Title of Invention	"ELECTRONIC CONTROL APPARATUS"
Abstract	To obtain an electronic control apparatus which may be reduced in weight as well as in size, and has improved operability in assembly and improved reliability in attachment of a cover to a housing. In the electronic control apparatus, attachment units for attaching a cover (7) to a housing (3) include engagement protrusions (7a) integrally formed with the cover (7) made of an insulating resin and engagement holes (3c) formed of an insulating resin integrally with an inner surface of a side wall (3b) of the housing (3). The engagement protrusions (7a) are inserted into the engagement holes (3c) to attach the cover (7) to the housing (3).

Title of Invention

"ELECTRONIC CONTROL APPARATUS"

Abstract

To obtain an electronic control apparatus which may be reduced in weight as well as in size, and has improved operability in assembly and improved reliability in attachment of a cover to a housing. In the electronic control apparatus, attachment units for attaching a cover (7) to a housing (3) include engagement protrusions (7a) integrally formed with the cover (7) made of an insulating resin and engagement holes (3c) formed of an insulating resin integrally with an inner surface of a side wall (3b) of the housing (3). The engagement protrusions (7a) are inserted into the engagement holes (3c) to attach the cover (7) to the housing (3).

Full Text	ELECTRONIC CONTROL APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic control apparatus used for, for example, an electric power steering device for assisting in biasing a steering device of a vehicle with a rotary force of an electric motor. 2. Description of the Related Art Conventionally, there is known an electronic control apparatus, which includes a field effect transistor (FET) as a semiconductor switching element, which being a power device to be mounted on a metal substrate, and has a structure in which a connection member fixed onto the metal substrate, for electrically connecting the metal substrate and components provided outside the metal substrate to each other. For example, an electronic control apparatus described in JP 3644835 B (FIG. 2) (hereinafter, referred to as Patent Document 1) includes a power substrate, a housing, a control substrate, a connection member, a heat sink, and a case. On the power substrate, a bridge circuit including the semiconductor switching elements for switching a current of an electric motor is mounted. The housing includes a conductive plate or the like which is insert molding into an insulating resin and a high-current component mounted thereon. A low-current component such as a microcomputer is mounted on the control substrate. The connection member electrically connects the power substrate, and the housing and the control substrate to each other. The heat sink is brought into close contact with the power substrate. The case is formed by press molding of a metal plate to cover the power substrate, the housing, and the control substrate, and is attached to the heat sink. In addition, an electronic control apparatus described in JP 2003-309384 A (FIG. 3) (hereinafter, referred to as Patent Document 2) includes a cover, a printed circuit board, a case, and a housing. An engagement portion corresponding to a snap hook formed on a periphery of the cover is engaged with a portion to be engaged formed for the case, to thereby attach the cover to the case in a removable manner. In the electronic control apparatus described in Patent Document 1 described above, top and side surfaces of an apparatus main body including the power substrate, the housing, and the control substrate therein are covered with the case formed by press molding of the metal plate. Therefore, the electronic control apparatus has a problem in that a volume as well as a mass is increased. Moreover, a caulking tab formed on an end surface of the case is caulked to secure the case to the heat sink. Therefore, the electronic control apparatus has another problem in that a securing operation is complicated. On the other hand, in the electronic control apparatus described in Patent Document 2 described above, the snap hook formed on the periphery of the cover is engaged with the portion to be engaged formed in an outer peripheral portion of the case, and a position at which the snap hook is engaged with the portion to be engaged is externally exposed. Therefore, this conventional electronic control apparatus has a problem in that there is a fear that the cover is unintentionally detached from the case by an external shock applied on the position where the engaged portion between the snap hook and the portion to be engaged is exposed. SUMMARY OF THE INVENTION The present invention is devised to solve the problems described above, and has an object of providing an electronic control apparatus which may be reduced in weight cis well as in size and has improved operability in assembly and improved reliability in attachment of a cover to a housing. An electronic control apparatus according to the present invention includes: a housing made of an insulating resin, the housing having opening portions at both ends thereof; a heat sink attached to one of the ends of the housing; a power device mounted onto the heat sink; a circuit board provided so as to be opposed to the heat sink, the circuit board carrying an electronic circuit including a control circuit for controlling the power device; a cover, which is made of an insulating resin to be attached to another end of the housing, for housing the power device and the circuit board in cooperation with 2 the heat sink; and attachment means for attaching the cover to the housing, wherein the attachment means includes: engagement protrusions formed on the cover; and engagement holes provided to the housing, and the engagement protrusions are inserted into the engagement holes, respectively, to be engaged thereto so that the cover is attached to the housing. According to the electronic control apparatus of the present invention, because the cover and the housing are made of the insulating resin, the weight is reduced. Moreover, the engagement protrusions of the cover are inserted into the engagement holes of the housing to be engaged thereto, thereby fixing the cover to the housing. Therefore, the effects such as a reduction in size, improved operability in assembly, and improved reliability in attachment of the cover to the housing may be obtained. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: Fig. 1 is an exploded perspective view illustrating an electronic control apparatus according to a first embodiment of the present invention; FIG. 2 is a side sectional view of the electronic control apparatus illustrated in FIG. 1; FIG. 3 is a sectional perspective view of the electronic control apparatus, which is cut along a direction perpendicular to the side cross-section of FIG 2; FIG. 4 is a sectional perspective view of the electronic control apparatus illustrated in FIG. 1, which is cut along the same direction as that of the side cross-section of the electronic control apparatus of FIG. 2 and is viewed from the direction opposite to that of FIG. 2; FIG. 5 is a sectional perspective view of the electronic control apparatus illustrated in FIG. 1, which is cut along a direction parallel to the cross section of the electronic control apparatus of FIG. 3; FIG. 6 is a perspective view illustrating a cover illustrated in FIG 1; and FIG 7 is a sectional view of a principal part, illustrating the electronic control apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electronic control apparatus according to each embodiment of the present invention is described based on the accompanying drawings. In each of the drawings, the same or equivalent components or parts are denoted by the same reference numerals for description. First Embodiment FIG. 1 is an exploded perspective vievi/ illustrating an electronic control apparatus 1 according to a first embodiment of the present invention. FIG. 2 is a side sectional view of the electronic control apparatus 1 illustrated in FIG. 1. FIG. 3 is a sectional perspective view of the electronic control apparatus 1 cut along a direction perpendicular to the side cross-section of the electronic control apparatus 1 of FIG. 2. FIG. 4 is a sectional perspective view illustrating the electronic control apparatus 1, which is cut along the same direction as that of the side cross section of the electronic control apparatus 1 of FIG. 2 and is viewed from a direction opposite to that of FIG. 2. FIG. 5 is a sectional perspective view illustrating the electronic control apparatus 1 illustrated in FIG. 1 which is cut along a direction parallel to the cross section of the electronic control apparatus 1 of FIG. 3. FIG. 6 is a perspective view illustrating a cover 7 illustrated in FIG. 1. The electronic control apparatus 1 includes a housing 3, a heat sink 5, semiconductor switching elements 2, a circuit board 4, and the cover 7. The housing 3 is made of an insulating resin and has a box-like shape with opening portions formed on both sidejs. The heat sink 5 is made of aluminum, and is fixed onto one of the opening portions of the housing 3. Each of the semiconductor switching elements 2 corresponds to a power dcjvice mounted on the heat sink 5. The circuit board 4 is provided parallel to the heat sink 5 to be opposed thereto. An electronic circuit including a control circuit for controlling the semiconductor switching elements 2 is formed on the circuit board 4. The cover 7, which is made of an insulating resin is attached onto the other opening portion of the housing 3, and houses the semiconductor switching elements 2 and the circuit board 4 therein in cooperation with the heat sink 5. The cover 7 has engagement protrusions 7a, each including a hook portion 7b formed at an end. A pair of the engagement protrusions 7a are formed vertically on an outer peripheral edge of a surface of the cover 7, which is opposed to the circuit board 4, while their hook portions 7b are oriented in the opposite directions. Each pair of the engagement protrusions 7a is formed on each side of the cover 7. The pairs of protrusions 7a provided on the opposed sides are arranged in point symmeti7 with respect to a center of the surface of the cover 7, which is opposed to the circuit board 4. On an inner wall surface of each of side walls 3b of the housing 3 surrounding the components, engagement holes 3c penetrating through the housing 3 in a direction, in which the engagement protrusions 7a of the cover 7 are inserted, are integrally formed of the insulating resin. On opposed inner wall surfaces of the engagement holes 3c, convex portions 3d and tapered portions 3e are respectively formed. The hook portions 7b of the engagement protrusions 7a are locked to the convex portions 3d. The tapered portions 3e gradually elastically deform the pair of hook portions 7b in a direction parallel to the side walls 3b of the housing 3 to allow the hook portions 7b to get closer to each other as the engagement protrusions 7a are inserted. Therefore, when the pair of engagement protrusions 7a are inserted into the engagement holes 3c, the hook portions 7b of the engagement protrusions 7a are gradually deformed inward by the tapered portions 3e. Then, each of the hook portions 7b passes over the convex portion 3d to be engaged thereto. As a result, the cover 7 is attached to the housing 3. A fitting portions 7c are formed at proximal end portions of the pair of engagement protrusions 7a. The fitting portions 7c are fitted into an insert port 3f of the engagement holes 3c to position the cover 7 and the housing 3. F-urther, the heat sink 5 is provided on the side of the engagement holes 3c, which is opposite to the insert port 3f. The heat sink 5 closes the engagement holes 3c. Note that the engagement protrusions 7a formed on the cover 7 and the engagement holes 3c provided to the housing 3 constitute attachment means for attaching the cover 7 to the housing 3. Further, the electronic control apparatus 1 includes, as illustrated in FIG 2. conductive plates 6a and 6b and a plate spring 21. Each of the conductive plates 6a has a base portion integrally formed with the housing 3 by insert molding of an insulating resin 3a, and electrically connects the circuit board 4 and each of the semiconductor switching elements 2 to each other. The conductive plate 6b has a base portion integrally formed with the housing 3 by the insert molding using the insulating resin 3a, and electrically connects the circuit board 4 and power connector terminals 8a to each other. The plate spring 21, which is made of a metal, is an elastic member for pressing an insulating resin package of each of the semiconductor switching elements 2 to bring a heat spreader hs into close contact with the heat sink 5. The plate spring 21 is secured to the hecit sink 5 by a screw 20 through an intermediation of the housing 3. A vehicle connector 8 to be electrically connected to a wiring of a vehicle is provided on one side surface of the housing 3, whereas a motor connector 9 to be electrically connected to an electric motor (not shown) and a sensor connector 10 to be electrically connected to a torque sensor (not shown) are provided on the other side surface. The vehicle connector 8 includes: the power connector terminals 8a to be electrically connected to a battery (not shown) of the vehicle; and signal connector terminals 8b to/from which a signal is input/output through the wiring of the vehicle. Further, the motor connector 9 includes motor connector terminals 9a, whereas the sensor connector 10 includes sensor connector terminals 10a. The conductive plates 6a electrically connect the circuit board 4 and the semiconductor switching element 2 to each other. And the conductive plate 6b is electrically connected to the power connector terminal 8a. Together with the conductive plates 6a and the conductive plates 6b, the power connector terminals 8a, the signal connector terminals 8b, the motor connector terminals 9a, the sensor connector terminals 10a and the like are formed by the insert molding in the housing 3. At the same time, the vehicle connector 8, the motor connector 9, and the sensor connector 10 are formed integrally with the housing 3. Further, on both side wall surfaces of the housing 3 on the side of the opening portion opposite to the opening to which the heat sink 5 is attached, attachment leg portions 3L for attaching the electronic control apparatus 1 to the vehicle corresponding to an attachment target body are respectively formed. As each of the semiconductor switching elements 2, a high-side MOSFET and a low-side MOSFET are integrated to form a half-bridge. As the semiconductor switching element 2, the half-bridge is housed within a single package. In addition, a pair of the semiconductor switching elements 2 constitute a bridge circuit for switching a current of the electric motor (not shown). The semiconductor switching element 2 of the half-bridge includes five terminals, that is, a power supply terminal, a gate terminal of the high-side MOSFET, a bridge output terminal, a gate terminal of the low-side MOSFET, and a ground terminal. The power supply terminal, the bridge output terminal, and the ground terminal are high-current terminals through which a high current flows, whereas the gate terminal of the high-side MOSFET and the gate terminal of the low-side MOSFET are low-current terminals for signals. A microcomputer 13 is mounted by soldering on a wiring pattern on a surface of the circuit board 4, whereas capacitors 14 for absorbing a ripple of a motor current are mounted by soldering on a wiring pattern of a bottom surface. Although not shown in FIG. 1, a coil for preventing an electromagnetic noise generated at the time of a switching operation of the semiconductor switching elements 2 from leaking to the exterior, a motor current detecting circuit including a shunt resist or, a peripheral circuit element and the like are also mounted by soldering onto the wiring pattern formed on the circuit board 4. Further, a plurality of through holes 4a, each having an inner surface plated with copper, are formed through the circuit board 4. The through holes 4a are electrically connected to the wiring pattern of the circuit board 4. The heat sink 5 includes a heat sink main body 5a and an anodized aluminum film 5b corresponding to an insulating coating formed on a surface of the heat sink main body 5a. The heat sink 5 is formed in the following manner. An elongated extruded profile is formed by extruding aluminum or an aluminum alloy from a die. A heat sink material is fabricated by forming the anodized aluminum film 5b in advance on an entire surface of the extruded profile. The heat sink material is cut to a desired length by a cutter, thereby forming the heat sink 5. Outer peripheral end surfaces of the heat sink 5 on both sides in one direction, which are formed by cutting with the cutter, are cut surfaces 5c on which the heat sink main body 5a is externally exposed. The anodized aluminum film 5b is formed on the surfaces other than the cut surfaces 5c. The anodized aluminum film 5b is formed even on the surface on which the semiconductor switching elements 2 are mounted and the bottom surface thereof. The cut surfaces 5c are opposed to the inner wall surfaces of the side walls 3b of the housing 3. Although the heat sink 5 is fabricated by the extruded profile in this case, the heat sink 5 may also be fabricated by cutting of the heat sink material which is subjected to hot or cold forging. Alternatively, the heat sink 5 may also be fabricated by cutting of a plate material which is subjected to hot or cold rolling. Further alternatively, the four outer peripheral end surfaces of the heat sink main body 5a or a part thereof may be exposed to be opposed to the inner wall surfaces of the side walls 3b. The plate spring 21 presses the surface of the insulating resin package of each of the semiconductor switching elements 2 to bring the heat spreader hs corresponding to a heat releasing portion of the ssemiconductor switching element 2 into close contact with the surface of the heat sink 5 on which the anodized aluminum film 5b is formed. Although the heat spreader hs of the semiconductor switching element 2 is electrically connected to the bridge output terminal, the heat spreader hs is electrically insulated from the heat sink 5 by the anodized aluminum film 5b. The heat sink 5 has small concavity and convexity on its surface. Therefore, even when the heat spreader hs of the semiconductor switching element 2 is brought into close contact with the heat sink 5 by a function of the plate spring 21, a slight gap is generated therebetween. By the effects of the slight gap, a thermal resistance of a heat transfer path for releasing heat generated in the semiconductor switching elements 2 to the heat sink 5 is increased. In order to eliminate the gap, a highly thermal conductive adhesive resin (not shown) is applied between the heat spreader hs and the anodized aluminum film 5b of the heat sink 5 to bring the heat spreader hs and the heat sink 5 into close contact witli each other to fix them. As another means of eliminating the gap between the heat spreader hs of the semiconductor switching element 2 and the heat sink 5, a highly thermal conductive grease may be provided therebetween. The plate spring 21 is formed by, for example, a copper alloy plate having spring properties, such as a phosphor bronze plate for spring, which is subjected to press working using a press working machine, The plate spring 21 includes: pressure portions 21a for pressing the insulating resin packages of the pair of adjacent semiconductor switching elements 2; and engagement portions 21b respectively extending perpendicular to the pressure portions 21a. The engagement portions 21b are pressed-fitted into between a pair of holding portions 3b formed of the insulating resin integrally with the housing 3 to be engaged thereto. Further, for the plate spring 21, a slit 21c is formed in an extended portion extending from both sides of one of the engagement portions 21 b. A holding member H having functions of holding the circuit board 4 and of connecting the ground terminal of the circuit board 4 to the heat sink 5 is press-fitted into the slit 21 c. A press-fit terminal portion Hp formed at a top of the holding portion H is press-fitted into the through hole 4a of the circuit board 4 to electrically connect the wiring pattern of the circuit board 4 and the heat sink 5 to each other through the press-fit terminal portion Hp, the holding member H, the plate spring 21, and the screw 20. Although the plate spring 21 is made of the copper alloy plate having the spring properties such as the phosphor bronze plate for spring in this case, the plate spring 21 may be made of other materials such as a stainless steel plate for spring. A proximal end portion of each of the conductive plates 6a, which is exposed from the insulating resin 3a of the housing 3, is connected to the tops of the power supply terminal, the bridge output terminal, the ground terminal, and the gate terminal of each of the semiconductor switching elements 2 by laser welding. A press-fit terminal portion 6p is formed on each of the conductive plates 6a. The press-fit terminal portions 6p are press-fitted into the through holes 4a of the circuit board 4. As a result, each of the terminals of the semiconductor switching elements 2 and the wiring pattern of the circuit board 4 are electrically connected to each other. The conductive plates 6a are arranged to overlap each other to extend In a direction in which each of the terminals of the semiconductor switching elements 2 extends. Further, the terminals of each of the semiconductor switching elements 2 are arranged on a surface of each of the conductive plates 6a, which is opposed to the heat sink 5. Each of the terminals of the semiconductor switching elements 2 is formed to have a width of 0.8 mm and a thickness of 0.5 mm at an interval of 1.7 mm between the terminals. A high current flows through the conductive plate 6a which is connected to the power supply terminal, the bridge output terminal, and the ground terminal corresponding to the high-current terminals of the semiconductor switching element 2. Because each of the conductive plates 8a is made of a rolled copper alloy, a thickness of the conductive plate 6a to be connected to the high-current terminals is required to be increased when a rolled surface (surface) of the conductive plate 6a and the high-current terminals of the semiconductor switching element 2 are welded to each other. However, in terms of formation of the press-fit terminal portions and the press working, it is difficult to increase the thickness of each of the conductive plates 6a. Therefore, in the first embodiment, the thickness of each of the conductive plates 6a is set to the same value of 0.8 mm as that of the width of each of the terminals of the semiconductor switching element 2. Instead, a width of each of the conductive plates 6a is set larger than the thickness to allow an end surface perpendicular to the rolled surface to be welded to the terminals of the semiconductor switching element 2. Specifically, the conductive plate 6a is formed to have a larger size in a bonding direction with the terminals of the semiconductor switching element 2 than that in a direction perpendicular to the bonding direction (size in a width direction). Because a low current flows through the conductive plate 6a used for signals, it is not necessary to take a reduction in electric resistance into consideration. However, this conductive plate 6a is made of the same material as that of the conductive plate 6a through which the high current flows. The conductive plates 6a are made of a highly conductive copper alloy with high strength or phosphor bronze in view of an electrical conductivity for allowing the high current to flow and a mechanical strength for forming the press-fit temninal portions 6p. For the conductive plate 6a formed by using phosphor bronze, the motor current of, for example, 30A or lower is used. Each of the terminals of the semiconductor switching element 2 is bent in the same crank-like shape with a standing portion and a lying portion in the middle, and extends in the same direction. A first bent portion 2a corresponding to a bent portion of each of the terminals of the semiconductor switching element 2 on the distal end side is formed at an acute angle. A second bent portion 2b corresponding to a bent portion on the main body side of the semiconductor switching element 2 is formed to be upright at a right angle. As illustrated in FIG. 2, on an upper surfeice of a middle portion of the heat sink 5, which has a larger thickness as compared with that of both sides, the heat spreader hs corresponding to the heat releasing portion of the semiconductor switching element 2 is mounted. On the other hand, above a small-thickness portion of the heat sink 5 on one side, bent welded portions of the terminals of the semiconductor switching element 2 are located. The welded portions of the terminals of the semiconductor switching element 2, which are to be welded to the conductive plate 6a, are separated away from the heat spreader hs. In addition, the heat sink 5 is not attached yet at the time of welding. Therefore, the main body of each of the semiconductor switching elements 2 does not become an obstacle to the laser welding. A laser beam LB is radiated from a direction of the attachment of the heat sink 5 to the surfaces of the terminals of the semiconductor switching element 2. As a result, the terminals of the semiconductor switching element 2 are laser-welded to the conductive plate 6a. Moreover, each of the terminals of the semiconductor switching element 2 is formed to have the first bent portion 2a formed at the acute angle, and is pressed against the conductive plate 6a by bending elasticity. In this state, the vicinity of the distal end portion of each of the terminals of the semiconductor switching element 2 is irradiated with the laser beam LB to be welded to the conductive plate 6a. At this time, a gap between each of the terminals of the semiconductor switching element 2 and the conductive plate 6a increases from the distal end portion toward the first bent portion 2a. As a result, the vicinity of the distal end portion corresponding to the vicinity of the welded portion is pressed against the conductive plate 6a by the bending elasticity As illustrated in FIG. 2, a positioning portion 3h for positioning each of the semiconductor switching elements 2 and the housing 3 is provided to the housing 3. The positioning portion 3h has a tapered portion at its distal end. The positioning portion 3h is guided by the tapered portion to be inserted into a hole 2c formed in the heat spreader hs of the semiconductor switching element 2, thereby performing the positioning. The positioning portion 3h also performs the positioning for the direction in which each of the terminals of the semiconductor switching element 2 extends. Moreover, as illustrated in FIG. 1, a pair of positioning portions 3k for positioning each of the terminals of the semiconductor switching elements 2 and the conductive plates 6a are formed to the housing 3 in a similar manner to a positioning portions 3h, and the positioning portions 3k are opposed mutually. The positioning portions 3k perform positioning for a direction perpendicular to the extending direction of each of the terminals of the semiconductor switching element 2. The positioning portions 3k are formed on both outer sides of the terminals of each of the semiconductor switching elements 2. Each of the positioning portions 3k has a tapered portion at its distal end. The outer side of each of the terminals of the semiconductor switching element 2 is guided by the tapered portion to position each of the terminals of the semiconductor switching element 2 and the conductive plates 6a. Each of the terminals of the semiconductor switching element 2, which is positioned by the positioning portions 3h and 3k, is welded to the conductive plate 6a. Each of the terminals of the semiconductor switching element 2 is provided to be separated away from an axis AX of FIG. 2, which corresponds to a press-fitting direction of the press-fit terminal portions 6p, in a horizontal direction to be welded to the conductive plate 6a. The insulating resin 3a is interposed on an extension of the axis AX between the conductive plate 6a and the heat sink 5. As a result, a press-fit force for press-fitting the press-fit terminal portions 6p into the through holes 4a of the circuit board 4 is received by the heat sink 5 through the insulating resin 3a. Therefore, the welded portion for the laser welding is distant from the insulating resin 3a which inhibits the welding. In addition, because the insulating resin 3a is interposed between the conductive plate 6a and the heat sink 5 when the press-fit terminal portions 6p are press-fitted into the through holes 4a, a technique of the laser welding and a technique of the press-fitting to the through hole 4a may be both employed. The laser beam LB is radiated to the surface of each of the terminals of the semiconductor switching element 2, thereby connecting the terminals of the semiconductor switching element 2 to the conductive plates 6a. Therefore, it is necessary to prevent the degradation and melting damage of the insulating resin 3a due to heat generated by the laser welding. Moreover, it is also necessary to prevent the degradation and melting damage of the insulating resin 3a in the vicinity of the laser-welded portion and the degradation of the press-fit terminal portions 6p of the conductive plate 6a due to reflected light of the laser beam LB generated on the surfaces of the terminals of the semiconductor switching element 2 at the time of laser welding. Further, it is also necessary to prevent gases from adhering to the press-fit terminal portions 6p of the conductive plate 6a at the time of laser welding. A gas is generated from a melted portion of each of the terminals of the semiconductor switching element 2. Moreover, a gas is generated from the insulating resin 3a in the vicinity of the laser-welded portion due to heat of the laser welding, or the reflected light. In the first embodiment, the proximal end portion of each of the conductive plate 6a, which is welded to the terminals of the semiconductor switching element 2, is formed in a comb-like pattern to be exposed from the insulating resin 3a of the housing 3. As a result, the insulating resin 3a may be less affected by the heat and the reflected light generated at the time of laser welding. Moreover, the press-fit terminal portions 6p of the conductive plate 6a are provided on the cover 7 side, whereas the laser-welded portion is arranged on the heat sink 5 side. In this manner, a distance beKveen the press-fit terminal portions 6p and the laser-welded portion is increased. As a result, the press-fit terminal portion 6p is less affected by the heat, reflected I ght, and gas generated at the time of laser welding. Moreover, the insulating resin 3a is interposed between the press-fit terminal portions 6p and the laser-welded portion. As a result, the reflected light generated at the time of laser welding can hardly reach the press-fit terminal portions 6p. Two of the press-fit terminal portions 6p are formed on the conductive plate 6a through which the high current flows, whereas the single press-fit terminal portion 6p is formed on the conductive plate 6a for signals, through which the low current flows. Specifically, as illustrated in FIG. 1, seven press-fit terminal portions 6p are provided for each of the semiconductor switching elements 2. As described above, the interval between the terminals of the semiconductor switching element 2 is 1.7 mm. Moreover, a diameter of the through hole 4a of the circuit board 4, into which the press-fit terminal portion 6p is press-fitted, is formed to be 1.45 mm. In the first embodiment, the adjacent press-fit terminal portions 6p of the conductive plate 6a are arranged in a zigzag pattern. As a result, a distance between the adjacent press-fit terminal portions 6p is made larger than the interval between the terminals of the semiconductor switching element 2. As illustrated in FIG. 4, end portions 15a of terminals 15 are bent at a right angle to respectively overlap end portions 8c of the signal connector terminals 8b and end portions 10b of the sensor connector terminals 10a. Overlapping surfaces of the end portions 15a and the end portions 8c and 10b are formed in parallel to the heat sink 5 to be welded to each other. In this case, the end portions 8c of the signal connector terminals 8b and the end portions 10b of the sensor connector terminals 10a are provided on the side of the heat sink 5. Further, as in the case of the welding between the terminals of the semiconductor switching element 2 and the conductive plates 6a, the laser beam is radiated from the direction of attaching the heat sink 5 to the surfaces of the end portions 8c of the signal connector terminals 8b and the end portions 10b of the sensor connector terminals 10a. As a result, the signal connector terminals 8b and the sensor connector terminals 10a are welded to the terminals 15. A press-fit terminal portion 15p is formed at an end of each of the terminals 15 on the side opposite to the welded portion. The press-fit terminal portions 15p are press-fitted into the through holes 4a of the circuit board 4. As a result, the signal connector terminals 8b and the sensor connector terminals 10a connected to the terminals 15 are electrically connected to the wiring pattern of the circuit board 4. As in the case of the conductive plates 6a, the press-fit terminal portions 15p of the terminals 15 are provided on the cover 7 side, whereas the laser-welded portions are provided on the heat sink 5 side. In this manner, a distance between the press-fit terminal portions 15p and the laser-welded portions is increased. As a result, the press-fit terminal portions 15p are less affected by the heat, reflected light, and gas generated at the time of laser welding. The motor connector terminals 9a are connected to an end of the conductive plate 6a to which the bridge output terminal of the semiconductor switching element 2 is connected, the end being on the side opposite to the proximal end portion. The motor connector terminals 9a are provided on a surface of an end portion of the conductive plate 6a, which is opposed to the heat sink 5. The laser beam LB is radiated from the direction of the attachment of the heat sink 5 to the surfaces of the motor connector terminals 9a. As a result, as in the case where the conductive plate 6a and the bridge output terminal of the semiconductor switching element 2 are welded to each other, the motor connector terminals 9a are welded to the conductive plate 6a. The motor current output form the bridge output terminal of the semiconductor switching element 2 passes not through the circuit board 4 but directly through the motor connector terminals 9a to flow into the electric motor (not shown). The press-fit terminal portions 6p extending toward the circuit board 4 are formed in a middle portion of the conductive plate 6a which is connected to the bridge output terminal of the semiconductor switching element 2. In this manner, a signal for monitoring a voltage of the motor connector terminals 9a is output to the circuit board 4. As illustrated in FIG. 2, the power connector terminals 8a are connected to the conductive plate 6b. The power connector terminals 8a are provided on a surface of an end of the conductive plate 6b, which is opposed to the heat sink 5. Then, the laser beam LB is radiated from the direction of the attachment of the heat sink 5 to the surfaces of the power connector terminals 8a to weld the power connector terminals 8a to the conductive plate 6b as in the case of the connection of the motor connector terminals 9a to the conductive plate 6a. The press-fit terminal portions 6p extending toward the circuit board 4 are formed on the conductive plate 6b. The press-fit terminal portions 6p are press-fitted into the through holes 4a of the circuit board 4. As a result, the conductive plate 6b and the wiring pattern of the circuit board 4 are electrically connected to each other. Then, a current from the battery of the vehicle is supplied to the circuit board 4 through the power connector terminals 8a, the conductive plate 6b, and the press-fit terminal portions 6p. The press-fit terminal portions 6p, 15p, and Hp are respectively press-fitted into the through holes 4a to mechanically hold the circuit board 4. The conductive plates 6a and 6b, the terminals 15, and the holding member H are formed by insert molding of the insulating resin 3a of the housing 3. Because the insulating resin 3a is interposed between the conductive plates 6a and 6b, the terminals 15, and the holding member H, and the heat sink 5, the press-fit force may be received by the heat sink 5 when the press-fit terminal portions 6p, 15p, and Hp are press-fitted into the through holes 4a. Due to fabrication precision, however, a slight gap is generated between the insulating resin 3a and the heat sink 5. In the press-fitting, a relative height accuracy between the press-fit terminal portions 6p, 15p, and Hp and the circuit board 4 is important. However, the generation of the slight gap between the insulating resin 3a and the heat sink 5 degrades the relative height ciccuracy. Therefore, for example, as illustrated in F'IG. 2, an adhesive (not shown) is applied in a gap between the insulating resin 3a below the conductive plate 6a and the heat sink 5 and a gap between the insulating resin 3a below the conductive plate 6b and the heat sink 5 to eliminate the effects of the gaps. As illustrated in FIG. 5, inside a peripheral edge of each of the fitting portions 7c of the cover 7, a holding portion 7d is formed. On the inner side of each of the engagement holes 3c of the housing 3, a holding portion 3m is formed. The circuit board 4 is sandwiched between the holding portions 7d and 3m to be held therebetween. Alternatively, the holding portions 7d and 3m may be formed at the positions where the press-fit terminal portions 6p, 15p, and Hp are not located to mechanically hold the circuit board 4 by the press-fit terminal portions 6p, 15p, and Hp and the holding portions 7d and 3m. Next, a procedure of assembling the electronic control apparatus 1 configured as described above is described. First, a cream solder is applied onto the circuit board 4. Then, the components such as the microcomputer 13 and the peripheral circuit elements thereof are arranged thereon. Thereafter, the cream solder is melted by using a reflow device to solder each of the components onto the circuit board 4. Next, the terminals of each of the semiconductor switching elements 2 are bent in a crank-like shape. Then, the semiconductor switching elements 2 are arranged on the housing 3 with the opening portion on the side where the heat sink 5 is attached being oriented upward. At this time, the main body and each of the terminals of each of the semiconductor switching elements 2 are guided and positioned by the positioning portions 3h and 3k to superimpose each of the terminals on the conductive plate 6a. Thereafter, the laser beam LB is radiated from the terminal side of the semiconductor switching element 2 to laser-weld each of the terminals and the conductive plates 6a to each other. Similarly, the laser beam LB is radiated from the side of the power connector terminals 8a and the motor connector terminals 9a to laser-weld the power connector terminals 8a and the conductive plate 6b to each other and the motor connector terminals 9a and the conductive plate 6a to each other. The laser beam is also radiated to the surfaces of the end portions 8c of the signal connector terminals 8b and the end portions 10b of the sensor connector terminals 10a to laser-weld the signal connector terminals 8b and the sensor connector terminals 10a to the terminals 15. Next, on a portion of the heat sink 5, on which each of the semiconductor switching elements 2 is mounted, a highly thermal conductive adhesive resin (not shown) is printed at a small thickness. Further, an adhesive (not shown) is applied to the portions of the heat sink 5, which are opposed to the insulating resin 3a in the vicinity of the regions where the conductive plates 6a and 6b, the terminals 15, and the holding member H are formed by insert-molding. Thereafter, the housing 3, for which the laser welding is completed, is inverted to cause the opening portion, to which the heat sink 5 is attached, to be oriented downward. Then, the housing 3 is placed on the heat sink 5. Further, the engagement portions 21b are press-fitted to an inner side of a holding portion 3g to lock the plate spring 21 to the housing 3. Simultaneously, the slit 21c is press-fitted into the holding member H. Next, the plate spring 21 as well as the housing 3 is secured to the heat sink 5 with the screws 20. The semiconductor switching elements 2 are pressed against the heat sink 5 by the pressing portions 21a of the plate spring 21. Thereafter, the adhesive resin and the adhesive are cured in a furnace kept at high temperature. Subsequently, the distal ends of the press-fit terminal portions 6p, 15p, and Hp are inserted into the through holes 4a of the circuit board 4 to attach the circuit board 4 onto an upper part of the housing 3. Thereafter, the press-fit terminal portions 6p, 15p, and Hp are press-fitted into the through holes 4a by using the pressing machine. Next, the engagement protrusions 7a of the cover 7 are inserted into the engagement holes 3c of the housing 3 to position the cover 7 on the opening portion of the housing 3. Thereafter, the cover 7 is pressed to be engaged to the housing 3, thereby completing the assembly of the electronic control apparatus 1. As described above, according to the electronic control apparatus 1 of the first embodiment, the attachment means for attaching the cover 7 to the housing 3 includes the engagement protrusions 7a formed on the cover 7 and the engagement holes 3c provided to the housing 3. The engagement protrusions 7a are inserted into the engagement holes 3c to fix the cover 7 to the housing 3. Therefore, the operability in assembly of the electronic control apparatus 1 is improved. Further, because the cover 7 and the engagement protrusions 7a are integrally formed of the insulating resin, the electronic control apparatus 1 is reduced in weight. Moreover, the hook portion 7b is formed at the end of each of the engagement protrusions 7a. In addition, on the inner wall surface of the engagement holes 3c, the convex portion 3d for engaging the hook portion 7b of the engagement protrusion 7a and the tapered portion 3e for elastically deforming the hook portion 7b as the engagement protrusion 7a is inserted are formed. Therefore, the insertion of the engagement protrusion 7a is facilitated to improve the operability in assembly of the electronic control apparatus 1. Moreover, because the cover 7 is surely locked to the housing 3, dust resistance of the electronic control apparatus 1 is improved. The two engagement protrusions 7a form a pair to protrude in a vertical direction. The hook portions 7b of the pair of the engagement protrusions 7a are formed to be oriented in the opposite directions. In addition, on the opposed inner wall surfaces of the engagement holes 3c, the convex portion 3d and the tapered portion 3e are formed. Thus, the insertion of the engagement protrusion 7a is facilitated to improve the operability in assembly of the electronic control apparatus 1. F-urther, because the cover 7 is surely locked to the housing 3, the dust resistance of the electronic control apparatus 1 is improved. F-urther, because the engagement holes 3c are integrally formed of the insulating resin on the inner wall surfaces of the side walls 3b of the housing 3, the electronic control apparatus 1 may be reduced in size. Moreover, the attachment means for attaching the cover 7 to the housing 3 are invisible from the outside. In addition, it is hard to easily remove the cover 7 from the housing 3. Therefore, illegal modification of an internal structure of the electronic control apparatus 1 may be prevented. Moreover, when the engagement protrusions 7a are inserted into the engagement holes 3c, the hook portions 7b are configured to be elastically deformed in a direction parallel to the side walls 3b of the housing 3 by the tapered portions 3e. Therefore, a bulge of the attachment means from the side walls 3b is reduced to reduce the electronic control apparatus 1 in size. Further, the fitting portions 7c are formed at the proximal end portions of the engagement protrusions 7a. The fitting portions 7c are fitted into the insert ports 3f of the engagement holes 3c to position the cover 7 and the housing 3. Therefore, the engagement protrusions 7a are prevented from being damaged by the application of an excessive stress due to an external force applied on the cover 7. As a result, the dust resistance of the electronic control apparatus 1 is improved. Further, because the hook portions 7b of the engagement protrusions 7a are formed to be oriented in the opposite directions, the engagement holes 3c may be reduced in size. As a result, the electronic control apparatus 1 may be reduced in size. Further, because the pairs of engagement protrusions 7a are formed on each side of the cover 7, the cover 7 may be surely locked to the housing 3. As a result, the dust resistance of the electronic control apparatus 1 is improved. In addition, an abnormal noise generated at the boundary surface between the cover 7 and the housing 3 due to a vibration is suppressed. Further, the engagement protrusions 7a provided on the opposed sides are arranged in point symmetry with respect to the center of the plane parallel to the circuit board 4. Therefore, the cover 7 may be attached at a position rotated by 180 degrees. As a result, the operability in assembly of the electronic control apparatus 1 is improved. Further, the heat sink 5 is arranged on the side opposite to the insert ports 3f to be opposed to the engagement holes 3c to allow the heat sink 5 to close the engagement holes 3c. Therefore, a foreign substance may be prevented from entering the electronic control apparatus 1, thereby improving the dust resistance of the electronic control apparatus 1. Moreover, the illegal modification of the electronic control apparatus 1 may be prevented. Moreover, because the circuit board 4 is sandwiched between the holding portions 7d formed on the cover 7 and the holding portions 3m formed on the housing 3 to be held therebetween, the vibration of the circuit board 4 may be suppressed to improve vibration resistance of the electronic control apparatus 1. Further, the holding portions 7d are formed inside the peripheral edges of the fitting portions 7c of the cover 7, whereas the holding portions 3m are formed on the inner sides of the engagement holes 3c of the housing 3. Therefore, the circuit board 4 is firmly held to improve the vibration resistance of the electronic control apparatus 1. Second Embodiment FIG. 7 is a sectional view illustrating a principal part of the electronic control apparatus 1 according to a second embodiment of the present invention. FIG. 7 is a view illustrating the electronic control apparatus 1 being assembled. In FIG. 7, the heat sink 5 is situated above the cover 7. In the second embodiment, a configuration is the same as that of the electronic control apparatus 1 of the first embodimient except for the configurations of the housing 3 and the cover 7. Specifically, in the second embodiment, a groove 7e corresponding to a first groove portion is formed in an outer peripheral edge portion of the cover 7 along the entire periphery. The groove 7e is open toward the housing 3 side. A protrusion 3n is formed on an opening end portion of the housing 3 on the cover 7 side along the entire periphery. A space formed by the insention of the protrusion 3n into the groove 7e is filled with a silicon adhesive 31 corresponding to the adhesive resin. The engagement protrusion 7a of the cover 7 is formed inside the groove 7e. The engagement protrusion 7a is inserted into the engagement hole 3c of the housing 3 to fix the cover 7 to the housing 3. A groove 30 corresponding to a second groove portion is formed between an outer peripheral end surface of the heat sink 5 and an inner wall surface 3p of the opening portion of the housing 3. The groove 30 is filled with the same silicon adhesive 31 as that filling the groove 7e. Moreover, the groove 7e and the groove 30 are open in the same direction. Further, the grooves 7e and 30 are filled with the silicon adhesive 31 from the same direction. Although not shown, a respiratory hole for communicating the interior of the electronic control apparatus 1 and the exterior v^ith each other is provided to the housing 3. A water repellant filter which allows air to pass therethrough but not water to pass therethrough is attached onto the respiratory hole. The procedure of assembling the electronic control apparatus 1 according to the second embodiment is the sanie as that in the first embodiment until the step of press-fitting the press-fit terminal portions 6p, 15p, and Hp into the through holes 4a of the circuit board 4 by using the pressing machine. Next, the water repellant filter (not shown) is attached onto a respiratory hole (not shown) formed through the housing 3 by thermal welding. Thereafter, as illustrated in FIG. 7, the cover 7 is placed with the open side of the groove 7e being oriented upward. Then, the groove 7e is filled with the silicon adhesive 31. Next, the engagement protrusion 7a of the cover 7 is inserted into the engagement hole 3c of the housing 3 with the surface, to which the cover 7 is to be attached, being oriented downward. Thereafter, the housing 3 is pressed to fix the cover 7 to the housing 3. Thereafter, the groove 30 with the opening portion of the housing 3 being oriented upward is filled with the silicon adhesive 31. Next, while both the grooves 7e and 30 are oriented upward, the electronic control apparatus 1 is placed in the furnace at high temperature to cure the silicon adhesive 31. After the silicon adhesive 31 is cured, the electronic control apparatus 1 is taken out from the furnace to be cooled. In this manner, the assembly of the electronic control apparatus 1 is completed. The silicon adhesive 31 may be a cold setting adhesive. The respiratory hole may be provided through the cover 7. and the water repellent filter may be attached onto the respiratory hole. Moreover, the water repellent filter may be attached after the step of curing the silicon adhesive 31. According to the electronic control appareitus 1 of the second embodiment, the groove 7e is formed in the outer peripheral edge portion of the cover 7, whereas the groove 30 is formed between the outer peripheral end surface of the heat sink 5 and the inner wall surface 3p of the opening portion of the housing 3. In addition, the grooves 7e and 30 are filled with the silicon adhesive 31. As a result, the interior of the electronic control apparatus 1 is sealed from the exterior. Therefore, water or the like may be prevented from entering the interior of the electronic control apparatus 1 from t.ie sxterior, thereby improving water resistance of the electronic control apparatus 1. Moreover, the engagement protrusions 7a and the engagement holes 3c constituting the attachment means is provided inside the groove 7e. As a result, the attachment means is prevented from being damaged by the external force, thereby improving the water resistance of the electronic control apparatus 1. Because the grooves 7e and 30 are open upward in the same direction and are filled with the silicon adhesive 31 from the same direction, the silicon adhesive 31 does not outflow from the grooves 7e and 30 during the curing of the silicon adhesive 31. As a result, together with the improvement of operability in assembly of the electronic control apparatus 1, the water resistance is improved. Although each of the terminals of the semiconductor switching elements 2 and the conductive plates 6a are bonded to each other by the laser welding in the first and second embodiments described above, the bonding may be performed by other welding methods such as resistance welding and TIG welding. Alternatively, the bonding may be performed by a method other than welding, such as ultrasonic bonding. Moreover, in the above-mentioned embodiments, the half-bridge formed by integrating the high-side MOSFET and the low-side MOSFET is housed in one package to form the semiconductor switching element 2, and the two semiconductor switching elements 2 form a pair to constitute the bridge circuit for switching the current of the electric motor. However, the high-side MOSFET and the low-side MOSFET may be separately configured to allow four semiconductor switching elements 2 to constitute the bridge circuit. Alternatively, the bridge circuit may be constituted by six semiconductor switching elements 2 to control the driving of a three-phase brushless motor. Further, though the semiconductor switching element 2 is used as the power device, other power devices such as a diode and a thyristor may be used. Although the thickness of the conductive plate 6a is set to 0.8 mm in the above-mentioned embodiments, the thickness of the conductive plate 6a may be set to other values such as 1.0 mm and 1.2 mm in view of the current flowing through each of the conductive plates 6a, the interval between the terminals of the semiconductor switching element 2, and the like. The example in which the present invention is applied to the electric power steering device for the automobile has been described above. However, the present invention is also applicable to an electronic control apparatus dealing with the high current (for example, 25A or higher), which includes the power device, such as the electronic control apparatus for an anti-lock brake system (ABS) and the electronic control apparatus for air-conditioning, to obtain the same effects. WHAT IS CLAIMED IS: 1. An electronic control apparatus, comprising: a housing made of an insulating resin, the housing having opening portions at both ends thereof; a heat sink attached to one of the ends of the housing; a power device mounted onto the heat sink; a circuit board provided so as to be opposed to the heat sink, the circuit board carrying an electronic circuit including a control circuit for controlling the power device; a cover, which is made of an insulating resin to be attached to another end of the housing, for housing the power device and the circuit board in cooperation with the heat sink; and attachment means for attaching the cover to the housing, wherein the attachment means comprises: engagement protrusions formed on the cover; and engagement holes provided to the housing, and the engagement protrusions are inserted into the engagement holes, respectively, to be engaged thereto so that the cover is attached to the housing. 2. An electronic control apparatus according to Claim 1, wherein each of the engagennent protrusions has an end portion formed in a hook-like shape. 3. An electronic control apparatus according to Claim 2, wherein convex portions for engaging the hook-like shaped end portions, and tapered portions for gradually elastically deforming the hook-like shaped end portions while the engagement protrusions are being inserted toward the convex portion, are formed on inner wall surfaces of each of the engagement hole. 4. An electronic control apparatus according to any one of Claims 1 to 3, wherein the two engagement protrusions form a pair to be inserted into each of the engagement holes to be engaged thereto. 5. An electronic control apparatus according to any one of Claims 1 to 4. wherein the engagement holes are formed on inner sides of the housing. 6. An electronic control apparatus according to Claim 5, wherein the engagement holes are formed on inner wall surfaces of side walls of the housing. 7. An electronic control apparatus according to any one of Claims 1 to 6, wherein the engagement protrusions each are elastically deformed along a parallel direction to the side wall of the housing, and are inserted into the engagement holes to be engaged thereto. 8. An electronic control apparatus according to any one of Claims 1 to 7, wherein proximal end portions of the engagement protrusions are fitted into insert ports of the engagement holes to position the cover with respect to the housing. 9. An electronic control apparatus according to any one of Claims 1 to 8, wherein the engagement holes are formed to be opposed to the heat sink. 10. An electronic control apparatus according to any one of Claims 1 to 9, wherein the circuit board is sandwiched between the cover and the housing to be held therebetween. 11. An electronic control apparatus according to any one of Claims 1 to 10, wherein a first groove portion is formed between the housing and the cover, whereas a second groove portion is formed between the housing and the heat sink, wherein the attachment means are provided inside the first groove portions, and wherein the first groove portion and the second groove portion are filled with an adhesive resin. 12. An electronic control apparatus according to Claim 11, wherein the first groove portions are formed in peripheral edge portions of the cover, and wherein the first groove portions and the second groove portions each have an opening portion formed to be open in the same direction.

Full Text

ELECTRONIC CONTROL APPARATUS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic control apparatus used for, for example, an electric power steering device for assisting in biasing a steering device of a vehicle with a rotary force of an electric motor.
2. Description of the Related Art
Conventionally, there is known an electronic control apparatus, which includes a field effect transistor (FET) as a semiconductor switching element, which being a power device to be mounted on a metal substrate, and has a structure in which a connection member fixed onto the metal substrate, for electrically connecting the metal substrate and components provided outside the metal substrate to each other.
For example, an electronic control apparatus described in JP 3644835 B (FIG. 2) (hereinafter, referred to as Patent Document 1) includes a power substrate, a housing, a control substrate, a connection member, a heat sink, and a case. On the power substrate, a bridge circuit including the semiconductor switching elements for switching a current of an electric motor is mounted. The housing includes a conductive plate or the like which is insert molding into an insulating resin and a high-current component mounted thereon. A low-current component such as a microcomputer is mounted on the control substrate. The connection member electrically connects the power substrate, and the housing and the control substrate to each other. The heat sink is brought into close contact with the power substrate. The case is formed by press molding of a metal plate to cover the power substrate, the housing, and the control substrate, and is attached to the heat sink.
In addition, an electronic control apparatus described in JP 2003-309384 A (FIG. 3) (hereinafter, referred to as Patent Document 2) includes a cover, a printed circuit board, a case, and a housing. An engagement portion corresponding to a snap hook formed on a periphery of the cover is engaged with a portion to be engaged formed for the case, to thereby attach the cover to the case in a removable manner.

In the electronic control apparatus described in Patent Document 1 described above, top and side surfaces of an apparatus main body including the power substrate, the housing, and the control substrate therein are covered with the case formed by press molding of the metal plate. Therefore, the electronic control apparatus has a problem in that a volume as well as a mass is increased.
Moreover, a caulking tab formed on an end surface of the case is caulked to secure the case to the heat sink. Therefore, the electronic control apparatus has another problem in that a securing operation is complicated.
On the other hand, in the electronic control apparatus described in Patent Document 2 described above, the snap hook formed on the periphery of the cover is engaged with the portion to be engaged formed in an outer peripheral portion of the case, and a position at which the snap hook is engaged with the portion to be engaged is externally exposed. Therefore, this conventional electronic control apparatus has a problem in that there is a fear that the cover is unintentionally detached from the case by an external shock applied on the position where the engaged portion between the snap hook and the portion to be engaged is exposed.
SUMMARY OF THE INVENTION
The present invention is devised to solve the problems described above, and has an object of providing an electronic control apparatus which may be reduced in weight cis well as in size and has improved operability in assembly and improved reliability in attachment of a cover to a housing.
An electronic control apparatus according to the present invention includes:
a housing made of an insulating resin, the housing having opening portions at both ends thereof;
a heat sink attached to one of the ends of the housing;
a power device mounted onto the heat sink;
a circuit board provided so as to be opposed to the heat sink, the circuit board carrying an electronic circuit including a control circuit for controlling the power device;
a cover, which is made of an insulating resin to be attached to another end of the housing, for housing the power device and the circuit board in cooperation with
2

the heat sink; and
attachment means for attaching the cover to the housing, wherein the attachment means includes:
engagement protrusions formed on the cover; and engagement holes provided to the housing, and the engagement protrusions are inserted into the engagement holes, respectively, to be engaged thereto so that the cover is attached to the housing.
According to the electronic control apparatus of the present invention, because the cover and the housing are made of the insulating resin, the weight is reduced. Moreover, the engagement protrusions of the cover are inserted into the engagement holes of the housing to be engaged thereto, thereby fixing the cover to the housing. Therefore, the effects such as a reduction in size, improved operability in assembly, and improved reliability in attachment of the cover to the housing may be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
Fig. 1 is an exploded perspective view illustrating an electronic control apparatus according to a first embodiment of the present invention;
FIG. 2 is a side sectional view of the electronic control apparatus illustrated in FIG. 1;
FIG. 3 is a sectional perspective view of the electronic control apparatus, which is cut along a direction perpendicular to the side cross-section of FIG 2;
FIG. 4 is a sectional perspective view of the electronic control apparatus illustrated in FIG. 1, which is cut along the same direction as that of the side cross-section of the electronic control apparatus of FIG. 2 and is viewed from the direction opposite to that of FIG. 2;
FIG. 5 is a sectional perspective view of the electronic control apparatus illustrated in FIG. 1, which is cut along a direction parallel to the cross section of the electronic control apparatus of FIG. 3;
FIG. 6 is a perspective view illustrating a cover illustrated in FIG 1; and
FIG 7 is a sectional view of a principal part, illustrating the electronic control

apparatus according to a second embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, an electronic control apparatus according to each embodiment of the present invention is described based on the accompanying drawings. In each of the drawings, the same or equivalent components or parts are denoted by the same reference numerals for description.
First Embodiment
FIG. 1 is an exploded perspective vievi/ illustrating an electronic control apparatus 1 according to a first embodiment of the present invention. FIG. 2 is a side sectional view of the electronic control apparatus 1 illustrated in FIG. 1. FIG. 3 is a sectional perspective view of the electronic control apparatus 1 cut along a direction perpendicular to the side cross-section of the electronic control apparatus 1 of FIG. 2. FIG. 4 is a sectional perspective view illustrating the electronic control apparatus 1, which is cut along the same direction as that of the side cross section of the electronic control apparatus 1 of FIG. 2 and is viewed from a direction opposite to that of FIG. 2. FIG. 5 is a sectional perspective view illustrating the electronic control apparatus 1 illustrated in FIG. 1 which is cut along a direction parallel to the cross section of the electronic control apparatus 1 of FIG. 3. FIG. 6 is a perspective view illustrating a cover 7 illustrated in FIG. 1.
The electronic control apparatus 1 includes a housing 3, a heat sink 5, semiconductor switching elements 2, a circuit board 4, and the cover 7. The housing 3 is made of an insulating resin and has a box-like shape with opening portions formed on both sidejs. The heat sink 5 is made of aluminum, and is fixed onto one of the opening portions of the housing 3. Each of the semiconductor switching elements 2 corresponds to a power dcjvice mounted on the heat sink 5. The circuit board 4 is provided parallel to the heat sink 5 to be opposed thereto. An electronic circuit including a control circuit for controlling the semiconductor switching elements 2 is formed on the circuit board 4. The cover 7, which is made of an insulating resin is attached onto the other opening portion of the housing 3, and houses the semiconductor switching elements 2 and the circuit board 4 therein in cooperation with the heat sink 5.

The cover 7 has engagement protrusions 7a, each including a hook portion 7b formed at an end. A pair of the engagement protrusions 7a are formed vertically on an outer peripheral edge of a surface of the cover 7, which is opposed to the circuit board 4, while their hook portions 7b are oriented in the opposite directions. Each pair of the engagement protrusions 7a is formed on each side of the cover 7. The pairs of protrusions 7a provided on the opposed sides are arranged in point symmeti7 with respect to a center of the surface of the cover 7, which is opposed to the circuit board 4.
On an inner wall surface of each of side walls 3b of the housing 3 surrounding the components, engagement holes 3c penetrating through the housing 3 in a direction, in which the engagement protrusions 7a of the cover 7 are inserted, are integrally formed of the insulating resin. On opposed inner wall surfaces of the engagement holes 3c, convex portions 3d and tapered portions 3e are respectively formed. The hook portions 7b of the engagement protrusions 7a are locked to the convex portions 3d. The tapered portions 3e gradually elastically deform the pair of hook portions 7b in a direction parallel to the side walls 3b of the housing 3 to allow the hook portions 7b to get closer to each other as the engagement protrusions 7a are inserted.
Therefore, when the pair of engagement protrusions 7a are inserted into the engagement holes 3c, the hook portions 7b of the engagement protrusions 7a are gradually deformed inward by the tapered portions 3e. Then, each of the hook portions 7b passes over the convex portion 3d to be engaged thereto. As a result, the cover 7 is attached to the housing 3.
A fitting portions 7c are formed at proximal end portions of the pair of engagement protrusions 7a. The fitting portions 7c are fitted into an insert port 3f of the engagement holes 3c to position the cover 7 and the housing 3.
F-urther, the heat sink 5 is provided on the side of the engagement holes 3c, which is opposite to the insert port 3f. The heat sink 5 closes the engagement holes 3c.
Note that the engagement protrusions 7a formed on the cover 7 and the engagement holes 3c provided to the housing 3 constitute attachment means for attaching the cover 7 to the housing 3.

Further, the electronic control apparatus 1 includes, as illustrated in FIG 2. conductive plates 6a and 6b and a plate spring 21. Each of the conductive plates 6a has a base portion integrally formed with the housing 3 by insert molding of an insulating resin 3a, and electrically connects the circuit board 4 and each of the semiconductor switching elements 2 to each other. The conductive plate 6b has a base portion integrally formed with the housing 3 by the insert molding using the insulating resin 3a, and electrically connects the circuit board 4 and power connector terminals 8a to each other. The plate spring 21, which is made of a metal, is an elastic member for pressing an insulating resin package of each of the semiconductor switching elements 2 to bring a heat spreader hs into close contact with the heat sink 5.
The plate spring 21 is secured to the hecit sink 5 by a screw 20 through an intermediation of the housing 3.
A vehicle connector 8 to be electrically connected to a wiring of a vehicle is provided on one side surface of the housing 3, whereas a motor connector 9 to be electrically connected to an electric motor (not shown) and a sensor connector 10 to be electrically connected to a torque sensor (not shown) are provided on the other side surface.
The vehicle connector 8 includes: the power connector terminals 8a to be electrically connected to a battery (not shown) of the vehicle; and signal connector terminals 8b to/from which a signal is input/output through the wiring of the vehicle. Further, the motor connector 9 includes motor connector terminals 9a, whereas the sensor connector 10 includes sensor connector terminals 10a.
The conductive plates 6a electrically connect the circuit board 4 and the semiconductor switching element 2 to each other. And the conductive plate 6b is electrically connected to the power connector terminal 8a. Together with the conductive plates 6a and the conductive plates 6b, the power connector terminals 8a, the signal connector terminals 8b, the motor connector terminals 9a, the sensor connector terminals 10a and the like are formed by the insert molding in the housing 3. At the same time, the vehicle connector 8, the motor connector 9, and the sensor connector 10 are formed integrally with the housing 3.
Further, on both side wall surfaces of the housing 3 on the side of the

opening portion opposite to the opening to which the heat sink 5 is attached, attachment leg portions 3L for attaching the electronic control apparatus 1 to the vehicle corresponding to an attachment target body are respectively formed.
As each of the semiconductor switching elements 2, a high-side MOSFET and a low-side MOSFET are integrated to form a half-bridge. As the semiconductor switching element 2, the half-bridge is housed within a single package. In addition, a pair of the semiconductor switching elements 2 constitute a bridge circuit for switching a current of the electric motor (not shown).
The semiconductor switching element 2 of the half-bridge includes five terminals, that is, a power supply terminal, a gate terminal of the high-side MOSFET, a bridge output terminal, a gate terminal of the low-side MOSFET, and a ground terminal. The power supply terminal, the bridge output terminal, and the ground terminal are high-current terminals through which a high current flows, whereas the gate terminal of the high-side MOSFET and the gate terminal of the low-side MOSFET are low-current terminals for signals.
A microcomputer 13 is mounted by soldering on a wiring pattern on a surface of the circuit board 4, whereas capacitors 14 for absorbing a ripple of a motor current are mounted by soldering on a wiring pattern of a bottom surface.
Although not shown in FIG. 1, a coil for preventing an electromagnetic noise generated at the time of a switching operation of the semiconductor switching elements 2 from leaking to the exterior, a motor current detecting circuit including a shunt resist or, a peripheral circuit element and the like are also mounted by soldering onto the wiring pattern formed on the circuit board 4.
Further, a plurality of through holes 4a, each having an inner surface plated with copper, are formed through the circuit board 4. The through holes 4a are electrically connected to the wiring pattern of the circuit board 4.
The heat sink 5 includes a heat sink main body 5a and an anodized aluminum film 5b corresponding to an insulating coating formed on a surface of the heat sink main body 5a. The heat sink 5 is formed in the following manner. An elongated extruded profile is formed by extruding aluminum or an aluminum alloy from a die. A heat sink material is fabricated by forming the anodized aluminum film 5b in advance on an entire surface of the extruded profile. The heat sink material is

cut to a desired length by a cutter, thereby forming the heat sink 5.
Outer peripheral end surfaces of the heat sink 5 on both sides in one direction, which are formed by cutting with the cutter, are cut surfaces 5c on which the heat sink main body 5a is externally exposed. The anodized aluminum film 5b is formed on the surfaces other than the cut surfaces 5c. The anodized aluminum film 5b is formed even on the surface on which the semiconductor switching elements 2 are mounted and the bottom surface thereof.
The cut surfaces 5c are opposed to the inner wall surfaces of the side walls 3b of the housing 3.
Although the heat sink 5 is fabricated by the extruded profile in this case, the heat sink 5 may also be fabricated by cutting of the heat sink material which is subjected to hot or cold forging.
Alternatively, the heat sink 5 may also be fabricated by cutting of a plate material which is subjected to hot or cold rolling.
Further alternatively, the four outer peripheral end surfaces of the heat sink main body 5a or a part thereof may be exposed to be opposed to the inner wall surfaces of the side walls 3b.
The plate spring 21 presses the surface of the insulating resin package of each of the semiconductor switching elements 2 to bring the heat spreader hs corresponding to a heat releasing portion of the ssemiconductor switching element 2 into close contact with the surface of the heat sink 5 on which the anodized aluminum film 5b is formed. Although the heat spreader hs of the semiconductor switching element 2 is electrically connected to the bridge output terminal, the heat spreader hs is electrically insulated from the heat sink 5 by the anodized aluminum film 5b.
The heat sink 5 has small concavity and convexity on its surface. Therefore, even when the heat spreader hs of the semiconductor switching element 2 is brought into close contact with the heat sink 5 by a function of the plate spring 21, a slight gap is generated therebetween. By the effects of the slight gap, a thermal resistance of a heat transfer path for releasing heat generated in the semiconductor switching elements 2 to the heat sink 5 is increased. In order to eliminate the gap, a highly thermal conductive adhesive resin (not shown) is applied between the heat spreader hs and the anodized aluminum film 5b of the heat sink 5 to bring the heat spreader

hs and the heat sink 5 into close contact witli each other to fix them.
As another means of eliminating the gap between the heat spreader hs of the semiconductor switching element 2 and the heat sink 5, a highly thermal conductive grease may be provided therebetween.
The plate spring 21 is formed by, for example, a copper alloy plate having spring properties, such as a phosphor bronze plate for spring, which is subjected to press working using a press working machine, The plate spring 21 includes: pressure portions 21a for pressing the insulating resin packages of the pair of adjacent semiconductor switching elements 2; and engagement portions 21b respectively extending perpendicular to the pressure portions 21a. The engagement portions 21b are pressed-fitted into between a pair of holding portions 3b formed of the insulating resin integrally with the housing 3 to be engaged thereto. Further, for the plate spring 21, a slit 21c is formed in an extended portion extending from both sides of one of the engagement portions 21 b.
A holding member H having functions of holding the circuit board 4 and of connecting the ground terminal of the circuit board 4 to the heat sink 5 is press-fitted into the slit 21 c. A press-fit terminal portion Hp formed at a top of the holding portion H is press-fitted into the through hole 4a of the circuit board 4 to electrically connect the wiring pattern of the circuit board 4 and the heat sink 5 to each other through the press-fit terminal portion Hp, the holding member H, the plate spring 21, and the screw 20.
Although the plate spring 21 is made of the copper alloy plate having the spring properties such as the phosphor bronze plate for spring in this case, the plate spring 21 may be made of other materials such as a stainless steel plate for spring.
A proximal end portion of each of the conductive plates 6a, which is exposed from the insulating resin 3a of the housing 3, is connected to the tops of the power supply terminal, the bridge output terminal, the ground terminal, and the gate terminal of each of the semiconductor switching elements 2 by laser welding.
A press-fit terminal portion 6p is formed on each of the conductive plates 6a. The press-fit terminal portions 6p are press-fitted into the through holes 4a of the circuit board 4. As a result, each of the terminals of the semiconductor switching elements 2 and the wiring pattern of the circuit board 4 are electrically connected to

each other.
The conductive plates 6a are arranged to overlap each other to extend In a direction in which each of the terminals of the semiconductor switching elements 2 extends. Further, the terminals of each of the semiconductor switching elements 2 are arranged on a surface of each of the conductive plates 6a, which is opposed to the heat sink 5. Each of the terminals of the semiconductor switching elements 2 is formed to have a width of 0.8 mm and a thickness of 0.5 mm at an interval of 1.7 mm between the terminals.
A high current flows through the conductive plate 6a which is connected to the power supply terminal, the bridge output terminal, and the ground terminal corresponding to the high-current terminals of the semiconductor switching element 2. Because each of the conductive plates 8a is made of a rolled copper alloy, a thickness of the conductive plate 6a to be connected to the high-current terminals is required to be increased when a rolled surface (surface) of the conductive plate 6a and the high-current terminals of the semiconductor switching element 2 are welded to each other. However, in terms of formation of the press-fit terminal portions and the press working, it is difficult to increase the thickness of each of the conductive plates 6a.
Therefore, in the first embodiment, the thickness of each of the conductive plates 6a is set to the same value of 0.8 mm as that of the width of each of the terminals of the semiconductor switching element 2. Instead, a width of each of the conductive plates 6a is set larger than the thickness to allow an end surface perpendicular to the rolled surface to be welded to the terminals of the semiconductor switching element 2.
Specifically, the conductive plate 6a is formed to have a larger size in a bonding direction with the terminals of the semiconductor switching element 2 than that in a direction perpendicular to the bonding direction (size in a width direction).
Because a low current flows through the conductive plate 6a used for signals, it is not necessary to take a reduction in electric resistance into consideration. However, this conductive plate 6a is made of the same material as that of the conductive plate 6a through which the high current flows.
The conductive plates 6a are made of a highly conductive copper alloy with

high strength or phosphor bronze in view of an electrical conductivity for allowing the high current to flow and a mechanical strength for forming the press-fit temninal portions 6p. For the conductive plate 6a formed by using phosphor bronze, the motor current of, for example, 30A or lower is used.
Each of the terminals of the semiconductor switching element 2 is bent in the same crank-like shape with a standing portion and a lying portion in the middle, and extends in the same direction. A first bent portion 2a corresponding to a bent portion of each of the terminals of the semiconductor switching element 2 on the distal end side is formed at an acute angle. A second bent portion 2b corresponding to a bent portion on the main body side of the semiconductor switching element 2 is formed to be upright at a right angle.
As illustrated in FIG. 2, on an upper surfeice of a middle portion of the heat sink 5, which has a larger thickness as compared with that of both sides, the heat spreader hs corresponding to the heat releasing portion of the semiconductor switching element 2 is mounted. On the other hand, above a small-thickness portion of the heat sink 5 on one side, bent welded portions of the terminals of the semiconductor switching element 2 are located.
The welded portions of the terminals of the semiconductor switching element 2, which are to be welded to the conductive plate 6a, are separated away from the heat spreader hs. In addition, the heat sink 5 is not attached yet at the time of welding. Therefore, the main body of each of the semiconductor switching elements 2 does not become an obstacle to the laser welding.
A laser beam LB is radiated from a direction of the attachment of the heat sink 5 to the surfaces of the terminals of the semiconductor switching element 2. As a result, the terminals of the semiconductor switching element 2 are laser-welded to the conductive plate 6a.
Moreover, each of the terminals of the semiconductor switching element 2 is formed to have the first bent portion 2a formed at the acute angle, and is pressed against the conductive plate 6a by bending elasticity. In this state, the vicinity of the distal end portion of each of the terminals of the semiconductor switching element 2 is irradiated with the laser beam LB to be welded to the conductive plate 6a.
At this time, a gap between each of the terminals of the semiconductor

switching element 2 and the conductive plate 6a increases from the distal end portion toward the first bent portion 2a. As a result, the vicinity of the distal end portion corresponding to the vicinity of the welded portion is pressed against the conductive plate 6a by the bending elasticity
As illustrated in FIG. 2, a positioning portion 3h for positioning each of the semiconductor switching elements 2 and the housing 3 is provided to the housing 3. The positioning portion 3h has a tapered portion at its distal end. The positioning portion 3h is guided by the tapered portion to be inserted into a hole 2c formed in the heat spreader hs of the semiconductor switching element 2, thereby performing the positioning. The positioning portion 3h also performs the positioning for the direction in which each of the terminals of the semiconductor switching element 2 extends.
Moreover, as illustrated in FIG. 1, a pair of positioning portions 3k for positioning each of the terminals of the semiconductor switching elements 2 and the conductive plates 6a are formed to the housing 3 in a similar manner to a positioning portions 3h, and the positioning portions 3k are opposed mutually. The positioning portions 3k perform positioning for a direction perpendicular to the extending direction of each of the terminals of the semiconductor switching element 2.
The positioning portions 3k are formed on both outer sides of the terminals of each of the semiconductor switching elements 2. Each of the positioning portions 3k has a tapered portion at its distal end. The outer side of each of the terminals of the semiconductor switching element 2 is guided by the tapered portion to position each of the terminals of the semiconductor switching element 2 and the conductive plates 6a.
Each of the terminals of the semiconductor switching element 2, which is positioned by the positioning portions 3h and 3k, is welded to the conductive plate 6a.
Each of the terminals of the semiconductor switching element 2 is provided to be separated away from an axis AX of FIG. 2, which corresponds to a press-fitting direction of the press-fit terminal portions 6p, in a horizontal direction to be welded to the conductive plate 6a.
The insulating resin 3a is interposed on an extension of the axis AX between

the conductive plate 6a and the heat sink 5. As a result, a press-fit force for press-fitting the press-fit terminal portions 6p into the through holes 4a of the circuit board 4 is received by the heat sink 5 through the insulating resin 3a.
Therefore, the welded portion for the laser welding is distant from the insulating resin 3a which inhibits the welding. In addition, because the insulating resin 3a is interposed between the conductive plate 6a and the heat sink 5 when the press-fit terminal portions 6p are press-fitted into the through holes 4a, a technique of the laser welding and a technique of the press-fitting to the through hole 4a may be both employed.
The laser beam LB is radiated to the surface of each of the terminals of the semiconductor switching element 2, thereby connecting the terminals of the semiconductor switching element 2 to the conductive plates 6a. Therefore, it is necessary to prevent the degradation and melting damage of the insulating resin 3a due to heat generated by the laser welding.
Moreover, it is also necessary to prevent the degradation and melting damage of the insulating resin 3a in the vicinity of the laser-welded portion and the degradation of the press-fit terminal portions 6p of the conductive plate 6a due to reflected light of the laser beam LB generated on the surfaces of the terminals of the semiconductor switching element 2 at the time of laser welding.
Further, it is also necessary to prevent gases from adhering to the press-fit terminal portions 6p of the conductive plate 6a at the time of laser welding. A gas is generated from a melted portion of each of the terminals of the semiconductor switching element 2. Moreover, a gas is generated from the insulating resin 3a in the vicinity of the laser-welded portion due to heat of the laser welding, or the reflected light.
In the first embodiment, the proximal end portion of each of the conductive plate 6a, which is welded to the terminals of the semiconductor switching element 2, is formed in a comb-like pattern to be exposed from the insulating resin 3a of the housing 3. As a result, the insulating resin 3a may be less affected by the heat and the reflected light generated at the time of laser welding.
Moreover, the press-fit terminal portions 6p of the conductive plate 6a are provided on the cover 7 side, whereas the laser-welded portion is arranged on the

heat sink 5 side. In this manner, a distance beKveen the press-fit terminal portions 6p and the laser-welded portion is increased. As a result, the press-fit terminal portion 6p is less affected by the heat, reflected I ght, and gas generated at the time of laser welding.
Moreover, the insulating resin 3a is interposed between the press-fit terminal portions 6p and the laser-welded portion. As a result, the reflected light generated at the time of laser welding can hardly reach the press-fit terminal portions 6p.
Two of the press-fit terminal portions 6p are formed on the conductive plate 6a through which the high current flows, whereas the single press-fit terminal portion 6p is formed on the conductive plate 6a for signals, through which the low current flows. Specifically, as illustrated in FIG. 1, seven press-fit terminal portions 6p are provided for each of the semiconductor switching elements 2.
As described above, the interval between the terminals of the semiconductor switching element 2 is 1.7 mm. Moreover, a diameter of the through hole 4a of the circuit board 4, into which the press-fit terminal portion 6p is press-fitted, is formed to be 1.45 mm.
In the first embodiment, the adjacent press-fit terminal portions 6p of the conductive plate 6a are arranged in a zigzag pattern. As a result, a distance between the adjacent press-fit terminal portions 6p is made larger than the interval between the terminals of the semiconductor switching element 2.
As illustrated in FIG. 4, end portions 15a of terminals 15 are bent at a right angle to respectively overlap end portions 8c of the signal connector terminals 8b and end portions 10b of the sensor connector terminals 10a. Overlapping surfaces of the end portions 15a and the end portions 8c and 10b are formed in parallel to the heat sink 5 to be welded to each other.
In this case, the end portions 8c of the signal connector terminals 8b and the end portions 10b of the sensor connector terminals 10a are provided on the side of the heat sink 5. Further, as in the case of the welding between the terminals of the semiconductor switching element 2 and the conductive plates 6a, the laser beam is radiated from the direction of attaching the heat sink 5 to the surfaces of the end portions 8c of the signal connector terminals 8b and the end portions 10b of the sensor connector terminals 10a. As a result, the signal connector terminals 8b and

the sensor connector terminals 10a are welded to the terminals 15.
A press-fit terminal portion 15p is formed at an end of each of the terminals 15 on the side opposite to the welded portion. The press-fit terminal portions 15p are press-fitted into the through holes 4a of the circuit board 4. As a result, the signal connector terminals 8b and the sensor connector terminals 10a connected to the terminals 15 are electrically connected to the wiring pattern of the circuit board 4.
As in the case of the conductive plates 6a, the press-fit terminal portions 15p of the terminals 15 are provided on the cover 7 side, whereas the laser-welded portions are provided on the heat sink 5 side. In this manner, a distance between the press-fit terminal portions 15p and the laser-welded portions is increased. As a result, the press-fit terminal portions 15p are less affected by the heat, reflected light, and gas generated at the time of laser welding.
The motor connector terminals 9a are connected to an end of the conductive plate 6a to which the bridge output terminal of the semiconductor switching element 2 is connected, the end being on the side opposite to the proximal end portion. The motor connector terminals 9a are provided on a surface of an end portion of the conductive plate 6a, which is opposed to the heat sink 5.
The laser beam LB is radiated from the direction of the attachment of the heat sink 5 to the surfaces of the motor connector terminals 9a. As a result, as in the case where the conductive plate 6a and the bridge output terminal of the semiconductor switching element 2 are welded to each other, the motor connector terminals 9a are welded to the conductive plate 6a.
The motor current output form the bridge output terminal of the semiconductor switching element 2 passes not through the circuit board 4 but directly through the motor connector terminals 9a to flow into the electric motor (not shown). The press-fit terminal portions 6p extending toward the circuit board 4 are formed in a middle portion of the conductive plate 6a which is connected to the bridge output terminal of the semiconductor switching element 2. In this manner, a signal for monitoring a voltage of the motor connector terminals 9a is output to the circuit board 4.
As illustrated in FIG. 2, the power connector terminals 8a are connected to the conductive plate 6b. The power connector terminals 8a are provided on a

surface of an end of the conductive plate 6b, which is opposed to the heat sink 5. Then, the laser beam LB is radiated from the direction of the attachment of the heat sink 5 to the surfaces of the power connector terminals 8a to weld the power connector terminals 8a to the conductive plate 6b as in the case of the connection of the motor connector terminals 9a to the conductive plate 6a.
The press-fit terminal portions 6p extending toward the circuit board 4 are formed on the conductive plate 6b. The press-fit terminal portions 6p are press-fitted into the through holes 4a of the circuit board 4. As a result, the conductive plate 6b and the wiring pattern of the circuit board 4 are electrically connected to each other. Then, a current from the battery of the vehicle is supplied to the circuit board 4 through the power connector terminals 8a, the conductive plate 6b, and the press-fit terminal portions 6p.
The press-fit terminal portions 6p, 15p, and Hp are respectively press-fitted into the through holes 4a to mechanically hold the circuit board 4.
The conductive plates 6a and 6b, the terminals 15, and the holding member H are formed by insert molding of the insulating resin 3a of the housing 3. Because the insulating resin 3a is interposed between the conductive plates 6a and 6b, the terminals 15, and the holding member H, and the heat sink 5, the press-fit force may be received by the heat sink 5 when the press-fit terminal portions 6p, 15p, and Hp are press-fitted into the through holes 4a.
Due to fabrication precision, however, a slight gap is generated between the insulating resin 3a and the heat sink 5.
In the press-fitting, a relative height accuracy between the press-fit terminal portions 6p, 15p, and Hp and the circuit board 4 is important. However, the generation of the slight gap between the insulating resin 3a and the heat sink 5 degrades the relative height ciccuracy.
Therefore, for example, as illustrated in F'IG. 2, an adhesive (not shown) is applied in a gap between the insulating resin 3a below the conductive plate 6a and the heat sink 5 and a gap between the insulating resin 3a below the conductive plate 6b and the heat sink 5 to eliminate the effects of the gaps.
As illustrated in FIG. 5, inside a peripheral edge of each of the fitting portions 7c of the cover 7, a holding portion 7d is formed. On the inner side of each of the

engagement holes 3c of the housing 3, a holding portion 3m is formed. The circuit board 4 is sandwiched between the holding portions 7d and 3m to be held therebetween.
Alternatively, the holding portions 7d and 3m may be formed at the positions where the press-fit terminal portions 6p, 15p, and Hp are not located to mechanically hold the circuit board 4 by the press-fit terminal portions 6p, 15p, and Hp and the holding portions 7d and 3m.
Next, a procedure of assembling the electronic control apparatus 1 configured as described above is described.
First, a cream solder is applied onto the circuit board 4. Then, the components such as the microcomputer 13 and the peripheral circuit elements thereof are arranged thereon. Thereafter, the cream solder is melted by using a reflow device to solder each of the components onto the circuit board 4.
Next, the terminals of each of the semiconductor switching elements 2 are bent in a crank-like shape. Then, the semiconductor switching elements 2 are arranged on the housing 3 with the opening portion on the side where the heat sink 5 is attached being oriented upward. At this time, the main body and each of the terminals of each of the semiconductor switching elements 2 are guided and positioned by the positioning portions 3h and 3k to superimpose each of the terminals on the conductive plate 6a.
Thereafter, the laser beam LB is radiated from the terminal side of the semiconductor switching element 2 to laser-weld each of the terminals and the conductive plates 6a to each other.
Similarly, the laser beam LB is radiated from the side of the power connector terminals 8a and the motor connector terminals 9a to laser-weld the power connector terminals 8a and the conductive plate 6b to each other and the motor connector terminals 9a and the conductive plate 6a to each other.
The laser beam is also radiated to the surfaces of the end portions 8c of the signal connector terminals 8b and the end portions 10b of the sensor connector terminals 10a to laser-weld the signal connector terminals 8b and the sensor connector terminals 10a to the terminals 15.
Next, on a portion of the heat sink 5, on which each of the semiconductor

switching elements 2 is mounted, a highly thermal conductive adhesive resin (not shown) is printed at a small thickness. Further, an adhesive (not shown) is applied to the portions of the heat sink 5, which are opposed to the insulating resin 3a in the vicinity of the regions where the conductive plates 6a and 6b, the terminals 15, and the holding member H are formed by insert-molding.
Thereafter, the housing 3, for which the laser welding is completed, is inverted to cause the opening portion, to which the heat sink 5 is attached, to be oriented downward. Then, the housing 3 is placed on the heat sink 5. Further, the engagement portions 21b are press-fitted to an inner side of a holding portion 3g to lock the plate spring 21 to the housing 3. Simultaneously, the slit 21c is press-fitted into the holding member H.
Next, the plate spring 21 as well as the housing 3 is secured to the heat sink 5 with the screws 20. The semiconductor switching elements 2 are pressed against the heat sink 5 by the pressing portions 21a of the plate spring 21. Thereafter, the adhesive resin and the adhesive are cured in a furnace kept at high temperature.
Subsequently, the distal ends of the press-fit terminal portions 6p, 15p, and Hp are inserted into the through holes 4a of the circuit board 4 to attach the circuit board 4 onto an upper part of the housing 3. Thereafter, the press-fit terminal portions 6p, 15p, and Hp are press-fitted into the through holes 4a by using the pressing machine.
Next, the engagement protrusions 7a of the cover 7 are inserted into the engagement holes 3c of the housing 3 to position the cover 7 on the opening portion of the housing 3.
Thereafter, the cover 7 is pressed to be engaged to the housing 3, thereby completing the assembly of the electronic control apparatus 1.
As described above, according to the electronic control apparatus 1 of the first embodiment, the attachment means for attaching the cover 7 to the housing 3 includes the engagement protrusions 7a formed on the cover 7 and the engagement holes 3c provided to the housing 3. The engagement protrusions 7a are inserted into the engagement holes 3c to fix the cover 7 to the housing 3. Therefore, the operability in assembly of the electronic control apparatus 1 is improved.
Further, because the cover 7 and the engagement protrusions 7a are

integrally formed of the insulating resin, the electronic control apparatus 1 is reduced in weight.
Moreover, the hook portion 7b is formed at the end of each of the engagement protrusions 7a. In addition, on the inner wall surface of the engagement holes 3c, the convex portion 3d for engaging the hook portion 7b of the engagement protrusion 7a and the tapered portion 3e for elastically deforming the hook portion 7b as the engagement protrusion 7a is inserted are formed. Therefore, the insertion of the engagement protrusion 7a is facilitated to improve the operability in assembly of the electronic control apparatus 1.
Moreover, because the cover 7 is surely locked to the housing 3, dust resistance of the electronic control apparatus 1 is improved.
The two engagement protrusions 7a form a pair to protrude in a vertical direction. The hook portions 7b of the pair of the engagement protrusions 7a are formed to be oriented in the opposite directions. In addition, on the opposed inner wall surfaces of the engagement holes 3c, the convex portion 3d and the tapered portion 3e are formed. Thus, the insertion of the engagement protrusion 7a is facilitated to improve the operability in assembly of the electronic control apparatus 1.
F-urther, because the cover 7 is surely locked to the housing 3, the dust resistance of the electronic control apparatus 1 is improved.
F-urther, because the engagement holes 3c are integrally formed of the insulating resin on the inner wall surfaces of the side walls 3b of the housing 3, the electronic control apparatus 1 may be reduced in size.
Moreover, the attachment means for attaching the cover 7 to the housing 3 are invisible from the outside. In addition, it is hard to easily remove the cover 7 from the housing 3. Therefore, illegal modification of an internal structure of the electronic control apparatus 1 may be prevented.
Moreover, when the engagement protrusions 7a are inserted into the engagement holes 3c, the hook portions 7b are configured to be elastically deformed in a direction parallel to the side walls 3b of the housing 3 by the tapered portions 3e. Therefore, a bulge of the attachment means from the side walls 3b is reduced to reduce the electronic control apparatus 1 in size.
Further, the fitting portions 7c are formed at the proximal end portions of the

engagement protrusions 7a. The fitting portions 7c are fitted into the insert ports 3f of the engagement holes 3c to position the cover 7 and the housing 3. Therefore, the engagement protrusions 7a are prevented from being damaged by the application of an excessive stress due to an external force applied on the cover 7. As a result, the dust resistance of the electronic control apparatus 1 is improved.
Further, because the hook portions 7b of the engagement protrusions 7a are formed to be oriented in the opposite directions, the engagement holes 3c may be reduced in size. As a result, the electronic control apparatus 1 may be reduced in size.
Further, because the pairs of engagement protrusions 7a are formed on each side of the cover 7, the cover 7 may be surely locked to the housing 3. As a result, the dust resistance of the electronic control apparatus 1 is improved.
In addition, an abnormal noise generated at the boundary surface between the cover 7 and the housing 3 due to a vibration is suppressed.
Further, the engagement protrusions 7a provided on the opposed sides are arranged in point symmetry with respect to the center of the plane parallel to the circuit board 4. Therefore, the cover 7 may be attached at a position rotated by 180 degrees. As a result, the operability in assembly of the electronic control apparatus 1 is improved.
Further, the heat sink 5 is arranged on the side opposite to the insert ports 3f to be opposed to the engagement holes 3c to allow the heat sink 5 to close the engagement holes 3c. Therefore, a foreign substance may be prevented from entering the electronic control apparatus 1, thereby improving the dust resistance of the electronic control apparatus 1.
Moreover, the illegal modification of the electronic control apparatus 1 may be prevented.
Moreover, because the circuit board 4 is sandwiched between the holding portions 7d formed on the cover 7 and the holding portions 3m formed on the housing 3 to be held therebetween, the vibration of the circuit board 4 may be suppressed to improve vibration resistance of the electronic control apparatus 1.
Further, the holding portions 7d are formed inside the peripheral edges of the fitting portions 7c of the cover 7, whereas the holding portions 3m are formed on the

inner sides of the engagement holes 3c of the housing 3. Therefore, the circuit board 4 is firmly held to improve the vibration resistance of the electronic control apparatus 1.
Second Embodiment
FIG. 7 is a sectional view illustrating a principal part of the electronic control apparatus 1 according to a second embodiment of the present invention.
FIG. 7 is a view illustrating the electronic control apparatus 1 being assembled. In FIG. 7, the heat sink 5 is situated above the cover 7.
In the second embodiment, a configuration is the same as that of the electronic control apparatus 1 of the first embodimient except for the configurations of the housing 3 and the cover 7.
Specifically, in the second embodiment, a groove 7e corresponding to a first groove portion is formed in an outer peripheral edge portion of the cover 7 along the entire periphery. The groove 7e is open toward the housing 3 side. A protrusion 3n is formed on an opening end portion of the housing 3 on the cover 7 side along the entire periphery. A space formed by the insention of the protrusion 3n into the groove 7e is filled with a silicon adhesive 31 corresponding to the adhesive resin.
The engagement protrusion 7a of the cover 7 is formed inside the groove 7e. The engagement protrusion 7a is inserted into the engagement hole 3c of the housing 3 to fix the cover 7 to the housing 3.
A groove 30 corresponding to a second groove portion is formed between an outer peripheral end surface of the heat sink 5 and an inner wall surface 3p of the opening portion of the housing 3. The groove 30 is filled with the same silicon adhesive 31 as that filling the groove 7e.
Moreover, the groove 7e and the groove 30 are open in the same direction. Further, the grooves 7e and 30 are filled with the silicon adhesive 31 from the same direction.
Although not shown, a respiratory hole for communicating the interior of the electronic control apparatus 1 and the exterior v^ith each other is provided to the housing 3. A water repellant filter which allows air to pass therethrough but not water to pass therethrough is attached onto the respiratory hole.
The procedure of assembling the electronic control apparatus 1 according to

the second embodiment is the sanie as that in the first embodiment until the step of press-fitting the press-fit terminal portions 6p, 15p, and Hp into the through holes 4a of the circuit board 4 by using the pressing machine.
Next, the water repellant filter (not shown) is attached onto a respiratory hole (not shown) formed through the housing 3 by thermal welding.
Thereafter, as illustrated in FIG. 7, the cover 7 is placed with the open side of the groove 7e being oriented upward. Then, the groove 7e is filled with the silicon adhesive 31.
Next, the engagement protrusion 7a of the cover 7 is inserted into the engagement hole 3c of the housing 3 with the surface, to which the cover 7 is to be attached, being oriented downward. Thereafter, the housing 3 is pressed to fix the cover 7 to the housing 3.
Thereafter, the groove 30 with the opening portion of the housing 3 being oriented upward is filled with the silicon adhesive 31. Next, while both the grooves 7e and 30 are oriented upward, the electronic control apparatus 1 is placed in the furnace at high temperature to cure the silicon adhesive 31.
After the silicon adhesive 31 is cured, the electronic control apparatus 1 is taken out from the furnace to be cooled. In this manner, the assembly of the electronic control apparatus 1 is completed.
The silicon adhesive 31 may be a cold setting adhesive.
The respiratory hole may be provided through the cover 7. and the water repellent filter may be attached onto the respiratory hole.
Moreover, the water repellent filter may be attached after the step of curing the silicon adhesive 31.
According to the electronic control appareitus 1 of the second embodiment, the groove 7e is formed in the outer peripheral edge portion of the cover 7, whereas the groove 30 is formed between the outer peripheral end surface of the heat sink 5 and the inner wall surface 3p of the opening portion of the housing 3. In addition, the grooves 7e and 30 are filled with the silicon adhesive 31.
As a result, the interior of the electronic control apparatus 1 is sealed from the exterior. Therefore, water or the like may be prevented from entering the interior

of the electronic control apparatus 1 from t.ie sxterior, thereby improving water resistance of the electronic control apparatus 1.
Moreover, the engagement protrusions 7a and the engagement holes 3c constituting the attachment means is provided inside the groove 7e.
As a result, the attachment means is prevented from being damaged by the external force, thereby improving the water resistance of the electronic control apparatus 1.
Because the grooves 7e and 30 are open upward in the same direction and are filled with the silicon adhesive 31 from the same direction, the silicon adhesive 31 does not outflow from the grooves 7e and 30 during the curing of the silicon adhesive 31.
As a result, together with the improvement of operability in assembly of the electronic control apparatus 1, the water resistance is improved.
Although each of the terminals of the semiconductor switching elements 2 and the conductive plates 6a are bonded to each other by the laser welding in the first and second embodiments described above, the bonding may be performed by other welding methods such as resistance welding and TIG welding.
Alternatively, the bonding may be performed by a method other than welding, such as ultrasonic bonding.
Moreover, in the above-mentioned embodiments, the half-bridge formed by integrating the high-side MOSFET and the low-side MOSFET is housed in one package to form the semiconductor switching element 2, and the two semiconductor switching elements 2 form a pair to constitute the bridge circuit for switching the current of the electric motor. However, the high-side MOSFET and the low-side MOSFET may be separately configured to allow four semiconductor switching elements 2 to constitute the bridge circuit.
Alternatively, the bridge circuit may be constituted by six semiconductor switching elements 2 to control the driving of a three-phase brushless motor.
Further, though the semiconductor switching element 2 is used as the power device, other power devices such as a diode and a thyristor may be used.
Although the thickness of the conductive plate 6a is set to 0.8 mm in the above-mentioned embodiments, the thickness of the conductive plate 6a may be set

to other values such as 1.0 mm and 1.2 mm in view of the current flowing through each of the conductive plates 6a, the interval between the terminals of the semiconductor switching element 2, and the like.
The example in which the present invention is applied to the electric power steering device for the automobile has been described above. However, the present invention is also applicable to an electronic control apparatus dealing with the high current (for example, 25A or higher), which includes the power device, such as the electronic control apparatus for an anti-lock brake system (ABS) and the electronic control apparatus for air-conditioning, to obtain the same effects.

WHAT IS CLAIMED IS:
1. An electronic control apparatus, comprising:
a housing made of an insulating resin, the housing having opening portions at both ends thereof;
a heat sink attached to one of the ends of the housing;
a power device mounted onto the heat sink;
a circuit board provided so as to be opposed to the heat sink, the circuit board carrying an electronic circuit including a control circuit for controlling the power device;
a cover, which is made of an insulating resin to be attached to another end of the housing, for housing the power device and the circuit board in cooperation with the heat sink; and
attachment means for attaching the cover to the housing,
wherein the attachment means comprises:
engagement protrusions formed on the cover; and engagement holes provided to the housing, and the engagement protrusions are inserted into the engagement holes, respectively, to be engaged thereto so that the cover is attached to the housing.
2. An electronic control apparatus according to Claim 1, wherein each of the engagennent protrusions has an end portion formed in a hook-like shape.
3. An electronic control apparatus according to Claim 2, wherein convex portions for engaging the hook-like shaped end portions, and tapered portions for gradually elastically deforming the hook-like shaped end portions while the engagement protrusions are being inserted toward the convex portion, are formed on inner wall surfaces of each of the engagement hole.
4. An electronic control apparatus according to any one of Claims 1 to 3, wherein the two engagement protrusions form a pair to be inserted into each of the engagement holes to be engaged thereto.

5. An electronic control apparatus according to any one of Claims 1 to 4. wherein the engagement holes are formed on inner sides of the housing.
6. An electronic control apparatus according to Claim 5, wherein the engagement holes are formed on inner wall surfaces of side walls of the housing.
7. An electronic control apparatus according to any one of Claims 1 to 6, wherein the engagement protrusions each are elastically deformed along a parallel direction to the side wall of the housing, and are inserted into the engagement holes to be engaged thereto.
8. An electronic control apparatus according to any one of Claims 1 to 7, wherein proximal end portions of the engagement protrusions are fitted into insert ports of the engagement holes to position the cover with respect to the housing.
9. An electronic control apparatus according to any one of Claims 1 to 8, wherein the engagement holes are formed to be opposed to the heat sink.
10. An electronic control apparatus according to any one of Claims 1 to 9,
wherein the circuit board is sandwiched between the cover and the housing to be
held therebetween.
11. An electronic control apparatus according to any one of Claims 1 to 10,
wherein a first groove portion is formed between the housing and the cover,
whereas a second groove portion is formed between the housing and the heat sink, wherein the attachment means are provided inside the first groove portions,
and
wherein the first groove portion and the second groove portion are filled with
an adhesive resin.
12. An electronic control apparatus according to Claim 11,
wherein the first groove portions are formed in peripheral edge portions of the

cover, and
wherein the first groove portions and the second groove portions each have an opening portion formed to be open in the same direction.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=Ur6hZzazhf4EZE7OiFy3aQ==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

278304

Indian Patent Application Number

2419/CHE/2009

PG Journal Number

53/2016

Publication Date

23-Dec-2016

Grant Date

20-Dec-2016

Date of Filing

06-Oct-2009

Name of Patentee

MITSUBISHI ELECTRIC CORPORATION

Applicant Address

7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310

Inventors:

#	Inventor's Name	Inventor's Address
1	TOMINAGA, TSUTOMU	C/O MITSUBISHI ELECTRIC CORPORATION, 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310
2	TANIGAWA, Masaaki	of c/o Mitsubishi Electric Engineering Company, Limited, 1-13- 5, Kudankita, chiyoda-ku, Tokyo 102-0073, Japan; a Japanese citizen

PCT International Classification Number

H01H 9/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2009-081737	2009-03-30	Japan