Title of Invention

A BRUSHED MOTOR

Abstract

The problem to be solved by the invention is to reduce fluctuation in performance of a brushed motor by stabilizing shape of lead wires (pigtail) through the manufacturing process of the brushed motor. Lead wire 3 comprising a bundle of plural conductive filaments such as stranded copper wires is connected to a brush 21, and has a solid lead 312 formed by applying a stiffening treatment such as welding, soldering, adhesion with an adhesive or caulking with a bush 35 in the neighborhood of a lead wire connection surface of the brush 21, particularly at the center of an erecting portion 31 of the lead wire erecting from the brush 21. Figure 1.

Full Text

The present invention relates to a brushed motor including brushes such as rotating armature type brushed motor and, more particularly, to a brushed motor preferably used in electric power steering systems. Figs. 13 to 16 show a conventional rotating armature type electric motor. Fig. 13 is a transversal sectional view of the mentioned conventional electric motor. Fig. 14 is a plan view of a brush holder used in the electric motor. Fig. 15 is an enlarged sectional view taken along the line X-X in Fig. 4, and Fig. 16 is an enlarged side view of a brush holding case and neighborhood thereof. Referring to Figs. 13 to 16, reference numeral 1 is an electric motor, numeral 11 is an armature, numeral 12 is a commutator, and numerals 13 and 14 are bearings. Numeral 15 is a yoke, numeral 16 is a magnet, numeral 17 is a housing, numeral 18 is a rotating shaft, and numeral 21 is brush holders. Numeral 22 is brush holding cases, numeral 23 is springs, numeral 24 is spring retainers, numeral 3 is lead wires generally referred to as pigtails connected to the brushes 21, numeral 4 is outgoing lines, and numeral 5 is an electrode plate connecting the lead wires 3 with the outgoing lines 4. The lead lire 3 comprises an erecting portion 31 erecting from its connection end to the brush 21 and extending in parallel to the rotating shaft 18, a bending portion 32 cascade- connected to the erecting portion 31, and a tail portion 33 cascade-connected to the bending portion 32. The lead wire 3 is connected to the outgoing lead wire 4 by welding an end of the tail portion 33 to the electrode plate 5. In the structure of the electric motor arranged as mentioned above, the brush 21 is slidably held in the brush holding case 22 directing in the direction of the arrow A (see Fig. 16) and, being pressed by the resilient force from the spring 23, slidably contacts with the commutator 12. In the electric power steering motor, the resilient force of the spring 23 is particularly designed to be a relatively small value in order to reduce loss torque of the motor and to reduce noise due to the sliding contact between the brush 21 and the commutator 12. As a result, the sliding contact of the brush 21 with the commutator 12 is easily affected by the shape of the lead wire 3 in the neighborhood of the connecting portion with the brush 21, particularly, by the shape at the part surrounding the erecting portion 31. In other words, the brush 21 with the lead wire 3 on its back slidably contacts with the commutator 12 while moving reciprocally in the direction of the arrow A within the brush holding case 22. Further, contact pressure and contact condition against the commutator 12 change depending on the shape of the lead wire 3, particularly, on the shape of the erecting portion 31, because of clearance existing between the brush 21 and the brush holding case 22 in the direction of the arrow B in Fig. 15. As a result, significant fluctuations occur in the aspects of loss torque, sliding contact noise of the brush, difference in performance between normal and reverse rotations, torque ripples, and others. As for the lead wire 3, in order to reduce the aforementioned influence, a stranded thin copper wires are used in many cases. Accordingly, the lead wire 3 has poor rigidity so that, even if the lead wire 3 has been shaped at the time of assembling the brush holder 2, the shape may frequently be deformed during transportation, etc. A further problem exists in that the erecting portion 31 is deformed because of the pulling force in the process of installing the armature 11 into the housing 17 in which it is required to pull the brush 21 into the brush holding case 22. Advantages of the Invention The present invention was made to solve the above-discussed problems and has an object of stabilizing the shape of lead wires through the entire manufacturing process of a brushed motor and reducing the fluctuation in performance of the brushed motor. To accomplish the foregoing object, a brushed motor according to the invention is described herein. Accordingly the present invention provides a brushed motor characterized in that solid leads each formed by connecting a lead wire composed of a bundle of a plurality of conductive filaments are connected to a brush, and a stiffening treatment is applied to the bundle of said conductive filaments in the neighborhood of a connecting end of the lead wire connected to said brush. It is preferable that the lead wire has an erecting portion erecting from a lead wire connection on the surface of the brush to which the lead wire is connected and extending in parallel or almost in parallel to a rotating shaft of the electric motor, and at least a part of said erecting portion is provided with a solid lead. As a result, contact condition between the brush and a commutator is kept stable and constant, and therefore fluctuation in the aspect of loss torque, sliding contact noise from the brush, difference in performance between normal and reverse rotations, torque ripples, and others of the electric motor can be reduced. It is also preferable that the erecting portion is a flexible mounting portion in which stiffening treatment is not applied to a root portion thereof, the flexible mounting portion having a length Ll from the lead wire connection on the surface of the brush, and the length Ll satisfying a following equation: Ll ^ t where: t is a wall thickness of a brush holding case for holding the mentioned brush. As a result, it becomes possible to prevent problems such as disconnection of the copper filaments, reduction in cross sectional area of the flexible mounting portion in the event that large stretch or elongation of the copper filaments takes place, or projection of the erecting portion from the opening provided in the brush holding case as a result of the reduction in cross sectional area. It is also preferable that the erecting portion has a bending portion cascade-connected to the erecting portion and in which a distance L3 of the erecting portion erecting from the lead wire connection on the surface of the brush to the mentioned bending portion satisfies a following equation: L3 > LI + L2 where: Ll is a length of the flexible mounting portion and L2 is a length of the solid lead. As a result, location and length of the solid lead formed in the erecting portion are appropriate, neither bending of the erecting portion by the external force applied during assembling of the electric motor nor dislocation of the brush in the brush holding case due to the bending occurs, and therefore slidability of the brush in the brush holding case is kept good. It is also preferable that, in sectional shape of the erecting portion of the solid lead in a direction orthogonal to a longitudinal direction, a side orthogonal to a sliding direction of the brush in the brush holding case is longer than the other side parallel to the sliding direction. As a result, it is certain that solid lead is a little easy to be deformed in the sliding direction of the brush in the brush holding case. But no substantial change occurs in the contact condition between the commutator and the brush because, even if any external force such as vibration or impact should act thereon, the solid lead does not fall down in the direction orthogonal to the sliding direction owing to large resistance to deformation in the orthogonal direction. It is also preferable that, in sectional shape of the erecting portion of the solid lead in a direction orthogonal to a longitudinal direction, a side parallel to a sliding direction of the brush in the brush holding case is longer than the other side orthogonal to the sliding direction. As a result, it becomes possible that, in order to weld the lead wire to an electrode plate, the rectangular cross sectional shape of the end of the lead wire to which stiffening treatment has been applied by welding is identical to the cross sectional shape of the solid lead. Therefore, man-hour and cost in the manufacturing process can be reduced. It is also preferable that the stiffening treatment is applied by welding or soldering conductive filaments forming the lead wire to each other. It is also preferable that the stiffening treatment is applied by joining conductive filaments forming a lead wire with an adhesive. It is also preferable that the stiffening treatment is applied by caulking the lead wire with a bush. As a result, the stiffening treatment can be adequately and efficiently applied to any desired portion of the erecting portion of the lead wire. It is also preferable that the lead wire has an erecting portion, a bending portion and a tail portion cascade-connected to the bending portion, and the tail portion extends in the direction orthogonal to the sliding direction of the brush in a brush holding case or in the sliding direction of the bush, and extends behind the mentioned brush. As a result, the shape of the mentioned lead wire is hardly deformed due to the external force applied thereto, and therefore favorable contact condition is kept between the commutator and the brush. Consequently, the fluctuations in the aspects of loss torque, sliding contact noise of the brush, difference in performance between normal and reverse rotations, or torque ripples of the electric motor, can be successfully reduced. It is also preferable that the electric motor according to the invention is an electric motor for use in electric power steering system. As a result, it becomes possible to produce steadily electric power steering motors of high performance with their fluctuation reduced. Drawings Fig. 1 is a plan view of a brush holder used in Embodiment 1 according to the present invention. Fig. 2 is an enlarged sectional view of a part taken along the line Y-Y in Fig. 1. Fig. 3 is an enlarged side view of the brush holding case and the neighborhood thereof in Embodiment 1 according to the invention. Fig. 4 is an enlarged sectional view of the part corresponding to Fig. 2 showing a comparative embodiment with Embodiment 1. Fig. 5 is a schematic view to explain Embodiment 2 according to the invention. Fig. 6 is an enlarged sectional view of a part taken along the line Y-Y in Fig. 1 to show Embodiment 3 according to the invention. Fig. 7 is an enlarged side view of the brush holding case and the neighborhood thereof in Embodiment 3 according to the invention. Fig. 8 is an enlarged sectional view of a part taken along the line Y-Y in Fig. 1 to show Embodiment 4 according to the invention. Fig. 9 is an enlarged side view of the brush holding case and the neighborhood thereof in Embodiment 4 according to the invention. Fig. 10 is a perspective view of a bush used in Embodiment 4 according to the invention. Fig. 11 is a transverse sectional view of an electric motor in Embodiment 5 according to the invention. Fig. 12 is a plan view of a brush holder used in Fig. 11. Fig. 13 is a transverse sectional view of an electric motor according to the prior art. Fig. 14 is a plan view of a brush holder used in Fig. 13. Fig. 15 is an enlarged sectional view of a part along the line X-X in Fig. 14. Fig. 16 is an enlarged side view of a brush holding case and the neighborhood thereof in the electric motor according to the prior art. Description of the Preferred Embodiments In the preferred embodiments hereinafter described, same reference numerals are designated to like parts so that description thereof may be omitted. Embodiment 1 . Figs. 1 to 3 show an electric motor according to Embodiment 1 of the invention, and in which Fig. 1 is a plan view of a brush holder used in Embodiment 1 according to the present invention, Fig. 2 is an enlarged sectional view of a part taken along the line Y-Y in Fig.l, and Fig. 3 is an enlarged side view of the brush holding case and the neighborhood thereof in Embodiment 1 according to the invention. In addition, as every transverse sectional view of the entire electric motor according to Embodiment 1 and that according to later described Embodiments 2 to 4 are substantially the same as that in Fig. 13, Fig. 13 is referred also in the description of Embodiments 2 to 4, and any further reference is omitted as far as transverse sectional view of the entire electric motor is concerned. Referring to Figs. 1 to 3, reference numerals 311, 312 and 313 are a flexible mounting portion, a solid lead, and an upper solid lead respectively located in an erecting portion 31 of a lead wire 3. Numeral 25 is an opening formed on an upper surface of a brush holding case 22, and numeral 26 is a stopper formed at the end of the opening 25. The erecting portion 31 almost vertically stands from the lead wire connection surface of the brush 21, in other words, in parallel to the rotating shaft 18 of the electric motor 1. A tail portion 33 is connected to an electrode plate 5 extending in the direction perpendicular to the direction of the arrow A so as to be connected with an outgoing lead line 4. The lead wire 3 may be made of, e.g., stranded thin copper wires of about 0.05 mm to 0.08 mm in diameter. The flexible mounting portion 311 is a portion without applying any stiffening treatment extending from a lead wire connection surface of a brush 21 to an end of the solid lead 312. In this Embodiment 1, the solid lead 312 is formed by applying a stiffening treatment to the substantially center part of the erecting portion in the lead wire 3. The stiffening treatment applied in this case is accomplished by welding stranded thin copper wires adjacent to one another to form the lead wire 3 using a welding machine. Thus, density of the welded thin copper wires increases as a result of such welding so that the solid lead 312 decreases in wire size to be smaller than the flexible mounting portion 311 or the upper solid lead 313, as illustrated. Sectional shape of the solid lead 312 (i.e., shape of the cross section perpendicular to the longitudinal direction of the erecting portion 31) is rectangular which is short in the direction parallel to the sliding direction of the brush 21 (see the arrow A indicated in Fig. 3) while being long in the direction orthogonal to the sliding direction of the brush 21 (see Fig. 2). As a result, the solid lead 312 is easy to be deformed in the direction of the arrow A but is hard to be deformed in the direction orthogonal to the direction of the arrow A. Therefore, no substantial changes occur in the contact condition between the commutator 12 and the brush 21 when any external force such as vibration force, impact force or others are applied thereto. As described above, the erecting portion 31 has the solid lead 312 near its central portion. Consequently, not only the solid lead 312 portion has a high rigidity, but also the flexible mounting portion 311 increases its rigidity to a certain extent due to the effect of the rigidity of the solid lead. As a result, even if the lead wire 3 is connected to the electrode plate 5, and the brush 21 is inserted and accommodated in the brush holding case 22 by grasping the solid lead 312 in the same manner as the prior art after, shape of the erecting portion 31 and the bending portion 32 does not substantially change, and the erecting portion 31 keeps a stable shape almost vertically standing with respect to a sliding surface 211 of the brush 21. Furthermore, due to the improvement in the rigidity of the solid lead 312 and the flexible mounting portion 311, the lead wire 3 can keep its initial configuration even if receiving any vibration or shock during transportation thereof or at the time of assembling the motor. The boundary line between the erecting portion 31 and the bending portion 32 is indicated by the line segment B running at right angle to the longitudinal axis of the erecting portion 31, and passing through the bending point 34 of the bending portion 32(see to Fig, 2). As a result, the upper solid lead 313 comes into contact with the bending portion at the line segment B. In addition, L3 shown in Fig. 2 indicates a length of the erecting portion 31 as defined above. Further, in Embodiment 1, as shown in Fig.2, the length LI of the flexible mounting portion 311 and the wall thickness t of the brush holding case 22 are in a relation expressed by the following equation (I) . On the other hand, the length L3 of the erecting portion 31, the length Ll of the flexible mounting portion 311 and the length L2 of the solid lead 312 are in a relation expressed by the following equation (II). Namely, the relation expressed by the following equation (II) means that the length of the upper solid lead 313 is larger than zero at all times. Ll ^ t (I) L3 > Ll + L2 (II) Then, the meaning of the equation (I) and the equation (II) will be hereinafter described. First, with respect to the equation (I)/ as mentioned above, wire size of the part of the solid lead 312 to which stiffening treatment, particularly welding treatment has been applied, becomes smaller. There may be disconnection of thin copper wire due to generation of a large tensile force in the thin copper wire of the flexible mounting portion 311 or reduction in cross-sectional area of the flexible mounting portion 311 due to stretch of the thin copper wire. When the diameter of the flexible mounting portion 311 having reduced cross-sectional area becomes smaller than the width L4 (see Fig. 1) of the stopper 26 on the opening 25 formed on the upper surface of the brush holding case 22, there arises a problem that the erecting portion 31 externally gets out of the opening 25 climbing over the stopper 26. To cope with this problem, by establishing Ll^t, the reduction in the outer diameter of the flexible mounting portion 311, the resulting climbing over the stopper 26, the disconnection of the conductive wire, etc. are entirely prevented. Then, the equation (II) is hereinafter described. Fig. 4 is a comparative example of Embodiment 1 that corresponds to the arrangement shown in Fig. 2. A solid lead 36 in Fig. 4 is an example of the solid lead that includes excessively long stiffening-treated region. The solid lead 36 extends to most part of the bending portion 32, hence the solid lead 36 differs from the arrangement sown in Fig. 2 . If the stiffening-treated region is excessively long as the solid lead 36, the solid lead 36 may be bent and deformed by the external force applied during assembling of the electric motor, and the brush 21 may be pressed on the side face of the brush holding case 22, and because of such deformation, slidability of the brush 21 in the brush holding case 22 may sometimes be deteriorated. On the contrary, when establishing the relation expressed by the mentioned equation (II) wherein the sum of LI and L2 is less thanL3, the mentioned deformation or dislocation may not occur, and the slidability of the brush 21 can be kept good. In this Embodiment 1, it is preferable that the lead wire 3 shall be as short as possible in view of restrictive space of location and cost. It is preferable that length L2 of the solid lead 312 is a value of more or less 2 mm. Although the cross sectional shape of the solid lead 312 is described to be rectangular in the foregoing Embodiment 1, the cross-sectional shape may be circular, elliptical, trapezoidal or square other than rectangular on condition that the erecting portion 31 of the lead wire 3 has enough rigidity. The cross-sectional shape may be any shape such as ellipse, trapezoid or the like giving an orientation to the rigidity of the solid lead. Furthermore, the orientation may be arbitrary. Embodiment 2 . Fig. 5 is a schematic view to explain Embodiment 2 showing another example of the connection between the brush 21 and the lead wire 3, in which the tail portion 33 of the lead wire 3 extends behind the brush 21. Further, a stiffening treatment is applied to an end 34 of the lead wire 3 for welding the lead wire 3 to the electrode plate 4 (not shown) so that the cross-sectional shape may be rectangular by welding. In this process, when applying the stiffening treatment in such a manner that the solid lead 312 is formed into the same cross-sectional shape as that of the end 34, there is an advantage such that the end 34 and the solid lead can be stiffening-treated in the same manner as one another. As a result, it becomes possible to reduce man-hour and cost in the manufacturing process. Embodiment 3 . Figs. 6 and 7 are to explain Embodiment 3 according to the invention, and in which Fig. 6 is an enlarged sectional view of a part taken along the line Y-Y in Fig. 1, and Fig. 7 is an enlarged side view of the brush holding case and the neighborhood thereof. In Figs. 6 to 7, reference numeral 312 designates a solid lead of the erecting portion 31 in the lead wire 3. The stiffening treatment is applied to the solid lead 312 with an adhesive so that the shape of the lead wire 3 can be almost steadily held keeping the predetermined shape. As far as each length of the flexible mounting portion 311, the solid lead 312 and an upper lead 313 is concerned/ the foregoing description about Embodiment 1 likewise applies to this Embodiment 3. Embodiment 4 . Figs . 8 to 10 are to show Embodiment 4 according to the invention, and in which Fig. 8 is an enlarged sectional view of a part taken along the line Y-Y in Fig. 1, and Fig. 9 is an enlarged side view of the brush holding case and the neighborhood thereof. In Figs. 8 to 10, reference numeral 312 designates a solid lead of the erecting portion 31 in the lead wire 3 and numeral 35 designates a bush. Fig. 10 is a perspective view of the bush. A stiffening treatment is applied to the solid lead 312 by caulking with the bush 35 so that the shape of the lead wire 3 can be almost steadily held keeping the predetermined shape. As far as each length of the flexible mounting portion 311, the solid lead 312 and the upper lead 313 is concerned, the foregoing description about Embodiment 1 likewise applies to this Embodiment 4. Embodiment 5 . Figs. 11 and 12 are to explain Embodiment 5 according to the invention, and in which Fig. 11 is a transverse sectional view of an electric motor, and Fig. 12 is a plan view of a brush holder used in the electric motor. As shown in Figs. 11 to 12, in this Embodiment 5, the tail portion 33 of the lead wire 3 is pulled out in the same direction as the sliding direction A of the brush 21, and the stiffening treatment is applied partially to the erecting portion 31 of the lead wire 3 in the same manner as in the foregoing Embodiments 1 to 4. As a result of applying such stiffening treatment, there arises an advantage such that deformation resistant characteristic of the lead wire 3 against various external forces is superior in the same manner as in the foregoing Embodiments 1 to 4. At the same time, there is another advantage such that influence on the contact condition between the brush 21 and a commutator 12 under the external force applied to the lead wire 3 is further reduced, as compared with the foregoing Embodiment 1 and others in which the tail portion 33 is pulled out in the direction of side surface of the brush 21. WE CLAIM : 1. A brushed motor characterized in that solid leads each formed by connecting a lead wire composed of a bundle of a plurality of conductive filaments are connected to a brush, and a stiffening treatment is applied to the bundle of said conductive filaments in the neighborhood of a connecting end of the lead wire connected to said brush. 2. The brushed motor as claimed in claim 1, wherein said lead wire has an erecting portion erecting from a lead wire connection on the surface of the brush to which said lead wire is connected and extending in parallel or almost in parallel to a rotating shaft of the electric motor, and at least a part of said erecting portion is provided with a solid lead. 3. The brushed motor as claimed in claim 1, wherein said erecting portion is a flexible mounting portion wherein stiffening treatment is not applied to a root portion thereof, said flexible mounting portion having a length LI from the lead wire connection on the surface of the brush, and said length LI satisfying a following equation: LI > t where: t is a wall thickness of a brush holding case for holding said brush. 4. The brushed motor as claimed in claim 2, wherein said erecting portion has a bending portion cascade-connected to said erecting portion and wherein a length L3 of said erecting portion erecting from the lead wire connection on the surface of the brush to said bending portion satisfies a following equation: L3 > LI + L2 where: LI is a length of the flexible mounting portion and L2 is a length of the solid lead. 5. The brushed motor as claimed in claim 2, wherein, in sectional shape of the erecting portion of the solid lead in a direction orthogonal to a longitudinal direction, a side orthogonal to a sliding direction of the brush in the brush holding case is longer than the other side parallel to the sliding direction. 6. The brushed motor as claimed in claim 2, wherein, in sectional shape of the erecting portion of the solid lead in a direction orthogonal to a longitudinal direction, a side parallel to a sliding direction of the brush in the brush holding case is longer than the other side orthogonal to the sliding direction. 7. The brushed motor as claimed in claim 1, wherein the stiffening treatment is applied by welding or soldering conductive filaments forming the lead wire to each other. 8. The brushed motor as claimed in claim 1, wherein the stiffening treatment is applied by joining conductive filaments forming a lead wire with an adhesive. 9. The brushed motor as claimed in claim 1, wherein the stiffening treatment is applied by caulking the lead wire with a bush. 10. The brushed motor as claimed in claim 1, wherein the lead wire has an erecting portion, a bending portion and a tail portion cascade-connected to the bending portion, said tail portion extending in the direction orthogonal to the sliding direction of the brush in a brush holding case or in the sliding direction of the bush, and extending behind the mentioned brush. 11. A brushed motor substantially as herein described with reference to Figures 1 to 12 of the accompanying drawings.

Documents:

1034-mas-2001 abstract-granded.pdf

1034-mas-2001 claims-granded.pdf

1034-mas-2001 description (complete)-granded.pdf

1034-mas-2001 drawings-granded.pdf

1034-mas-2001-abstract.pdf

1034-mas-2001-claims.pdf

1034-mas-2001-correspondence others.pdf

1034-mas-2001-correspondence po.pdf

1034-mas-2001-description complete.pdf

1034-mas-2001-drawings.pdf

1034-mas-2001-form 1.pdf

1034-mas-2001-form 26.pdf

1034-mas-2001-form 3.pdf

1034-mas-2001-form 5.pdf

1034-mas-2001-other documents.pdf