Title of Invention

A CONTROL UNIT COMPRISING AT LEAST TWO HOUSING PARTS

Abstract

A Control unit comprising at least two housing parts Abstract In a control unit, the printed circuit board (10) bears on an edge (28) of the housing base (26) . The power components (14) to be cooled are arranged in the region where the printed circuit board (10) bears on the edge (28) . In order to achieve uniform pressing of the printed circuit board (10) over the entire bearing face, addi¬tional auxiliary means are used to generate a contact pressure on the power component (14) or on the printed circuit board (10). In this case, it is possible to use elastomer strips (31) or spring elements (30) acting on the power components (14). Furthermore, multi-part supporting elements (40) or plastic parts (45), which in each case act directly on the printed circuit board (10), can also be used. This enables good heat transfer away from the power component (14) via the edge (28) of the housing base (26).

Full Text

Control unit comprising at least two housing parts Prior art The invention is based on a control unit compris¬ing at least two housing parts of the generic type of the independent claims. In the case of a control unit dis¬closed in DE-U 92 00S 24.8, a printed circuit board is fixedly inserted between two housing parts, that is to say a housing cover and a housing base, with the aid of screw joints. The housing cover and the housing base are produced from readily thermally conductive material. In order to be able to dissipate the heat loss of the power components arranged on the printed circuit board via the housing parts, the printed circuit board is provided with a thermally conductive layer, for example a copper coating or a thermally conductive layer. However, new types of power components, in particular, have a very high power loss, which can be outwardly dissipated only with great difficulty with the aid of the conventional thermally conductive layer and the previous structural set-up. In the case of other control unit designs, the underside of the substrate carrying the power components is completely provided with a heat-dissipating layer for the purpose of heat dissipation. As a result, this side of the printed circuit board can no longer be populated with power components, which results in an increased area requirement and, consequently, a high development of costs. Advantages of the invention In contrast, the control unit according to the invention, having the characterizing features of the main claim, has the advantage that there is a relatively low thermal contact resistance between the printed circuit board and the bearing face, serving as heat sink, of the housing base. A contact pressure of the printed circuit board on the heat sink can be generated in a simple and cost-effective manner by means of the mechanical auxiliary means. If appropriate, a thermally conductive adhesive can also be provided between the bearing face of the housing base and the underside of the printed circuit board, as a result of which the thermal conductivity is again optimized. The contact pressure can be generated by simple structural measures, which enables the unit to be produced at very favourable costs. A restriction to specific printed circuit boards is not necessary. Furthermore, population with components on both sides in a simple manner except for the region where the printed circuit board bears on the housing part is also possible. Accordingly, the present invention provides a control unit, comprising at least two housing parts and at least one printed circuit board populated with power components, the printed circuit board at least partially having a layer of thermally conductive material, characterized in that the printed circuit board bears on at least one of the housing parts with a region which is larger than or the same size as the bearing face of at least one power component to be cooled, in that there is a mechanical auxiliary means between at least one power component to be cooled and the first housing part, with the result that uniform bearing of the second housing part, at least in the region of the power component to be cooled, indirectly or directly on the printed circuit board is possible. Further advantages and advantageous developments emerge from the description and from the drawing. Drawing Exemplary embodiments of the invention are illustrated in the drawing and are explained in more detail in the following description. Figures I to 5 each show a section through a diagrammatic illustration of part of a control unit. Description of the exemplary embodiments The electrical switching or control unit has a printed circuit board 10, on the top side 11 of which an electronic circuit is constructed of which only a few electronic components 14, which give off a heat loss during operation, are illustrated. These components 14 are embodied as SMD components (Surface Mounted Device) in the drawing. In a manner which is not illustrated, the printed circuit board 10 is connected in a conventional manner to a connector strip. The top side 11 of the printed circuit board 10 is covered by a trough- shaped housing cover 18. Except for the region of the connector strip, the housing cover 18 has a continuous edge 22 in the form of a collar on its housing walls 21. In this case, the printed circuit board 10 can, as illustrated in Figure 1, extend approxi¬mately as far as the side wall 21. The components 14 can consequently be arranged right up to the edge of the printed circuit board 10. On the other hand, it is also possible to keep the edge of the printed circuit board 10 free from circuit components and conductor tracks, with the result that this edge of the printed circuit board 10 projects to a point under the edge 22 of the housing cover 18. The continuous edge 22 has an angular border 23 which runs approximately perpendicularly to the edge 22 ' and projects right over the end of the printed circuit board 10. The underside 25 of the printed circuit board 10 is surrounded by a likewise trough-shaped housing base 26, the side walls 27 of which have a continuous edge 28 in the form of a collar which bears indirectly or directly on the outer region of the underside 25 of the printed circuit board 10. The power components 14 whose heat must be dissipated preferably also bear on the printed circuit board 10 in this edge region 28. In Figure 1, the edge 28 terminates approximately flush with the border 23 of the housing cover 18, with the result that the printed circuit board 10 is enclosed with the aid of a sealing ring 29 between the housing cover 18 and the housing base 26, that is to say between the edge 22 of the housing cover 18 and the edge 28 of the housing base 26. The housing cover 18 and the housing base 26 are fastened, for example, by means of a plurality of screws arranged at the corners of the housing. Instead of the aforementioned screw joint, however, the housing parts can also be fixedly connected to one another by bonding, soldering, flanging, riveting, and by means of latching elements or other connection techniques. The housing cover 18 and the housing base 26 are preferably produced from a readily thermally conductive material. It is important here that the bearing face of the housing base 26, that is to say of the edge 28 on the printed circuit board 10, is large enough to enable at least the power components 14 having the highest heat loss to be arranged on the superior side of the printed circuit board 10. This enables direct heat dissipation from the power component 14 through the printed circuit board 10 to the edge 28 of the housing base 26 and thus into the open. In order to achieve good thermal conductivity, the printed circuit board 10 is connected with the aid of a contact adhesive having thermally conductive properties. In order to join or fix the printed circuit board 10 on the edge 28 of the housing cover 26 during assembly of the control unit, this contact adhesive also has adhesive-bonding properties. If the printed circuit board 10 is now fixedly clamped in between the housing cover 18 and the housing base 26 with the aid of the screw joints that are not illustrated, then it is possible, on account of the screw j oints which can be provided only at the edge, for a wedge-shaped gap to form between the edge 28 and the underside 25 of the printed circuit board 10. This wedge-shaped gap becomes larger and larger starting from the outer end of the edge 28, that is to say seen from the border 23, in the direction of the interior of the housing. Even if there is only minimal gap formation here, in the process varying thermal dissipation, that is to say a varying thermal leakage resistance, is produced over the entire bearing face of the printed circuit board 10 on the edge 28. The larger this gap is, the poorer is the heat dissipation from the power components 14 to the housing parts 18 and 26. This varying thermal dissipation can have an adverse effect on the functionality of the power components 14. For this reason, it may be necessary to press the printed circuit board, that is to say indirectly the power components 14, uniformly onto the edge 28 of the housing base 26. For this purpose, a contact pressure on the power components or on the printed circuit board 10 is generated with additional mechanical auxiliary means. However, when these mechanical auxiliary means are used, it is also necessary to take account of optimization of the costs incurred as a result. In Figure 1, then, an additional spring element 30 is used to press the power component 14 onto the printed circuit board 10 and the latter in turn uniformly onto the edge 28. The contact pressure of the spring element 30 in this case acts directly on the relevant power component 14 and consequently ensures a uniform bearing face of the edge 28 on the printed circuit board 10. The spring element 30 rests, on the one hand, as men¬tioned, on the power component 14 and, on the other hand, on the inner side of the housing cover 18. This spring element 30 may, for example, be riveted to the inner side of the housing cover 18. In order to permit simple assembly, the intention is for as far as possible only a small number of spring elements 30, that is to say in the optimum case just one spring element 30, to press against the power component 14. In order, furthermore, to achieve uniform distribution of the contact pressure, the spring element 30 should bear centrally on the power component 14. If it is intended to press individually against an individual power component 14, then the spring element 30 should bear approximately centrally on the power component 14. However, if a plurality of power components 14 are arranged in a line one behind the other on the edge of the printed circuit board 10, then it is possible to work with an elongate subdivided spring element which comes to bear approximately centrally over the power components 14. The design of the control unit according to Figure 2 corresponds to that of Figure 1. Figure 2 illustrates a modification of the mechanical auxiliary means for pressing against the power component 14. In Figure 2, an elastic component made of plastic is used as the auxiliary means. Figure 2 illustrates this as an elastomer strip 31. This elastomer strip 31 may have a circular, rectangular or any other cross-section, which achieves a uniform contact pressure on the power component 14. The elastomer strip 31 can in this case be bonded to the inner side of the housing cover 18, with the result that it bears approximately centrally an the power components 14 after assembly. In the exemplary embodiment according to Figure 3, the printed circuit board 10 is clamped in with the aid of a bead 35 formed in the housing cover 18 between the side wall 21 and the edge 22. The printed circuit board 10 is thereby clamped between the housing cover 18 and the housing base 26. In the exemplary embodiments accord¬ing to Figures 3 and 4, the printed circuit board 10 is pressed directly on the edge 2 8 of the housing base 2 6 without having a contact pressure act on the power components 14. For this purpose, there is an additional supporting element on. that end of the power component 14 which faces away from the edge 21. In Figure 3, this supporting element is designed as a mechanical post 40. A first post part 41 is in this case arranged between the inner side of the housing cover 18 and the printed circuit board 10 and a second post part 42 is arranged between the inner side of the housing base 26 and the underside of the printed circuit board 10. The height of the second post part 42 is in this case to be matched to the height of the side wall 27 of the housing base 26. The same applies to the first housing part 41, which is to be matched to the height of the side wall 21. In order to achieve a uniform contact pressure, a plurality of supporting elements 40 are arranged such that they are distributed uniformly over the printed circuit board. However, these supporting elements 40 are situated as close as possible to the edge 28. This design is particu¬larly advantageous in the case of cast housing parts, since as early as during the casting operation, the first and second supporting parts 41, 42 can be concomitantly cast on the housing cover 18 and on the housing base 26, respectively. If the intention is to design the supporting elements once again as an elastic plastic part, then it has, as illustrated in Figure 4, a hat-shaped or arcuate configuration. The plastic part 45 in this case presses the printed circuit board 10 onto the edge 28. Further¬more, it bears with as large an area as possible against the inner wall of the housing cover 18. To fix the plastic part 45, there are holes 46 in the printed circuit board 10. In the exemplary embodiment according to Figures 5 and 5a the mechanical auxiliary means 50 is arranged between the printed circuit board 10 and the housing cover 18 and the housing base 26. In this case/ the auxiliary means 50 does not act on the power components 14. The auxiliary means 50 consists of a bottom part 51, which is situated between the printed circuit board 10 and the housing base 26, and of an abutment 52, which is arranged between the printed circuit board 10 and the housing cover 18. As is evident from Figure 5a, the auxiliary means 50 is arranged such that it bears approx¬imately centrally on the printed circuit board 10. It is also possible to form the auxiliary means only on one side, so that only a bottom part or an abutment is present. The auxiliary means may be an additionally inserted part or be formed on the inner side of the housing base 26 or of the housing cover 18. The auxiliary means can be fitted in a screwed manner, in a latched manner or bearing in a planar manner. The auxiliary means illustrated in Figure 5 is possible both in the design of the control unit according to Figures 1 and 2 and in the design of the control unit according to Figures 3 and 4. The auxiliary means can be arranged in addition to the means shown in these exemplary embodiments or can replace these means. WE CLAIM: 1. A control unit, comprising at least two housing parts (i 8, 26} and at least one printed circuit board (10) populated with power components (14), the printed circuit board (10) at least partially having a layer of thermally conductive material, characterized in that the printed circuit board (10) bears on at least one of the housing parts (26) with a region (28) which is larger than or the same size as the bearing face of at least one power component (14) to be cooled, in that there is a mechanical auxiliary means (30) between at least one power component (14) to be cooled and the first housing part (18), with the result that uniform bearing of the second housing part (26), at least in the region (28) of the power component (14) to be cooled, indirectly or directly on the printed circuit board (10) is possible. 2. A control unit, comprising at least two housing parts (18, 26) and at least one printed circuit board (10) populated with power components (14), the printed circuit board (10) at least partially having a layer of thermally conductive material, characterized in that the printed circuit board (10) bears on at least one of the housing parts (26) with a region (28) which is larger than or the same size as the bearing face of at least one power component (14) to be cooled, in that the printed circuit board (10) is clamped in between the first and the second housing part (18, 26), and in that there is a mechanical auxiliary means (40, 45) between the printed circuit board (10) and at least one housing part, with the result that uniform bearing of the region (28) of the second housing part (26) indirectly or directly on the printed circuit board (10) is possible. 3. A control unit, comprising at least two housing parts (18, 26) and at least one printed circuit board (10) populated with power components (14). the printed circuit board (10) at least partially having a layer of thermally conductive material, characterized in that the printed circuit board (10) bears on at least one of the housing parts (26) with a region (28) which is larger than or the same size as the bearing face of at least one power component (14) to be cooled, in that a mechanical auxiliary means (50) is arranged between the printed circuit board (10) and the second housing part (26) or the first housing part (18), with the result that uniform bearing of the region (28) of the second housing part (26) indirectly or directly on the printed circuit board (10) is possible. 4. The control unit as claimed in claim 3. wherein there is an abutment (52) between the printed circuit board (10) and the second housing part (26) or the first housing part (18). 5. The control unit as claimed in claim 3 or 4, wherein the auxiliary means (50) is arranged centrally on the printed circuit board (10). 6 . The control unit as claimed in any one of claims I to 5, wherein the auxiliary means is a spring element (30). 7. The control unit as claimed in any one of claims 1 to 5, wherein the auxiliary means is a plastic element. 8. The control unit as claimed in any one of claims 1 to 5, wherein the auxiliary means is an elastomer strip. 9. The control unit as claimed in anv one of claims 1 to 5, wherein the auxiliary means is an extension (40) which projects from the inner side of the first housing part (18) to the printed circuit board (10). 10. The control unit as claimed in claim 9, wherein there is an abutment (42) on that side of the printed circuit board (10) which faces the second housing part (26). 11. The control unit as claimed in claim 10, wherein the abutment is an extension (42) on the second housing part (26). 12. The control unit as claimed in any of claims 1 to 11, wherein the auxiliary means is aplastic part of pot-shaped design. 13. A controi unit, comprising at least two housing parts, substantially as herein described with reference to the accompanying drawings.

Documents:

054-mas-1997 abstract-duplicate.pdf

054-mas-1997 abstract.pdf

054-mas-1997 claims-duplicate.pdf

054-mas-1997 claims.pdf

054-mas-1997 correspondence-others.pdf

054-mas-1997 correspondence-po.pdf

054-mas-1997 description (complete)-duplicate.pdf

054-mas-1997 description (complete).pdf

054-mas-1997 drawings-duplicate.pdf

054-mas-1997 drawings.pdf

054-mas-1997 form-1.pdf

054-mas-1997 form-26.pdf

054-mas-1997 form-4.pdf

054-mas-1997 others.pdf

054-mas-1997 pct.pdf

054-mas-1997 petition.pdf