JP2015109386A - Electronic control unit and electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic control unit which effectively radiates heat of a heating component without increasing components, and to provide an electric power steering device including the electronic control unit.SOLUTION: In an electronic control unit, heat radiation parts 41, 51 which contact with an FET 31 to radiate heat of the FET 31 and correction parts 42, 52 which correct warpage of a circuit board 30 are provided at a housing (an ECU base 40, a plate 50) for housing the circuit board 30 on which the FET 31 serving as a heater element is surface-mounted. The heat radiation parts 41, 51 are placed in contact with the FET 31 through a TIM 34 that is a conductive member and insulation layers 41b, 51b. The correction parts 42, 52 press the circuit board 30 in a thickness direction through insulation layers 42b, 52b.

Description

  The present invention relates to an electronic control unit and an electric power steering apparatus including the same.

  The electric power steering apparatus includes an electronic control unit (ECU) that controls driving of the electric motor based on detection signals of various sensors such as a torque sensor. The electronic control unit includes a circuit board on which a power semiconductor element (for example, MOSFET) is mounted, a housing that houses the circuit board, and the like. However, the power semiconductor element generates heat at a high temperature when energized. It is necessary to take heat countermeasures to dissipate the heat generated from the element to the outside of the housing.

  As a method for dissipating the heat generated by the heating element to the outside, for example, there is a technique described in Patent Document 1. This technology dissipates the heat of the heating element to the outside by a heat sink. Between the circuit board on which the heating element is mounted and the heat sink, an electrical insulating layer and a heat transfer metal formed thereon are provided. A heat transfer substrate having a foil layer is interposed. Here, the circuit board and the metal foil layer of the heat transfer board are joined by solder.

  As another method, for example, there is a technique described in Patent Document 2. In this technology, a heat sink is closely attached to the side opposite to the heating element mounting portion of the circuit board and the side opposite to the circuit board of the heating element, and the heat of the heating element is transferred to the board surface side and the opposite side of the heating element. The heat is dissipated from both sides.

JP 2011-165867 A JP 2010-245174 A

However, the technique described in Patent Document 1 requires a heat transfer board interposed between the circuit board and the heat sink, resulting in an increase in the number of components. Furthermore, since the heat transfer board is joined to the circuit board by soldering, the number of assembly steps increases.
Moreover, in the technique of the said patent document 2, although it is the structure which closely_contact | adheres a heat sink to a circuit board, when a circuit board warps, adhesive force will change and heat dissipation will deteriorate.
Therefore, an object of the present invention is to provide an electronic control unit that can effectively dissipate the heat of the heating element without increasing the number of components, and an electric power steering apparatus including the electronic control unit.

  In order to solve the above problems, one aspect of an electronic control unit according to the present invention includes a circuit board on which an electronic component including a heating element is surface-mounted, a metal base, and a metal cover. A housing for holding the circuit board by sandwiching and fixing the peripheral edge of the board in the thickness direction. Then, at least one of the base and the cover is directly or indirectly sandwiching the circuit board between the heating element and a position facing the heating element directly or across the circuit board via a heat conductive member and an insulating layer. A heat dissipating part is provided. Further, the base and the cover include a correction portion that presses the circuit board in the thickness direction through the insulating layer so as to correct the warp of the circuit board.

  In this way, the heat radiating portion is formed in the housing, and the heat is radiated from the heat generating element by bringing it into close contact with the surface of the heat generating element or the circuit board opposite to the heat generating element mounting portion. At this time, the warp of the circuit board is corrected by the correction portion formed in the housing, and unevenness in the close contact between the heating element and the heat conductive member is prevented. Thereby, heat dissipation can be stabilized. Furthermore, since the insulating layer is provided between the heat generating element and the circuit board and the heat radiating part, and between the heat generating element and the circuit board and the correcting part, it is possible to ensure insulation. Therefore, even if the heat radiating part or the correcting part is in contact with the heat generating element or the circuit board, an electric short circuit does not occur and a stable operation can be maintained.

Moreover, in the above, it is preferable to provide an elastic member between the circuit board and the correction part. Thereby, a circuit board can be appropriately pressed by the correction part, and the curvature of a circuit board can be corrected effectively.
Furthermore, in the above, it is preferable that the elastic member includes a heat conductive material. As a result, the elastic member between the circuit board and the correction portion can have a heat dissipation function.

In the above, the insulating layer is preferably formed on the base and the cover. Thus, by forming the insulating layer on the housing side by surface treatment, the electronic control unit can be easily assembled with the insulating layer interposed.
Furthermore, in the above, it is preferable that the heat conductive member includes an insulating material. Thereby, the heat conductive member between the heat generating element and the circuit board and the heat radiating portion can be provided with an insulating function.

  According to another aspect of the present invention, there is provided an electric power steering apparatus that includes a torque detection unit that detects a steering torque transmitted from a steering wheel, and an electric motor that generates a steering assist torque according to the steering torque detected by the torque detection unit. A motor, and any one of the electronic control units that controls driving of the electric motor. As described above, since the electronic control unit having both heat dissipation and insulation properties is provided, the electric motor can be stably operated, and appropriate steering assist control can be performed.

  In the electronic control unit of the present invention, since the heat radiating portion and the correction portion are formed in the housing that houses the circuit board on which the heating element is mounted, the warp of the circuit board is corrected effectively without increasing the number of components. Heat generated by the heating element can be dissipated. In addition, since the insulating layer is provided between the heat generating element and the circuit board and the heat radiating portion, and between the circuit board and the correction portion, it is possible to ensure insulation in addition to the heat radiating property.

It is a figure which shows the basic structure of the electric power steering apparatus by which the electronic control unit of this embodiment is mounted. It is a figure which shows the structure of a controller. It is a disassembled perspective view of an electronic control unit. It is a disassembled perspective view of an electronic control unit. It is a figure which shows the assembly state of an electronic control unit. It is a figure which shows sectional drawing of an electronic control unit. It is sectional drawing of a thermal radiation part. It is sectional drawing of a correction part. It is sectional drawing which shows another example of a correction part. It is a figure which shows another example of an elastic member.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a basic structure of an electric power steering apparatus on which the electronic control unit of this embodiment is mounted.
In the figure, reference numeral 1 denotes a steering wheel, and the steering force applied to the steering wheel 1 from the driver is transmitted to the steering shaft 2. The steering force transmitted to the steering wheel 1 is transmitted to the tie rod 6 via the reduction gear 3, the universal joints 4A and 4B, and the pinion rack mechanism 5, and steers steered wheels (not shown).

The steering shaft 2 is provided with a torque sensor 7 that detects a steering torque Ts that is applied to the steering wheel 1 and transmitted to the steering shaft 2. The reduction gear 3 is connected to an electric motor 8 that generates a steering assist force for the steering system. Here, the electric motor 8 is a three-phase brushless motor.
Electric power is supplied to the controller 10 from a battery (not shown), and an ignition key signal IGN (see FIG. 2) is input via an ignition key (not shown). The controller 10 calculates a steering assist command value based on the steering torque Ts detected by the torque sensor 7 and the vehicle speed V detected by the vehicle speed sensor 9, and supplies the steering assist command value to the electric motor 8 based on the calculated steering assist command value. Control the current.

The controller 10 is mainly composed of a microcomputer, and its configuration is as shown in FIG. The controller 10 includes a control arithmetic device 11, a gate drive circuit 12, a motor drive unit 13, and a cutoff device 14.
In addition to the steering torque Ts and the vehicle speed V, the control arithmetic unit 11 calculates the three-phase motor currents ia to ic detected by the current detection circuit 15 and the rotational position θ of the electric motor 8 detected by the rotor position detection circuit 17. Based on these, the current command value of the electric motor 8 is calculated based on these. The control arithmetic device 11 outputs the calculated current command value to the gate drive circuit 12.

Here, a rotation sensor 16 such as a Hall sensor is attached to the electric motor 8, and the rotor position detection circuit 17 detects the rotation position θ based on the rotation signal RT from the rotation sensor 16. Yes.
The ignition signal IGN from the ignition key is input to the ignition voltage monitor unit 18 and the power supply circuit unit 19, and the power supply voltage Vdd and the reset signal RS for stopping the device are input from the power supply circuit unit 19 to the control arithmetic unit 11. It has come to be.

  The gate drive circuit 12 forms a gate drive signal based on the input current command value and the like, and outputs it to the motor drive unit 13 having a FET bridge configuration. The motor drive unit 13 is an inverter circuit including FETs Tr1 to Tr6 that are power semiconductor elements. The motor drive unit 13 drives the electric motor 8 via an emergency stop interrupting device 14. Here, the interruption | blocking apparatus 14 is comprised by the relay contacts 141 and 142 which interrupt | block two phases.

Here, the breaking device 14 is configured to use a contact-type relay, but a semiconductor-type relay can be used instead. In this case, a semiconductor relay is inserted in each phase of the electric motor 8.
3 and 4 are exploded perspective views of an electronic control unit (ECU) constituting the controller 10.

The electronic control unit 20 includes a circuit board 30 on which FETs Tr1 to Tr6 and the like constituting the motor drive unit 13 are mounted, and an ECU housing (ECU base 40 and plate (cover) 50) that accommodates the circuit board 30.
The circuit board 30 is made of resin with FR-4 or the like as a base material, and a FET 31 that is a heating element is mounted on the surface of the circuit board 30 by solder. Here, the FET 31 is a FET Tr1 to Tr6 for driving a motor, a relay FET when a semiconductor relay is used as the interrupting device 14, or the like.

  Further, an elastic member 32 is fixed to a portion of the circuit board 30 where the FET 31 is not mounted by an adhesive member such as a bond or a double-sided tape. The elastic member 32 is fixed to both sides of the circuit board 30 at positions facing each other with the circuit board 30 interposed therebetween. Furthermore, a plurality of through holes 33 into which mounting screws 60 (see FIG. 5) for attaching the circuit board 30 to the ECU base 40 are screwed are formed in the peripheral portion of the circuit board 30.

The ECU base 40 is a box-shaped member having an opening, and the circuit board 30 can be attached to the opening. The ECU base 40 is formed by, for example, aluminum die casting.
At the bottom of the ECU base 40, a heat radiating part 41 protruding toward the opening is formed at a position facing the FET 31 directly or via the circuit board 30 with the circuit board 30 attached. The heat dissipating part 41 includes a heat dissipating surface 41 a that is a plane parallel to the circuit board 30 at the end on the circuit board 30 side.

In addition, a correction portion 42 that protrudes toward the opening is formed at the bottom of the ECU base 40 at a position facing the elastic member 32 with the circuit board 30 attached. The correction unit 42 includes a correction surface 42 a that is a plane parallel to the circuit board 30 at the end on the circuit board 30 side.
An insulating layer is formed on each of the heat radiation surface 41a and the correction surface 42a. The insulating layer is formed by alumite treatment or fluorine coating.

Further, a screw hole 43 into which the mounting screw 60 is screwed is formed at a peripheral portion of the ECU base 40 at a position corresponding to the through hole 33 of the circuit board 30.
The plate 50 is a plate-like metallic member that is fixed to the ECU base 40 so as to close the opening of the ECU base 40. The plate 50 is provided with a heat radiating portion 51 protruding toward the circuit board 30 at a position facing the FET 31 directly or via the circuit board 30 in a state of being fixed to the ECU base 40 to which the circuit board 30 is attached. Yes. The heat dissipating part 51 includes a heat dissipating surface 51 a that is a plane parallel to the circuit board 30 at the end on the circuit board 30 side.

The plate 50 is formed with a correction portion 52 that protrudes toward the circuit board 30 at a position facing the elastic member 32 in a state of being fixed to the ECU base 40 to which the circuit board 30 is attached. The correction unit 52 includes a correction surface 52 a that is a plane parallel to the circuit board 30 at the end on the circuit board 30 side.
An insulating layer is formed on each of the heat radiation surface 51a and the correction surface 52a. The insulating layer is formed by alumite treatment or fluorine coating.

Further, a through hole 53 into which the mounting screw 60 is screwed is formed at a peripheral portion of the plate 50 at a position corresponding to the screw hole of the ECU base 40.
Then, the electronic control unit 20 is completed by attaching the plate 50 from above the circuit board 30 to the ECU base 40 to which the circuit board 30 is attached, and fixing with the attachment screw 60 as shown in FIG.

6A and 6B are views showing the assembled state of the electronic control unit 20, wherein FIG. 6A is a front view, FIG. 6B is an AA cross-sectional view, and FIG. 6C is a BB cross-sectional view.
In the assembled state of the electronic control unit 20, as shown in FIG. 6B, the FET 31 mounted on the circuit board 30 includes a heat radiating surface 41 a formed on the ECU base 40 and a heat radiating surface 51 a formed on the plate 50. Therefore, the circuit board 30 is sandwiched from both sides in the thickness direction. At this time, a grease-like or sheet-like thermally conductive material (TIM) is interposed between the FET 31 and the heat dissipation part 41 and between the FET 31 and the heat dissipation part 51, respectively.

  That is, when the FET 31 is mounted on the upper surface of the circuit board 30 (the surface on the ECU base 40 side) as shown in FIG. The heat radiating surface 41a on which 41b is formed is brought into close contact via the TIM 34. Further, a heat radiating surface 51a on which an insulating layer 51b is formed is adhered to the surface of the circuit substrate 30 opposite to the FET 31 via the TIM 34.

Further, as shown in FIG. 6C, the portion where the FET 31 is not mounted on the circuit board 30 is an elastic member by a correction surface 42a formed on the ECU base 40 and a correction surface 52a formed on the plate 50. The circuit board 30 is sandwiched from both sides in the thickness direction via 32.
That is, as shown in the enlarged view of the β portion of FIG. 6C in FIG. 8, the elastic member 32 is fixed to the upper surface of the circuit board 30 (the surface on the ECU base 40 side) by the adhesive member 32a. The substrate 30 is pressed downward (on the plate 50 side) by the correction surface 42a on which the insulating layer 42b is formed via the elastic member 32.

Similarly, the elastic member 32a is attached to the lower surface (the surface on the plate 50 side) of the circuit board 30 at a position facing the elastic member 32 fixed to the upper surface of the circuit board 30 with the circuit board 30 interposed therebetween. 32 is fixed, and the circuit board 30 is pressed upward (ECU base 40 side) by the correction surface 52a on which the insulating layer 52b is formed via the elastic member 32.
Here, the pressing force of the correction units 42 and 52 against the circuit board 30 is set to such an extent that the warp of the circuit board 30 is corrected.

  As described above, a part of the peripheral edge of the circuit board 30 is sandwiched in the thickness direction by the ECU base 40 and the plate 50 constituting the ECU housing, and is fixed by the mounting screw 60. At this time, the heat radiation part 41 of the ECU base 40 and the heat radiation part 51 of the plate 50 sandwich the FET 31 and the circuit board 30 via the TIM 34 so that the heat of the FET 31 is radiated from both surfaces of the circuit board 30.

  That is, for example, as shown in FIG. 7, when the FET 31 is mounted on the upper surface of the circuit board 30 (the surface on the ECU base 40 side), the heat radiation portion 41 formed on the ECU base 40 is formed on the upper surface of the FET 31. The heat radiating surface 41 a is brought into close contact with the TIM 34. Thereby, the heat of the FET 31 can be released from the upper surface of the FET 31 to the ECU base 40 via the TIM 34.

At the same time, the heat radiation surface 51 a of the heat radiation portion 51 formed on the plate 50 is brought into close contact with the lower surface of the FET 31 (the surface opposite to the FET 31 mounting portion of the circuit board 30) via the TIM 34. As a result, heat from the FET 31 can be released from the lower surface of the circuit board 30 to the plate 50 via the TIM 34 simultaneously with heat radiation from the upper surface of the FET 31.
Thus, the heat of the FET 31 can be efficiently radiated from both sides of the FET 31.

Further, since the heat radiating portions 41 and 51 are formed in the ECU housing (ECU base 40 and plate 50) that accommodates the circuit board 30, there is no need to add new heat radiating components, and the number of components of the electronic control unit 20 can be increased. Can be prevented. Furthermore, since no solder joint or the like is required when realizing the heat dissipation mechanism, the number of assembly steps can be reduced.
Insulating layers 41b and 51b are formed on the surface of the heat radiating portion 41 of the ECU base 40 and the heat radiating portion 51 of the plate 50 on the circuit board 30 side, respectively. Therefore, even if the heat radiating portions 41 and 51 are in contact with the FET 31 or the circuit board 30, the operation can be maintained without causing an electrical short circuit.

  By the way, when the circuit board 30 is warped in the case where the heat dissipation surfaces 41a and 51a are in close contact with the circuit board 30 on which the FET 31 or the FET 31 is mounted and the heat radiation surfaces 41a and 51a are in close contact via the TIM 34 as in the present embodiment, Variations occur in the distances between the FET 31 and the circuit board 30 and the heat radiation surfaces 41a and 51a, and the adhesion between the FET 31 and the circuit board 30 and the heat radiation parts 41 and 51 changes.

  If the TIM 34 interposed between the FET 31 and the ECU base 40 and between the FET 31 and the plate 50 is too thick, the heat transfer effect cannot be exhibited, and the heat dissipation is deteriorated. On the other hand, if the thickness of the TIM 34 is too thin, the insulating properties deteriorate. Therefore, it is necessary to manage the intervals between the FET 31 and the ECU base 40 and between the FET 31 and the plate 50 within appropriate ranges.

  Therefore, in the present embodiment, the ECU base 40 and the plate 50 are provided with correction portions 42 and 52 that are opposed to each other with the circuit board 30 interposed therebetween, and the portions where the FET 31 of the circuit board 30 is not mounted by the correction portions 42 and 52. The warp of the circuit board 30 is corrected by pressing from both sides in the thickness direction. As a result, the thickness of the TIM 34 can be controlled to a predetermined thickness, unevenness in the close contact between the FET 31 and the circuit board 30 and the TIM 34 can be prevented, and stable heat dissipation can be realized. it can. At this time, since the correction portions 42 and 52 are disposed to face each other with the circuit board 30 in between, the warp of the circuit board 30 can be corrected appropriately.

Insulating layers 42b and 52b are also formed on the circuit board 30 side surfaces of the correction part 42 of the ECU base 40 and the correction part 52 of the plate 50, respectively. Therefore, even if the correction parts 42 and 52 are in contact with the FET 31 or the circuit board 30, the operation can be maintained without causing an electrical short circuit.
As described above, in this embodiment, by providing a correction mechanism that corrects the warp of the circuit board 30, the FET 31 and the circuit board 30 are sandwiched between the ECU base 40 and the plate 50, and heat is radiated from both sides of the FET 31. In the structure, the heat of the FET 31 can be released efficiently and stably. Further, since the insulating layer is formed on the ECU base 40 and the plate 50 on the side facing the circuit board 30, both heat dissipation and insulating properties can be achieved.

(Modification)
In the above embodiment, as a correction mechanism for correcting the warp of the circuit board 30, the circuit board 30 is sandwiched between the ECU base 40 (correction part 42) and the plate 50 (correction part 52) via the elastic member 32. As described above, as shown in FIG. 9, the circuit board 30 may be directly sandwiched between the ECU base 40 (correction unit 42) and the plate 50 (correction unit 52). Thereby, the correction mechanism of the circuit board 30 can be realized without adding the elastic member 32.

  Moreover, in the said embodiment, as shown to FIG.3 and FIG.4, although the case where the cross-sectional shape of the elastic member 32 was made circular was demonstrated, as shown to Fig.10 (a), a square may be sufficient. However, it may have a shape having a hole at the center. The elastic member 32 and the ECU base 40 or the plate 50 may have a fitting structure as shown in FIG. Further, the elastic member 32 may be a metal or metal + resin member, and may be fixed to the circuit board 30 by surface mounting.

Furthermore, in the said embodiment, although the correction surfaces 42a and 52a were formed in the correction | amendment parts 42 and 52 and the case where the curvature of the circuit board 30 was corrected by surface contact was demonstrated, point contact and line contact may be sufficient. .
Moreover, in the said embodiment, the elastic member 32 can be made into the elastic member (elastic TIM) containing a heat conductive material, and can also have a heat dissipation function.

Furthermore, in the above-described embodiment, the case where the insulating layers of the ECU base 40 and the plate 50 are formed only on the heat radiating surfaces 41a and 51a and the correction surfaces 42a and 52a has been described, but the ECU base 40 and the plate 50 are entirely formed. It may be formed.
Moreover, in the said embodiment, an insulation auxiliary material is added to TIM34 as a heat conductive material interposed between the circuit board 30 and the thermal radiation part 41 and between the circuit board 30 and the thermal radiation part 51. It may be. Thereby, heat dissipation and insulation can be realized more effectively.

Further, in the above-described embodiment, the case where the correction unit 42 of the ECU base 40 and the correction unit 52 of the plate 50 are disposed to face each other with the circuit board 30 interposed therebetween is described. Not necessarily.
Moreover, in the said embodiment, although the case where the thermal radiation parts 41 and 51 were formed in both ECU base 40 and the plate 50 was demonstrated, only any one may be sufficient.

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Reduction gear, 4A, 4B ... Universal joint, 5 ... Pinion rack mechanism, 6 ... Tight rod, 7 ... Torque sensor, 8 ... Electric motor, 9 ... Vehicle speed sensor, 10 ... Controller 11 control controller 12 gate drive circuit 13 motor drive unit 14 interrupting device 15 current detection circuit 16 rotation sensor 17 rotor position detection circuit 18 IGN voltage monitor unit DESCRIPTION OF SYMBOLS 19 ... Power supply circuit part, 20 ... Electronic control unit, 30 ... Circuit board, 31 ... FET, 32 ... Elastic member, 33 ... Through-hole, 34 ... TIM, 40 ... ECU base, 41 ... Heat radiation part, 41a ... Heat radiation surface, 41b ... insulating layer, 42 ... straightening part, 42a ... straightening surface, 42b ... insulating layer, 43 ... screw hole, 50 ... plate, 51 ... heat radiation part, 51a ... heat radiation , 51b ... insulating layer, 52 ... correcting section, 52a ... correcting faces, 52 b ... insulating layer, 53 ... through hole, 60 ... mounting screw

Claims (6)

A circuit board on which electronic components including heating elements are surface-mounted,
A housing made of a metal base and a metal cover, and holding the circuit board by sandwiching and fixing the peripheral edge of the circuit board in the thickness direction,
At least one of the base and the cover is directly or indirectly sandwiched between the heating element and the heating element via a heat conductive member and an insulating layer at a position facing the heating element directly or across the circuit board. It has a heat dissipating part that makes contact indirectly,
The electronic control unit according to claim 1, wherein the base and the cover include a correction portion that presses the circuit board in the thickness direction through an insulating layer so as to correct the warp of the circuit board.   The electronic control unit according to claim 1, further comprising an elastic member between the circuit board and the correction unit.   The electronic control unit according to claim 2, wherein the elastic member includes a heat conductive material.   The electronic control unit according to claim 1, wherein the insulating layer is formed on the base and the cover.   The electronic control unit according to claim 1, wherein the heat conductive member includes an insulating material. A torque detector for detecting a steering torque transmitted from the steering wheel;
An electric motor that generates a steering assist torque according to the steering torque detected by the torque detector;
An electric power steering apparatus comprising: the electronic control unit according to any one of claims 1 to 5 that controls driving of the electric motor.

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