JP2020004887A - Circuit board - Google Patents

Abstract

To provide a circuit board that secures a mounting area for a control element and a power element and improves mounting efficiency.SOLUTION: One side 25 of a circuit board 22 is arranged so as to face one side in the axial direction of a motor, and a power elements FET1 to FET11 and a control element 31 for motor driving are mounted on the other side 23 of the circuit board 22, and the control element 31 is arranged outside the power elements FET1 to FET11 in the radial direction of the motor on the circuit board 22. Further, heat is conducted from one surface side to the other surface side of the circuit board 22 via copper inlays IL1 to IL11 provided on the circuit board 22 for each power element, and the conducted heat is radiated to an external radiator.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a circuit board, and more particularly, to a motor driving circuit board used in an electronic control unit of an electric power steering device.

  2. Description of the Related Art A vehicle such as an automobile is equipped with an electric motor that generates an auxiliary torque in response to a driver's operation of a steering wheel, and an electric power steering device that includes a control device for the electric motor. 2. Description of the Related Art As an electric power steering apparatus has a tendency to be reduced in size, it is important to reduce the size and minimization of the size of a circuit board constituting an electronic control unit. At the same time, heat dissipation of heat generated from the control device and the like is also important.

  Patent Literature 1 discloses that an electronic component is mounted on an electronic component mounting surface, which is a surface opposite to a motor side of a substrate, and a SW element mounted on a heating element mounting surface, which is a motor side surface, includes a motor shaft. The motor wires of each phase are arranged point-symmetrically with respect to the axis center in the order of W phase, V phase and U phase, and the motor lines of the respective phases are arranged on the ECU side of the frame member via the heat radiation gel. A drive device that is in contact with an end face in a state capable of dissipating heat is disclosed.

Japanese Patent No. 6123848

  The electric power steering device using the driving device of Patent Document 1 employs a double inverter system, and a plurality of SW elements mounted on a heating element mounting surface are line-symmetric with respect to a straight line passing through the axis of the motor. To reduce the impedance, and arrange the motor wires in point symmetry with respect to the axis center, thereby reducing the variation in the wiring length of each phase and the variation in the impedance.

  Further, in Patent Document 1, the mounting surface of the microcomputer is opposite to the surface on which the SW element is mounted, so that the mounting area of the substrate cannot be used effectively, and the mounting efficiency in production decreases, There is a problem that heat generated in the element cannot be efficiently dissipated.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to secure a mounting area for a control element and a power element on a circuit board, improve the mounting efficiency of these components, and improve the efficiency. An object of the present invention is to provide a circuit board capable of dissipating heat.

  The following configuration is provided as one means for achieving the above object and solving the above-mentioned problems. That is, an exemplary first invention of the present application is a circuit board for driving a motor, wherein one side of the circuit board is arranged so as to face one side in the axial direction of the motor, and A power element and a control element for driving a motor are mounted on the other surface side, and the control element is arranged outside the power element in a predetermined direction, and a metal provided on the circuit board for each power element The circuit board is characterized in that heat is conducted from one surface side to the other surface side of the circuit board via the penetrating member, and the conducted heat is radiated to an external radiator.

  A second exemplary invention of the present application is an electronic control unit for electric power steering formed integrally with an electric motor, wherein the circuit board according to the first exemplary invention is mounted on a circuit of the electronic control unit. It is characterized in that it is a substrate.

  An exemplary third invention of the present application is an electric power steering device that assists a driver of a vehicle or the like to operate a steering wheel, wherein the torque sensor detects torque due to the operation of the steering wheel, and the above-described second exemplary invention. And an electric motor driven by the electronic control unit for electric power steering based on the torque detected by the torque sensor.

  ADVANTAGE OF THE INVENTION According to this invention, even if a control element and a power element are mounted on the same surface of a circuit board, the mounting area of them can be ensured, and the efficiency of mounting components on the board during production can be improved.

FIG. 1 is a schematic configuration of a steering system including the electric power steering device according to the embodiment. FIG. 2 is an exploded perspective view of the electric power steering device integrated with the electronic control unit according to the embodiment. FIG. 3 is an external view of the front side of the control unit when viewed from above. FIG. 4 is an external view of the rear surface side of the control unit as viewed in plan. FIG. 5 is a diagram schematically illustrating a state where the main body of the electric motor and the control unit mounted on the output side opposite to the axial direction of the electric motor are viewed from a direction perpendicular to the axial direction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration of a steering system including an electric power steering device according to an embodiment of the present invention. The steering system 1 includes a steering handle 2 as a steering member, a rotating shaft 3 connected to the handle 2, a pinion gear 6, a rack shaft 7, an electric power steering device 10, and the like.

  The electric power steering apparatus 10 includes an electronic control unit (ECU) 20, an electric motor 15, and the like. The rotating shaft 3 is provided with a torque sensor 9 for detecting a steering torque when the steering wheel 2 is operated, and the detected steering torque is sent to the electronic control unit 20.

  The rotating shaft 3 meshes with a pinion gear 6 provided at the tip. The pinion gear 6 converts the rotational motion of the rotary shaft 3 into a linear motion of the rack shaft 7, and a pair of wheels 5 a and 5 b provided at both ends of the rack shaft 7 at an angle corresponding to the displacement of the rack shaft 7. Is steered.

  The electronic control unit 20 outputs an auxiliary torque for assisting the steering of the steering wheel 2 from the electric motor 15 based on signals such as the steering torque obtained from the torque sensor 9 and the vehicle speed from a vehicle speed sensor (not shown), and decelerates. The power is transmitted to the rotating shaft 3 via the gear 4. That is, the rotation of the rotating shaft 3 is assisted by the torque generated by the electric motor 15, thereby assisting the driver in operating the steering wheel.

  FIG. 2 is an exploded perspective view of an electric power steering device equipped with an electronic control unit for electric power steering according to an embodiment of the present invention and integrated with the electronic control unit. In the electric power steering apparatus 10 shown in FIG. 2, a heat sink 13 is disposed above an electric motor (brushless motor) 15 covered with a motor cover 14 in the axial direction (indicated by a dashed line in FIG. 2). The control unit 20 is placed on the upper side, on the side opposite to the output side of the electric motor 15 in the axial direction, and is fixed to the heat sink 13 with screws or the like.

  The heat sink 13 is a bearing holder and a member for radiating heat generated from the control unit 20 to be held, and is formed by, for example, aluminum die casting. By using the bearing holder of the electric motor as an external radiator, the number of components of the electronic control unit for electric power steering can be reduced.

  The upper part of the control unit 20 is covered with a metal or resin unit cover 12. The external connector 16 is a connection terminal for a power supply supplied to the electric motor 15, a control signal to the control unit 20, and the like. The external connector 16 is covered with a connector case and fixed to the heat sink 13.

  In the electric power steering apparatus 10 shown in FIG. 2, when the control unit 20 is held by the heat sink 13, a heat radiating area (heat radiating area) on the rear surface of the board corresponding to the area where the heat generating components are mounted on the substrate surface of the control unit 20. Portion) 27 and a heat receiving area (heat receiving portion) 29 provided in a plane on the heat sink 13 are opposed to each other with a predetermined gap therebetween.

  The gap is filled with a heat radiating material such as heat radiating grease, so that heat generated by the heat generating components of the control unit 20 is conducted to a circuit board pattern or the like arranged in the heat radiating area 27, and the circuit board pattern or the like is formed. Is dissipated to the heat sink 13.

  The heat radiating area 27 on the substrate and the heat receiving area 29 on the heat sink have substantially the same shape and area. However, in consideration of the heat radiating effect and efficiency, it is desirable that the heat receiving area 29 be larger than the heat radiating area 27. . The heat receiving area 29 may be formed in accordance with the shape of the heat radiating area 27 in consideration of designing the heat receiving area 29 in accordance with the shape of the heat radiating area 27 on the substrate.

  It should be noted that the electric power steering device is constantly operating, and if heat generated from the control unit of the electric power steering device during steering cannot be efficiently dissipated, overheat protection is applied. Therefore, in order to avoid a problem that the original purpose of the electric power steering device, which assists the steering of the steering wheel, is not achieved, it is important for the control unit to radiate heat from heat-generating components such as power elements on a circuit board.

  Next, the arrangement of components on the circuit board and the heat radiation configuration of the electronic control unit for electric power steering according to the present embodiment will be described in detail.

  FIG. 3 is an external view of the front surface of the control unit 20 (the unit cover 12 side) as viewed in plan, and FIG. 4 is an external view of the rear surface of the control unit 20 (the electric motor 15 side) as viewed in plan. Here, in order to make it easy to understand the correspondence between the front surface region and the back surface region of the control unit 20, FIG. 4 is a diagram when the back surface is seen through from the front surface side (FIG. 3).

  On the surface 23 of the circuit board 22 of the control unit 20 shown in FIG. 3, a control element (microprocessor) 31 for controlling the electric power steering device, an FET bridge circuit composed of FET1 to FET6, and a switching for supplying a drive current to the motor are provided. Various sensors (not shown) such as FETs (FET9 to FET11), electrolytic capacitors C1 to C3 for motor drive current, a control power supply element (power supply IC) 35, control power supply capacitors C11 to C13, and current sensors are mounted. ing.

  The control unit 20 has, on the surface 23 of the circuit board 22, a region for mounting a control system device such as a signal processing component for controlling the electric power steering device and various sensors such as a current sensor (also referred to as a control unit region 23a). , An FET bridge circuit composed of FET1 to FET6, a switching FET (FET9 to FET11) for supplying a drive current to the motor, and a region (also referred to as a power portion region 23b) on which electrolytic capacitors C1 to C3 are mounted. Have been divided.

  By dividing the control unit region 23a and the power unit region 23b, the control system device of the control unit 20 can control not only the control unit region 23a on the substrate front surface 23 but also the control unit on the back surface 25 of the substrate as shown in FIG. A pre-driver element 33, which is an element (IC) for controlling a motor drive FET, is mounted in the area 25a. As a result, components related to the control system of one circuit board can be mounted on the front and back surfaces of the board, so that the degree of freedom of design can be improved on a board having a limited area.

  On the power input side of the control unit 20, an external connector terminal 26 which is an input terminal for a positive potential and a negative potential of a drive power source of the electric motor 15 and the like, three electrolytic capacitors C1 to C3 connected in parallel, and a coil 56 are configured. A noise filter is arranged. The noise filter absorbs noise and the like included in the power supply supplied to the control unit 20, and smoothes the power supply voltage. The coil 56 is a common mode coil including, for example, two coils.

  The control unit 20 further includes FETs 7 and 8 functioning as semiconductor relays that can shut off power when an abnormality occurs in the power supply voltage from the battery, and six units that supply a drive current (three-phase AC current) to the electric motor 15. And a three-phase inverter circuit (FET bridge circuit) composed of the FETs 1 to 6 described above.

  The gates of the six FETs 1 to 6 constituting the FET bridge circuit are driven on or off by a signal from a control circuit (not shown) composed of, for example, a microcomputer, a pre-driver and the like. Each of the U, V, and W phase currents generated by the on or off control is a drive current supplied to the electric motor 15 via an output terminal unit 57 including three terminals U, V, and W.

  The FET 1 and the FET 2 are connected between a positive power supply line and a negative potential line (GND), and generate a U-phase current flowing through the U winding of the electric motor 15. The FET 9 functions as a semiconductor relay that can cut off the U-phase current. The FET 3 and the FET 4 are connected between a positive power supply line and a negative potential (GND) line, generate a V-phase current flowing through a V winding of the electric motor 15, and the FET 10 is a semiconductor relay that cuts off the V-phase current. It is.

  Similarly, FET5 and FET6 are connected between the positive power supply line and the negative potential (GND) line, generate a W-phase current flowing through the W winding of the electric motor 15, and the FET11 can cut off the W-phase current. Semiconductor relay.

  Although not shown, on the surface 23 of the circuit board 22, a torque interface circuit, a CAN circuit for transmitting and receiving various information of the vehicle, and the like are arranged. The circuit board 22 may be either a double-sided board or a multilayer board.

  As shown in FIG. 3, the circuit board 22 of the control unit 20 includes a motor having a through hole H1 formed by partially notching a plate end thereof, and through holes H2 and H3 formed by punching a portion near the plate end. It is arranged at a position symmetrical with respect to the central axis P. These through holes H1 to H3 are used as positioning when the control unit 20 is mounted on the electric motor 15, and positioning when the control unit 20 is fixed to the electric motor 15 is facilitated.

Next, the arrangement of components in the control unit 20 will be described.
In the electric power steering device 10, when the control unit 20 is mounted on the output side opposite to the axial direction of the electric motor 15, the intersection between the one-dot chain line (motor center axis) in FIG. 3 and FIG. Here, this intersection is referred to as a motor center axis P for convenience.

  Here, as shown in FIG. 3, in the control unit 20, two concentric regions A and B extending in the radial direction of the motor around the motor center axis P are assumed. The area A is an area surrounded by dotted lines 41 and 42, and the area B is an area surrounded by dotted lines 42 and 43.

  The area A is located radially inward of the area B, and an FET bridge circuit and a switching FET that generate a large amount of heat are arranged in the area A in the power section 23b. The region B is located radially outward of the region A, and the control element 31 of the electric power steering device is disposed in the region B of the control unit 23a.

  Further, in the area B on the side of the power section 23b, output terminal sections 57 for U, V, and W phase currents supplied to the electric motor 15 are arranged as shown in FIG. As shown in FIG. 4, a pre-driver element 33 is arranged in a region of the substrate back surface 25 corresponding to the region B on the control unit 23a side of the substrate front surface 23.

  As described above, in the control unit 20, the control element 31 is arranged outside the substrate 22 (outside in the radial direction) and away from the FET (also referred to as a power element) that generates a large amount of heat. Further, the control element 31 is arranged at a position distant from the output terminal 57 of each of the large currents U, V, and W.

  In other words, the control element 31 is disposed at a position symmetrical to the power element and the output terminal 57 with the motor center axis P interposed therebetween in the y direction in FIG. ing. Therefore, the control element 31, the power element, and other elements (capacitors and the like) are arranged in order from the outside in the radial direction of the motor, and the control element 31 transfers heat generated by the power element and the like on the same circuit board. It is located in a difficult position.

  Further, as shown in FIG. 3, the control element 31 is arranged at an angle different from other components such as a power element, with its corner portion located on the outer edge side of the circuit board 22.

  More specifically, when the circuit board 22 is viewed in a plan view, the power element and the like have one side and the other side respectively arranged along the x direction and the y direction, whereas the control element 31 Are arranged at a predetermined angle θ (for example, 45 °) with respect to the x direction (or y direction) in the vicinity of an edge having a curvature of the circuit board 22.

  Also, as shown in FIG. 4, on the substrate back surface 25 of the control unit 20, the pre-driver element 33 is also arranged by being rotated by a predetermined angle θ (for example, 45 °) with respect to the x direction (or y direction) similarly to the control element 31. Have been.

  In this way, by arranging the control element 31 and the pre-driver element 33 at a predetermined angle in a portion of the circuit board 22 having a curvature, for example, as shown by a broken line 45 in FIG. The control element 31 and the pre-driver element 33 can be arranged closer to the edge of the substrate as compared to the state along the direction and the y direction). Further, the dead space in the element peripheral region can be minimized, and the mounting area on the substrate can be effectively utilized. In this case, the pre-driver element 33 may be mounted in a vacant area on the surface of the substrate caused by minimizing the dead space.

  From the viewpoint of heat dissipation on the circuit board 22 of the control unit 20, for example, a heat transfer member (a heat conduction member) that penetrates the circuit board 22 in accordance with the mounting position of the FET bridge circuit and the switching FET that generate a large amount of heat. A copper inlay having a coin shape with a predetermined diameter is embedded. Specifically, as shown in FIG. 4, copper inlays IL1 to IL11 are arranged immediately below FET1 to FET11, respectively. The heat generated by the FETs 1 to 11 is radiated to the back surface 25 of the circuit board 22 via these copper inlays.

  In the above-described example, the control element 31 is disposed on the outermost side in the direction that expands in the radial direction of the motor from the motor central axis P on the circuit board 22. However, the control element 31 is disposed in the central axis direction of the motor. May be specified.

  FIG. 5 schematically illustrates the main body of the electric motor 15 and the control unit 20 mounted on the opposite side of the electric motor 15 in the axial direction when viewed from a direction perpendicular to the axial direction.

  Here, assuming that the center of gravity of the electric motor 15 is G, the distance L1 from the center of gravity G to a point p1 (the position where the control element 31 is disposed) on the control unit 20 and the point p2 from the center of gravity G (for example, a dashed line) (In the vicinity of the center axis of the motor and the position where the power element is disposed), the control element 31 is disposed closer to the edge of the substrate. There is a relationship of L2.

  As described above, the control element 31 is arranged at a position farthest from the center of gravity G of the electric motor 15, that is, in the central axis direction of the electric motor 15, the distance from the center of gravity G of the electric motor 15 is longer than that of the power element. By arranging the control element 31 in such a manner, the influence of heat generation from the power element can be avoided in the control element 31. This also applies to a pre-driver element arranged on the back surface of the substrate, which is not shown in FIG.

  In the electric power steering apparatus according to the present embodiment, as shown in FIG. 4 and the like, output terminals 57 of the U, V, and W phase currents supplied to the electric motor 15 are arranged on the power unit 25b side. I have. By doing so, the wiring distance from the three-phase inverter circuit or the like to the electric motor 15 can be shortened, and power loss due to lowering the resistance value due to the shorter power supply path pattern length can be reduced.

  Note that the arrangement numbers, arrangement positions, areas, and the like of the heat generating components (such as FETs), copper inlays, power supply patterns, and ground (GND) patterns on the circuit boards shown in FIGS. Can be changed as appropriate in accordance with the specifications.

  As described above, in the electronic control unit for the electric power steering according to the present embodiment, the substrate area is divided into the control section area and the power section area, and the control element is located closer to the motor center axis than the power element or the like. It is located radially outside of the motor.

  In this way, a power element such as an FET (a high heat-generating component) and a non-heat-generating component (a low heat-generating component) such as a control element can be separated on the substrate, and the power element and the control element are mounted on the same surface of the circuit board. In doing so, it is possible to improve the mounting efficiency of components in production while securing a mounting area according to the electrical characteristics of each element. Further, heat generated from the control element itself can be efficiently dissipated to the heat sink arranged above the electric motor in the axial direction.

  Furthermore, by arranging the control element and the pre-driver element at a predetermined angle in a portion of the circuit board having a curvature, the mounting area of the control element itself is secured while eliminating a dead space generated on the board, thereby producing the circuit. The above mounting efficiency can be improved.

  Also, since components related to the control system can be mounted on both sides of the circuit board on the same circuit board, the degree of freedom in design can be improved on a circuit board with a limited area due to size reduction.

  Furthermore, by disposing the control element so that the distance from the motor center axis in the radial direction of the motor and the distance from the center of gravity of the motor in the axial direction are longer than the power element, the control element is It is possible to avoid being affected by the heat generated from the above.

  In addition, the copper inlay as the metal penetrating member can secure a heat conduction path from one surface side to the other surface side of the circuit board, thereby enabling effective heat transfer and heat radiation. In addition, by using the housing of the electric motor as an external radiator, the number of parts of the electronic control unit for electric power steering can be reduced.

  According to the above configuration, effective heat dissipation can be achieved in the electric power steering electronic control unit formed integrally with the electric motor, so that the heat capacity design including the electric motor is facilitated. In addition, heat can be effectively dissipated when steering the vehicle, especially when turning the steering wheel, which requires assisting power from the power steering rather than when driving, so that the electric power steering device avoids stopping the operation of the electric motor due to overheating. Then, the necessary assist can be continued.

DESCRIPTION OF SYMBOLS 1 Steering system 2 Steering handle 3 Rotating shaft 4 Reduction gear 6 Pinion gear 7 Rack shaft 10 Electric power steering device 12 Unit cover 13 Heat sink 14 Motor cover 15 Electric motor 16 External connector 20 Electronic control unit 22 Circuit board 23 Board surface 23a, 25a Control section areas 23b, 25b Power section area 25 Backside of board 26 External connector terminals 27 Heat dissipation area (heat dissipation section)
29 Heat receiving area (heat receiving part)
31 Control element (microprocessor)
33 Pre-driver element 35 Power supply element for control (power supply IC)
56 Coil 57 Output terminals C1 to C3 Electrolytic capacitors C11 to C13 Control power supply capacitors H1 to H3 Through holes IL1 to IL11 Copper inlay

Claims (14)

A circuit board for driving a motor,
One side of the circuit board is disposed so as to face one side in the axial direction of the motor, and a power element and a control element for driving a motor are mounted on the other side of the circuit board, and in a predetermined direction. The control element is disposed outside the power element,
Heat conducting from one surface side to the other surface side of the circuit board via a metal penetrating member provided on the circuit board for each power element, and dissipating the conducted heat to an external radiator. Circuit board.   The radial direction of the motor on the circuit board is the predetermined direction, and the control element has a longer separation distance from the intersection of the circuit board and the central axis of the motor in the radial direction than the power element. The circuit board according to claim 1.   2. The circuit board according to claim 1, wherein an axial direction of the motor is the predetermined direction, and the control element has a longer distance from a center of gravity of the motor in the axial direction than the power element. 3.   The circuit board according to any one of claims 1 to 3, wherein the control element, the power element, and another element are arranged in order from a radial outside of the motor.   The circuit board has a shape having a curvature portion in plan view, and a mounting direction of the control element disposed near the curvature portion is different from a mounting direction of the power element and the other element. Item 5. The circuit board according to item 4.   The circuit board according to any one of claims 1 to 5, wherein the other surface of the circuit board is divided into a mounting area for the power element and a mounting area for the control element.   The microprocessor and the power supply circuit are arranged on the other surface of the circuit board, and the pre-driver circuit is arranged on one or the other surface of the circuit board. The circuit board according to claim 1.   8. The circuit board according to claim 7, wherein the microprocessor is arranged on the other side of the circuit board corresponding to the arrangement position of the pre-driver circuit on one side of the circuit board.   8. The circuit board according to claim 7, wherein a torque interface circuit and a CAN circuit are arranged near an external connection connector on one side of the circuit board, and the pre-driver circuit is arranged on the one side. .   A through-hole formed by partially notching a plate end of the circuit board and a through-hole formed by punching the vicinity of the plate end are symmetrically arranged at the intersection, and the through-hole is used as a positioning of the circuit board with respect to the motor. The circuit board according to claim 2, wherein the circuit board is used. An electronic control unit for electric power steering formed integrally with an electric motor,
An electronic control unit for electric power steering, wherein the circuit board according to any one of claims 1 to 10 is used as a circuit board of the electronic control unit.   12. The electric motor case is used as the external heat radiator, and heat generated from the power element is conducted to a heat receiving surface formed on a part of the external heat radiator to radiate heat. An electronic control unit for an electric power steering according to claim 1.   The electric power according to claim 11, wherein an output terminal of a three-phase bridge circuit that generates an AC power supply for driving the electric motor is arranged in a region between a plate edge of the circuit board and the power element. Electronic control unit for steering. An electric power steering device which assists a driver of a vehicle or the like in operating a steering wheel,
A torque sensor for detecting torque by operating the steering wheel,
An electronic control unit for electric power steering according to any one of claims 11 to 13,
An electric motor driven by an electronic control unit for the electric power steering based on the torque detected by the torque sensor,
An electric power steering device comprising:

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