Electric power steering control unit

Abstract

To provide a controller of an electric power steering system making it possible to prevent the resolution of a motor current from excessively degrading and to inexpensively upgrade the heat radiation efficiency of a shunt resistor.SOLUTION: An EPS-ECU 60 that performs steering control of a vehicle 1 includes a substrate 100, a shunt resistor R1 and MOSFETs 120a to 120d mounted on the substrate 100, and a substrate fixation / heat radiation structure 130 disposed on an undersurface 100B of the substrate 100. The substrate fixation / heat radiation structure 130 includes substrate fixation parts 132a to 132d, MOSFET heat radiation parts 133, and a shunt resistor heat radiation part 134. A via hole 101 is formed between the shunt resistor R1 and MOSFET 120a on the substrate 100. The via hole 101 is filled with a grease 140. The grease 140 poured into the via hole 101 is in contact with the shunt resistor heat radiation part 134 and MOSFET heat radiation part 133.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a control device for an electric power steering having a heat dissipation structure related to a shunt resistor constituting a current detection circuit.

Background Art

[0002] Conventionally, there has been an electronic control unit (EPS-ECU (Electric Power Stearing-Electronic Control Unit)) for electric power steering that assists the force required for a driver's steering operation using a brushed motor (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, an EPS-ECU that uses a brushed motor realizes the function of detecting the motor current of the brushed motor by itself with a current detection circuit.

[0005] As a current detection circuit, for example, a current detection circuit 110 having the circuit configuration shown in Figure 9 can be used. The circuit configuration of the current detection circuit 110 shown in Figure 9 is a general current detection circuit configuration, so a detailed explanation will be omitted and only a brief description will be given. The current detection circuit 110 includes resistors R1 to R7, an operational amplifier AMP, and a smoothing capacitor C. In the current detection circuit 110, the current flowing through the brushed motor (motor current of the brushed motor) is converted into a voltage by passing current through the shunt resistor R1. The resistors R2 to R6 and the operational amplifier AMP constitute an offset-compensated negative feedback non-inverting amplifier circuit, with negative feedback applied by resistors R5 and R6, and the offset voltage generated between the non-inverting input terminal and the inverting input terminal of the operational amplifier AMP compensated by resistors R2 to R4. The voltage converted by passing the motor current through the shunt resistor R1 is amplified by the operational amplifier AMP and resistors R5 and R6, and the amplified voltage (output voltage) is output from terminal T as the voltage of resistor R7. The analog voltage value amplified by the current detection circuit 110 is converted to a digital voltage value and used by the CPU in the EPS-ECU.

[0006] For example, when increasing the current of a brushed motor (e.g., from 55[A] to 65[A]), the current detection range on the system expands, as shown in Figure 10(a) as an example (the maximum value of the current detection range increases from [A] to [B]). On the other hand, due to the CPU specifications, the upper limit of the output voltage of the current detection circuit 110 (5[V]) cannot be changed, and the dynamic range cannot be changed. Therefore, in order to handle high currents, it is necessary to lower the resistance value of the shunt resistor R1 to reduce the current resolution to a resolution commensurate with the high current. Note that if the CPU is made more advanced (e.g., from 12-bit to 14-bit), it is possible to handle high currents without reducing the current resolution, but this raises concerns about increased CPU costs and overflow during calculations.

[0007] If the resistance value of the shunt resistor R1 is reduced, the current detection performance of the current detection circuit 110 deteriorates due to a decrease in current resolution. This may cause the comparator that compares the output voltage of the current detection circuit 110 with the reference voltage to be unable to respond to fluctuations in the output voltage of the current detection circuit 110, potentially leading to larger current fluctuations.

[0008] Furthermore, if a surface-mount component (a component mounted on the main surface of the circuit board) is used as the shunt resistor R1, the heat generated due to the miniaturization of the shunt resistor R1 necessitates an even smaller resistance value for R1. When using a surface-mount component compared to using a plate shunt, as shown in Figure 10(b) as an example, the current detection range in the system expands (the maximum value of the current detection range increases from "B" to "C"), the current resolution decreases beyond the required level, and there is a risk that the system performance related to current fluctuations may not be satisfactory.

[0009] Furthermore, if a surface-mount component is used as the shunt resistor R1, it is possible to increase the gain value of the current detection circuit 110 to return the maximum value of the system's current detection range from "C" to "B" (the maximum value when using a plate shunt). However, if the gain value of the current detection circuit 110 is increased, the radio waves (noise) superimposed on the signal on the wires of the current detection circuit 110 will also be greatly amplified, which may cause malfunctions in the CPU that uses the output voltage of the current detection circuit 110. For this reason, there is a limit to how much the gain value of the current detection circuit 110 can be increased, and there is a risk that, compared to before the gain value was increased, the maximum value of the system's current detection range can only be returned from "C" to "D" (it may not be possible to return from "C" to "B"), as shown in the example in Figure 10(c).

[0010] This invention has been made in view of the above-mentioned problems, and aims to provide a technology for an electric power steering control device that prevents an excessive decrease in the resolution of the motor current without using a high-performance CPU, and that can inexpensively improve the heat dissipation efficiency of the shunt resistor. [Means for solving the problem]

[0011] To achieve the above objective, the electric power steering control device according to the present invention includes a current detection circuit including a shunt resistor for detecting the motor current of a brushed motor, and controls the brushed motor based on the motor current detected by the current detection circuit to control the steering of the vehicle, comprising: a plurality of heat-generating electronic components including a shunt resistor; a substrate on which the shunt resistor is surface-mounted at a predetermined end of the main surface and other heat-generating electronic components different from the shunt resistor are surface-mounted at specific locations on the main surface, and a predetermined location on a predetermined end side of the shunt resistor is fixed to a fixing object; and the substrate is sandwiched between the shunt resistor and the substrate is suspended. The heat sink comprises: a first heat sink positioned such that it overlaps with the shunt resistor in a plan view taken perpendicular to the shunt resistor, and absorbs and dissipates heat from the shunt resistor; a second heat sink positioned between the substrate and other heat-generating electronic components, and overlapping with the other heat-generating electronic components in a plan view, and absorbs and dissipates heat from the other heat-generating electronic components; through-vias that penetrate the substrate and are positioned between the heat-generating electronic components in a plan view; and thermal grease filled in the through-vias. The first and second heat sinks are connected, and the thermal grease extends from the through-vias toward one of the first and second heat sinks, and is in contact with the heat sink.

[0012] In this configuration, the shunt resistor is placed at the edge of the main surface of the substrate, where the warping of the substrate is small, and the first heat sink is positioned so that it overlaps with the shunt resistor. In this case, compared to when the shunt resistor is placed at an area where the warping of the substrate is large, the distance between the shunt resistor and the first heat sink can be shortened, thereby improving the heat dissipation characteristics of the shunt resistor. Furthermore, through vias filled with thermal grease are provided between multiple heat-generating electronic components, including the shunt resistor, and this thermal grease is in contact with either the first or second heat sink. Therefore, the heat generated from the heat-generating electronic components can be efficiently dissipated from that heat sink. In addition, because the first and second heat sinks are connected, the heat generated from the heat-generating electronic components can be effectively distributed between the first and second heat sinks. Moreover, since the heat generated from the shunt resistor can be efficiently dissipated, there is no need to lower the resistance value of the shunt resistor to suppress heat generation. Therefore, it is possible to prevent an excessive decrease in motor current resolution caused by lowering the resistance value of the shunt resistor. In addition, by not lowering the resistance value of the shunt resistor, it becomes unnecessary to use a high-performance CPU, thus reducing the cost of the electric power steering control device. Furthermore, by filling the through-vias with thermal grease, the heat dissipation characteristics can be improved, so for example, inexpensive, small components with low power ratings can be used as heat-generating components on the circuit board, thus enabling miniaturization and cost reduction.

[0013] Furthermore, a through-via formation region is provided on the main surface of the substrate between the shunt resistor and other heat-generating electronic components, and the through-via formation region may have a portion that overlaps with both the first heat sink and the second heat sink in a plan view.

[0014] This configuration allows heat generated from the shunt resistor and other heat-generating electronic components to be effectively distributed between the first and second heat sinks. Furthermore, since the shunt resistor and other heat-generating electronic components generate heat when energized, they are positioned at a predetermined distance (required distance between components) to prevent them from affecting each other's heat. This configuration allows heat generated from the shunt resistor and other heat-generating electronic components to be effectively distributed between the first and second heat sinks via through-vias placed between them. Therefore, the distance between the shunt resistor and other heat-generating electronic components (required distance between components) can be shortened, enabling miniaturization of the control device. [Effects of the Invention]

[0015] According to the present invention, compared to the case where the shunt resistor is placed in a location with significant warping of the substrate, the distance between the shunt resistor and the first heat sink can be shortened, thereby improving the heat dissipation characteristics of the shunt resistor. Furthermore, through vias filled with thermal grease are provided between multiple heat-generating electronic components, including the shunt resistor, and this thermal grease is in contact with one of the first and second heat sinks. Therefore, heat generated from the heat-generating electronic components can be efficiently dissipated from the heat sink. In addition, because the first and second heat sinks are connected, heat generated from the heat-generating electronic components can be effectively distributed between the first and second heat sinks. Moreover, since heat generated from the shunt resistor can be efficiently dissipated, there is no need to lower the resistance value of the shunt resistor to suppress heat generation. This prevents an excessive decrease in the motor current resolution that would occur if the resistance value of the shunt resistor were lowered. Furthermore, by not reducing the resistance value of the shunt resistor, the need for a high-performance CPU is eliminated, thus reducing the cost of the electric power steering control unit. In addition, by filling the through-vias with thermal grease, the heat dissipation characteristics can be improved, allowing for the use of inexpensive, small components with low power ratings as heat-generating components on the circuit board, thus enabling miniaturization and cost reduction. [Brief explanation of the drawing]

[0016] [Figure 1] It is a system configuration diagram showing the system configuration of an electric power steering according to an embodiment of the present invention. [Figure 2] It is a diagram showing the circuit configuration of the H-bridge circuit in FIG. 1. [Figure 3] It is a diagram for explaining an example of a heat dissipation structure for the heat of the shunt resistor constituting the current detection circuit in the EPS-ECU in FIG. 1 and the heat of the MOS-FET constituting the H-bridge circuit. [Figure 4] It is a schematic diagram for explaining the warping of the substrate and the distance between the substrate and the substrate fixing and heat dissipation structure when the substrate is attached and fixed to the substrate fixing portion of the substrate fixing and heat dissipation structure in FIG. 3. [Figure 5] It is a schematic diagram for explaining the width of the grease arranged between the substrate and the heat dissipation portion for the shunt resistor when the substrate is attached and fixed to the substrate fixing portion of the substrate fixing and heat dissipation structure in FIG. 3. [Figure 6] It is a diagram for explaining the arrangement relationship of the heat dissipation portion for the shunt resistor, the heat dissipation portion for the MOS-FET, and each through-via. [Figure 7] It is a diagram for explaining the filling state of the grease of the through-via. [Figure 8] It is a diagram for explaining a modified example of the heat dissipation structure for the heat of the shunt resistor and the heat of the MOS-FET. [Figure 9] It is a circuit diagram showing the circuit configuration of a conventional current detection circuit. [Figure 10] (a) to (c) are diagrams showing the characteristics of the detected current and the output voltage of the current detection circuit for explaining the problems.

Embodiments for Carrying Out the Invention

[0017] An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0018] The EPS-ECU 60 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 7. Note that the EPS-ECU 60 corresponds to the "control device for electric power steering" of the present invention.

[0019] As shown in FIG. 1, the vehicle 1 includes a steering wheel (not shown), a steering angle sensor 10, a brushed motor 20, a torque sensor 30, a photographing device 40, a camera ECU 50, and an EPS-ECU 60.

[0020] The steering angle sensor 10 is a sensor that detects the rotation angle (steering angle) of the steering wheel (steering) from the neutral position. In the present embodiment, the steering angle sensor 10 sets the neutral position as 0 [deg], detects the steering angle with a positive value when the steering wheel is operated clockwise and a negative value when the steering wheel is operated counterclockwise, and outputs the detected steering angle to the EPS-ECU 60. Further, the steering angle sensor 10 calculates the angular velocity of the steering wheel from the steering angle detected by the steering angle sensor 10 and the time measured by a timer, and outputs the calculated angular velocity to the EPS-ECU 60.

[0021] The brushed motor 20 is controlled by the EPS-ECU 60 for the energization direction (the energization direction of rotating the brushed motor 20 clockwise or counterclockwise) and the current value of the current applied to the brushed motor 20, and outputs a torque for rotating the steering wheel according to the energization direction and the current value of the current applied to the brushed motor 20.

[0022] The torque sensor 30 is a sensor that detects the steering torque applied to the steering wheel, and outputs the detected steering torque to the EPS-ECU 60.

[0023] The photographing device 40 photographs images around the vehicle 1, and is composed of cameras provided at a plurality of locations on the vehicle 1, such as a right side camera, a left side camera, a front camera, and a rear camera of the vehicle 1. The photographing device 40 outputs the image data photographed by each camera to the camera ECU 50.

[0024] The camera ECU 50 is an electronic control unit that performs control related to driver assistance, and consists of a microprocessor equipped with a CPU (not shown) that performs various controls and calculations, and a memory (not shown) that stores various programs and data. When automatic steering is performed to assist the driver, the camera ECU 50 calculates a target steering angle based on image data input from the camera 40, and outputs the calculated target steering angle to the EPS-ECU 60.

[0025] The EPS-ECU60 (corresponding to the "control device for electric power steering" of the present invention) is an electronic control unit that performs control related to automatic steering and other aspects of driver assistance. It consists of a circuit board 100 (see Figure 3), a microprocessor 61 equipped with a CPU (not shown) for performing various calculations and a memory (not shown) for storing various programs and data, a current detection circuit 110, an H-bridge circuit 120, and the like. In this embodiment, the current detection circuit 110 uses a general current detection circuit as shown in Figure 9. The H-bridge circuit 120 has a general current detection circuit configuration as shown in Figure 2, so a detailed explanation is omitted and only a brief explanation is given.

[0026] The H-bridge circuit 120 shown in Figure 2 is configured by combining four MOS-FETs 120a to 12d. (a) When MOS-FET 120a=ON, MOS-FET 120b=OFF, MOS-FET 120c=OFF, and MOS-FET 120d=ON, the direction of current flow applied to the brushed motor 20 is used to control the rotation direction of the brushed motor 20 to one rotation direction. (b) When MOS-FET 120a=OFF, MOS-FET 120b=ON, MOS-FET 120c=ON, and MOS-FET 120d=OFF, the direction of current flow applied to the brushed motor 20 is used to control the rotation direction of the brushed motor 20 to another rotation direction. (c)MOS-FET120a=OFF, MOS-FET120b=OFF, MOS-FET120c=OFF, MOS-FET120d=OFF, (d)MOS-FET120a=OFF, MOS-FET120b=OFF, MOS-FET120c=ON, MOS-FET120d=ON are used as brakes for the brushed motor 20. Also, (e)MOS-FET120a=ON, MOS-FET120b=OFF, MOS-FET120c=ON, MOS-FET120d=OFF, (f)MOS-FET120a=OFF, MOS-FET120b=ON, MOS-FET120c=OFF, MOS-FET120d=ON are prohibited from use.

[0027] Under normal conditions, the EPS-ECU60 detects the driver's steering wheel operation and controls the drive of the brushed motor 20 to assist rotation in the detected direction of operation. This normal control is performed by the EPS-ECU60 controlling the direction and value of the current applied to the brushed motor 20 by controlling the ON / OFF state of the four MOS-FETs 120a to 120d that constitute the H-bridge circuit 120.

[0028] Furthermore, during automatic steering that assists the driver, the EPS-ECU60 controls the drive of the brushed motor 20 based on the steering angle and angular velocity of the steering wheel detected by the steering angle sensor 10, the steering torque detected by the torque sensor 30, the target steering angle calculated by the camera ECU 50, and the motor current detected by the current detection circuit 110. This control during automatic steering is performed by the EPS-ECU60 controlling the direction and value of the current applied to the brushed motor 20 by controlling the ON / OFF state of the four MOS-FETs 120a to 120d that constitute the H-bridge circuit 120.

[0029] Next, the heat dissipation structure of the EPS-ECU60 will be explained with reference to Figure 3. The EPS-ECU60 in Figure 1, as shown in Figure 3, comprises a substrate 100, a microprocessor 61 equipped with a CPU and memory (see Figure 1), a current detection circuit 110 including a shunt resistor R1 as a component (see Figures 1 and 8), an H-bridge circuit 120 including four MOS-FETs 120a to 120d as components (see Figures 1 and 2), a substrate fixing and heat dissipation structure 130, and greases 140A and 140B. The substrate fixing and heat dissipation structure 130 comprises a base portion 131, four substrate fixing portions 132a to 132d, a heat dissipation portion 133 for the MOS-FETs, and a heat dissipation portion 134 for the shunt resistor.

[0030] The substrate 100 has a rectangular shape when viewed in a plan view (hereinafter simply referred to as "plan view") from the vertical direction on its upper surface 100A, which is one of its main surfaces. Circular through-holes 100a to 100d are provided at each of the four corners of the substrate 100 in this plan view. The substrate 100 is fixed to the substrate fixing and heat dissipation structure 130 with its lower surface 100B, the main surface opposite to the upper surface 100A, facing the base portion 131 of the substrate fixing and heat dissipation structure 130. As shown in Figure 3, the substrate fixing and heat dissipation structure 130 has four substrate fixing parts 132a to 132d at positions corresponding to the through-holes 100a to 100d of the substrate 100. Each substrate fixing part 132a to 132d extends vertically (upwards in the plane of the paper in Figure 3) from the base portion 131 toward the lower surface 100B of the substrate 100. Each substrate fixing portion 132a to 100d is substantially cylindrical in shape and has screw holes formed in the vertical direction. The through holes 100a to 100d of the substrate 100 are positioned to overlap with the screw holes provided in the corresponding substrate fixing portions 132a to 132d, and the substrate 100 is attached to the substrate fixing portions 132a to 132d by four screws 105a to 105d. In this way, the substrate 100 is attached to the substrate fixing portions 132a to 132d and fixed to the substrate fixing and heat dissipation structure 130.

[0031] On the upper surface 100A of the substrate 100, a microprocessor 61 (see Figure 1), a current detection circuit 110 (see Figures 1 and 9) including a shunt resistor R1 as a component, and an H-bridge circuit 120 (see Figures 1 and 2) including four MOS-FETs 120a to 120d as components are mounted.

[0032] The shunt resistor R1 is a surface-mounted component (SMD: Surface Mount Device) that is mounted on the top surface 100A of the substrate 100. The shunt resistor R1 is surface-mounted at the edge of the top surface 100A of the substrate 100. This edge is a region near edge 100da (the edge connecting the corner of the corner where the through-hole 100d is provided and the corner of the corner where the through-hole 100a is provided) that is within a predetermined distance set in advance. The portion of the substrate 100 with through-holes 100a fixed to the substrate fixing portion 132a is closer to edge 100ab (the edge connecting the corner where through-holes 100a is provided and the corner where through-holes 100b is provided) than the portion with through-holes 100d fixed to the substrate fixing portion 132d is closer to edge 100cd (the edge connecting the corner where through-holes 100c is provided and the corner where through-holes 100d is provided) than the portion with through-holes 100d fixed to the substrate fixing portion 132d than the portion with through-holes 100d fixed to the substrate fixing portion 132d than the portion with through-holes 100c is provided and the corner where through-holes 100d is provided) than the portion with through-holes 100a fixed to the substrate fixing portion 132a is closer to edge 100cd (the edge connecting the corner where through-holes 100c is provided and the corner where through-holes 100d is provided) than the portion with through-holes 100a fixed to the substrate fixing portion 132a is closer to edge 100cd than the portion withd fixed to the substrate fixing portion 132d than the portion with through-holes 100d fixed to the substrate fixing portion 132d.

[0033] Each of the four MOS-FETs 120a to 120d is a surface-mounted (SMD) component that is mounted on the top surface 100A of the substrate 100. Each of the MOS-FETs 120a to 120d is surface-mounted near the center between side 100ab (the side connecting the corner where through-hole 100a is provided and the corner where through-hole 100b is provided) and side 100cd (the side connecting the corner where through-hole 100c is provided and the corner where through-hole 100d is provided) on the top surface 100A of the substrate 100. In this embodiment, each of the MOS-FETs 120a to 120d is arranged in a line parallel to side 100cd (or side 100ab). Shunt resistor R1 is closer to side 100ab (the side connecting the corner where through-hole 100a is located and the corner where through-hole 100b is located) than to each of the four MOS-FETs 120a to 120d. Furthermore, the shortest distance between shunt resistor R1 and side 100ab (the side connecting the corner where through-hole 100a is located and the corner where through-hole 100b is located) is smaller than the shortest distance between each of the four MOS-FETs 120a to 120d and side 100cd (the side connecting the corner where through-hole 100c is located and the corner where through-hole 100d is located). Furthermore, the shortest distance between each of the four MOS-FETs 120a to 120d and the edge 100da on the top surface 100A of the substrate 100 that is closest to the MOS-FETs 120a to 120d is smaller than the shortest distance between the shunt resistor R1 and the edge 100da on the top surface 100A of the substrate 100 that is closest to the shunt resistor R1. Note that the shunt resistor R1 and each of the MOS-FETs 120a to 120d, which generate heat when energized, correspond to the "heat-generating electronic components" of the present invention.

[0034] The substrate fixing and heat dissipation structure 130 is formed of a material with thermal conductivity (for example, aluminum). When the substrate fixing and heat dissipation structure 130 is formed of metal, the base portion 131, substrate fixing portions 132a to 132d, the heat dissipation portion for MOS-FETs 133, and the heat dissipation portion for shunt resistors 134 can be formed together, for example, by forging. Electronic components may be mounted on the lower surface 100B of the substrate 100, or wiring patterns may be formed thereon. Therefore, if the heat dissipation portion for MOS-FETs 133 or the heat dissipation portion for shunt resistors 134 is formed of a conductive material such as metal, contact between the heat dissipation portion for MOS-FETs 133 or the heat dissipation portion for shunt resistors 134 and the lower surface 100B of the substrate 100 may cause problems such as a short circuit in the pattern on the lower surface 100B of the substrate 100. Therefore, the heights of the shunt resistor heat dissipation section 134 and the MOS-FET heat dissipation section 133 of the substrate fixing / heat dissipation structure 130 (distance from the base section 131 toward the lower surface 100B of the substrate 100: height relative to the base section 131) are designed so that they do not come into contact with the lower surface 100B of the substrate 100. The heights of the shunt resistor heat dissipation section 134 and the MOS-FET heat dissipation section 133 are designed taking into account the warping of the substrate 100.

[0035] Here, the warping of the substrate 100 will be explained with reference to Figure 4. When the substrate 100 is fixed to the four substrate fixing parts 132a to 132d of the substrate fixing / heat dissipation structure 130 using four screws 105a to 105d, and the substrate 100 warps as shown in Figure 4, the amount of warping of the substrate 100 is smaller at the edges closer to the substrate fixing parts 132a to 132d than at the center of the substrate 100. In addition, although there are individual differences in the warping of the substrate, the individual difference in the amount of warping of the substrate 100 is also smaller at the edges closer to the substrate fixing parts 132a to 132d than at the center of the substrate 100. Therefore, the distance (clearance) between the upper surface 134a of the shunt resistor heat dissipation section 134, which corresponds to the end closest to the substrate fixing sections 132a to 132d, and the lower surface 100B of the substrate 100 can be designed to be shorter than the distance (clearance) between the upper surface 133a of the MOS-FET heat dissipation section 133, which is further away from the substrate fixing sections 132a to 132d, and the lower surface 100B of the substrate 100. In this embodiment, the heights of the shunt resistor heat dissipation section 134 and the MOS-FET heat dissipation section 133 are designed such that the distance between the upper surface 134a of the shunt resistor heat dissipation section 134 and the lower surface 100B of the substrate 100 is shorter than the distance between the upper surface 133a of the MOS-FET heat dissipation section 133 and the lower surface 100B of the substrate 100.

[0036] The MOS-FET heat dissipation section 133 (corresponding to the "second heat sink" of the present invention) primarily absorbs heat from the MOS-FETs 120a to 120d and releases it to the outside. The MOS-FET heat dissipation section 133 is positioned on the base portion 131 such that it sandwiches the substrate 100 between the MOS-FETs 120a to 120d, and overlaps with the MOS-FETs 120a to 120d in a plan view. In other words, the MOS-FETs 120a to 120d are surface-mounted on the upper surface 100A of the substrate 100 and are located on the upper surface 100A side, while the MOS-FET heat dissipation section 133 is located on the lower surface 100B side of the substrate 100. In a plan view, the MOS-FET heat dissipation section 133 is positioned near the center between the line connecting the substrate fixing portion 132a and the substrate fixing portion 132b, and the line connecting the substrate fixing portion 132c and the substrate fixing portion 132d.

[0037] A projection 133b for correcting warping is formed in the center of the upper surface 133a of the heat dissipation section 133 for the MOS-FET. This projection 133b can be formed from the same material as the base section 131, the substrate fixing sections 132a to 132d, the heat dissipation section 133 for the MOS-FET, and the heat dissipation section 134 for the shunt resistor. In this case, each part 131, 132a to 132d, 133, 133b, and 134 can be formed collectively by casting. In this case, it is advisable to avoid placing wiring patterns or components in areas on the lower surface 100B of the substrate 100 that may come into contact with the projection 133b.

[0038] As described above, by providing the warp-correcting protrusion 133b, if the substrate 100 warps downwards (warping toward the substrate fixing / heat dissipation structure 130), the warp of the substrate 100 is corrected by the protrusion 133b. This prevents contact between the substrate 100 and the substrate fixing / heat dissipation structure 130 (MOS-FET heat dissipation section 133, shunt resistor heat dissipation section 134) due to the warp of the substrate 100. As a result, the distance (clearance) between the upper surface 134a of the shunt resistor heat dissipation section 134 and the lower surface 100B of the substrate 100, and the distance (clearance) between the upper surface 133a of the MOS-FET heat dissipation section 133 and the lower surface 100B of the substrate 100 can be reduced in the design. By reducing the distance (clearance) between the upper surface 134a of the shunt resistor heat dissipation section 134 and the lower surface 100B of the substrate 100, and by reducing the distance (clearance) between the upper surface 133a of the MOS-FET heat dissipation section 133 and the lower surface 100B of the substrate 100, the heat dissipation characteristics of the heat generated from the shunt resistor R1 and MOS-FETs 120a to 120d are improved. The warp correction projection 133b may be formed integrally with the MOS-FET heat dissipation section 133, or it may be a separate component.

[0039] The heat dissipation section 134 for the shunt resistor (corresponding to the "first heat sink" of the present invention) primarily absorbs heat from the shunt resistor R1 and releases it to the outside. The heat dissipation section 134 for the shunt resistor is positioned on the base portion 131 such that it sandwiches the substrate 100 between the shunt resistor R1 and the shunt resistor R1, and overlaps with the shunt resistor R1 in a plan view. In other words, the shunt resistor R1 is surface-mounted on the upper surface 100A of the substrate 100 and is on the upper surface 100A side, while the heat dissipation section 134 for the shunt resistor is on the lower surface 100B side of the substrate 100. The heat dissipation section 134 for the shunt resistor is positioned between the line connecting the substrate fixing section 132a and the substrate fixing section 132b, and the line connecting the substrate fixing section 132c and the substrate fixing section 132d, in a plan view, and is positioned such that the heat dissipation section 134 for the shunt resistor is closer to the line connecting the substrate fixing section 132a and the substrate fixing section 132b than the heat dissipation section 133 for the MOS-FET. In other words, the heat dissipation section 134 for the shunt resistor is closer to side 100ab (the side connecting the corner of the substrate 100 where the through hole 100a is provided and the corner of the substrate 100 where the through hole 100b is provided) than the heat dissipation section 133 for the MOS-FET. Furthermore, the shortest distance of the heat dissipation section 134 for the shunt resistor with respect to the line connecting the substrate fixing section 132a and the substrate fixing section 132b is smaller than the shortest distance of the heat dissipation section 133 for the MOS-FET with respect to the line connecting the substrate fixing section 132c and the substrate fixing section 132d.

[0040] The heat dissipation section 134 for the shunt resistor is positioned in close contact with the heat dissipation section 133 for the MOS-FET and is connected to the heat dissipation section 133 for the MOS-FET. Therefore, in this embodiment, the heat generated from the shunt resistor R1 is dispersed and dissipated between the heat dissipation section 134 for the shunt resistor and the heat dissipation section 133 for the MOS-FET. Similarly, the heat generated from the MOS-FETs 120a to 120d is also dispersed and dissipated between the heat dissipation section 133 for the MOS-FET and the heat dissipation section 134 for the shunt resistor.

[0041] On the substrate 100, in a plan view, multiple through-vias 101 (see Figures 1, 6, and 7) are formed between adjacent MOS-FETs 120a to 120d, and between the MOS-FET 120a closest to the shunt resistor R1 among the four MOS-FETs 120a to 120d and the shunt resistor R1. Here, in order to distinguish a particular through-via 101 from the others, the through-via located between adjacent MOS-FETs 120a to 120d is referred to as through-via 101a, the through-via located between the shunt resistor R1 and the adjacent MOS-FET 120a is referred to as through-via 101b, and when neither is distinguished, they are referred to as through-via 101.

[0042] Each through-via 101 penetrates the upper surface 100A and the lower surface 100B of the substrate 100 and has a circular shape in plan view. The inner surface of each through-via 101, the peripheral edge of the opening of the through-via 101 on the upper surface 100A of the substrate 100, and the peripheral edge of the opening of the through-via 101 on the lower surface 100B of the substrate 100 are all coated with, for example, Cu plating 102 (see Figure 7). Therefore, heat generated from the MOS-FETs 120a to 120d and heat generated from the shunt resistor R1 can be easily dissipated through the Cu plating 102 to the heat dissipation section 133 for the MOS-FETs and the heat dissipation section 134 for the shunt resistor.

[0043] Each through-via 101a positioned between adjacent MOS-FETs 120a to 120d is for dissipating heat generated from both adjacent MOS-FETs 120a to 120d towards the MOS-FET heat dissipation section 133. Between adjacent MOS-FETs 120a to 120d, two through-vias 101 are positioned, each arranged in a direction parallel to the long side 100da of the substrate 100.

[0044] Each through-via 101b positioned between the shunt resistor R1 and the MOS-FET 120a closest to it is for dissipating heat generated from both the shunt resistor R1 and the MOS-FET 120a to the MOS-FET heat dissipation section 133 and the shunt resistor heat dissipation section 134. In this embodiment, as shown in Figure 6, a through-via placement region Rb (corresponding to the "through-via formation region" of the present invention) is set up in a predetermined region between the MOS-FET 120a and the shunt resistor R1 on the upper surface 100A of the substrate 100 for arranging the through-vias 101b, and six through-vias 101b are formed in this region Rb. In this embodiment, if the lines parallel to the long side of the substrate 100, side 100da, are defined as rows, and the lines parallel to the short side of the substrate 100, side 100ab, are defined as columns, a total of six through-vias 101b are arranged in 2 rows and 3 columns in the through-via placement region Rb.

[0045] As shown in Figure 6, of the six through-vias 101b, two through-vias 101b in the row closest to side 100ab overlap the shunt resistor heat dissipation section 134 (upper surface 134a of the shunt resistor heat dissipation section 134) in a plan view. On the other hand, the remaining through-vias 101b overlap the MOS-FET heat dissipation section 133 (upper surface 133a of the MOS-FET heat dissipation section 133) in a plan view. In other words, the through-via arrangement region Rb has a region that overlaps the MOS-FET heat dissipation section 133 and a region that overlaps the shunt resistor heat dissipation section 134 in a plan view. To put it another way, the through-via arrangement region Rb is arranged to straddle the MOS-FET heat dissipation section 133 and the shunt resistor heat dissipation section 134 in a plan view.

[0046] The opening diameter of each through via 101 is preferably, for example, φ0.3cm to 1.0cm, taking into consideration the grease filling properties and heat dissipation characteristics described later.

[0047] The grease 140 (corresponding to the "thermal grease" of the present invention) is intended to improve the heat dissipation efficiency when dissipating heat generated from the shunt resistor R1 and MOS-FETs 120a to 12d to the substrate fixing / heat dissipation structure 130. It is mainly filled and arranged in the spaces between the lower surface 100B of the substrate 100 and the upper surface 133a of the MOS-FET heat dissipation section 133, and between the lower surface 100B of the substrate 100 and the upper surface 134a of the shunt resistor heat dissipation section 134. Here, in order to distinguish between specific types of grease 140, the grease 140 that is mainly filled in the space between the lower surface 100B of the substrate 100 and the upper surface 133a of the heat dissipation part 133 for the MOS-FET will be referred to as grease 140A, and the grease 140 that is mainly filled in the space between the lower surface 100B of the substrate 100 and the upper surface 134a of the heat dissipation part 134 for the shunt resistor will be referred to as grease 140B. If neither type is distinguished, the entire mixture will be referred to as grease 140.

[0048] In this embodiment, a heat dissipation grease with high thermal conductivity and insulating properties is used as the grease 140. As an insulating heat dissipation grease, for example, a modified silicone mixed with a filler such as a metal oxide (e.g., alumina) can be used.

[0049] The grease 140A is primarily provided to fill the space between the upper surface 133a of the MOS-FET heat dissipation section 133 and the lower surface 100B of the substrate 100. The grease 140A is also filled into each through-via 101a located between adjacent MOS-FETs 120a to 120d, and into some of the through-vias 101b located in the through-via arrangement region Rb. These some through-vias 101b are the four through-vias 101b that overlap with the upper surface 133a of the MOS-FET heat dissipation section 133 in a plan view (see Figure 6).

[0050] The filling state of grease 140A will be explained with reference to Figure 7, which shows an example of the filling state of grease 140B within the through vias 101b. Grease 140A has a portion that is filled in the space between the upper surface 133a of the MOS-FET heat dissipation section 133 and the lower surface 100B of the substrate 100, and a portion that is filled inside each through via 101a. The two portions are connected and form a single unit. In this case, it can also be said that grease 140A extends from each through via 101a toward the upper surface 133a of the MOS-FET heat dissipation section 133 and is in contact with the MOS-FET heat dissipation section 133.

[0051] The grease 140B is primarily provided to fill the space between the heat dissipation section 134 for the shunt resistor and the lower surface 100B of the substrate 100. The grease 140B is also filled into some of the through-vias 101b located in the through-via arrangement region Rb. These some through-vias 101b are two through-vias 101b that overlap with the upper surface 134a of the heat dissipation section 134 for the shunt resistor in a plan view (see Figure 6).

[0052] The filling state of the grease 140B will be explained with reference to Figure 7. The grease 140B has a portion that is filled in the space between the upper surface 134a of the shunt resistor heat dissipation section 134 and the lower surface 100B of the substrate 100, and a portion that is filled inside each through via 101b. The two portions are connected and form a single unit. In this case, it can also be said that the grease 140B extends from each through via 101b toward the upper surface 134a of the shunt resistor heat dissipation section 134 and is in contact with the shunt resistor heat dissipation section 134.

[0053] The thermal conductivity of grease 140 is higher than that of air. Therefore, when grease 140 is filled inside each through via 101, heat generated from the MOS-FETs 120a~120d and shunt resistor R1 is more easily transferred to the heat dissipation section 133 for the MOS-FETs and the heat dissipation section 134 for the shunt resistor than when nothing is filled inside the through via 101.

[0054] Let's assume that the substrate 100 is fixed to the four substrate fixing parts 132a to 132d of the substrate fixing / heat dissipation structure 130 using four screws 105a to 105d, and that a convex upward warp occurs on the substrate 100 as shown in Figure 4. In this case, as shown in Figure 5(a), the thickness of the grease 140B when the shunt resistor R1 and the heat dissipation part 134 for the shunt resistor are placed at the edge of the substrate 100, as in this embodiment, is thinner than the thickness of the grease 140B when the shunt resistor R1 and the heat dissipation part 134 for the shunt resistor are placed at the center of the substrate 100 (Figure 5(b)). If the substrate fixing / heat dissipation structure 130 is made of a metal such as aluminum, the substrate fixing / heat dissipation structure 130, including the heat dissipation part 133 for the MOS-FET and the heat dissipation part 134 for the shunt resistor, has a higher thermal conductivity than the grease 140. Therefore, a thinner grease 140B results in better heat dissipation characteristics.

[0055] The grease 140 is applied to the upper surface 133a of the MOS-FET heat dissipation section 133 and the upper surface 134a of the shunt resistor heat dissipation section 134 of the substrate fixing / heat dissipation structure 130 before the substrate 100 is fixed to the substrate fixing / heat dissipation structure 130 using screws 105a to 105d. At this time, the thickness of the grease 140A on the MOS-FET heat dissipation section 133 is made to be greater than the distance (clearance) between the upper surface 133a of the MOS-FET heat dissipation section 133 and the lower surface 100B of the substrate 100 when the substrate 100 is fixed to the substrate fixing / heat dissipation structure 130. In this way, when the substrate 100 is fixed to the substrate fixing / heat dissipation structure 130, the applied grease 140A spreads to fill the space between the upper surface 133a of the MOS-FET heat dissipation section 133 and the lower surface 100B of the substrate 100. The excess then gets pushed up into the interior of each through via 101a and some through vias 101b, so that the interior of each through via 101a and 101b is also filled with grease 140A.

[0056] The grease 140B applied to the shunt resistor heat dissipation section 134 is the same as the grease 140A. That is, the thickness of the grease 140B on the shunt resistor heat dissipation section 134 is made thicker than the distance (clearance) between the upper surface 134a of the shunt resistor heat dissipation section 134 and the lower surface 100B of the substrate 100 when the substrate 100 is fixed to the substrate fixing / heat dissipation structure 130. In this way, when the substrate 100 is fixed to the substrate fixing / heat dissipation structure 130, the applied grease 140B spreads to fill the space between the upper surface 134a of the shunt resistor heat dissipation section 134 and the lower surface 100B of the substrate 100, and the excess is pushed up into the interior of each through via 101b (or part of the through via 101b), so that the interior of each through via 101b is also filled with grease 140B.

[0057] When filling the through vias 101 with grease 140 in this manner, if the opening diameter of the through via 101 is too small, it becomes difficult for the grease 140 to enter the interior. Conversely, if the opening diameter of the through via 101 is large, the filling of the grease 140 improves, but the number of through vias 101 that can be formed decreases. Since the heat dissipation by the through vias 101 improves as the total area of ​​the inner circumferential surface covered with metal such as Cu plating increases, the more through vias 101 are arranged, the higher the heat dissipation characteristics of that region. Therefore, when considering both the filling ability of the grease 140 and the heat dissipation characteristics, it is preferable to arrange as many through vias 101 as possible while ensuring that the opening diameter of the through via 101 is large enough to allow for proper filling of the grease inside.

[0058] Therefore, according to the above embodiment, the shunt resistor R1 is placed on the upper surface 100A of the substrate 100, at the end of the substrate 100 where the curvature of the substrate 100 is small, and the shunt resistor R1 and the heat dissipation part 134 for the shunt resistor are arranged so that they overlap in a plan view with the substrate 100 in between. By doing so, the distance between the shunt resistor R1 and the heat dissipation part 134 for the shunt resistor can be shortened, and the heat dissipation characteristics of the shunt resistor R1 can be improved.

[0059] Furthermore, by connecting the heat dissipation section 134 for the shunt resistor to the heat dissipation section 133 for the MOS-FET, the heat from the shunt resistor R1 can be distributed between the heat dissipation section 134 for the shunt resistor and the heat dissipation section 133 for the MOS-FET, thereby improving the heat dissipation characteristics of the shunt resistor R1.

[0060] Furthermore, a through-via 101 filled with grease 140 is provided between the shunt resistor R1 and the MOS-FET 120a, and the grease 140 is in contact with the MOS-FET heat dissipation section 133 and the shunt resistor heat dissipation section 134. Therefore, heat generated from the shunt resistor R1 and the MOS-FET 120a can be efficiently dissipated from the MOS-FET heat dissipation section 133 and the shunt resistor heat dissipation section 134. In addition, because the MOS-FET heat dissipation section 133 and the shunt resistor heat dissipation section 134 are connected, heat generated from the shunt resistor R1 and the MOS-FET 120a can be effectively distributed between the MOS-FET heat dissipation section 133 and the shunt resistor heat dissipation section 134.

[0061] Furthermore, the through-via arrangement region Rb between the MOS-FET 120a and the shunt resistor R1 has a portion that overlaps with both the heat dissipation section 133 for the MOS-FET and the heat dissipation section 134 for the shunt resistor in a plan view. This allows the heat generated from the shunt resistor R1 and the MOS-FET 120a to be more effectively distributed to the heat dissipation section 133 for the MOS-FET and the heat dissipation section 134 for the shunt resistor. In addition, since the heat generated from the shunt resistor R1 can be efficiently dissipated, there is no need to lower the resistance value of the shunt resistor R1 to suppress heat generation. Therefore, it is possible to prevent an excessive decrease in the motor current resolution that would occur if the resistance value of the shunt resistor R1 were lowered.

[0062] Furthermore, through vias 101a filled with grease 140A are provided between adjacent MOS-FETs 120a to 120d, and the grease 140A is in contact with the MOS-FET heat dissipation section 133. Therefore, the heat generated from each MOS-FET 120a to 120d can be efficiently dissipated from the MOS-FET heat dissipation section 133. In addition, since the MOS-FET heat dissipation section 133 and the shunt resistor heat dissipation section 134 are connected, the heat generated from each MOS-FET 120a to 120b can be effectively distributed between the MOS-FET heat dissipation section 133 and the shunt resistor heat dissipation section 134.

[0063] Furthermore, since the shunt resistor R1 and MOS-FETs 120a to 120d generate heat when energized, they are generally placed at a predetermined distance (the required distance between components) to prevent them from being affected by each other's heat. In contrast, in the embodiment described above, through-vias 101 are placed between adjacent MOS-FETs 120a to 120d, and between MOS-FET 120a and shunt resistor R1, and the inside of the through-vias 101 is filled with grease 140 in contact with either the MOS-FET heat dissipation section 133 or the shunt resistor heat dissipation section 134. In this way, the heat generated from the MOS-FETs 120a to 120d and shunt resistor R1 can be dissipated through the through-vias 101 to the MOS-FET heat dissipation section 133 or the shunt resistor heat dissipation section 134. As a result, the distance between the shunt resistor R1 and MOS-FET 120a (required distance between components) and the distance between adjacent MOS-FETs 120a to 120d (required distance between components) can be shortened, making it possible to miniaturize the control device 60.

[0064] Furthermore, by positioning the heat dissipation section 134 for the shunt resistor closer to the edge of the substrate 100 where the curvature is less than that of the heat dissipation section 133 for the MOS-FET, the distance of the heat dissipation section 134 to the substrate 100 can be reduced. This makes it possible to reduce the thickness of the grease 140B, thereby further improving the heat dissipation performance of the shunt resistor R1.

[0065] Furthermore, by connecting the heat dissipation section 134 for the shunt resistor and the heat dissipation section 133 for the MOS-FETs and using them together as a heat dissipation section for the shunt resistor R1 and MOS-FETs 120a to 120d, the weight of each of the heat dissipation sections 134 and 133 for the shunt resistors can be reduced.

[0066] Furthermore, by not reducing the resistance value of the shunt resistor, it becomes unnecessary to use a high-performance CPU, thus reducing the cost of the electric power steering control device 60. In addition, in the above embodiment, the grease 140 used to fill the space between the upper surface 134a of the shunt resistor heat dissipation section 134 and the lower surface 100B of the substrate 100, and the space between the upper surface 133a of the MOS-FET heat dissipation section 133 and the lower surface 100B of the substrate 100, is used to fill the inside of the through-via 101 with heat dissipation grease. With this configuration, for example, inexpensive, small-sized components with low power ratings can be used as the heat-generating electronic components on the substrate, thereby enabling miniaturization and cost reduction.

[0067] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, in the embodiments described above, the heat dissipation section 134 for the shunt resistor is arranged in close contact with the heat dissipation section 133 for the MOS-FET, but the invention is not limited to this, and for example, as shown in Figure 8, the heat dissipation section for the shunt resistor may be connected to both the heat dissipation section for the MOS-FET and the substrate fixing section.

[0068] In Figure 8, the substrate fixing and heat dissipation structure 130A comprises a base portion 131, four substrate fixing portions 132a to 132d, a heat dissipation portion 133 for the MOS-FET, and a heat dissipation portion 134A for the shunt resistor. The heat dissipation portion 134A for the shunt resistor sandwiches the substrate 100 between itself and the shunt resistor R1, and is positioned on the base portion 131 such that it overlaps with the shunt resistor R1 in a plan view. The heat dissipation portion 134A for the shunt resistor is also in contact with the substrate fixing portion 132a. The heat dissipation portion 134A for the shunt resistor and the heat dissipation portion 133 for the MOS-FET are connected via a connection portion 135 provided on the base portion 131. In a plan view, the heat dissipation portion 134A for the shunt resistor is closer to the line connecting the substrate fixing portion 132a and the substrate fixing portion 132b than the heat dissipation portion 133 for the MOS-FET. Furthermore, the heat dissipation section 134A for the shunt resistor is closer to side 100ab (the side connecting the corner of the substrate 100 where the through-hole 100a is provided and the corner of the substrate 100 where the through-hole 100b is provided) than the heat dissipation section 133 for the MOS-FET.

[0069] Furthermore, the heat dissipation section 134A for the shunt resistor is located between the line connecting the substrate fixing section 132a and the substrate fixing section 132b, and the line connecting the substrate fixing section 132c and the substrate fixing section 132d, and is provided in the vicinity of the substrate fixing section 132a. As shown in the modified example in Figure 8, if the heat dissipation section 134A for the shunt resistor is placed closer to the substrate fixing section 132a compared to the above embodiment, the heat dissipation section 134A for the shunt resistor and the substrate 100 will face each other in a portion where the amount of warping of the substrate is smaller. This allows the thickness of the grease 140B to be made thinner, thereby further improving heat dissipation.

[0070] Furthermore, the number of through-vias 101a placed between adjacent MOS-FETs 120a and 120b, and the number of through-vias 101b placed between MOS-FET 120a and shunt resistor R1, can be changed as appropriate. In addition, the shape of the opening of each through-via 101 is not limited to a circle, but can be changed as appropriate to, for example, a rectangle or a triangle.

[0071] Furthermore, in the above embodiment, MOS-FETs 120a to 120d are used as semiconductor elements for switching the current flowing through the brushed motor 20, but the invention is not limited to these. For example, semiconductor elements other than MOS-FETs 120a to 120d that have two states, an on state and an off state, may also be used.

[0072] Furthermore, although the circuit configuration of the current detection circuit 110 is shown in Figure 9, it is not limited to this configuration, and other circuit configurations of the current detection circuit may also be used.

[0073] Furthermore, the embodiments described above, the contents described above, and the contents described in the modified examples above may be combined as appropriate.

[0074] The present invention is widely applicable to control devices for electric power steering systems that have a heat dissipation structure related to the shunt resistor constituting the current detection circuit. [Explanation of Symbols]

[0075] 20: Brushed motor 60: Control Unit (EPS-ECU) (Control unit for electric power steering) 100: Circuit board 101: Through-beam 110: Current detection circuit 133: Heat dissipation section for MOS-FET (second heat sink) 134: Heat dissipation section for shunt resistor (first heat sink) 140: Grease (thermal grease) R1: Shunt resistor Rb: Through-via placement region (through-via formation region) R1, 120a~120d: Shunt resistor, MOS-FET (heat-generating electronic component)

Claims

1. An electric power steering control device comprising a current detection circuit including a shunt resistor for detecting the motor current of a brushed motor, and controlling the brushed motor based on the motor current detected by the current detection circuit to control the steering of the vehicle, Multiple heat-generating electronic components including the aforementioned shunt resistor, A substrate in which the shunt resistor is surface-mounted at a predetermined end of the main surface, and other heat-generating electronic components different from the shunt resistor are surface-mounted at a specific location on the main surface, and a predetermined location on the predetermined end side of the shunt resistor is fixed to the object to be fixed, A first heat sink is provided, which sandwiches the substrate between the shunt resistor and the substrate, and is positioned such that, in a plan view from the vertical, the substrate overlaps with the shunt resistor, and absorbs and dissipates heat from the shunt resistor. A second heat sink is provided, which sandwiches the substrate between the other heat-generating electronic components, and is positioned such that it overlaps with the other heat-generating electronic components in a plan view, and which absorbs and dissipates heat from the other heat-generating electronic components. In the plan view, through vias that penetrate the substrate are arranged between the heat-generating electronic components, The thermal grease filled into the through via, Equipped with, The first heat sink and the second heat sink are connected, The heat dissipation grease extends from the through via toward one of the first heat sink and the second heat sink, and is in contact with the heat sink. The substrate is rectangular in its plan view and has through holes at each of its four corners for fixing to the object to be fixed. The control device for electric power steering is characterized in that the predetermined end of the main surface is located in a region near one side of the substrate that is within a predetermined distance from that side, and is set on a region connecting two through holes located at both ends of that side.

2. A through-via formation region is provided between the shunt resistor and the other heat-generating electronic component on the main surface of the substrate, where the through-via is formed. The control device for electric power steering according to claim 1, characterized in that the through-via formation region has a portion that overlaps with both the first heat sink and the second heat sink in the plan view.

3. A control device for electric power steering, comprising a current detection circuit including a shunt resistor for detecting the motor current of a brushed motor, and controlling the brushed motor based on the motor current detected by the current detection circuit to control the steering of the vehicle, Multiple heat-generating electronic components including the aforementioned shunt resistor, A substrate in which the shunt resistor is surface-mounted at a predetermined end of the main surface, and other heat-generating electronic components different from the shunt resistor are surface-mounted at a specific location on the main surface, and a predetermined location on the predetermined end side of the shunt resistor is fixed to the object to be fixed, A first heat sink is provided, which sandwiches the substrate between the shunt resistor and the substrate, and is positioned such that, in a plan view from the vertical, the substrate overlaps with the shunt resistor, and absorbs and dissipates heat from the shunt resistor. A second heat sink is provided, which sandwiches the substrate between the other heat-generating electronic components, and is positioned such that it overlaps with the other heat-generating electronic components in a plan view, and which absorbs and dissipates heat from the other heat-generating electronic components. In the plan view, through vias that penetrate the substrate are arranged between the heat-generating electronic components, The thermal grease filled into the through via, Equipped with, The first heat sink and the second heat sink are connected, The heat dissipation grease extends from the through via toward one of the first heat sink and the second heat sink, and is in contact with the heat sink. A through-via formation region is provided between the shunt resistor and the other heat-generating electronic component on the main surface of the substrate, where the through-via is formed. The through-via formation region has a portion that overlaps with both the first heat sink and the second heat sink in the plan view. The substrate is rectangular in its plan view and has through holes at each of its four corners for fixing to the object to be fixed. The control device for electric power steering is characterized in that the through-via formation region is a region near one side of the substrate that is within a predetermined distance from one side of the substrate, and is set on a region connecting two through-holes located at both ends of the said side.

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