阅读说明：本技术 电动助力转向用的电子控制单元 (Electronic control unit for electric power steering ) 是由 原田一树 木暮荣和 阿部信吾 于 2019-03-28 设计创作，主要内容包括：本发明提供电动助力转向用的电子控制单元,该电动助力转向用的电子控制单元与电动马达一体形成,其中,所述电子控制单元具有从外部接受电源供给的一个电路板,所述电路板的一面侧的基板区域具有安装有电源系统电路部件的区域和安装有控制系统电路部件的区域,在与安装有所述电源系统电路部件的区域对应的所述电路板的另一面侧的区域形成有导体图案,在与安装有所述控制系统电路部件的区域对应的所述电路板的另一面侧的区域安装有至少一部分的控制系统电路部件,所述导体图案至少包含所述电源系统电路部件的电源图案和接地端图案,所述电源图案和所述接地端图案包含多个电源图案和多个接地端图案。(The present invention provides an electronic control unit for electric power steering, which is formed integrally with an electric motor, wherein the electronic control unit has a circuit board for receiving power supply from outside, a substrate region on one surface side of the circuit board has a region where power system circuit components are mounted and a region where control system circuit components are mounted, a conductor pattern is formed in a region on the other surface side of the circuit board corresponding to a region where the power system circuit component is mounted, at least a part of the control system circuit components are mounted in a region on the other surface side of the circuit board corresponding to a region in which the control system circuit components are mounted, the conductor pattern includes at least a power supply pattern and a ground terminal pattern of the power supply system circuit part, the power supply pattern and the ground terminal pattern include a plurality of power supply patterns and a plurality of ground terminal patterns.)

1. An electronic control unit for electric power steering, which is formed integrally with an electric motor,

the electronic control unit has a circuit board receiving power supply from the outside,

the substrate area on one surface side of the circuit board has an area where power system circuit components are mounted and an area where control system circuit components are mounted,

a conductor pattern is formed in a region on the other surface side of the circuit board corresponding to a region where the power system circuit component is mounted,

at least a part of the control system circuit components are mounted in a region on the other surface side of the circuit board corresponding to a region in which the control system circuit components are mounted,

the conductor pattern includes at least a power supply pattern and a ground terminal pattern of the power supply system circuit part,

the power supply pattern and the ground terminal pattern include a plurality of power supply patterns and a plurality of ground terminal patterns.

2. The electronic control unit for electric power steering according to claim 1,

heat is conducted from one surface side of the circuit board to the other surface side of the circuit board via a metal penetration member provided on the circuit board for each power supply system circuit component, and the conducted heat is dissipated by the conductor pattern.

3. The electronic control unit for electric power steering according to claim 1,

the case of the electric motor is used as an external heat radiator, and heat generated by the power supply system circuit component is conducted from the conductor pattern to a heat receiving surface formed in a part of the external heat radiator so as to correspond to the shape of the conductor pattern.

4. The electronic control unit for electric power steering according to claim 3,

the heat receiving surface is formed in a planar shape so as to face the conductor pattern.

5. The electronic control unit for electric power steering according to claim 1,

the conductor pattern also includes a power supply output pattern toward the electric motor.

6. The electronic control unit for electric power steering according to claim 5,

the areas of regions corresponding to the positive-side pattern and the negative-side pattern of the conductor pattern, which generate the three-phase bridge circuit for driving the alternating-current power supply of the electric motor, are made larger than the area of the power supply output pattern toward the electric motor.

7. The electronic control unit for electric power steering according to claim 1,

the sum total area of the plurality of power patterns is greater than the sum total area of the plurality of ground terminal patterns.

8. The electronic control unit for electric power steering according to claim 5,

the sum total area of the plurality of power supply patterns is greater than the sum total area of the plurality of ground terminal patterns, and the sum total area of the plurality of ground terminal patterns is greater than the area of the power supply output pattern.

9. The electronic control unit for electric power steering according to claim 1,

no component is mounted in a region on the other surface side of the circuit board corresponding to a region where the power supply system circuit component is mounted.

10. The electronic control unit for electric power steering according to claim 6,

an output terminal of the three-phase bridge circuit is arranged on a region side of the circuit board where the power supply system circuit component is mounted.

11. The electronic control unit for electric power steering according to claim 1,

the power supply patterns and the ground terminal patterns include 3 or more of the power supply patterns and 4 or more of the ground terminal patterns.

12. The electronic control unit for electric power steering according to claim 5,

the power output patterns include 6 or more power output patterns.

13. An electric power steering apparatus for assisting a steering wheel operation of a driver of a vehicle or the like, characterized in that,

the electric power steering device includes:

a torque sensor that detects torque generated by the steering wheel operation;

an electronic control unit for electric power steering according to any one of claims 1 to 12; and

and an electric motor that is driven by the electronic control unit for electric power steering in accordance with the torque detected by the torque sensor.

Technical Field

The present invention relates to an electric power steering apparatus, and more particularly to a heat dissipation mechanism of an electronic control unit of an electric power steering apparatus.

Background

A vehicle such as an automobile is mounted with an electric power steering apparatus including an electric motor that generates an assist torque in response to a steering wheel operation of a driver, a control device for the electric motor, and the like. With the trend toward miniaturization of the entire electric power steering apparatus, heat dissipation from the control apparatus and the like becomes important.

For example, in japanese laid-open patent publication No. 2016-36246, a frame member of a drive device is used as an outer contour of an electric motor, and heat generated in a heat generating element is radiated as a heat sink, so that the heat generating element, an electronic component, and the like are disposed in a projection region in the axial direction of a cylindrical portion of a rotating electric machine, thereby achieving miniaturization. The motor control device disclosed in japanese laid-open patent publication No. 2017-184294 has the following structure: the shunt resistor is disposed at a position closer to the outer periphery of the circuit board than the power semiconductor element, and radiates heat to the frame via a thermally connected circuit pattern and a metal pattern formed on the outer periphery surface layer of the circuit board.

In the motor control device disclosed in japanese laid-open patent publication No. 2015-180155, heat generated from a switching element, a microcomputer, and the like is transmitted to a heat dissipation base in contact with the back surface of a circuit board, and further, heat is dissipated to the outside through a case main body (housing) and an actuator case, thereby integrally configuring a power supply module and a control module and realizing miniaturization of the motor control device.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open gazette: japanese laid-open patent publication No. 2016-36246

Patent document 2: japanese laid-open gazette: japanese laid-open patent publication No. 2017-184294

Patent document 3: japanese laid-open gazette: japanese laid-open patent publication No. 2015-180155

Disclosure of Invention

Problems to be solved by the invention

In the devices described in japanese laid-open patent publication No. 2016-36246 and 2017-184294, the control unit and the power supply unit are disposed on both sides of the substrate, and the heat generating component is cooled by bringing the back surface thereof into contact with the heat sink. In particular, in the case of japanese laid-open patent publication No. 2017-184294, even if the mounting density of the components is increased by the double-sided arrangement, since the power semiconductor element and the shunt resistor are cooled separately, the arrangement of the components is restricted, and the miniaturization of the device is restricted.

On the other hand, since japanese laid-open patent publication No. 2015-180155 is a drive control device applied to an electric actuator such as a brake booster, heat generated from the power module is also lower than heat generated from a power supply unit of the electric power steering apparatus. Therefore, the heat dissipation structure of japanese laid-open patent publication No. 2015-180155 cannot be directly applied to heat dissipation in the electric power steering apparatus.

Since the electric power steering apparatus always operates and the heat generating component continuously generates heat, the conventional heat dissipation mechanism cannot sufficiently secure a heat dissipation path. Therefore, when heat generated from the control unit of the electric power steering apparatus during steering of the steering wheel cannot be efficiently dissipated, overheating protection is applied, and the original purpose of the electric power steering apparatus such as assisting in steering of the steering wheel cannot be achieved.

The present invention has been made in view of the above problems, and an object of the present invention is to make heat dissipation in an electronic control unit of an electric power steering apparatus efficient, to eliminate a limitation of an assist operation due to heat, and to make the electric power steering apparatus compact.

Means for solving the problems

The above object is achieved by the following means. That is, the circuit board according to the exemplary 1 st aspect of the present invention is characterized in that a circuit component is mounted on one surface side of the circuit board, and a conductor pattern for radiating heat generated by the circuit component from the other surface side is formed on the other surface side of the circuit board.

An exemplary 2 nd aspect of the present invention is an electronic control unit for electric power steering integrally formed with an electric motor, the electronic control unit including one circuit board to which power is supplied from outside, wherein heat generated from a power supply system circuit component of the electric power steering disposed on one surface side of the circuit board is dissipated by a conductor pattern formed on the other surface side of the circuit board.

An exemplary 3 rd aspect of the present invention is an electric power steering apparatus for assisting a steering wheel operation of a driver of a vehicle or the like, the electric power steering apparatus including: a torque sensor that detects torque generated by the steering wheel operation; the electronic control unit for electric power steering according to claim 2; and an electric motor that is driven by the electronic control unit for electric power steering in accordance with the torque detected by the torque sensor.

Effects of the invention

According to the present invention, in the electronic control unit of the electric power steering apparatus, high heat radiation efficiency can be obtained for the heat generating component, and limitation of the assist operation due to overheat protection can be suppressed.

Drawings

Fig. 1 is a schematic configuration of a steering system including an electric power steering apparatus according to an embodiment.

Fig. 2 is an exploded perspective view of the electric power steering apparatus integrated with the electronic control unit according to the embodiment.

Fig. 3 is an external view of the control unit on the front side of the wiring board.

Fig. 4 is an external view of the control unit from the back side of the wiring board.

Fig. 5 is a circuit configuration diagram of a power supply unit of the control unit.

Fig. 6a is a graph showing a temperature increase rate of the control unit of the electric power steering apparatus before a heat dissipation countermeasure.

Fig. 6b is a diagram showing the temperature increase rate of the control unit of the electric power steering apparatus according to the embodiment after the heat dissipation countermeasure.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a schematic configuration of a steering system including an electric power steering apparatus according to an embodiment of the present invention. The steering system 1 includes a steering wheel 2 as a steering member, a rotating shaft 3 connected to the steering wheel 2, a pinion gear 6, a rack shaft 7, an electric power steering apparatus 10, and the like.

The electric power steering apparatus 10 is constituted by an electronic control unit 20, an electric motor 15, and the like. A torque sensor 9 for detecting a steering torque when the steering wheel 2 is operated is provided on the rotary shaft 3, and the detected steering torque is transmitted to the electronic control unit 20.

The rotary shaft 3 is engaged with a pinion 6 provided at a front end thereof. The rotational motion of the rotary shaft 3 is converted into linear motion of the rack shaft 7 by the pinion 6, and the pair of wheels 5a and 5b provided at both ends of the rack shaft 7 are steered to an angle corresponding to the amount of displacement of the rack shaft 7.

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

Fig. 2 is an exploded perspective view of an electric power steering apparatus in which an electric power steering electronic control unit according to an embodiment of the present invention is mounted and integrated with the electronic control unit. In the electric power steering apparatus 10 shown in fig. 2, a heat sink 13 is disposed in an axial upper portion of an electric motor (brushless motor) 15 covered by a motor cover 14, and a Control Unit (Electronic Control Unit: ECU)20 is disposed above the heat sink 13 and on an axial opposite output side of the electric motor 15, and is fixed to the heat sink 13 by a screw or the like.

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

The upper portion of the control unit 20 is covered with a unit cover 12 made of metal. The external connector 16 is a connection terminal for a power supply to the electric motor 15, a control signal to the control unit 20, and the like, is covered with a connector housing, and is 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 radiator 13, the heat radiation region (heat radiation portion) 27 on the back surface of the substrate of the control unit 20 and the heat receiving region (heat receiving portion) 29 provided in a planar shape on the upper portion of the radiator 13 are in a positional relationship in which they face each other with a gap at a predetermined interval therebetween. By filling the space with a thermally conductive insulating resin, heat generated in the heat generating components of the control unit 20 is conducted to the circuit board pattern or the like disposed in the heat dissipation region 27, and is dissipated from the circuit board pattern or the like to the heat sink 13.

The heat dissipation region 27 on the substrate and the heat receiving region 29 on the heat sink have substantially the same shape and area, but in consideration of the heat dissipation effect and efficiency, the area of the heat receiving region 29 is preferably larger than the area of the heat dissipation region 27. In addition, the heat receiving region 29 may be designed in consideration of the shape of the heat dissipation region 27 on the substrate, and the heat receiving region 29 may be formed in correspondence with the shape of the heat dissipation region 27.

Fig. 3 is an external view of the wiring board 22 of the control unit 20 from the top (on the unit cover 12 side). Fig. 4 is an external view of the rear surface (electric motor 15 side) of the wiring board 22 of the control unit 20 in a plan view. In addition, fig. 4 is a view when the back surface is seen in perspective from the front surface side (fig. 3) in order to easily understand the correspondence between the front surface area and the back surface area of the wiring board 22.

The front surface 23 of the wiring board 22 shown in fig. 3 has the following areas: a region (hereinafter, referred to as a control unit 23a) in which control system devices such as signal processing components for controlling the electric power steering apparatus and various sensors such as a current sensor are mounted; and a region (hereinafter, referred to as a power supply unit 23b, but also referred to as a power supply module as appropriate) in which an FET bridge circuit including FETs 1 to 6, switching FETs (FETs 9 to 11) for supplying a driving current to the motor, electrolytic capacitors C1 to C3, and the like are mounted.

In the control unit 20, the control section 23a and the power supply section 23b occupy substantially one half of the entire area of the wiring board 22, respectively, the entire area being substantially bisected by the control section 23a and the power supply section 23 b.

By dividing the area of the wiring board 22 into the control unit 23a and the power supply unit 23b in this way, the control system device can be mounted not only on the control unit 23a of the board front surface 23 but also on the control unit 25a of the board rear surface 25 as shown in fig. 4, for example, on the microprocessor 31 for controlling the electric power steering apparatus. Thus, since components related to the control system of one circuit board can be mounted on both sides of the substrate, the degree of freedom in design can be improved in a substrate having a limited area.

Fig. 5 is a circuit configuration diagram of the power supply unit 23b of the control unit 20 shown in fig. 3 and the like. In fig. 5, B + and B-are input terminals of the positive electrode potential and the negative electrode potential of the driving power source such as the electric motor 15, and are connected to the external connector 16. A noise filter including a coil 56 and an electrolytic capacitor 53 is provided on the power supply input side of the power supply unit 23 b. The noise filter can absorb noise included in the power supply supplied to the control unit 20, thereby smoothing the power supply voltage.

The coil 56 is a common mode coil composed of 2 coils, for example. The electrolytic capacitor 53 is constituted by 3 electrolytic capacitors C1 to C3 connected in parallel as shown in fig. 3, for example.

The power supply unit 23b as a power supply module includes FETs 7, 8, a switching circuit 54, and the like, wherein the FETs 7 and 8 function as semiconductor relays capable of cutting off power when a power supply voltage from a battery is abnormal or the like, and the switching circuit 54 supplies a drive current (3-phase alternating current) to the electric motor 15. The switching circuit 54 is a 3-phase inverter circuit (FET bridge circuit) composed of 6 FETs 1 to 6.

For example, the gates of 6 FETs 1 to 6 constituting the switching circuit 54 are driven to be turned on or off by a signal from a control circuit (not shown) including a microcomputer, a pre-driver, and the like. The current of each phase U, V, W generated by the on/off control is a drive current supplied to the electric motor 15 via the output terminal section 57 including the 3 terminals U, V, W.

FET 1 and FET 2 are connected between a positive power supply line L1 and a negative potential line (GND) L2, and generate a U-phase current flowing through a U-winding of the electric motor 15. The shunt resistor R1 provided between the FET 2 and the GND line L2 functions as a current sensor for detecting the U-phase current (the U-phase current can be obtained from the potential of the connection node between the FET 2 and the shunt resistor R1). Further, an FET 9 as a semiconductor relay capable of cutting off the U-phase current is provided between the connection node of the FETs 1 and 2 and the output terminal U to the electric motor 15.

Similarly, FET 3 and FET 4 are connected between a positive power supply line L1 and a negative potential (GND) line L2, and generate a V-phase current flowing through a V-coil of electric motor 15. The shunt resistor R2 provided between the FET 4 and the GND line L2 functions as a current sensor for detecting the V-phase current (the V-phase current can be obtained from the potential of the connection node between the FET 4 and the shunt resistor R2). Further, the FET 10 provided between the connection node of the FETs 3 and 4 and the output terminal V to the electric motor 15 functions as a semiconductor relay capable of cutting off the V-phase current.

FET 5 and FET 6 are connected between a positive power supply line L1 and a negative potential (GND) line L2, and generate a W-phase current flowing through a W-winding of electric motor 15. As a current sensor for detecting the W-phase current, a shunt resistor R3 (the W-phase current can be obtained from the potential of the connection node between the FET 6 and the shunt resistor R3) is provided between the FET 6 and the GND line L2. Further, an FET 11 as a semiconductor relay capable of cutting off the W-phase current is provided between a connection node of the FETs 5 and 6 and the output terminal W to the electric motor 15.

Next, a heat dissipation mechanism in the electric power steering apparatus mounted with the electronic control unit for electric power steering according to the present embodiment will be described in detail.

The area of the substrate back surface 25 of the control unit 20 shown in fig. 4 can be divided into a control portion 25a corresponding to the control portion 23a and a power supply portion 25b corresponding to the power supply portion 23 b. The region surrounded by the broken line in the power supply portion 25b is a heat dissipation region 27, and has an area and a shape corresponding to the arrangement region of the component (heat generating component) having a large amount of heat generation in the power supply portion 23b mounted on the substrate front surface 23 side in fig. 3.

In the heat dissipation region 27 of the wiring board 22, a heat conductive member (heat conductive member) penetrating the wiring board 22, that is, coin-shaped copper insert having a predetermined diameter is embedded in accordance with the mounting position of the FET bridge circuit or the switching FET, which generates a large amount of heat, in particular. Specifically, as shown in fig. 4, copper-embedded IL1 to IL11 are disposed directly below each of FET 1 to FET 11. The heat generated in the FETs 1 to 11 is radiated to the back surface 25 side of the wiring board 22 through the copper-embedded portions.

Further, the following structure is adopted in the wiring board 22: a power supply pattern and a Ground (GND) pattern for supplying power to heat-generating components such as FETs 1 to 9 are disposed in the heat dissipation region 27, and heat generated in the heat-generating components is also dissipated from these patterns. This is the following structure: in the case of a large FET, it is possible to cope with heat dissipation directly below the component by copper embedding, but in the case of a small FET, the heat dissipation area becomes small due to the restriction on the substrate area caused by the miniaturization of the control unit, so that heat dissipation is insufficient only by copper embedding, and heat generated from the heat generating component is also transferred to the power supply pattern and the GND pattern, and heat dissipation efficiency is improved by causing the power supply pattern and the GND pattern to participate in heat dissipation.

Unlike a normal wiring pattern, the power supply pattern and the Ground (GND) pattern in the wiring board 22 are arranged in a region capable of securing an area as large as possible in the heat dissipation region 27, for example, as in the power supply patterns PW1 to PW3 and GND patterns G1 to G4 shown in fig. 4.

The wiring board 22 may be any of a double-sided substrate and a multilayer substrate. In the case of a double-sided substrate, the power supply pattern and the GND pattern are arranged on the back surface (solder surface) of the substrate. On the other hand, in the case of a multilayer substrate, by disposing these power supply patterns and GND patterns also in the inner layer, a pattern having a large area and low resistance (low impedance) can be realized, and heat dissipation efficiency can be improved accordingly.

When the power supply pattern and the GND pattern correspond to the circuit configuration diagram of fig. 5, a large current flows through the power supply line L1 and the Ground (GND) terminal L2, which are paths for supplying power to the FETs 1 to 6 constituting the switch circuit 54 of fig. 5, in the power supply portion 23b of the control unit 20. The power supply line L1 is arranged in power supply patterns PW1 to PW3 having a large pattern surface in the heat dissipation area 27 of the wiring board 22 in fig. 4, and the GND line L2 is arranged in GND patterns G1 to G4 having a large pattern surface in the heat dissipation area 27 in fig. 4.

As wiring patterns other than the power supply pattern and the ground terminal (GND) pattern, the following structure is adopted: the pattern on the wiring board 22 corresponding to the line L3 (the path from the connection node of the FETs 1 and 2 to the FET 9), the line L4 (the path from the connection node of the FETs 3 and 4 to the FET 10), the line L5 (the path from the connection node of the FETs 5 and 6 to the FET 11), the line L6 (the power output pattern from the FET 9 to the output terminal U toward the electric motor 15), the line L7 (the power output pattern from the FET 10 to the output terminal V toward the electric motor 15), and the line L8 (the power output pattern from the FET 11 to the output terminal W toward the electric motor 15) shown in the circuit configuration diagram of fig. 5 is also arranged in the heat dissipation region 27 as a path through which a current flows based on the power supply line L1 and the ground terminal (GND) line L2, and heat from the heat dissipation component is also dissipated from the pattern.

In the control unit 20, the areas of the patterns corresponding to the positive side pattern L1 and the negative side pattern L2 of the three-phase bridge circuit are formed larger than the areas of the power output patterns L3 to L8 toward the electric motor 15. More specifically, in the following relationship: (areas of the power supply patterns PW1 to PW 3) > (areas of the GND patterns G1 to G4) > (areas of the power supply output patterns L3 to L8 facing the electric motor).

In the electric power steering apparatus of the present embodiment, as shown in fig. 4 and the like, the output terminal portion 57 for each phase current of U, V, W supplied to the electric motor 15 is disposed on the power supply portion 25b side. This can shorten the wiring distance from the 3-phase inverter circuit and the like to the electric motor 15, and reduce the power loss with a lower resistance value due to a shorter pattern length of the power supply path.

The number, arrangement position, area, and the like of the heat generating components (FETs and the like), the embedded copper, the power supply pattern, and the ground terminal (GND) pattern in the circuit board shown in fig. 3, 4, and the like are examples, and can be changed as appropriate according to the specification of the electric power steering apparatus.

Fig. 6a and 6b show the heat radiation effect in the control unit of the electric power steering apparatus of the present embodiment. The vertical axis represents the temperature increase rate (%), and the horizontal axis represents the elapsed time. Here, when the temperature of the substrate rises due to heat from the heat generating component, the temperature of the electrolytic capacitor also rises due to the influence thereof, and therefore, of the components mounted on the power supply unit 23b, Aluminum Electrolytic Capacitors (AEC) C1 to C3, which have relatively low maximum use temperatures of, for example, 125 ℃, are used as the temperature measurement targets.

Fig. 6a shows the result of measuring the temperature increase rate of the body and the terminals of the electrolytic capacitor mounted on the substrate when a constant current is applied to the control unit before the heat dissipation countermeasure, and the result of measuring 1 electrolytic capacitor that can be measured out of 3 electrolytic capacitors. AEC1 in fig. 6a is the temperature increase rate of the main body of the electrolytic capacitor, and AEC2 is the terminal temperature increase rate of the electrolytic capacitor.

Fig. 6b shows the measurement results of the temperature increase rates of the electrolytic capacitors C1 to C3 mounted in the control unit of the electric power steering apparatus according to the present embodiment, after taking measures against heat dissipation, in which heat from the heat generating components is dissipated via the power supply pattern and the Ground (GND) pattern. AEC3 of fig. 6b corresponds to the bulk temperature rise rate of each of the 3 electrolytic capacitors, and AEC4 corresponds to the terminal temperature rise rate of each of the 3 electrolytic capacitors.

In comparison with fig. 6a and 6b, the electrolytic capacitor in the control unit of the present embodiment, which has been subjected to the heat dissipation measure for dissipating heat via the power supply pattern and the GND pattern, has a blunted tendency of temperature increase compared to the electrolytic capacitor in the conventional control unit before the measure. This indicates that the heat radiation countermeasure in the control unit of the present embodiment achieves the heat radiation effect.

For example, the temperature increase of the main body of the electrolytic capacitor can be suppressed to 348% after the countermeasure, while the temperature increase rate is 412% before the countermeasure. In addition, regarding the increase rate of the terminal temperature of the electrolytic capacitor directly connected to the power supply pattern and the GND pattern provided on the substrate, the increase rate can be suppressed from 476% before the countermeasure to 280% after the countermeasure for the positive side terminal. Similarly, the temperature rise of the negative terminal can be suppressed from 356% before the countermeasure to 280% after the countermeasure.

As described above, in the electric power steering apparatus of the present embodiment, the power supply pattern and the Ground (GND) pattern that supply power to the heat generating component mounted on the wiring board of the control unit are arranged in the heat dissipation area provided on the wiring board, and the heat conduction path from the heat dissipation area to the heat sink of the electric motor is provided. Thus, heat from the heat generating component can be dissipated through the power supply pattern and the Ground (GND) pattern, and high heat dissipation efficiency can be achieved for the heat generating component.

Further, since the copper-embedded board penetrating the wiring board is disposed directly below each of the heat generating components located in the heat dissipation area, effective heat conduction and heat dissipation by the copper-embedded board can be performed in addition to heat dissipation by the power supply pattern and the GND pattern.

With the above configuration, heat can be efficiently radiated in the electronic control unit for electric power steering integrally formed with the electric motor, and the design of the heat capacity including the electric motor is facilitated. Further, when the vehicle is steered, particularly when static steering of the assist steering wheel by the power steering is required more than during traveling, heat can be efficiently radiated, so that it is possible to avoid suspension of the operation of the electric motor due to overheating in the electric power steering apparatus, and to continue necessary assist.

Description of the reference symbols

1: a steering system; 2: a steering wheel; 3: a rotating shaft; 4: a reduction gear; 6: a pinion gear; 7: a rack shaft; 10: an electric power steering apparatus; 12: a unit cover; 13: a heat sink; 15: an electric motor; 16: an external connector; 20: an electronic control unit; 22: a wiring board; 23: a front surface of the substrate; 23a, 25 a: a control unit; 23b, 25 b: a power supply unit; 25: a back surface of the substrate; 27: a heat release region (heat release section); 29: a heat receiving region (heat receiving unit); 31: a microprocessor; 53: an electrolytic capacitor; 54: a switching circuit; 56: a coil; 57: an output terminal section; C1-C3: an electrolytic capacitor; G1-G4: a GND pattern; IL 1-IL 11: embedding copper; l1: a power line; l2: a Ground (GND) line; PW 1-PW 3: a power supply pattern.