JP7570692B2 - Electric drive device and electric power steering device - Google Patents

Description

This disclosure relates to an electric drive device and an electric power steering device equipped with an electronic control device that controls the rotation of a motor.

An electric power steering device that generates auxiliary steering torque using a motor is equipped with an electronic control device that controls the motor. For example, Patent Document 1 describes a drive device that allows electronic components to be densely mounted on a board.

In the electric drive device of Patent Document 1, the motor, electronic control device, and connector are arranged in that order along the axial direction parallel to the motor shaft. In the electric drive device of Patent Document 1, the connector is inserted and removed in the axial direction, so the size increases in the axial direction.

In contrast, in the electric drive device of Patent Document 2, the direction of insertion and removal into the connector is the radial direction of the motor shaft. As a result, the electric drive device of Patent Document 2 has a smaller axial size than the electric drive device of Patent Document 1.

JP 2016-034204 A JP 2017-092100 A International Publication No. 2012/056735

In the electric drive device of Patent Document 3, a hole is provided on the surface of the heat sink opposite the unevenness for embedding a choke coil.

In contrast, in the electric drive device of Patent Document 2, even if a hole is provided for embedding the choke coil of Patent Document 3, there are no irregularities that allow the choke coil to dissipate heat.

The present disclosure has been made in consideration of the above problems, and aims to provide an electric drive unit and an electric power steering unit that can more efficiently dissipate heat generated by the choke coil when electricity is passed through them while reducing the axial size.

In order to achieve the above object, an electric drive device according to one embodiment includes a motor including a shaft extending in the axial direction from the load side to the anti-load side, a motor rotor interlocking with the shaft, a motor stator including a stator core that rotates the motor rotor, and a housing that houses the motor rotor and the motor stator inside, a magnet provided on the anti-load side of the shaft, a heat sink provided on the anti-load side of the motor, an electronic control device including a circuit board arranged on the anti-load side of the heat sink and on which a choke coil is mounted, and a rotation angle sensor that is on an extension line of the magnet in the axial direction and attached to the circuit board, and a connector provided on the radial side of the shaft of the heat sink, the heat sink having a first surface, a second surface that is on the anti-load side of the first surface, and a first wall portion and a second wall portion that protrude from a wall of a step between the first surface and the second surface toward the connector, and the choke coil is inserted between the first wall portion and the second wall portion.

This reduces the size of the motor in the axial direction parallel to the shaft, making the electric drive device smaller. Heat from the choke coil is transferred to the first wall and the second wall, and dissipated from the first wall and the second wall.

As a preferred embodiment, the heat sink further includes a third wall portion connecting the first wall portion and the second wall portion, and the heat sink includes a recess surrounded on all four sides by a step wall between the bottom surface and the second surface between the first wall portion and the second wall portion, the first wall portion, the second wall portion, and the third wall portion. As a result, the five surfaces of the choke coil face the bottom surface and the four inner wall surfaces of the recess, thereby increasing the heat dissipation efficiency.

In a preferred embodiment, a heat dissipation material is filled between the first wall and the second wall. This makes it easier for the heat of the choke coil to be transferred to the housing.

In a preferred embodiment, the viscosity of the heat dissipation material is 200 Pa·s or more and 300 Pa·s or less. This allows the use of low-viscosity heat dissipation materials.

In a preferred embodiment, the heat dissipation material is in contact with at least one-third of the choke coil in the axial direction. This makes it easier for heat from the choke coil to be transferred to the housing.

In a preferred embodiment, the heat sink is located closer to the load than the first surface and further has a mounting surface on which the connector is mounted, and the second surface faces the circuit board and is a heat dissipation surface that dissipates heat from the circuit board. The step between the first surface and the second surface and the step between the first surface and the mounting surface can be used to bring the connector and the choke coil closer together.

In a preferred embodiment, the outside of the first wall portion and the second wall portion when viewed in the axial direction is the first surface. As a result, even if the heat dissipation material should climb over the first wall portion or the second wall portion, it can be received by the adjacent first surface, making it less likely that problems will occur due to the heat dissipation material.

In a preferred embodiment, the choke coil is located near the power terminal of the connector. This increases the efficiency of removing high-frequency components.

In a preferred embodiment, the heat sink has a hollow portion through which the shaft passes, and the hollow portion and the choke coil sandwich the second surface when viewed in the axial direction. This makes it difficult for the heat dissipation material to move from the housing portion to the hollow portion, even if the heat dissipation material overcomes the first wall portion or the second wall portion. As a result, the heat dissipation material is unlikely to adhere to the shaft or magnet.

In a preferred embodiment, the electric power steering device includes an electric drive unit that generates the auxiliary steering torque. This reduces the size of the motor in the axial direction parallel to the shaft and in the radial direction of the shaft, improving the freedom of arrangement of the electric power steering device.

This disclosure makes it possible to provide an electric drive device and an electric power steering device that can more efficiently dissipate heat generated by the choke coil when electricity is passed through them while reducing the axial size.

FIG. 1 is a perspective view that shows a schematic diagram of a vehicle equipped with an electric power steering device according to a first embodiment. FIG. 2 is a schematic diagram of the electric power steering device according to the first embodiment. FIG. 3 is a cross-sectional view that typically shows a cross section of the motor according to the first embodiment. FIG. 4 is a schematic diagram showing wiring of the motor according to the first embodiment. FIG. 5 is a schematic diagram showing the relationship between the motor and the ECU according to the first embodiment. FIG. 6 is a side view of the electric drive device according to the first embodiment. FIG. 7 is a plan view of the electric drive device according to the first embodiment. FIG. 8 is a cross-sectional view taken along the line VIII-VIII of FIG. FIG. 9 is a cross-sectional view taken along the line IX-IX of FIG. FIG. 10 is a cross-sectional view taken along the line XX of FIG. FIG. 11 is a cross-sectional view taken along the line XI-XI of FIG. FIG. 12 is a perspective view illustrating the electric drive device according to the first embodiment with the cover removed. FIG. 13 is a plan view of FIG. FIG. 14 is a perspective view illustrating the electric drive device according to the first embodiment with the cover and the circuit board removed. FIG. 15 is a plan view of FIG. 16 is a cross-sectional view taken along line XX of FIG. 7 according to the second embodiment. FIG. 17 is a perspective view illustrating the electric drive device according to the second embodiment with the cover and the circuit board removed. FIG. 18 is a schematic diagram of an electric power steering device according to the third embodiment. FIG. 19 is a side view showing an example of the arrangement of the ECU according to the third embodiment. 20 is a cross-sectional view taken along line XX of FIG. 7 according to the third embodiment. FIG. 21 is a perspective view illustrating the electric drive device according to the third embodiment with the cover and the circuit board removed.

The form (embodiment) for carrying out the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art would easily imagine and those that are substantially the same. Furthermore, the components described below can be combined as appropriate.

(Embodiment 1)
Fig. 1 is a perspective view showing a vehicle equipped with an electric power steering device according to embodiment 1. Fig. 2 is a schematic diagram of the electric power steering device according to embodiment 1. As shown in Fig. 1, a vehicle 101 is equipped with an electric power steering device 100. An overview of the electric power steering device 100 will be described with reference to Fig. 2.

The electric power steering device 100 includes, in the order of transmission of force from the driver (operator), a steering wheel 91, a steering shaft 92, a universal joint 96, an intermediate shaft 97, a universal joint 98, a first rack-and-pinion mechanism 99, and a tie rod 72. The electric power steering device 100 also includes a torque sensor 94 that detects the steering torque of the steering shaft 92, a motor 30, an electronic control device (hereinafter referred to as an ECU (Electronic Control Unit)) 10 that controls the motor 30, a reduction gear 75, and a second rack-and-pinion mechanism 70. A vehicle speed sensor 82, a power supply device 83 (e.g., an on-board battery), and an ignition switch 84 are provided on the vehicle body. The vehicle speed sensor 82 detects the traveling speed of the vehicle 101. The vehicle speed sensor 82 outputs the detected vehicle speed signal SV to the ECU 10 via CAN (Controller Area Network) communication. When the ignition switch 84 is on, the ECU 10 is supplied with power from the power supply device 83.

The electric drive device 1 includes a motor 30 and an ECU 10 fixed to the anti-load side of the shaft 31 of the motor 30. The electric drive device 1 may also include an adapter that connects the ECU 10 and the motor 30.

As shown in FIG. 2, the steering shaft 92 includes an input shaft 92A, an output shaft 92B, and a torsion bar 92C. One end of the input shaft 92A is connected to the steering wheel 91, and the other end is connected to the torsion bar 92C. One end of the output shaft 92B is connected to the torsion bar 92C, and the other end is connected to a universal joint 96. The torque sensor 94 detects the torsion of the torsion bar 92C to detect the steering torque applied to the steering shaft 92. The torque sensor 94 outputs a steering torque signal T corresponding to the detected steering torque to the ECU 10 via CAN communication. The steering shaft 92 rotates due to the steering force applied to the steering wheel 91.

The intermediate shaft 97 has an upper shaft 97A and a lower shaft 97B, and transmits the torque of the output shaft 92B. The upper shaft 97A is connected to the output shaft 92B via a universal joint 96. Meanwhile, the lower shaft 97B is connected to a first pinion shaft 99A of a first rack-and-pinion mechanism 99 via a universal joint 98. The upper shaft 97A and the lower shaft 97B are connected, for example, by a spline.

The first rack and pinion mechanism 99 has a first pinion shaft 99A, a first pinion gear 99B, a rack shaft 99C, and a first rack 99D. One end of the first pinion shaft 99A is connected to the lower shaft 97B via a universal joint 98, and the other end is connected to the first pinion gear 99B. The first rack 99D formed on the rack shaft 99C meshes with the first pinion gear 99B. The rotational motion of the steering shaft 92 is transmitted to the first rack and pinion mechanism 99 via the intermediate shaft 97. This rotational motion is converted into linear motion of the rack shaft 99C by the first rack and pinion mechanism 99. The tie rods 72 are connected to both ends of the rack shaft 99C.

The motor 30 generates an auxiliary steering torque to assist the driver in steering. The motor 30 may be a brushless motor or a brush motor having brushes and a commutator.

The ECU 10 includes a rotation angle sensor 23a. The rotation angle sensor 23a detects the rotation phase of the motor 30. The ECU 10 acquires a rotation phase signal of the motor 30 from the rotation angle sensor 23a, acquires a steering torque signal T from the torque sensor 94, and acquires a vehicle speed signal SV of the vehicle 101 from the vehicle speed sensor 82. The ECU 10 calculates an auxiliary steering command value of the assist command based on the rotation phase signal, the steering torque signal T, and the vehicle speed signal SV. The ECU 10 supplies a current to the motor 30 based on the calculated auxiliary steering command value.

The reduction gear 75 includes a worm shaft 75A that rotates integrally with the shaft 31 of the motor 30, and a worm wheel 75B that meshes with the worm shaft 75A. Therefore, the rotational motion of the shaft 31 is transmitted to the worm wheel 75B via the worm shaft 75A. In this embodiment, the side of the shaft 31 facing the reduction gear 75 is referred to as the load side end, and the side of the shaft 31 opposite the reduction gear 75 is referred to as the anti-load side end.

The second rack and pinion mechanism 70 has a second pinion shaft 71A, a second pinion gear 71B, and a second rack 71C. One end of the second pinion shaft 71A is fixed so as to be coaxial with the worm wheel 75B and rotate integrally with it. The other end of the second pinion shaft 71A is connected to the second pinion gear 71B. The second rack 71C formed on the rack shaft 99C meshes with the second pinion gear 71B. The rotational motion of the motor 30 is transmitted to the second rack and pinion mechanism 70 via the reduction gear 75. This rotational motion is converted into linear motion of the rack shaft 99C by the second rack and pinion mechanism 70.

The driver's steering force input to the steering wheel 91 is transmitted to the first rack and pinion mechanism 99 via the steering shaft 92 and the intermediate shaft 97. The first rack and pinion mechanism 99 transmits the transmitted steering force to the rack shaft 99C as a force applied in the axial direction of the rack shaft 99C. At this time, the ECU 10 acquires the steering torque signal T input to the steering shaft 92 from the torque sensor 94. The ECU 10 acquires the vehicle speed signal SV from the vehicle speed sensor 82. The ECU 10 acquires the rotation phase signal of the motor 30 from the rotation angle sensor 23a. Then, the ECU 10 outputs a control signal to control the operation of the motor 30. The auxiliary steering torque generated by the motor 30 is transmitted to the second rack and pinion mechanism 70 via the reduction gear 75. The second rack and pinion mechanism 70 transmits the auxiliary steering torque to the rack shaft 99C as a force applied in the axial direction of the rack shaft 99C. In this way, the steering of the steering wheel 91 by the driver is assisted by the electric power steering device 100.

As shown in FIG. 2, the electric power steering device 100 is of a rack assist type in which an assist force is applied to the second rack and pinion mechanism 70, but is not limited to this. The electric power steering device 100 may be of a column assist type in which an assist force is applied to the steering shaft 92, or a pinion assist type in which an assist force is applied to the first pinion gear 99B, for example.

FIG. 3 is a cross-sectional view showing a cross section of the motor according to the first embodiment. FIG. 4 is a schematic diagram showing wiring of the motor according to the first embodiment. In this embodiment, the circumferential direction is a direction along a concentric circle centered on the shaft 31. The radial direction is a direction away from the shaft 31 in a plane perpendicular to the axial direction Ax. As shown in FIG. 3, the motor 30 includes a housing 930, a motor stator having a stator core 931, and a motor rotor 932. The motor stator includes the cylindrical stator core 931, a plurality of first coils 37, and a plurality of second coils 38. The stator core 931 includes an annular back yoke 931a and a plurality of teeth 931b protruding from the inner circumferential surface of the back yoke 931a. Twelve teeth 931b are arranged in the circumferential direction. The motor rotor 932 includes a rotor yoke 932a and a magnet 932b. The magnets 932b are provided on the outer circumferential surface of the rotor yoke 932a. The number of magnets 932b is, for example, eight. The rotation of the motor rotor 932 is linked to the rotation of the shaft 31.

As shown in FIG. 3, the first coil 37 is wound in a concentrated manner around each of the teeth 931b. The first coil 37 is wound in a concentrated manner around the outer periphery of the teeth 931b via an insulator. All of the first coils 37 are included in the first coil system. The first coil system according to the first embodiment is supplied with current and excited by an inverter circuit 251 (see FIG. 5) included in the first power circuit 25A. The first coil system includes, for example, six first coils 37. The six first coils 37 are arranged so that two first coils 37 are adjacent to each other in the circumferential direction. Three first coil groups Gr1, each of which includes adjacent first coils 37 as one group, are arranged at equal intervals in the circumferential direction. That is, the first coil system includes three first coil groups Gr1 arranged at equal intervals in the circumferential direction. The number of first coil groups Gr1 does not necessarily have to be three, and it is sufficient that 3n first coil groups Gr1 are arranged at equal intervals in the circumferential direction when n is a natural number. Also, it is preferable that n is an odd number. As described above, in this embodiment, there are multiple coil groups, and each of the three phases is divided into at least two systems, the first coil group gr1 and the second coil group Gr2, and the stator core is excited with three-phase AC.

As shown in FIG. 3, the second coil 38 is wound in a concentrated manner on each of the teeth 931b. The second coil 38 is wound in a concentrated manner on the outer periphery of the teeth 931b via an insulator. The teeth 931b on which the second coil 38 is wound in a concentrated manner are different from the teeth 931b on which the first coil 37 is wound in a concentrated manner. All the second coils 38 are included in the second coil system. The second coil system is supplied with current and excited by the inverter circuit 251 (see FIG. 5) included in the second power circuit 25B. The second coil system includes, for example, six second coils 38. The six second coils 38 are arranged so that two second coils 38 are adjacent to each other in the circumferential direction. Three second coil groups Gr2, each of which includes adjacent second coils 38 as one group, are arranged at equal intervals in the circumferential direction. That is, the second coil system includes three second coil groups Gr2 arranged at equal intervals in the circumferential direction. The number of second coil groups Gr2 does not necessarily have to be three; it is sufficient that 3n coils are arranged at equal intervals in the circumferential direction, where n is a natural number. It is also preferable that n be an odd number.

4, the six first coils 37 include two first U-phase coils 37Ua and 37Ub excited by a first U-phase current I1u, two first V-phase coils 37Va and 37Vb excited by a first V-phase current I1v, and two first W-phase coils 37Wa and 37Wb excited by a first W-phase current I1w. The first U-phase coil 37Ub is connected in series to the first U-phase coil 37Ua. The first V-phase coil 37Vb is connected in series to the first V-phase coil 37Va. The first W-phase coil 37Wb is connected in series to the first W-phase coil 37Wa. The winding directions of the first coils 37 around the teeth 931b are all the same. Additionally, the first U-phase coil 37Ub, the first V-phase coil 37Vb, and the first W-phase coil 37Wb are joined by a star connection (Y connection).

As shown in FIG. 4, the six second coils 38 include two second U-phase coils 38Ua and 38Ub excited by the second U-phase current I2u, two second V-phase coils 38Va and 38Vb excited by the second V-phase current I2v, and two second W-phase coils 38Wa and 38Wb excited by the second W-phase current I2w. The second U-phase coil 38Ub is connected in series to the second U-phase coil 38Ua. The second V-phase coil 38Vb is connected in series to the second V-phase coil 38Va. The second W-phase coil 38Wb is connected in series to the second W-phase coil 38Wa. The winding directions of the second coils 38 around the teeth 931b are all the same direction, and are the same as the winding direction of the first coil 37. Additionally, the second U-phase coil 38Ub, the second V-phase coil 38Vb, and the second W-phase coil 38Wb are joined by a star connection (Y connection).

As shown in FIG. 3, the three first coil groups Gr1 are composed of a first UV coil group Gr1UV, a first VW coil group Gr1VW, and a first UW coil group Gr1UW. The first UV coil group Gr1UV includes a first U-phase coil 37Ub and a first V-phase coil 37Va that are adjacent to each other in the circumferential direction. The first VW coil group Gr1VW includes a first V-phase coil 37Vb and a first W-phase coil 37Wa that are adjacent to each other in the circumferential direction. The first UW coil group Gr1UW includes a first U-phase coil 37Ua and a first W-phase coil 37Wb that are adjacent to each other in the circumferential direction.

As shown in FIG. 3, the three second coil groups Gr2 are composed of a second UV coil group Gr2UV, a second VW coil group Gr2VW, and a second UW coil group Gr2UW. The second UV coil group Gr2UV includes a second U-phase coil 38Ub and a second V-phase coil 38Va that are adjacent to each other in the circumferential direction. The second VW coil group Gr2VW includes a second V-phase coil 38Vb and a second W-phase coil 38Wa that are adjacent to each other in the circumferential direction. The second UW coil group Gr2UW includes a second U-phase coil 38Ua and a second W-phase coil 38Wb that are adjacent to each other in the circumferential direction.

The first coil 37 excited by the first U-phase current I1u faces the second coil 38 excited by the second U-phase current I2u in the radial direction of the stator core 931. In the following description, the radial direction of the stator core 931 is simply referred to as the radial direction. For example, as shown in FIG. 3, the first U-phase coil 37Ua faces the second U-phase coil 38Ua in the radial direction, and the first U-phase coil 37Ub faces the second U-phase coil 38Ub.

The first coil 37 excited by the first V-phase current I1v faces the second coil 38 excited by the second V-phase current I2v in the radial direction. For example, as shown in FIG. 3, the first V-phase coil 37Va faces the second V-phase coil 38Va in the radial direction, and the first V-phase coil 37Vb faces the second V-phase coil 38Vb.

The first coil 37 excited by the first W-phase current I1w faces the second coil 38 excited by the second W-phase current I2w in the radial direction. For example, as shown in FIG. 3, the first W-phase coil 37Wa faces the second W-phase coil 38Wa in the radial direction, and the first W-phase coil 37Wb faces the second W-phase coil 38Wb.

Figure 5 is a schematic diagram showing the relationship between the motor and the ECU according to the first embodiment. As shown in Figure 5, the ECU 10 includes a detection circuit 23, a control circuit 24, a first power circuit 25A, and a second power circuit 25B. The detection circuit 23 includes a rotation angle sensor 23a and a motor rotation speed calculation unit 23b. The control circuit 24 includes a control calculation unit 241, a gate drive circuit 242, and a cutoff drive circuit 243. The first power circuit 25A includes an inverter circuit 251 and a current cutoff circuit 255. The second power circuit 25B includes an inverter circuit 251 and a current cutoff circuit 255. The inverter circuit 251 also includes a plurality of switching elements 252 and a current detection circuit 254 for detecting a current value. Note that in Figure 5, circuits that do not require description are omitted as appropriate.

The control calculation unit 241 calculates the motor current command value. The motor rotation speed calculation unit 23b calculates the motor electrical angle θm and outputs it to the control calculation unit 241. The gate drive circuit 242 receives the motor current command value output from the control calculation unit 241. The gate drive circuit 242 controls the first power circuit 25A and the second power circuit 25B based on the motor current command value.

As shown in FIG. 5, the ECU 10 is equipped with a rotation angle sensor 23a. The rotation angle sensor 23a is, for example, a magnetic sensor. The detection value of the rotation angle sensor 23a is supplied to the motor rotation speed calculation unit 23b. The motor rotation speed calculation unit 23b calculates the motor electrical angle θm based on the detection value of the rotation angle sensor 23a and outputs it to the control calculation unit 241.

The control calculation unit 241 receives the steering torque signal T detected by the torque sensor 94, the vehicle speed signal SV detected by the vehicle speed sensor 82, and the motor electrical angle θm output from the motor rotation speed calculation unit 23b. The control calculation unit 241 calculates a motor current command value based on the steering torque signal T, the vehicle speed signal SV, and the motor electrical angle θm, and outputs the motor current command value to the gate drive circuit 242.

The gate drive circuit 242 calculates a first pulse width modulation signal based on the motor current command value and outputs it to the inverter circuit 251 of the first power circuit 25A. The inverter circuit 251 switches the switching element 252 to obtain three-phase current values according to the duty ratio of the first pulse width modulation signal, generating a three-phase AC including a first U-phase current I1u, a first V-phase current I1v, and a first W-phase current I1w. The first U-phase current I1u excites the first U-phase coil 37Ua and the first U-phase coil 37Ub, the first V-phase current I1v excites the first V-phase coil 37Va and the first V-phase coil 37Vb, and the first W-phase current I1w excites the first W-phase coil 37Wa and the first W-phase coil 37Wb.

The gate drive circuit 242 calculates a second pulse width modulation signal based on the motor current command value and outputs it to the inverter circuit 251 of the second power circuit 25B. The inverter circuit 251 switches the switching element 252 to obtain three-phase current values according to the duty ratio of the second pulse width modulation signal, generating a three-phase AC including a second U-phase current I2u, a second V-phase current I2v, and a second W-phase current I2w. The second U-phase current I2u excites the second U-phase coil 38Ua and the second U-phase coil 38Ub, the second V-phase current I2v excites the second V-phase coil 38Va and the second V-phase coil 38Vb, and the second W-phase current I2w excites the second W-phase coil 38Wa and the second W-phase coil 38Wb.

The inverter circuit 251 is a power conversion circuit that converts DC power into AC power. As described above, the inverter circuit 251 has a plurality of switching elements 252. The switching elements 252 are, for example, field effect transistors. A smoothing capacitor 253 is connected in parallel to the inverter circuit 251. The smoothing capacitor 253 is, for example, an electrolytic capacitor. The circuit board 20 is provided with a plurality of smoothing capacitors connected in parallel as the smoothing capacitors 253.

As described above, the inverter circuit 251 also has a current detection circuit 254. The current detection circuit 254 includes, for example, a shunt resistor. The current value detected by the current detection circuit 254 is sent to the control calculation unit 241. The current detection circuit 254 may be connected to detect the current value of each phase of the motor 30.

The current interruption circuit 255 is disposed between the inverter circuit 251 and the first coil 37 or the second coil 38. When the current value detected by the current detection circuit 254 is determined to be abnormal, the control calculation unit 241 drives the current interruption circuit 255 via the interruption drive circuit 243 to interrupt the current flowing from the inverter circuit 251 to the first coil 37. The control calculation unit 241 also drives the current interruption circuit 255 via the interruption drive circuit 243 to interrupt the current flowing from the inverter circuit 251 to the second coil 38. In this way, the current flowing to the first coil 37 and the current flowing to the second coil 38 are each independently controlled by the control calculation unit 241. Input and output signals such as the steering torque signal T and the vehicle speed signal SV are also transmitted to the control calculation unit 241 via the connector CNT.

Figure 6 is a side view of the electric drive device according to the first embodiment. Figure 7 is a plan view of the electric drive device according to the first embodiment. Figure 8 is a cross-sectional view showing a cross section along the VIII-VIII arrows in Figure 6. Figure 9 is a cross-sectional view showing a cross section along the IX-IX arrows in Figure 7. Figure 10 is a cross-sectional view showing a cross section along the X-X arrows in Figure 7. Figure 11 is a cross-sectional view showing a cross section along the XI-XI arrows in Figure 6. Figure 12 is a perspective view of the electric drive device according to the first embodiment with the cover removed. Figure 13 is a plan view of Figure 12. Figure 14 is a perspective view of the electric drive device according to the first embodiment with the cover and the circuit board removed. Figure 15 is a plan view of Figure 14. As shown in Figures 6 and 7, the electric drive device 1 includes a motor 30 and an ECU 10 arranged on the anti-load side of the motor 30.

6 and 7, the ECU 10 includes a heat sink 40 and a cover 50 that covers the anti-load side of the heat sink 40. As shown in FIG. 8, the heat sink 40 supports the circuit board 20, and the cover 50 covers the circuit board 20. As shown in FIG. 9, the heat sink 40 is attached with the circuit board 20 and a connector CNT. When viewed from the axial direction Ax, the connector CNT is arranged so that the connector terminal of the wire harness can be inserted and removed from the radial outside of the shaft 31 of the motor 30. As described above, the ECU 10 includes the circuit board 20, the heat sink 40 that supports the circuit board 20, the connector CNT, and the cover 50.

As shown in FIG. 8, the motor 30 includes a housing 930. The motor rotor 932 includes a rotor yoke 932a and a magnet 932b. The magnet 932b is provided on the outer peripheral surface of the rotor yoke 932a. The housing 930 is cylindrical and accommodates the motor rotor 932, a stator including a plurality of coil groups divided into two systems for three phases, for example, a first coil group Gr1 and a second coil group Gr2 (see FIG. 3), and the shaft 31.

As shown in FIG. 8, the circuit board 20 has a board body 21 and a plurality of electronic components mounted on the board body 21. The board body 21 is, for example, a printed circuit board made of resin or the like. The plurality of electronic components mounted on one board body 21 include, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), a field effect transistor (FET), a magnetic sensor, an electrolytic capacitor, a resistive element, a diode, a thermistor, and the like. The detection circuit 23, the control circuit 24, the first power circuit 25A, and the second power circuit 25B shown in FIG. 5 are configured by these plurality of electronic components.

As shown in FIG. 9, the heat sink 40 has a step 43 between a first surface 41 and a second surface 42 on the anti-load side of the heat sink body. The first surface 41 does not have to be a flat surface, and it is sufficient that it is lower than the second surface 42 in the axial direction Ax. A housing portion 47 for housing a choke coil is provided between the first surface 41 and the second surface 42.

As shown in FIG. 9, the heat sink 40 supports the circuit board 20. The circuit board 20 is fixed to one surface (anti-load side) of the heat sink 40. The heat sink 40 is made of a metal material with high heat dissipation properties, such as aluminum or copper, and efficiently dissipates heat generated by the circuit board 20 to the outside.

As shown in FIG. 8, the shaft 31 is rotatably supported by bearings 33 and 34. Bearing 33 is interposed between the heat sink 40 and the shaft 31. On the load side of the heat sink 40, there is a bearing support portion 411, and there is a hollow portion 45H of the heat sink 40 through which the shaft 31 passes. The bearing 33 is disposed on the inside 35 of the hollow portion 45H surrounded by the bearing support portion 411. Bearing 34 is interposed between the housing 930 and the shaft 31.

As shown in Figures 8 and 9, a magnet 32 is attached to one end of the shaft 31 via a magnet holder 32A. Half of the magnet 32 is magnetized with a south pole when viewed from the axial direction Ax, and the other half is magnetized with a north pole. Alternatively, the magnet 32 may have south and north poles arranged alternately on its outer circumferential surface when viewed in the circumferential direction. Since the bearing 33 has high component precision, the position of the magnet 32 in the axial direction Ax, which is arranged on the anti-load side of the heat sink 40, is constant. The end where the magnet 32 is located is the anti-load end of the shaft 31.

At the other end of the shaft 31 is a motor gear 31G that transmits rotation to the worm shaft 75A (see FIG. 1). The end where the motor gear 31G is located is the load side end of the shaft 31.

The substrate body 21 has a first surface 21b and a second surface 21a located on the opposite side of the first surface 21b. The detection circuit 23, the control circuit 24, the first power circuit 25A, and the second power circuit 25B shown in FIG. 5 are composed of one or more electronic components mounted on the first surface 21b or the second surface 21a. For example, the rotation angle sensor 23a is composed of one electronic component mounted on the first surface 21b of the substrate body 21.

The control circuit 24 shown in FIG. 5 is composed of a plurality of electronic components each mounted on the second surface 21a of the substrate body 21. The circuit board 20 also includes a smoothing capacitor 253 mounted on the second surface 21a of the substrate body 21. The circuit board 20 also includes a choke coil 61 mounted on the first surface 21b of the substrate body 21 (see FIG. 10).

The rotation angle sensor 23a is disposed on the anti-load side of the shaft 31, on an extension of the axial direction Ax of the magnet 32. The substrate body 21 has a plane perpendicular to the axial direction Ax as the mounting surface for the rotation angle sensor 23a. The rotation angle sensor 23a is mounted on the substrate body 21 so as to sense changes in the magnetic field of the magnet 32. It is desirable that the magnet 32 and the rotation angle sensor 23a face each other in the axial direction Ax. The rotation angle sensor 23a may be disposed on the second surface 21a instead of the first surface 21b of the substrate body 21, or may be disposed on both the first surface 21b and the second surface 21a of the substrate body 21.

The rotation angle sensor 23a is, for example, a spin valve sensor. A spin valve sensor is an element in which a non-magnetic layer is sandwiched between a pinned layer of a ferromagnetic material whose magnetization direction is fixed by an antiferromagnetic layer or the like, and a free layer of a ferromagnetic material, and is a sensor that can detect changes in the direction of magnetic flux. Spin valve sensors include GMR (Giant Magneto Resistance) sensors and TMR (Tunnel Magneto Resistance) sensors. Note that the rotation angle sensor 23a may be any sensor that can detect the rotation of the magnet 32. The rotation angle sensor 23a may be, for example, an AMR (Anisotropic Magneto Resistance) sensor or a Hall sensor.

The lid 50 is made of metal or resin and prevents foreign matter and moisture from entering the inside of the electric drive device 1. As shown in FIG. 8, the lid 50 is fixed between a support post 451 protruding from the anti-load side of the heat sink 40 and a bolt CT, which is a fixing member.

As shown in Figures 9, 10, and 11, the heat sink 40 has a base portion 44 that supports the connector CNT. The base portion 44 protrudes radially outward beyond the inner wall of the housing 930. The connector CNT is disposed on the anti-load side of the base portion 44.

The connector CNT has a power terminal, a communication terminal for performing CAN communication, and an input/output terminal for inputting and outputting data by a method other than CAN communication. The resin material of the connector CNT is, for example, polybutylene terephthalate (PBT).

As shown in Figures 12 and 13, the circuit board 20 is disposed on the anti-load side of the heat sink 40. As shown in Figures 14 and 15, the mounting surface 441 is closer to the load side than the first surface 41, and the second surface 42 is closer to the anti-load side than the first surface.

As shown in FIG. 10, the connector CNT transmits the power wiring PW (see FIG. 2) that transmits power from the power supply device 83 to the circuit board 20. As shown in FIG. 13, a choke coil 61 and a capacitor 62 are attached to the circuit board 20, and the choke coil 61 and the capacitor 62 form a filter circuit. The filter circuit removes high-frequency components from the power wiring PW from the power supply device 83. The capacitor 62 is, for example, a film capacitor.

For this reason, it is desirable to arrange the connector CNT and the choke coil 61 close to each other, as shown in FIG. 10, in order to increase the efficiency of removing high-frequency components. The housing portion 47 is arranged adjacent to the power terminal of the connector CNT.

The recess 46 of the storage section 47 is filled with a heat dissipation material 63. The heat dissipation material 63 is, for example, a material in which a thermally conductive filler is mixed into a silicone polymer. The heat dissipation material 63 is, for example, in a paste form. For example, the viscosity of the heat dissipation material 63 is 200 Pa·s or more and 300 Pa·s or less. If the viscosity of the heat dissipation material 63 is 250 Pa·s or more, the heat dissipation material 63 is less likely to flow out of the storage section 47.

When the choke coil 61 is inserted into the recess 46 of the housing 47, the upper surface of the heat sink rises, and the heat sink 63 comes into contact with more than one-third of the axial direction of the choke coil 61. As a result, the heat of the choke coil 61 is dissipated in multiple directions and transmitted to the housing 47.

As shown in Figures 12 and 13, the recess 46 of the storage section 47 is completely covered by the circuit board 20. As shown in Figures 14 and 15, the outer surfaces of the first wall section 461, the second wall section 462, and the third wall section 463 of the storage section 47 are longer in the axial direction than the depth of the recess 46 of the storage section 47. The outer surfaces of the first wall section 461, the second wall section 462, and the third wall section 463 of the storage section 47 have a large area, which can improve the heat dissipation properties of the storage section 47.

As shown in FIG. 15, the recess 46 of the storage section 47 has a bottom surface 46e and four inner wall surfaces 46a, 46b, 46c, and 46d. The inner wall surface 46c is a step wall between the bottom surface 46e and the second surface 42 between the first wall section 461 and the second wall section 462. The five surfaces of the choke coil 61 face the bottom surface 46e and each of the four inner wall surfaces 46a, 46b, 46c, and 46d, improving heat dissipation efficiency.

14 and 15, when viewed in the axial direction, the accommodation portion 47 protrudes from the wall of the step 43 of the heat sink 40 toward the connector CNT, and the accommodation portion 47 is sandwiched between two first surfaces 41. The outside of the first wall portion 461 and the second wall portion 462 is the first surface 41. A capacitor 62 is arranged in one of the first surfaces 41. The first wall portion 461 and the second wall portion 462 protrude from the wall of the step 43 of the heat sink 40 toward the connector CNT, and a choke coil 61 can be accommodated between the first wall portion 461 and the second wall portion 462. The first wall portion 461 and the second wall portion 462 are connected by a third wall portion 463, and a recess 46 is formed. The distance between the choke coil 61 and the four inner wall surfaces 46a, 46b, 46c, and 46d is, for example, about 0.5 mm or more and 1.5 mm or less, and is at least smaller than the size of the choke coil 61.

If low-viscosity heat dissipation material 63 is filled in recess 46 and, in the unlikely event that heat dissipation material 63 climbs over storage section 47, it can be received by first surface 41 adjacent to storage section 47, making it unlikely for unexpected malfunctions to occur. In addition, the end of storage section 47 on the anti-load side is flush with second surface 42. If low-viscosity heat dissipation material 63 is filled in recess 46 and, in the unlikely event that heat dissipation material 63 climbs over storage section 47 and moves toward second surface 42, it will simply spread over second surface 42, making it unlikely for malfunctions to occur.

In addition, the hollow portion 45H and the choke coil 61 sandwich the second surface 42 when viewed in the axial direction. Therefore, the low-viscosity heat dissipation material 63 is filled in the recess 46, and even if the heat dissipation material 63 overcomes the housing portion 47, it is difficult for it to move from the housing portion 47 to the hollow portion 45H. As a result, the heat dissipation material 63 is difficult to adhere to the shaft 31 and the magnet 32.

As shown in FIG. 14, the heat sink 40 has support columns 451 and 452 that protrude from the first surface 41 toward the anti-load side. The support columns 451 and 452 each have a female thread portion drilled in the axial direction Ax from the top surface on the anti-load side. As shown in FIG. 12, the support column 451 protrudes beyond the circuit board 20. As shown in FIG. 8, the cover 50 is fixed to the heat sink 40 by fastening the bolt CT that passes through the cover 50 to the female thread portion of the support column 451.

As shown in FIG. 12, the bolt BT1 that penetrates the circuit board 20 is fastened to the female thread of the support column 452. This fixes the circuit board 20 to the heat sink 40 so that it does not shift.

As shown in FIG. 12, the connector CNT is sandwiched between the heat sink 40 and the circuit board 20, and the circuit board 20 and the connector CNT are fixed with a bolt BT2. This fixes the connector CNT to the circuit board 20 so that it does not shift.

The bolt BT1 that fixes the heat sink 40 to the circuit board 20 is located adjacent to the bolt BT2. Since the bolt BT1 (second bolt) and the bolt BT2 (third bolt) are close to each other, even if the connector CNT swings, the fastening force of the bolt BT1 in addition to the fastening force of the bolt BT2 can suppress the swinging of the connector CNT.

As shown in FIG. 12, the electric drive device 1 includes a first coil wiring 321 that connects the first coil group Gr1 to the circuit board 20, and a second coil wiring 322 that connects the second coil group Gr2 to the circuit board 20. The first coil wiring 321 and the second coil wiring 322 may be included in the ECU 10 or may be included in the motor 30.

As shown in FIG. 12, the first coil wiring 321 and the second coil wiring 322 are inserted into the through holes of the circuit board 20, and the circuit board 20 is electrically connected to the first coil wiring 321 and the second coil wiring 322.

As shown in Figs. 12 and 13, the second surface 42 faces the circuit board 20 in order to dissipate heat generated by the circuit board 20. A heat dissipation material is applied between the circuit board 20 and the second surface 42 of the heat sink 40. The heat dissipation material is, for example, a material in which a thermally conductive filler is mixed into a silicone polymer, and is called a TIM (Thermal Interface Material). The heat dissipation material may be any material other than the above materials, so long as it has a higher thermal conductivity than the board body 21 of the circuit board 20.

As shown in Figures 11, 14, and 15, the anti-load side of the base 44 has a mounting surface 441 on which the connector CNT is mounted, a protrusion 442 that protrudes further toward the anti-load side than the mounting surface 441, a recess 443 at the base of the protrusion 442 that is recessed toward the load side than the mounting surface 441, and a recess 444 that is recessed toward the load side than the mounting surface 441 and accommodates the head of the bolt BBT, which is a fixing member.

As shown in Figures 9 and 11, the connector CNT has a recess CNTR on the load side. The protrusion 442 is fitted into the recess CNTR. When viewed from the radial direction of the shaft 31, the recess CNTR is provided midway between both ends of the connector CNT. This allows the recess CNTR to have a minimum volume, ensuring sufficient conductor space for the connector.

As shown in FIG. 14, the shape of the protrusion 442 is a rectangular column. This allows each surface of the column to provide a reaction force against the twisting force, further suppressing the oscillation of the connector CNT. The protrusion 442 is made of metal, so even though it is small, it can support the connector CNT.

As shown in Figures 10 and 14, the bolt BBT that passes through the base portion 44 is fastened to the female thread portion of the flange 933 of the motor 30, thereby fixing the heat sink 40 to the motor 30.

As described above, the electric drive device 1 includes the motor 30, the ECU 10 provided on the anti-load side of the shaft 31 to drive and control the motor 30, and the connector CNT. The ECU 10 includes a magnet 32 at the end of the anti-load side of the shaft 31, and a circuit board 20 arranged on the anti-load side of the shaft 31, on an extension of the axial direction (e.g., axial direction Ax) of the shaft 31. The circuit board 20 includes a detection circuit 23 including a rotation angle sensor 23a that detects the rotation of the magnet 32, and a choke coil 61. The rotation angle sensor 23a is a magnetic sensor that detects the rotation of the magnet 32.

The connector CNT is provided on the radial side of the shaft 31. The heat sink 40 has a recess 46 on the anti-load side into which the choke coil 61 is inserted, and has a housing portion 47 that protrudes from the wall of the step 43 between the first surface 41 and the second surface 42 toward the connector CNT.

This reduces the size of the axial direction Ax parallel to the shaft 31 of the motor 30, making the electric drive device 1 smaller. Heat generated by passing current through the choke coil 61 is transferred to the housing portion. Because the housing portion 47 protrudes, the surface area of the housing portion 47 is increased, improving the heat dissipation properties of the housing portion 47 itself. As a result, the heat transferred to the housing portion 47 is dissipated from the housing portion 47, making it difficult for the temperature of the choke coil 61 to rise.

The heat sink 40 has a first surface 41 located on the anti-load side of the mounting surface 441, and a second surface located on the anti-load side of the first surface 41. The second surface 42 faces the circuit board 20 and is a heat dissipation surface that dissipates heat from the circuit board 20. The accommodation section 47 is provided between the first surface 41 and the second surface 42. The accommodation section 47 is provided by utilizing the step between the first surface 41 and the second surface 42, so that the accommodation section 47 can be provided in a space-saving manner.

The electric power steering device 100 also includes the electric drive device 1 described above, which generates an auxiliary steering torque. This reduces the axial direction Ax parallel to the shaft 31 of the motor 30 and the radial size of the shaft 31, improving the freedom of arrangement of the electric power steering device 100.

(Embodiment 2)
Fig. 16 is a cross-sectional view showing a cross section along the X-X arrow in Fig. 7 according to the second embodiment. Fig. 17 is a perspective view explaining an electric drive device according to the second embodiment with the cover and the circuit board removed. Note that the same components as those explained in the first embodiment above are given the same reference numerals and redundant explanations will be omitted. In the second embodiment, there is no third wall portion 463, and an opening 463A is provided.

The heat sink 40 has a first surface 41, a second surface 42 located on the anti-load side of the first surface 41, and a first wall portion 461 and a second wall portion 462 protruding from the wall of the step 43 between the first surface 41 and the second surface 42 toward the connector CNT. A bottom surface 46e between the first wall portion 461 and the second wall portion 462 is located on the anti-load side of the first surface 41 and on the load side of the second surface 42. The bottom surface 46e is recessed when viewed from the second surface 42. A choke coil 61 is inserted between the first wall portion 461 and the second wall portion 462.

The heat sink 40 of the second embodiment does not have the third wall portion 463, so when attaching the connector CNT to the heat sink 40, there is no possibility that the terminal of the connector CNT will come into contact with the third wall portion 463. As a result, the reliability of the electric drive device 1 is improved.

In addition, the four faces of the choke coil 61 face the bottom surface 46e and the four inner wall surfaces 46a, 46b, and 46c, respectively, improving heat dissipation efficiency. Heat generated by energizing the choke coil 61 is transferred to the first wall portion 461 and the second wall portion 462. The outer surfaces of the first wall portion 461 and the second wall portion 462 have a large area, which can improve the heat dissipation of the storage portion 47. For example, if the connector CNT is inserted and removed from above in the vertical direction, the opening 463A faces upward in the vertical direction. Here, it is desirable that the opening 463A of the electric drive device 1 of embodiment 2 faces upward in the vertical direction. This makes it difficult for the heat dissipation material 63 to flow out.

The connector CNT is provided on the radial side of the shaft 31. The heat sink 40 has a first wall portion 261 and a second wall portion 262 that protrude toward the connector CNT side from the wall of the step 43 between the first surface 41 and the second surface 42. A choke coil 61 is inserted between the first wall portion 461 and the second wall portion 462.

This reduces the size of the axial direction Ax parallel to the shaft 31 of the motor 30, making the electric drive device 1 smaller. Heat generated by energizing the choke coil 61 is transferred to the first wall portion 461, the second wall portion 462, and the bottom surface 46e. Because the first wall portion 461 and the second wall portion 462 protrude, the surface area of the first wall portion 461 and the second wall portion 462 is increased, and the heat dissipation properties of the first wall portion 461 and the second wall portion 462 are improved. As a result, the heat transferred to the first wall portion 461 and the second wall portion 462 is dissipated from the first wall portion 461 and the second wall portion 462, making it difficult for the temperature of the choke coil 61 to rise.

(Embodiment 3)
FIG. 18 is a schematic diagram of an electric power steering device according to a third embodiment. FIG. 19 is a side view showing an example of the arrangement of an ECU according to the third embodiment. FIG. 20 is a cross-sectional view showing a cross section along the X-X arrows in FIG. 7 according to the third embodiment. FIG. 21 is a perspective view explaining an electric drive device according to the third embodiment with the cover and the circuit board removed. Note that the same components as those explained in the first and second embodiments are given the same reference numerals and overlapping explanations are omitted. In the third embodiment, there is no wall portion 463, and an opening 463A is provided. The bottom surface 46e has a groove portion 48 along the edge of the opening 463A.

As shown in FIG. 18, the electric power steering device 100A is a column assist type, and the electric drive device 1 applies an assist force to the steering shaft 92 and the output shaft 92B via the reduction gear 75.

As shown in FIG. 19, the electric drive device 1 including the ECU 10 and the motor 30 is disposed in the reduction gear device 75. In this embodiment, the axial direction Ax refers to a direction parallel to the extension direction of the shaft 31 (see FIG. 3) of the motor 30. The axial direction Ax is often inclined with respect to the vertical direction VD. This is because the axial direction Ax is determined based on the space available in the vehicle 101 (see FIG. 1). For example, if the connector CNT is inserted and removed from a diagonally downward direction of the vertical direction VD, the opening 463A may face downward in the vertical direction VD.

In the third embodiment, the bottom surface 46e has a groove portion 48 along the edge of the opening 463A, so that the groove portion 48 serves as a storage portion for the heat dissipation material 63, making it difficult for the heat dissipation material 63 to flow out. Even if the opening 463A faces downward in the vertical direction VD, the heat dissipation material 63 does not easily flow out, so problems due to the flow of the heat dissipation material 63 are unlikely to occur. Because the heat dissipation material 63 does not easily flow out, a low viscosity material can also be used.

In this way, in embodiment 3, the bottom surface 46e has a groove portion 48 along the edge of the opening 463A, which increases the freedom of positioning of the electric drive device 1.

1 Electric drive unit 10 ECU
20 Circuit board 21 Board body 21a Second surface 21b First surface 23 Detection circuit 23a Rotation angle sensor 24 Control circuit 25A First power circuit 25B Second power circuit 30 Motor 31 Shaft 31G Motor gear 32 Magnet 33, 34 Bearing 40 Heat sink 41 First surface 42 Second surface 43 Step 44 Base portion 45H Hollow portion 46 Recessed portion 46a, 46b, 46c, 46d Inner wall surface 46e Bottom surface 461, 462, 463 Wall portion 47 Storage portion 50 Lid 100 Electric power steering device 101 Vehicle 930 Housing 931 Stator core 931a Back yoke 931b Teeth 932 Motor rotor 932a Rotor yoke 932b Magnet 933 Flange Ax Axial direction BBT, BT1, BT2, CT Bolt CNT Connector CNTQ Square CNTR Concave

Claims (10)

A shaft extending in an axial direction from a load side to a non-load side;
a motor rotor coupled to the shaft;
a motor stator including a stator core that rotates the motor rotor;
a motor including a housing that houses the motor rotor and the motor stator therein;
A magnet provided on the anti-load side of the shaft;
a heat sink provided on the anti-load side of the motor;
an electronic control device including a circuit board on which a choke coil is mounted, the circuit board being disposed on the anti-load side of the heat sink; and a rotation angle sensor located on an extension line of the axial direction of the magnet and attached to the circuit board;
a connector provided on a radial side of the heat sink relative to the shaft,
the heat sink has a first surface, a second surface located on the anti-load side of the first surface, and a first wall portion and a second wall portion protruding from a wall of a step between the first surface and the second surface toward the connector,
The choke coil is inserted between the first wall portion and the second wall portion. The electric drive device according to claim 1, further comprising a third wall portion connecting the first wall portion and the second wall portion, and the heat sink comprises a recess surrounded on all four sides by a step wall between the bottom surface between the first wall portion and the second wall portion and the second surface, the first wall portion, the second wall portion, and the third wall portion. The electric drive device according to claim 1 or 2, wherein a heat dissipating material is provided between the first wall portion and the second wall portion. The electric drive device according to claim 3, wherein the viscosity of the heat dissipation material is 200 Pa·s or more and 300 Pa·s or less. The electric drive device according to claim 3 or 4, wherein the heat dissipation material is in contact with at least one-third of the choke coil in the axial direction. The electric drive device according to any one of claims 1 to 5, wherein the heat sink is located closer to the load than the first surface and further has a mounting surface on which the connector is mounted, and the second surface faces the circuit board and is a heat dissipation surface that dissipates heat from the circuit board. The electric drive device according to claim 6, wherein the outside of the first wall portion and the second wall portion is the first surface when viewed in the axial direction. The electric drive device according to claim 6 or 7, wherein the choke coil is disposed near the power terminal of the connector. The electric drive device according to any one of claims 6 to 8, wherein the heat sink has a hollow portion through which the shaft passes, and the hollow portion and the choke coil sandwich the second surface when viewed in the axial direction. The electric drive device according to any one of claims 1 to 9,
An electric power steering device in which the electric drive device generates an auxiliary steering torque.

Images