JP7404915B2 - Motor unit and electric power steering device - Google Patents

Description

The present invention relates to a motor unit and an electric power steering device.

The electric power steering device includes an electric motor and a control device that controls the electric motor. In order to simplify the structure of an electric power steering device, a technique is known in which the control device and the electric motor are integrated by attaching the control device to the electric motor. For example, Patent Document 1 describes an example of a method for fixing a control unit to an electric motor. In Patent Document 1, electromagnetic compatibility (EMC) is improved by covering a unit-side connector provided in a control unit with a gear box.

JP2009-029287A

However, when the gear box covers the connector as in Patent Document 1, the volume of the gear box increases, making it difficult to reduce the weight.

The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a motor unit and an electric power steering device that can be lightweight and improve electromagnetic environment compatibility.

To achieve the above object, a motor unit according to one aspect of the present disclosure includes a cylindrical motor case, a gearbox that is a conductor disposed at one end of the motor case, and a gearbox that extends radially outward of the gearbox. The gearbox includes an electric motor including a motor terminal, a control device case supported by the electric motor, and a control device including a connector having three connection terminals to which the motor terminals are connected. The cover portion overlaps the entire connector when viewed from the axial direction of the electric motor, and the cover portion covers both the arrangement direction in which the three connection terminals are lined up and the axial direction. The connector overlaps at least a portion of the connector when viewed from the direction orthogonal to the connector, and does not overlap the connector when viewed from the arrangement direction.

As a result, the cover portion, which is a conductor, covers a portion of the connector, thereby improving compatibility with electromagnetic environments. Furthermore, even if the cover part exposes a part of the connector, the motor unit of the present disclosure has sufficient electromagnetic environment compatibility to withstand use. On the other hand, the required volume of the gearbox is smaller than when the gearbox covers the connector from all directions. Therefore, the gearbox of the present disclosure is lightweight compared to a case where the gearbox covers the connector from all directions. Therefore, the motor unit of the present disclosure can be lightweight and improve electromagnetic environment compatibility.

A desirable embodiment of the motor unit includes an insulating cover that is an insulator and is disposed between the connector and the cover part.

This improves the insulation between the connector and the cover portion, which is a conductor. This makes it difficult for the cover portion to affect the current flowing through the connector.

An electric power steering device according to one aspect of the present disclosure includes the above motor unit, and the control device controls the electric motor and causes the electric motor to generate an auxiliary steering torque.

Due to the high electromagnetic compatibility of the motor unit, the current supplied from the control device to the electric motor is less likely to be disturbed by radiated noise. Further, the electric power steering device can reduce noise propagated to radio broadcasts and the like by suppressing the generation of radiated noise.

According to the present disclosure, it is possible to provide a motor unit and an electric power steering device that can be lightweight and have improved electromagnetic environment compatibility.

FIG. 1 is a schematic diagram of an electric power steering device according to an embodiment. FIG. 2 is a perspective view of the electric power steering device according to the embodiment. FIG. 3 is a front view of the motor unit of the embodiment. FIG. 4 is a left side view of the motor unit of the embodiment. FIG. 5 is a sectional view taken along line AA in FIG. FIG. 6 is an enlarged view of FIG. 5. FIG. 7 is a perspective view of the insulating cover of the embodiment. FIG. 8 is a diagram showing the results of emission tests for the first comparative example, the second comparative example, and the example.

Hereinafter, the present invention will be explained in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments (hereinafter referred to as embodiments). Furthermore, the constituent elements in the embodiments below include those that can be easily imagined by those skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the embodiments below can be combined as appropriate.

(Embodiment)
FIG. 1 is a schematic diagram of an electric power steering device according to an embodiment. FIG. 2 is a perspective view of the electric power steering device according to the embodiment. As shown in FIG. 1, the electric power steering device 80 includes a steering wheel 81, a steering shaft 82, a first universal joint 84, an intermediate shaft 85, and a second universal joint in the order in which force applied by an operator is transmitted. A joint 86 is connected to a pinion shaft 87. In the following description, the front of the vehicle in which the electric power steering device 80 is mounted is simply referred to as the front, and the rear of the vehicle is simply referred to as the rear.

As shown in FIG. 1, the steering shaft 82 includes an input shaft 82a and an output shaft 82b. One end of the input shaft 82a is connected to the steering wheel 81, and the other end of the input shaft 82a is connected to the output shaft 82b. Further, one end of the output shaft 82b is connected to the input shaft 82a, and the other end of the output shaft 82b is connected to the first universal joint 84.

As shown in FIG. 1, the intermediate shaft 85 connects the first universal joint 84 and the second universal joint 86. One end of the intermediate shaft 85 is connected to the first universal joint 84 , and the other end is connected to the second universal joint 86 . One end of the pinion shaft 87 is connected to the second universal joint 86, and the other end of the pinion shaft 87 is connected to the steering gear 88. Rotation of the steering shaft 82 is transmitted to the pinion shaft 87 via the intermediate shaft 85. That is, the intermediate shaft 85 rotates together with the steering shaft 82.

As shown in FIG. 1, the steering gear 88 includes a pinion 88a and a rack 88b. Pinion 88a is connected to pinion shaft 87. Rack 88b meshes with pinion 88a. Steering gear 88 converts the rotational motion transmitted to pinion 88a into linear motion using rack 88b. Rack 88b is connected to tie rod 89. The angle of the wheels changes as the rack 88b moves.

As shown in FIG. 1, the electric power steering device 80 includes a reduction gear device 92 and a motor unit 1. The speed reduction device 92 is, for example, a worm speed reduction device. The motor unit 1 includes an electric motor 2 and a control device 3. The torque generated by the electric motor 2 is transmitted to the worm wheel via the worm inside the reduction gear device 92, and rotates the worm wheel. The speed reduction device 92 increases the torque generated by the electric motor 2 using a worm and a worm wheel. The speed reducer 92 then applies auxiliary steering torque to the output shaft 82b. That is, the electric power steering device 80 is of a column assist type. The control device 3 is an ECU (Electronic Control Unit).

As shown in FIG. 1, the electric power steering device 80 includes a torque sensor 94 and a vehicle speed sensor 95. The electric motor 2, torque sensor 94, and vehicle speed sensor 95 are electrically connected to the control device 3. The torque sensor 94 outputs the steering torque transmitted to the input shaft 82a to the control device 3 through CAN (Controller Area Network) communication. Vehicle speed sensor 95 detects the running speed (vehicle speed) of the vehicle body on which electric power steering device 80 is mounted. The vehicle speed sensor 95 is provided in the vehicle body and outputs the vehicle speed to the control device 3 through CAN communication.

The control device 3 is attached to the electric motor 2 and controls the operation of the electric motor 2. For example, the control device 3 controls the electric motor 2 by PWM (Pulse Width Modulation) control. Switching noise due to PWM control may occur outside the control device 3. The control device 3 acquires signals from each of the torque sensor 94 and the vehicle speed sensor 95. Current is supplied to the control device 3 from a power supply device 99 (for example, a vehicle-mounted battery) while the ignition switch 98 is in an on state. The control device 3 calculates an auxiliary steering command value based on the steering torque and vehicle speed. The control device 3 adjusts the current value supplied to the electric motor 2 based on the auxiliary steering command value, and causes the electric motor 2 to generate an auxiliary steering torque. The control device 3 acquires information on the induced voltage from the electric motor 2 or information output from a resolver or the like provided in the electric motor 2 . The control device 3 controls the electric motor 2 and causes the electric motor 2 to generate auxiliary steering torque, thereby reducing the force required to operate the steering wheel 81.

FIG. 3 is a front view of the motor unit of the embodiment. FIG. 4 is a left side view of the motor unit of the embodiment. FIG. 5 is a sectional view taken along line AA in FIG. FIG. 6 is an enlarged view of FIG. 5. FIG. 7 is a perspective view of the insulating cover of the embodiment.

In the following description, an XYZ orthogonal coordinate system is used. The X-axis is parallel to the direction in which the connection terminals 355 of the connector 35 are lined up (arrangement direction). The Y-axis is perpendicular to the X-axis and the rotation axis R of the electric motor 2. The Z-axis is parallel to the rotation axis R of the electric motor 2. A direction parallel to the X axis is described as an X direction. A direction parallel to the Y axis is described as a Y direction. A direction parallel to the Z axis is referred to as a Z direction. Among the Y directions, the direction from the electric motor 2 toward the control device 3 is defined as the +Y direction. Among the Z directions, the direction from the insulating cover 5 toward the connector 35 is defined as the +Z direction. The right direction when facing the +Z direction with the +Y direction up is the +X direction.

As shown in FIG. 3, the motor unit 1 includes an electric motor 2 and a control device 3. In the motor unit 1, an electric motor 2 and a control device 3 are arranged close to each other. In the following description, a direction parallel to the rotation axis R of the electric motor 2 will be referred to as an axial direction. A direction perpendicular to the axial direction is described as a radial direction. A direction along a circle centered on the rotation axis R is described as a circumferential direction.

As shown in FIGS. 3 to 5, the electric motor 2 includes a motor case 21, a gear box 23, and a motor terminal 25. The motor case 21 is a substantially cylindrical member made of metal, for example. The motor case 21 contains a rotor, a stator, and the like. The rotor rotates around a rotation axis R. A coil is wound around the stator. The coil is supplied with three-phase alternating current. Motor case 21 is made of metal.

Gear box 23 is made of metal. Gear box 23 is a conductor. Gear box 23 is arranged at one end of motor case 21 . For example, the gear box 23 houses a worm wheel and a worm gear. As shown in FIG. 3, the gear box 23 includes a gear box main body 230, a support portion 231, and a cover portion 4. Gear box main body 230 is a member that closes an opening at one end of motor case 21 . Gear box main body 230 has a substantially disc shape. The support portion 231 protrudes from the outer peripheral surface of the gear box main body portion 230 in the +Y direction. Gear box 23 includes two supports 231. The cover portion 4 protrudes from the outer peripheral surface of the gear box main body portion 230 in the +Y direction. When viewed from the Z direction, the cover part 4 is arranged between the two support parts 231. As shown in FIG. 4, the cover part 4 includes a side wall part 41 and an upper wall part 43. The side wall portion 41 is a plate-shaped member extending in the +Y direction from the outer peripheral surface of the gear box main body portion 230. The thickness direction of the side wall portion 41 is parallel to the Z direction. The upper wall portion 43 is a plate-shaped member extending in the +Z direction from the end of the side wall portion 41 in the +Y direction. The thickness direction of the upper wall portion 43 is parallel to the Y direction.

The motor terminal 25 shown in FIG. 5 is a conductor, and is a member that connects the coil and the control device 3. Motor terminal 25 is made of metal. The electric motor 2 includes three motor terminals 25. The three motor terminals 25 are arranged in a line as shown in FIG. Three-phase alternating current generated by the control device 3 is supplied to the coils via three motor terminals 25. Motor terminal 25 extends radially outward from gearbox 23 . Motor terminal 25 extends outward between motor case 21 and gear box 23 .

As shown in FIGS. 3 to 5, the control device 3 includes a control device case 31, a board 36, a connector 34, and a connector 35. The control device case 31 includes a main body 32 and a lid 33. The main body 32 and the lid 33 are made of metal. The main body 32 and the lid 33 are conductors. The main body 32 is a member that supports the substrate 36. The main body 32 of this embodiment is also a member for promoting heat dissipation of the substrate 36. That is, the main body 32 also functions as a heat sink. The bottom surface of the main body 32 faces the outer peripheral surface of the motor case 21. The main body 32 is supported by the gear box 23. More specifically, the main body 32 is attached to the support part 231 of the gearbox 23 by a fixing member 39. The lid 33 is attached to the main body 32 so as to cover the substrate 36.

The board 36 is a printed circuit board made of resin or the like, for example. The board 36 is attached to the main body 32 with screws or the like. The board 36 includes a plurality of electronic components that constitute a control circuit and a plurality of electronic components that constitute a power supply circuit. The board 36 serves both as a control circuit board and a power supply circuit board. The substrate 36 includes a plurality of motor drive elements 37. The motor drive element 37 is an FET (Field Effect Transistor). Switching noise is generated by the motor drive element 37. The motor drive element 37 is arranged in a portion of the board 36 near the connector 35. By reducing the effect of switching noise generated by the motor drive element 37 on the connector 35, electromagnetic compatibility (EMC) is improved. Connector 34 is attached to main body 32. Connector 34 is connected to other equipment other than motor terminal 25.

The connector 35 is a member to which the motor terminal 25 is connected. As shown in FIG. 4, the connector 35 is arranged so as not to be covered by the lid 33 of the control device case 31. As shown in FIG. That is, the connector 35 is exposed from the control device case 31.

As shown in FIG. 6, the connector 35 includes a connector case 350 and three connection terminals 355. Connector case 350 is attached to main body 32 of control device case 31. Connection terminal 355 is a conductor supported by connector case 350. The connection terminal 355 is made of metal. The three connection terminals 355 are arranged in a line as shown in FIG. The connection terminal 355 is connected to the motor terminal 25 by the mounting member 38. Specifically, after the motor terminal 25 is inserted between the head of the mounting member 38 and the connection terminal 355, the mounting member 38 is tightened. The connection terminal 355 is connected to the substrate 36.

As shown in FIG. 6, the insulating cover 5 is a member attached to the control device case 31 so as to surround the connector 35. The insulating cover 5 is an insulator. For example, the insulating cover 5 is made of resin. More specifically, the insulating cover 5 is made of polycarbonate. As shown in FIG. 7, the insulating cover 5 includes a base 51, two arm parts 53, two claw parts 57, two side parts 54, a top part 55, and a bottom part 58.

As shown in FIG. 7, the base 51 is a plate-shaped member orthogonal to the Z-axis. The arm portions 53 are arranged at both ends of the base portion 51 in the X direction. The arm portion 53 extends from the base portion 51 in the +Z direction. The claw portion 57 is arranged at the tip of the arm portion 53. The width of the claw portion 57 decreases as it moves away from the arm portion 53. The side parts 54 are arranged at both ends of the base part 51 in the X direction. The side surface portion 54 is arranged in the −Y direction of the arm portion 53. The side surface portion 54 is a plate-shaped member orthogonal to the X-axis.

The upper surface portion 55 is arranged at the end of the base portion 51 in the +Y direction. The upper surface portion 55 is a plate-shaped member orthogonal to the Y axis. The upper surface portion 55 includes two holes 551. The bottom surface portion 58 is arranged at the end of the base portion 51 in the −Y direction. The bottom portion 58 is a plate-shaped member orthogonal to the Y-axis.

When attaching the insulating cover 5 to the connector 35, the protrusion provided on the connector 35 is fitted into the hole 551 of the upper surface portion 55. Thereafter, the arm portion 53 is pushed into the connector 35. The arm portion 53 is elastically deformed by the reaction force that the claw portion 57 receives from the connector 35 . When the claw portion 57 reaches the recess provided in the connector 35, the elastic deformation of the arm portion 53 returns and the claw portion 57 fits into the recess. Thereby, the insulating cover 5 is attached to the connector 35. In this way, the insulating cover 5 can be attached to the connector 35 in one operation without using a fixing member or the like. Further, by covering the connector 35 with the insulating cover 5, intrusion of foreign matter into the connector 35 is suppressed. Furthermore, since the claw portion 57 fits into the recess, the insulating cover 5 is less likely to fall off from the connector 35.

As shown in FIGS. 3 and 4, the cover part 4 covers a part of the connector 35. As shown in FIGS. The side wall portion 41 of the cover portion 4 overlaps the entire connector 35 when viewed from the Z direction. That is, the side wall portion 41 covers the entire surface of the connector 35 on the −Z direction side. The upper wall portion 43 of the cover portion 4 overlaps at least a portion of the connector 35 when viewed from the Y direction. That is, the upper wall portion 43 covers at least a portion of the surface of the connector 35 on the +Y direction side. The cover portion 4 does not overlap the connector 35 when viewed from the X direction. That is, the cover portion 4 does not cover the surface of the connector 35 on the +X direction side and the surface on the −X direction side. The cover part 4 is arranged outside the connector 35 when viewed from the X direction. The cover portion 4 exposes the connector 35 in the X direction.

FIG. 8 is a diagram showing the results of emission tests for the first comparative example, the second comparative example, and the example. The emission tests conducted on the first comparative example, the second comparative example, and the example are tests that evaluate unnecessary radiation emitted from in-vehicle electronic equipment to the outside, and are tests that comply with the CISPR25 standard. be. The motor units of the comparative example, the first comparative example, the second comparative example, and the example as an EUT (example) are placed on a horizontal reference ground plane while being connected to a load via a harness. An antenna is placed horizontally at a predetermined distance from the harness. The first comparative example is a motor unit that does not include the cover portion 4 described above. The second comparative example is a motor unit that includes a side wall portion 41 but does not include an upper wall portion 43. An example is the motor unit 1 described above. That is, the embodiment is a motor unit in which the gear box 23 includes a cover section 4 having a side wall section 41 and an upper wall section 43. FIG. 8 shows the average value of the measured radiation noise voltage per minute. FIG. 8 shows the results of an emission test conducted with the motor unit 1 placed on the reference ground plane so that the Z direction of the above-mentioned XYZ orthogonal coordinate system is the vertical direction and the +X direction is directed toward the antenna.

As shown in FIG. 8, in the example, the measured radiation noise is more likely to be reduced than in the first comparative example and the second comparative example. That is, the embodiment can improve electromagnetic environment compatibility more than the first comparative example and the second comparative example.

As explained above, the motor unit 1 of this embodiment includes the electric motor 2 and the control device 3. The electric motor 2 includes a cylindrical motor case 21 , a gear box 23 that is a conductor disposed at one end of the motor case 21 , and a motor terminal 25 that extends radially outward of the gear box 23 . The control device 3 includes a control device case 31 supported by the electric motor 2, and a connector 35 having three connection terminals 355 to which the motor terminals 25 are connected. The gear box 23 includes a cover portion 4 that covers a portion of the connector 35. The cover portion 4 overlaps the entire connector 35 when viewed from the axial direction (Z direction) of the electric motor 2. The cover portion 4 overlaps at least a portion of the connector 35 when viewed from a direction (Y direction) perpendicular to both the arrangement direction (X direction) and the axial direction (Z direction) in which the three connection terminals 355 are lined up. . The cover portion 4 does not overlap the connector 35 when viewed from the arrangement direction (X direction).

As a result, the cover part 4, which is a conductor, covers a part of the connector 35, thereby improving compatibility with the electromagnetic environment as shown in FIG. Further, even if the cover part 4 exposes a part of the connector 35, the motor unit 1 of this embodiment has sufficient electromagnetic environment compatibility to withstand use. More specifically, the motor unit 1 has improved resistance to switching noise caused by the PWM control of the control device 3. On the other hand, compared to the case where the gear box 23 covers the connector 35 from all directions, the required volume of the gear box 23 becomes smaller. Therefore, the gear box 23 of this embodiment is lighter than the case where the gear box 23 covers the connector 35 from all directions. Therefore, the motor unit 1 of this embodiment can be made lighter and have improved electromagnetic environment compatibility.

The motor unit 1 of this embodiment includes an insulating cover 5 that is an insulator and is disposed between the connector 35 and the cover part 4.

This improves the insulation between the connector 35 and the cover portion 4, which is a conductor. Therefore, the cover portion 4 is less likely to affect the current flowing through the connector 35.

The electric power steering device 80 of this embodiment includes a motor unit 1. The control device 3 controls the electric motor 2 and causes the electric motor 2 to generate an auxiliary steering torque.

Since the motor unit 1 has high electromagnetic compatibility, the current supplied from the control device 3 to the electric motor 2 is less likely to be disturbed by radiated noise. Further, the electric power steering device 80 can reduce noise propagated to radio broadcasts and the like by suppressing the generation of radiated noise.

1 Motor unit 2 Electric motor 3 Control device 4 Cover part 5 Insulating cover 21 Motor case 23 Gear box 25 Motor terminal 31 Control device case 32 Main body 33 Lid 34 Connector 35 Connector 36 Board 37 Motor drive element 38 Mounting member 39 Fixing member 41 Side wall Part 43 Upper wall part 51 Base part 53 Arm part 54 Side part 55 Top part 57 Claw part 58 Bottom part 80 Electric power steering device 81 Steering wheel 82 Steering shaft 82a Input shaft 82b Output shaft 84 First universal joint 85 Intermediate shaft 86 Second Universal joint 87 Pinion shaft 88 Steering gear 88a Pinion 88b Rack 89 Tie rod 92 Reducer 94 Torque sensor 95 Vehicle speed sensor 98 Ignition switch 99 Power supply 230 Gear box body 231 Support part 350 Connector case 355 Connection terminal 551 Hole R Rotating shaft

Claims (3)

an electric motor including a cylindrical motor case, a gearbox that is a conductor disposed at one end of the motor case, and a motor terminal extending radially outward of the gearbox;
a control device including a control device case supported by the electric motor, and a connector having three connection terminals to which the motor terminals are connected;
Equipped with
The gear box includes a cover portion that protrudes radially outward from an outer peripheral surface of the gear box and covers a part of the connector while being separated from the connector ,
The cover portion overlaps the entire connector when viewed from the axial direction of the electric motor, and overlaps the entire connector when viewed from a direction perpendicular to both the arrangement direction in which the three connection terminals are lined up and the axial direction. A motor unit that overlaps at least a portion of the connector and does not overlap the connector when viewed from the arrangement direction. The motor unit according to claim 1, further comprising an insulating cover that is an insulator and is disposed between the connector and the cover part. comprising the motor unit according to claim 1 or 2,
An electric power steering device, wherein the control device controls the electric motor and causes the electric motor to generate an auxiliary steering torque.

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