Motor device

Abstract

A motor device (10) comprises: a motor case (21) having a peripheral wall; a stator (22) fitted to the inner peripheral surface of the motor case; and a rotor (23) disposed inside the stator. The motor case has a first end part and a second end part, which are positioned on the opposite side of each other in the axial direction, and the motor case is configured such that the second end part can be attached to an attachment object (30). The second end part includes an attachment part (17A) that is provided to an outer peripheral surface of the second end part and that is configured to attach the motor case to the attachment object. The outer peripheral surface of the motor case has a groove (21B), and the groove is provided in a region of the motor case, which region is on the side opposite from the attachment object with respect to the attachment part and is in the circumferential direction of the motor case corresponding to at least the attachment part.

Description

Motor device

[0001] The present disclosure relates to a motor device.

[0002] Conventionally, motor devices are used to drive various mechanical devices. A motor device has, for example, a case, a stator, and a rotor. The case, stator, and rotor are each cylindrical bodies with a circular cross-sectional shape. The stator is fixed to the inner peripheral surface of the case. The rotor is inserted axially into the stator. The rotor is rotatable relative to the inner peripheral surface of the stator.

[0003] When the motor device is driven, magnetic attractive and repulsive forces act between the stator and rotor. This causes the stator to expand and contract radially. This expansion and contraction refers to the expansion and contraction of the stator's outer diameter. This expansion and contraction of the stator generates vibrations, which may result in noise. Furthermore, the vibrations may be transmitted to the object on which the motor device is mounted via the case.

[0004] For example, the motor device in Patent Document 1 is attached to a steering column of a vehicle. The steering column is fixed to the vehicle body via a bracket. The bracket has a cylindrical flange into which the steering column is inserted. An elastic body is interposed between the flange and the steering column. By elastically supporting the steering column with the elastic body, vibrations from the motor device are prevented from being transmitted to the vehicle body via the steering column.

[0005] Japanese Patent Application Laid-Open No. 2003-63420

[0006] The motor device disclosed in Patent Document 1 can indeed suppress the transmission of vibrations from the motor device. However, it requires the provision of a separate elastic body. Depending on the product specifications, it may be necessary to suppress the transmission of vibrations from the motor device while minimizing the number of parts.

[0007] A motor device according to one aspect of the present disclosure includes a motor case having a peripheral wall, a stator fitted to an inner peripheral surface of the motor case, and a rotor disposed inside the stator. The motor case has a first end and a second end located axially opposite each other, and the second end is configured to be attached to an attachment target. The second end has an attachment portion configured to attach the motor case to the attachment target, the attachment portion being provided on an outer peripheral surface of the second end. The outer peripheral surface of the motor case has a groove, and the groove is provided in a region of the motor case opposite the attachment target with respect to the attachment portion, at least in a circumferential region of the motor case corresponding to the attachment portion.

[0008] Fig. 1 is a perspective view of a motor device according to one embodiment. Fig. 2 is a cross-sectional view of the motor of Fig. 1 cut in a direction perpendicular to the axial direction. Fig. 3 is a perspective view showing the expansion and contraction deformation of the motor of Fig. 1. Fig. 4 is a cross-sectional view showing the main parts of the motor of Fig. 1. Fig. 5 is a graph showing the degree of deformation of a mounting part of a comparative example having no groove and the degree of deformation of a mounting part of one embodiment having a groove. Fig. 6 is a cross-sectional view showing the main parts of a motor according to another embodiment.

[0009] A motor device according to one embodiment will be described. <Overall Configuration of Motor Device 10> As shown in Fig. 1, motor device 10 has a motor 11 and an electronic control device 12. Motor 11 is, for example, a three-phase brushless motor. The three phases are U-phase, V-phase, and W-phase. Electronic control device 12 is provided at a first end of motor 11. Electronic control device 12 controls the driving of motor 12. Electronic control device 12 has a case and a circuit board housed in the case. The circuit board has electronic components for controlling the driving of motor 11.

[0010] The second end of the motor 11 has an end wall 13. The second end is the end opposite the first end in the axial direction of the motor 11. The end wall 13 is a circular wall that extends in a direction perpendicular to the axial direction of the motor 11 and closes the second end of the motor 11. The end wall 13 has a mating recess 14. The mating recess 14 is a concave portion into which a portion of the mounting object of the motor device 10 is fitted. The mating recess 14 opens in the direction from the first end to the second end of the motor 11.

[0011] The motor 11 has an output shaft 16. The axis of the output shaft 16 coincides with the axis of the motor 11. A first end of the output shaft 16 is located inside the motor 11. A second end of the output shaft 16 passes through the end wall 13 without contacting the end wall 13 and is exposed inside the fitting recess 14. The protruding height of the output shaft 16 from the end wall 13 is, for example, the same as the depth of the fitting recess 14. The depth is the axial length of the fitting recess 14. However, the protruding height of the output shaft 16 from the end wall 13 may be greater than the depth of the fitting recess 14. In other words, the output shaft 16 may protrude from the outer surface of the end wall 13.

[0012] The motor 11 has, for example, two mounting portions 17. The mounting portions 17 are portions for mounting the motor 11 to a mounting object. The mounting portions 17 are provided on the outer peripheral surface of a second end of the motor 11. The two mounting portions 17 extend radially opposite each other in the motor 11. The mounting portions 17 have two end faces located opposite each other in the axial direction of the motor 11. The first end face is the face of the mounting portion 17 closer to the electronic control device 12 in the axial direction of the motor 11. The second end face is the face of the mounting portion 17 farther from the electronic control device 12 in the axial direction of the motor 11, and is flush with the outer surface of the end wall 13. The mounting portion 17 has a threaded hole 17A. The threaded hole 17A penetrates the mounting portion 17 in the axial direction of the motor 11. The inner peripheral surface of the threaded hole 17A has a female thread.

[0013] The motor device 10 is attached to an object via the attachment portion 17. The object is, for example, a reducer. One example of a reducer is a worm reducer. A worm reducer has a worm wheel, a worm, and a reducer housing. The worm wheel and the worm are housed inside the reducer housing. The motor device 10 is attached to the reducer housing via the attachment portion 17. The worm wheel is, for example, attached to a shaft so as to be rotatable integrally with the shaft. The worm is coaxially connected to the output shaft 16. The worm wheel and the worm mesh with each other. The rotation of the motor 11 is transmitted to the shaft via the reducer. The shaft may be a steering shaft of a vehicle, or a pinion shaft that meshes with rack teeth of a steered shaft.

[0014] <Detailed Configuration of Motor 11> Next, a detailed description will be given of the configuration of the motor 11. As shown in Fig. 2, the motor 11 has a motor case 21, a stator 22, and a rotor 23. The motor case 21, the rotor 23, and the stator 22 are each a cylindrical body having a circular cross-sectional shape.

[0015] The outer peripheral surface of the stator 22 is fitted to the inner peripheral surface of the motor case 21. The stator 22 has a core 22A and multiple coils 22B. The core 22A is made up of multiple split cores arranged closely together along the inner peripheral surface of the motor case 21. The split cores have teeth. The teeth are provided on the inner peripheral surface of the split cores. The coils 22B are wound around the teeth via insulators.

[0016] The rotor 23 is disposed inside the stator 22. The rotor 23 has a rotor core 23A and a plurality of rotor magnets 23B. The rotor core 23A is rotatable integrally with the output shaft 16. The output shaft 16 passes through the rotor core 23A in the axial direction. The rotor magnets 23B are permanent magnets and are fixed to the outer peripheral surface of the rotor core 23A at intervals in the circumferential direction. The rotor magnets 23B are magnetized in the radial direction of the rotor core 23A. The magnetization directions of two circumferentially adjacent rotor magnets 23B are opposite to each other.

[0017] When energized, the coil 22B generates a magnetic field, which generates a magnetic attractive force F1 and a magnetic repulsive force F2 between the stator 22 and the rotor 23. The rotor 23 rotates due to the magnetic attractive force F1 and the magnetic repulsive force F2.

[0018] The motor 11 is, for example, a "10-pole, 12-slot" motor. That is, the motor 11 has 10 poles and 12 slots. The number of poles is the number of magnetic poles of the rotor 23. The number of slots is the number of spaces between two circumferentially adjacent teeth, and is the number of spaces in which the coils 22B can be accommodated.

[0019] As shown in Figure 4, the stator 22 has a first end and a second end. The first end is the end of the stator 22 farther from the end wall 13. The second end is the end of the stator 22 closer to the end wall 13. The second end has a small diameter portion 22C. The small diameter portion 22C is a portion of the stator 22 that has a smaller outer diameter than the other portions.

[0020] The peripheral wall of the motor case 21 has a thick portion 21A. The thick portion 21A is a portion of the peripheral wall of the motor case 21 that is thicker than other portions. The thick portion 21A is provided at the second end of the motor case 21. The outer peripheral surface of the small diameter portion 22C of the stator 22 is press-fitted into the inner peripheral surface of the thick portion 21A. The press-fitting is achieved by applying pressure to push the second end of the stator 22 into the inner peripheral surface of the thick portion 21A. A portion of the small diameter portion 22C axially overlaps a portion of the mounting portion 17. In other words, a portion of the small diameter portion 22C faces a portion of the mounting portion 17 in the radial direction, with the thick portion 21A interposed therebetween.

[0021] The end wall 13 has a bearing holder 25. The bearing holder 25 is provided on the inner surface of the end wall 13. The inner surface is the end face of the end wall 13 opposite the attachment target 30. The bearing holder 25 is a cylindrical body with a circular cross-sectional shape. The outer peripheral surface of a bearing 26 is fitted into the inner peripheral surface of the bearing holder 25. A second end of the output shaft 16 is rotatably supported relative to the motor case 21 via the bearing 26. The second end of the output shaft 16 passes through the end wall 13 in the axial direction without contacting the end wall 13.

[0022] <Mounting Structure of Motor Device 10> Next, the mounting structure of the motor device 10 will be described. As shown in FIG. 4, the mounting object 30 has a housing 31. The housing 31 has a mounting surface 32. The mounting surface 32 is the surface of the housing 31 to which the motor device 10 is fixed. The mounting surface 32 has a fitting protrusion 33. The fitting protrusion 33 is a cylindrical body with a circular cross-section. The outer diameter of the fitting protrusion 33 is approximately the same as the inner diameter of the fitting recess 14. The outer peripheral surface of the fitting protrusion 33 fits into the inner peripheral surface of the fitting recess 14. The housing 31 has an insertion hole 31A. The output shaft 16 or a worm connected to the output shaft 16 is inserted into the insertion hole 16. For ease of explanation, the worm is not shown in FIG. 4.

[0023] The housing 31 has two fastening portions 34. The fastening portions 34 are flat plate-shaped portions of the housing 31 that correspond to the mounting portion 17 in the axial direction. The fastening portions 34 have two end faces that are located opposite each other in the axial direction. The first end face is the face of the fastening portion 34 on the motor device 11 side. The second end face is the face of the fastening portion 34 on the opposite side from the motor device 11. The first end face of the fastening portion 34 is maintained in contact with the second end face of the mounting portion 17.

[0024] The fastening portion 34 has an insertion hole 34A. The insertion hole 34A passes through the fastening portion 34 in the axial direction. The screw hole 17A of the mounting portion 17 is aligned with the insertion hole 34A of the housing 31. The motor device 10 is fixed to the housing 31 by a bolt 35. The bolt 35 is fastened to the screw hole 17A through the insertion hole 34A.

[0025] <Regarding the Expansion / Contraction Vibration of the Motor 11> As shown in Figure 2, when the motor 11 is driven, a magnetic attractive force F1 and a magnetic repulsive force F2 are generated between the stator 22 and the rotor 23, causing the stator 22 to expand and contract in the radial direction. The expansion and contraction refers to the expansion and contraction of the outer diameter of the stator 22. The manner in which the stator 22 deforms is determined by the relationship between the number of poles and the number of slots of the motor 11. That is, the outer periphery of the stator 22 deforms so that two or more enlarged-diameter portions and two or more reduced-diameter portions alternate at equal angular intervals, and the number of enlarged-diameter portions and reduced-diameter portions is equal to the greatest common divisor of the number of poles and the number of slots of the motor 11. The enlarged-diameter portions are the expanded-diameter portions of the stator 22. The reduced-diameter portions are the reduced-diameter portions of the stator 22.

[0026] For example, if the motor 11 is a "10-pole, 12-slot" motor, the greatest common divisor between the number of poles and the number of slots of the motor 11 is "2." Therefore, as shown by the two-dot chain line in FIG. 2 , when viewed from the axial direction of the stator 22, the expanded diameter portions 24A and the reduced diameter portions 24B are alternately formed at 90° intervals around the circumferential direction of the stator 22. As a result, when viewed from the axial direction, the outer periphery of the stator 22 elastically deforms into an ellipse. When viewed from the axial direction, the outer periphery of the stator 22 elastically deforms so that the ellipse rotates along with the rotation of the rotor 23. In other words, as the rotor 23 rotates, the position of the major axis of the ellipse moves sequentially around the circumferential direction.

[0027] As shown by the dashed line in Figure 3, the peripheral wall of the motor case 21 deforms in such a way that it bulges outward in the radial direction in the long axis direction of the deformed stator 22. Conversely, as shown by the dashed line in Figure 3, the peripheral wall of the motor case 21 deforms in such a way that it contracts inward in the radial direction in the short axis direction of the deformed stator 22. The expansion and contraction deformation of the peripheral wall of the motor case 21 induces deformation of the mounting portions 17 of the motor 11 in the axial direction, i.e., in the up and down direction in Figure 3. As the peripheral wall of the motor case 21 expands and contracts, the two mounting portions 17 swing in the same direction.

[0028] The expansion and contraction deformation of the stator 22 raises the following concerns. Specifically, the expansion and contraction deformation of the stator 22 contributes to vibration of the stator 22. The vibration of the stator 22 is transmitted to the object to which the motor device 10 is attached via the motor case 21. In particular, the axial swing of the attachment portion 17 makes it easier for the vibration to be transmitted to the object to which the motor device 10 is attached.

[0029] If the shaft is a steering shaft of a vehicle, vibrations may be transmitted to the steering shaft via the reduction gear, causing vibrations in the steering shaft and, ultimately, the steering wheel connected to the steering shaft. There is also concern that vibrations of the stator 22 may cause noise.

[0030] Therefore, in this embodiment, the following configuration is adopted to suppress the transmission of vibrations caused by the expansion and contraction deformation of the stator 22 to the attachment object. <Configuration for suppressing vibration transmission> As shown in Fig. 1, the outer peripheral surface of the motor case 21 has a groove 21B. The groove 21B is provided around the entire circumference of the motor case 21. The groove 21B is located on the opposite side of the attachment portion 17 from the housing 31. The groove 21B is a constricted portion of the motor case 21. The constricted portion is a portion of the peripheral wall of the motor case 21 that has a smaller outer diameter than other portions.

[0031] As shown in Figure 4, groove 21B is provided on the outer peripheral surface of thick portion 21A. Groove 21B is, for example, a recess having an arc-shaped cross section. Groove 21B is adjacent to mounting portion 17 in the axial direction of motor 11. The inner surface of groove 21B smoothly continues to the first end face of mounting portion 17. Groove 21B is located between stator 22 and mounting portion 17 in the radial direction of motor 11.

[0032] <Operation of the Present Embodiment> This embodiment provides the following operation. The expansion and contraction of the peripheral wall of the motor case 21 induces deformation of the mounting portion 17 in the axial direction, i.e., the vertical direction in FIG. 3 . However, the motor case 21 has groove 21B. Groove 21B is located on the opposite side of the mounting portion 17 from the housing 31, and is adjacent to the mounting portion 17 in the axial direction of the motor 11. This reduces the rigidity of the portion of the motor case 21 where groove 21B is located, between the stator 22 and the mounting portion 17. This suppresses deformation of the mounting portion 17 that accompanies the expansion and contraction of the peripheral wall of the motor case 21.

[0033] 5, if the degree of deformation of the mounting portion 17 of the comparative example in which the motor case 21 does not have the groove 21B is taken as "100%, " the degree of deformation of the mounting portion 17 of the present embodiment is, for example, "58%." In other words, by providing the groove 21B in the motor case 21, the deformation of the mounting portion 17 is suppressed. Therefore, the transmission of vibrations caused by the expansion and contraction deformation of the stator 22 to the mounting portion 17 and, ultimately, to the mounting object 30 is suppressed.

[0034] Advantages of the Present Embodiment The present embodiment provides the following advantages. (1) The motor device 10 includes a motor case 21 having a peripheral wall, a stator 22 fitted to the inner peripheral surface of the motor case 21, and a rotor 23 disposed inside the stator 22. The motor case 21 has a first end and a second end located opposite each other in the axial direction, and the second end is attached to the attachment object 30. The second end has an attachment portion 17 for attaching the motor case 21 to the attachment object 30. The attachment portion 17 is provided on the outer peripheral surface of the second end of the motor case 21. The outer peripheral surface of the motor case 21 has a groove 21B. The groove 21B is provided in a region of the motor case 21 opposite the attachment object 30 with respect to the attachment portion 17. The groove 21B is provided around the entire circumference of the motor case 21.

[0035] This configuration reduces the rigidity of the portion of the motor case 21 where the groove 21B is provided between the stator 22 and the mounting portion 17. This suppresses deformation of the mounting portion 17 due to the expansion and contraction of the peripheral wall of the motor case 21. This makes it less likely that vibrations due to the expansion and contraction of the stator 22 will be transmitted to the mounting object 30. This also improves noise and vibration (NV) performance. This ensures quietness. Furthermore, there is no need to provide a separate component in the motor device 10 to suppress transmission of vibrations from the motor device 10 to the mounting object 30. This prevents an increase in the number of components in the motor device 10 and reduces the production cost of the motor device 10.

[0036] (2) The groove 21B is adjacent to the mounting portion 17 in the axial direction of the motor case 21. With this configuration, deformation of the mounting portion 17 due to expansion and contraction of the peripheral wall of the motor case 21 can be more effectively suppressed.

[0037] (3) The second end of the motor case 21 has a thick portion 21A that is thicker than the other portions of the peripheral wall of the motor case 21. The groove 21B is provided on the outer peripheral surface of the thick portion 21A. With this configuration, the strength of the motor case 21 can be ensured while the depth of the groove 21B can be ensured.

[0038] (4) The stator 22 and the mounting portion 17 overlap in the axial direction of the motor 11. In a motor device 10 configured in this manner, the expansion and contraction deformation of the peripheral wall of the motor case 21 is directly transmitted to the mounting portion 17, which may increase the amount of deformation of the mounting portion 17. Therefore, there is technical significance in providing the groove 21B in the motor case 21 to suppress the amount of deformation of the mounting portion 17.

[0039] Other Embodiments This embodiment may be modified as follows. As shown in FIG. 6 , the depth of the groove 21B may be increased as long as the strength of the motor case 21 is maintained. Increasing the depth of the groove 21B means extending the groove 21B radially inward of the motor case 21. The depth of the groove 21B may be equal to the difference between the inner diameter φ1 of the thick-walled portion 21A and the inner diameter φ2 of the portion of the peripheral wall of the motor case 21 other than the thick-walled portion 21A. This arrangement, as indicated by arrow R1, can lengthen the transmission path of vibrations caused by the expansion and contraction of the stator 22 while maintaining the strength of the motor case 21. This reduces the transmission of vibrations caused by the expansion and contraction of the stator 22 to the mounting portion 17 and, ultimately, to the mounting object 30. Furthermore, noise caused by vibrations caused by the expansion and contraction of the stator 22 can be reduced.

[0040] Groove 21B does not have to be continuous around the entire circumference of motor case 21. Groove 21B only needs to be provided in a region of motor case 21 on the opposite side of mounting portion 17 from mounting target 30, at least in a circumferential region of motor case 21 that corresponds to mounting portion 17. The "circumferential region of motor case 21 that corresponds to mounting portion 17" is a region of motor case 21 that is located at the same circumferential position as mounting portion 17. This configuration also makes it possible to suppress deformation of mounting portion 17 that accompanies expansion and contraction of the peripheral wall of motor case 21.

[0041] The groove 21B does not have to be adjacent to the mounting portion 17 in the axial direction of the motor 11. In other words, the groove 21B only needs to be provided on the outer peripheral surface of the thick portion 21A, and may be provided at a position away from the mounting portion 17 in the axial direction of the motor 11.

[0042] The peripheral wall of the motor case 21 does not have to have the thick portion 21A. In other words, the thickness of the peripheral wall may be constant in the axial direction. The number of mounting portions 17 is not limited to two. The number of mounting portions 17 may be three or four. The number of mounting portions 17 may also be five or more. The number of fastening portions 34 of the housing 31 is the same as the number of mounting portions 17.

[0043] The electronic control unit 12 may be omitted from the motor device 10. That is, the electronic control unit 12 may be separate from the motor 11. The motor device 10 may be a drive source for an electric power steering device. In this case, the motor 11 functions as an assist motor. The assist motor generates an assist force that is applied to the steering wheel.

[0044] Motor device 10 may be a drive source for a steer-by-wire steering device. In this case, motor 11 functions as a reaction motor or a steering motor. The reaction motor generates a steering reaction force applied to the steering wheel. The steering motor generates a steering force for steering the steered wheels of the vehicle.

[0045] The motor device 10 can be used as a drive source for various mechanical devices, not just a steering device for a vehicle. The mechanical device may be, for example, a machine tool driven by the motor 11.

Claims

1. A motor device comprising: a motor case having a peripheral wall; a stator fitted to the inner peripheral surface of the motor case; and a rotor arranged inside the stator, wherein the motor case has a first end and a second end located opposite each other in the axial direction, the second end being configured to be attached to an attachment target, the second end having an attachment part configured to attach the motor case to the attachment target, the attachment part being provided on the outer peripheral surface of the second end, the outer peripheral surface of the motor case having a groove, the groove being provided in an area of ​​the motor case on the opposite side of the attachment target from the attachment part, at least in a circumferential area of ​​the motor case corresponding to the attachment part.

2. The motor device according to claim 1, wherein the groove is adjacent to the mounting portion in the axial direction of the motor case.

3. A motor device according to claim 1 or claim 2, wherein the second end has a thick portion that is thicker than other portions of the peripheral wall of the motor case, and the groove is provided on the outer peripheral surface of the thick portion.

4. The motor device according to claim 3, wherein the depth of said groove is the same as the difference between the inner diameter of said thick portion and the inner diameter of said other portion.

5. The motor device according to claim 1 or 2, wherein the stator and the mounting portion have portions that overlap with each other in the axial direction.

6. A motor device according to claim 1 or 2, wherein the groove is provided along the entire periphery of the motor case.

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