In-wheel motor drive device installed in automobiles

Abstract

To provide an in-wheel motor drive device in which a first helical gear of a motor spindle and a second helical gear of an axle are engaged with each other, which can withstand the thrust load generated in the helical gear and also suppress the increase in the weight of a gear case.SOLUTION: A gear case of an in-wheel motor drive device stores first / second helical gears, has a first opening through which a motor spindle passes on the inner wall, and has a second opening through which an axle passes on the outer wall. The in-wheel motor drive device also includes a first thrust bearing which is mounted on the outer wall and supports the first helical gear and a second thrust bearing which is mounted on the inner wall and supports the second helical gear. The directions of the helical teeth of the first and second helical gears are set so that when the vehicle moves forward, the first helical gear is subjected to the thrust load toward the vehicle width direction outer side and the second helical gear is subjected to the thrust load toward the vehicle width direction center side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an in-wheel motor drive device mounted on an automobile. [Background technology]

[0002] Patent Document 1 discloses an example of an in-wheel motor drive device. In this in-wheel motor drive device, a motor main shaft and an axle connected to a wheel are parallel to each other, and a helical gear is fixed to each of them. The helical gear of the motor main shaft engages with the helical gear of the axle, transmitting torque from the motor main shaft to the axle. The axle is rotatably supported by the case via a cylindrical roller bearing and a ball bearing. The cylindrical roller bearing supports the load in the radial direction, and the ball bearing supports the load in the thrust direction. It is known that helical gears generate a large load in the thrust direction (thrust load). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-018735 Summary of the Invention [Problem to be solved by the invention]

[0004] The thrust loads applied to the first helical gear (the helical gear on the motor main shaft side) and the second helical gear (the helical gear on the axle side) are received by the gear case via thrust bearings. If the entire wall of the case is made thick enough to withstand the thrust load, the weight increases. If the entire wall of the case is made thin, the gear case may be deformed by the thrust load. This specification provides technology that can firmly withstand the thrust load generated in the helical gears while also suppressing an increase in the weight of the gear case. [Means for solving the problem]

[0005] The in-wheel motor drive device disclosed in this specification includes a motor case that houses a motor, and a gear case that is in contact with the outer side of the motor case in the vehicle width direction and that houses a first helical gear and a second helical gear. The first helical gear is fixed to the motor main shaft. The second helical gear is fixed to an axle. The axle is parallel to the motor main shaft, and the second helical gear is engaged with the first helical gear. The gear case is in contact with the motor case, and has a first opening in its wall (inner wall) facing the motor case, through which the motor main shaft (or the shaft of the first helical gear) passes, and a second opening in its wall (outer wall) on the outer side in the vehicle width direction, through which the axle passes. The in-wheel motor drive device further includes a first thrust bearing and a second thrust bearing. The first thrust bearing is attached to the outer wall of the gear case and rotationally supports the first helical gear. The second thrust bearing is attached to the inner wall of the gear case and rotationally supports the second helical gear. The first thrust bearing may support the rotation of the first helical gear via the motor main shaft, and the second thrust bearing may support the rotation of the second helical gear via the axle. The orientations of the helical teeth of the first helical gear and the second helical gear are set so that when the motor main shaft rotates in the direction moving the vehicle forward, a thrust load is applied to the first helical gear outward in the vehicle width direction, and a thrust load is applied to the second helical gear toward the center in the vehicle width direction.

[0006] The inner wall of the gear case is provided with a first opening along the motor main shaft through which the motor main shaft (or the shaft of the first helical gear) passes, resulting in low strength. However, no opening is required in the portion of the outer wall facing the first helical gear, resulting in high strength. When the vehicle moves forward, the thrust load generated by the first helical gear is directed outward in the vehicle width direction, and the outer wall, which has higher strength, receives the thrust load via the first thrust bearing. The outer wall of the gear case is provided with a second opening along the axle through which the axle passes, resulting in low strength. However, no opening is required in the portion of the inner wall facing the second helical gear, resulting in high strength. When the vehicle moves forward, the thrust load generated by the second helical gear is directed toward the center in the vehicle width direction, and the inner wall, which has higher strength, receives the thrust load via the second thrust bearing. The gear case can reliably receive the thrust load in the areas without openings. At the same time, because high thrust loads are not generated near the first and second openings of the gear case, there is no need to increase the thickness of those areas. The in-wheel motor drive device disclosed in this specification can withstand the thrust load generated in the helical gear, and also can suppress an increase in the weight of the gear case.

[0007] A rib is provided on the back surface of the outer wall of the motor case in the vehicle width direction, and the rib is preferably positioned so as to overlap with the axle when viewed from the axial direction of the axle. The rib of the motor case supports part of the thrust load acting on the second helical gear when traveling forward. Even if the thickness of the inner wall of the gear case (or the outer wall of the motor case) is made thin, the thrust load generated on the second helical gear can be firmly supported.

[0008] Alternatively, the peripheral wall of the motor case, which is parallel to the motor main shaft, may be configured to overlap the axle when viewed from the axial direction of the axle. The peripheral wall of the motor case supports part of the thrust load acting on the second helical gear during forward movement. Even if the thickness of the outer wall of the motor case (or the inner wall of the gear case) is thin, the thrust load acting on the second helical gear can be firmly supported.

[0009] The in-wheel motor drive device disclosed in this specification receives the thrust load generated when the motor main shaft rotates in the direction of forward movement of the vehicle on the wall of the gear case that has no opening. Details and further improvements of the technology disclosed in this specification will be described in the "Description of Embodiments" below. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of an in-wheel drive device according to a first embodiment. [Figure 2] 1 is a cross-sectional view of an in-wheel drive device according to a first embodiment (illustration of some components is omitted). [Figure 3] FIG. 10 is a diagram showing the positional relationship between the rib and the axle when viewed from the direction along the axle. [Figure 4] FIG. 10 is a cross-sectional view of an in-wheel drive device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) An in-wheel motor drive device 2 of a first embodiment will be described with reference to Figures 1-3. For ease of description, the in-wheel motor drive device 2 may be simply referred to as the drive device 2 below. The drive device 2 is mounted on an automobile 90. The automobile 90 is a type of electric vehicle, as it is propelled by a drive device 2 that includes an electric motor. The automobile 90 employs a drive device 2 for all four wheels. As the four drive devices 2 have the same structure, only one drive device 2 will be described below.

[0012] FIG. 1 shows a cross-sectional view of the drive unit 2. The top of FIG. 1 corresponds to the vertically upward direction, and the bottom corresponds to the vertically downward direction. The left-right direction of FIG. 1 corresponds to the width direction of the automobile 90. The automobile 90 is equipped with a drive unit 2 for each wheel, and FIG. 1 shows a cross-section of the drive unit 2 equipped at the right front part of the automobile 90. The right side of FIG. 1 corresponds to the outer side of the automobile 90 in the width direction, and the left side corresponds to the inner side of the automobile 90 in the width direction. In this embodiment, "inner side in the vehicle width direction" means the center side of the automobile 90. "Outer side in the vehicle width direction" may also be expressed as "the side closer to the wheel 91."

[0013] The drive unit 2 includes a motor 10 and an axle 30. The motor 10 includes a stator 11 and a rotor 12, which are housed in a motor case 14. The stator 11 is fixed to the motor case 14. The rotor 12 includes a motor main shaft 13, and the motor main shaft 13 (rotor 12) is rotatably supported by the motor case 14 via a ball bearing 15. A rib 17 is provided on the inner surface of the outer wall (outer wall 16) of the motor case 14 in the vehicle width direction. The effect of the rib 17 will be described later.

[0014] The axle 30 is parallel to the motor main shaft 13. In FIG. 1, the dashed-dotted line CL1 represents the axis of the motor main shaft 13, and the dashed-dotted line CL2 represents the axis of the axle 30. A first helical gear 21 is fixed to the motor main shaft 13, and a second helical gear 22 is fixed to the axle 30. A wheel 91 is connected to the outer end of the axle 30 in the vehicle width direction, and a tire 92 is fitted on the wheel 91.

[0015] The second helical gear 22 is engaged with the first helical gear 21, and the torque of the motor 10 is transmitted to the wheel 91 via the first and second helical gears 21 and 22. In other words, the rotation of the motor main shaft 13 is transmitted to the wheel 91 via the first and second helical gears 21 and 22. The motor main shaft 13, which includes the axis of the first helical gear 21, extends outside the motor case 14 along the vehicle width direction.

[0016] The first and second helical gears 21 and 22 are housed in a gear case 20. The gear case 20 is in contact with the motor case 14. More specifically, the gear case 20 is fixed to the outer wall 16 of the motor case 14. The gear case 20 is supported by a suspension arm (not shown). That is, the gear case 20 (drive unit 2) is supported on the body of the automobile 90 via a suspension arm (not shown).

[0017] 2 shows a cross section of the drive unit 2, with some components omitted. The detailed structure of the drive unit 2 will be described with reference to FIG.

[0018] The first helical gear 21 is fixed to the motor main shaft 13 and is rotatably supported by the gear case 20 by a pair of first thrust bearings 31a, 31b. The first thrust bearing 31a is attached to an outer wall 23 of the gear case 20, and the first thrust bearing 31b is attached to an inner wall 24 of the gear case 20. Here, the outer wall 23 (inner wall 24) refers to the wall of the gear case 20 on the outer side (center side) in the vehicle width direction.

[0019] The second helical gear 22 is fixed to the axle 30 and is rotatably supported by the gear case 20 by a pair of second thrust bearings 32a, 32b. The second thrust bearing 32a is attached to the outer wall 23, and the second thrust bearing 32b is attached to the inner wall 24. The axle 30 is rotatably supported by the gear case 20 by a pair of third thrust bearings 33.

[0020] The gear case 20 has a first opening 25 and a second opening 26. The first opening 25 is provided in an inner wall 24 of the gear case 20, and the motor main shaft 13 (shaft of the first helical gear 21) passes through it. The second opening 26 is provided in an outer wall 23 of the gear case 20, and the axle 30 (shaft of the second helical gear 22) passes through it.

[0021] The first thrust bearings 31a and 31b determine the thrust and radial positions of the first helical gear 21. In other words, the first thrust bearings 31a and 31b bear the thrust and radial loads applied to the first helical gear 21. The second thrust bearings 32a and 32b determine the thrust and radial positions of the second helical gear 22. In other words, the second thrust bearings 32a and 32b bear the thrust and radial loads applied to the second helical gear 22. The same applies to the third thrust bearing 33.

[0022] Typical thrust bearings include thrust ball bearings, thrust angular contact ball bearings, thrust cylindrical roller bearings, thrust needle bearings, thrust tapered roller bearings, and thrust spherical roller bearings. In Figures 1 and 2, the first and second thrust bearings 31 and 32 are depicted as thrust spherical roller bearings, but they may also be other types of thrust bearings.

[0023] As is well known, the tooth surfaces of helical gears are not parallel to the gear axis but are inclined. Therefore, when two helical gears engage to transmit power, a strong thrust load is generated on both helical gears. To maintain the axial position of the helical gears against this strong thrust load, thrust bearings are used to support the helical gears.

[0024] The first helical gear 21 and the second helical gear 22 are determined so that the orientation of the helical teeth (inclination of the tooth flank with respect to the axis) satisfies the following condition: That is, the orientation of the helical teeth is determined so that when the motor main shaft 13 rotates in the direction in which the automobile 90 moves forward, a thrust load toward the outside in the vehicle width direction is applied to the first helical gear 21, and a thrust load toward the inside (center) in the vehicle width direction is applied to the second helical gear 22. In other words, when the motor main shaft 13 rotates in the direction in which the automobile 90 moves forward, the tooth flank on the outside in the vehicle width direction of the second helical gear 22 abuts against the tooth flank on the center side in the vehicle width direction of the first helical gear 21.

[0025] For convenience of explanation, the rotation of the motor main shaft 13 in the direction in which the automobile 90 moves forward will be referred to as "forward rotation." The thick arrow line F1 in Fig. 2 indicates the thrust load generated on the first helical gear 21 during forward rotation of the motor main shaft, and the thick arrow line F2 indicates the thrust load generated on the second helical gear 22 during forward rotation. The thrust load generated on the first helical gear 21 and the thrust load generated on the second helical gear 22 have the same absolute value but are directed in opposite directions.

[0026] First thrust bearings 31 support rotation of the first helical gear 21 on both sides in the vehicle width direction. During forward rotation, the thrust load (thick arrow F1) is directed outward in the vehicle width direction, so the thrust load is concentrated on the first thrust bearing 31a, which is located on the outer side of the first helical gear 21 in the vehicle width direction. The first thrust bearing 31a is supported by the outer wall 23. Because no opening is provided in the portion of the outer wall 23 facing the first helical gear 21, the strength of this portion is higher than that of the portion of the inner wall 24 on the opposite side. The thrust load generated on the first helical gear 21 during forward rotation is firmly supported by the portion of the outer wall 23 without an opening. Meanwhile, the first opening 25 is provided in the portion of the inner wall 24 facing the first helical gear 21, so the strength of the area around the first opening 25 is lower (compared to the outer wall 23 on the opposite side). However, a high thrust load is not applied around the first opening 25. Since it is not necessary to increase the strength of the inner wall 24 around the first opening 25, an increase in the weight of the gear case 20 can be suppressed.

[0027] The same applies to the thrust load generated on the second helical gear 22. During forward rotation, the thrust load generated on the second helical gear 22 is directed toward the center in the vehicle width direction. The thrust load is concentrated on the second thrust bearing 32b, which is located near the center in the vehicle width direction of the second helical gear 22. The second thrust bearing 32b is supported by the inner wall 24. Because no opening is provided in the portion of the inner wall 24 that faces the second helical gear 22, the strength of this portion is higher than that of the portion of the outer wall 23 on the opposite side. The thrust load generated on the second helical gear 22 during forward rotation is firmly supported by the portion of the inner wall 24 that does not have an opening. On the other hand, because the second opening 26 is provided in the portion of the outer wall 23 that faces the second helical gear 22, the strength of the area around the second opening 26 is lower (compared to the inner wall 24 on the opposite side). However, a high thrust load is not applied to the area around the second opening 26. Since it is not necessary to increase the strength of the outer wall 23 around the second opening 26, an increase in the weight of the gear case 20 (drive device 2) can be suppressed.

[0028] A rib 17 is provided on the back surface of the outer wall 16 of the motor case 14 (see Figure 1). The arrangement of the rib 17 and the axle 30 will be explained. Figure 3 shows the positional relationship between the rib 17 and the axle 30 when viewed from the axial direction of the axle 30. As shown in Figure 3, the rib 17 overlaps with the axle 30 when viewed from the axial direction of the axle 30. A portion of the thrust load acting on the second helical gear 22 is supported by the rib 17 of the motor case 14. Even if the thickness of the outer wall 16 of the motor case 14 (or the inner wall 24 of the gear case 20) is reduced, the rib 17 firmly supports the thrust load generated on the second helical gear 22 during forward rotation.

[0029] Second Embodiment Figure 4 shows a cross-sectional view of a drive unit 2a of a second embodiment. The shape of the motor case 14a of the drive unit 2a is different from that of the drive unit 2 of the first embodiment. Other than the shape of the motor case 14a, the structure of the drive unit 2a is the same as that of the drive unit 2 of the first embodiment.

[0030] The motor case 14a has an outer diameter smaller than that of the motor case 14 of the drive unit 2 of the first embodiment. A peripheral wall 18, which is a wall of the motor case 14a and is parallel to the motor main shaft 13, is positioned so as to overlap with the axle 30 when viewed in the axial direction of the axle 30. In FIG. 4, the axis CL2 of the axle 30 passes through the peripheral wall 18. With this configuration, the peripheral wall 18 of the motor case 14a supports part of the thrust load acting on the second helical gear 22. Even if the thickness of the outer wall 16 of the motor case (or the inner wall 24 of the gear case 20) is reduced, the peripheral wall 18 firmly supports the thrust load generated in the second helical gear 22.

[0031] As described above, the drive unit 2 (2a) of the embodiment can firmly withstand the thrust load generated in the helical gears, and can also suppress an increase in the weight of the gear case 20 (drive unit 2, 2a). The drive unit 2 (2a) can firmly withstand the thrust load generated in the helical gears 21, 22, particularly when the automobile 90 moves forward (when the motor main shaft 13 rotates forward).

[0032] Points to note regarding the technology described in the embodiment will be described. A pair of first thrust bearings 31a, 31b are arranged on both sides of the first helical gear 21. The first thrust bearing 31a is fixed to the outer wall 23 of the gear case 20 and supports the rotation of the first helical gear 21 on the outer side of the first helical gear 21 in the vehicle width direction. The thrust load generated in the first helical gear 21 during normal rotation is firmly received by the outer wall 23 via the first thrust bearing 31a. A pair of second thrust bearings 32a, 32b are arranged on both sides of the second helical gear 22. The second thrust bearing 32b is fixed to the inner wall 24 of the gear case 20 and supports the rotation of the second helical gear 22 on the inner side (center side) of the second helical gear 22 in the vehicle width direction. The thrust load generated in the second helical gear 22 during normal rotation is firmly received by the inner wall 24 via the second thrust bearing 32b.

[0033] The technology described in the embodiments may be expressed as follows: This specification discloses an automobile 90 equipped with an in-wheel motor drive device 2 (2a). The automobile 90 is equipped with the in-wheel motor drive device 2 (2a) described in the embodiments.

[0034] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0035] 2, 2a: In-wheel motor drive device 10: Motor 11: Stator 12: Rotor 13: Motor shaft 14, 14a: Motor case 15: Ball bearing 16: Outer wall 17: Rib 18: Peripheral wall 20: Gear case 21: First helical gear 22: Second helical gear 23: Outer wall 24: Inner wall 25: First opening 26: Second opening 30: Axle 31a, 31b: First thrust bearing 32a, 32b: Second thrust bearing 33: Third thrust bearing 90: Automobile 91: Wheel 92: Tire

Claims

1. An in-wheel motor drive device mounted on a vehicle, a motor case that houses a motor; an axle that is parallel to the motor main shaft and has a wheel fixed to an outer end in a vehicle width direction of the automobile; a first helical gear fixed to the motor main shaft; a second helical gear fixed to the axle and engaged with the first helical gear; a gear case in contact with the motor case, housing the first helical gear and the second helical gear, the gear case having a first opening in an inner wall facing the motor case through which the motor main shaft passes, and a second opening in an outer wall on the outer side in the vehicle width direction through which the axle passes; a first thrust bearing attached to the outer wall and rotatably supporting the first helical gear; a second thrust bearing attached to the inner wall and rotatably supporting the second helical gear; a rib provided on a rear surface of an outer wall of the motor case in the vehicle width direction; It is equipped with the directions of the helical teeth of the first helical gear and the second helical gear are set so that, when the motor main shaft rotates in a direction in which the automobile moves forward, a thrust load directed outward in the vehicle width direction is applied to the first helical gear, and a thrust load directed toward the center in the vehicle width direction is applied to the second helical gear; When viewed from the axial direction of the axle, the rib overlaps with the axle. In-wheel motor drive unit.

2. An in-wheel motor drive device mounted on an automobile, a motor case that houses a motor; an axle that is parallel to the motor main shaft and has a wheel fixed to an outer end in a vehicle width direction of the automobile; a first helical gear fixed to the motor main shaft; a second helical gear fixed to the axle and engaged with the first helical gear; a gear case in contact with the motor case, housing the first helical gear and the second helical gear, the gear case having a first opening in an inner wall facing the motor case through which the motor main shaft passes, and a second opening in an outer wall on the outer side in the vehicle width direction through which the axle passes; a first thrust bearing attached to the outer wall and rotatably supporting the first helical gear; a second thrust bearing attached to the inner wall and rotatably supporting the second helical gear; It is equipped with the directions of the helical teeth of the first helical gear and the second helical gear are set so that, when the motor main shaft rotates in a direction in which the automobile moves forward, a thrust load directed outward in the vehicle width direction is applied to the first helical gear, and a thrust load directed toward the center in the vehicle width direction is applied to the second helical gear; The motor case wall is a peripheral wall parallel to the motor main shaft, and is oriented in the axial direction of the axle. When viewed from the outside, it overlaps with the axle. In-wheel motor drive unit.

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