CN111565958A

CN111565958A - In-wheel motor driving device

Info

Publication number: CN111565958A
Application number: CN201980008085.9A
Authority: CN
Inventors: 田村四郎; 太向真也; 杉浦早织
Original assignee: NTN Corp
Current assignee: NTN Corp
Priority date: 2018-01-16
Filing date: 2019-01-09
Publication date: 2020-08-21
Also published as: JP2019123496A

Abstract

A speed reduction unit of an in-wheel motor drive device is provided with an output shaft (38) coupled to a moving coil (12) of a hub bearing unit (11), an output gear (37) as a helical gear coupled coaxially with the output shaft, and a first bearing (38b) and a second bearing (38a) that rotatably support the output shaft, wherein the rigidity of the second bearing is higher than that of the first bearing. The in-wheel motor drive device is characterized in that when the direction of an axial load (Fa) generated at the meshing part of the output gear (37) during forward rotation drive is one side of the axial direction of the output shaft (38), a second bearing (38a) is arranged at one side of the output gear (37) in the axial direction, and a first bearing (38b) is arranged at the other side of the output gear in the axial direction.

Description

In-wheel motor driving device

Technical Field

The present invention relates to an in-wheel motor drive device including a reduction gear unit having a plurality of gear wheels, and more particularly, to an in-wheel motor drive device in which a final gear (output gear) of the reduction gear unit is a helical gear.

Background

The in-wheel motor drive device disposed inside a wheel includes a motor unit that drives the wheel, a hub bearing unit to which the wheel is attached, and a speed reduction unit that reduces the speed of rotation of the motor unit and then transmits the reduced rotation to the hub bearing unit. As the speed reduction mechanism in the speed reduction unit, a parallel shaft gear speed reduction mechanism having a plurality of gears has been conventionally employed.

Japanese patent laid-open publication No. 2017-165392 (patent document 1) discloses the following structure: the reduction unit of the in-wheel motor drive device includes an input shaft coupled to a motor rotation shaft of the motor unit, an input gear coupled to the input shaft, an output shaft coupled to a moving coil of the hub bearing unit, an output gear (final gear) coupled to the output shaft, an intermediate shaft extending parallel to the input shaft and the output shaft, and an intermediate gear coupled to the intermediate shaft, and both ends of the output shaft are rotatably supported by a first bearing and a second bearing, respectively. Patent document 1 also discloses that the gear of the reduction unit is a helical gear to improve the tooth contact.

[ Prior Art document ]

[ patent document ]

[ patent document 1 ] Japanese patent laid-open publication No. 2017-165392

Disclosure of Invention

[ SUMMARY OF THE INVENTION ]

[ problem to be solved by the invention ]

According to the support structure for the output shaft disclosed in patent document 1, since the output shaft can be stably supported by the first bearing and the second bearing, even if an external force is applied from the wheel to the moving coil of the hub bearing portion, the displacement of the output shaft can be suppressed, and the uneven wear of the gear of the speed reducer portion can be prevented. In addition, in patent document 1, since a helical gear is applied as a gear of the reduction part, high quietness can be expected.

However, helical gears have a characteristic that an axial load (axial force) is generated in the meshing portion in accordance with the torsional direction of the tooth direction. Therefore, if only the output shaft is rotatably supported by the two bearings, the output shaft may be inclined due to the influence of the axial load acting on the output gear coupled to the output shaft. In such a case, the relative inclination between the output shaft and the intermediate shaft increases, and thus vibration generated in the meshing portion of the output gear increases, and noise may be generated in the vehicle interior due to solid propagation of the vibration.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an in-wheel motor drive device capable of suppressing inclination of an output shaft due to an influence of an axial load generated in a gear meshing portion when a helical gear is applied to a final gear of a speed reduction portion.

[ MEANS FOR solving PROBLEMS ] A method for solving the problems

An in-wheel motor drive device according to an aspect of the present invention includes: a hub bearing unit having a moving coil to which a wheel is attached; and a deceleration section. The speed reducer includes an output shaft coupled to a moving coil of the hub bearing portion, an output gear as a helical gear coupled coaxially with the output shaft, a first bearing rotatably supporting the output shaft, and a second bearing rotatably supporting the output shaft and having a higher rigidity than the first bearing. In the in-wheel motor drive device, when the direction of the axial load generated in the meshing portion of the output gear during normal rotation drive is one side in the axial direction of the output shaft, the second bearing is disposed at one side in the axial direction with respect to the output gear, and the first bearing is disposed at the other side in the axial direction with respect to the output gear. In this case, the tooth tips of the output gear are inclined such that the other side in the axial direction becomes the vehicle front side than the one side when viewed from above.

Preferably, the second bearing has a greater pitch circle than the first bearing.

In addition, the diameter of the rolling elements of the second bearing is preferably smaller than the diameter of the rolling elements of the first bearing. This can further improve the rigidity of the second bearing.

Preferably, the in-wheel motor drive device further includes a housing accommodating the speed reducer, and the first bearing and the second bearing are disposed between an outer diameter surface of the output shaft and a cylindrical surface formed in the housing.

Preferably, the moving coil of the hub bearing portion is an inner ring.

The hub bearing unit includes a stationary ring disposed coaxially with the moving ring and a plurality of rolling elements disposed in an annular gap between the moving ring and the stationary ring. In this case, the pitch circle of the second bearing may be larger than the pitch circle of the rolling element of the hub bearing portion, and the pitch circle of the first bearing may be equal to or smaller than the pitch circle of the rolling element of the hub bearing portion.

Preferably, the speed reducer unit includes an input shaft coupled to the motor rotation shaft, an input gear provided on the input shaft, a first intermediate gear meshed with the input gear, a second intermediate gear meshed with the output gear, an intermediate shaft integrally provided with the first intermediate gear and the second intermediate gear, a first intermediate bearing positioned on one side of the first intermediate gear in the axial direction and rotatably supporting the intermediate shaft, and a second intermediate bearing positioned on the other side of the second intermediate gear in the axial direction and rotatably supporting the intermediate shaft. In this case, it is further preferable that the pitch circle of the second intermediate bearing is larger than the pitch circle of the first intermediate bearing.

Preferably, one side in the axial direction is the outside in the vehicle width direction, and the other side in the axial direction is the inside in the vehicle width direction.

[ Effect of the invention ]

According to the present invention, the second bearing having relatively high rigidity is disposed in the direction in which the axial load acts on the meshing portion of the output gear during the normal rotation driving. This can suppress the inclination of the output shaft during normal rotation driving with a high frequency of use. As a result, vibration at the meshing portion of the output gear can be suppressed in most cases when the vehicle is driven, and therefore noise can be prevented or reduced.

Drawings

Fig. 1 is a longitudinal sectional view of an in-wheel motor drive device according to an embodiment of the present invention, which is shown in an expanded state and cut along a predetermined plane.

Fig. 2 is a transverse cross-sectional view schematically showing the internal structure of the reduction part of the in-wheel motor drive device according to the embodiment of the present invention.

Fig. 3 is a perspective view showing a state in which the output gear in the embodiment of the present invention is viewed from obliquely above.

Fig. 4 is a perspective view schematically showing a meshing state of the output gear and the intermediate gear in the embodiment of the present invention.

Fig. 5 is a view showing the rotation directions of the output gear and the intermediate gear in the normal rotation driving and the reverse rotation driving, respectively, in the embodiment of the present invention.

Fig. 6 (a) is a diagram conceptually showing an axial load generated in the output gear during the normal rotation driving, and fig. 6 (B) is a diagram conceptually showing radial loads generated in the two rolling bearings during the normal rotation driving.

Fig. 7 (a) is a view conceptually showing an axial load generated in the output gear at the time of the reverse rotation driving, and fig. 7 (B) is a view conceptually showing radial loads generated in the two rolling bearings at the time of the reverse rotation driving.

Fig. 8 is a diagram showing a detailed configuration example of the speed reducer section according to the embodiment of the present invention, and is a longitudinal sectional view in which the in-wheel motor drive device is shown in an expanded state by being cut along a predetermined plane.

Fig. 9 (a) and (B) are exploded perspective views of the input shaft unit of the speed reducer section shown in fig. 8.

Fig. 10 (a) and (B) are exploded perspective views of the intermediate shaft unit of the reduction unit shown in fig. 8.

Fig. 11 (a) and (B) are exploded perspective views of the output shaft unit of the reduction unit shown in fig. 8.

Fig. 12 is a transverse sectional view showing an internal structure of the speed reducer section shown in fig. 8.

Detailed Description

Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and the description thereof will be omitted.

< example of basic configuration >

First, a basic configuration example of an in-wheel motor drive device 1 according to an embodiment of the present invention will be described with reference to fig. 1 and 2. In-wheel motor drive device 1 is mounted on a passenger vehicle such as an electric vehicle or a hybrid vehicle.

Fig. 1 is a longitudinal sectional view of an in-wheel motor drive device 1 according to an embodiment of the present invention, which is shown in an expanded state and cut along a predetermined plane. Fig. 2 is a transverse cross-sectional view showing an internal structure of the speed reducer 31 of the in-wheel motor drive device 1, and schematically shows a state viewed from the outside in the vehicle width direction. The predetermined plane shown in fig. 1 is an expansion plane connecting a plane including the axis M and the axis N shown in fig. 2 and a plane including the axis N and the axis O in this order. In fig. 1, the left side of the drawing indicates the outside (outside) in the vehicle width direction, and the right side of the drawing indicates the inside (inside) in the vehicle width direction. In fig. 2, the gears inside the reduction unit 31 are indicated by tip circles, and the teeth are not shown.

The in-wheel motor drive device 1 includes a hub bearing portion 11 provided at the center of a wheel W, a motor portion 21 that drives the wheel, and a speed reduction portion 31 that reduces the speed of rotation of the motor portion 21 and then transmits the reduced speed to the hub bearing portion 11.

The motor unit 21 and the speed reducer unit 31 are disposed offset from the axis O of the hub bearing unit 11. The axis O extends in the vehicle width direction and coincides with the axle. In the present embodiment, one side in the direction of the axis O is an outer side, and the other side in the direction of the axis O is an inner side.

Regarding the position in the axis O direction, the hub bearing portion 11 is disposed on one side in the axis direction of the hub motor driving device 1, the motor portion 21 is disposed on the other side in the axis direction of the hub motor driving device 1, the speed reduction portion 31 is disposed on one side in the axis direction than the motor portion 21, and the position of the speed reduction portion 31 in the axis direction overlaps with the position of the hub bearing portion 11 in the axis direction.

The in-wheel motor drive device 1 is a vehicle motor drive device that drives a wheel of an electric vehicle. The in-wheel motor drive device 1 is coupled to a vehicle body, not shown. The in-wheel motor driving device 1 can drive the electric vehicle at a speed of 0-180 km/h.

The hub bearing portion 11 is a rotating inner ring/fixed outer ring, and includes an inner ring 12 serving as a moving ring (hub ring) coupled to the wheel W, an outer ring 13 serving as a stationary ring coaxially disposed on the outer diameter side of the inner ring 12, and a plurality of rolling elements 14 disposed in an annular space between the inner ring 12 and the outer ring 13. The rotation center of the inner race 12 coincides with an axis O passing through the center of the hub bearing portion 11.

The outer race 13 penetrates the front surface portion 39f of the main body case 39 and is fixedly coupled to the front surface portion 39 f. The front portion 39f is a case wall portion of the main body case 39 that covers one end of the speed reducer 31 in the axis O direction. For example, a plurality of outer ring protruding portions protruding in the outer diameter direction are provided upright on the outer peripheral surface of the outer ring 13 at circumferentially different positions, and bolts are inserted through holes provided in the outer ring protruding portions from one side in the axis O direction. The shaft portion of each bolt is screwed into a female screw hole bored in the front surface portion 39f of the main body case 39.

The bracket member 61 is coupled and fixed to the outer ring 13. On the outer peripheral surface of the outer ring 13, a plurality of outer ring projecting portions 13g projecting in the outer diameter direction are provided at circumferentially different positions. The bracket member 61 is positioned on the other side in the axis O direction of the outer ring protrusion 13g, and the bolt 62 is inserted from one side in the axis O direction through the through hole of the outer ring protrusion 13g and the female screw hole of the bracket member 61. The bracket member 61 is fixed by a bolt 63 passing through the main body case 39 from the other side in the direction of the axis O.

The inner ring 12 is a cylindrical body longer than the outer ring 13, and passes through a center hole of the outer ring 13. A coupling portion 12f is formed at one end portion in the axis O direction of the inner ring 12 protruding outward (outside) from the outer ring 13. The coupling portion 12f is a flange and constitutes a coupling portion for coaxially coupling the brake disc BD and the wheel. The inner race 12 is coupled to the wheel W via a coupling portion 12f and rotates integrally with the wheel.

Double rows of rolling elements 14 are disposed in an annular space between the inner ring 12 and the outer ring 13. The outer peripheral surface of the center portion in the axis O direction of the inner ring 12 constitutes an inner raceway surface of the plurality of rolling elements 14 arranged in the first row. The inner raceway ring 12r is fitted to the outer periphery of the other end portion of the inner ring 12 in the axis O direction. The outer peripheral surface of the inner raceway ring 12r forms an inner raceway surface of the plurality of rolling elements 14 arranged in the second row. The inner circumferential surface of one end portion of the outer ring 13 in the axis O direction constitutes an outer raceway surface of the rolling elements 14 in the first row. The inner circumferential surface of the other end portion of the outer ring 13 in the axis O direction constitutes an outer raceway surface of the rolling elements 14 in the second row. A seal 16 is interposed in an annular space between the inner ring 12 and the outer ring 13. The seal 16 seals both ends of the annular space, and prevents the entry of dust and foreign matter. The output shaft 38 of the speed reducer 31 is inserted into the center hole at the other end of the inner race 12 in the axis O direction, and spline-fitted or serration-fitted.

The motor unit 21 includes a motor rotating shaft 22, a rotor 23, and a stator 24, and the motor rotating shaft 22, the rotor 23, and the stator 24 are sequentially arranged from the axis M of the motor unit 21 to the outer diameter side. The motor unit 21 is a radial gap motor of an inner rotor or an outer stator type, but may be of another type. For example, although not shown, the motor unit 21 may be an axial gap motor.

The motor unit 21 is housed in the motor case 29. The motor housing 29 surrounds the outer periphery of the stator 24. One end of the motor case 29 in the direction of the axis M is joined to the back surface portion 39b of the main body case 39. The other end of the motor case 29 in the axis M direction is sealed by a plate-shaped motor case cover 29 v. The rear surface portion 39b is a case wall portion of the main body case 39 that covers the other end of the speed reducer 31 in the direction of the axis M (the direction of the axis O).

The main body case 39, the motor case 29, and the motor case cover (rear cover) 29v constitute the case 10 that is the outer shell of the in-wheel motor drive device 1.

The stator 24 includes a cylindrical stator core 25 and a coil 26 wound around the stator core 25. The stator core 25 is formed by laminating annular steel plates in the direction of the axis M.

Both ends of the motor rotary shaft 22 are rotatably supported by the rear surface portion 39b of the main body case 39 and the motor case cover 29v via rolling

bearings

27 and 28. An axis M, which is a rotation center of the motor rotary shaft 22 and the rotor 23, extends in parallel with the axis O of the hub bearing portion 11. That is, the motor unit 21 is offset from the axis O of the hub bearing unit 11. For example, as shown in fig. 2, the axis M of the motor unit 21 is offset from the axis O in the vehicle front-rear direction, and specifically, is disposed in the vehicle front direction with respect to the axis O.

The speed reducer 31 includes: an input shaft 32 coaxially coupled to the motor rotating shaft 22 of the motor unit 21; an input gear 33 coaxially provided on an outer peripheral surface of the input shaft 32; a plurality of

intermediate gears

34, 36; an intermediate shaft 35 coupled to the centers of these

intermediate gears

34, 36; an output shaft 38 coaxially coupled to the inner ring 12 of the hub bearing portion 11; and an output gear 37 coaxially provided on the outer peripheral surface of the output shaft 38. The plurality of gears and the rotating shaft of the speed reducer 31 are housed in the main body case 39. The main body case 39 constitutes an outer contour of the speed reducing portion 31, and is therefore also referred to as a speed reducing portion case.

The input gear 33 is a helical gear with external teeth. The input shaft 32 has a hollow structure, and one end portion in the axial direction of the motor rotary shaft 22 is inserted into the hollow portion 32h of the input shaft 32. Thereby, the motor rotary shaft 22 and the input shaft 32 are spline-fitted (or serration-fitted) so as not to be relatively rotatable. The input shaft 32 is rotatably supported by a front portion 39f and a rear portion 39b of the main body case 39 via rolling

bearings

32a and 32b on both end sides of the input gear 33.

An axis N which is a rotation center of the intermediate shaft 35 of the speed reducer 31 extends parallel to the axis O. Both ends of the intermediate shaft 35 are rotatably supported by a front portion 39f and a rear portion 39b of the main body case 39 via

bearings

35a and 35 b. A first intermediate gear 34 and a second intermediate gear 36 are provided in the center of the intermediate shaft 35 coaxially with the axis N of the intermediate shaft 35. The first intermediate gear 34 and the second intermediate gear 36 are external-toothed helical gears, and the diameter of the first intermediate gear 34 is larger than that of the second intermediate gear 36. The first intermediate gear 34 having a large diameter is disposed on the other side in the axis N direction than the second intermediate gear 36, and meshes with the input gear 33 having a small diameter. The second intermediate gear 36 having a small diameter is disposed on one side of the first intermediate gear 34 in the axis N direction, and meshes with the output gear 37 having a large diameter.

As shown in fig. 1, the axis N of the intermediate shaft 35 is disposed above the axes O and M. The axis N of the intermediate shaft 35 is disposed at the vehicle front side of the axis O and the vehicle rear side of the axis M. The speed reducer 31 is a three-axis parallel-shaft gear reducer having axes O, N, M arranged at intervals in the vehicle longitudinal direction and extending parallel to each other.

The output gear 37 is an externally toothed helical gear, and is coaxially provided in the center of the output shaft 38. The output shaft 38 extends along an axis O. One end portion of the output shaft 38 in the axis O direction is inserted into the center hole of the inner race 12 and fitted so as not to be relatively rotatable. The fitting is spline fitting or serration fitting. The central portion (one end side) of the output shaft 38 in the axis O direction is rotatably supported by a front surface portion 39f of the main body case 39 via a rolling bearing 38 a. The other end portion (the other end side) of the output shaft 38 in the axis O direction is rotatably supported by a rear surface portion 39b of the main body case 39 via a rolling bearing 38 b.

The rolling bearing 38a is located on the outer side of the output gear 37, and the rolling bearing 38b is located on the inner side of the output gear 37. The rolling

bearings

38a and 38b are disposed between the outer diameter surface of the output shaft 38 and the cylindrical surface formed in the main body case 39. Specifically, the outer ring of the rolling bearing 38a is fixed to the cylindrical surface formed at the front portion 39f of the main body case 39, and the outer ring of the rolling bearing 38b is fixed to the cylindrical surface formed at the rear portion 39b of the main body case 39.

The reduction unit 31 reduces the rotation of the input shaft 32 and transmits the rotation to the output shaft 38 by the engagement of the small-diameter drive gear and the large-diameter driven gear, that is, the engagement of the input gear 33 and the first intermediate gear 34 and the engagement of the second intermediate gear 36 and the output gear 37. The rotation elements of the speed reduction unit 31 from the input shaft 32 to the output shaft 38 constitute a drive transmission path for transmitting the rotation of the motor unit 21 to the inner race 12. The input shaft 32, the intermediate shaft 35, and the output shaft 38 are double-supported by the rolling bearing described above. The rolling

bearings

32a, 35a, 38a, 32b, 35b, 38b are radial bearings.

The main body case 39 includes a cylindrical portion, and a plate-like front portion 39f and a back portion 39b that cover both ends of the cylindrical portion. The cylindrical portion covers the internal components of the speed reducer portion 31 so as to surround the axes O, N, M extending parallel to each other. The plate-like front portion 39f covers the internal components of the speed reducer section 31 from one side in the axial direction. The plate-like back surface portion 39b covers the internal components of the speed reducer section 31 from the other side in the axial direction. As shown in fig. 2, an oil tank 40 for storing lubricating oil is provided at a lower portion of the main body case 39.

The rear surface portion 39b of the main body case 39 is also a partition wall that is joined to the motor case 29 and separates an internal space of the speed reducer unit 31 and an internal space of the motor unit 21. The motor case 29 is supported by the main body case 39 and protrudes from the main body case 39 to the other side in the axial direction.

When electric power is supplied from the outside of the in-wheel motor drive device 1 to the stator 24 of the motor unit 21, the rotor 23 of the motor unit 21 rotates and the rotation is output from the motor rotation shaft 22 to the speed reduction unit 31. The speed reduction unit 31 reduces the speed of the rotation input from the motor unit 21 to the input shaft 32 and outputs the rotation from the output shaft 38 to the hub bearing unit 11. The inner ring 12 of the hub bearing portion 11 rotates at the same rotational speed as the output shaft 38, and drives a wheel, not shown, attached and fixed to the inner ring 12.

< Structure for supporting rotation of output shaft >

Next, a rotation support structure of the output shaft 38 of the in-wheel motor drive device 1 according to the present embodiment will be described.

As described above, the output shaft 38 is doubly supported by the two rolling

bearings

38a, 38b having different positions in the axial direction. Thus, the output shaft 38 is stably supported for rotation, and therefore even if the inner ring 12 of the hub bearing portion 11 coupled to the output shaft 38 is slightly displaced (deformed) by an external force accompanying a turning load, the displacement (inclination) of the output shaft 38 can be suppressed as much as possible.

Here, in the present embodiment, as shown in fig. 3 and 4, a helical gear may be applied as the output gear 37 coaxially coupled to the output shaft 38. The helical gear is a cylindrical gear having a helical tooth direction. Fig. 3 shows a state in which the output gear 37 is viewed obliquely from above, and fig. 4 schematically shows a state in which the output gear 37 meshes with the intermediate gear 36. In this way, when the output gear 37 and the intermediate gear 36 are helical gears, the tooth contact of the gear meshing portion is good, and therefore, high quietness can be (ideally) obtained.

On the other hand, when the vehicle is running, that is, when the wheels are driven, the helical gear generates a unique axial load at the meshing portion of the output gear 37 (the meshing portion with the intermediate gear 36). Therefore, due to the influence of the axial load acting on the meshing portion of the output gear 37, one of the rolling

bearings

38a and 38b supporting the output shaft 38 receives a higher load than the other. Therefore, if only the output shaft 38 is doubly supported by the two rolling

bearings

38a and 38b, the load may be biased to one bearing, and the output shaft 38 may be inclined.

This will be described in detail with reference to fig. 5 to 7. Fig. 5 is a diagram showing the rotation directions of the output gear 37 and the intermediate gear 36 during the normal rotation driving and the reverse rotation driving, respectively. Fig. 6 (a) is a diagram conceptually showing an axial load generated in the output gear 37 during the normal rotation driving, and fig. 6 (B) is a diagram conceptually showing radial loads generated in the two rolling bearings 38a and 38B during the normal rotation driving. Fig. 7 (a) is a diagram conceptually showing an axial load generated in the output gear 37 during the reverse rotation driving, and fig. 7 (B) is a diagram conceptually showing a radial load generated in each of the two rolling bearings 38a and 38B during the reverse rotation driving. Fig. 5 shows a state in which the

gears

36 and 37 are viewed from the outside, and fig. 6 (a) and 7 (a) show a state in which the

gears

36 and 37 shown in fig. 5 are viewed from above. Fig. 6 (B) and 7 (B) show a part of the longitudinal sectional view of fig. 1 in an enlarged manner.

The direction of the twist in the tooth direction of the output gear 37 in the embodiment is the so-called right twist direction, and as shown in fig. 3, the tooth tips 37a of the output gear 37 are inclined so that the inner side (the other side in the axial direction) is located forward of the vehicle with respect to the outer side (the one side in the axial direction). As shown in fig. 6 (a) and (B), the load generated at the meshing portion of the output gear 37 includes a radial component fr (g) and an axial component Fa, and the load is shared by the outer rolling bearing 38a and the inner rolling bearing 38B.

The gear radial component fr (g) generated in the gear meshing portion functions as a bearing radial component fr (b) in the same direction as the gear radial component fr (g) in the rolling

bearings

38a and 38 b. The radial components fr (g) and fr (b) represent radial forces directed radially inward. This bearing radial component fr (b) is referred to as a first bearing radial component fr (b).

On the other hand, the gear axial component Fa generated in the gear meshing portion acts as mutually opposite bearing radial components Far in the rolling

bearings

38a and 38 b. This is because the axial center (axis O) of the output gear 37 and the meshing portion are offset in the radial direction, and therefore, a moment about the axis O is generated, and the two rolling

bearings

38a and 38b receive the moment as a bearing radial component. This bearing radial component Far is referred to as a second bearing radial component Far.

Specifically, the second bearing radial component Far is oriented in the opposite direction in the outer rolling bearing 38a and the inner rolling bearing 38 b. Therefore, in one bearing, the first bearing radial component fr (b) and the second bearing radial component Far cancel each other, but in the other bearing, the first bearing radial component fr (b) and the second bearing radial component Far add each other. Therefore, when the output gear 37 is a helical gear, a large load acts on only one of the two rolling

bearings

38a and 38b that rotatably support the output shaft 38.

More specifically, as shown in fig. 6 (a), the axial load Fa generated at the meshing portion of the output gear 37 during normal rotation driving is directed outward. In fig. 6 (a), the direction of the tangential force generated at the meshing portion of the output gear 37 during the normal rotation driving is indicated by a broken line.

In this case, as shown in fig. 6 (B), the second bearing radial load Far acting on the outer rolling bearing 38a is directed radially inward, and the second bearing radial load Far acting on the inner rolling bearing 38B is directed radially outward. Therefore, during the normal rotation driving, the outer rolling bearing 38a receives a higher radial load than the inner rolling bearing 38 b.

On the other hand, as shown in fig. 7 (a), the axial load Fa generated in the meshing portion of the output gear 37 during reverse rotation is directed inward. In fig. 7 (a), the direction of the tangential force generated at the meshing portion of the output gear 37 during the reverse rotation is indicated by a broken line.

In this case, as shown in fig. 7 (B), the second bearing radial load Far acting on the outer rolling bearing 38a is directed radially outward, and the second bearing radial load Far acting on the inner rolling bearing 38B is directed radially inward. Therefore, during the reverse rotation driving, the inner rolling bearing 38b receives a higher radial load than the outer rolling bearing 38 a.

In this way, when the output gear 37 is a helical gear, the magnitude relationship of the radial loads acting on the two rolling

bearings

38a and 38b that rotatably support the output shaft 38 is reversed between the normal rotation driving and the reverse rotation driving.

Here, in the present embodiment, the rigidity of the outer rolling bearing 38a that receives a relatively high load during the normal rotation driving is set to be higher than the rigidity of the inner rolling bearing 38 b. In the case where the axial load Fa toward the outside is applied to the meshing portion of the output gear 37 during the normal rotation driving, the magnitude of the bearing load and the level of rigidity of the rolling

bearings

38a and 38b are related as follows.

[ TABLE 1 ]

In the present embodiment, the Pitch circle (Pitch circle) of the Outer (OB) side rolling bearing 38a is made larger than the Pitch circle of the Inner (IB) side rolling bearing 38b, so that the rigidity of the outer side rolling bearing 38a is made higher than the rigidity of the inner side rolling bearing 38 b. That is, as shown in fig. 1, the PCD (pitch circle diameter D1) of the outer rolling bearing 38a is larger than the PCD (pitch circle diameter D2) of the inner rolling bearing 38 b. Accordingly, the number of rolling elements of the outer rolling bearing 38a can be made larger than the number of rolling elements of the inner rolling bearing 38b, and the rolling elements of the outer rolling bearing 38a can be made larger than the rolling elements of the inner rolling bearing 38b, so that the rigidity of the outer rolling bearing 38a is higher than the rigidity of the inner rolling bearing 38 b.

In order to vary the pitch circles of the two rolling

bearings

38a and 38b in this manner, for example, as shown in fig. 1, the rolling bearing 38b on the inner side may be provided in a stepped portion 38d provided at the inner side end of the output shaft 38. Specifically, the inner race of the rolling bearing 38b is fitted into the stepped portion 38d of the output shaft 38. Accordingly, the rolling bearing 38b on the motor unit 21 side (inner side) can be made relatively small, and the radial dimension of the in-wheel motor drive device 1 can be suppressed to be small without increasing the pitch circle size of the rolling bearing 38a on the outer side more than necessary.

In the embodiment shown in fig. 1, the pitch circle of the outer rolling bearing 38a is larger than the pitch circle of the rolling elements 14 of the hub bearing unit 11, and the pitch circle of the inner rolling bearing 38b is equal to or smaller than the pitch circle of the rolling elements 14 of the hub bearing unit 11.

The outer rolling bearing 38a may be disposed between an outer peripheral surface of an annular projection 37b provided upright on one end surface of the output gear 37 in the axis O direction and a cylindrical surface formed on a front surface portion 39f of the main body case 39. The cylindrical surface of the front portion 39f is formed by the inner peripheral surface of an annular projection 39i provided upright on the inner wall surface of the front portion 39 f. In this case, the other end portions in the axis O direction of the inner ring 12 and the outer ring 13 may be housed in the space on the inner diameter side of the annular convex portion 37b of the output gear 37.

As described above, the rolling bearing 38a may be disposed so as to be able to rotatably support the output shaft 38, and may not be configured to directly support the outer peripheral surface of the output shaft 38. As shown in fig. 1 and the like, it is preferable that the position of (the rolling element of) the rolling bearing 38a in the axis O direction is set at a position not overlapping with the position of the meshing portion of the output gear 37 and the intermediate gear 36 (i.e., the tooth width of the output gear 37).

By adopting the above arrangement, the PCD (pitch diameter D1) of the outer rolling bearing 38a can be 1.5 times or more, and more preferably 2 times or more, the PCD (pitch diameter D2) of the inner rolling bearing 38 b.

As described above, by making the outer rolling bearing 38a more rigid than the inner rolling bearing 38b, the inclination of the output shaft 38 during the normal rotation driving can be suppressed. In the forward rotation drive, the frequency of use is overwhelmingly higher than that of the reverse rotation drive, and the rotation is performed at a high speed. Therefore, by suppressing the inclination of the output shaft 38 during the normal rotation driving, it is possible to prevent or suppress the generation of noise associated with the vibration of the gear meshing portion during the vehicle running.

< detailed configuration example of deceleration section >

Fig. 8 to 12 show a detailed configuration example of the speed reduction unit including the three-axis parallel shaft type gear reducer as described above. Fig. 8 is a view corresponding to fig. 1, and is a longitudinal sectional view showing the in-wheel motor drive device 1A according to the embodiment of the present invention, cut along a predetermined plane and expanded. Fig. 9 (a) and (B) are exploded perspective views of the input shaft unit of the speed reducer 31A. Fig. 10 (a) and (B) are exploded perspective views of the intermediate shaft unit of the speed reducer 31A. Fig. 11 (a) and (B) are exploded perspective views of the output shaft unit of the speed reducer 31A. Fig. 12 is a transverse cross-sectional view corresponding to fig. 2, showing an internal structure of the speed reducer 31A of the in-wheel motor drive device 1A, and schematically shows a state viewed from the outside in the vehicle width direction. Fig. 9 (a) to 11 (a) are perspective views of the respective shaft units viewed from the outside in the vehicle width direction, and fig. 9 (B) to 11 (B) are perspective views of the respective shaft units viewed from the inside in the vehicle width direction.

The basic configuration of the in-wheel motor drive device 1A shown in fig. 8 is the same as the in-wheel motor drive device 1 shown in fig. 1 and 2. The reduction unit 31A of the in-wheel motor drive device 1A also includes the input shaft 32, the intermediate shaft 35, the output shaft 38, the input gear 33 provided on the input shaft 32, the

intermediate gears

34, 36 provided on the intermediate shaft 35, the output gear 37 provided on the output shaft 38, and the rolling

bearings

32a, 35a, 38a, 32b, 35b, 38b that support these

shafts

32, 35, 38, as described above. In the following description, the direction along the axis M, N, O will be referred to as "axial direction".

Referring to fig. 8 and 9, the input shaft unit is composed of an input shaft 32, an input gear 33 provided integrally with the input shaft 32, and a pair of rolling

bearings

32a and 32b rotatably supporting the input shaft 32. The input gear 33 is formed integrally with the input shaft 32. The input gear 33 is provided at an axial center portion of the input shaft 32. The rolling

bearings

32a, 32b are fitted into the outer peripheral surfaces of the

axial end portions

71, 72 of the input shaft 32, respectively. The inner rings of the rolling

bearings

32a and 32b may be respectively in contact with one end surface and the other end surface of the input gear 33 in the axial direction.

The outer diameters of both

end portions

71, 72 of the input shaft 32 are equal to each other. In this case, the rolling

bearings

32a and 32b are preferably formed of bearings of the same specification. That is, PCD, inner diameter size, outer diameter size, diameter and number of rolling elements of the rolling

bearings

32a, 32b are preferably equal to each other. This enables the support structure of the input shaft 32 to be made common in terms of components, and thus can reduce manufacturing costs.

Referring to fig. 8 and 10, the intermediate shaft unit includes an intermediate shaft 35, two

intermediate gears

34 and 36 provided integrally with the intermediate shaft 35, and a pair of rolling

bearings

35a and 35b rotatably supporting the intermediate shaft 35. The large-diameter intermediate gear 34 is formed integrally with the intermediate shaft 35. On the other hand, the small-diameter intermediate gear 36 is separate from the intermediate shaft 35 and spline-fitted (press-fitted) to the intermediate shaft 35. Specifically, the intermediate shaft 35 includes a spline portion 83 having repeated concavities and convexities on an outer peripheral surface thereof, and spline grooves provided on an inner peripheral surface 85 of the intermediate gear 36 are fitted into the spline portion 83. Thereby, the intermediate gear 36 is integrally coupled to the intermediate shaft 35.

It should be noted that the intermediate shaft 35 may have a hollow structure. That is, the intermediate shaft 35 may have a hollow hole 86 penetrating in the axial direction. This can form the hollow hole 86 in the passage of the lubricating oil, thereby improving the lubricating performance of the speed reducer portion 31A.

The rolling

bearings

35a and 35b are fitted into the outer peripheral surfaces of the

axial end portions

81 and 82 of the intermediate shaft 35. The one end portion 81 of the intermediate shaft 35 is disposed adjacent to the spline portion 83. The axial position of the other end 82 of the intermediate shaft 35 may partially overlap with the axial position of the intermediate gear 38. That is, the rolling bearing 35b on the inner side may be disposed in an annular recess 87 provided on the other axial end surface of the large-diameter intermediate gear 34. This can shorten the axial dimension of the intermediate shaft 35.

The other end 82 of the intermediate shaft 35 has a larger outer diameter than the one end 81. Therefore, the PCD (pitch circle diameter D3) of the inner rolling bearing 35b is larger than the PCD (pitch circle diameter D4) of the outer rolling bearing 35 a. In the in-wheel motor drive device 1A, the bearing span of the gear shaft (the input shaft 32, the intermediate shaft 35, and the output shaft 38) is short due to the demand for downsizing of the axial dimension, and therefore the amount of increase in the inclination of the gear shaft with respect to the radial displacement is relatively large. During normal rotation driving, an axial load is generated toward the inside at the meshing portion of the rear-stage intermediate gear 36, and an axial load is generated toward the outside at the meshing portion of the front-stage intermediate gear 34. The torque increases further toward the rear section, and therefore the axial load toward the inside is relatively large at the intermediate shaft 35.

Therefore, as described above, the rolling bearing 35b on the inner side has a larger diameter than the rolling bearing 35a on the outer side, whereby the rigidity of the rolling bearing 35b can be ensured. Specifically, even when the rolling elements (steel balls) of the

bearings

35a and 35b have the same diameter, the number of the rolling elements 89b of the rolling bearing 35b can be increased more than the number of the rolling elements 89a of the rolling bearing 35 a. This can suppress the inclination of the intermediate shaft 35 during the normal rotation driving, and therefore the offset of the tooth surface contact is reduced. As a result, the vibration can be suppressed from occurring in the meshing portion between the intermediate gear 34 and the input gear 33 and the meshing portion between the intermediate gear 36 and the output gear 37.

In addition, the rolling elements 89b of the inner rolling bearing 35b have a smaller diameter than the rolling elements 89a of the outer rolling bearing 35a, so that the number of the rolling elements 89b of the rolling bearing 35b can be further increased. This can increase the rated load of the rolling bearing 35b, and therefore can improve the rigidity of the rolling bearing 35 b. Further, since the width dimension of the inner rolling bearing 35b can be made smaller than the width dimension of the outer rolling bearing 35a, the axial dimension of the intermediate shaft 35 can be shortened.

The intermediate gear 36 is located between the rolling bearing 35a and the large-diameter intermediate gear 34. As shown in fig. 8, the outer diameter dimension D5 of the inner ring 88 of the rolling bearing 35a is preferably larger than the (largest) outer diameter dimension D6 of the spline portion 83 of the intermediate shaft 35. Thus, the inner ring 88 of the rolling bearing 35a is in surface contact with one end surface in the axial direction of the intermediate gear 36, and therefore, the intermediate gear 36 can be prevented from falling off from the intermediate shaft 35 due to vibration or the like. In the reverse rotation driving, even when an axial load in the external direction is generated at the meshing portion of the idler gear 36, the inner ring 88 of the rolling bearing 35a functions as a retaining member for the idler gear 36.

The movement of the inner ring 88 of the rolling bearing 35a to one axial side is restricted by the annular elastic member 84 fitted into the groove 81a provided at the one end portion 81 of the intermediate gear 36.

Referring to fig. 8 and 11, the output shaft unit is composed of an output shaft 38, an output gear 37 provided integrally with the output shaft 38, and a pair of rolling

bearings

38a and 38b rotatably supporting the output shaft 38. The output gear 37 is formed integrally with the output shaft 38. The output gear 37 is provided at an axial center portion of the output shaft 38. A spline portion 93 for spline fitting with the inner ring 12 of the hub bearing portion 11 is provided on the outer peripheral surface of one end portion in the axial direction of the output shaft 38.

As described above, the outer rolling bearing 38a is fitted into the outer peripheral surface of the annular projection 37b provided upright on one axial end surface of the output gear 37. The annular projecting portion 37b is adjacent to the output gear 37 without overlapping in axial position and overlaps with the other axial end portion of the inner ring 12 of the hub bearing portion 11. The inner rolling bearing 38b is fitted into the outer peripheral surface of the other end portion 92 in the axial direction of the output shaft 38. The rolling bearing 35a on the outer side of the intermediate shaft 35 is disposed at substantially the same axial position as the rolling bearing 38 a. The rolling bearing 35b on the inner side of the intermediate shaft 35 may be located on the outer side (one axial side) than the rolling bearing 38 b.

The output shaft 38 has a protruding portion 94 protruding further toward the inside (the other axial side) than a fitting portion where the output shaft 38 and the inner rolling bearing 38b are fitted, and the oil pump 63 can be attached to the protruding portion 94. In this case, the outer diameter dimension (the diameter of the outer peripheral surface of the outer ring) D7 of the rolling bearing 38b on the inner side is preferably larger than the outer diameter dimension D8 of the oil pump 63.

Since the outer rolling bearing 38a is affected by the axial load during the normal rotation driving, as shown in fig. 1, the PCD (pitch circle diameter D1) of the outer rolling bearing 38a is larger than the PCD (pitch circle diameter D2) of the inner rolling bearing 38 b. It is preferable that the diameter of the rolling elements 99a of the outer rolling bearing 38a is smaller than that of the rolling elements 99b of the inner rolling bearing 38b, and the number of the rolling elements 99a of the rolling bearing 38a is further increased. This increases the rated load of the rolling bearing 38a, and therefore the rigidity of the rolling bearing 38a is further improved. In this case, since the width of the outer rolling bearing 38a can be made smaller than the width of the inner rolling bearing 38b, the axial dimension of the output shaft 38 can be shortened.

As described above, the decelerating section 31A may have the following features.

The outer rolling bearing 32a and the inner rolling bearing 32b of the input shaft 32 are formed by the same bearing.

The outer diameter of the inner ring 88 of the rolling bearing 35a on the outer side of the intermediate shaft 35 is larger than the outer diameter of the spline portion 83 of the intermediate gear 36 spline-fitted to the intermediate shaft 33.

(modification 1)

In the above embodiment, the teeth of the output gear 37 are twisted in the right direction, but the teeth of the output gear may be twisted in the left direction. That is, the outside (one side in the axial direction) of the tooth tips of the output gear is inclined to be the vehicle front side with respect to the inside (the other side in the axial direction). In this case, since the direction of the axial load generated in the meshing portion of the output gear during the normal rotation driving is the inner side, the inner side rolling bearing may be made to have higher rigidity than the outer side rolling bearing, contrary to the above-described embodiment. That is, in this case, the pitch circle of the rolling bearing on the inner side may be made larger than the pitch circle of the rolling bearing on the outer side.

In this way, when the direction of the axial load generated at the meshing portion of the output gear is set to "one side in the axial direction" during the normal rotation driving, a rolling bearing (second bearing) having relatively high rigidity may be disposed at one side in the axial direction of the output gear, and a rolling bearing (first bearing) having relatively low rigidity may be disposed at the other side in the axial direction of the output gear.

(modification 2)

In the above embodiment, the moving coil of the hub bearing portion 11 is an inner ring, but the moving coil may be an outer ring. That is, the above-described rotation support structure of the output shaft can be applied to a hub motor drive device including a hub bearing unit of a rotating outer ring/fixed inner ring type.

(modification 3)

In the above embodiment, the example in which the speed reduction unit 31 is a three-axis parallel shaft type gear reducer is shown, but the speed reduction unit may be another type of gear reducer such as a four-axis parallel shaft type gear reducer.

It should be noted that the embodiments disclosed herein are illustrative in all respects and not limited thereto. The scope of the present invention is defined by the claims, not by the above description, and includes all modifications equivalent in meaning and scope to the claims.

[ notation ] to show

1. 1A in-wheel motor drive device, 10 casing, 11 hub bearing portion, 12 inner ring, 13 outer ring, 14 rolling body, 21 motor portion, 22 motor rotation shaft, 23 rotor, 24 stator, 25 stator core, 26 coil, 27, 28, 32a, 32b, 35a, 35b, 38a, 38b rolling bearing, 29 motor casing, 29v motor casing cover, 31A speed reduction portion, 32 input shaft, 33 input gear, 34, 36 intermediate gear, 35 intermediate shaft, 37 output gear, 38 output shaft, 39 main body casing, M, N, O axis, W wheel.

Claims

1. An in-wheel motor drive device is characterized by comprising:

a hub bearing unit having a moving coil to which a wheel is attached; and

a speed reduction unit including an output shaft coupled to the moving coil of the hub bearing unit, an output gear as a helical gear coupled coaxially with the output shaft, a first bearing rotatably supporting the output shaft, and a second bearing rotatably supporting the output shaft and having a higher rigidity than the first bearing,

in the case where the direction of the axial load generated in the meshing portion of the output gear is toward one side in the axial direction of the output shaft during the normal rotation driving, the second bearing is disposed on one side in the axial direction of the output gear, and the first bearing is disposed on the other side in the axial direction of the output gear.

2. The in-wheel motor drive arrangement according to claim 1,

the pitch circle of the second bearing is larger than that of the first bearing.

3. The in-wheel motor drive arrangement according to claim 2,

the diameter of the rolling elements of the second bearing is smaller than the diameter of the rolling elements of the first bearing.

4. The in-wheel motor drive apparatus according to any one of claims 1 to 3,

the in-wheel motor drive device further includes a housing accommodating the speed reduction unit,

the first bearing and the second bearing are disposed between an outer diameter surface of the output shaft and a cylindrical surface formed in the housing.

5. The in-wheel motor drive apparatus according to any one of claims 1 to 4,

the moving coil of the hub bearing portion is an inner ring.

6. The in-wheel motor drive arrangement according to claim 5,

the hub bearing portion includes a stationary ring and a plurality of rolling elements, the stationary ring is disposed coaxially with the moving ring, the plurality of rolling elements are disposed in an annular gap between the moving ring and the stationary ring,

the pitch circle of the second bearing is larger than the pitch circle of the rolling element of the hub bearing portion, and the pitch circle of the first bearing is smaller than or equal to the pitch circle of the rolling element of the hub bearing portion.

7. The in-wheel motor drive apparatus according to any one of claims 1 to 6,

the deceleration section includes: an input shaft coupled to a motor rotation shaft, an input gear provided on the input shaft, a first intermediate gear meshed with the input gear, a second intermediate gear meshed with the output gear, an intermediate shaft provided integrally with the first intermediate gear and the second intermediate gear, a first intermediate bearing provided on one side of the first intermediate gear in an axial direction and rotatably supporting the intermediate shaft, and a second intermediate bearing provided on the other side of the second intermediate gear in the axial direction and rotatably supporting the intermediate shaft,

the pitch circle of the second intermediate bearing is greater than the pitch circle of the first intermediate bearing.

8. The in-wheel motor drive apparatus according to any one of claims 1 to 7,

one side of the axial direction is the outside of the vehicle width direction, and the other side of the axial direction is the inside of the vehicle width direction.