JP2019123496A - In-wheel motor driving device - Google Patents

Abstract

To suppress an inclination of an output shaft due to an influence of an axial load generated in a gear engagement part when applying a helical gear as a final gear (output gear) of a deceleration part.SOLUTION: A deceleration part of an in-wheel motor driving device includes an output shaft (38) joined to a rotary wheel (12) of a wheel hub bearing part (11), an output gear (37), a helical gear joined coaxially to the output shaft, and a first bearing (38b) and a second bearing (38a) which support the output shaft rotatably, where rigidity of the second bearing part is higher than rigidity of the first bearing. In the in-wheel motor driving device, when an axial load (Fa) generated in the engagement part of the output gear (37 ) is directed toward one side in a shaft line direction of the output shaft (38) during normal rotation drive, the second bearing (38a) is arranged at a position closer to the one side in the shaft line direction than the output gear (37) and the first bearing (38b) is arranged at a position closer to the other side in the shaft line direction than the output gear.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an in-wheel motor drive provided with a gear type reduction unit having a plurality of gears, and more particularly to an in-wheel motor drive using a final gear (output gear) of the reduction unit as a helical gear. .

  The in-wheel motor drive device disposed inside the wheel comprises a motor unit for driving the wheel, a wheel hub bearing unit to which the wheel is attached, and a speed reduction unit for decelerating the rotation of the motor unit and transmitting it to the wheel hub bearing unit Equipped with Conventionally, a parallel shaft gear reduction mechanism having a plurality of gears has been adopted as a reduction mechanism in the reduction portion.

  JP-A-2017-165392 (PTL 1) discloses an input shaft connected to the motor rotation shaft of the motor unit, an input gear connected to the input shaft, and a wheel hub bearing unit. An output shaft coupled to the rotating wheel, an output gear coupled to the output shaft (final gear), an intermediate shaft extending parallel to the input shaft and the output shaft, and an intermediate gear coupled to the intermediate shaft, both ends of the output shaft An arrangement rotatably supported by the bearing and the second bearing is disclosed. Further, Patent Document 1 also discloses that the tooth contact is improved by making the gear of the speed reduction unit a helical gear.

Unexamined-Japanese-Patent No. 2017-165392

  According to the support structure of the output shaft disclosed in Patent Document 1, the output shaft can be stably supported on both sides by the first bearing and the second bearing, so that the rotating wheel of the wheel hub bearing portion from the wheel wheel Even when an external force is applied, the effect of suppressing the displacement of the output shaft and preventing the partial wear of the gear of the speed reducing portion can be obtained. Moreover, in Patent Document 1, since a helical gear is applied as the gear of the speed reducing portion, high quietness is expected.

  However, the helical gear has a characteristic that an axial load (axial force) is generated at the meshing portion according to the twisting direction of the tooth line. Therefore, just because the output shaft is rotatably supported by the two bearings, the output shaft may be inclined due to the effect of an 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 is increased, so that the vibration generated at the meshing portion of the output gear is increased, and there is a concern that noise may be generated inside the vehicle by the solid propagation of the vibration. The

  The present invention has been made to solve the problems as described above, and an object thereof is to apply an axial load generated in a gear meshing portion when a helical gear is applied to the final gear of the reduction portion. It is providing the in-wheel motor drive which can control the inclination of the output shaft by influence.

  An in-wheel motor drive according to one aspect of the present invention includes a wheel hub bearing portion having a rotating wheel to which a wheel is attached, and a speed reduction portion. The speed reduction portion includes an output shaft coupled to the rotating wheel of the wheel hub bearing portion, an output gear which is a helical gear coupled coaxially with the output shaft, and a first bearing rotatably supporting the output shaft. And a second bearing rotatably supporting the output shaft and having higher rigidity than the first bearing. When the direction of the axial load generated at the meshing portion of the output gear during normal rotation drive is one side of the output shaft in the axial direction, the in-wheel motor drive is positioned at the one side in the axial direction relative to the output gear. A bearing is disposed, and the first bearing is disposed at a position on 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 is forward of the vehicle than the one side when viewed from above.

  Preferably, the pitch circle of the second bearing is larger than the pitch circle of the first bearing.

  It is also desirable that the diameter of the rolling element of the second bearing is smaller than the diameter of the rolling element of the first bearing. Thereby, the rigidity of the second bearing can be further enhanced.

  Preferably, the in-wheel motor drive further includes a casing for accommodating the reduction gear, and the first and second bearings are disposed between the outer diameter surface of the output shaft and the cylindrical surface formed on the casing There is.

  Preferably, the rotating wheel of the wheel hub bearing is an inner ring.

  The wheel hub bearing portion includes a fixed wheel coaxially arranged with the rotating wheel, and a plurality of rolling elements arranged in an annular gap between the rotating wheel and the fixed wheel. In this case, the pitch circle of the second bearing is larger than the pitch circle of the rolling elements of the wheel hub bearing portion, and the pitch circle of the first bearing is equal to or less than the pitch circle of the rolling elements of the wheel hub bearing portion It is also good.

  Preferably, the speed reducing portion includes an input shaft coupled to the motor rotation shaft, an input gear provided on the input shaft, a first intermediate gear meshing with the input gear, and a second intermediate gear meshing with the output gear. An intermediate shaft integrally provided with the first intermediate gear and the second intermediate gear; a first intermediate bearing positioned axially on one side with respect to the first intermediate gear and rotatably supporting the intermediate shaft; And a second intermediate bearing positioned on the other axial side with respect to the intermediate gear and rotatably supporting the intermediate shaft. In this case, it is further desirable that the pitch circle of the second intermediate bearing be larger than the pitch circle of the first intermediate bearing.

  Preferably, one axial direction side is the outer side in the vehicle width direction, and the other axial side is the inner side in the vehicle width direction.

  According to the present invention, the relatively high rigidity second bearing is disposed in the direction in which the axial load acts on the meshing portion of the output gear during normal rotation driving. This makes it possible to suppress the inclination of the output shaft during normal rotation driving that is frequently used. As a result, it is possible to suppress the vibration in the meshing portion of the output gear in most of the time of driving the vehicle, so it is possible to prevent or reduce noise.

BRIEF DESCRIPTION OF THE DRAWINGS It is a longitudinal cross-sectional view which cut | disconnects the in-wheel motor drive device which concerns on embodiment of this invention in a predetermined | prescribed plane, and expand | deploy and shows. It is a cross-sectional view which shows typically the internal structure of the deceleration part of the in-wheel motor drive device which concerns on embodiment of this invention. It is a perspective view which shows the state which looked at the output gearwheel in embodiment of this invention from diagonally upward. It is a perspective view which shows typically the meshing state of an output gearwheel and an intermediate gearwheel in embodiment of this invention. FIG. 7 is a diagram showing the rotation directions of the output gear and the intermediate gear in normal rotation drive and reverse rotation drive in the embodiment of the present invention. (A) is a figure which shows notionally the axial load which arises in an output gear at the time of normal rotation drive, (B) is a figure which shows notionally the radial load which arises in two rolling bearings at the time of normal rotation drive. Is (A) is a figure which shows notionally the axial load which arises in an output gear at the time of reverse drive, (B) is a figure which shows notionally the radial load which arises in two rolling bearings at the time of reverse drive, respectively. . It is a figure which shows the detailed structural example of the deceleration part in embodiment of this invention, and is a longitudinal cross-sectional view which cut | disconnects an in-wheel motor drive device in a predetermined | prescribed plane, and expand | deploys it. (A), (B) is a disassembled perspective view of the input-shaft unit of the deceleration part shown in FIG. (A), (B) is a disassembled perspective view of the intermediate shaft unit of the deceleration part shown in FIG. (A), (B) is a disassembled perspective view of the output-shaft unit of the deceleration part shown in FIG. It is a cross-sectional view which shows the internal structure of the deceleration part shown in FIG.

  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 characters and description thereof will not be repeated.

<About basic configuration example>
First, with reference to FIG. 1 and FIG. 2, the example of a basic composition of the in-wheel motor drive device 1 which concerns on embodiment of this invention is demonstrated. The in-wheel motor drive device 1 is mounted on a passenger vehicle such as an electric vehicle and a hybrid vehicle.

  FIG. 1 is a longitudinal sectional view showing an in-wheel motor drive device 1 according to an embodiment of the present invention cut at a predetermined plane and developed. FIG. 2 is a cross-sectional view showing the internal structure of the speed reducing portion 31 of the in-wheel motor drive device 1 and schematically shows a state as viewed from the outer side in the vehicle width direction. The predetermined plane shown in FIG. 1 is a development plane in which the plane including the axis M and the axis N shown in FIG. 2 and the plane including the axis N and the axis O are connected in this order. In FIG. 1, the left side of the drawing represents the outer side in the vehicle width direction (outboard side), and the right side of the drawing represents the inner side in the vehicle width direction (inboard side). In FIG. 2, each gear in the inside of the speed reduction unit 31 is represented by a tip circle, and individual teeth are omitted.

  The in-wheel motor drive device 1 decelerates the rotation of the wheel hub bearing portion 11 provided at the center of the wheel W, the motor portion 21 for driving the wheels, and the motor portion 21 and transmits the reduced speed to the wheel hub bearing portion 11 And a unit 31.

  The motor unit 21 and the speed reduction unit 31 are disposed offset from the axis O of the wheel 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 the outboard side, and the other side in the direction of the axis O is the inboard.

  With respect to the position in the direction of the axis O, the wheel hub bearing portion 11 is disposed at one axial direction of the in-wheel motor drive device 1, the motor portion 21 is disposed at the other axial direction of the in-wheel motor drive device 1, and the reduction portion 31 is a motor portion The axial position of the speed reducing portion 31 overlaps with the axial position of the wheel hub bearing portion 11.

  The in-wheel motor drive apparatus 1 is a motor drive apparatus for vehicles which drives the wheel of an electric vehicle. The in-wheel motor drive device 1 is connected to a vehicle body (not shown). The in-wheel motor drive device 1 can travel the electric vehicle at a speed of 0 to 180 km / h.

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

  The outer ring 13 penetrates the front portion 39f of the main body casing 39 and is connected and fixed to the front portion 39f. The front portion 39 f is a casing wall that covers one end of the main casing 39 in the direction of the axis O of the speed reduction portion 31. For example, on the outer peripheral surface of the outer ring 13, a plurality of outer ring projecting portions protruding in the outer diameter direction are provided at different positions in the circumferential direction, and one side of the through hole provided in each outer ring projecting portion Bolt is passed through. The shaft portion of each bolt is screwed with a female screw hole drilled in the front portion 39 f of the main body casing 39.

  The carrier member 61 is connected and fixed to the outer ring 13. On the outer peripheral surface of the outer ring 13, a plurality of outer ring protruding portions 13g protruding in the outer diameter direction are provided at different positions in the circumferential direction. The carrier member 61 is located on the other side of the outer ring projecting portion 13g in the direction of the axis O, and the bolt 62 is passed through the through hole of the outer ring projecting portion 13g and the female screw hole of the carrier member 61 from one side in the axis O direction. The carrier member 61 is fixed to the main body casing 39 by a bolt 63 passed from the other side in the axis O direction.

  The inner ring 12 is a cylindrical body longer than the outer ring 13, and is passed through the center hole of the outer ring 13. A coupling portion 12 f is formed at one end of the inner ring 12 in the direction of the axis O that protrudes from the outer ring 13 to the outside (outboard side). The coupling portion 12 f is a flange, and constitutes a coupling portion for coaxial coupling with the brake rotor BD and the wheel. The inner ring 12 is coupled to the wheel W at a coupling portion 12f and integrally rotates with the wheel.

  A plurality of 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 central portion in the direction of the axis O of the inner ring 12 constitutes an inner raceway surface of the plurality of rolling elements 14 arranged in the first row. An inner race 12r is fitted on the outer periphery of the other end of the inner ring 12 in the direction of the axis O. The outer peripheral surface of the inner race 12r constitutes an inner raceway surface of the plurality of rolling elements 14 arranged in the second row. The inner peripheral surface of the axial line O direction one end of the outer ring 13 constitutes the outer raceway surface of the first row of rolling elements 14. The inner circumferential surface of the other end of the outer ring 13 in the direction of the axis O forms the outer raceway surface of the second row of rolling elements 14. In the annular space between the inner ring 12 and the outer ring 13, a sealing material 16 is further interposed. The sealing material 16 seals both ends of the annular space to prevent the entry of dust and foreign matter. The output shaft 38 of the speed reduction unit 31 is inserted into the central hole at the other end of the inner ring 12 in the direction of the axis O, and spline fitting or serration fitting is performed.

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

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

  The main body casing 39, the motor casing 29, and the motor casing cover (rear cover) 29 v constitute a casing 10 forming an 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 ring-shaped steel plates in the axis M direction.

  Both end portions of the motor rotation shaft 22 are rotatably supported by the back surface portion 39 b of the main body casing 39 and the motor casing cover 29 v via the rolling bearings 27, 28. An axis M, which is the rotational center of the motor rotation shaft 22 and the rotor 23, extends parallel to the axis O of the wheel hub bearing portion 11. That is, the motor unit 21 is offset from the axis O of the wheel 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 longitudinal direction of the vehicle, and specifically, is disposed forward of the axis O in the vehicle.

  The speed reduction unit 31 includes an input shaft 32 coaxially coupled to the motor rotation shaft 22 of the motor unit 21, an input gear 33 coaxially provided on the outer peripheral surface of the input shaft 32, a plurality of intermediate gears 34 and 36, and these intermediate It has an intermediate shaft 35 coupled to the center of the gears 34 and 36, an output shaft 38 coaxially coupled to the inner ring 12 of the wheel hub bearing 11, and an output gear 37 coaxially provided on the outer peripheral surface of the output shaft 38. The plurality of gears and the rotation shaft of the speed reduction unit 31 are accommodated in the main body casing 39. Since the main body casing 39 forms the outer shell of the speed reduction portion 31, it is also referred to as a speed reduction portion casing.

  The input gear 33 is a helical gear with external teeth. The input shaft 32 has a hollow structure, and one axial end of the motor rotation shaft 22 is inserted into the hollow portion 32 h of the input shaft 32. As a result, the motor rotation shaft 22 is spline fitted (or serrated) to the input shaft 32 so as not to be relatively rotatable. The input shaft 32 is rotatably supported on the front portion 39f and the rear portion 39b of the main casing 39 via rolling bearings 32a and 32b at both ends of the input gear 33.

  An axis N, which is the center of rotation of the intermediate shaft 35 of the reduction gear 31, extends parallel to the axis O. Both ends of the intermediate shaft 35 are rotatably supported by the front portion 39f and the rear portion 39b of the main body casing 39 via bearings 35a and 35b. At a central portion of the intermediate shaft 35, a first intermediate gear 34 and a second intermediate gear 36 are provided coaxially with the axis N of the intermediate shaft 35. The first intermediate gear 34 and the second intermediate gear 36 are externally toothed helical gears, and the diameter of the first intermediate gear 34 is larger than the diameter of the second intermediate gear 36. The large diameter first intermediate gear 34 is disposed on the other side in the direction of the axis N relative to the second intermediate gear 36 and meshes with the small diameter input gear 33. The small diameter second intermediate gear 36 is disposed on one side in the axial direction N relative to the first intermediate gear 34 and meshes with the large diameter output gear 37.

  The axis N of the intermediate shaft 35 is disposed above the axis O and the axis M, as shown in FIG. The axis N of the intermediate shaft 35 is disposed forward of the axis O in the vehicle and rearward of the axis M in the vehicle. The speed reduction unit 31 is a three-axis parallel-axis gear reduction gear having axes O, N, and M which are disposed in a longitudinal direction of the vehicle at intervals and extend in parallel to each other.

  The output gear 37 is a helical gear with external teeth, and is coaxially provided at the center of the output shaft 38. The output shaft 38 extends along the axis O. One end of the output shaft 38 in the direction of the axis O is inserted into the center hole of the inner ring 12 and is fitted in a relatively non-rotatable manner. Such fitting is spline fitting or serration fitting. The central portion (one end side) of the output shaft 38 in the direction of the axis O is rotatably supported by the front portion 39f of the main casing 39 via the rolling bearing 38a. The other end (the other end) of the output shaft 38 in the direction of the axis O is rotatably supported by the rear surface portion 39 b of the main casing 39 via the rolling bearing 38 b.

  The rolling bearing 38 a is located on the outboard side of the output gear 37, and the rolling bearing 38 b is located on the inboard side of the output gear 37. The rolling bearings 38 a and 38 b are disposed between the outer diameter surface of the output shaft 38 and the cylindrical surface formed on the main body casing 39. Specifically, the outer ring of the rolling bearing 38a is fixed to the cylindrical surface formed on the front portion 39f of the main body casing 39, and the outer ring of the rolling bearing 38b is fixed to the cylindrical surface formed on the back portion 39b of the main body casing 39. It is fixed.

  The reduction portion 31 meshes with the small diameter drive gear and the large diameter driven gear, that is, the meshing of the input gear 33 and the first intermediate gear 34, and the meshing of the second intermediate gear 36 and the output gear 37. The rotation is decelerated and transmitted to the output shaft 38. The rotating elements from the input shaft 32 to the output shaft 38 of the speed reduction unit 31 constitute a drive transmission path for transmitting the rotation of the motor unit 21 to the inner ring 12. The input shaft 32, the intermediate shaft 35, and the output shaft 38 are supported on both sides by the above-described rolling bearing. These rolling bearings 32a, 35a, 38a, 32b, 35b, 38b are radial bearings.

  The main body casing 39 includes a cylindrical portion, and a plate-like front portion 39f and a rear portion 39b covering both ends of the cylindrical portion. The cylindrical portion covers the internal components of the speed reduction portion 31 so as to surround the axes O, N, M extending parallel to one another. The plate-like front portion 39 f covers the internal components of the speed reduction unit 31 from one side in the axial direction. The plate-like rear surface portion 39 b covers the internal components of the speed reduction unit 31 from the other side in the axial direction. As shown in FIG. 2, an oil tank 40 in which lubricating oil is stored is provided at the lower part of the main body casing 39.

  The back surface portion 39 b of the main body casing 39 is also a partition that is coupled to the motor casing 29 and partitions the internal space of the speed reduction unit 31 and the internal space of the motor unit 21. The motor casing 29 is supported by the main body casing 39 and protrudes from the main body casing 39 to the other side in the axial direction.

  When electric power is supplied to the stator 24 of the motor unit 21 from the outside of the in-wheel motor drive device 1, the rotor 23 of the motor unit 21 rotates and outputs rotation from the motor rotation shaft 22 to the speed reduction unit 31. The speed reduction unit 31 decelerates the rotation input from the motor unit 21 to the input shaft 32, and outputs the rotation from the output shaft 38 to the wheel hub bearing unit 11. The inner ring 12 of the wheel 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.

<About the rotational support structure of the 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 supported on both sides by two rolling bearings 38a and 38b having different axial positions. Thereby, since the output shaft 38 is stably rotationally supported, even if the inner ring 12 of the wheel hub bearing unit 11 coupled to the output shaft 38 is slightly displaced (deformed) by the external force accompanying the turning load, the output shaft The displacement (inclination) of 38 can be suppressed as much as possible.

  Here, in the present embodiment, as shown in FIGS. 3 and 4, a helical gear is applied as the output gear 37 coaxially coupled to the output shaft 38. The helical gear is a cylindrical gear in which tooth lines are formed in a helical line. FIG. 3 shows a state in which the output gear 37 is viewed obliquely from above, and FIG. 4 schematically shows the meshing state of the output gear 37 and the intermediate gear 36. As described above, in the case where the output gear 37 and the intermediate gear 36 are helical gears, since the tooth contact in the gear meshing portion is improved, (ideally) high quietness can be obtained.

  On the other hand, when the vehicle travels, that is, when the wheels are driven, an axial load specific to the helical gear is generated at the meshing portion (the meshing portion with the intermediate gear 36) of the output gear 37. Therefore, under 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 load higher than the other. Therefore, if the output shaft 38 is supported on both sides by the two rolling bearings 38a and 38b, the load may be biased to one of the bearings, and the output shaft 38 may be inclined.

  This will be described in detail with reference to FIGS. FIG. 5 is a view showing rotation directions of the output gear 37 and the intermediate gear 36 in forward rotation and reverse rotation respectively. FIG. 6A is a view conceptually showing an axial load generated on the output gear 37 at the time of normal rotation driving, and FIG. 6B is generated at each of two rolling bearings 38a and 38b at the time of normal rotation driving. It is a figure which shows a radial load notionally. FIG. 7A is a view conceptually showing an axial load generated on the output gear 37 at the time of reverse drive, and FIG. 7B is a radial load generated on each of the two rolling bearings 38a and 38b at the time of reverse drive. It is a figure which shows notionally. 5 shows the gears 36 and 37 viewed from the outboard side, and FIGS. 6A and 7A show the gears 36 and 37 shown in FIG. 5 from above. The viewed state is shown. Moreover, a part of longitudinal cross-sectional view of FIG. 1 is expanded and shown by FIG. 6 (B) and FIG. 7 (B).

  The twisting direction of the teeth of the output gear 37 in the embodiment is a so-called right twisting direction, and as shown in FIG. It inclines so that it may become the vehicle front rather than the side (axial direction one side). As shown in FIGS. 6A and 6B, the load generated at the meshing portion of the output gear 37 includes a radial component Fr (g) and an axial component Fa, and this load is on the outboard side. Are shared by the rolling bearing 38a and the rolling bearing 38b on the inboard side.

  The gear radial component Fr (g) generated at the gear meshing portion acts as a bearing radial component Fr (b) in the same direction as the gear radial component Fr (g) in the rolling bearings 38a and 38b. The radial components Fr (g) and Fr (b) represent radial inward radial forces. 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 at the gear meshing portion acts as bearing radial components Far in mutually opposite directions in the rolling bearings 38a and 38b. Since the axial center (axis O) of the output gear 37 and the meshing portion are offset in the radial direction, a moment about the axis about the axis O is generated, and the moment is calculated by the two rolling bearings 38a and 38b. Is received as a bearing radial component. The bearing radial component Far is referred to as a second bearing radial component Far.

  Specifically, the direction of the second bearing radial component Far is opposite between the rolling bearing 38a on the outboard side and the rolling bearing 38b on the inboard side. Therefore, in one of the bearings, 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 Fr (b) The bearing radial component Far is added. Therefore, when the output gear 37 is a helical gear, a large load is applied to only one of the two rolling bearings 38a and 38b that rotatably support the output shaft 38.

  More specifically, as shown in FIG. 6A, the direction of the axial load Fa generated at the meshing portion of the output gear 37 during forward rotation is on the outboard side. In FIG. 6A, the direction of the tangential force generated at the meshing portion of the output gear 37 at the time of normal rotation driving is indicated by a dotted line.

  In this case, as shown in FIG. 6B, the second bearing radial load Far acting on the outboard side rolling bearing 38a is directed radially inward and acts on the inboard side rolling bearing 38b. The direction of the second bearing radial load Far is radially outward. Therefore, during normal rotation driving, the rolling bearing 38a on the outboard side receives a higher radial load than the rolling bearing 38b on the inboard side.

  On the other hand, as shown in FIG. 7A, the direction of the axial load Fa generated at the meshing portion of the output gear 37 at the time of reverse driving is the inboard side. In FIG. 7A, the direction of the tangential force generated at the meshing portion of the output gear 37 at the time of reverse driving is indicated by a dotted line.

  In this case, as shown in FIG. 7B, the second bearing radial load Far acting on the outboard side rolling bearing 38a is directed radially outward and acts on the inboard side rolling bearing 38b. The direction of the second bearing radial load Far is radially inward. Therefore, at the time of reverse driving, the inboard rolling bearing 38b receives a higher radial load than the outboard rolling bearing 38a.

  As described above, when the output gear 37 is a helical gear, the magnitude relationship of the radial load applied to the two rolling bearings 38a and 38b that rotatably support the output shaft 38 during the normal rotation drive and the reverse rotation drive is reversed. Do.

  Here, in the present embodiment, the rigidity of the rolling bearing 38a on the outboard side, which receives a relatively high load during normal rotation driving, is set higher than the rigidity of the rolling bearing 38b on the inboard side. When the axial load Fa in the outboard direction is applied to the meshing portion of the output gear 37 during normal rotation driving, the relationship between the magnitude of the bearing load of the rolling bearings 38a and 38b and the rigidity is as follows.

  In the present embodiment, by making the pitch circle of the rolling bearing 38a on the outboard (OB) side larger than the pitch circle of the rolling bearing 38b on the inboard (IB) side, the rigidity of the rolling bearing 38a on the outboard side Is higher than the rigidity of the rolling bearing 38b on the inboard side. That is, as shown in FIG. 1, the PCD (pitch circle diameter D1) of the rolling bearing 38a on the outboard side is larger than the PCD (pitch circle diameter D2) of the rolling bearing 38b on the inboard side. Thereby, the number of rolling elements of the rolling bearing 38a on the outboard side is made larger than the number of rolling elements of the rolling bearing 38b on the inboard side, or the rolling elements of the rolling bearing 38a on the outboard side are inboard The rigidity of the rolling bearing 38a on the outboard side is higher than the rigidity of the rolling bearing 38b on the inboard side.

  Thus, in order to make the size of the pitch circle of the two rolling bearings 38a and 38b different, for example, as shown in FIG. 1, the inboard rolling bearings 38b are the inboard end of the output shaft 38. It may be provided in the level | step-difference part 38d provided in. Specifically, the inner ring of the rolling bearing 38 b is fitted into the step portion 38 d of the output shaft 38. As a result, the rolling bearing 38b on the motor unit 21 side (inboard side) can be made relatively compact, and the size of the pitch circle of the rolling bearing 38a on the outboard side need not be made larger than necessary. The radial dimension of the wheel motor drive device 1 can be reduced.

  In the embodiment shown in FIG. 1, the pitch circle of the rolling bearing 38a on the outboard side is larger than the pitch circle of the rolling element 14 of the wheel hub bearing 11, and the pitch circle of the rolling bearing 38b on the inboard side is It is equal to or less than the pitch circle of the rolling elements 14 of the wheel hub bearing portion 11.

  Further, the rolling bearing 38a on the outboard side is between the outer peripheral surface of the annular convex portion 37b erected on one end face of the output gear 37 in the direction of the axis O and the cylindrical surface formed on the front portion 39f of the main body casing 39. It may be arranged in The cylindrical surface of the front portion 39f is constituted by the inner peripheral surface of an annular convex portion 39i erected on the inner wall surface of the front portion 39f. In this case, the other end of the inner ring 12 and the outer ring 13 in the direction of the axis O may be accommodated in the space on the inner diameter side of the annular convex portion 37 b of the output gear 37.

  As described above, the rolling bearing 38 a may be disposed so as 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, (the rolling elements of) the rolling bearing 38a is at the position of the meshing portion between the output gear 37 and the intermediate gear 36 (that is, the width of the gear of the output gear 37). It is desirable to be provided at a position not overlapping with.

  By adopting the above arrangement form, the PCD (pitch circle diameter D1) of the outboard side rolling bearing 38a is 1.5 times or more of the PCD (pitch circle diameter D2) of the inboard side rolling bearing 38b, More preferably, it may be twice or more.

  As described above, by making the rolling bearing 38a on the outboard side higher in rigidity than the rolling bearing 38b on the inboard side, it is possible to suppress the inclination of the output shaft 38 during normal rotation driving. The normal rotation drive is overwhelmingly more frequently used and rotates at a higher speed than the reverse rotation drive. Therefore, by suppressing the inclination of the output shaft 38 at the time of normal rotation drive, it becomes possible to prevent or suppress the generation of the noise accompanying the vibration of the gear meshing portion during the traveling of the vehicle.

<About a detailed configuration example of the reduction gear>
8 to 12 show detailed configuration examples of the speed reducing portion configured by the three-axis parallel shaft 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 by cutting it along a predetermined plane and developing it. FIGS. 9A and 9B are exploded perspective views of the input shaft unit of the speed reduction unit 31A. FIGS. 10A and 10B are exploded perspective views of the intermediate shaft unit of the reduction gear 31A. 11A and 11B are exploded perspective views of the output shaft unit of the speed reduction unit 31A. FIG. 12 is a view corresponding to FIG. 2 and is a cross-sectional view showing the internal structure of the speed reducing portion 31A of the in-wheel motor drive device 1A, schematically showing a state as viewed from the outer side in the vehicle width direction. In each of FIGS. 9 to 11, (A) shows a perspective view of each shaft unit viewed from the outer side in the vehicle width direction, and (B) shows a perspective view of each shaft unit viewed from the inner side in the vehicle width direction. Represents

  The basic configuration itself of in-wheel motor drive device 1A shown in FIG. 8 is the same as in-wheel motor drive device 1 shown in FIGS. 1 and 2. The decelerating portion 31A of the in-wheel motor drive device 1A is also provided on the input shaft 32, the intermediate shaft 35, the output shaft 38, the input gear 33 provided on the input shaft 32, and the intermediate shaft 35 as described above. The intermediate gears 34, 36, the output gear 37 provided on the output shaft 38, and rolling bearings 32a, 35a, 38a, 32b, 35b, 38b for supporting the shafts 32, 35, 38 are included. In the following description, the direction along the axis M, N, O will be referred to as "axial direction".

  Referring to FIGS. 8 and 9, the input shaft unit includes an input shaft 32, an input gear 33 integrally provided with the input shaft 32, and a pair of rolling bearings 32a rotatably supporting the input shaft 32, And 32b. The input gear 33 is integrally formed with the input shaft 32. The input gear 33 is provided at the axial center of the input shaft 32. Rolling bearings 32 a and 32 b are respectively fitted on the outer peripheral surfaces of both axial end portions 71 and 72 of the input shaft 32. The inner rings of the rolling bearings 32a and 32b may be in contact with one axial end face and the other end face of the input gear 33, respectively.

  The outer diameter dimensions of both end portions 71 and 72 of the input shaft 32 are equal to each other. In this case, it is desirable that the rolling bearings 32a and 32b be constituted by bearings of the same standard. That is, as for PCD of rolling bearing 32a, 32b, inside diameter size, outside diameter size, diameter and number of rolling elements, it is desirable that they are mutually equal. Thereby, since parts can be made common regarding the support structure of the input shaft 32, a manufacturing cost can be reduced.

  Referring to FIGS. 8 and 10, the intermediate shaft unit includes an intermediate shaft 35, two intermediate gears 34 and 36 integrally provided with the intermediate shaft 35, and a pair of rotatably supporting the intermediate shaft 35. It comprises rolling bearings 35a and 35b. The large diameter intermediate gear 34 is integrally formed with the intermediate shaft 35. On the other hand, the small-diameter intermediate gear 36 is separate from the intermediate shaft 35, and is spline-fitted (press-fitted) to the intermediate shaft 35. Specifically, the intermediate shaft 35 includes a spline portion 83 in which the outer peripheral surface is repeatedly provided with irregularities, and a spline groove provided on the inner peripheral surface 85 of the intermediate gear 36 is fitted to the spline portion 83. . Thus, the intermediate gear 36 is integrally coupled to the intermediate shaft 35.

  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. As a result, since the hollow hole 86 can be used as a lubricating oil passage, the lubricating performance of the speed reduction portion 31A is improved.

  Rolling bearings 35 a and 35 b are respectively fitted on the outer peripheral surfaces of the axially opposite end portions 81 and 82 of the intermediate shaft 35. One end 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 inboard side may be disposed in an annular recess 87 provided on the other axial end face of the large-diameter intermediate gear 34. Thereby, the axial dimension of the intermediate shaft 35 can be shortened.

  The outer diameter dimension of the other end 82 of the intermediate shaft 35 is larger than the outer diameter dimension of the one end 81. Therefore, the PCD (pitch circle diameter D3) of the inboard side rolling bearing 35b is larger than the PCD (pitch circle diameter D4) of the outboard side rolling bearing 35a. In the in-wheel motor drive device 1A, the bearing span of the gear shaft (the input shaft 32, the intermediate shaft 35, the output shaft 38) is short due to the request for miniaturization of the axial dimension, and therefore the tilt of the gear shaft increases with radial displacement. The amount is relatively large. During forward driving, an axial load is generated in the inboard side at the meshing portion of the intermediate gear 36 on the rear stage side, and an axial load is generated in the meshing portion of the intermediate gear 34 on the front side toward the outboard side. Occur. Since the torque becomes higher toward the rear, the axial load toward the inboard side of the intermediate shaft 35 is relatively larger.

  Therefore, as described above, the rigidity of the rolling bearing 35b can be secured by making the inboard rolling bearing 35b larger in diameter than the outboard rolling bearing 35a. Specifically, even when the diameters of the rolling elements (steel balls) of both bearings 35a and 35b are the same, the number of rolling elements 89b of the rolling bearing 35b should be larger than the number of rolling elements 89a of the rolling bearing 35a. Can. As a result, since the inclination of the intermediate shaft 35 can be suppressed at the time of normal rotation drive, the misalignment of the tooth surface contact is reduced. As a result, it is possible to suppress the occurrence of vibration 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.

  The number of rolling elements 89b of the rolling bearing 35b is further increased by making the diameter of the rolling elements 89b of the rolling bearing 35b on the inboard side smaller than the rolling elements 89a of the rolling bearing 35a on the outboard side. Good. Thereby, since the rated load of the rolling bearing 35b can be increased, the rigidity of the rolling bearing 35b can be enhanced. Further, since the width dimension of the inboard rolling bearing 35b can be made smaller than the width dimension of the outboard rolling bearing 35a, the axial dimension of the intermediate shaft 35 can be shortened.

  The intermediate gear 36 is located between the rolling bearing 35 a and the large diameter intermediate gear 34. As shown in FIG. 8, it is desirable that the outer diameter dimension D5 of the inner ring 88 of the rolling bearing 35 a be larger than the (maximum) outer diameter dimension D6 of the spline portion 83 of the intermediate shaft 35. Thereby, since the inner ring 88 of the rolling bearing 35a and the axial direction one end face of the intermediate gear 36 come in contact with each other, it is possible to prevent the intermediate gear 36 from coming off the intermediate shaft 35 due to vibration or the like. Even when an axial load in the outboard direction is generated at the meshing portion of the intermediate gear 36 during reverse driving, the inner ring 88 of the rolling bearing 35 a also acts as a retainer for the intermediate gear 36.

  The movement of the rolling bearing 35a in the axial direction to one side is restricted by the ring-shaped elastic member 84 fitted in the groove 81a provided at the one end 81 of the intermediate gear 36.

  Referring to FIGS. 8 and 11, the output shaft unit includes an output shaft 38, an output gear 37 integrally provided with the output shaft 38, and a pair of rolling bearings 38a rotatably supporting the output shaft 38, And 38b. The output gear 37 is integrally formed with the output shaft 38. The output gear 37 is provided at the axial center of the output shaft 38. A spline portion 93 for spline fitting with the inner ring 12 of the wheel hub bearing portion 11 is provided on the outer peripheral surface of the axial direction one end portion of the output shaft 38.

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

  The output shaft 38 has a protrusion 94 that protrudes further inboard (the other side in the axial direction) than the fitting with the inboard rolling bearing 38b, and the oil pump 63 is attached to the protrusion 94. It may be In this case, it is desirable that the outer diameter dimension (diameter of the outer peripheral surface of the outer ring) D7 of the inboard side rolling bearing 38b be larger than the outer diameter dimension D8 of the oil pump 63.

  Since the rolling bearing 38a on the outboard side is affected by the axial load during normal rotation driving, as shown in FIG. 1, the PCD (pitch circle diameter D1) of the rolling bearing 38a on the outboard side is on the inboard side. It is larger than PCD (pitch circle diameter D2) of the rolling bearing 38b. In addition, it is also desirable to make the diameter of the rolling element 99a of the rolling bearing 38a on the outboard side smaller than that of the rolling element 99b of the rolling bearing 38b on the inboard side to further increase the number of rolling elements 99a of the rolling bearing 38a. As a result, the rated load of the rolling bearing 38a is increased, and the rigidity of the rolling bearing 38a is further enhanced. In this case, since the width dimension of the rolling bearing 38a on the outboard side can be made smaller than the width dimension of the rolling bearing 38b on the inboard side, the axial dimension of the output shaft 38 can also be shortened.

  As described above, the speed reduction unit 31A may have the following features.

  The rolling bearing 32a on the outboard side of the input shaft 32 and the rolling bearing 32b on the inboard side are constituted by the same bearing.

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

(Modification 1)
In the above embodiment, although the teeth of the output gear 37 are twisted in the right direction, the teeth of the output gear may be twisted in the left. That is, the tip of the output gear may be inclined so that the outboard side (one side in the axial direction) is forward of the vehicle than the inboard side (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 at the time of normal rotation drive is on the inboard side, the rolling bearing on the inboard side and the rolling bearing on the outboard side are contrary to the above embodiment. The rigidity should be higher than that. That is, in this case, the pitch circle of the inboard rolling bearing may be larger than the pitch circle of the outboard rolling bearing.

  As described above, when the direction of the axial load generated at the meshing portion of the output gear is "axially one side" during normal rotation driving, a relatively high rigidity rolling bearing is provided at a position on the one axial side of the output gear. The (second bearing) may be disposed, and a relatively low-rigidity rolling bearing (first bearing) may be disposed at a position on the other side in the axial direction relative to the output gear.

(Modification 2)
In the above-described embodiment, the rotating wheel of the wheel hub bearing portion 11 is the inner ring, but the rotating ring may be the outer ring. That is, the rotation support structure of the output shaft as described above can also be applied to an in-wheel motor drive provided with a wheel hub bearing portion of a rotating outer ring and a fixed inner ring type.

(Modification 3)
In the above embodiment, an example in which the reduction unit 31 is a three-axis parallel shaft gear reduction gear is shown, but the reduction unit is, for example, another type gear reduction gear such as a four-axis parallel shaft gear reduction gear May be

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all the modifications within the meaning and scope equivalent to the claims.

  1, 1 A In-wheel motor drive device, 10 casing, 11 wheel hub bearing portion, 12 inner ring, 13 outer ring, 14 rolling element, 21 motor portion, 22 motor rotating 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, 31, 31A reduction unit, 32 input shaft, 33 input gear, 34, 36 intermediate gear, 35 intermediate shaft, 37 output gear, 38 output shaft, 39 body casing, M, N, O axis, W wheel wheel.

Claims (8)

A wheel hub bearing having a rotating wheel to which the wheel is attached;
An output shaft connected to the rotating wheel of the wheel hub bearing portion, an output gear which is a helical gear connected coaxially to the output shaft, and a first bearing rotatably supporting the output shaft. And a decelerator including a second bearing rotatably supporting the output shaft and having rigidity higher than that of the first bearing.
When the direction of the axial load generated in the meshing portion of the output gear is one side in the axial direction of the output shaft during normal rotation driving, the second bearing is positioned at the one side in the axial direction with respect to the output gear. An in-wheel motor drive device characterized in that the first bearing is disposed at a position on the other side in the axial direction with respect to the output gear.   The in-wheel motor drive according to claim 1, wherein a pitch circle of the second bearing is larger than a pitch circle of the first bearing.   The in-wheel motor drive according to claim 2, wherein the diameter of the rolling element of the second bearing is smaller than the diameter of the rolling element of the first bearing. It further comprises a casing for accommodating the reduction gear,
The in-wheel motor drive according to any one of claims 1 to 3, wherein the first and second bearings are disposed between an outer diameter surface of the output shaft and a cylindrical surface formed in the casing. .   The in-wheel motor drive according to any one of claims 1 to 4, wherein the rotating wheel of the wheel hub bearing portion is an inner ring. The wheel hub bearing portion includes a fixed wheel coaxially arranged with the rotating wheel, and a plurality of rolling elements arranged in an annular gap between the rotating wheel and the fixed wheel,
The pitch circle of the second bearing is larger than the pitch circle of the rolling elements of the wheel hub bearing portion, and the pitch circle of the first bearing is equal to or less than the pitch circle of the rolling elements of the wheel hub bearing portion The in-wheel motor drive according to claim 5. The speed reducing portion includes an input shaft connected to a motor rotation shaft, an input gear provided on the input shaft, a first intermediate gear meshing with the input gear, and a second intermediate gear meshing with the output gear. An intermediate shaft integrally provided with the first intermediate gear and the second intermediate gear, and a first intermediate shaft positioned on one side in the axial direction with respect to the first intermediate gear and rotatably supporting the intermediate shaft A bearing, and a second intermediate bearing positioned on the other axial side with respect to the second intermediate gear and rotatably supporting the intermediate shaft,
The in-wheel motor drive according to any one of claims 1 to 6, wherein a pitch circle of the second intermediate bearing is larger than a pitch circle of the first intermediate bearing.   The in-wheel motor drive according to any one of claims 1 to 7, wherein the one axial direction side is the outer side in the vehicle width direction, and the other axial side is the inner side in the vehicle width direction.

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