Transmission

Abstract

To support a rotating shaft in a stably rotatable manner.SOLUTION: A speed reducer 1 comprises an input gear unit 10 connected to a rotor shaft 42 of a drive unit 40. The input gear unit 10 comprises: an input shaft 11 connected to the rotor shaft 42, and comprising a first input shaft raceway surface K11 in an outer peripheral surface; a first input shaft outer ring 13 provided so as to surround the first input shaft raceway surface K11, and comprising a first input shaft outer ring raceway surface L11 in an inner peripheral surface 13b; and a plurality of rolling bodies 14.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a transmission for decreasing or increasing the rotational speed of a drive unit. [Background technology]

[0002] For example, as described in Patent Document 1, there is a transmission (reduction gear) that reduces the rotation speed of the drive shaft of a drive unit and outputs it. Such a transmission has multiple rotating shafts with gears, and reduces the rotation speed by sequentially transmitting the rotation of the drive shaft to the multiple rotating shafts by engaging the gears with each other. For this reason, such a transmission is provided with multiple bearings that rotatably support the rotating shaft with respect to the housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-3048 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, since the above-mentioned transmission sequentially slows down or speeds up the rotational speed of the drive shaft of the drive unit using gears, if any wobble occurs in the rotating shaft on which the gears are mounted, it is possible that rotational performance, durability, etc. will be reduced.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a transmission that can stably and rotatably support a rotating shaft. [Means for solving the problem]

[0006] A transmission according to a first aspect of the present invention includes a first shaft unit connected to a drive shaft of a drive unit, and the first shaft unit includes a first shaft connected to the drive shaft and having a first shaft raceway surface on its outer peripheral surface, a first output gear provided on the first shaft and rotating integrally with the first shaft, a first outer ring attached to a first support portion supporting the first shaft and arranged to surround the first shaft raceway surface, and having a first outer ring raceway surface on its inner peripheral surface, and a plurality of first rolling elements arranged between the first shaft raceway surface and the first outer ring raceway surface.

[0007] In this transmission, the first shaft, which is a rotating shaft connected to the drive shaft of the drive unit, is rotatably supported by the first support part via the first rolling element and the first outer ring. In other words, the first shaft also functions as the inner ring of the bearing. In this way, this transmission can reduce the number of parts in the mechanism that supports the first shaft, and can suppress a decrease in support accuracy of the first shaft due to variations in part accuracy, etc. Therefore, in this transmission, the first shaft (rotating shaft) connected to the drive shaft of the drive unit can be stably and rotatably supported.

[0008] In the above transmission, the first rolling element is a ball, the first shaft raceway surface is a groove extending in the circumferential direction of the outer circumferential surface of the first shaft, and of a pair of groove bottom portions extending in the circumferential direction of the outer circumferential surface of the first shaft in the groove constituting the first shaft raceway surface, the groove bottom portion closer to the first output gear may have a larger diameter than the other groove bottom portion. In this case, even when the first rolling element receives an axial load of the first shaft, this transmission can prevent the first rolling element from riding up the groove (first shaft raceway surface) by making the height of the groove bottom portion receiving the load higher than the other.

[0009] In the above transmission, the first rolling elements are balls, the first shaft raceway surface is a groove extending in the circumferential direction of the outer circumferential surface of the first shaft, the first shaft includes a raceway surface forming portion where the first shaft raceway surface is provided, and an intermediate portion between the raceway surface forming portion and the first output gear, and the outer diameter of the intermediate portion may be larger than the outer diameter of the raceway surface forming portion. In this case, the transmission can improve the rigidity of the first shaft around the first gear.

[0010] In the above transmission, the axial shape of the first shaft in the groove of the first shaft raceway surface is an arc shape along the raceway groove virtual circle, and the intermediate portion and the first output gear do not need to interfere with the raceway groove virtual circle. In this case, the transmission can appropriately position the balls, which are the first rolling elements, in the groove, which is the first shaft raceway surface, without interfering with the intermediate portion and the first output gear.

[0011] The transmission may be provided with a gap of a predetermined standard length or more between the first outer ring and the intermediate portion in the axial direction of the first shaft. In this case, the transmission can prevent the balls as the first rolling elements from interfering with the intermediate portion even if the balls as the first rolling elements move in the axial direction of the first shaft when the first shaft rotates.

[0012] The above-mentioned transmission further includes a retainer that holds each of the plurality of rolling elements so that they can roll freely, and the retainer may protrude outward from an end of the first outer ring in the axial direction of the first shaft. Here, a general bearing including an inner ring, an outer ring, a plurality of rolling elements, and a retainer that holds the rolling elements is carried in a pre-assembled state and then assembled to the transmission. In such a bearing, the retainer is configured so that it does not protrude from the inner ring and the outer ring in the axial direction so that the retainer is not damaged by external impact or the like during transportation. However, the transmission of the present application does not have the configuration of a general bearing in which the inner ring, the outer ring, the plurality of rolling elements, and the retainer are assembled, and is not subject to structural constraints to prevent damage to the retainer during transportation. Therefore, this transmission can suppress the constraints on the retainer, and can increase the design freedom of the retainer.

[0013] In the above transmission, the first shaft may be provided with a first oil passage extending along the axial direction of the first shaft, the first shaft may be provided with a first oil hole communicating with the first oil passage and the outer peripheral surface of the first shaft, and at least a part of an opening of the first oil hole in the outer peripheral surface of the first shaft may face the inner peripheral surface of the first outer ring in the radial direction of the first shaft. In this case, the transmission can improve the performance of supplying lubricating oil to the first shaft raceway surface and the first outer ring raceway surface.

[0014] In the above transmission, the first oil hole may extend along the radial direction of the first shaft and be provided upstream of the first shaft raceway surface in the oil flow direction of the first oil passage in the axial direction of the first shaft. In this case, in this transmission, the supply path of the lubricating oil to the first shaft raceway surface, etc. can be shortened, and the lubricating oil can be supplied more appropriately.

[0015] In the above transmission, an O-ring may be provided between the outer peripheral surface of the first outer ring and the first support portion so as to surround the first outer ring. In this case, the transmission can suppress the occurrence of creep caused by the first outer ring receiving a rotational load or whirling.

[0016] In the above transmission, the outer peripheral surface of the first outer ring may be provided with a coating having lower friction than the outer peripheral surface of the first outer ring. In this case, the transmission can suppress the occurrence of creep caused by the first outer ring receiving a rotational load or whirling.

[0017] The above-mentioned transmission further includes a second shaft unit to which power is transmitted from the first shaft unit, the second shaft unit including a second shaft having a second shaft raceway surface on its outer circumferential surface, a second input gear provided on the second shaft, meshing with the first output gear and rotating integrally with the second shaft, a second output gear provided on the second shaft and rotating integrally with the second shaft, a second outer ring provided on a second support part supporting the second shaft, surrounding the second shaft raceway surface, and having a second outer ring raceway surface on its inner circumferential surface, and a plurality of second rolling elements disposed between the second shaft raceway surface and the second outer ring raceway surface, and the rotation axis of the first shaft and the rotation axis of the second shaft may be parallel to each other. In this case, in this transmission, the second shaft to which power is transmitted from the first shaft unit is rotatably supported by the second support part via the second rolling elements and the second outer ring. In other words, the second shaft also functions as the inner ring of the bearing. In this way, this transmission can reduce the number of parts in the mechanism that supports the second shaft, and can suppress a decrease in support accuracy of the second shaft due to variations in part accuracy, etc. Therefore, this transmission can stably support the second shaft (rotating shaft) to which power is transmitted from the first shaft unit so that it can rotate.

[0018] In the above transmission, the second rolling element is a tapered roller, the second shaft raceway surface is tapered, the second shaft further has a second small rib portion provided adjacent to the small diameter side end of the second shaft raceway surface of the tapered rib, a second oil passage extending along the axial direction of the second shaft is provided inside the second shaft, and the second shaft may further have a second oil hole communicating with the second oil passage and the outer circumferential surface of the second small rib. In this case, the transmission rotatably supports the second shaft by the structure of a tapered roller bearing. The transmission can supply lubricating oil from the outer circumferential surface of the second small rib to the second shaft raceway surface, etc., and can supply lubricating oil more effectively by the pumping action of the tapered roller bearing.

[0019] In the above transmission, the second rolling elements are balls, the second shaft raceway is a groove extending in the circumferential direction of the outer circumferential surface of the second shaft, a second oil passage extending along the axial direction of the second shaft is provided inside the second shaft, and the second shaft is further provided with a second oil hole communicating with the second oil passage and the outer circumferential surface of the second shaft, and an opening of the second oil hole that opens into the outer circumferential surface of the second shaft may be adjacent to the second shaft raceway. In this case, the transmission can appropriately supply lubricating oil to the second shaft raceway etc. through the second oil hole.

[0020] In the above transmission, the second rolling elements are tapered rollers, the second shaft raceway surface has a truncated cone shape, and the second shaft does not need to be provided with a small flange portion adjacent to the small diameter end of the truncated cone shape of the second shaft raceway surface. In this case, the ease of assembly of each part of the second shaft unit can be improved in this transmission.

[0021] The above transmission may further include a differential gear unit to which power is transmitted from the second shaft unit, the differential gear unit including a differential case having a third shaft raceway surface on its outer circumferential surface, a third input gear provided in the differential case, meshing with the second output gear and rotating integrally with the differential case, a differential mechanism provided in the differential case, a third outer ring attached to a third support portion supporting the differential case, provided so as to surround the third shaft raceway surface, and having a third outer ring raceway surface on its inner circumferential surface, and a plurality of third rolling elements disposed between the third shaft raceway surface and the third outer ring raceway surface, and the rotation axis of the second shaft and the rotation axis of the differential case may be parallel to each other. In this case, the differential case to which power is transmitted from the second shaft unit is rotatably supported by the third support portion via the third rolling elements and the third outer ring. In other words, the differential case also functions as the inner ring of the bearing. In this way, this transmission can reduce the number of parts in the mechanism that supports the differential case, and can suppress a decrease in support accuracy of the differential case due to variations in part accuracy, etc. Therefore, this transmission can stably support the differential case (rotating shaft) to which power is transmitted from the second axle unit so that it can rotate.

[0022] In the above transmission, the third rolling element is a tapered roller, the third shaft raceway surface is tapered, the differential case further has a third small flange portion provided adjacent to the small diameter end of the third shaft raceway surface of the tapered shape, a third oil passage is provided inside the differential case, and the differential case may further have a third oil hole communicating with the third oil passage and the outer peripheral surface of the third small flange portion. In this case, the differential case is rotatably supported by a tapered roller bearing structure. The transmission can supply lubricating oil from the outer peripheral surface of the third small flange portion to the third shaft raceway surface, etc., and can supply lubricating oil more effectively by the pumping action of the tapered roller bearing.

[0023] In the above transmission, the third rolling element may be a tapered roller, the third shaft raceway surface may be a cone-frustum shape, and the differential case may not be provided with a small flange portion adjacent to the small diameter end of the cone-frustum shape of the third shaft raceway surface. In this case, the ease of assembly of each part of the differential gear unit in this transmission can be improved.

[0024] The above transmission may further include a drive unit, and the drive unit may include a drive mechanism, a drive shaft having a fourth shaft raceway surface on its outer circumferential surface, which is rotationally driven by the drive mechanism and connected to the first shaft, a fourth outer ring attached to a fourth support part supporting the drive shaft, which is provided so as to surround the fourth shaft raceway surface, and which has a fourth outer ring raceway surface on its inner circumferential surface, and a plurality of fourth rolling elements arranged between the fourth shaft raceway surface and the fourth outer ring raceway surface. In this case, the drive shaft of the drive unit is rotatably supported by the fourth support part via the fourth rolling elements and the fourth outer ring. That is, the drive shaft also functions as the inner ring of the bearing. In this way, the transmission can reduce the number of parts of the mechanism supporting the drive shaft, and can suppress a decrease in support accuracy of the drive shaft due to variations in part accuracy, etc. Therefore, even when the transmission includes a drive unit, the drive shaft (rotating shaft) of the drive unit can be stably and rotatably supported.

[0025] In the above transmission, the drive shaft is provided with a fourth oil passage extending along the axial direction of the drive shaft, and the drive shaft is further provided with a fourth oil hole communicating with the fourth oil passage and the outer peripheral surface of the drive shaft, and the opening of the fourth oil hole that opens into the outer peripheral surface of the drive shaft may be adjacent to the fourth shaft raceway. In this case, the transmission can appropriately supply lubricating oil to the fourth shaft raceway etc. via the fourth oil hole.

[0026] The above transmission may further include a drive unit, and the drive unit may include a drive mechanism, a drive shaft having a fourth shaft raceway on its inner peripheral surface, which is rotationally driven by the drive mechanism and connected to the first shaft, a fourth inner ring attached to the outer periphery of a fourth support part supporting the drive shaft from the inside of the fourth shaft raceway surface, which is provided inside the fourth shaft raceway surface and has a fourth inner ring raceway surface on its outer periphery surface, and a plurality of fourth rolling elements arranged between the fourth shaft raceway surface and the fourth inner ring raceway surface. In this case, the drive shaft of the drive unit is rotatably supported by the fourth support part via the fourth rolling elements and the fourth inner ring. That is, the drive shaft also functions as the outer ring of the bearing. In this way, the number of parts of the mechanism supporting the drive shaft can be reduced, and a decrease in support accuracy of the drive shaft due to variations in part accuracy or the like can be suppressed. Therefore, even when the transmission includes a drive unit, the drive shaft (rotating shaft) of the drive unit can be stably and rotatably supported.

[0027] In the above transmission, at least one of the number of teeth of the first output gear and the number of the first rolling bodies may be a prime number. In the above transmission, at least one of the number of teeth of the first output gear, the number of the first rolling bodies, the number of teeth of the second input gear, the number of teeth of the second output gear, and the number of the second rolling bodies may be a prime number. In the above transmission, at least one of the number of teeth of the first output gear, the number of the first rolling bodies, the number of teeth of the second input gear, the number of teeth of the second output gear, the number of the second rolling bodies, the number of teeth of the third input gear, and the number of the third rolling bodies may be a prime number. In these cases, the transmission can reduce vibration due to resonance of each part.

[0028] A transmission according to a second aspect of the present invention includes a second shaft unit to which power is transmitted from a first shaft unit connected to a drive shaft of a drive unit, the second shaft unit including a second shaft having a second shaft raceway surface on its outer peripheral surface, a second input gear provided on the second shaft and meshing with a first output gear provided on the first shaft unit and rotating integrally with the second shaft, a second output gear provided on the second shaft and rotating integrally with the second shaft, a second outer ring attached to a second support portion supporting the second shaft and arranged so as to surround the second shaft raceway surface and having a second outer ring raceway surface on its inner peripheral surface, and a plurality of second rolling elements arranged between the second shaft raceway surface and the second outer ring raceway surface, and the rotation axis of the first shaft and the rotation axis of the second shaft of the first shaft unit are parallel to each other.

[0029] In this transmission, the second shaft to which power is transmitted from the first shaft unit is rotatably supported by the second support part via the second rolling element and the second outer ring. In other words, the second shaft also functions as the inner ring of the bearing. In this way, this transmission can reduce the number of parts in the mechanism that supports the second shaft, and can suppress a decrease in support accuracy of the second shaft due to variations in part accuracy, etc. Therefore, in this transmission, the second shaft (rotating shaft) to which power is transmitted from the first shaft unit can be stably and rotatably supported.

[0030] A transmission according to a third aspect of the present invention includes a differential gear unit to which power is transmitted from a first shaft unit connected to a drive shaft of a drive unit via a second shaft unit, the differential gear unit including a differential case having a third shaft raceway surface on its outer peripheral surface, a third input gear provided on the differential case, which meshes with a second output gear provided on the second shaft unit and rotates integrally with the differential case, a differential mechanism provided within the differential case, a third outer ring attached to a third support part that supports the differential case and is provided so as to surround the third shaft raceway surface and has a third outer ring raceway surface on its inner peripheral surface, and a plurality of third rolling elements arranged between the third shaft raceway surface and the third outer ring raceway surface, and the rotation axis of the first shaft of the first shaft unit, the rotation axis of the second shaft of the second shaft unit, and the rotation axis of the differential case are parallel to each other.

[0031] In this transmission, the differential case to which power is transmitted from the second axle unit is rotatably supported on the third support portion via the third rolling element and the third outer ring. In other words, the differential case also functions as the inner ring of the bearing. In this way, this transmission can reduce the number of parts in the mechanism that supports the differential case, and can suppress a decrease in the support accuracy of the differential case due to variations in part accuracy, etc. Therefore, in this transmission, the differential case (rotating shaft) to which power is transmitted from the second axle unit can be stably and rotatably supported. Effect of the Invention

[0032] According to various aspects of the present invention, the rotating shaft can be stably and rotatably supported. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a cross-sectional view showing a main part of a reducer according to an embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the input gear unit and its surroundings in FIG. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of the first input shaft raceway surface and the second input shaft raceway surface and their surroundings. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the counter gear unit and its surroundings in FIG. [Diagram 5] FIG. 5 is an enlarged cross-sectional view of the differential gear unit and its surroundings in FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view of the drive unit and its surroundings in FIG. [Figure 7] FIG. 7 is an enlarged cross-sectional view of an input gear unit according to a first modified example. [Figure 8] FIG. 8 is an enlarged cross-sectional view of an input gear unit according to a second modified example. [Figure 9] FIG. 9 is an enlarged cross-sectional view of an input gear unit according to a third modified example. [Figure 10]FIG. 10 is an enlarged sectional view of an input gear unit according to a fourth modified example. [Figure 11] FIG. 11 is an enlarged sectional view of an input gear unit according to a fifth modified example. [Figure 12] FIG. 12 is an enlarged sectional view of a counter gear unit according to a first modified example. [Figure 13] FIG. 13 is an enlarged sectional view of a counter gear unit according to a second modified example. [Figure 14] FIG. 14 is an enlarged sectional view of a counter gear unit according to a third modified example. [Figure 15] FIG. 15 is an enlarged cross-sectional view of a differential gear unit according to a first modified example. [Figure 16] FIG. 16 is an enlarged cross-sectional view of a differential gear unit according to the second modified example. [Figure 17] FIG. 17 is an enlarged cross-sectional view of a drive unit according to a first modified example. [Figure 18] FIG. 18 is an enlarged cross-sectional view of a drive unit according to a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and duplicated explanations will be omitted. In addition, in the following, a reduction gear that reduces the rotational speed of a drive unit will be used as the transmission according to the present invention.

[0035] As shown in Fig. 1, the reducer (transmission) 1 includes an input gear unit (first shaft unit) 10, a counter gear unit (second shaft unit) 20, a differential gear unit 30, and a drive unit 40. The drive unit 40 includes an electric motor. The reducer 1 in this embodiment is configured as a three-shaft parallel reducer for an EV (Electric Vehicle) having the drive unit 40, as an example. The reducer 1 includes a housing that houses each mechanism such as the input gear unit 10, although this is omitted in Fig. 1.

[0036] [Input gear unit configuration] The input gear unit 10 is connected to the rotor shaft 42 of the drive unit 40. That is, the rotation of the rotor shaft 42 of the drive unit 40 is directly transmitted to the input gear unit 10. More specifically, the input gear unit 10 includes an input shaft (first shaft) 11, an input shaft output gear (first output gear) 12, a first input shaft outer ring (first outer ring) 13, a plurality of rolling elements (first rolling elements) 14, a first input shaft retainer (retainer) 15, a second input shaft outer ring (first outer ring) 16, a plurality of rolling elements (first rolling elements) 17, and a second input shaft retainer (retainer) 18, as shown in FIG.

[0037] The input shaft 11 is connected to the rotor shaft 42 of the drive unit 40. Here, a spline 11s is formed on the outer circumferential surface of the input shaft 11 at the end connected to the rotor shaft 42. The input shaft 11 is spline-coupled to the rotor shaft 42 by the spline 11s. In addition, the input shaft 11 has a first input shaft raceway surface (first shaft raceway surface) K11 and a second input shaft raceway surface (first shaft raceway surface) K12 on its outer circumferential surface.

[0038] The first input shaft raceway surface K11 is provided on the outer circumferential surface of the input shaft 11 near the end opposite to the end where the spline 11s is formed. The second input shaft raceway surface K12 is provided on the outer circumferential surface of the input shaft 11 near the spline 11s. The first input shaft raceway surface K11 and the second input shaft raceway surface K12 are grooves extending in the circumferential direction of the outer circumferential surface of the input shaft 11.

[0039] The input shaft output gear 12 is provided on the input shaft 11 and rotates integrally with the input shaft 11. The input shaft output gear 12 is provided at a position between the first input shaft raceway surface K11 and the second input shaft raceway surface K12. In this embodiment, the input shaft output gear 12 is provided integrally with the input shaft 11. The input shaft output gear 12 outputs power to the counter gear unit 20.

[0040] The first input shaft outer ring 13 is attached to an input shaft support part (first support part) C1 that supports the input shaft 11. The input shaft support part C1 is, for example, a part of a housing that houses the input gear unit 10 and the like. The first input shaft outer ring 13 is provided so as to surround the first input shaft raceway surface K11. The first input shaft outer ring 13 has an outer peripheral surface 13a that is attached to the input shaft support part C1, and an inner peripheral surface 13b that faces the outer peripheral surface of the input shaft 11 (the first input shaft raceway surface K11).

[0041] The first input shaft outer ring 13 has a first input shaft outer ring raceway surface (first outer ring raceway surface) L11 on its inner circumferential surface 13b. The first input shaft outer ring raceway surface L11 is a groove extending in the circumferential direction of the inner circumferential surface 13b of the first input shaft outer ring 13.

[0042] The multiple rolling elements 14 are disposed between the first input shaft raceway surface K11 of the input shaft 11 and the first input shaft outer ring raceway surface L11 of the first input shaft outer ring 13. The rolling elements 14 are spherical balls. The first input shaft retainer 15 holds each of the multiple rolling elements 14 between the outer peripheral surface of the input shaft 11 and the inner peripheral surface 13b of the first input shaft outer ring 13 so that they can roll freely.

[0043] The second input shaft outer ring 16 is attached to the input shaft support part C1 that supports the input shaft 11. The second input shaft outer ring 16 is provided so as to surround the second input shaft raceway surface K12. The second input shaft outer ring 16 has an outer peripheral surface 16a that is attached to the input shaft support part C1, and an inner peripheral surface 16b that faces the outer peripheral surface of the input shaft 11 (the second input shaft raceway surface K12).

[0044] The second input shaft outer ring 16 has a second input shaft outer ring raceway surface (first outer ring raceway surface) L12 on its inner circumferential surface 16b. The second input shaft outer ring raceway surface L12 is a groove extending in the circumferential direction of the inner circumferential surface 16b of the second input shaft outer ring 16.

[0045] The multiple rolling elements 17 are disposed between the second input shaft raceway surface K12 of the input shaft 11 and the second input shaft outer ring raceway surface L12 of the second input shaft outer ring 16. The rolling elements 17 are spherical balls. The second input shaft retainer 18 holds each of the multiple rolling elements 17 between the outer circumferential surface of the input shaft 11 and the inner circumferential surface 16b of the second input shaft outer ring 16 so that they can roll freely.

[0046] In this manner, the input shaft 11 is rotatably supported at two locations, the location of the first input shaft raceway surface K11 and the location of the second input shaft raceway surface K12. Moreover, the input gear unit 10 in this embodiment does not have a component that functions only as an inner ring of a bearing. In the input gear unit 10 in this embodiment, the input shaft 11 also functions as an inner ring of a bearing.

[0047] In the input gear unit 10 of this embodiment, the first input shaft outer ring 13, the rolling elements 14, and the first input shaft raceway surface K11 of the input shaft 11 form a deep groove ball bearing. Similarly, the second input shaft outer ring 16, the rolling elements 17, and the second input shaft raceway surface K12 of the input shaft 11 form a deep groove ball bearing.

[0048] The input shaft 11 in this embodiment includes a first raceway surface forming portion (raceway surface forming portion) 11a and a first intermediate portion (intermediate portion) 11b. The first raceway surface forming portion 11a is a portion of the input shaft 11 where the first input shaft raceway surface K11 is provided. The first intermediate portion 11b is a portion of the input shaft 11 between the first raceway surface forming portion 11a and a portion where the input shaft output gear 12 is provided. The outer diameter of the first intermediate portion 11b is larger than the outer diameter of the first raceway surface forming portion 11a. That is, the connection portion between the first raceway surface forming portion 11a and the first intermediate portion 11b is a step portion. The step height D1, which is the difference between the radius of the first intermediate portion 11b and the radius of the first raceway surface forming portion 11a, may be equal to or greater than a predetermined height.

[0049] Similarly, the input shaft 11 in this embodiment includes a second raceway surface forming portion (raceway surface forming portion) 11c and a second intermediate portion (intermediate portion) 11d. The second raceway surface forming portion 11c is a portion of the input shaft 11 where the second input shaft raceway surface K12 is provided. The second intermediate portion 11d is a portion of the input shaft 11 between the second raceway surface forming portion 11c and a portion where the input shaft output gear 12 is provided. The outer diameter of the second intermediate portion 11d is larger than the outer diameter of the second raceway surface forming portion 11c. That is, the connection portion between the second raceway surface forming portion 11c and the second intermediate portion 11d is a step portion. The step height D1, which is the difference between the radius of the second intermediate portion 11d and the radius of the second raceway surface forming portion 11c, may be equal to or greater than a predetermined height.

[0050] A gap of a predetermined reference length D2 or more is provided between the first input shaft outer ring 13 and the first intermediate portion 11b in the axial direction (extension direction) of the input shaft 11. Similarly, a gap of a predetermined reference length D2 or more is provided between the second input shaft outer ring 16 and the second intermediate portion 11d in the axial direction of the input shaft 11.

[0051] The first input shaft retainer 15 protrudes outward from an end of the first input shaft outer ring 13 in the axial direction of the input shaft 11. In this embodiment, the first input shaft retainer 15 protrudes from one of both end portions of the first input shaft outer ring 13 in the axial direction of the input shaft 11, the end portion being on the opposite side to the input shaft output gear 12 side. The protrusion amount D3 of the first input shaft retainer 15 is equal to or less than a predetermined reference protrusion amount.

[0052] Similarly, the second input shaft retainer 18 protrudes outward from the end of the second input shaft outer ring 16 in the axial direction of the input shaft 11. In this embodiment, the second input shaft retainer 18 protrudes from one of both end portions of the second input shaft outer ring 16 in the axial direction of the input shaft 11, the end portion being opposite the input shaft output gear 12 side. The protrusion amount D3 of the second input shaft retainer 18 is equal to or smaller than a predetermined reference protrusion amount.

[0053] As shown in FIG. 3, the axial shape of the input shaft 11 in the groove of the first input shaft raceway surface K11 is an arc shape along the raceway groove virtual circle S1. The first intermediate portion 11b and the input shaft output gear 12 do not interfere with the raceway groove virtual circle S1. Similarly, the axial shape of the input shaft 11 in the groove of the second input shaft raceway surface K12 is an arc shape along the raceway groove virtual circle S2. The second intermediate portion 11d and the input shaft output gear 12 do not interfere with the raceway groove virtual circle S2. In FIG. 3, the rolling elements 14, the first input shaft retainer 15, the rolling elements 17, and the second input shaft retainer 18 are omitted in order to show the raceway groove virtual circles S1 and S2.

[0054] [Counter gear unit configuration] As shown in Fig. 1, power is transmitted to the counter gear unit 20 from the input gear unit 10. In more detail, the counter gear unit 20 includes a counter shaft (second shaft) 21, a counter shaft input gear (second input gear) 22, a counter shaft output gear (second output gear) 23, a first counter shaft outer ring (second outer ring) 24, a plurality of rolling elements (second rolling elements) 25, a first counter shaft holder 26, a second counter shaft outer ring (second outer ring) 27, a plurality of rolling elements (second rolling elements) 28, and a second counter shaft holder 29, as shown in Fig. 4.

[0055] Power is transmitted to the countershaft 21 from the input gear unit 10 via a countershaft input gear 22. The rotation axis A2 of the countershaft 21 and the rotation axis A1 of the input shaft 11 are parallel to each other (see FIG. 1). The countershaft 21 has a first countershaft raceway surface (second shaft raceway surface) K21 and a second countershaft raceway surface (second shaft raceway surface) K22 on its outer circumferential surface.

[0056] The first countershaft raceway surface K21 is provided on the outer circumferential surface near one end of the countershaft 21. The first countershaft raceway surface K21 has a truncated cone shape with a diameter decreasing toward one end of the countershaft 21. The second countershaft raceway surface K22 is provided on the outer circumferential surface near the other end of the countershaft 21. The second countershaft raceway surface K22 has a truncated cone shape with a diameter decreasing toward the other end of the countershaft 21.

[0057] The countershaft input gear 22 is provided on the countershaft 21 and rotates integrally with the countershaft 21. The countershaft input gear 22 is provided at a position between the first countershaft raceway surface K21 and the second countershaft raceway surface K22. The countershaft input gear 22 meshes with the input shaft output gear 12 of the input gear unit 10. As a result, power is transmitted to the countershaft 21 from the input gear unit 10 via the countershaft input gear 22.

[0058] In this embodiment, the countershaft input gear 22 is provided as a separate member from the countershaft 21. The countershaft 21 and the countershaft input gear 22 are connected, for example, by a spline. In this case, for example, the countershaft input gear 22 may be prevented from coming off the countershaft 21 by a nut 22a.

[0059] The number of teeth provided on the counter shaft input gear 22 is greater than the number of teeth provided on the input shaft output gear 12 of the input gear unit 10. Therefore, when power is transmitted from the input gear unit 10 to the counter gear unit 20, the rotation speed is reduced.

[0060] The countershaft output gear 23 is provided on the countershaft 21 and rotates integrally with the countershaft 21. The countershaft output gear 23 is provided at a position between the countershaft input gear 22 and the second countershaft raceway surface K22. In this embodiment, the countershaft output gear 23 is provided integrally with the countershaft 21. The countershaft output gear 23 outputs power to the differential gear unit 30.

[0061] The first countershaft outer ring 24 is attached to a countershaft support part (second support part) C2 that supports the countershaft 21. The countershaft support part C2 is, for example, a part of a housing that houses the input gear unit 10 and the like. The first countershaft outer ring 24 is provided so as to surround the first countershaft raceway surface K21. The first countershaft outer ring 24 has an outer peripheral surface 24a that is attached to the countershaft support part C2. The first countershaft outer ring 24 has an inner peripheral surface that is provided with a first countershaft outer ring raceway surface (second outer ring raceway surface) L21 that faces the first countershaft raceway surface K21. The first countershaft outer ring raceway surface L21 has a truncated cone shape that decreases in diameter toward one end side of the countershaft 21.

[0062] The rolling elements 25 are disposed between the first countershaft raceway surface K21 of the countershaft 21 and the first countershaft outer ring raceway surface L21 of the first countershaft outer ring 24. The rolling elements 25 are tapered rollers. The first countershaft cage 26 holds each of the rolling elements 25 between the first countershaft raceway surface K21 of the countershaft 21 and the first countershaft outer ring raceway surface L21 of the first countershaft outer ring 24 so that they can roll freely.

[0063] The countershaft 21 has a first countershaft small flange portion (second small flange portion) 21a provided adjacent to the small diameter side end portion of the first countershaft raceway surface K21, and a first countershaft large flange portion 21b provided adjacent to the large diameter side end portion of the first countershaft raceway surface K21.

[0064] The second countershaft outer ring 27 is attached to the countershaft support part (second support part) C2 that supports the countershaft 21. The second countershaft outer ring 27 is provided so as to surround the second countershaft raceway surface K22. The second countershaft outer ring 27 has an outer peripheral surface 27a that is attached to the countershaft support part C2. The second countershaft outer ring 27 has an inner peripheral surface that is provided with a second countershaft outer ring raceway surface (second outer ring raceway surface) L22 that faces the second countershaft raceway surface K22. The second countershaft outer ring raceway surface L22 has a truncated cone shape that decreases in diameter toward the other end of the countershaft 21.

[0065] The plurality of rolling elements 28 are disposed between the second countershaft raceway surface K22 of the countershaft 21 and the second countershaft outer ring raceway surface L22 of the second countershaft outer ring 27. The rolling elements 28 are tapered rollers. The second countershaft cage 29 holds each of the plurality of rolling elements 28 between the second countershaft raceway surface K22 of the countershaft 21 and the second countershaft outer ring raceway surface L22 of the second countershaft outer ring 27 so that they can roll freely.

[0066] The countershaft 21 has a second countershaft small flange portion 21c provided adjacent to the small diameter side end portion of the second countershaft raceway surface K22, and a second countershaft large flange portion 21d provided adjacent to the large diameter side end portion of the second countershaft raceway surface K22.

[0067] In this way, the countershaft 21 is rotatably supported at two locations, the first countershaft raceway surface K21 and the second countershaft raceway surface K22. The counter gear unit 20 in this embodiment does not have a component that functions only as an inner ring of the bearing. In the counter gear unit 20 in this embodiment, the countershaft 21 also functions as an inner ring of the bearing.

[0068] In the counter gear unit 20 of this embodiment, the first countershaft outer ring 24, the rolling elements 25, and the first countershaft raceway surface K21 of the countershaft 21 form a tapered roller bearing. Similarly, the second countershaft outer ring 27, the rolling elements 28, and the second countershaft raceway surface K22 of the countershaft 21 form a tapered roller bearing.

[0069] [Differential gear unit configuration] 1, the differential gear unit 30 receives power from the counter gear unit 20. In more detail, the differential gear unit 30 includes a differential case 31, a differential input (third input gear) gear 32, a differential mechanism 33, a first differential outer ring (third outer ring) 34, a plurality of rolling elements (third rolling elements) 35, a first differential cage 36, a second differential outer ring (third outer ring) 37, a plurality of rolling elements (third rolling elements) 38, and a second differential cage 39, as shown in FIG.

[0070] Power is transmitted to the differential case 31 from the counter gear unit 20 via a differential input gear 32. A rotation axis A3 of the differential case 31 and a rotation axis A2 of the counter gear unit 20 are parallel to each other (see FIG. 1). The differential case 31 has an accommodation space therein for accommodating a differential mechanism 33. The differential case 31 has a first differential raceway surface (third shaft raceway surface) K31 and a second differential raceway surface (third shaft raceway surface) K32 on its outer circumferential surface.

[0071] The first differential raceway surface K31 is provided on the outer circumferential surface near one end of the differential case 31 in the direction of the rotation axis A3. The first differential raceway surface K31 has a truncated cone shape with a diameter decreasing toward one end of the differential case 31. The second differential raceway surface K32 is provided on the outer circumferential surface near the other end of the differential case 31 in the direction of the rotation axis A3. The second differential raceway surface K32 has a truncated cone shape with a diameter decreasing toward the other end of the differential case 31.

[0072] The differential input gear 32 is provided in the differential case 31 and rotates integrally with the differential case 31. The differential case 31 is provided at a position between the first differential raceway surface K31 and the second differential raceway surface K32. The differential input gear 32 meshes with the counter shaft output gear 23 of the counter gear unit 20. As a result, power is transmitted from the counter gear unit 20 to the differential case 31 via the differential input gear 32. In this embodiment, the differential input gear 32 is provided integrally with the differential case 31.

[0073] The number of teeth provided on the differential input gear 32 is greater than the number of teeth provided on the counter shaft output gear 23 of the counter gear unit 20. Therefore, the rotation speed is reduced when power is transmitted from the counter gear unit 20 to the differential gear unit 30.

[0074] The differential mechanism 33 is provided inside the differential case 31. The differential mechanism 33 is, for example, a differential mechanism of a vehicle differential gear unit including a pinion gear and a side gear. Various well-known mechanisms can be used as the differential mechanism 33. The differential case 31 is provided with a first plug-in port h1 and a second plug-in port h2 at both ends of the differential case 31 in the direction of the rotation axis A3. The differential mechanism 33 transmits driving force to a drive shaft or the like inserted from the first plug-in port h1 and the second plug-in port h2. The first plug-in port h1 is located inside the first differential raceway surface K31 that extends in an annular shape. The second plug-in port h2 is located inside the second differential raceway surface K32 that extends in an annular shape.

[0075] The first differential outer ring 34 is attached to a differential support part (third support part) C3 that supports the differential case 31. The differential support part C3 is, for example, a part of a housing that houses the input gear unit 10 and the like. The first differential outer ring 34 is provided so as to surround the first differential raceway surface K31. The first differential outer ring 34 has an outer peripheral surface 34a that is attached to the differential support part C3. The first differential outer ring 34 has an inner peripheral surface that is provided with a first differential outer ring raceway surface (third outer ring raceway surface) L31 that faces the first differential raceway surface K31. The first differential outer ring raceway surface L31 has a truncated cone shape that decreases in diameter toward one end side of the differential case 31.

[0076] The multiple rolling elements 35 are disposed between the first differential raceway surface K31 of the differential case 31 and the first differential outer ring raceway surface L31 of the first differential outer ring 34. The rolling elements 35 are tapered rollers. The first differential cage 36 holds each of the multiple rolling elements 35 between the first differential raceway surface K31 of the differential case 31 and the first differential outer ring raceway surface L31 of the first differential outer ring 34 so that they can roll freely.

[0077] In addition, the differential case 31 has a first differential small flange portion 31a provided adjacent to the small diameter side end of the first differential track surface K31, and a first differential large flange portion 31b provided adjacent to the large diameter side end of the first differential track surface K31.

[0078] The second differential outer ring 37 is attached to the differential support part C3 that supports the differential case 31. The second differential outer ring 37 is provided so as to surround the second differential raceway surface K32. The second differential outer ring 37 has an outer peripheral surface 37a that is attached to the differential support part C3. The second differential outer ring 37 has an inner peripheral surface that is provided with a second differential outer ring raceway surface (third outer ring raceway surface) L32 that faces the second differential raceway surface K32. The second differential outer ring raceway surface L32 has a truncated cone shape that decreases in diameter toward the other end of the differential case 31.

[0079] The multiple rolling elements 38 are disposed between the second differential raceway surface K32 of the differential case 31 and the second differential outer ring raceway surface L32 of the second differential outer ring 37. The rolling elements 38 are tapered rollers. The second differential cage 39 holds each of the multiple rolling elements 38 between the second differential raceway surface K32 of the differential case 31 and the second differential outer ring raceway surface L32 of the second differential outer ring 37 so that they can roll freely.

[0080] In addition, the differential case 31 has a second differential small flange portion (third small flange portion) 31c provided adjacent to the small diameter side end portion of the second differential track surface K32, and a second differential large flange portion 31d provided adjacent to the large diameter side end portion of the second differential track surface K32.

[0081] In this way, the differential case 31 is rotatably supported at two locations, the first differential raceway surface K31 and the second differential raceway surface K32. The differential gear unit 30 in this embodiment does not have a component that functions only as an inner ring of the bearing. In the differential gear unit 30 in this embodiment, the differential case 31 also functions as an inner ring of the bearing.

[0082] In the differential gear unit 30 of this embodiment, the first differential outer ring 34, the rolling elements 35, and the first differential raceway surface K31 of the differential case 31 form a tapered roller bearing. Similarly, the second differential outer ring 37, the rolling elements 38, and the second differential raceway surface K32 of the differential case 31 form a tapered roller bearing.

[0083] [Drive unit configuration] As shown in Fig. 1, the drive unit 40 constitutes an electric motor unit that serves as a drive source for the vehicle. More specifically, the drive unit 40 includes a motor rotor (drive mechanism) 41, a rotor shaft (drive shaft) 42, a first rotor shaft outer ring (fourth outer ring) 43, a plurality of rolling elements (fourth rolling elements) 44, a first rotor shaft holder 45, a second rotor shaft outer ring (fourth outer ring) 46, a plurality of rolling elements (fourth rolling elements) 47, and a second rotor shaft holder 48, as shown in Fig. 6.

[0084] The motor rotor 41 constitutes a rotor of an electric motor. Although not shown, the drive unit 40 includes components such as magnets that constitute an electric motor as a drive mechanism. The drive unit 40 may also include electronic components such as an inverter.

[0085] The rotor shaft 42 is provided at the center of the motor rotor 41. The rotor shaft 42 is rotated by the motor rotor 41. The rotor shaft 42 serves as an output shaft for the driving force of the drive unit 40. The rotor shaft 42 is connected to the input shaft 11 of the input gear unit 10. The rotation axis A4 of the rotor shaft 42 and the rotation axis A1 of the input shaft 11 are coaxial.

[0086] Here, a spline 42s is formed on the inner circumferential surface of the rotor shaft 42 at the end connected to the input shaft 11. The spline 42s of the rotor shaft 42 and the spline 11s of the input shaft 11 are spline-coupled to connect the rotor shaft 42 and the input shaft 11. The rotor shaft 42 also has a first rotor shaft raceway surface (fourth shaft raceway surface) K41 and a second rotor shaft raceway surface (fourth shaft raceway surface) K42 on its outer circumferential surface.

[0087] The first rotor shaft raceway surface K41 is provided on the outer circumferential surface of the rotor shaft 42 near the end connected to the input shaft 11. The second rotor shaft raceway surface K42 is provided on the outer circumferential surface of the rotor shaft 42 near the end opposite to the first rotor shaft raceway surface K41. The first rotor shaft raceway surface K41 and the second rotor shaft raceway surface K42 are grooves extending in the circumferential direction of the outer circumferential surface of the rotor shaft 42.

[0088] The first rotor shaft outer ring 43 is attached to a rotor shaft support part (fourth support part) C4 that supports the rotor shaft 42. The rotor shaft support part C4 is, for example, a part of a housing that houses the input gear unit 10 and the like. The first rotor shaft outer ring 43 is provided so as to surround the first rotor shaft raceway surface K41. The first rotor shaft outer ring 43 has an outer peripheral surface 43a attached to the rotor shaft support part C4 and an inner peripheral surface 43b facing the outer peripheral surface of the rotor shaft 42 (the first rotor shaft raceway surface K41).

[0089] The first rotor shaft outer ring 43 has a first rotor shaft outer ring raceway surface (fourth outer ring raceway surface) L41 on an inner circumferential surface 43b. The first rotor shaft outer ring raceway surface L41 is a groove extending in the circumferential direction of the inner circumferential surface 43b of the first rotor shaft outer ring 43.

[0090] The multiple rolling elements 44 are disposed between the first rotor shaft raceway surface K41 of the rotor shaft 42 and the first rotor shaft outer ring raceway surface L41 of the first rotor shaft outer ring 43. The rolling elements 44 are spherical balls. The first rotor shaft retainer 45 holds each of the multiple rolling elements 44 between the outer circumferential surface of the rotor shaft 42 and the inner circumferential surface 43b of the first rotor shaft outer ring 43 so that they can roll freely.

[0091] The second rotor shaft outer ring 46 is attached to a rotor shaft support part C4 that supports the rotor shaft 42. The second rotor shaft outer ring 46 is provided so as to surround the second rotor shaft raceway surface K42. The second rotor shaft outer ring 46 has an outer peripheral surface 46a that is attached to the rotor shaft support part C4, and an inner peripheral surface 46b that faces the outer peripheral surface of the rotor shaft 42 (the second rotor shaft raceway surface K42).

[0092] The second rotor shaft outer ring 46 has a second rotor shaft outer ring raceway surface (fourth outer ring raceway surface) L42 on its inner circumferential surface 46b. The second rotor shaft outer ring raceway surface L42 is a groove extending in the circumferential direction of the inner circumferential surface 46b of the second rotor shaft outer ring 46.

[0093] The multiple rolling elements 47 are disposed between the second rotor shaft raceway surface K42 of the rotor shaft 42 and the second rotor shaft outer ring raceway surface L42 of the second rotor shaft outer ring 46. The rolling elements 47 are spherical balls. The second rotor shaft retainer 48 holds each of the multiple rolling elements 47 between the outer circumferential surface of the rotor shaft 42 and the inner circumferential surface 46b of the second rotor shaft outer ring 46 so that they can roll freely.

[0094] In this way, the rotor shaft 42 is rotatably supported at two locations, the first rotor shaft raceway surface K41 and the second rotor shaft raceway surface K42. Furthermore, the drive unit 40 in this embodiment does not have a component that functions only as an inner ring of the bearing. In the drive unit 40 in this embodiment, the rotor shaft 42 also functions as the inner ring of the bearing.

[0095] In the drive unit 40 of this embodiment, the first rotor shaft outer ring 43, the plurality of rolling elements 44, and the first rotor shaft raceway surface K41 of the rotor shaft 42 form a tapered roller bearing. Similarly, the second rotor shaft outer ring 46, the rolling elements 47, and the second rotor shaft raceway surface K42 of the rotor shaft 42 form a tapered roller bearing.

[0096] [Number of gear teeth and rolling elements] The number of teeth and the number of rolling elements of each of the above-mentioned gears are all prime numbers. Specifically, the number of teeth of the input shaft output gear 12 and the number of rolling elements 14 and 17 in the input gear unit 10, the number of teeth of the counter shaft input gear 22 and the counter shaft output gear 23 in the counter gear unit 20, the number of teeth of the differential input gear 32 in the differential gear unit 30, the number of rolling elements 35 and 38, and the number of rolling elements 44 and 47 in the drive unit 40 are all prime numbers.

[0097] However, the number of teeth and the number of rolling elements of each of these gears do not have to be prime numbers. At least one of the number of teeth and the number of rolling elements of each of these gears may be a prime number. Specifically, for example, at least one of the number of teeth of the input shaft output gear 12 in the input gear unit 10 and the number of rolling elements 14 and 17 may be a prime number. Also, for example, at least one of the number of teeth of the input shaft output gear 12 in the input gear unit 10 and the number of rolling elements 14 and 17, the number of teeth of the counter shaft input gear 22 and the counter shaft output gear 23 in the counter gear unit 20 and the number of rolling elements 25 and 28 may be a prime number.

[0098] Alternatively, for example, at least any one of the number of teeth of the input shaft output gear 12 in the input gear unit 10, the number of rolling elements 14 and 17, the number of teeth of the counter shaft input gear 22 and the counter shaft output gear 23 in the counter gear unit 20, the number of rolling elements 25 and 28, the number of teeth of the differential input gear 32 in the differential gear unit 30, and the number of rolling elements 35 and 38 may be a prime number. Also, for example, at least any one of the number of teeth of the input shaft output gear 12 in the input gear unit 10, the number of rolling elements 14 and 17, and the number of rolling elements 44 and 47 in the drive unit 40 may be a prime number.

[0099] As described above, in the reduction gear 1, the input shaft 11, which is a rotating shaft connected to the rotor shaft 42 of the drive unit 40, is rotatably supported by the input shaft support part C1 via the rolling elements 14 and the first input shaft outer ring 13 and via the rolling elements 17 and the second input shaft outer ring 16. That is, the input shaft 11 also functions as the inner ring of the bearing. In this way, the reduction gear 1 can reduce the number of parts of the mechanism that supports the input shaft 11, and can suppress a decrease in the support accuracy of the input shaft 11 due to variations in part accuracy and the like. In addition, in the reduction gear 1, since the input shaft 11 also functions as the inner ring of the bearing, the radial size around the bearing can be reduced compared to a case where an inner ring is separately provided. And, in the reduction gear 1, the inclination of the input shaft 11 can also be suppressed. Therefore, in the reduction gear 1, the input shaft 11, which is connected to the rotor shaft 42 of the drive unit 40 and rotates at the highest speed, can be rotatably supported.

[0100] In the input shaft 11 of the reducer 1, the outer diameter of the first intermediate portion 11b is larger than the outer diameter of the first raceway surface forming portion 11a where the first input shaft raceway surface K11 is provided. Similarly, the outer diameter of the second intermediate portion 11d is larger than the outer diameter of the second raceway surface forming portion 11c where the second input shaft raceway surface K12 is provided. In this case, the reducer 1 can improve the rigidity of the input shaft 11 around the input shaft output gear 12.

[0101] As shown in FIG. 3, the first input shaft raceway surface K11 provided on the input shaft 11 has an arc shape along the raceway groove virtual circle S1. The first intermediate portion 11b of the input shaft 11 and the input shaft output gear 12 do not interfere with the raceway groove virtual circle S1. Similarly, the second input shaft raceway surface K12 provided on the input shaft 11 has an arc shape along the raceway groove virtual circle S2. The second intermediate portion 11d of the input shaft 11 and the input shaft output gear 12 do not interfere with the raceway groove virtual circle S2. In this case, the reducer 1 can appropriately dispose the rolling elements 14 in the groove that is the first input shaft raceway surface K11 without interfering with the first intermediate portion 11b and the input shaft output gear 12. Furthermore, in the reducer 1, the rolling elements 17 can be appropriately disposed in the groove that is the second input shaft raceway surface K12 without interfering with the second intermediate portion 11d and the input shaft output gear 12.

[0102] In the input shaft 11, a gap of reference length D2 or more is provided between the first intermediate portion 11b and the first input shaft outer ring 13. In this case, even if the rolling element 14 moves in the axial direction of the input shaft 11 during rotation of the input shaft 11, it is possible to prevent the rolling element 14 from interfering with the first intermediate portion 11b. Similarly, in the input shaft 11, a gap of reference length D2 or more is provided between the second intermediate portion 11d and the second input shaft outer ring 16. In this case, even if the rolling element 17 moves in the axial direction of the input shaft 11 during rotation of the input shaft 11, it is possible to prevent the rolling element 17 from interfering with the second intermediate portion 11d.

[0103] In the input gear unit 10, the first input shaft retainer 15 protrudes outward from the end of the first input shaft outer ring 13. Similarly, the second input shaft retainer 18 protrudes outward from the end of the second input shaft outer ring 16. Here, a general bearing including an inner ring, an outer ring, a plurality of rolling elements, and a retainer for retaining the rolling elements is carried in a pre-assembled state and assembled to the reducer. In such a bearing, the retainer is configured not to protrude from the inner ring and the outer ring in the axial direction so that the retainer is not damaged by external impact or the like during transportation. However, the reducer 1 in this embodiment does not have the configuration of a general bearing in which the inner ring, the outer ring, a plurality of rolling elements, and the retainer are assembled, and is not subject to structural constraints for preventing damage to the retainer during transportation. As a result, this reducer 1 can reduce the constraints imposed on the first input shaft retainer 15 and the second input shaft retainer 18, thereby increasing the design freedom of the first input shaft retainer 15 and the second input shaft retainer 18.

[0104] The reducer 1 also includes a counter gear unit 20. In the reducer 1, the counter shaft 21 to which power is transmitted from the input gear unit 10 is rotatably supported by the counter shaft support part C2 via the rolling elements 25 and the first counter shaft outer ring 24 and via the rolling elements 28 and the second counter shaft outer ring 27. In other words, the counter shaft 21 also functions as the inner ring of the bearing. In this way, the reducer 1 can reduce the number of parts of the mechanism supporting the counter shaft 21, and can suppress a decrease in the support accuracy of the counter shaft 21 due to variations in part accuracy and the like. Therefore, in the reducer 1, the counter shaft 21 to which power is transmitted from the input gear unit 10 can be stably and rotatably supported in the same manner as the input shaft 11.

[0105] The reducer 1 also includes a differential gear unit 30. In the reducer 1, the differential case 31 to which power is transmitted from the counter gear unit 20 is rotatably supported by the differential support part C3 via the rolling elements 35 and the first differential outer ring 34 and via the rolling elements 38 and the second differential outer ring 37. That is, the differential case 31 also functions as the inner ring of the bearing. In this way, the reducer 1 can reduce the number of parts of the mechanism that supports the differential case 31, and can suppress a decrease in the support accuracy of the differential case 31 due to variations in part accuracy and the like. Therefore, in the reducer 1, the differential case 31 to which power is transmitted from the counter gear unit 20 can be stably and rotatably supported, similar to the input shaft 11 and the like.

[0106] The reducer 1 also includes a drive unit 40. In the reducer 1, the rotor shaft 42 of the drive unit 40 is rotatably supported by the rotor shaft support part C4 via the rolling elements 44 and the first rotor shaft outer ring 43, and via the rolling elements 47 and the second rotor shaft outer ring 46. That is, the rotor shaft 42 also functions as the inner ring of the bearing. In this way, the reducer 1 can reduce the number of parts of the mechanism that supports the rotor shaft 42, and can suppress a decrease in the support accuracy of the rotor shaft 42 due to variations in part accuracy and the like. Therefore, in the reducer 1, like the input shaft 11 and the like, even when the reducer 1 includes the drive unit 40, the rotor shaft 42 of the drive unit 40 can be stably and rotatably supported.

[0107] The number of teeth of each of the above-mentioned gears and the number of rolling elements are all prime numbers, or at least some of them are prime numbers. In this case, the reducer 1 can reduce vibration caused by resonance of each part.

[0108] [Modification of input gear unit] Next, modified examples of the reducer 1 according to this embodiment will be described. The following will focus on the differences from the above embodiment. First, various modified examples of the input gear unit 10 will be described.

[0109] [First modified example of input gear unit] 7, the input gear unit (first shaft unit) 10A according to the first modification is configured such that the bearing and the input shaft are integrated only on one side, unlike the input gear unit 10 according to the embodiment. More specifically, the input gear unit 10A includes an input shaft (first shaft) 11A, an input shaft output gear 12, a second input shaft outer ring 16, rolling elements 17, a second input shaft retainer 18, and a bearing 100.

[0110] The bearing 100 is a deep groove ball bearing. The bearing 100 has an outer ring 101, an inner ring 102, a plurality of rolling elements 103, and a cage 104. The rolling elements 103 are spherical balls. The rolling elements 103 are disposed between an outer ring raceway surface of the outer ring 101 and an inner ring raceway surface of the inner ring 102. The cage 104 holds each of the plurality of rolling elements 103 so that they can roll freely. The inner ring 102 is attached to the outer peripheral surface near the end opposite to the end of the first raceway surface forming portion 11a on which the spline 11s is provided. The outer peripheral surface of the outer ring 101 is attached to the input shaft support portion C1 described above.

[0111] Even in this case, the portion of the input shaft 11A where the second input shaft raceway surface K12 is provided also functions as an inner ring, so that the input gear unit 10A can stably support the input shaft 11A for rotation.

[0112] [Second modified example of input gear unit] As shown in Fig. 8, the input gear unit (first shaft unit) 10B according to the second modification is characterized by the shapes of the first input shaft raceway surface (first shaft raceway surface) K11B and the second input shaft raceway surface (first shaft raceway surface) K12B. More specifically, the input gear unit 10B includes an input shaft (first shaft) 11B instead of the input shaft 11 of the input gear unit 10 according to the embodiment shown in Fig. 2.

[0113] The input shaft 11B has a first input shaft raceway surface K11B and a second input shaft raceway surface K12B on its outer circumferential surface. The first input shaft raceway surface K11B and the second input shaft raceway surface K12B are grooves extending in the circumferential direction of the outer circumferential surface of the input shaft 11B.

[0114] In the grooves constituting the first input shaft raceway surface K11B, a pair of groove edges extending in the circumferential direction of the outer circumferential surface of the input shaft 11B are referred to as groove edge F11a and groove edge F11b. The groove edge F11b is an edge closer to the input shaft output gear 12 than the groove edge F11a. The groove edge F11b closer to the input shaft output gear 12 has a larger diameter than the groove edge F11a. In other words, in the first input shaft raceway surface K11B, the shoulder portion (groove edge F11b) closer to the input shaft output gear 12 is higher than the other shoulder portion (groove edge F11a).

[0115] In addition, in the grooves constituting the second input shaft raceway surface K12B, a pair of groove edges extending in the circumferential direction of the outer circumferential surface of the input shaft 11B are referred to as groove edge portion F12a and groove edge portion F12b. The groove edge portion F12b is an edge portion closer to the input shaft output gear 12 than the groove edge portion F12a. The groove edge portion F12b closer to the input shaft output gear 12 has a larger diameter than the groove edge portion F12a. In other words, in the second input shaft raceway surface K12B, the shoulder portion (groove edge portion F12b) closer to the input shaft output gear 12 is higher than the other shoulder portion (groove edge portion F12a).

[0116] In this way, even when the rolling elements 14 and 17 are subjected to an axial load from the input shaft 11B, the input gear unit 10B can prevent the rolling elements 14 and 17 from climbing up the grooves (the first input shaft raceway surface K11B and the second input shaft raceway surface K12B) by making the height of the groove edge portion on the side receiving the load (the height of the groove edge portions F11b and F12b) higher than the other.

[0117] [Third modified input gear unit] As shown in FIG. 9, an input gear unit (first shaft unit) 10C according to the third modified example has an input shaft (first shaft) 11C instead of the input shaft 11 of the input gear unit 10 according to the embodiment shown in FIG.

[0118] A first oil passage M11 extending along the axial direction of the input shaft 11C is provided inside the input shaft 11C. Lubricating oil is supplied to the first oil passage M11 from a hydraulic supply source (not shown). Furthermore, the input shaft 11C is provided with a first oil hole M12 communicating with the first oil passage M11 and the outer circumferential surface of the input shaft 11C. Although only one first oil hole M12 is shown in FIG. 9, two or more first oil holes M12 may be provided at different positions in the rotation direction of the input shaft 11C. At least a part of the opening M12a of the first oil hole M12 on the outer circumferential surface of the input shaft 11C faces the inner circumferential surface 13b of the first input shaft outer ring 13 in the radial direction of the input shaft 11C. That is, the lubricating oil can be supplied from the first oil passage M11 to the periphery of the rolling element 14 through the opening M12a of the first oil hole M12.

[0119] As described above, at least a part of the opening M12a of the first oil hole M12 faces the inner peripheral surface 13b of the first input shaft outer ring 13. This improves the performance of supplying lubricating oil to the first input shaft raceway surface K11 and the first input shaft outer ring raceway surface L11 in the input gear unit 10C. Note that, in the input gear unit 10C according to the third modified example, an oil hole may be provided on the rolling element 17 side to supply lubricating oil. Alternatively, a configuration may be used in which lubricating oil is supplied to both the rolling element 14 side and the rolling element 17 side.

[0120] [Fourth modified input gear unit] As shown in FIG. 10, the input gear unit (first shaft unit) 10D according to the fourth modification is obtained by changing the position of the first oil hole M12 of the input gear unit 10C according to the third modification shown in FIG. 9. More specifically, the input gear unit 10D according to the fourth modification has a first oil hole M13 provided in the input shaft (first shaft) 11D instead of the first oil hole M12 of the input gear unit 10C according to the third modification. In addition, in the first oil passage M11 provided in the input shaft 11D, the lubricating oil flows from the end on the side where the first input shaft raceway surface K11 is formed to the end on the side where the spline 11s is provided. That is, in the first oil passage M11, the first input shaft raceway surface K11 side is the upstream side in the flow direction of the lubricating oil, and the side where the spline 11s is provided is the downstream side in the flow direction of the lubricating oil.

[0121] The first oil hole M13 extends along the radial direction of the input shaft 11D. Although only one first oil hole M13 is shown in Fig. 10, two or more first oil holes M13 may be provided at different positions in the rotation direction of the input shaft 11D. The first oil hole M13 is provided upstream of the first input shaft raceway surface K11 in the flow direction of the lubricating oil (oil flow direction) in the first oil passage M11 in the axial direction (extension direction) of the input shaft 11D.

[0122] In this case, in the input gear unit 10D, the supply path of the lubricating oil to the first input shaft raceway surface K11 etc. can be shortened, and the lubricating oil can be supplied more appropriately. At least a part of the opening M13a of the first oil hole M13 on the outer peripheral surface of the input shaft 11D may face the inner peripheral surface 13b of the first input shaft outer ring 13. In this case, the lubricating oil can be supplied more efficiently around the first input shaft raceway surface K11.

[0123] [Fifth modified example of input gear unit] As shown in Fig. 11, an input gear unit (first shaft unit) 10E according to the fifth modified example is obtained by adding O-rings 111 and 112 to the input gear unit 10D according to the fourth modified example shown in Fig. 10. More specifically, the input gear unit 10E includes an input shaft (first shaft) 11E instead of the input shaft 11D according to the fourth embodiment, and further includes O-rings 111 and 112.

[0124] The input shaft 11E does not include the first oil hole M13 as compared to the input shaft 11D according to the fourth embodiment. The O-ring 111 is disposed between the outer peripheral surface 13a of the first input shaft outer ring 13 and the input shaft support portion C1 so as to surround the first input shaft outer ring 13. In this modification, two O-rings 111 are provided. The O-ring 112 is disposed between the outer peripheral surface 16a of the second input shaft outer ring 16 and the input shaft support portion C1 so as to surround the second input shaft outer ring 16. In this modification, two O-rings 112 are provided.

[0125] The O-rings 111 and 112 are made of an elastically deformable material (e.g., rubber, resin, etc.). In this modification, the O-ring 111 is disposed in a groove provided in the outer peripheral surface 13a of the first input shaft outer ring 13. Similarly, in this modification, the O-ring 112 is disposed in a groove provided in the outer peripheral surface 16a of the second input shaft outer ring 16.

[0126] In this case, in the input gear unit 10E, the occurrence of creep caused by the first input shaft outer ring 13 and the second input shaft outer ring 16 receiving a rotational load or whirling can be suppressed.

[0127] As another method for suppressing the occurrence of creep, instead of the O-ring 111 provided on the outer peripheral surface 13a of the first input shaft outer ring 13, a coating may be provided on the outer peripheral surface of the first input shaft outer ring. This coating has a surface with lower friction than the outer peripheral surface of the first input shaft outer ring. This coating may be, for example, a low-friction solid lubricant coating. This solid lubricant coating is a film containing a solid lubricant. Even when a low-friction coating is provided in this way, the occurrence of creep caused by the first input shaft outer ring receiving a rotational load or whirling can be suppressed. Similarly, a low-friction coating may be provided on the second input shaft outer ring 16 side on which the O-ring 112 is provided.

[0128] [Modification of counter gear unit] Next, various modified examples of the counter gear unit 20 will be described.

[0129] [First modified example of counter gear unit] As shown in Fig. 12, the counter gear unit (second shaft unit) 20A according to the first modification is different from the counter gear unit 20 according to the embodiment in that the bearing and the counter shaft are integrated only on one side. Moreover, even on the side where the counter shaft and the bearing are integrated, the counter shaft does not have a small flange. More specifically, the counter gear unit 20A includes a counter shaft (second shaft) 21A, a counter shaft input gear 22, a counter shaft output gear 23, a first counter shaft outer ring 24, a rolling element 25, a first counter shaft retainer 26, and a bearing 200.

[0130] The bearing 200 is a tapered roller bearing. The bearing 200 has an outer ring 201, an inner ring 202, a plurality of rolling elements 203, and a cage 204. The rolling elements 203 are tapered rollers. The rolling elements 203 are disposed between an outer ring raceway surface of the outer ring 201 and an inner ring raceway surface of the inner ring 202. The cage 204 holds each of the plurality of rolling elements 203 so that they can roll freely. The inner ring 202 is attached to the outer peripheral surface of the countershaft 21A near the end portion on the side closer to the countershaft output gear 23. The outer peripheral surface of the outer ring 201 is attached to the countershaft support part C2 described above.

[0131] Moreover, the end of the countershaft 21A opposite to the end on the side where the bearing 200 is attached is rotatably supported on the countershaft support part C2 via the above-mentioned rolling elements 25 and the first countershaft outer ring 24. In this modification, no small flange part is provided at a position adjacent to the small diameter side end part of the truncated cone shaped first countershaft raceway surface (second countershaft raceway surface) K21.

[0132] Even in such a case, the countershaft 21A also functions as an inner ring at the portion of the countershaft 21A where the first countershaft raceway surface K21 is provided. Therefore, the counter gear unit 20A can stably support the countershaft 21A for rotation. Moreover, the countershaft 21A does not have a small flange at the end where the first countershaft raceway surface K21 is provided. Therefore, the counter gear unit 20A can improve the ease of assembly of each part.

[0133] [Second modified example of counter gear unit] As shown in FIG. 13, the counter gear unit (second shaft unit) 20B of the second modified example has a counter shaft (second shaft) 21B instead of the counter shaft 21 of the counter gear unit 20 of the embodiment shown in FIG. 4.

[0134] A second oil passage M21 extending along the axial direction of the countershaft 21B is provided inside the countershaft 21B. Lubricating oil is supplied to the second oil passage M21 from a hydraulic supply source (not shown). The lubricating oil flows through the second oil passage M21 provided in the countershaft 21B from an end portion on the side where the first countershaft raceway surface K21 is formed to an end portion on the side where the second countershaft raceway surface K22 is formed. That is, in the second oil passage M21, the first countershaft raceway surface K21 side is the upstream side in the flow direction of the lubricating oil, and the second countershaft raceway surface K22 side is the downstream side in the flow direction of the lubricating oil.

[0135] Further, the countershaft 21B is provided with a second oil hole M22 that communicates with the second oil passage M21 and the outer circumferential surface of the first countershaft small flange (second small flange) 21a provided on the countershaft 21B. That is, the lubricating oil can be supplied from the second oil passage M21 to the periphery of the rolling element 25 through the opening M22a of the second oil hole M22. Although only one second oil hole M22 is shown in FIG. 13, two or more second oil holes M22 may be provided at different positions in the rotation direction of the countershaft 21B. Moreover, at least a part of the opening M22a of the second oil hole M22 that opens into the first countershaft small flange 21a faces the first countershaft outer ring raceway surface L21 of the first countershaft outer ring 24 in the radial direction of the countershaft 21B.

[0136] In this case, the counter gear unit 20B rotatably supports the counter shaft 21B by a tapered roller bearing structure. The counter gear unit 20B can supply lubricating oil from the outer circumferential surface of the first counter shaft small flange portion 21a to the first counter shaft raceway surface K21, etc., and can supply lubricating oil more effectively by the pumping action of the tapered roller bearing.

[0137] As described above, at least a part of the opening M22a of the second oil hole M22 faces the first countershaft outer ring raceway surface L21 of the first countershaft outer ring 24. This improves the performance of supplying lubricating oil to the first countershaft raceway surface K21 and the like in the counter gear unit 20B. Note that in the counter gear unit 20B according to the second modified example, an oil hole may be provided in the second countershaft small flange portion 21c on the rolling element 28 side to supply lubricating oil. Alternatively, a configuration may be used in which lubricating oil is supplied to both the rolling element 25 side and the rolling element 28 side.

[0138] [Third modified example of counter gear unit] 14, a counter gear unit (second shaft unit) 20C according to a third modified example rotatably supports a counter shaft (second shaft) 21C by a deep groove ball bearing structure. More specifically, the counter gear unit 20C includes a counter shaft 21C, a counter shaft input gear 22, a counter shaft output gear 23, a first counter shaft outer ring (second outer ring) 210, a plurality of rolling elements (second rolling elements) 211, a first counter shaft holder 212, a second counter shaft outer ring (second outer ring) 220, a plurality of rolling elements (second rolling elements) 221, and a second counter shaft holder 222.

[0139] On the outer circumferential surface of the countershaft 21C, a first countershaft raceway surface (second shaft raceway surface) K21C and a second countershaft raceway surface (second shaft raceway surface) K22C are provided, instead of the first countershaft raceway surface K21 and the second countershaft raceway surface K22 according to the embodiment. The first countershaft raceway surface K21C and the second countershaft raceway surface K22C are grooves extending in the circumferential direction of the outer circumferential surface of the countershaft 21C.

[0140] The first countershaft outer ring 210 is disposed so as to surround the first countershaft raceway surface K21C. The outer peripheral surface of the first countershaft outer ring 210 is attached to the countershaft support part C2 described above. The inner peripheral surface of the first countershaft outer ring 210 is provided with a first countershaft outer ring raceway surface (second outer ring raceway surface) L21C. The first countershaft outer ring raceway surface L21C is a groove extending in the circumferential direction of the first countershaft outer ring 210. The rolling elements 211 are balls having a spherical shape. The rolling elements 211 are disposed between the first countershaft raceway surface K21C of the countershaft 21C and the first countershaft outer ring raceway surface L21C of the first countershaft outer ring 210. The first countershaft retainer 212 holds each of the multiple rolling elements 211 so as to be freely rotatable. In this manner, the first countershaft outer ring 210, the rolling elements 211, and the first countershaft raceway surface K21C of the countershaft 21C form a deep groove ball bearing.

[0141] Similarly, the second countershaft outer ring 220 is disposed so as to surround the second countershaft raceway surface K22C. The outer peripheral surface of the second countershaft outer ring 220 is attached to the countershaft support part C2 described above. The inner peripheral surface of the second countershaft outer ring 220 is provided with a second countershaft outer ring raceway surface (second outer ring raceway surface) L22C. The second countershaft outer ring raceway surface L22C is a groove extending in the circumferential direction of the second countershaft outer ring 220. The rolling elements 221 are balls having a spherical shape. The rolling elements 221 are disposed between the second countershaft raceway surface K22C of the countershaft 21C and the second countershaft outer ring raceway surface L22C of the second countershaft outer ring 220. The second countershaft retainer 222 holds each of the multiple rolling elements 221 so as to be freely rotatable. In this manner, the second countershaft outer ring 220, the rolling elements 221, and the second countershaft raceway surface K22C of the countershaft 21C form a deep groove ball bearing.

[0142] A second oil passage M21 extending along the axial direction of the countershaft 21C is provided inside the countershaft 21C. The countershaft 21C is also provided with a second oil hole M22 communicating with the second oil passage M21 and the outer circumferential surface of the countershaft 21C. Although only one second oil hole M22 is shown in FIG. 14, two or more second oil holes M22 may be provided at different positions in the rotational direction of the countershaft 21C. An opening M22a of the second oil hole M22 that opens into the outer circumferential surface of the countershaft 21C is adjacent to the first countershaft raceway surface K21C.

[0143] Here, the opening M22a of the second oil hole M22 being adjacent to the first countershaft raceway surface K21C includes a state in which the opening edge of the opening M22a is in contact with the first countershaft raceway surface K21C. Also, the opening M22a of the second oil hole M22 being adjacent to the first countershaft raceway surface K21C includes a state in which the opening edge of the opening M22a is adjacent to the first countershaft raceway surface K21C with a predetermined gap therebetween. In other words, the opening M22a of the second oil hole M22 being adjacent to the first countershaft raceway surface K21C may be in a state in which lubricating oil can be supplied from the opening M22a of the second oil hole M22 to the periphery of the first countershaft raceway surface K21C.

[0144] In this way, the counter gear unit 20C is provided with the second oil hole M22, and thus the lubricant can be appropriately supplied to the first countershaft raceway surface K21C and the like through the second oil hole M22. In addition, in this modification, the countershaft 21C is supported by a deep groove ball bearing. In this case, the countershaft 21C can be rotated with a smaller amount of lubricant than when it is supported by a tapered roller bearing.

[0145] Furthermore, at least a part of the opening M22a of the second oil hole M22 may face the inner circumferential surface of the first countershaft outer ring 210 in the radial direction of the countershaft 21C. In this case, the counter gear unit 20C can improve the performance of supplying lubricating oil to the first countershaft raceway surface K21C and the like.

[0146] [Differential gear unit modification] Next, various modified examples of the differential gear unit will be described.

[0147] [First modified example of differential gear unit] As shown in Fig. 15, the differential gear unit 30A according to the first modification is different from the differential gear unit 30 according to the embodiment in that the bearing and the differential case are integrated only on one side. In addition, even on the side where the differential case and the bearing are integrated, the differential case does not have a small flange. More specifically, the differential gear unit 30A includes a differential case 31A, a differential input gear 32, a differential mechanism 33, a second differential outer ring 37, rolling elements 38, a second differential cage 39, and a bearing 300.

[0148] The bearing 300 is a tapered roller bearing. The bearing 300 has an outer ring 301, an inner ring 302, a plurality of rolling elements 303, and a cage 304. The rolling elements 303 are tapered rollers. The rolling elements 303 are disposed between an outer ring raceway surface of the outer ring 301 and an inner ring raceway surface of the inner ring 302. The cage 304 holds each of the plurality of rolling elements 303 so that they can roll freely. The inner ring 302 is attached to the outer peripheral surface of the end (the end on the side where the first insertion port h1 is provided) on the opposite side to the side where the second differential raceway surface K32 is provided in the differential case 31A. The outer peripheral surface of the outer ring 301 is attached to the above-mentioned differential support part C3.

[0149] In addition, in the differential case 31A, the end opposite to the end on the side where the bearing 300 is attached is rotatably supported on the differential support part C3 via the above-mentioned rolling elements 38 and the second differential outer ring 37. In this modified example, no small flange part is provided at a position adjacent to the small diameter side end part of the truncated cone shaped second differential raceway surface (third shaft raceway surface) K32.

[0150] Even in such a case, the differential case 31A also functions as an inner ring at the portion where the second differential raceway surface K32 is provided in the differential case 31A. Therefore, the differential gear unit 30A can stably support the differential case 31A so that it can rotate. Also, the differential case 31A does not have a small flange at the end where the second differential raceway surface K32 is provided. Therefore, the differential gear unit 30A can improve the ease of assembly of each part.

[0151] [Second modified example of differential gear unit] As shown in FIG. 16, a differential gear unit 30B according to the second modified example includes a differential case 31B instead of the differential case 31 of the differential gear unit 30 according to the embodiment shown in FIG.

[0152] The differential case 31B is provided with a third oil hole M32 that communicates with the outer circumferential surface of the second differential small flange portion (third small flange portion) 31c adjacent to the first differential raceway surface K31 and the second insertion port h2. Although only one third oil hole M32 is shown in FIG. 16, two or more third oil holes M32 may be provided at different positions in the rotational direction of the differential case 31B. At least a part of an opening M32a of the third oil hole M32 that opens into the outer circumferential surface of the second differential small flange portion 31c faces the second differential outer ring raceway surface L32 of the second differential outer ring 37 in the radial direction of the second differential outer ring 37.

[0153] Here, lubricating oil flows through the accommodation space that accommodates the differential mechanism 33 inside the differential case 31B. The lubricating oil also enters the inner part of the second plug h2. In other words, the second plug h2 (the gap between the inner wall surface of the second plug h2 and the outer circumferential surface of the drive shaft inserted into the second plug h2) functions as an oil passage (third oil passage) for the lubricating oil. The lubricating oil is supplied from the second plug h2, which functions as an oil passage, to the vicinity of the first countershaft raceway surface K21 via the third oil hole M32.

[0154] In this case, the differential gear unit 30B rotatably supports the differential case 31B by a tapered roller bearing structure. The differential gear unit 30B can supply lubricating oil from the outer circumferential surface of the second differential small flange portion 31c to the first differential raceway surface K31 and the like, and can supply lubricating oil more effectively by the pumping action of the tapered roller bearing.

[0155] As described above, at least a part of the opening M32a of the third oil hole M32 faces the second differential outer ring raceway surface L32 of the second differential outer ring 37. This improves the performance of supplying lubricating oil to the second differential outer ring raceway surface L32 and the like in the differential gear unit 30B. Note that in the differential gear unit 30B according to the second modified example, an oil hole may be provided in the first differential small flange portion 31a on the rolling element 35 side to supply lubricating oil. Alternatively, a configuration may be used in which lubricating oil is supplied to both the rolling element 35 side and the rolling element 38 side.

[0156] [Modification of the drive unit] Next, various modified examples of the drive unit will be described.

[0157] [First modified example of the drive unit] 17, unlike the drive unit 40 according to the embodiment, the drive unit 40A according to the first modification has a configuration in which one end of the rotor shaft is supported from the inner peripheral side. More specifically, the drive unit 40A includes a motor rotor 41, a rotor shaft (drive shaft) 42A, a first rotor shaft outer ring 43, a rolling element 44, a first rotor shaft holder 45, a plurality of rolling elements 47A, a second rotor shaft holder 48A, and a second rotor shaft inner ring 49A.

[0158] The rotor shaft 42A is connected to the input shaft 11 in the same manner as the rotor shaft 42 according to the embodiment. The rotor shaft 42A has a first rotor shaft raceway surface K41 and a second rotor shaft raceway surface (fourth rotor shaft raceway surface) K42A. The second rotor shaft raceway surface K42A is provided on the inner circumferential surface of the rotor shaft 42 near the end opposite to the first rotor shaft raceway surface K41. The second rotor shaft raceway surface K42A is a groove extending in the circumferential direction of the inner circumferential surface of the rotor shaft 42A.

[0159] The second rotor shaft inner ring 49A is attached to the outer periphery of the rotor shaft support part (fourth support part) C4A that supports the rotor shaft 42A from the inside of the second rotor shaft raceway surface K42A. The second rotor shaft inner ring 49A is provided on the inside of the second rotor shaft raceway surface K42A so that the outer periphery of the second rotor shaft inner ring 49A faces the second rotor shaft raceway surface K42A. The second rotor shaft inner ring 49A has a second rotor shaft inner ring raceway surface (fourth inner ring raceway surface) L43A on its outer periphery. The second rotor shaft inner ring raceway surface L43A is a groove extending in the circumferential direction of the inner periphery of the second rotor shaft inner ring 49A.

[0160] The rolling elements 47A are disposed between the second rotor shaft raceway surface K42A of the rotor shaft 42A and the second rotor shaft inner ring raceway surface L43A of the second rotor shaft inner ring 49A. The rolling elements 47A are spherical balls. The second rotor shaft retainer 48A holds each of the rolling elements 47A between the inner peripheral surface of the rotor shaft 42A and the inner peripheral surface of the second rotor shaft inner ring 49A so that they can roll freely.

[0161] In this manner, the rotor shaft 42A is rotatably supported at two locations, the location of the first rotor shaft raceway surface K41 and the location of the second rotor shaft raceway surface K42A. Furthermore, the drive unit 40A in this modified example does not have a component that functions only as an outer ring of a bearing at the end on the side where the second rotor shaft raceway surface K42A is provided. At the end on the side where the second rotor shaft raceway surface K42A is provided in the rotor shaft 42A in this modified example, the rotor shaft 42A also functions as an outer ring of a bearing.

[0162] In the drive unit 40A of this modification, a deep groove ball bearing is formed by the first rotor shaft outer ring 43, the plurality of rolling elements 44, and the first rotor shaft raceway surface K41 of the rotor shaft 42. Similarly, a deep groove ball bearing is formed by the second rotor shaft inner ring 49A, the rolling elements 47A, and the second rotor shaft raceway surface K42A of the rotor shaft 42A.

[0163] As described above, in this modification, one end of the rotor shaft 42A is rotatably supported by the rotor shaft support C4 via the rolling elements 44 and the first rotor shaft outer ring 43. That is, one end of the rotor shaft 42A also functions as the outer ring of the bearing. The other end of the rotor shaft 42A is rotatably supported by the rotor shaft support C4A via the rolling elements 47A and the second rotor shaft inner ring 49A. The other end of the rotor shaft 42A also functions as the outer ring of the bearing. In this way, the drive unit 40A can reduce the number of parts of the mechanism that supports the rotor shaft 42A, and can suppress a decrease in the support accuracy of the rotor shaft 42A due to variations in part accuracy and the like. Therefore, the drive unit 40 can stably support the rotor shaft 42A so that it can rotate.

[0164] In addition, since the rolling body 47A and the second rotor shaft inner ring 49A, etc. are located inside the rotor shaft 42A, it is possible to achieve space saving and low torque while maintaining ease of assembly when assembling the motor rotor 41, etc. to the rotor shaft 42A.

[0165] [Second modified example of the drive unit] As shown in FIG. 18, a drive unit 40B according to the second modification includes a rotor shaft (drive shaft) 42B instead of the rotor shaft 42 of the drive unit 40 according to the embodiment shown in FIG.

[0166] A fourth oil passage M41 extending along the axial direction of the rotor shaft 42B is provided inside the rotor shaft 42B. Lubricating oil is supplied to the fourth oil passage M41 from a hydraulic supply source (not shown). Furthermore, the rotor shaft 42B is provided with a fourth oil hole M42 communicating with the fourth oil passage M41 and the outer circumferential surface of the rotor shaft 42B. Although only one fourth oil hole M42 is shown in FIG. 18, two or more fourth oil holes M42 may be provided at different positions in the rotation direction of the rotor shaft 42B. An opening M42a of the fourth oil hole M42 opening on the outer circumferential surface of the rotor shaft 42B is adjacent to the second rotor shaft raceway surface (fourth shaft raceway surface) K42. That is, the fourth oil passage M41 can be supplied to the periphery of the rolling element 47 through the opening M42a of the fourth oil hole M42.

[0167] Here, the opening M42a of the fourth oil hole M42 being adjacent to the second rotor shaft raceway surface K42 includes a state in which the opening edge of the opening M42a is in contact with the second rotor shaft raceway surface K42. Also, the opening M42a of the fourth oil hole M42 being adjacent to the second rotor shaft raceway surface K42 includes a state in which the opening edge of the opening M42a is adjacent to the second rotor shaft raceway surface K42 with a predetermined gap therebetween. In other words, the opening M42a of the fourth oil hole M42 being adjacent to the second rotor shaft raceway surface K42 may be in a state in which lubricating oil can be supplied from the opening M42a of the fourth oil hole M42 to the periphery of the second rotor shaft raceway surface K42.

[0168] In this way, by providing the fourth oil hole M42, the drive unit 40B can appropriately supply lubricating oil to the second rotor shaft raceway surface K42 and the like through the fourth oil hole M42. Note that in the drive unit 40B according to the second modified example, an oil hole similar to the fourth oil hole M42 may be provided on the rolling element 44 side to supply lubricating oil. Also, a configuration may be used in which lubricating oil is supplied to both the rolling element 47 side and the rolling element 44 side.

[0169] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. Furthermore, at least a part of the embodiment and various modifications described above may be arbitrarily combined.

[0170] In addition, in the above embodiment and various modified examples, the input gear unit 10 (10A, 10B, 10C, 10D, 10E), the counter gear unit 20 (20A, 20B, 20C), the differential gear unit 30 (30A, 30B), and the drive unit 40 (40A, 40B) are all configured with rotating members such as the input shaft 11 and bearings integrated together, but any one or more of these units may have a rotating member and bearings integrated together. Furthermore, the reducer 1 according to the above embodiment and various modified examples may further include a gear unit having a rotating shaft in addition to the above-mentioned units.

[0171] In the above embodiment and various modified examples, a deep groove ball bearing and a tapered roller bearing have been described as examples of the bearing structure, but other bearing structures, such as an angular ball bearing or a cylindrical roller bearing, may also be used.

[0172] In the above, a reduction gear has been described as the transmission according to the present invention. However, the present invention is not limited to this, and the transmission according to the present invention may be a speed increaser that increases the rotation speed of a drive unit. Even when the transmission according to the present invention is a speed increaser, the same configuration as the configuration of the bearing portion described for the reduction gear 1 can be adopted, except that the conversion ratio of the rotation speed by the gears between each unit is different from that of the reduction gear 1 described above. [Explanation of symbols]

[0173] 1...reduction gear (transmission), 10, 10A, 10B, 10C, 10D, 10E...input gear unit (first shaft unit), 11, 11A, 11B, 11C, 11D, 11E...input shaft (first shaft), 11a...first raceway surface forming portion (raceway surface forming portion), 11b...first intermediate portion (intermediate portion), 11c...second raceway surface forming portion (raceway surface forming portion), 11d...second intermediate portion (intermediate portion), 12...input shaft output gear (first output gear), 13...first input shaft outer ring (first outer ring), 14, 17...rolling body (first rolling body), 15...first input shaft Cage (cage) 16... second input shaft outer ring (first outer ring), 18... second input shaft cage (cage), 20, 20A, 20B, 20C... counter gear unit (second shaft unit), 21, 21A, 21B, 21C... counter shaft (second shaft), 21a... first counter shaft small flange portion (second small flange portion), 22... counter shaft input gear (second input gear), 23... counter shaft output gear (second output gear), 24, 210... first counter shaft outer ring (second outer ring), 27, 220... second counter shaft outer ring (first 2 outer ring), 25, 28, 211, 221... rolling element (second rolling element), 30, 30A, 30B... differential gear unit, 31, 31A, 31B... differential case, 32... differential input gear (third input gear), 33... differential mechanism, 34... first differential outer ring (third outer ring), 35, 38... rolling element (third rolling element), 37... second differential outer ring (third outer ring), 40, 40A, 40B... drive unit, 41... motor rotor (drive mechanism), 42, 42A, 42B... rotor shaft (drive shaft), 43... first rotor shaft outer ring ( 4th outer ring), 44, 47, 47A... rolling element (4th rolling element), 46... second rotor shaft outer ring (4th outer ring), 111, 112... O-ring, A1, A2, A3, A4... rotating shaft, C1... input shaft support part (1st support part), C2... counter shaft support part (2nd support part), C3... differential support part (3rd support part), C4, C4A... rotor shaft support part (4th support part), F11a, F11b, F12a, F12b... groove edge part, h2... second insertion port (3rd oil passage), K11, K11B... first input shaft raceway surface (first shaft raceway surface), K12,K12B…2nd input shaft raceway surface (1st shaft raceway surface), K21, K21C…1st countershaft raceway surface (2nd shaft raceway surface), K22, K22C…2nd countershaft raceway surface (2nd shaft raceway surface), K31…1st differential raceway surface (3rd shaft raceway surface), K32…2nd differential raceway surface (3rd shaft raceway surface), K41…1st rotor shaft raceway surface (4th shaft raceway surface), K42, K42A…2nd rotor shaft raceway surface (4th shaft raceway surface), L11…1st input shaft outer ring raceway surface (1st outer ring raceway surface), L12…2nd input shaft outer ring raceway surface (1st outer ring raceway surface), L21, L21C…1st countershaft outer ring raceway surface (2nd outer ring raceway surface) L22, L22C: second countershaft outer ring raceway surface (second outer ring raceway surface), L31: first differential outer ring raceway surface (third outer ring raceway surface), L32: second differential outer ring raceway surface (third outer ring raceway surface), L41: first rotor shaft outer ring raceway surface (fourth outer ring raceway surface), L42: second rotor shaft outer ring raceway surface (fourth outer ring raceway surface), 4 outer ring raceway surface), L43A... second rotor shaft inner ring raceway surface (fourth inner ring raceway surface), M11... first oil passage, M12, M13... first oil hole, M12a, M13a, M22a, M32a, M42a... opening, M21... second oil passage, M22... second oil hole, M32... third oil hole, M41... fourth oil passage, M42... fourth oil hole, S1, S2... raceway groove imaginary circle.

Claims

1. A first shaft unit is connected to a drive shaft of the drive unit, The first shaft unit includes: a first shaft connected to the drive shaft and having a first shaft raceway on an outer circumferential surface; a first output gear provided on the first shaft and rotating integrally with the first shaft; a first outer ring attached to a first support portion that supports the first shaft and disposed so as to surround the first shaft raceway surface, the first outer ring having a first outer ring raceway surface on an inner circumferential surface; a plurality of first rolling elements disposed between the first shaft raceway surface and the first outer ring raceway surface; having The first rolling element is a ball, the first shaft raceway surface is a groove extending in a circumferential direction of the outer circumferential surface of the first shaft, a groove that constitutes the first shaft raceway surface, and of a pair of groove edge portions extending in a circumferential direction of the outer circumferential surface of the first shaft, the groove edge portion closer to the first output gear has a larger diameter than the other groove edge portion.

2. The first shaft includes an orbital surface forming portion where the first shaft orbital surface is provided, and an intermediate portion between the orbital surface forming portion and the first output gear, The transmission according to claim 1 , wherein an outer diameter of the intermediate portion is larger than an outer diameter of the raceway surface forming portion.

3. a shape of the groove of the first shaft raceway surface in an axial direction of the first shaft is an arc shape along a raceway groove virtual circle, The transmission according to claim 2 , wherein the intermediate portion and the first output gear do not interfere with the raceway groove imaginary circle.

4. The roller bearing further includes a cage that holds each of the plurality of rolling elements so as to be capable of rolling, The transmission according to any one of claims 1 to 3, wherein the cage protrudes outward from an end of the first outer ring in an axial direction of the first shaft.

5. a first oil passage is provided inside the first shaft and extends along an axial direction of the first shaft, Further, a first oil hole is provided in the first shaft, the first oil hole communicating with the first oil passage and an outer peripheral surface of the first shaft, The transmission according to any one of claims 1 to 4, wherein at least a portion of an opening of the first oil hole in the outer peripheral surface of the first shaft faces the inner peripheral surface of the first outer ring in a radial direction of the first shaft.

6. 6. The transmission according to claim 5, wherein the first oil hole extends along a radial direction of the first shaft and is provided upstream of the first shaft raceway surface in an oil flow direction of the first oil passage in the axial direction of the first shaft.

7. The transmission according to any one of claims 1 to 6, wherein an O-ring is provided between an outer circumferential surface of the first outer ring and the first support portion so as to surround the first outer ring.

8. The transmission according to any one of claims 1 to 6, wherein an outer circumferential surface of the first outer ring is provided with a coating having lower friction than the outer circumferential surface of the first outer ring.

9. Further comprising a second shaft unit to which power is transmitted from the first shaft unit, The second shaft unit is a second shaft having a second shaft raceway surface on an outer circumferential surface; a second input gear provided on the second shaft, meshing with the first output gear and rotating integrally with the second shaft; a second output gear provided on the second shaft and rotating integrally with the second shaft; a second outer ring attached to a second support portion that supports the second shaft and disposed so as to surround the second shaft raceway surface, the second outer ring having a second outer ring raceway surface on an inner circumferential surface; a plurality of second rolling elements disposed between the second shaft raceway surface and the second outer ring raceway surface; having The transmission according to any one of claims 1 to 8, wherein the rotation axis of the first shaft and the rotation axis of the second shaft are parallel to each other.

10. the second rolling element is a tapered roller, The second shaft raceway surface has a truncated cone shape, the second shaft further has a second small flange provided adjacent to a small diameter side end of the second shaft raceway surface having a truncated cone shape, a second oil passage is provided inside the second shaft and extends along an axial direction of the second shaft, The transmission according to claim 9 , further comprising a second oil hole provided in the second shaft, the second oil hole communicating with the second oil passage and an outer circumferential surface of the second small flange portion.

11. The second rolling element is a ball, the second shaft raceway surface is a groove extending in a circumferential direction of the outer circumferential surface of the second shaft, a second oil passage is provided inside the second shaft and extends along an axial direction of the second shaft, Further, the second shaft is provided with a second oil hole communicating with the second oil passage and an outer circumferential surface of the second shaft, The transmission according to claim 9 , wherein an opening of the second oil hole that opens into the outer circumferential surface of the second shaft is adjacent to the second shaft raceway surface.

12. the second rolling element is a tapered roller, The second shaft raceway surface has a truncated cone shape, 10. The transmission according to claim 9, wherein the second shaft does not have a small flange portion adjacent to a small diameter end portion of the second shaft raceway surface having a truncated cone shape.

13. Further comprising a differential gear unit to which power is transmitted from the second shaft unit, The differential gear unit includes: a differential case having a third shaft raceway on its outer circumferential surface; a third input gear provided in the differential case, meshing with the second output gear and rotating integrally with the differential case; a differential mechanism provided in the differential case; and a third outer ring attached to a third support portion that supports the differential case and disposed so as to surround the third shaft raceway surface, the third outer ring having a third outer ring raceway surface on an inner circumferential surface; a plurality of third rolling elements disposed between the third shaft raceway surface and the third outer ring raceway surface; having The transmission according to any one of claims 9 to 12, wherein the rotation axis of the second shaft and the rotation axis of the differential case are parallel to each other.

14. the third rolling element is a tapered roller, The third shaft orbital surface has a truncated cone shape, the differential case further includes a third small flange provided adjacent to a small diameter end of the third shaft raceway surface having a truncated cone shape, A third oil passage is provided inside the differential case, The transmission according to claim 13, further comprising a third oil hole provided in the differential case, the third oil passage communicating with an outer circumferential surface of the third small flange portion.

15. the third rolling element is a tapered roller, The third shaft orbital surface has a truncated cone shape, 14. The transmission according to claim 13, wherein the differential case is not provided with a small flange portion adjacent to a small diameter end portion of the third shaft raceway surface having a truncated cone shape.

16. The drive unit is further provided. The drive unit includes: A drive mechanism; a drive shaft having a fourth shaft raceway surface on an outer circumferential surface thereof, the drive shaft being rotationally driven by the drive mechanism and connected to the first shaft; a fourth outer ring attached to a fourth support portion that supports the drive shaft, arranged to surround the fourth shaft raceway surface, and having a fourth outer ring raceway surface on an inner circumferential surface; a plurality of fourth rolling elements disposed between the fourth shaft raceway surface and the fourth outer ring raceway surface; The transmission according to any one of claims 1 to 15, comprising:

17. A fourth oil passage is provided inside the drive shaft and extends along the axial direction of the drive shaft, Further, the drive shaft is provided with a fourth oil hole communicating with the fourth oil passage and an outer peripheral surface of the drive shaft, 17. The transmission according to claim 16, wherein an opening of the fourth oil hole that opens into the outer circumferential surface of the drive shaft is adjacent to the fourth shaft raceway surface.

18. A drive unit and a first axle unit connected to a drive shaft of the drive unit, The first shaft unit includes: a first shaft connected to the drive shaft and having a first shaft raceway on an outer circumferential surface; a first output gear provided on the first shaft and rotating integrally with the first shaft; a first outer ring attached to a first support portion that supports the first shaft and disposed so as to surround the first shaft raceway surface, the first outer ring having a first outer ring raceway surface on an inner circumferential surface; a plurality of first rolling elements disposed between the first shaft raceway surface and the first outer ring raceway surface; having The drive unit includes: A drive mechanism; a drive shaft having a fourth shaft raceway surface on an inner peripheral surface thereof, the drive shaft being rotationally driven by the drive mechanism and connected to the first shaft; a fourth inner ring attached to an outer periphery of a fourth support part that supports the drive shaft from an inside of the fourth shaft raceway surface, the fourth inner ring being disposed inside the fourth shaft raceway surface and having a fourth inner ring raceway surface on an outer periphery thereof; a plurality of fourth rolling elements disposed between the fourth shaft raceway surface and the fourth inner ring raceway surface; A transmission having

19. The transmission according to any one of claims 1 to 8, wherein at least one of the number of teeth of the first output gear and the number of the first rolling elements is a prime number.

20. The transmission according to any one of claims 9 to 12, wherein at least one of the number of teeth of the first output gear, the number of the first rolling bodies, the number of teeth of the second input gear, the number of teeth of the second output gear, and the number of the second rolling bodies is a prime number.

21. The transmission according to any one of claims 13 to 15, wherein at least one of the number of teeth of the first output gear, the number of the first rolling bodies, the number of teeth of the second input gear, the number of teeth of the second output gear, the number of the second rolling bodies, the number of teeth of the third input gear, and the number of the third rolling bodies is a prime number.

22. The transmission according to any one of claims 16 to 18, wherein at least one of the number of teeth of the first output gear, the number of the first rolling bodies, and the number of the fourth rolling bodies is a prime number.

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