Vehicle differential device

A vehicle differential device includes a plurality of pinion gear sets. Each of the pinion gear sets includes a first pinion gear configured to mesh with a first outer helical gear and a plurality of second pinion gears configured to mesh with a second outer helical gear. The first pinion gear integrally includes an axially one end side gear portion configured to mesh with the first outer helical gear and an axially other end side gear portion configured to mesh with the second pinion gears. The second pinion gears are configured to mesh with the second outer helical gear at positions separated from each other in a circumferential direction of the second outer helical gear, and the axially other end side gear portion of the first pinion gear is configured to mesh with the second pinion gears at positions radially outward of the second outer helical gear.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2019-050718 filed on Mar. 19, 2019 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a vehicle differential device that can distribute an input drive force to a pair of output shafts while allowing a differential rotation thereof.

2. Description of Related Art

The vehicle differential device that can distribute the input drive force to right and left drive shafts while allowing the differential rotation thereof includes right and left side gears, a plurality of pinion gear sets, a housing, and washers. The right and left side gears rotate integrally with the right and left drive shafts, respectively. Each of the pinion gear sets includes a pair of pinion gears disposed in parallel to the right and left side gears such that the pinion gears mesh with each other. The housing holds each pinion gear of the pinion gear sets such that each pinion gear is rotatable. The washers are disposed to face axial end faces of the right and left side gears. In such a differential device, the right and left side gears and each of the pinion gears have helical teeth (twisted teeth). With the helical teeth of the right and left side gears and the helical teeth of each of the pinion gears meshing with each other, an axial thrust force is generated in the right and left side gears and the respective pinion gears. A frictional resistance force generated by the thrust force limits a differential rotation between the right and left side gears to suppress slipping of wheels of a vehicle, serving as a differential limiting force that makes it possible to improve running performance when the vehicle travels on rough roads, for example.

The applicant of the present disclosure proposes a differential device described in Japanese Unexamined Patent Application Publication No. 2009-197976 (JP 2009-197976 A) as a differential device that can be reduced in size. In the differential device, one pinion gear, of a pair of pinion gears, has a large diameter gear portion and a small diameter gear portion with different pitch circle diameters. The large diameter gear portion meshes with a left side gear of the right and left side gears, and the small diameter gear portion meshes with the other pinion gear on an outer peripheral side of the right side gear. A part of the other pinion gear meshes, in its circumferential direction, with the small diameter gear portion of the one pinion gear, and another part of the other pinion gear meshes, in its circumferential direction, with the right side gear.

SUMMARY

In the differential device described in JP 2009-197976 A, depending on a direction of relative rotation of the right and left side gears, the small diameter gear portion of the one pinion gear receives a radial force toward the right side gear. Therefore, as represented by a reference character 20F shown in FIGS. 2 and 3 of JP 2009-197976 A, a gear support portion needs to be formed in the housing (differential case) such that the gear support portion is interposed between the small diameter gear portion of the one pinion gear and the right side gear. Thus, man-hours for processing the differential case is increased. In addition, the other pinion gear meshes with the small diameter gear portion of the one pinion gear and the right side gear, that is, at two locations, in the circumferential direction. Thus, a large load is imposed on the other pinion gear when transmitting drive force, and this limits the possibility of size reduction of the other pinion gear.

Further, if diameters of the right and left side gears are reduced in order to reduce the size of the device, frictional sliding diameters between the right and left side gears and the washers are reduced, making it difficult to generate a large differential limiting force.

In view of this, the present disclosure provides a vehicle differential device that can be reduced in size while suppressing an increase in processing man-hours and a decrease in the differential limiting force.

A vehicle differential device configured to distribute drive force of a vehicle to a first output shaft and a second output shaft according to a first aspect of the present disclosure includes a first inner helical gear, a first outer helical gear, a second inner helical gear, a second outer helical gear, a housing, a friction member, and a plurality of pinion gear sets. The first inner helical gear is configured to rotate integrally with the first output shaft and has outer peripheral helical teeth on an outer peripheral surface of the first inner helical gear. The first outer helical gear is disposed on an outer periphery of the first inner helical gear and has inner peripheral helical teeth on an inner peripheral surface of the first outer helical gear. The inner peripheral helical teeth of the first outer helical gear are configured to mesh with the outer peripheral helical teeth of the first inner helical gear. The second inner helical gear is configured to rotate integrally with the second output shaft and has outer peripheral helical teeth on an outer peripheral surface of the second inner helical gear. The second outer helical gear is disposed on an outer periphery of the second inner helical gear and has inner peripheral helical teeth on an inner peripheral surface of the second outer helical gear. The inner peripheral helical teeth of the second outer helical gear are configured to mesh with the outer peripheral helical teeth of the second inner helical gear. The housing is configured to accommodate the first outer helical gear and the second outer helical gear. The friction member is disposed between the first outer helical gear and the second outer helical gear. The pinion gear sets are held in the housing. Each of the pinion gear sets includes a first pinion gear configured to mesh with the first outer helical gear, and a plurality of second pinion gears configured to mesh with the second outer helical gear. The first pinion gear integrally includes an axially one end side gear portion configured to mesh with the first outer helical gear, and an axially other end side gear portion configured to mesh with the second pinion gears. The second pinion gears are configured to mesh with the second outer helical gear at positions separated from each other in a circumferential direction of the second outer helical gear. The axially other end side gear portion of the first pinion gear is configured to mesh with the second pinion gears at positions radially outward of the second outer helical gear.

In the vehicle differential device according to the first aspect of the present disclosure, the vehicle differential device can be reduced in size while suppressing the increase in the processing man-hours and the decrease in the differential limiting force.

In the vehicle differential device according to the first aspect of the present disclosure, the housing may have a plurality of recessed fitting portions. The friction member may include a main body portion having an annular plate shape and configured such that an axial end surface of the first outer helical gear and an axial end surface of the second outer helical gear abut against the main body portion, and a plurality of fitting projections projecting radially outward from the main body portion. The fitting projections of the friction member may be fitted onto the recessed fitting portions of the housing so that the friction member is restrained from rotating with respect to the housing.

In the vehicle differential device according to the first aspect of the present disclosure, the friction member may have a plurality of abutting projections projecting radially outward from the main body portion and disposed between the fitting projections. The abutting projections of the friction member may abut against an inner peripheral surface of the housing so that the friction member is positioned with respect to the housing in a radial direction.

In the vehicle differential device according to the first aspect of the present disclosure, a pitch circle diameter of the second outer helical gear may be smaller than a pitch circle diameter of the first outer helical gear.

In the vehicle differential device according to the first aspect of the present disclosure, the first pinion gear and the second pinion gears may have helical teeth on outer peripheral surfaces of the first pinion gear and the second pinion gears. In the first pinion gear, a pitch circle diameter of the axially other end side gear portion may be smaller than a pitch circle diameter of the axially one end side gear portion, and a twist angle of a tooth trace in the axially other end side gear portion may be smaller than a twist angle of a tooth trace in the axially one end side gear portion.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiment

An embodiment of the present disclosure will be described with reference toFIGS. 1 to 4. Note that the embodiment described below is represented as a specific example suitable for implementing the present disclosure. Although some parts exemplify various technical matters that are technically preferable, the technical scope of the present disclosure is not limited to the specific examples.

FIG. 1is a sectional view of a differential device according to the embodiment of the present disclosure.FIG. 2is an exploded perspective view of the differential device.

A differential device1that is mounted on a vehicle is used to distribute a drive force (torque), which is input from a ring gear10, from a driving source of the vehicle, such as an engine, to the first and second output shafts11and12while allowing a differential rotation thereof. InFIG. 1, the ring gear10and the first and second output shafts11and12are indicated by virtual lines (long dashed double-short dashed lines). InFIG. 2, a rotation direction of the differential device1when the vehicle travels forward is indicated by an arrow A1, and the rotation direction of the differential device1when the vehicle moves backward is indicated by an arrow A2. In the embodiment, a case where the first and second output shafts11and12serve as drive shafts respectively connected to the right and left wheels is described. However, the differential device1may be mounted on a four-wheel drive vehicle to be used as a center differential that distributes a drive force to front and rear propeller shafts.

The differential device1includes a housing2, first and second helical gear pairs3and4, a plurality of pinion gear sets5, a center washer6, first and second side washers71and72, and a gap adjusting shim73. The housing2rotates about a rotation axis O together with the ring gear10. The first and second helical gear pairs3and4are accommodated in the housing2and disposed side by side along the rotation axis O. The pinion gear sets5are held in the housing2. The center washer6is disposed between the first helical gear pair3and the second helical gear pair4and serves as a friction member. The first and second side washers71and72are disposed such that the first and second helical gear pairs3and4are sandwiched between the center washer6and the first and second side washers71and72. Hereinafter, a direction parallel to the rotation axis O is referred to as an axial direction. The center washer6and the first and second side washers71and72are restricted from rotating with respect to the housing2.

The first helical gear pair3includes a first inner helical gear31that rotates integrally with the first output shaft11, and a first outer helical gear32that is disposed on an outer periphery of the first inner helical gear31. Spline teeth311for connecting with the first output shaft11are formed on an inner peripheral surface of the first inner helical gear31, and outer peripheral helical teeth312are formed on an outer peripheral surface of the first inner helical gear31. Inner peripheral helical teeth321are formed on an inner peripheral surface of the first outer helical gear32, and outer peripheral helical teeth322are formed on an outer peripheral surface of the first outer helical gear32.

The outer peripheral helical teeth312of the first inner helical gear31and the inner peripheral helical teeth321of the first outer helical gear32mesh with each other. When torque is transmitted from the first outer helical gear32to the first inner helical gear31, an axial thrust force acts on the first inner helical gear31due to the torque transmission, and a thrust force serving as a reaction to the axial thrust force acts on the first outer helical gear32.

As shown inFIG. 2, a twist direction of a tooth trace of the outer peripheral helical teeth322of the first outer helical gear32and a twist direction of a tooth trace of the outer peripheral helical teeth312of the first inner helical gear31are directions that are opposite to each other. In the embodiment, twisted directions of the tooth traces of the inner peripheral helical teeth321of the first outer helical gear32and the outer peripheral helical teeth312of the first inner helical gear31are set such that the first outer helical gear32is pressed toward the center washer6and the first inner helical gear31is pressed toward the first side washer71when the vehicle travels forward. In contrast, when the vehicle moves backward, the first outer helical gear32is pressed toward the first side washer71and the first inner helical gear31is pressed toward the center washer6.

The second helical gear pair4includes a second inner helical gear41that rotates integrally with the second output shaft12, and a second outer helical gear42disposed on an outer periphery of the second inner helical gear41. Spline teeth411for connecting with the second output shaft12are formed on an inner peripheral surface of the second inner helical gear41, and outer peripheral helical teeth412are formed on an outer peripheral surface of the second inner helical gear41. Inner peripheral helical teeth421are formed on an inner peripheral surface of the second outer helical gear42, and outer peripheral helical teeth422are formed on an outer peripheral surface of the second outer helical gear42.

The outer peripheral helical teeth412of the second inner helical gear41and the inner peripheral helical teeth421of the second outer helical gear42mesh with each other. When torque is transmitted from the second outer helical gear42to the second inner helical gear41, an axial thrust force acts on the second inner helical gear41due to the torque transmission, and a thrust force serving as a reaction to the axial thrust force acts on the second outer helical gear42.

A twist direction of a tooth trace of the outer peripheral helical teeth422of the second outer helical gear42and a twist direction of a tooth trace of the outer peripheral helical teeth412of the second inner helical gear41are directions that are opposite to each other. In the embodiment, twisted directions of the tooth traces of the inner peripheral helical teeth421of the second outer helical gear42and the outer peripheral helical teeth412of the second inner helical gear41are set such that the second outer helical gear42is pressed toward the center washer6and the second inner helical gear41is pressed toward the second side washer72when the vehicle travels forward. In contrast, when the vehicle moves backward, the second outer helical gear42is pressed toward the second side washer72, and the second inner helical gear41is pressed toward the center washer6.

A pitch circle diameter P42(seeFIG. 2) of the second outer helical gear42is smaller than a pitch circle diameter P32(seeFIG. 2) of the first outer helical gear32. The twisted direction of the tooth trace of the outer peripheral helical teeth322of the first outer helical gear32and the twisted direction of the tooth trace of the outer peripheral helical teeth422of the second outer helical gear42are inverse to each other.

Each of the pinion gear sets5is constituted by one first pinion gear51and two second pinion gears52. The first pinion gear51integrally includes an axially one end side gear portion511that meshes with the first outer helical gear32and an axially other end side gear portion512that meshes with the two second pinion gears52. The second pinion gears52mesh with the second outer helical gear42while meshing with the axially other end side gear portion512of the first pinion gear51.

The axially other end side gear portion512of the first pinion gear51meshes with the two second pinion gears52at a position radially outward of the second outer helical gear42. A space is formed between the axially other end side gear portion512of the first pinion gear51and the second outer helical gear42, and a support portion for supporting the first pinion gear51is not provided in the space. Tilting of the first pinion gear51in a direction in which the axially other end side gear portion512approaches the second outer helical gear42is suppressed through meshing of the first pinion gear51with the two second pinion gears52. The two second pinion gears52mesh with the second outer helical gear42at positions separated from each other in the circumferential direction of the second outer helical gear42.

FIG. 3is a side view showing the first pinion gear51alone. The first pinion gear51has six helical teeth513formed in a spiral shape on an outer peripheral surface thereof. Each of the helical teeth513has a tooth trace513aand a tooth groove513bformed continuously over the axially one end side gear portion511and the axially other end side gear portion512. A tooth tip surface513cof each of the helical teeth513has a predetermined width in a circumferential direction of the first pinion gear51.

The axially one end side gear portion511is larger in outer diameter than the axially other end side gear portion512. When a pitch circle diameter of the axially one end side gear portion511is referred to as P1, and a pitch circle diameter of the axially other end side gear portion512is referred to as P2, P1is larger than P2, and the ratio of P1to P2(P1/P2) is, for example, 1.05 to 1.15. In an example shown inFIG. 3, the ratio is set to approximately 1.1. When a twist angle of the tooth trace513ain the axially one end side gear portion511is referred to as θ1, and a twist angle of the tooth trace513ain the axially other end side gear portion512is referred to as θ2, θ1is larger than θ2, and the ratio of θ1to θ2is, for example, the same as the ratio of the pitch circle diameters of the axially one end side gear portion511and the axially other end side gear portion512.

In a central portion510of the first pinion gear51, the pitch circle diameter and the twist angle are gradually reduced from those of the axially one end side gear portion511to those of the axially other end side gear portion512, so that stress is not concentrated in the central portion510. Each of the second pinion gears52has six helical teeth521that mesh with the helical teeth513of the axially other end side gear portion512of the first pinion gear51, and a pitch circle diameter of each of the second pinion gears52is equal to P2and the twist angle thereof is equal to θ2.

As described above, the pitch circle diameter P2of the axially other end side gear portion512is smaller than the pitch circle diameter P1of the axially one end side gear portion511, and the twist angle θ2of the tooth trace of the axially other end side gear portion512is smaller than the twist angle θ1of the tooth trace of the axially one end side gear portion511. Thus, a TBR (torque bias ratio) when the first helical gear pair3rotates faster than the second helical gear pair4(for example, when the vehicle turns right) and the TBR when the second helical gear pair4rotates faster than the first helical gear pair3(for example, when the vehicle turns left) are equalized.

That is, in the embodiment, the pitch circle diameter P32of the first outer helical gear32is larger than the pitch circle diameter P42of the second outer helical gear42. If the twist angle θ1of the tooth trace of the axially one end side gear portion511is equal to the twist angle θ2of the tooth trace of the axially other end side gear portion512, a difference in diameter between the first outer helical gear32and the second outer helical gear42causes a deviation in a differential limiting force, which limits differential rotation of the first outer helical gear32and the second outer helical gear42, between right turning and left turning of the vehicle. However, in the embodiment, since the first pinion gear51is constituted as described above, such imbalance in the TBR is suppressed.

The housing2includes a first housing member21having a bottomed cylindrical shape, and a second housing member22fixed to a portion of the first housing member21on its open side. The first housing member21accommodates the first and second helical gear pairs3and4. The first housing member21has bores20serving as pinion gear accommodating spaces for holding the first pinion gear51and the two second pinion gears52. In the embodiment, as shown inFIG. 2, since the differential device1has four pinion gear sets5, four bores20are formed in the first housing member21.

In each of the bores20, a first accommodation space201that accommodates the first pinion gear51and two second accommodation spaces202that accommodate the two second pinion gears52communicate with each other. The two second accommodation spaces202are formed at both ends of each of the bores20in the circumferential direction of the first housing member21. The first accommodation space201is formed between the two second accommodation spaces202. The first accommodation space201and the two second accommodation spaces202are open at the end of the first housing member21on its open side.

When the first pinion gear51rotates inside the bore20, the tooth tip surface513cof the helical teeth513of the first pinion gear51slides on an inner surface201aof the first accommodation space201. Further, when the second pinion gear52rotates inside the bore20, a tooth tip surface521cof the helical teeth521of the second pinion gear52slides on an inner surface202aof the second accommodation space202. Frictional force generated on the tooth tip surfaces513cand521cof the first and second pinion gears51and52, respectively, due to the sliding, serves as the differential limiting force that limits the differential rotation between the first and second output shafts11and12.

The first housing member21integrally includes a cylindrical portion211having four bores20, a bottom portion212projecting inward from one end portion of the cylindrical portion211, a flange portion213projecting outward from the other end portion of the cylindrical portion211, and a tube portion214projecting from a center portion of the bottom portion212in the axial direction and through which the first output shaft11is inserted. An oil groove214afor allowing lubricating oil to flow is formed on an inner surface of the tube portion214.

The first accommodation space201and the second accommodation space202extend from the end portion of the first housing member21on its open side toward the bottom portion212in the axial direction of the cylindrical portion211. An axial length of the second accommodation space202is shorter than an axial length of the first accommodation space201. The bottom portion212has an oil hole212afor circulating the lubricating oil between the first accommodation space201and the outside of the housing2.

At a center portion of the cylindrical portion211of the first housing member21, a first hollow portion203serving as an accommodation space for accommodating the first helical gear pair3, and a second hollow portion204serving as an accommodation space for accommodating the second helical gear pair4are formed side by side in the axial direction. The first hollow portion203is provided on a deep side (the bottom portion212side) of the first housing member21, and the second hollow portion204is provided on the open side of the first housing member21. The first hollow portion203communicates with the first accommodation space201of the bore20and does not communicate with the second accommodation space202. The second hollow portion204communicates with the first accommodation space201and the second accommodation space202of the bore20. The first side washer71is disposed between the first inner helical gear31and the bottom portion212of the first housing member21.

The second housing member22integrally includes an annular plate portion221that closes one end of each of the bores20on the open side of the first housing member21, a flange portion222that abuts against the flange portion213of the first housing member21, and a tube portion223that projects from the annular plate portion221in the axial direction and through which the second output shaft12is inserted. An oil groove223afor allowing the lubricating oil to flow is formed on an inner surface of the tube portion223. The second side washer72is disposed between the second inner helical gear41and the annular plate portion221of the second housing member22. An oil hole221afor circulating the lubricating oil is formed in the annular plate portion221so as to penetrate the annular plate portion221in the axial direction.

The flange portion213of the first housing member21and the flange portion222of the second housing member22are fastened by a plurality of bolts23. The housing2is rotatably supported on a differential carrier by a bearing (not shown) so as to rotate about the rotation axis θ. Bolt insertion holes213aand222aare formed in the flange portions213and222of the first and second housing members21and22, respectively. Shaft portions of bolts100for fixing the ring gear10to the housing members21and22are inserted through the bolt insertion holes213aand222a.

FIG. 4Ais a perspective view showing the center washer6and the first housing member21, andFIG. 4Bis a structural view of the center washer6and the first housing member21as seen in the axial direction.

The center washer6is disposed between the first outer helical gear32and the second outer helical gear42. The center washer6integrally includes an annular plate-shaped main body portion61, a plurality of fitting projections62, and a plurality of abutting projections63. Axial end surfaces32aand42aof the first outer helical gear32and the second outer helical gear42, respectively, abut against the main body portion61when the vehicle travels forward. The fitting projections62and the abutting projections63project radially outward from the main body portion61. The main body portion61has a through hole610at its center portion.

The first housing member21has a plurality of recessed fitting portions215into which the fitting projections62of the center washer6are respectively fitted. In the embodiment, the center washer6has four fitting projections62, and the same number of recessed fitting portions215are formed in the first housing member21. Further, in the embodiment, the recessed fitting portions215are recessed from a bottom surface202bof the second accommodation space202in the axial direction. With the fitting projections62fitted into the recessed fitting portions215, the center washer6is restrained from rotating with respect to the housing2.

The abutting projections63of the center washer6are provided between the fitting projections62in the circumferential direction of the main body portion61. Distal end surfaces63aof the abutting projections63are formed in an arc shape with a curvature matching a curvature of an inner peripheral surface203aof the first hollow portion203of the first housing member21. With the abutting projections63of the center washer6abutting against the inner peripheral surface203aof the first hollow portion203, the center washer6is positioned with respect to the housing2in the radial direction.

Although not shown, the first outer helical gear32and the second outer helical gear42may include an annular projection which protrudes radially inward and which is provided at the end on the center washer61side. In this case, a part of the main body portion61of the center washer6may be disposed between the annular projection of the first outer helical gear32and an annular projection of the second outer helical gear42. Furthermore, although not shown, the inner diameter of the through hole610may be smaller than the inner diameter of a portion of the first outer helical gear32where the annular projection of the first outer helical gear32is formed and the inner diameter of a portion of the second outer helical gear42where the annular projection of the second outer helical gear42is formed. Thereby, for example, compared with the case where the first and second outer helical gears32and42do not have the annular projections, a contact area between the center washer6and the axial end surface32aof the first outer helical gear32, and a contact area between the center washer6and the axial end surface42aof the second outer helical gear42are increased, and wear of the axial end surfaces32aand42ais suppressed.

Operation of Differential Device1

When the housing2is rotated by the drive force input from the ring gear10, the drive force is transmitted to the pinion gear sets5held by the cylindrical portion211of the first housing member21, and is distributed from the first pinion gear51to the first outer helical gear32, and from the second pinion gears52to the second outer helical gear42. Then, the drive force is output from the first outer helical gear32to the first output shaft11via the first inner helical gear31, and from the second outer helical gear42to the second output shaft12via the second inner helical gear41.

When the vehicle travels forward, the first outer helical gear32receives a thrust force toward the center washer6by meshing with the first pinion gear51and also by meshing with the first inner helical gear31. Due to the thrust forces, a frictional force is generated between the axial end surface32aof the first outer helical gear32and the center washer6. Further, the first inner helical gear31receives a thrust force toward the first side washer71by meshing with the first outer helical gear32, and thus a frictional force is generated between the axial end surface31aof the first inner helical gear31and the first side washer71.

Similarly, the second outer helical gear42receives a thrust force toward the center washer6by meshing with the second pinion gears52, and also by meshing with the second inner helical gear41. Due to the thrust forces, a frictional force is generated between the axial end surface42aof the second outer helical gear42and the center washer6. Further, the second inner helical gear41receives a thrust force toward the second side washer72by meshing with the second outer helical gear42, and thus a frictional force is generated between the axial end surface41aof the second inner helical gear41and the second side washer72.

The frictional forces serve as differential limiting forces that limit the differential rotation between the first and second output shafts11and12. Thus, slipping of the right and left wheels is suppressed, and running performance when traveling on rough roads is improved.

Effects of Embodiment

According to the embodiment described above, the differential limiting force when the vehicle travels forward is increased due to the thrust force generated by the meshing between the first outer helical gear32and the first inner helical gear31and the thrust force generated by the meshing between the second outer helical gear42and the second inner helical gear41.

Further, since the first pinion gear51and the second pinion gears52mesh with each other on the outer peripheral side of the second outer helical gear42, the differential device can be reduced in size in the axial direction. In addition, since the two second pinion gears52mesh with the one first pinion gear51, load applied on each second pinion gear52can be reduced during transmission of the drive force, and the second pinion gears52can be reduced in size.

Still further, it is possible to avoid interference between the first pinion gear51and the second outer helical gear42while eliminating the need of a configuration corresponding to a gear support portion20F (a member interposed between the first pinion gear51and the second outer helical gear42) that is required in the differential device described in JP 2009-197976 A. Thus, an increase in man-hours for processing the housing2can be suppressed.

Appendix

Although the present disclosure has been described based on the embodiment, the embodiment does not limit the applicable embodiment according to the claims. It should be noted that all combinations of the features described in the embodiment are not essential for the solution of the present disclosure to the problem.

Further, in order to implement the present disclosure, the embodiment can be modified as appropriate without departing from the spirit of the present disclosure. For example, in the embodiment described above, a case where the differential device1includes the four pinion gear sets5has been described, but the applicable embodiment is not limited thereto. The differential device1may have two, three, or five or more pinion gear sets5.

As long as the interference between the first pinion gear51and the second outer helical gear42can be avoided, the pitch circle diameter of the second outer helical gear42may be the same as the pitch circle diameter of the first outer helical gear32. In addition, the pitch circle diameter of the axially other end side gear portion512of the first pinion gear51may be the same as the pitch circle diameter of the axially one end side gear portion511of the first pinion gear51.