JP2013087888A - Differential device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small differential device reduced in sliding portion in a differential device for a vehicle such as a four-wheeler or a three-wheeler.SOLUTION: The device includes: a differential case 20 opened at both ends; a pinion shaft 31 fixed in the differential case 20; a pinion gear 32 rotatable around the pinion shaft 31; a side gear 40 integrally rotating with a drive shaft 401; and a first bearing 50. The side gear 40 has a gear portion 41 meshed with the pinion gear 32 and a boss 42 extending from the gear portion 41 to the axial outside. The first bearing 50 externally contacts with the boss 42 and internally contacts with the differential case 20.

Description

  The present invention relates to a differential device for a vehicle such as a four-wheeled vehicle or a tricycle.

  In a rear-wheel drive or four-wheel drive four-wheeled vehicle, the power from the transmission is transmitted to the center of the left and right rear wheels via a propeller shaft that extends in the front-rear direction at the center in the vehicle width direction. It is transmitted to the reduction gear. More specifically, the power of the propulsion shaft is transmitted through a drive pinion gear to a ring gear (diff ring gear) composed of a hypoid gear while being deflected and decelerated by 90 °, and is transmitted to a differential case integrated with the ring gear.

  In addition, when the four-wheeled vehicle travels on a curve, a difference occurs in the rotation speed between the inner wheel and the outer wheel. Therefore, this is solved by providing a differential device (differential device) in the final reduction gear.

  As shown in FIG. 6, the differential apparatus 500 houses a pinion gear 502 and a side gear 503 in a meshed state in a cast or forged differential case 501 to which the ring gear 601 is fixed. The pinion gear 502 is rotatably held by a pinion shaft 504 fixed to the differential case 501. A drive shaft 602 is splined to the side gear 503.

  When the four-wheeled vehicle travels a curve, the left and right side gears 503 rotate differentially, and the side gears 503 rotate relative to the differential case 501 while meshing with the pinion gears 502. Therefore, it is necessary to prevent the side gear 503 and the differential case 501 from being worn by supplying lubricating oil to the meshing portion of the side gear 503 and the pinion gear 502 and the sliding portion (sliding surface) of the side gear 503 and the differential case 501. A thrust washer 505 (thrust bearing) is provided between the side gear 503 and the differential case 501.

  Further, one end of the drive shaft 602 is inserted into the cylindrical boss portions 506 formed on both ends of the differential case 501 while forming a minimal gap. When the four-wheeled vehicle travels on a curve, the boss portion 506 and the drive shaft 602 rotate relative to each other, so that lubricating oil is supplied to the minimal gap, that is, the sliding portion between the boss portion 506 and the drive shaft 602. It is necessary to prevent the boss 506 and the drive shaft 602 from being worn.

  By the way, in recent years, there is an increasing demand for improvement in fuel consumption. One solution for the final reduction gear is to reduce the lubricating oil in the housing 603 (carrier), that is, to lower the oil level of the lubricating oil reservoir in the housing 603. There is a method for reducing the agitation resistance of the lubricating oil by the ring gear 601. However, if the lubricating oil is simply reduced, the lubricating oil may not be sufficiently supplied to the above-described sliding portion (where the lubricating oil is necessary).

Therefore, there is a configuration in which the lubricating oil that has been scraped up by the rotating ring gear 601 and then flows down the inner wall surface of the housing 603 is collected and supplied to the above-described required lubricating oil via a cast groove.
In this case, as a method for efficiently collecting the lubricating oil, a lubricating oil reservoir is formed above the housing 603 and is formed integrally with the housing 603 or formed as a separate part. A technique has been proposed in which the lubricating oil scooped up in step 1 or the lubricating oil flowing down is collected, and then the lubricating oil is naturally dropped and supplied to the above-described locations where the lubricating oil is required (see Patent Document 1).

  Further, a technology is provided in which a gutter member having a U-shaped cross section called a garter is provided in the housing 603, the splash of the lubricating oil is collected by the gutter member, and the lubricating oil is supplied to the above-described lubricating oil required portions. Has been proposed (see Patent Document 2).

JP 2009-30743 A Japanese Patent No. 3719582

  However, in Patent Documents 1 and 2, since the storage portion and the eaves member are provided above the differential case 501 (rotating body) that rotates in the housing 603, a space for mounting the storage portion or the like is required, and the housing 603 is required. Will become larger.

  Therefore, an object of the present invention is to provide a small differential device with few sliding portions.

  As means for solving the above-mentioned problems, the present invention provides a differential case that is open at both ends, a pinion shaft that is fixed in the differential case, a pinion gear that is rotatable about the pinion shaft, and a drive shaft. The side gear includes a gear portion that meshes with the pinion gear, and a boss portion that extends axially outward from the gear portion. The differential device is circumscribed by a boss portion and inscribed by the differential case.

  According to such a configuration, since the first bearing circumscribes the boss portion and inscribes the differential case, the boss portion (side gear) and the differential case are relatively rotatable by the first bearing. That is, the boss part (side gear) and the differential case are not in direct contact with each other, and there is no sliding part constituted by the boss part and the differential case being in direct contact with each other.

  Thus, since the differential apparatus is a structure which is not provided with the sliding part of a boss | hub part (side gear) and a differential case, there are few places where lubricating oil is required. Thereby, the lubricating oil taken in the differential case can be reduced. Further, since the boss portion (side gear) and the differential case do not slide, they are not seized and worn by sliding.

  Further, since the storage portion for storing the lubricating oil and the flange member for guiding the lubricating oil are not provided, the housing for housing the differential case can be reduced in size. Thereby, a differential apparatus can also be reduced in size and becomes lightweight.

  Further, the differential apparatus includes a housing that houses the differential case, and a second bearing, wherein the boss portion protrudes axially outward from the opening of the differential case, and the first bearing is connected to the differential case. It is preferable that the second bearing is circumscribed to the boss portion on the axially outer side than the opening of the differential case and is inscribed to the housing.

  According to such a configuration, since the second bearing circumscribes the boss portion that is axially outside the opening of the differential case and is inscribed in the housing, the boss portion (side gear) rotates to the housing via the second bearing. Freely supported. That is, the boss part (side gear) and the housing are not in direct contact, and there is no sliding part constituted by the boss part and the housing being in direct contact.

  Thus, since the differential apparatus is a structure which is not provided with the sliding part of a boss | hub part (side gear) and a housing, there are few lubricating oil required locations. Thereby, the supply structure of lubricating oil can be simplified. Further, since the boss portion (side gear) and the housing do not slide, they are not seized and worn by sliding.

  Further, in the differential apparatus, the boss portion includes a large boss portion and a small boss portion having a smaller diameter than the large boss portion from the inner side in the axial direction toward the outer side in the axial direction. One inner ring circumscribes the large boss portion and abuts on an axially outer end surface of the gear portion, and a second inner ring of the second bearing circumscribes the small boss portion and the shaft of the large boss portion. It is preferable to contact the outer end surface in the direction.

According to such a configuration, since the first inner ring of the first bearing circumscribes the large boss portion and abuts against the axially outer end surface of the gear portion, the thrust washer between the first inner ring and the gear portion is reduced. It becomes unnecessary.
Further, since the second inner ring of the second bearing circumscribes the small boss portion and abuts against the axially outer end surface of the large boss portion, a thrust washer between the second inner ring and the large boss portion is not necessary.

  The differential apparatus preferably includes a spacer that holds the first inner ring and the second inner ring at a predetermined interval in the axial direction.

  According to such a configuration, the first inner ring and the second inner ring can be held at a predetermined interval by the spacer.

  ADVANTAGE OF THE INVENTION According to this invention, a small differential apparatus with few sliding parts can be provided.

It is the block diagram which showed typically the final reduction gear apparatus which concerns on this embodiment. It is a schematic explanatory drawing which shows the positional relationship of an input shaft and an output shaft seeing the final reduction gear device which concerns on this embodiment from a vehicle width direction. It is the sectional view on the AA line of the final reduction gear device which concerns on this embodiment shown in FIG. It is an enlarged view of the principal part of the final reduction gear apparatus which concerns on this embodiment shown in FIG. FIG. 3 is a cross-sectional view of the final reduction gear device according to the present embodiment shown in FIG. It is sectional drawing of the differential apparatus which concerns on the past.

  An embodiment of the present invention will be described with reference to FIGS.

≪Configuration of final reduction gear≫
As shown in FIGS. 1 and 3, the final reduction gear 1 according to the present embodiment is mounted on a vehicle, and a reduction gear 100 that reduces the power of an electric motor 301 and left and right drive shafts 401 and 401 (illustrated). The differential device 10 (differential device) that differentially rotates the left and right drive wheels) and the housing 200 that houses the speed reduction device 100 and the differential device 10 are provided.

  That is, here, a configuration in which the power source is the electric motor 301 is illustrated, but other than this, for example, an internal combustion engine (such as a reciprocating engine) or a hydraulic motor may be used. And the structure which the transmission which changes power between the power source and the reduction gear 100 may interpose. Further, the output shaft of the power source and the drive shaft 401 are not parallel, and the power of the propulsion shaft extending in the front-rear direction may be deflected by 90 ° and transmitted through the drive pinion and the ring gear. Furthermore, the type of vehicle is, for example, a four-wheel vehicle or a tricycle, and the drive wheel may be either a front wheel or a rear wheel.

≪Speed reducer≫
The reduction gear 100 rotates integrally with an input shaft 101 connected to the output shaft 302 of the motor 301, an input gear 102 fixed to the input shaft 101, an idler driven gear 103 meshed with the input gear 102, and the idler driven gear 103. An intermediate shaft 104, an idler drive gear 105 fixed to the intermediate shaft 104, and a ring gear 106 (a differential ring gear) that meshes with the idler drive gear 105 and is integrated with a differential case 20 described later.

The power of the motor 301 is decelerated according to the gear ratio between the input gear 102 and the idler driven gear 103 and the gear ratio between the idler drive gear 105 and the ring gear 106 and is input to the differential case 20.
The input gear 102, the idler driven gear 103, the idler drive gear 105, and the ring gear 106 are arranged substantially horizontally in the housing 200 as seen from the vehicle width direction, as shown in FIG.

≪Differential device≫
As shown in FIGS. 4 and 5, the differential apparatus 10 includes a differential case 20 integrally formed with the ring gear 106, a pinion shaft 31, two pinion gears 32, two side gears 40, and two first bearings 50, 50 and two second bearings 60, 60. The differential device 10 has a symmetrical structure with the pinion shaft 31 as the center in the vehicle width direction. The number of pinion gears 32 may be three or more, and the shape of the pinion shaft 31 in the axial view is changed to a cross or the like corresponding to the number of pinion gears 32.

<Differential case>
The differential case 20 has a substantially cylindrical shape extending in the vehicle width direction (left-right direction, axial direction), and both ends thereof are open. The differential case 20 is rotatably accommodated in the housing 200 with the vehicle width axis direction as the rotation axis O.

  A ring gear 106 is provided so as to extend radially outward from the right end portion of the differential case 20. The differential case 20 and the ring gear 106 are integrally cast, and the number of parts is reduced. However, the differential case 20 and the ring gear 106 may be separate parts, and the ring gear 106 may be fastened to the differential case 20 with a bolt.

  As cast iron, for example, spheroidal graphite cast iron whose fatigue strength is improved by heat treatment is used. As a heat treatment method for spheroidal graphite cast iron, for example, those described in Japanese Patent Publication No. 61-19698, Japanese Patent No. 3723706 and the like can be used.

  The hollow portion of the differential case 20 having a substantially cylindrical shape functions as a gear accommodating chamber 21 that accommodates the pinion gear 32 and the side gear 40.

  The differential case 20 is formed with a pair of pinion shaft holes 22 and 22 centering on the rotation axis O in one radial direction (vertical direction in FIG. 4). A pinion shaft 31 is fitted into the pair of pinion shaft holes 22 and 22. The pinion shaft 31 is fixed to the differential case 20 by a pin (not shown) inserted in the vehicle width direction so that it does not fall off from the differential case 20.

  Further, the differential case 20 is formed with discharge holes 23 (also referred to as windows) at predetermined intervals in the circumferential direction (see FIG. 5). And it is designed so that the lubricating oil in the gear housing chamber 21 is discharged out of the differential case 20 through the discharge hole 23 and the lubricating oil in the gear housing chamber 21 becomes an appropriate amount.

<Pinion gear>
A pinion shaft 31 is inserted through the through hole of each pinion gear 32. Each pinion gear 32 is rotatably attached with the pinion shaft 31 as a rotation center.

<Side gear>
Each side gear 40 is rotatably arranged around the rotation axis O on each of the left side and the right side of the pinion shaft 31 and meshes with the two pinion gears 32 and 32. Specifically, each side gear 40 is attached to the differential case 20 via the first bearing 50 so as to be rotatable relative to the inner side in the axial direction of the opening of the differential case 20. It is rotatably attached to the housing 200 via a bearing 60.

  Here, “inner side in the axial direction” means the pinion shaft 31 side (center side) in the vehicle width direction (left-right direction). On the other hand, the “outside in the axial direction” means a side (back side) away from the pinion shaft 31 in the vehicle width direction.

  The side gear 40 has a gear part 41 whose outer shape has a frustoconical shape and gear teeth that mesh with the pinion gear 32 on the outer peripheral surface, and extends axially outward from the back surface of the gear part 41 and has a width from the opening of the differential case 20. And a cylindrical boss portion 42 protruding outward in the direction.

  Such a side gear 40 includes a hollow portion 43 on the rotation axis O line. The hollow portion 43 has an axially inner end portion of the drive shaft 401 inserted therein, and the side gear 40 and the drive shaft 401 are spline-coupled. As a result, the side gear 40 and the drive shaft 401 rotate together.

  The minimal gap formed between the side gear 40 and the drive shaft 401 functions as a lubricating oil supply path from the oil path space 205 toward the gear housing chamber 21 (in the differential case 20).

<Side gear-boss part>
The boss part 42 has a stepped outer peripheral surface, and a large cylindrical part 44 (large boss part) having a large outer diameter and a large cylindrical part having an outer diameter from the center side toward the outer side in the axial direction. And a small cylindrical portion 45 (small boss portion) having a diameter smaller than that of 44. The large cylindrical portion 44 is disposed axially inside (center side) of the opening of the differential case 20, that is, in the differential case 20, and the small cylindrical portion 45 is axially outside of the opening of the differential case 20, that is, Projects from the opening.

<First bearing, second bearing>
The 1st bearing 50 and the 2nd bearing 60 are comprised by a ball bearing and a taper roller bearing, for example. The first bearing 50 and the second bearing 60 are arranged in the order of the first bearing 50 and the second bearing 60 in the axial direction from the center side toward the outer side in the axial direction.

  The first bearing 50 is disposed between the large cylindrical portion 44 of the side gear 40 and the differential case 20, and makes the side gear 40 and the differential case 20 rotatable relative to each other. The second bearing 60 is disposed between the small cylindrical portion 45 of the side gear 40 and the housing 200, and supports the side gear 40 so as to be rotatable with respect to the housing 200.

This will be described more specifically.
The first bearing 50 circumscribes the outer peripheral surface of the large cylindrical portion 44 and also inscribes the inner peripheral surface of the differential case 20. In other words, the first inner ring 51 of the first bearing 50 is fitted on the large cylindrical portion 44, and the first outer ring 52 of the first bearing 50 is fitted on the differential case 20.

  The large cylindrical portion 44 is in contact only with the first inner ring 51 of the first bearing 50 and is not in contact with the first outer ring 52. Further, the differential case 20 is in contact with only the first outer ring 52 of the first bearing 50 and is not in contact with the first inner ring 51. As a result, the first inner ring 51 and the first outer ring 52 are rotatable relative to each other.

  The second bearing 60 circumscribes the outer peripheral surface of the small cylindrical portion 45 and also inscribes the inner peripheral surface of the housing 200. In other words, the second inner ring 61 of the second bearing 60 is fitted on the small cylindrical portion 45, and the second outer ring 62 of the second bearing 60 is fitted on the housing 200.

  The small cylindrical portion 45 is in contact only with the second inner ring 61 of the second bearing 60 and is not in contact with the second outer ring 62. The housing 200 is in contact with only the second outer ring 62 of the second bearing 60 and is not in contact with the second inner ring 61. As a result, the second inner ring 61 and the second outer ring 62 are rotatable relative to each other.

  The second bearing 60 extends inward in the radial direction of the housing 200 in the axial direction and is sandwiched between the ring-shaped extending portion 211 and the large cylindrical portion 44 when viewed in the axial direction. Thereby, the second bearing 60 is restricted in the axial direction. An axially outward thrust load of the large cylindrical portion 44 (side gear 40) is applied to the second outer ring 62 of the second bearing 60.

  In the axial direction, only the second inner ring 61 is in contact with the axially outer end surface of the large cylindrical portion 44. This eliminates the need for a thrust bearing between the second inner ring 61 and the large cylindrical portion 44.

  In the axial direction, a ring-shaped spacer 71 is disposed between the first bearing 50 and the second bearing 60. Thereby, the space | interval of the 1st bearing 50 and the 2nd bearing 60 is hold | maintained with the thickness (axial direction length) of the spacer 71. As shown in FIG. However, the spacer 71 is not limited to a ring shape, and may be appropriately changed to other shapes.

  The first bearing 50 is sandwiched between the spacer 71, the gear portion 41 of the side gear 40, and the step portion 24 of the differential case 20 in the axial direction. Thereby, the first bearing 50 is restricted in the axial direction. An axially outward thrust load of the gear portion 41 (side gear 40) is applied to the housing 200 through the first bearing 50, the spacer 71, and the second bearing 60 in this order.

  Further, in the axial direction, only the first inner ring 51 is in contact with the axially outer end surface (rear surface) of the gear portion 41 in the ring shape. Thereby, a thrust bearing is unnecessary between the first inner ring 51 and the gear portion 41.

≪Housing≫
As shown in FIG. 3, the housing 200 is a case that houses the motor 301, the reduction device 100, and the differential device 10, and has a function of storing lubricating oil at the bottom thereof. In this embodiment, the housing 200 includes a housing body 201 that is open on both sides in the axial direction, a left lid 202 that covers the left opening of the housing body 201, a right lid 203 that covers the right opening of the housing body 201, It has.

  An oil seal 221 (seal member) is interposed between the drive shaft insertion hole 204 formed in the housing 200 and the drive shaft 401.

  In the axial direction, an oil passage space 205 that is a space having a larger diameter than the drive shaft insertion hole 204 is formed between the oil seal 221 and the second bearing 60. A part of the lubricating oil that falls along the inner wall surface of the housing 200 is guided to the oil passage space 205 through a groove (not shown) formed in the axial direction in a portion of the housing 200 that is fitted on the second bearing 60. The oil seal 221 is lubricated or supplied to the gear housing chamber 21 (in the differential case 20) through the gap between the drive shaft 401 and the side gear 40. The lubricating oil supplied to the gear housing chamber 21 lubricates the meshing portion between the pinion gear 32 and the side gear 40.

≪Operation and effect of final reduction gear≫
Next, the operation and effect of the final reduction gear 1 will be described.
The power of the motor 301 is input to the differential device 10 after being decelerated by the reduction gear 100, and when the ring gear 106 and the differential case 20 are rotated, the pinion shaft 31, the side gear 40, the drive shaft 401, and the driving wheels (not shown) are rotated. When the vehicle travels on a curve, the left and right side gears 40 and 40 rotate at different rotational speeds, and the differential device 10 absorbs the difference between the rotational speeds of the left and right drive wheels.

  Further, when the ring gear 106 rotates, the lubricating oil in the lubricating oil pool in the housing 200 is scraped up, and the scraped lubricating oil flows down along the inner wall surface of the housing 200 and returns to the lubricating oil pool. Part of the lubricating oil lubricates the first bearing 50 and the second bearing 60, passes through a groove (not shown) formed in the axial direction in the portion of the housing 200 that fits outside the second bearing 60, and passes through the oil passage. The oil flows into the space 205 and lubricates the oil seal 221.

  Further, a part of the lubricating oil is supplied from the oil passage space 205 to the gear housing chamber 21 through the gap between the drive shaft 401 and the side gear 40, and the meshing portion between the pinion gear 32 and the side gear 40, the pinion gear 32 and the side gear 40. Lubricate the sliding part. Thereafter, the lubricating oil flows out of the differential case 20 through the discharge hole 23 and returns to the lubricating oil reservoir in the housing 200.

  Further, the side gear 40 is rotatable relative to the differential case 20 via the first bearing 50 and is rotatably supported by the housing 200 via the second bearing 60. That is, the side gear 40 and the differential case 20 are Since it does not slide and the differential case 20 and the drive shaft 401 do not slide, wear (burn-in) between the side gear 40 and the differential case 20 and between the differential case 20 and the drive shaft 401 is suppressed, Lubricating oil for lubricating them becomes unnecessary, and the amount of lubricating oil supplied into the differential case 20 can be reduced. As a result, as shown in FIG. 6, generally, a spiral groove formed on the inner peripheral surface of the boss portion 506 of the differential case 501 for supplying lubricating oil into the differential case 501 becomes unnecessary, and the shape of the differential case is simplified. .

  Further, the axially outward thrust load of the side gear 40 is configured to act on the first outer ring 52 of the first bearing 50 and the second outer ring 62 of the second bearing 60, that is, the side gear 40 and the differential case 20. Are not slid and the axially outward thrust load of the side gear 40 does not act on the differential case 20, so that wear (burn-in) between the differential case 20 and the side gear 40 is suppressed. This generally eliminates the need for the thrust washer 505 (thrust bearing, see FIG. 6) provided between the side gear 40 and the differential case 20. Therefore, an oil groove for supplying lubricating oil to the thrust bearing is not necessary.

  In the radial direction, a first bearing 50 and a second bearing 60 are provided between the boss portion 42 (the large cylindrical portion 44 and the small cylindrical portion 45) and the differential case 20 or the housing 200, and the boss portion 42 and the differential case are provided. Since the gap between the boss portion 42 and the differential case 20 does not slide, wear (burn-in) due to relative rotation between the boss portion 42 and the differential case 20 can be suppressed.

  That is, the gap between the drive shaft 401 and the boss portion 42 and the first bearing 50 are interposed between the drive shaft 401 and the differential case 20 in the radial direction, and the conventional drive shaft 602 and differential case shown in FIG. It becomes larger than the gap (distance) with 501. Since the gap between the drive shaft 401 and the boss portion 42 and the first bearing 50 also function as a passage for lubricating oil in the axial direction, the flow rate of lubricating oil in the axial direction increases, and the differential device 10 as a whole. Is easily lubricated well.

In addition, the differential device 10 can be reduced in size and weight because it does not include a storage portion that temporarily stores the lubricating oil or a gutter member that guides the lubricating oil.
Furthermore, since the differential case 20 is not open in the axial direction and closed inside, the differential case 20 can be easily formed by forging or casting in an integrated state with the ring gear 106, and the manufacturing cost can be reduced.

≪Modification≫
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, For example, you may change as follows.

  In the above-described embodiment, the configuration in which the outer peripheral surface of the boss portion 42 is stepped is exemplified, but other configurations, for example, where the outer peripheral surface is not stepped may be used.

  In the above-described embodiment, as illustrated in FIGS. 4 and 5, the configuration in which the second bearing 60 is disposed between the small cylindrical portion 45 and the housing 200 is exemplified. The configuration may be such that the first bearing 50 is disposed between the differential case 20 and the housing 200 on the same cross section as the first bearing 50. In such a configuration, the side gear 40 may not include the small cylindrical portion 45, that is, the boss portion 42 of the side gear 40 may not protrude outward in the axial direction from the opening of the differential case 20.

DESCRIPTION OF SYMBOLS 1 Final reduction device 10 Differential device 20 Differential case 31 Pinion shaft 32 Pinion gear 40 Side gear 41 Gear part 42 Boss part 44 Large cylindrical part (large boss part)
45 Small cylindrical part (small boss part)
50 First bearing 51 First inner ring 60 Second bearing 61 Second inner ring 71 Spacer 200 Housing 401 Drive shaft O Rotating shaft

Claims (4)

A differential case with open ends,
A pinion shaft fixed in the differential case;
A pinion gear that is rotatable about the pinion shaft as a rotation center;
A side gear that rotates integrally with the drive shaft;
A first bearing;
With
The side gear includes a gear portion that meshes with the pinion gear, and a boss portion that extends axially outward from the gear portion,
The first bearing is circumscribed by the boss portion and inscribed by the differential case. A housing for housing the differential case;
A second bearing;
With
The boss portion protrudes outward in the axial direction from the opening of the differential case,
The first bearing circumscribes the boss portion on the inner side in the axial direction than the opening of the differential case,
2. The differential apparatus according to claim 1, wherein the second bearing circumscribes the boss portion that is axially outer than the opening of the differential case and is inscribed in the housing. The boss portion includes a large boss portion and a small boss portion having a smaller diameter than the large boss portion from the axially inner side toward the axially outer side,
The first inner ring of the first bearing circumscribes the large boss portion and abuts on the axially outer end surface of the gear portion,
The differential device according to claim 2, wherein the second inner ring of the second bearing circumscribes the small boss portion and abuts on an axially outer end surface of the large boss portion. The differential apparatus according to claim 3, further comprising a spacer that holds the first inner ring and the second inner ring at predetermined intervals in the axial direction.

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