Differential device

1. A differential device comprising:

a differential case including a case main body in which a housing space is formed, and a bearing boss protruding from the case main body, having a cylindrical shape with a case through-hole communicating with the housing space, and being rotatably supported about a first rotation axis;

a side gear housed in the housing space of the differential case and rotatably arranged about the first rotation axis; and

a pinion gear housed in the housing space of the differential case, rotatably arranged about a second rotation axis perpendicular to the first rotation axis, and meshing with the side gear,

wherein an introduction groove for introducing lubricating oil into the housing space of the case main body is formed on an inner peripheral surface of the bearing boss,

wherein an inner surface groove communicating with the introduction groove and extending toward a back surface side of the pinion gear is formed on an inner surface of the case main body,

wherein the inner surface groove includes a first groove portion and a second groove portion positioned radially outward from the first groove portion in the radial direction of the case main body, and

wherein a shape of at least a part of the first groove portion is a shape over which the lubricating oil is harder to climb during vehicle forward movement as compared with the shape of the second groove portion.

2. The differential device according to claim 1 ,

wherein an inner wall surface at the rear side of at least a part of the first groove portion in a forward rotational direction, which is a rotational direction of the differential case during the vehicle forward movement, is steeper than an inner wall surface at the rear side of the second groove portion in the forward rotational direction.

3. The differential device according to claim 1 ,

wherein the inner surface groove has a third groove portion positioned radially inward from the first groove portion,

wherein a shape of at least a part of the third groove portion is a shape over which the lubricating oil is easier to climb during the vehicle forward movement as compared with the shape of the first groove portion, and

wherein the third groove portion is covered with a back surface of the side gear.

4. The differential device according to claim 3 ,

wherein an inner wall surface at a rear side of at least a part of the third groove portion in a forward rotational direction, which is the rotational direction of the differential case during the vehicle forward movement, is inclined more gently than an inner wall surface at the rear side of the first groove portion in the forward rotational direction.

5. The differential device according to claim 1 ,

wherein the second groove portion is covered with the back surface of the pinion gear.

6. The differential device according to claim 1 ,

wherein the first groove portion is positioned between a back surface of the side gear and the back surface of the pinion gear.

7. The differential device according to claim 2 ,

wherein the inner surface groove has a third groove portion positioned radially inward from the first groove portion,

wherein a shape of at least a part of the third groove portion is a shape over which the lubricating oil is easier to climb during the vehicle forward movement as compared with the shape of the first groove portion, and

wherein the third groove portion is covered with a back surface of the side gear.

8. The differential device according to claim 2 ,

wherein the second groove portion is covered with the back surface of the pinion gear.

9. The differential device according to claim 3 ,

wherein the second groove portion is covered with the back surface of the pinion gear.

10. The differential device according to claim 2 ,

wherein the first groove portion is positioned between a back surface of the side gear and the back surface of the pinion gear.

11. The differential device according to claim 3 ,

wherein the first groove portion is positioned between a back surface of the side gear and the back surface of the pinion gear.

12. The differential device according to claim 3 , wherein an inner wall surface at a rear side of at least a part of the third groove portion in a forward rotational direction, which is a rotational direction of the differential case during the vehicle forward movement, is inclined more gently than an inner wall surface at a rear side of the first groove portion in the forward rotational direction.

13. The differential device according to claim 12 , wherein the first groove portion is positioned between a back surface of the side gear and the back surface of the pinion gear.

14. The differential device according to claim 7 , wherein an inner wall surface at a rear side of at least a part of the third groove portion in a forward rotational direction, which is a rotational direction of the differential case during the vehicle forward movement, is inclined more gently than an inner wall surface at a rear side of the first groove portion in the forward rotational direction.

15. A differential device comprising:

a differential case including a case main body in which a housing space is formed, and a bearing boss protruding from the case main body, having a cylindrical shape with a case through-hole communicating with the housing space, and being rotatably supported about a first rotation axis;

a side gear housed in the housing space of the differential case and rotatably arranged about the first rotation axis; and

a pinion gear housed in the housing space of the differential case, rotatably arranged about a second rotation axis perpendicular to the first rotation axis, and meshing with the side gear,

wherein an introduction groove for introducing lubricating oil into the housing space of the case main body is formed on an inner peripheral surface of the bearing boss,

wherein an inner surface groove communicating with the introduction groove and extending toward a back surface side of the pinion gear is formed on an inner surface of the case main body,

wherein the inner surface groove includes a first groove portion and a third groove portion positioned radially inward from the first groove portion in the radial direction of the case main body, and

wherein a shape of at least a part of the first groove portion is a shape over which the lubricating oil is harder to climb during vehicle forward movement as compared with the shape of the third groove portion.

16. The differential device according to claim 15 , wherein an inner wall surface at a rear side of at least a part of the third groove portion in a forward rotational direction, which is a rotational direction of the differential case during the vehicle forward movement, is inclined more gently than an inner wall surface at a rear side of the first groove portion in the forward rotational direction.

17. The differential device according to claim 15 , wherein the third groove portion is covered with a back surface of the side gear.

18. The differential device according to claim 15 , wherein the first groove portion is positioned between a back surface of the side gear and a back surface of the pinion gear.

19. The differential device according to claim 16 , wherein the first groove portion is positioned between a back surface of the side gear and a back surface of the pinion gear.

20. The differential device according to claim 17 , wherein the first groove portion is positioned between a back surface of the side gear and a back surface of the pinion gear.