Vehicle differential gear
A vehicle differential gear includes first and second pinion gears rotatably supported by a differential case; first and second side gears meshing with the first and second pinion gears and each coupled to corresponding one of a pair of output shafts; and a center washer, a first end washer and a second end washer each having a sliding surface that slides with an axial end face of at least one side gear of the first or second side gears, the sliding surface being lubricated by a lubricating oil; wherein a surface treatment for enhancing a solid lubricating property is performed on the washers.
1. A vehicle differential gear that distributes a driving force of a drive source of a vehicle to a pair of output shafts while allowing a differential operation, the vehicle differential gear comprising:
a differential case, to which the driving force is input;
a plurality of pinion gears rotatably supported by the differential case;
a pair of side gears meshing with the plurality of pinion gears and each coupled to a corresponding one of the pair of output shafts;
a washer having a sliding surface that slides with an axial end face of at least one side gear of the pair of side gears to create a frictional force, the sliding at the sliding surface being lubricated by a lubricating oil; and
a solid lubricant coating on the sliding surface to suppress a fluctuation of the frictional force, wherein
the pair of side gears and the plurality of pinion gears are helical gears that generate a thrust force in an axial direction by meshing.
2. The vehicle differential gear according to claim 1 , wherein the washer is arranged between the pair of side gears.
3. The vehicle differential gear according to claim 1 , wherein the washer is arranged between the side gear and an inner surface of the differential case.
4. The vehicle differential gear according to claim 1 , wherein the solid lubricant coating contains molybdenum disulfide and graphite.
5. The vehicle differential gear according to claim 1 , wherein a Vickers hardness of the sliding surface of the washer is lower than a Vickers hardness of the axial end face of the side gear.