Driving-force distribution device

A driving-force distribution device mounted on a four-wheel-drive vehicle that includes, among a pair of front wheels and a pair of rear wheels, one pair as a pair of right and left main drive wheels and the other pair as a pair of right and left auxiliary drive wheels to which driving force is transmitted via a propeller shaft, and that switches between a two-wheel-drive state and a four-wheel-drive state by a first engagement/disengagement mechanism capable of cutting off transmission of the driving force from a driving source to the propeller shaft, the driving-force distribution device comprising:

• a differential mechanism that distributes the driving force of the driving source transmitted via the propeller shaft in the four-wheel-drive state to the pair of right and left auxiliary drive wheels in a manner to allow differential motion between the right and left auxiliary drive wheels;
• and,
• a second engagement/disengagement mechanism that is disposed between either one auxiliary drive wheel among the pair of right and left auxiliary drive wheels and the differential mechanism, and that cuts off transmission of the driving force from the differential mechanism to the one auxiliary drive wheel, wherein,
• the differential mechanism includes:
• a differential case that is coupled to the propeller shaft via a gear mechanism;
• a pinion shaft that is supported by the differential case to rotate integrally with the differential case;
• a plurality of pinion gears that are supported via the pinion shaft;
• and a pair of side gears that mesh with the pinion gears such that gear axes of the pair of side gears extend orthogonally to gear axes of the pinion gears, and meshing between the pinion gears and the pair of side gears is lubricated with lubricant,
• the pinion shaft has a flow passage through which the lubricant is allowed to flow from a side of one pinion gear positioned below among the pinion gears to a side of another pinion gear in a two-wheel-drive mode in which the pair of side gears rotate in opposite directions with the differential case not rotating,
• the lubricant is supplied to the flow passage by rotation of the one pinion gear positioned below, and
• an oil groove configured to guide the lubricant to the flow passage is formed on at least one surface of a gear back surface of each pinion gear and a sliding-contact surface of a sliding-contact member that is in sliding-contact with the gear back surface.

A driving-force distribution device mounted on a four-wheel-drive vehicle that includes, among a pair of front wheels and a pair of rear wheels, one pair as a pair of right and left main drive wheels and the other pair as a pair of right and left auxiliary drive wheels to which driving force is transmitted via a propeller shaft, and that switches between a two-wheel-drive state and a four-wheel-drive state by a first engagement/disengagement mechanism capable of cutting off transmission of the driving force from a driving source to the propeller shaft, the driving-force distribution device comprising:

• a differential mechanism that distributes the driving force of the driving source transmitted via the propeller shaft in the four-wheel-drive state to the pair of right and left auxiliary drive wheels in a manner to allow differential motion between the right and left auxiliary drive wheels;
• and,
• a second engagement/disengagement mechanism that is disposed between either one auxiliary drive wheel among the pair of right and left auxiliary drive wheels and the differential mechanism, and that cuts off transmission of the driving force from the differential mechanism to the one auxiliary drive wheel, wherein,
• the differential mechanism includes:
• a differential case that is coupled to the propeller shaft via a gear mechanism;
• a pinion shaft that is supported by the differential case to rotate integrally with the differential case;
• a plurality of pinion gears that are supported via the pinion shaft;
• and a pair of side gears that mesh with the pinion gears such that gear axes of the pair of side gears extend orthogonally to gear axes of the pinion gears, and meshing between the pinion gears and the pair of side gears is lubricated with lubricant,
• the pinion shaft has a flow passage through which the lubricant is allowed to flow from a side of one pinion gear positioned below among the pinion gears to a side of another pinion gear in a two-wheel-drive mode in which the pair of side gears rotate in opposite directions with the differential case not rotating,
• the flow passage includes a first flow passage portion that extends in a direction along the axis of the pinion shaft from the side of the one pinion gear to the side of the another pinion gear,
• the lubricant is supplied to the flow passage by rotation of the one pinion gear positioned below,
• the first flow passage portion is a hole through the pinion shaft, and
• the pinion shaft includes a second flow passage portion extending in a direction perpendicular to the axis of the pinion shaft through the pinion shaft and intersecting the first flow passage portion.