Vehicle final reduction gear unit

A final reduction gear unit adapted to be used with a vehicle comprising:

• a drive shaft for transmitting a drive force;
• a small reduction gear operatively coupled to the drive shaft for rotation;
• a large reduction gear operatively meshing with the small reduction gear for rotation;
• a differential mechanism adapted to transmit a drive force from the large reduction gear to left and right axles;
• a differential case housing the differential mechanism;
• and
• a final-reduction-gear case provided closer to a vehicle body, and housing the small reduction gear, the large reduction gear, the differential mechanism and the differential case;
• wherein the vehicle final reduction gear unit further includes:
• first friction brake occupying an area between the final-reduction-gear case which is a stationary body and the differential case which is a rotating body for applying a pressing force in an axial direction to generate a frictional force in order to put a brake on the differential case;
• and
• a second friction brake occupying an area between the differential case and the right axle, for applying a pressing force in the axial direction to generate a frictional force in order to use a rotational difference to put the differential mechanism into a lock state;
• wherein the second friction brake is placed within the radius of the first friction brake,
• wherein the first friction brake comprises:
• a cylinder-shaped first friction brake supporter that is mounted to the differential case extends from one end of the differential case and opens in the vehicle-transverse direction toward a right case member, and
• the second friction brake comprises:
• a plurality of second rotation friction discs that are spine-fitted into a cylinder-shaped inner peripheral surface of the first friction brake supporter.

A vehicle final reduction gear unit comprising:

• a prime mover generating a drive force;
• a drive shaft transmitting a drive force from the prime mover;
• a small reduction gear coupled to the drive shaft for rotation;
• a large reduction gear meshing with the small reduction gear for rotation;
• a differential mechanism transmitting a drive force from the large reduction gear to left and right axles;
• a differential case housing the differential mechanism;
• and
• a final-reduction-gear case provided closer to a vehicle body, and housing the small reduction gear, the large reduction gear, the differential mechanism and the differential case;
• wherein the vehicle final reduction gear unit further includes:
• a first friction brake occupying an area between the final-reduction-gear case which is a stationary body and the differential case which is a rotating body for applying a pressing force in an axial direction to generate a frictional force in order to put a brake on the differential case;
• and
• a second friction brake occupying an area between the differential case and the right axle, for applying a pressing force in the axial direction to generate a frictional force in order to use a rotational difference to put the differential mechanism into a lock state;
• wherein the second friction brake is placed within the radius of the first friction brake, and further comprising:
• a brake operation device for braking the vehicle by activating the first friction brake and the second friction brake;
• and
• a diff-lock operation device for putting the differential mechanism into a lock state by activating the second friction brake alone.