US Patent 7302875 Rotation transmitting device and hydraulic drive unit

A hydraulic drive device, comprising a hydraulic motor (10), a rotating body (20) connected to the drive shaft (11) of the hydraulic motor (10), functioning, by itself as a flywheel, and having an internal gear (21) formed on the output side thereof, a rotation transmitting device (1) having a gear mechanism for transmitting the rotating force of the rotating body (20) to an output shaft gear (50) by allowing counter gears (30) to mesh with the internal gear (21) and the outer shaft gear (50) to mesh with the counter gears (30), and an output shaft connected to the output shaft gear (50). Whereby, since a variation in rotating speed of the hydraulic motor (10) can be absorbed by the rotation transmitting device (1), the hydraulic motor (10) can be used directly as the drive source of a vehicle such as a car and a truck.