Abstract: A hydraulic motor driving apparatus includes a directional control valve for supplying discharge pressure fluid from a hydraulic pump into a first or second port of a hydraulic motor and returning the hydraulic fluid from the second or first port into a tank, and a pilot pressure applying valve for controlling the directional control valve. The directional control valve is urged to its neutral position by springs, to its first position by hydraulic pressure against its first pressure receiving portion and to its second position by hydraulic pressure against its second pressure receiving portion. Discharge pressure fluid from the hydraulic pump is supplied via a check valve into the first and second ports of the hydraulic motor when the directional control valve is at the neutral position. The discharge pressure fluid is supplied into the first port of the hydraulic motor and a hydraulic pressure fluid of the second port flows into the tank, when the directional control valve is at the first position.

Abstract: There is disclosed an apparatus for controlling the capacity of a hydraulic motor (5) in a hydraulically driven motor vehicle, which comprises: a hydraulic pump (2) adapted to be driven by an engine (1) having a variable rotation speed; the hydraulic motor of a variable capacity type adapted to be rotated by a discharge pressure fluid from the hydraulic motor for driving a traveling body that constitutes the motor vehicle allowed to travel; a capacity control section for reducing the capacity of the hydraulic motor when the rotation speed of the engine is increased and for increasing the capacity of the hydraulic motor when the rotation speed of the engine is reduced, the capacity control section having a variable operation rate and being operable at a variety of positions among a maximum capacity position, an intermediate capacity position and a minimum capacity position; and an operation rate control unit for accelerating the operation rate of the capacity control section when it is operating at a position