Hydraulic system for driving axial piston type hydraulic motor
A hydraulic system is provided for driving an axial piston type hydraulic motor wherein a swash plate 6 can be tilted in either direction from a neutral position to produce forward and reverse rotation of the motor, the system comprising a double acting piston and cylinder unit 10 for tilting the swash plate, a pair of springs 11a, 11b biasing the swash plate to its neutral position, a valve 13 which connects the two cylinder chambers 9a, 9b in its neutral position and which can be actuated to supply oil pressure to either of the cylinder chambers to tilt the swash plate in the selected direction, an inlet passage 21 connecting a hydraulic pump P to an inlet port 7A of the motor via a main control valve 23 which operates to open or close the inlet passage in response to a predetermined signal, an outlet passage 22 connecting an outlet port 7B of the motor to a tank via a passage switching valve 24 which operates to open or close the outlet passage in response to a predetermined signal, a bypass passage 25 around the passage switching valve and a pressure relief valve 26 installed in the bypass passage.