PURPOSE: To make discharge mode control at several stages performable without using a special means at the outside by constituting a means, which changes the maximum grade of a swash plate against a main shaft stepwise, solidly in a pump body.
CONSTITUTION: For example, at time of driving on a rough road, when a large oil quantity is necessary for an actuator, an electromagnetic part 9b of a selective operating mechanism is unenergized, a spool 9a is advanced, working fluid is made to flow into a radial hole 86 of a maximum tilting angle selector mechanism 8 from a fine diametral part 85, and a relay piston 8b is set free, thereby holding a control plunger at an allowable maximum tilting angle position with a spring 7b. On the other hand, at time of driving on a level road, the electromagnetic part 9b is energized, the spool 9a is moved downward, leading a pump port Ps to a cylinder discharge port 150, and discharge oil is made to flow into the radial hole 86 of the maximum tilting angle selector mechanism 8 from a cylinder port 9A, and then the piston 8b is moved upward, whereby the control plunger 6 is also moved upward, thus a swash plate 2 is displaced so as to cause its maximum tilting angle to become smaller. Thus, efficient control is performable.
ISHIKAWA MASAKUNI
KAZAHAYA YUKIO
