Patent ID: 6976358

Claim:
A circuit for controlling a discharge amount of a hydraulic pump, comprising: a variable displacement hydraulic pump for connection with an engine; an actuator connected with the hydraulic pump; a center bypass type directional switching valve installed in a flow path between the hydraulic pump and the actuator for controlling a start, stop and directional switching of the actuator during a switching operation; a pilot signal generating means installed in a down stream side of a center bypass path of the directional switching valve for controlling a discharge amount of the hydraulic pump; and a discharge amount adjusting valve which is installed in a supply path of the actuator of the center bypass type directional switching valve for controlling a discharge amount of hydraulic fluid supplied to the actuator and has an opening portion opened and closed based on a difference pressure between an upper stream side pressure and a down stream side pressure of the supply path of the actuator and an elastic force of a valve spring.