Abstract: For an energy-saving type control, a value of a control low rate QP controlled by a flow control valve V is closer to a value of a flow rate required by an output side such as a power cylinder 8, a steering valve 9 or the like, to suppress a driving torque of a pump P. An excitation current I of a solenoid SOL is specified on the basis of a solenoid current instruction value IT based on a steering torque and a solenoid current instruction value IS defining a standby flow rate.

Abstract: Provision of a fail-safe circuit which is capable of allowing a sub circuit to operate with reliability when a main circuit encounters abnormal conditions even in a system with only one supply source of pressure oil. A plurality of solenoid type control valves (3, 6) connected to an actuator (1) in parallel have centering springs respectively and are maintained at a neutral position in normal conditions. Each control valve is provided with a supply port, a return port and two actuator ports and is configured such that in the neutral position, the supply port and the return port are communicated with each other and interrupts communication with the actuator ports.

Abstract: For an energy-saving type control, a value of a control low rate QP controlled by a flow control valve V is closer to a value of a flow rate required by an output side such as a power cylinder 8, a steering valve 9 or the like, to suppress a driving torque of a pump P. An excitation current I of a solenoid SOL is specified on the basis of a solenoid current instruction value IT based on a steering torque and a solenoid current instruction value IS defining a standby flow rate.

Abstract: For an energy-saving type control, a value of a control low rate QP controlled by a flow control valve V is closer to a value of a flow rate required by an output side such as a power cylinder 8, a steering valve 9 or the like, to suppress a driving torque of a pump P. An excitation current I of a solenoid SOL is specified on the basis of a solenoid current instruction value IT based on a steering torque and a solenoid current instruction value IS defining a standby flow rate.

Abstract: The invention relates to a device that interrupts electric power to a driving circuit when a system failure is detected. A fail-safe mechanism is provided with a main switch circuit connected between a driving power source and a driver circuit; a sub switch circuit connected between the driving power source and the main switch circuit, and maintaining an OFF state in normal times; a timer circuit allowing the sub switch circuit for a predetermined time period after the driving power source is turned on; a failure detector circuit connected between the main switch circuit and a controller; and a sub switch control means bringing the sub switch circuit to an OFF state when the feeding of electric current is cut off. The main switch circuit is turned OFF when the failure detector circuit detects an abnormal condition of the controller.

Abstract: For an energy-saving type control, a value of a control low rate QP controlled by a flow control valve V is closer to a value of a flow rate required by an output side such as a power cylinder 8, a steering valve 9 or the like, to suppress a driving torque of a pump P. An excitation current I of a solenoid SOL is specified on the basis of a solenoid current instruction value IT based on a steering torque and a solenoid current instruction value IS defining a standby flow rate.

Abstract: For an energy-saving type control, a value of a control low rate QP controlled by a flow control valve V is closer to a value of a flow rate required by an output side such as a power cylinder 8, a steering valve 9 or the like, to suppress a driving torque of a pump P. An excitation current I of a solenoid SOL is specified on the basis of a solenoid current instruction value IT based on a steering torque and a solenoid current instruction value IS defining a standby flow rate.

Abstract: For an energy-saving type control, a value of a control low rate QP controlled by a flow control valve V is closer to a value of a flow rate required by an output side such as a power cylinder 8, a steering valve 9 or the like, to suppress a driving torque of a pump P. An excitation current I of a solenoid SOL is specified on the basis of a solenoid current instruction value IT based on a steering torque and a solenoid current instruction value IS defining a standby flow rate.