Abstract: When a solenoid has been turned on by supplying current to a coil thereof, the solenoid operation is checked by temporarily ceasing the supply of current to the coil to temporarily deenergize the solenoid. The current flowing in the coil is detected while the solenoid is temporarily deenergized, and the characteristics of the thus detected current are used to discriminate the position of a movable iron core of the solenoid. On the other hand, when the solenoid has been turned off by ceasing the supply of current to the coil, the solenoid operation is checked by temporarily supplying current to the coil to thereby temporarily energize the solenoid. The current flowing in the coil while the solenoid is temporarily energized is detected, and the characteristics of the thus detected coil current are used to determine the position of the movable iron core of the solenoid.

Abstract: A proportional pressure release valve comprising a valve body incorporating a valve seat, a valve closure member mounted in the valve body and cooperable with the valve seat to control flow of fluid through the valve from an inlet pressure port to an outlet tank port, and electromagnetic control means having a push pin operable to move, via resilient means, the valve closure member in dependence upon the magnitude of a control current applied thereto, wherein the valve further comprises damper means provided between the push pin and the valve closure member. The valve may also comprise an anti-cavitation ring having a bore and disposed downstream of the valve seat, the anti-cavitation ring being apertured to provide a fluid connection between the ring core and the tank port. The valve closure member may be guided for movement towards and away from the valve seat by guide means comprising at least one linear bearing.

Abstract: A proportional electromagnetic valve includes a valve main body having a valve member, a solenoid to drive the valve member, and an amplifier unit to control the solenoid. The solenoid is attached to one or both side portions of the valve main body. The amplifier unit has a size which is almost equal to a size on the unit attaching surface side of the valve main body and solenoids. The casing of the amplifier unit has an enclosing space large enough such that single printed board having all of drive amplifiers attached there to placed in the casing of the amplifier unit.

Abstract: A poppet valve in which a poppet is slidable in a valve body and opens or closes a main valve path for pressurized fluid at one end. The pressurized fluid is conveyed to a back pressure chamber at the rear of the poppet either through a reduced flow path or through a valve arrangement between the surfaces of the poppet and a poppet spool slidable within the poppet. Either a control rod or the poppet spool moving relative to the poppet opens a flow path at the side of the back pressure chamber and the flow continues through a hollow in the spool or the control rod to an oil chamber away from the back pressure chamber where it is released to a tank.

Abstract: A differential pressure regulator is arranged in series on the inflow side of a variable throttle for adjustment of a flow rate. An inlet pressure of the variable throttle is led into a primary pilot chamber of the differential pressure regulator. A constant flow control valve is provided in an oil passage connecting an oil passage on the inflow side of the differential pressure regulator with a secondary pilot chamber in order to allow a fluid of a constant flow rate to flow. The inflow side of a sequence valve is connected to the side of the secondary pilot chamber of the differential pressure regulator. The outflow side of the sequence valve is connected to the outlet side of the variable throttle or a tank. The inlet passage of the variable throttle is led into the primary pilot chamber of the sequence valve. An outlet pressure of the variable throttle is led into the secondary pilot chamber of the sequence valve. Further a check valve or a throttle is connected in parallel to the sequence valve.

Abstract: A pressure control valve including a valve, a spring for pressing the valve, and a power input means for compressing the spring further comprises a backup force-generating mechanism for producing and directing a backup force counter to the direction in which the reaction force due to the compression of the spring is exerted on the input means, so as to impart the backup force to the input means.

Abstract: A nozzle flapper valve provided with a nozzle, fixed throttle and flapper, characterized in that the flapper is formed to be cylindrical and has the cylindrical peripheral surface positioned on the axis of the nozzle so as to simplify the flapper moving mechanism and to prevent the flapper clearance from being clogged with dust in the fluid.