A pressure gauge includes a housing defining a fluid path and a bleed path. An inlet is mounted on the housing and a pressure sensor is disposed within the housing. A bleed valve is disposed along the fluid path and selectively opens or closes the bleed path. An actuator moves the bleed valve between a closed position and an open position. A control module is coupled to the pressure sensor and the actuator and includes a memory and a processor. A target fluid pressure is stored in the memory and the processor receives pressure data from the pressure sensor. When the pressure data is greater than the target fluid pressure, the processor controls the actuator to place the bleed valve in the open position. When the pressure data is equal to the target fluid pressure, the processor controls the actuator to place the bleed valve in the closed position.

An air control circuit including a safety function is simply formed from an air circuit. An air control circuit includes a main air line that controls an air device by concurrently turning on or off two external-pilot-operated electromagnetic valves, a pilot air line that supplies pilot air to the electromagnetic valves, and a pilot control line that switches the pilot air line between a supply state and an exhaust state. When one of the two electromagnetic valves suffers a breakdown to fail to be switched to an off position, air in the air device is exhausted through the other electromagnetic valve that has been switched to the off position to recover the air device, and the pilot air line is switched to the exhaust state by the pilot control line to prevent the two electromagnetic valves from restarting.

A discharge pressure scale (30) includes a valve housing (41) having a functional connector (A), a return flow connector (T) and a user connector (28). A valve piston (52) is guided such that it moves longitudinally against the effect of an energy accumulator (42), moving from a respective opening or regulating position, against a valve seat (94), into a closed position. The user connector (28) and return flow connectors (T) are separated from one another. The fluid pressure present at the user connector (28) can be guided onto a pressure-active surface (A.sub.1*) of the valve piston (52) by a pressure compensation device (70) in such a way that it moves into its respective opening or regulating position in a pressure-compensated manner due to the force of the energy accumulator (42).

A current controller for controlling a current of a solenoid is applied to a solenoid valve with a self-regulating pressure function from a feedback force according to an output hydraulic pressure. The current controller includes a current detector configured to detect an actual current of the solenoid, a drive unit configured to energize the solenoid with a predetermined energization period according to a drive signal, a signal output unit that sets a duty ratio of the drive signal such that the actual current follows a target current, the signal output unit being configured to generate and output the drive signal, a target setting unit that applies a dither amplitude with a dither period longer than the energization period, and an oscillation determination unit that determines, based on a behavior of the actual current, whether excessive oscillation is occurring or is trending toward excessive oscillation.

Certain embodiments provide a cover mounted on top of a manifold, the cover comprising an exhaust opening and an inner surface forming a space between the inner surface of the cover and an outer surface of the manifold, wherein the space is configured to receive pressurized gas at an inlet positioned on a first side of a valve. The valve is coupled to the outer surface of the manifold and positioned within the space. The exhaust opening is positioned on a second side of the valve opposite the first side of the valve such that pressurized gas circulates from the inlet around the valve and exits through the exhaust opening.

A valve, in particular a 4/2-way slide valve (60), includes a valve piston (67), which is guided in a longitudinally movable manner in a valve housing (25), for selectively connecting and disconnecting fluid connections in the valve housing (25), such as a pressure supply connection (P), a tank connection (T), and two utility connections (A, B). A magnetic system (49), to which current can be supplied, controls the valve piston (67). When no current is supplied to the magnetic system (49), the control pressure at one of the utility connections (A, B) can be set, in particular limited, by a control device (62, 70, 79, 80, 88) arranged in the valve housing.

A capacity control valve (1) includes a valve main body (10) having a first communication passage (11), a second communication passage (12), a third communication passage (13), and a main valve seat (15a), a valve element (20) having an intermediate communication passage (29), a main valve portion (21c), and an auxiliary valve portion (23d), a solenoid (30) that drives a rod (36) having an auxiliary valve seat (26c), and a first biasing member (43) that biases in the valve closing direction of the main valve portion (21c). The rod (36) is relatively moved with respect to the valve element (20) so as to open and close the auxiliary valve portion. The capacity control valve can efficiently discharge a liquid coolant irrespective of pressure of a suction chamber and lower drive force of a compressor at a liquid coolant discharging operation.

A device for controlling a required pressing force from a current collector of a vehicle on an overhead line, a method for using such a device and a power car having at least one such device, utilize a pilot control circuit, a working pressure control circuit and an adjustment device including a relay valve. The pilot control circuit adjusts a pilot control pressure and the relay valve uses a pilot control pressure to control a power pressure to provide a required working pressure for the pressing force of the current collector.

A solenoid valve system includes a supply solenoid valve, a plurality of exhaust solenoid valves, and a valve control section controlling opening and closing operation of the supply solenoid valve and the plurality of exhaust solenoid valves using PWM or PFM. The plurality of exhaust solenoid valves are disposed in parallel with each other. The supply solenoid valve and the plurality of exhaust solenoid valves have substantially identical flow rate characteristics. The number of the plurality of the exhaust solenoid valves is twice the number of the supply solenoid valve.

A current control device includes a target setting unit, a storage unit, an oil pressure ratio calculation unit, a specific current detection unit and a correction unit. The target setting unit adds a dither amplitude to a target current so that the current of the solenoid periodically changes at a dither cycle period longer than a PWM cycle period of the solenoid. The storage unit stores a stroke-current relationship between a stroke of the spool and the current of the solenoid. The oil pressure ratio calculation unit calculates an oil pressure ratio which is a value calculated by dividing an amplitude of the output oil pressure by an average value of the output oil pressure. The specific current detection unit detects a specific current based on the oil pressure ratio. The correction unit corrects the stroke-current relationship based on the specific stroke and the specific current.