A hydraulic control apparatus includes an output-side oil passage into which oil from a first oil passage and oil from a second oil passage flow, and a pressure regulating check valve regulating a hydraulic pressure in the second oil passage. The pressure regulating check valve includes first and second elastic portions housed in a spool hole between a valve body and a bottom of the spool hole. A natural length of the second elastic portion is shorter than a distance between the valve body and the bottom when the valve body closes an inflow hole. The second elastic portion applies an elastic force to the valve body in a state in which the valve body opens the inflow hole.

A pump device 1 includes a relief valve 42 having a ball 45 and a valve seat 44. The valve seat 44 has a ring-shaped seat surface 52 having a wide portion 52a and a narrow portion 52b on which the ball 45 is seated. Upon valve opening, the ball 45 is pressed in a valve opening direction by a pressing force F1 according to a pressure P of working fluid while being pressed against the wide portion 52a. The ball 45 rolls on the seat surface 52 upon the valve opening while continuing or keeping contact with the wide portion 52a. At this time, the ball 45 is stably held with the ball 45 contacting the wide portion 52a of the seat surface 52. Noise of the relief valve 42 caused by vibration of the ball 45 is therefore suppressed.

A hydraulic control system for vehicles is provided. A switching valve (34) that is adapted to provide a communication between an electric oil pump (25) and a drain passage while inhibiting a delivery of the oil from the electric oil pump (25) to the control object (20, C) when an output pressure of the mechanical oil pump (9) is higher than a predetermined level, and to provide a communication between the electric oil pump (25) and the control object (20, C) through a predetermined oil passage when an output pressure of the mechanical oil pump (9) is lower than the predetermined level. The electric oil pump (25) discharges oil before establishing the communication between the electric oil pump (25) and the control object (20, C) as a result of reduction in the output pressure of the mechanical oil pump (9) to be lower than the predetermined level.

Embodiments include a flow regulating device. The flow regulating device may include a check valve. The check valve can have a first flange, a second flange and a ball seated against a seat defined by the first flange. The check valve is in a closed position when the ball is seated against the first flange. One or more stoppers may be positioned at a distance from the first flange. A fluid may flow through a first orifice and a second orifice defined in the first and second flanges respectively, when the first check valve is in an open position. The fluid lifts the ball from the first orifice, and pushes the ball towards the second orifice. The stoppers abut the ball when the first check valve is in a fully open position.

The invention relates to an system for supplying a hydraulic circuit with hydraulic fluid. The system includes a working reservoir and an auxiliary reservoir connected to the working reservoir by a hydraulic line. An air pump has an inlet connected to a suction line that opens into a liquid-free portion of the auxiliary reservoir so that a negative pressure can be built up in the auxiliary reservoir relative to the atmospheric ambient pressure. The air pump inlet is also connected to a control line, which comprises a control opening which is covered by the hydraulic fluid in the working reservoir, at least before the air pump is started up.

A pressure switch including a pressure chamber and a moving disc. The moving disc is moveable in response to a pressure in the pressure chamber to cause contact between a moveable contact and a fixed contact. An orifice communicates a fluid pressure into the pressure chamber. The orifice provides a tortuous path for a fluid flow to reach the pressure chamber. An oil supply system and a generator are also disclosed.

Systems and methods for improving generation of vacuum for a vehicle are disclosed. In one example, an air conditioning compressor bypass valve is selectively activated to improve generation of vacuum by an engine. The systems and methods may reduce the possibility of compressor clutch degradation.

A valve member for a spring-loaded valve assembly includes a top portion having a spring retaining recess, the spring retaining recess extending into the top portion to form a void space, the void space to receive at least one coil of a spring, the spring retaining recess having a recess diameter that is smaller than a top portion diameter, wherein the recess diameter is larger than a rest diameter of a spring base including the coil, the spring retaining recess blocking expansion of the at least one coil when the spring is compressed. The valve member also includes a bottom portion coupled to the top portion. The valve member further includes a sealing element positioned axially below a shoulder of the top portion and legs coupled to the bottom portion.