DURCHFLUSSMENGENREGELVENTIL

摘要

A flow control valve unit for controlling flow rate of a pressurized working fluid flowing from a hydraulic pump to an actuator of a power steering device includes a spool chamber, a spool valve, an inlet port, a discharge port, a drain port and a notch. The spool chamber has a first chamber portion for receiving the fluid through the inlet port, and a second chamber portion which is communicated with the discharge port. The spool valve is movable from a first position in which the drain port is fully closed to a second position in which the drain port is partially opened. The second position defines first and second gaps respectively between a first land portion of the spool valve and an edge of the drain port and between the first land portion and an edge of the notch for allowing the fluid to flow from the first chamber portion to the drain port through two passages. The notch is positioned so as to be substantially opposed to the drain port and to make an area of the second gap larger than that of the first gap by a certain degree, such that, when the first gap is substantially narrowly opened, flow rate of the fluid flowing from the first chamber portion to said drain port through the first gap is set substantially equal to or less than flow rate of the fluid flowing through the second gap.