Image Number 2 for United States Patent #5706849.
In a flow control valve, a valve spool is movable for variably controlling an opening area of a port portion of a drain passage so that a necessary flow rate of fluid is conducted from a first pressure chamber to an outlet passage through a control orifice while a surplus flow rate of fluid is returned from the first pressure chamber to the drain passage. A movable sleeve is installed in a valve spool accommodation hole and around the valve spool. The movable sleeve has through holes communicable with the drain passage and an inlet passage, respectively. The movable sleeve has a first axial end portion disposed in the first pressure chamber and a second axial end portion disposed in a low pressure chamber. A spring is disposed in the low pressure chamber for urging the movable sleeve toward the first pressure chamber side. The movable sleeve is movable relative to the valve spool in response to a variation of pressure in the first pressure chamber for varying the opening area of the port portion of the drain passage.