Patent ID: 6615869
Filing Date: 2003-09-09
Classification: F16K,Y10T

Abstract:
A solenoid valve comprising:a hollow sleeve being provided at a circumferential wall thereof with a first supply port, an output port, a first drain port, a second supply port and a second drain port, the second supply port being provided with a first control orifice; a spool slidably moving in the hollow sleeve; a seat member fixed to the hollow sleeve and having an oil hole; a control pressure chamber formed in the hollow sleeve between the seat member and the spool, an end of the oil hole communicating with the control pressure chamber; a supply passage through which the second supply port communicates via the first control orifice with the control pressure chamber; a drain passage through which the other end of the oil hole is able to communicate with the second drain port; a solenoid having an armature core movable according to an electromagnetic attracting force, the spool being moved in a direction away from the seat member by pressure increase of the control pressure chamber due to oil supplied thereto via the supply passage, when the armature core is in contact with the seat member and closes the other end of the oil hole, and being moved toward the seat member by pressure decrease of the control pressure chamber due to the oil ejected therefrom via the drain passage, when the armature core is away from the seat member and opens the other end of the oil hole, so that one of a communication between the first supply port and the output port and a communication between the output port and the first drain port is selected; and a second control orifice, whose cross sectional opening area is smaller than that of the first control orifice, formed in the supply passage when an end of the spool comes in contact with an end of the seat member so that a flow amount of the oil supplied to and ejected from the control pressure chamber through the supply and drain passages after the spool contacts the seat member is smaller than that before the spool contacts the seat member.