A proportional pressure reducing valve includes a spool having a first end connected to a solenoid and a second end exposed to a feedback chamber. The spool is formed with a groove for allowing a supply port to communicate with an output port when the spool is driven by the solenoid in proportion to solenoid current under balanced condition of an axial force of the solenoid and feedback pressure.Check Valves The pressure reducing valve further comprises a pressure reduction valve including a second spool formed with a path, for relieving hydraulic pressure within the feedback chamber to the drain port, Reducing Valveswhen output port pressure rises a predetermined relief pressure, to sharply increase the output port pressure up to the supply pressure in proportion to the current passed through the solenoid. WATER POWER CONTROL VALVEA proportional pressure reducing valve comprising: a valve housing formed with a supply port, an output port, a drain port, and a feedback chamber communicating with the output port; a proportional solenoid attached to said valve housing; a first spool having a first end connected to said proportional solenoid and a second end exposed to the feedback chamber, said first spool formed with a groove for allowing the supply port to communicate with the output port, when said first spool is driven by said proportional solenoid, in such a way that output pressure at the output port increases in proportion to current passed through said proportional solenoid under balanced conditions of an axial force applied to the first end of said first spool by said proportional solenoid and a feedback force applied to the second end of said first spool within the feedback chamber; and a pressure reduction valve including a second spool formed with a path, for relieving hydraulic pressure within the feedback camber to the drain port, when output port pressure rises beyond a predetermined relief pressure determined by a spring, to sharply increase the output port pressure up to the supply pressure in proportion to the current passed through the proportional solenoid. As described above, in the proportional pressure reducing valve including a spool housed in a valve housing in such a way that an axial force of a proportional solenoid is applied to one end thereof and an output pressure is feedbacked to the other end thereof via a throttle formed in a feedback chamber so as to be balanced, since the feedback chamber communicates with a tank via a control valve after output port pressure increases gradually to a relief pressure, it is possible to increase the output pressure momentarily up to the supply pressure. That is, it is possible to improve the control precision, widen control pressure range, and increase response speed, without increasing the size of the proportional solenoid and the current passed therethrough, when applied to the clutch assembly. The valve output pressure below the relief pressure is used to engage the clutch in a half clutch condition and the valve output pressure the same as the supply pressure is used to engage the clutch in a tight clutch condition, after a sufficient torque has been transmitted.

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