Kawasaki Jukogyo Kabushiki Kaisha

Toshiyuki Yoshida

Toyoaki Sagawa

The fluid pressure device includes a valve housing 2 in which a spool hole 14 is formed, and a spool 18 having a first spool portion 22 inserted in the spool hole 14, and the spool portion 22 is movable with respect to the first hole portion 26 of the spool hole 14 in its axial direction. More fluid grooves 110 are formed in the first spool portion 22. Pressurized fluid acting on one side of the fluid groove 110 have pressure higher than that of pressurized fluid acting on the other sides of the fluid groove 110. A first gap between an outer peripheral surface of the one side of the seal portion and an inner peripheral surface of the first hole 26 between the adjacent fluid groove 110 is set slightly greater than a second gap between an outer peripheral surface of the other side of the seal portion and the inner peripheral surface of the first hole.

Fluid pressure device

A relief valve to be disposed in a hydraulic circuit, for example an absolute circuit, such as in an industrial construction machine, comprises a casing of substantially cylindrical structure having one end and another end, the casing including a casing body, a pressure regulating plug and a lid member. The relief valve further comprises a valve seat fitted into one end of the casing and provided with an inflow hole through which a pressurized fluid is flown, a plunger disposed in the casing and having one flanged end slidably engaged with an inner surface of the one end of the casing, the plunger having a central through hole, a stepped piston member disposed in the casing to be slidable therein and having an outwardly stepped one end and a spring member disposed between another end of the stepped piston member and the flanged one end of the plunger. A fluid chamber is defined between another end of the casing and the one end of the stepped piston member. A damping chamber is defined between the stepped portion of the stepped piston member and the stepped portion formed to the casing. The fluid chamber and the damping chamber is communicated with each other through a communication passage. The through hole of the plunger having a throttle portion having a predetermined length and the other end of the stepped piston member having an outer diameter substantially equal to an inner diameter of the inflow hole of the valve seat.

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Nishinomiya, Japan

Toshiyuki Yoshida