Hitachi, Ltd.

Hiroyuki Hayama

Takashi Nezu

Yohei Katayama

Hiroyuki Yamaguchi

A fluid pressure shock absorber in which valve opening of the main valve is controlled by an inner pressure of a backpressure chamber. A first piston () and a second piston () coupled to a piston rod () are fitted in a cylinder () such that a piston chamber (C) is defined between the first and second pistons. An extension-side main valve () and a compression-side main valve () are provided in the piston chamber (C). Valve opening of the main valves is controlled by an extension-side backpressure chamber () and a compression-side backpressure chamber (). A compression-side check valve () and an extension-side check valve () are provided at the first piston () and the second piston (). During an extension stroke of the piston rod (), the compression-side check valve () is closed, whereby action of a pressure of a cylinder upper chamber (A) on the compression-side main valve () is prevented. During a compression stroke of the piston rod (), the extension-side check valve () is closed, whereby action of a pressure of a cylinder lower chamber (B) on the extension-side main valve () is prevented. Accordingly, it is possible to generate a stable damping force, and enhance durability of the extension-side main valve () and the compression-side main valve ().

Fluid pressure shock absorber

A first piston and a second piston coupled to a piston rod are fitted in a cylinder, and an intermediate chamber is formed between the first and second pistons. A compression-side check valve and an extension-side check valve are provided at the first piston and the second piston. An extension-side main valve and a compression-side main valve are disposed in the intermediate chamber. A downstream side of a damping force adjusting valve is connected to the intermediate chamber. Inner pressures of an extension-side backpressure chamber and a compression-side backpressure chamber are adjusted by the damping force adjusting valve, whereby valve opening of the extension-side and compression-side main valves is controlled. Hydraulic fluid of the downstream side of the damping force adjusting valve is first sent into the intermediate chamber, and then is sent to a cylinder upper chamber or a cylinder lower chamber. Due to this arrangement, it is possible to prevent a sudden drastic change in a hydraulic fluid pressure and thereby to generate a stable damping force.

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Yokohama, Japan

Hiroyuki Hayama