Patent ID: 8544619

Claim:
A fluid pressure shock absorber, comprising: a cylinder in which a fluid is sealingly contained; a piston slidably fitted in the cylinder, the piston dividing the interior of the cylinder into a first chamber and a second chamber; a piston rod having one end coupled to the piston and the other end extending to an outside of the cylinder; a piston chamber formed in the piston; an extension-side oil passage formed in the piston so as to establish communication between the first chamber and the piston chamber; a compression-side oil passage formed in the piston so as to establish communication between the second chamber and the piston chamber; an extension-side piston oil passage formed in the piston so as to establish communication between the second chamber and the piston chamber; a compression-side piston oil passage formed in the piston so as to establish communication between the first chamber and the piston chamber; an extension-side check valve disposed on the second chamber side of the extension-side piston oil passage so as to allow a flow of fluid from the piston chamber to the second chamber; a compression-side check valve disposed on the first chamber side of the compression-side piston oil passage so as to allow a flow of fluid from the piston chamber to the first chamber; an extension-side main valve disposed within the piston and disposed on the piston chamber side of the extension-side oil passage; an extension-side backpressure chamber containing an inner pressure which acts on the extension-side main valve in a valve-closing direction of the extension-side main valve; a compression-side main valve disposed within the piston and disposed on the piston chamber side of the compression-side oil passage; and a compression-side backpressure chamber containing an inner pressure which acts on the compression-side main valve in a valve-closing direction of the compression-side main valve, wherein: the piston chamber is separated from the first chamber and the second chamber by the extension-side main valve, the compression-side check valve, the compression-side main valve, and the extension-side check valve, parts of the fluid flows are introduced into the extension-side backpressure chamber and the compression-side backpressure chamber, and opening of the extension-side main valve and the compression-side main valve is controlled by utilizing the inner pressures of the extension-side backpressure chamber and the compression-side backpressure chamber.