Shock absorber unit

Abstract

A valve system is disclosed which prevents a shrinkage or an elongation of a shock absorber in response to a compressive or tensile load applied thereto as a result of a rolling or pitching effect of a vehicle. The valve system comprises a switching valve movable among a second position in which a high pressure is introduced into an upper chamber of a shock absorber while a low pressure is introduced into a lower pressure which is separated from the upper chamber by a piston, a third position in which a low pressure is introduced into the upper chamber while a high pressure is introduced into the lower chamber, and a first position (holding position) in which the upper and the lower chamber are disconnected from a pressure source; a first and a second open/close valve which open or close a path between the switching valve on one hand and the upper and the lower chamber on the other hand; and a third open/close valve which opens or closes a path between the upper chamber and a gas spring bladder. A second mode in which the switching valve assumes its second position and the first open/close valve is enabled to pass a flow therethrough is selected in response to the compressive load. A third mode in which the switching valve assumes its third position and the second open/close valve is enabled to pass a flow therethrough while the third open/close valve is closed is selected in response to the tensile load. When neither compressive nor tensile load is applied, the first mode is selected in which the switching valve assumes its first position and the third open/close valve is enabled to pass a flow therethrough. The valve system assumes the first mode when all of the switching valve and the first, the second and the third open/close valve are deenergized.