Abstract: An air chamber (53) of a damping force adjusting mechanism (49) disposed in a hydraulic shock absorber (3) of a damping force adjusting type communicates with an air chamber (7) of an air spring through a tubular path (57). A free piston (51) is transferred in accordance with the pressure of the air chamber and a spool (46) is transferred to shift a damping force. The damping force presents a soft characteristic both on the extending side and on the retracting side in a usual status, presents a hard characteristic on the extending side and a soft characteristic on the retracting side when the pressure of the air chamber is high, and presents a soft characteristic on the extending side and a hard characteristic on the retracting side when the pressure of the air chamber (7) is low. The damping force can be obtained, which approximates the damping force control on the basis of a so-called sky-hook theory.

Abstract: When a hydraulic cylinder apparatus operates in a direction such that the same damping force as a skyhook damping force cannot be produced, a command signal is applied so as to operate an active system (a fluid supply/discharge valve) and supply or discharge a fluid relative to the hydraulic cylinder apparatus, to thereby provide compensation of the damping force and obtain a desired damping force (shock-absorbing function). It is unnecessary to continuously supply or discharge the fluid through the active system and energy consumption can be reduced as compared to a conventional active control.

Abstract: The flow of a hydraulic fluid caused by sliding movement of a piston in a cylinder is controlled by a disk valve and extension- and contraction-side main valves, thereby generating damping force. By controlling the valve opening pressures of the disk valve as a pressure control valve with respect to extension- and compression-side valve seats with a proportional solenoid actuator, damping force can be directly controlled independently of the piston speed. Moreover, the pressures in pilot chambers are changed to control the valve opening pressures of the extension- and compression-side main valves. Because the disk valve is placed between the extension- and compression-side valve seats, it is possible to simultaneously select different damping force characteristics for the extension and compression sides.

Abstract: The flow of a hydraulic fluid caused by sliding movement of a piston is controlled through a sub-disk valve, a main disk valve and a disk valve to generate damping force. A coil is energized to urge a plunger in the valve closing direction against spring force from a spring, thereby adjusting the relief pressure of the disk valve and thus controlling the damping force. The pressure in a back-pressure chamber varies according to the relief pressure of the disk valve. Thus, the valve opening pressure of the main disk valve is also adjusted. An abrupt input is absorbed by relieving the pressure from the back-pressure chamber by deflection of the disk valve. Because “soft” damping force characteristics, which are often used, are maintained with a small electric current, the power consumption can be reduced.