Abstract: A frequency-dependent mechanism provided at the lower end of a piston rod includes a tubular housing displaceable in an inner tube, together with the piston rod as one unit, and further includes a free piston and O-rings. A shutter of a passage area varying mechanism is provided with an axially extending inner hole, orifices, and oil grooves. The opening area between oil holes 3C and the orifices 33B is changed according to the rotational position of the shutter. The opening area between oil holes 3D and 3E and the oil grooves 33C and 33D and the opening area between oil holes 3F and 3G and the oil grooves 33E and 33F are also variably adjusted according to the rotational position of the shutter.

Abstract: 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.

Abstract: 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.

Abstract: An object of the present invention is to provide a damping force adjustable hydraulic shock absorber, in which response delay of a pressure control valve and self-excited vibration of a valve body can be prevented. A damping force is generated by controlling an oil flow between an annular oil passage 21 and a reservoir 4 generated by a sliding movement of a piston in a cylinder with use of a back-pressure type main valve 27 and a pressure control valve 28. The damping force is directly generated by the pressure control valve 28, and a valve-opening pressure of the main valve 27 is adjusted by adjusting an inner pressure of a back-pressure chamber 53. In the pressure control valve 28, a valve spring 57 is disposed between a valve body 56 and a plunger 34. A mass of the valve body 56 is sufficiently less than that of a plunger 34, and a spring stiffness of the valve spring 57 is higher than that of a plunger spring 36.

Abstract: An object of the present invention is to generate a stable damping force and enhance durability of a main valve in a hydraulic shock absorber in which valve opening of the main valve is controlled by an inner pressure of a backpressure chamber. A first piston 3 and a second piston 4 coupled to a piston rod 10 are fitted in a cylinder 2 such that a piston chamber 2C is defined between the first and second pistons 3, 4. An extension-side main valve 18 and a compression-side main valve 23 are provided in the piston chamber 2C. Valve opening of the main valves is controlled by an extension-side backpressure chamber 19 and a compression-side backpressure chamber 24. A compression-side check valve 13 and an extension-side check valve 16 are provided at the first piston 3 and the second piston 4. During an extension stroke of the piston rod 10, the compression-side check valve 13 is closed, whereby action of a pressure of a cylinder upper chamber 2A on the compression-side main valve 23 is prevented.

Abstract: In a controllable damping force shock absorber, a piston member connected to a piston rod is disposed in a cylinder in which a magnetic fluid is contained. A disc valve having an extension-stroke pressure-receiving portion and a compression-stroke pressure-receiving portion is provided in the piston member, and a pilot chamber is formed on a rear side of the disc valve. A coil is provided adjacent to passages communicated with the pilot chamber. By energizing the coil, a magnetic field that acts on the magnetic fluid flowing through the passages is generated, changing the viscosity of the magnetic fluid to control a damping force. A valve-opening pressure of the disc valve is controlled according to the pressure in the pilot chamber, such a way that the magnetic fluid exposed to the magnetic field can flow at a low flow rate, thus achieving low power consumption.

Abstract: A piston connected to a piston rod is slidably fitted in a cylinder having a hydraulic fluid sealed therein. First and second poppet valves having different valve opening characteristics are provided in first and second extension main passages, respectively. A pilot control valve is provided in a sub-passage. The control pressure of the pilot control valve is adjusted by a proportional solenoid, thereby controlling damping force. At the same time, the pressure at the upstream side of the pilot control valve is introduced into back-pressure chambers to adjust the valve opening pressures of the first and second poppet valves. Because the first and second poppet valves are sequentially opened or closed, damping force can be controlled stepwisely, and ideal damping force characteristics can be obtained.

Abstract: In a controllable damping force shock absorber, a piston member connected to a piston rod is fittingly disposed in a cylinder in which a magnetic fluid is sealably contained. A disc valve having an extension-stroke pressure-receiving portion and a compression-stroke pressure-receiving portion is provided in the piston member, and a pilot chamber is formed on a rear side of the disc valve. A coil is provided adjacent to passages communicated with the pilot chamber. By energizing the coil for excitation, a magnetic field that acts on the magnetic fluid flowing through the passages is generated, thus changing the viscosity of the magnetic fluid to thereby control a damping force. A valve-opening pressure of the disc valve is controlled according to the pressure in the pilot chamber, in such a way that the magnetic fluid exposed to the magnetic field can be flowed at a low flow rate, thus achieving low power consumption.

Abstract: A piston connected with a piston rod is slidably fitted in a cylinder having a hydraulic fluid sealed therein. First and second poppet valves having different valve opening characteristics are provided in first and second extension main passages, respectively. A pilot control valve is provided in a sub-passage. The control pressure of the pilot control valve is adjusted by a proportional solenoid, thereby controlling damping force. At the same time, the pressure at the upstream side of the pilot control valve is introduced into back-pressure chambers to adjust the valve opening pressures of the first and second poppet valves. Because the first and second poppet valves are sequentially opened or closed, damping force can be controlled stepwisely, and ideal damping force characteristics can be obtained.

Abstract: A free piston defines a gas chamber in a cylinder, an interior of which is divided into a rod-side chamber and a bottom-side chamber by a piston. An accumulator having a gas chamber is connected to the rod-side chamber by a first oil line, midway of which is provided a damping-force generating unit. Also, the bottom-side chamber and the first oil line are communicated to each other by a communication line, midway of which is provided a spring-constant switchover valve for communication and shut-off of the communication line. Accordingly, when the spring-constant switchover valve puts the communication line in communication, the two gas chambers are compressed to make a spring constant small, thereby making comfort in a vehicle favorable. Meanwhile, the spring-constant switchover valve shuts off the communication line, only one of the gas chambers is compressed to make the spring constant large, thereby limiting a contracting displacement of a piston rod and suppressing rolling of the vehicle.