Abstract: One aspect of the present invention is configured in such a manner that a main valve (a valve member) is in abutment with only a ridge portion (a second protrusion portion) on the inner peripheral side of a seat portion (a first seat portion) in a state of being mounted on a piston. This configuration can reduce the radial contact width between the main valve and the seat portion, and contribute to preventing or reducing variations in the valve-opening point and the damping force by managing the radial dimension of the ridge portion on the inner peripheral side of the seat portion to allow the contact diameter between the main valve and the seat portion to be kept constant.

Abstract: The present invention causes a low-rigidity disk to be supported by a backup disk (a deformation prevention portion), and therefore can prevent the low-rigidity disk from being deformed due to an inflow of hydraulic oil to between the low-rigidity disk and a disk adjacent thereto according to an increase in a pressure in a cylinder upper chamber during an extension stroke, and can improve the durability of the low-rigidity disk.

Abstract: A shock absorber is configured in such a manner that a flow passage area of each of first orifices 169 and 189 is smallest throughout a communication passage that establishes communication between a chamber 2A or 2B on an upstream side and a chamber 2B or 2A on a downstream side, and therefore prevents a pressure in a back-pressure chamber 55 or 26 from excessively increasing. As a result, the shock absorber can prevent overshoot of a damping force due to a delay of valve opening of a main valve 53 or 23 due to a remaining pressure in the back-pressure chamber 55 or 26 when a movement of a piston 3 is switched from one direction to an opposite direction.

Abstract: Provided is a shock absorber in which a check valve seated on a seat portion (second seat portion) having an annular shape is quickly opened during a reverse stroke. As a result, a working fluid in a chamber on a downstream side can be quickly introduced into a back-pressure chamber. Hence, a delay in response of a damping force, which may be caused by sticking of the check valve to a relief valve, can be suppressed.

Abstract: The present invention provides a shock absorber capable of improving responsiveness during an extension stroke without leading to an increase in an axial length. A shock absorber includes a chamber provided on a one-side end of a pilot valve and disposed in communication with a cylinder upper chamber, a communication passage configured to establish communication between the chamber and a cylinder lower chamber via a compression-side passage, and a check valve configured to permit hydraulic fluid in the communication passage to flow into the cylinder lower chamber during an extension stroke.

Abstract: Provided is a shock absorber that is so designed that fail-down is prevented, which is caused when solenoid thrust is relatively small. The shock absorber comprises a chamber disposed on one side of a valve element and communicating with a cylinder's one side chamber and a cylinder's other side chamber, a first communication passage allowing the chamber and the cylinder's one side chamber to communicate with each other, and a second communication passage allowing the chamber and the cylinder's other side chamber to communicate with each other. The first communication passage includes a first orifice, and the second communication passage includes a second orifice.

Abstract: In a shock absorber, an extension-side check valve permitting a flow of hydraulic fluid directed from a common passage to a compression-side passage side, and a compression-side orifice establishing communication between the compression-side passage and a compression-side back-pressure chamber are provided in an extension-side discharge passage. A compression-side check valve permitting a flow of hydraulic fluid directed from the common passage to an extension-side passage side, and an extension-side orifice establishing communication between the extension-side passage and an extension-side back-pressure chamber are provided in a compression-side discharge passage. A pilot valve includes a valve body slidably inserted in the common passage, and a valve spring biasing the valve body in a valve-opening direction.

Abstract: Provided is a shock absorber that is so designed that fail-down is prevented, which is caused when solenoid thrust is relatively small. The shock absorber comprises a chamber disposed on one side of a valve element and communicating with a cylinder's one side chamber and a cylinder's other side chamber, a first communication passage allowing the chamber and the cylinder's one side chamber to communicate with each other, and a second communication passage allowing the chamber and the cylinder's other side chamber to communicate with each other. The first communication passage includes a first orifice, and the second communication passage includes a second orifice.

Abstract: The present invention provides a shock absorber capable of improving responsiveness during an extension stroke without leading to an increase in an axial length. A shock absorber includes a chamber provided on a one-side end of a pilot valve and disposed in communication with a cylinder upper chamber, a communication passage configured to establish communication between the chamber and a cylinder lower chamber via a compression-side passage, and a check valve configured to permit hydraulic fluid in the communication passage to flow into the cylinder lower chamber during an extension stroke.

Abstract: In a shock absorber, an extension-side check valve permitting a flow of hydraulic fluid directed from a common passage to a compression-side passage side, and a compression-side orifice establishing communication between the compression-side passage and a compression-side back-pressure chamber are provided in an extension-side discharge passage. A compression-side check valve permitting a flow of hydraulic fluid directed from the common passage to an extension-side passage side, and an extension-side orifice establishing communication between the extension-side passage and an extension-side back-pressure chamber are provided in a compression-side discharge passage. A pilot valve includes a valve body slidably inserted in the common passage, and a valve spring biasing the valve body in a valve-opening direction.

Abstract: 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 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, and valve-opening pressure of the main valve is adjusted by adjusting an inner pressure of a back-pressure chamber. In the pressure control valve, a valve spring is disposed between a valve body and a plunger. A mass of the valve body is sufficiently less than that of the plunger, and a spring stiffness of the valve spring is higher than that of a plunger spring.

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 volume compensation accumulator apparatus connected to a conduit connecting hydraulic cylinders in a suspension system. The volume compensation accumulator apparatus includes an arrangement of the two orifice plates in series in a spaced-apart relation, which eliminates the necessity of reducing the diameters of the orifices while providing the same orifice characteristic as that of an orifice having a smaller diameter, thereby making the boring process of the orifice easy, and reducing clogging of the orifices with foreign objects.

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: There is provided with a cylinder apparatus comprising: a cylinder; a piston; a piston rod, one end of which is connected to the piston and the other end of which is extended outside; an external cylinder provided at an outer periphery of the cylinder so as to form a reservoir in which to seal the hydraulic liquid and gas therebetween; a base valve dividing the second chamber and the reservoir; a first check valve provided with the piston so as to allow flow of the hydraulic liquid only from the second chamber side to the first chamber side; a second check valve provided with the base valve so as to allow flow of the hydraulic liquid only from the reservoir side to the second chamber side; a flow passage connecting the first chamber with the reservoir; and an opening and closing valve opening and closing the flow passage.

Abstract: The present invention enables easy formation of an extremely small orifice in a volume compensation accumulator apparatus connected to a conduit connecting hydraulic cylinders in a suspension system. The volume compensation accumulator apparatus comprises an arrangement of the two orifice plates in series in a spaced-apart relation, which eliminates the necessity of reducing the diameters of the orifices while providing the same orifice characteristic as that of an orifice having a smaller diameter, thereby making the boring process of the orifice easy, and reducing clogging of the orifices with foreign objects.

Abstract: A controllable damping force hydraulic shock absorber including a pilot type damping valve having a back-pressure chamber for each of an extension stroke and a compression stroke. A piston connected to a piston rod is fitted into a sealed cylinder in which a hydraulic fluid is contained. During an extension stroke of the piston rod, the hydraulic fluid in an upper cylinder chamber flows to a lower cylinder chamber through an extension-side hydraulic fluid passage, an extension-side orifice hydraulic fluid passage, an extension-side back-pressure chamber, an axial hydraulic fluid passage, a radial hydraulic fluid passage, a compression-side back-pressure chamber, an extension-side check valve and a compression-side hydraulic fluid passage.

Abstract: There is provided with a cylinder apparatus comprising: a cylinder; a piston; a piston rod, one end of which is connected to the piston and the other end of which is extended outside; an external cylinder provided at an outer periphery of the cylinder so as to form a reservoir in which to seal the hydraulic liquid and gas therebetween; a base valve dividing the second chamber and the reservoir; a first check valve provided with the piston so as to allow flow of the hydraulic liquid only from the second chamber side to the first chamber side; a second check valve provided with the base valve so as to allow flow of the hydraulic liquid only from the reservoir side to the second chamber side; a flow passage connecting the first chamber with the reservoir; and an opening and closing valve opening and closing the flow passage.

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: A hydraulic shock absorber in which the flow of hydraulic fluid induced in each of extension and compression hydraulic fluid passages, by sliding movement of a piston, is controlled by a main disk valve to generate damping force. The valve opening pressure of the main disk valve is adjusted by the pressure in a back-pressure chamber. In a low piston speed region, the main disk valve closes a back-pressure chamber inlet passage. Therefore, the pressure in the backpressure chamber will not rise, and sufficiently small damping force is obtained. When the main disk valve opens, the backpressure chamber inlet passage opens simultaneously. Consequently, the pressure in the backpressure chamber rises, and the damping force increases.