Abstract: The present invention provides a controllable damping force hydraulic shock absorber comprising a pilot type damping valve having a back-pressure chamber for each of an extension stroke and a compression stroke, which has a simple structure. 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: In the disclosed hydraulic shock absorber, 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 back-pressure chamber will not rise, and sufficiently small damping force is obtained. When the main disk valve opens, the back-pressure chamber inlet passage opens simultaneously. Consequently, the pressure in the back-pressure chamber rises, and the damping force increases.

Abstract: A piston having a piston rod connected thereto is slidably fitted in a cylinder in which a hydraulic fluid is sealably contained. Extension-stroke and compression-stroke pilot type damping force control mechanisms are provided in the piston. Check valves are provided at inlet openings of back-pressure chambers (pilot chambers). Relief valves provided in the pilot chambers include orifice passages. When the direction of stroke of the piston rod is reversed, the pressures in the back-pressure chambers are maintained due to the check valves, and the back-pressure chambers are pressurized to a satisfactory level through the orifice passages.

Abstract: A piston having a piston rod connected thereto is slidably fitted in a cylinder in which a hydraulic fluid is sealably contained. Extension-stroke and compression-stroke pilot type damping force control mechanisms are provided in the piston. A pilot control valve of the extension-stroke pilot type damping force control mechanism is formed by a pressure control valve having a valve seat, a valve body and a pressure-receiving portion. A pilot control valve of the compression-stroke pilot type damping force control mechanism is formed by a flow rate control valve having a spool. A slider having the valve body of the pressure control valve and the spool of the flow rate control valve is operated by a proportional solenoid, to thereby control a damping force for an extension stroke and a damping force for a compression stroke.

Abstract: A piston having a piston rod connected thereto is slidably fitted in a cylinder in which a hydraulic fluid is sealably contained. Extension-stroke and compression-stroke pilot type damping force control mechanisms are provided in the piston. A pilot control valve of the extension-stroke pilot type damping force control mechanism is formed by a pressure control valve having a valve seat, a valve body and a pressure-receiving portion. A pilot control valve of the compression-stroke pilot type damping force control mechanism is formed by a flow rate control valve having a spool. A slider having the valve body of the pressure control valve and the spool of the flow rate control valve is operated by a proportional solenoid, to thereby control a damping force for an extension stroke and a damping force for a compression stroke.

Abstract: A piston having a piston rod connected thereto is slidably fitted in a cylinder in which a hydraulic fluid is sealably contained. Extension-stroke and compression-stroke pilot type damping force control mechanisms are provided in the piston. Check valves are provided at inlet openings of back-pressure chambers (pilot chambers). Relief valves provided in the pilot chambers include orifice passages. When the direction of stroke of the piston rod is reversed, the pressures in the back-pressure chambers are maintained due to the check valves, and the back-pressure chambers are pressurized to a satisfactory level through the orifice passages.

Abstract: A piston connected with a piston rod is slidably fitted in a cylinder having a hydraulic fluid sealed therein. The piston rod extends to the outside of the cylinder through a rod guide fitted to an end portion of the cylinder. An annular seal member is inserted into an annular groove formed on the inner peripheral surface of the rod guide. The piston rod extends through the seal member. A wave washer is inserted into a gap between one end of the annular groove and the seal member. With its spring force, the wave washer urges the seal member to be pressed against the sealing surface of the annular groove. Because the seal member is constantly held in the state of being pressed against the sealing surface irrespective of the stroke direction of the piston rod, stable sealing performance can be obtained, and the leakage of hydraulic fluid can be surely prevented.

Abstract: The flow of a hydraulic fluid, which occurs under a sliding movement of a piston in a cylinder, is directly controlled by virtue of an extension-stroke pressure control valve and a compression-stroke pressure control valve. At the same time, the pressure in a back pressure chamber is varied, to thereby adjust the valve opening pressure for a main disk valve. This enables control of a damping force over a wide range. In each of the extension-stroke and compression-stroke pressure control valves, a thrust is generated in a slider due to a difference in pressure-receiving areas between a stepped portion of the slider and a sub disk valve in a valve chamber. The valve opening pressure is controlled, according to the balance between the thrust of the slider and a thrust of a proportional solenoid. By reducing the difference in the pressure-receiving areas in the valve chamber, the load applied to the proportional solenoid can be reduced.

Abstract: The flow of a hydraulic fluid between connecting ports caused by sliding movement of a piston in a cylinder is controlled by a fixed orifice and the flow path area determined by ports that is varied by a spool, thereby directly controlling orifice characteristics. At the same time, the pressure in a pilot chamber is changed by the pressure loss between the ports to change the valve opening pressure of a main valve, thereby controlling valve characteristics. An orifice passage is provided in parallel to the ports. Thus, when the flow path area determined by the ports is restricted, variations in the flow path area attributable to machining accuracy or the like can be absorbed by the flow path area of the orifice passage provided in parallel to the ports. Therefore, stable “hard” damping force characteristics can be obtained.

Abstract: A hydraulic shock absorber includes an inner cylinder filled with a working oil, an outer cylinder, and a reservoir defined between the inner and outer cylinders. A piston is slidably disposed within the inner cylinder so as to divide the interior of the inner cylinder into an upper cylinder chamber and a lower cylinder chamber. A piston rod is connected to the piston. A tubular member is disposed between the inner and outer cylinders and has a radial port. A damper mechanism is attached to the outer cylinder so as to control the flow of the working oil to produce a damping resistance. The outer cylinder includes a mounting projection with a substantially flat top surface on which the damper mechanism is secured. A sleeve has one end inserted into the port of the tubular member and the other, flanged end terminating at the top surface of the mounting projection. A first sealing element is secured between the sleeve and the port to provide a seal between the sleeve and the tubular member.

Abstract: A hydraulic shock absorber includes disc valves seated on valve seats, and annular retainer discs having a diameter less than that of the valve seat. The retainer discs are guided by spacers and axially separable from the disc valves. Annular seal discs are disposed downstream of the disc valves. The inner periphery of the seal discs is partly overlapped with the outer periphery of the retainer discs. The outer peripheral edge of the retainer discs is in substantially linear contact with the disc valves. This arrangement restricts frictional resistance between the disc valves and the retainer discs when the disc valves are flexed and opened.

Abstract: A damping force control type hydraulic shock absorber is provided having a broad damping force control range and is capable of obtaining appropriate damping force over the entire piston speed range from a low speed region to a high speed region. A piston is fitted in a cylinder, and a reservoir is connected to the cylinder. A cylinder upper chamber and the reservoir are communicated through a main passage in which a main damping valve is provided. The cylinder upper and lower chambers are communicated through an extension sub-passage in which an extension sub-damping valve and an extension variable orifice are provided. The cylinder lower chamber and the reservoir are communicated through a compression sub-passage in which a compression sub-damping valve and a compression variable orifice are provided.

Abstract: In a damping force control type hydraulic shock absorber, the flow path area of a port is changed by moving a spool according to an electric current supplied to an actuator, and thus the flow path area of a passage between cylinder upper and lower chambers is directly changed, thereby controlling orifice characteristics. Moreover, the pressure in a pilot chamber is changed according to the resulting pressure loss so as to change the valve opening pressure of a disk valve, thereby controlling valve characteristics. This enables the damping force characteristic control range to be widened. The pilot chamber is formed by the side wall of a valve member, the disk valve, a seal disk, and a seal member, also, the seal member has no sliding portion. It is therefore possible to minimize the leakage of hydraulic fluid and to obtain stable damping force characteristics. It is also possible to minimize variations in damping force with temperature changes.

Abstract: A piston is slidably fitted in a cylinder for dividing the interior of the cylinder into upper and lower cylinder chambers. The upper cylinder chamber communicates with the lower cylinder chamber through a check valve. The lower cylinder chamber communicates with a reservoir through a check valve. The upper cylinder chamber communicates with the lower cylinder chamber through an extending side damping valve. The lower cylinder chamber communicates with the reservoir through a contracting side damping valve. A piston rod is connected to the piston. When the piston rod is in an extending stroke, a damping force is generated by the extending side damping valve. When the piston rod is in a compressing stroke, a damping force is generated by the contracting side damping valve. The reservoir includes a connecting hole having an opening. A baffle plate is provided within the reservoir and above the opening of the connecting hole.

Abstract: A piston connected to a piston rod is slidably mounted in a cylinder, and a lower cylinder chamber is connected to a reservoir. An extension side passage for communicating an upper cylinder chamber with the lower cylinder chamber and a compression side passage for communicating the cylinder chamber with the reservoir are provided with disc valves, respectively, behind which extension side and compression side back pressure chambers are formed. The extension side back pressure chamber is communicated with the upper and lower cylinder chambers through a fixed orifice and ports. The compression side back pressure chamber is communicated with the lower cylinder chamber and the reservoir through a fixed orifice and ports. By rotating a shutter, flow areas of the ports are changed to adjust orifice features and pressures in the extension side and compression side back pressure chambers are changed to adjust valve features.

Abstract: A damping force control type hydraulic shock absorber has a damping force control mechanism adapted to generate damping force by controlling the flow of a hydraulic fluid sealed in a cylinder. Flow is induced by the extension and retraction of an operating rod inserted in the cylinder. The damping force control mechanism is further adapted to control the damping force by movement of its valve body. The damping force control mechanism is disposed on the side of the cylinder such that the direction of movement of the valve body is offset with respect to the center axis of the operating rod and crosses the center axis.

Abstract: A damping force control type hydraulic shock absorber has a piston that has main hydraulic fluid passages and valve mechanisms and also has a piston rod connected thereto. One side of the cylinder of the shock absorber is provided with a damping force control mechanism having a guide member and a shutter, which open and close a bypass passage, and a valve mechanism that generates damping force by controlling the flow of hydraulic fluid through the bypass passage. Damping force characteristics are changed by rotating the shutter with a rotary actuator. Since the damping force control mechanism is provided on the side of the cylinder and the piston is provided with only the main hydraulic fluid passages and the valve mechanisms, the size of the piston assembly is relatively small. Accordingly, the stroke of the piston rod can be increased.

Abstract: In a damping force control type hydraulic shock absorber according to the invention, an extension-side bypass passage extends through an extension-side chamber (17b) in a shutter (17). A check valve (28) allows the flow of hydraulic fluid only during the extension stroke. A contraction-side bypass passage extends through a contraction-side chamber (17a) in the same shutter (17). Disk valves (30) allow the flow of hydraulic fluid only during the contraction stroke. By rotating the shutter (17), alignment between an extension-side inlet port (31) and an extension-side inlet opening (34) changes and alignment between a contraction-side inlet port (32) and a contraction-side inlet opening (33) also changes, thereby controlling the passage area of each of the extension- and contraction-side bypass passages, and thus enabling different damping force characteristics to be simultaneously selected for the extension and contraction sides.

Abstract: A cylinder (7) having a hydraulic fluid sealed therein is fitted with a piston (8) having a piston rod (9) connected thereto. The piston rod (9) is provided with a bypass passage (B) (generating relatively small damping force). The passage area of the bypass passage (B) is controlled by varying the area of orifices formed by guide ports (21 and 22) and shutter ports (24 and 25) by rotating a shutter (23), thereby changing damping force characteristics. Auxiliary ports (34 and 35) are provided to open into the guide ports (21 and 22), respectively.

Abstract: A damping force control type of hydraulic shock absorber includes a cylinder in which a piston is fitted to define two chambers. A main hydraulic fluid passage extends between the chambers, and a damping force generating mechanism is provided in the passage. A bypass passage is also provided between the two chambers. Two check valves are provided in the bypass passage and allow hydraulic fluid to flow in opposite directions, respectively, through the bypass passage. A first hydraulic fluid passage bypasses the first check valve and a second hydraulic fluid passage bypasses the second check valve. A control valve is provided to vary the sectional area of each of the first and second hydraulic fluid passages.