JPH084818A - Damping force adjusting type oil pressure buffer - Google Patents

Abstract

PURPOSE:To directly control damping force irrespective of a piston speed. CONSTITUTION:A piston to which a piston rod 4 is connected is fitted to the inside of a cylinder wherein oil liquid is sealed. Cylinder upper and lower chambers 2a, 2b are allowed to communicate with each other by extension side and contraction side passages 6, 7 and disk valves 9, 11 are provided therein. Back pressure chambers 20, 21 are provided on the rear face sides of the disk valves 9, 11, and pressure oil in the cylinder upper and lower chambers 2a, 2b are induced via orifices 28, 31 by back pressure passages 26, 29. A pressure control valve 32 is provided in the back pressure passage 29. When the piston 3 is moved, the disk valves 9, 11 are opened with opening degrees in accordance with pressure of the cylinder upper and lower chambers 2a, 2b and the back pressure chambers 20, 21 to generate damping force. Through adjustment of relief pressure of the pressure control valve 32 by means of an electric current applied to a proportional solenoid, the damping force on the extension side and contraction side can be directly controlled irrespective of a piston speed.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force adjustable hydraulic shock absorber mounted on a suspension system of a vehicle such as an automobile.

[0002]

2. Description of the Related Art In a hydraulic shock absorber mounted on a suspension system of a vehicle such as an automobile, a damping force can be appropriately adjusted in order to improve ride comfort and steering stability in accordance with road surface conditions, running conditions and the like. There is a damping force adjustable hydraulic shock absorber.

In this type of hydraulic shock absorber, a piston, to which a piston rod is connected, is slidably fitted in a cylinder in which an oil liquid is sealed, and two chambers in the cylinder are defined by the piston. Is connected to the main oil liquid passage and the bypass passage, and a damping force generating mechanism (orifice, disk valve, etc.) for generating a large damping force is provided in the main oil liquid passage,
In the bypass passage, a damping force generating mechanism having a small damping force and a damping force adjusting valve for opening and closing the bypass passage are provided.

With this configuration, when the damping force adjusting valve is opened, the oil liquid in the cylinder mainly flows through the bypass passage due to the sliding of the piston due to the expansion and contraction of the piston rod, and the small damping force is applied to both the expansion side and the compression side. Occurs, and the damping force characteristic becomes a soft characteristic. Also, when the damping force adjusting valve is closed, due to the piston sliding as the piston rod expands and contracts, the oil liquid in the cylinder flows only through the main oil liquid passage and a large damping force is generated on both the expansion side and the contraction side. The damping force characteristic becomes a hard characteristic. In this way, the damping force characteristic can be switched by opening and closing the damping force adjusting valve.

By selecting the damping force characteristic on the soft side during normal running of the vehicle, the vibration due to the unevenness of the road surface can be absorbed and the riding comfort can be improved.
By selecting the damping force characteristics on the hard side during turning, acceleration, braking, and high-speed traveling, it is possible to suppress changes in the posture of the vehicle body and improve steering stability.

Further, the applicant of the present invention has found that a disc valve for controlling the flow of the oil liquid in the main oil liquid passage, a back pressure chamber for exerting a pressure in the valve closing direction on the disc valve, and an upstream side of the main oil liquid passage. A disc valve opening pressure is provided by providing a back pressure passage that connects the cylinder chamber and the back pressure chamber, and a shutter that opens and closes the back pressure passage, and changes the pressure introduced into the back pressure chamber by opening and closing the shutter. Has been proposed so that a single disc valve can obtain a plurality of damping force characteristics (see Japanese Patent Laid-Open No. 2-51637).

Further, a damping force adjusting hydraulic shock absorber is combined with a controller and an actuator to automatically switch the damping force in real time according to road conditions, running conditions, etc., thereby improving riding comfort and steering stability. There is a suspension control device.

[0008]

However, there are the following problems in the above-described conventional damping force adjusting hydraulic shock absorber.
In the case where the passage area of the bypass passage is adjusted, since the passage area of the bypass passage set by the damping force adjusting valve is fixed, the damping force changes according to the magnitude of the piston speed. Also, in the case where the disc valve opening pressure is adjusted by the pressure in the back pressure chamber, the pressure in the cylinder chamber rises as the piston speed increases, and the pressure in the back pressure chamber also rises. The damping force changes accordingly. That is, the conventional damping force adjustment type hydraulic shock absorber adjusts the damping coefficient with the piston speed as a variable, and cannot directly control the damping force.

Therefore, when the damping force control is applied to the suspension control device as described above, first, the piston speed of the hydraulic shock absorber is detected so that a desired damping force is generated with respect to the input of the piston speed. Calculate the damping coefficient,
Further, it is necessary to take a procedure of driving the actuator so that the damping force adjusting valve has an opening degree corresponding to the calculated damping coefficient. As a result, the load on the control circuit becomes heavy, and it becomes difficult to quickly switch the damping force according to changes in road conditions and running conditions.

The present invention has been made in view of the above points, and an object of the present invention is to provide a damping force adjustable hydraulic shock absorber capable of directly controlling the damping force regardless of the piston speed.

[0011]

In order to solve the above-mentioned problems, a damping force adjusting hydraulic shock absorber of the present invention is provided with a cylinder in which an oil liquid is sealed and a slidable fit in the cylinder. A piston defining the inside of the cylinder into two cylinder chambers, a piston rod having one end penetrating the piston and being connected to the piston and the other end extending to the outside of the cylinder, and the two cylinder chambers provided in the piston. Communicating passage, a disc valve provided in the communicating passage for receiving the pressure of the one cylinder chamber to open the valve to generate a damping force, and a disc valve provided on the back side of the disc valve for closing the valve. And a back pressure passage that is provided along the piston rod and connects the back pressure chamber and the one cylinder chamber via an orifice, and the pressure of the back pressure chamber can be set arbitrarily. The hydraulic fluid in the back pressure chamber when it reaches a set pressure and relief to the other cylinder chamber, characterized by comprising a pressure control valve for controlling the pressure of the back pressure chamber.

[0012]

With this structure, the oil liquid in one of the cylinder chambers flows through the communication passage to the other cylinder chamber due to the movement of the piston accompanying the expansion and contraction of the piston rod, depending on the opening degree of the disc valve. A damping force is generated.
At this time, the oil liquid in one of the cylinder chambers is introduced into the back pressure chamber through the back pressure passage to urge the disc valve in the valve closing direction. Then, the disc valve is bent and opened to a position where the pressure on one cylinder chamber side of the communication passage and the elastic force of the disc valve and the pressure of the back pressure chamber are balanced, and the disc valve is opened according to the pressure of one cylinder chamber. Determine the damping force. Therefore, by adjusting the set pressure of the pressure control valve to control the pressure in the back pressure chamber, the damping force can be directly controlled regardless of the piston speed.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

The first embodiment will be described with reference to FIG. As shown in FIG. 1, the damping force adjustable hydraulic shock absorber 1 is
A piston 3 is slidably fitted in a cylinder 2 in which oil liquid is sealed.
The inside is divided into two chambers, a cylinder upper chamber 2a and a cylinder lower chamber 2b. One end side of a piston rod 4 which will be described later is connected to the piston 3, and the other end side of the piston rod 4 is inserted into a rod guide and an oil seal (not shown) attached to the end portion of the cylinder 2. It extends to the outside of the cylinder 2. Further, the cylinder 2 has a reservoir (not shown) for compensating the volume change in the cylinder 2 due to the expansion and contraction of the piston rod 4 by compressing and expanding gas.
Is connected. In the figure, 5 is a piston ring.

The piston 3 is provided with a plurality of expansion-side communication passages 6 and compression-side communication passages 7 for communicating the cylinder upper chamber 2a and the cylinder lower chamber 2b, respectively (one each shown) along the circumferential direction. ing. The extension side communication passage 6 is opened at the outer peripheral portion of the end surface of the piston 3 on the cylinder upper chamber 2a side,
The cylinder lower chamber 2b side is opened to the inner peripheral portion of the end surface of the piston 3. The compression side communication passage 7 is opened on the cylinder upper chamber 2a side on the inner peripheral portion of the end surface of the piston 3, and on the cylinder lower chamber 2b side is opened on the outer peripheral portion of the end surface of the piston 3.

On the end surface of the piston 3 on the cylinder lower chamber 2b side, an annular valve seat 8 is projectingly provided on the inner and outer circumferences across the opening of the extension side communication passage 6 so as to face the valve seat 8. Annular disc valves 9 are stacked. An annular valve seat 10 is projectingly provided on the inner and outer circumferences of the piston 3 on the end surface on the cylinder upper chamber 2a side across the opening of the compression side communication passage.
An annular disc valve 11 is laminated so as to face 10.

The disc valve 9 receives the pressure on the cylinder upper chamber 2a side of the extension side communication passage 6 and bends on the outer peripheral side to open the valve, and controls the flow of the oil liquid to provide a damping force according to the opening degree. The oil is generated, and the flow of the oil liquid in the opposite direction is blocked. Similarly, the disc valve 11 receives the pressure on the cylinder lower chamber 2b side of the compression side communication passage 7 and bends on the outer peripheral side to open the valve, and controls the flow of the oil liquid to generate a damping force according to the opening degree. In addition, the oil liquid is prevented from flowing in the opposite direction.

Cylindrical cases 14 and 15 having a bottom are stacked on the back sides of the disc valves 9 and 11 via annular retainers 12 and 13 which come into contact with the inner peripheral portions of the disc valves 9 and 11, respectively. Has been. Annular seal members 16 and 17 whose one ends are in liquid-tight contact with the disc valves 9 and 11 are slidably fitted in the openings of the cases 14 and 15, respectively. Seal member 1
6 and 17 are constantly pressed against the disk valves 9 and 11 by the springs 18 and 19, and the cases 14 and 15 and the seal member 1 are
By 6 and 17, expansion side and contraction side back pressure chambers 20 and 21 are formed on the back side of the disk valves 9 and 11.

The piston rod 4 comprises a passage member 22, a valve member 23 and a rod 24. Passage member 22
The small diameter part on the tip side is the piston 3, the disc valves 9, 11, the retainers 12, 13, the springs 18, 19, and the case 14,
The nut 25 is inserted into the nut 15, and the nut 25 is screwed to the tip end of the nut 25 so that they are integrally coupled and connected to the piston 3. Then, one end of the valve member 23 is coupled to the large diameter portion on the base end side, and the other end of the valve member 23 is connected to the rod.
24 is coupled, and the rod 24 is inserted into the rod guide and the oil seal (not shown) described above, so that the cylinder 2
Has been extended to outside.

The passage member 22 is provided with a back pressure passage 26 which communicates with the extension side back pressure chamber 20 and the contraction side back pressure chamber 21 via the passages 12a and 13a provided in the retainers 12 and 13, respectively. The back pressure passage 26 extends along the piston rod 4 and has one end through a check valve 27 and an orifice 28 that allow only the flow of oil liquid from the cylinder lower chamber 2b to the back pressure passage 26. 2b, and the other end communicates with a back pressure passage 29 provided in the valve member 23.

The back pressure passage 29 of the valve member 23 is communicated with the cylinder upper chamber 2a through a check valve 30 and an orifice 31 which allow only oil liquid to flow from the cylinder upper chamber 2a to the back pressure passage 29. There is. In the valve member 23, the pressure oil in the back pressure passage 29 is relieved to relieve the pressure in the back pressure passages 26, 29, that is, the back pressure chambers 20, 21.
A pressure control valve 32 for controlling the pressure of the oil liquid is provided.

The pressure control valve 32 has a relief chamber 34 that communicates with the back pressure passage 29 through a communication passage 33a provided in the valve seat 33.
A needle 35 (valve body) is movably guided inside,
The back pressure passage 29 that has reached a predetermined pressure by moving the needle 35 forward and backward to open and close the communication passage 33a of the valve seat 33 (open and close the orifice formed between the tapered portion of the needle 35 and the communication passage 33a). The pressure oil inside is relieved to the relief chamber 34. One end of an operating rod 36 is connected to the needle 35, the operating rod 36 is inserted into the rod 24, and the other end side is connected to a plunger (not shown) of a proportional solenoid provided outside the rod 24. There is. This proportional solenoid generates a constant thrust force according to a current supplied regardless of the displacement of the plunger. As described above, the pressure control valve 32 constitutes a proportional pressure control valve capable of arbitrarily adjusting the set pressure by changing the energizing current. The proportional solenoid may be provided inside the rod 24. In FIG. 1, 37 is a guide member for guiding the operating rod 36, and 38 is a seal member.

The needle 35 is provided with springs 39 and 40, the spring force of the spring 40 at the valve closing position is set stronger than the spring force of the spring 39, and is biased in the valve opening direction. It is possible to freely adjust the set pressure of the pressure control valve 32 by moving the solenoid to the closed position by energizing the solenoid and changing the valve opening pressure according to the energized current.

The valve member 23 is provided with drain passages 41 and 42 communicating with the relief chamber 34 of the pressure control valve 32.
The drain passage 41 communicates with the cylinder upper chamber 2a via a check valve 43 that allows only the oil liquid to flow from the relief chamber 34 to the cylinder upper chamber 2a. The drain passage 42 communicates with a passage 44 provided in the passage member 22, and further communicates with the cylinder lower chamber 2b through a passage 45 provided in the piston 3. Further, the drain passage 42 is provided with a check valve 46 that allows only the flow of the oil liquid from the relief chamber 34 side to the cylinder lower chamber 2b side.

The operation of the first embodiment constructed as above will be described below.

During the extension stroke of the piston rod 4, the movement of the piston 3 pressurizes the oil liquid in the cylinder upper chamber 2a to close the disc valve 11 to close the contraction side communication passage 7 and the extension side communication passage 6. Then, the disc valve 9 is opened to flow into the cylinder lower chamber 2b. At this time, the disc valve 9
Receives the pressure on the cylinder upper chamber 2a side and opens the valve to generate a damping force according to the opening degree.

Further, the pressure oil in the cylinder upper chamber 2a is a check valve.
30 is opened, the pressure is appropriately reduced by the orifice 31, and the pressure is introduced into the back pressure passage 29 and the back pressure passage 26. Here, the orifice 31 is configured so that the cylinder upper chamber 2a
Prevents the oil liquid from flowing to the cylinder lower chamber 2b via the back pressure passage 29, the relief chamber 34, the check valve 46, the drain passage 42, the passage 44, and the passage 45, and substantially only the pressure in the cylinder upper chamber 2a is prevented. To guide the back pressure passage 29. Further, the check valve 27 is closed from the back pressure passage 26 and introduced into the back pressure chamber 20 to urge the disc valve 9 in the valve closing direction. Here, the pressure of the back pressure chamber 20,
That is, when the pressure in the back pressure passages 26, 29 reaches the set pressure of the pressure control valve 32, the needle 35 retracts to move the back pressure passages 26, 29.
Since the pressure oil inside is relieved to the cylinder lower chamber 2b via the relief chamber 34, the check valve 46, the drain passage 42, the passage 44 and the passage 45, the pressure in the back pressure chamber 20 is the current supplied to the proportional solenoid. Can be arbitrarily set by adjusting the set pressure of the pressure control valve 32.

The disc valve 9 has the pressure on the cylinder upper chamber 2a side in the extension side communication passage 6 and the disc valve 9
The valve opens by flexing to a position where the elastic force of and the pressure in the back pressure chamber 20 are balanced. In this way, the cylinder upper chamber 2a
The damping force is determined by changing the passage area of the extension side communication passage 6 in accordance with the pressure. Therefore, a predetermined damping force is generated according to the current supplied to the proportional solenoid regardless of the piston speed.

During the compression stroke of the piston rod 4, the movement of the piston 3 pressurizes the oil liquid in the cylinder lower chamber 2b, closing the disc valve 9 to close the extension side communication passage 6 and the compression side communication passage 7. Through, the disc valve 11 is opened to flow to the cylinder upper chamber 2a. At this time, the disc valve
The valve 11 is opened by receiving the pressure on the cylinder lower chamber 2b side and generates a damping force according to the opening degree.

The hydraulic pressure in the cylinder lower chamber 2b is controlled by the check valve.
27 is opened, the pressure is appropriately reduced by the orifice 28, and the pressure is introduced into the back pressure passage 26 and the back pressure passage 29. Here, the orifice 28 is configured so that the cylinder lower chamber 2b
It prevents the oil liquid from flowing to the cylinder upper chamber 2a via the back pressure passage 26, the relief chamber 34, and the check valve 43, and substantially guides only the pressure of the cylinder lower chamber 2b to the back pressure passage 29. To do.
Further, the check valve 30 is closed from the back pressure passage 26 and the back pressure passage 29 to be introduced into the back pressure chamber 21, and the disc valve 11 is biased in the valve closing direction. Here, when the pressure in the back pressure chamber 21, that is, the pressure in the back pressure passages 26, 29 reaches the set pressure of the pressure control valve 32, the needle 35 retracts and the pressure oil in the back pressure passages 26, 29 relieves. Since the cylinder upper chamber 2a is relieved through the chamber 34, the check valve 43 and the drain passage 41, the pressure in the back pressure chamber 21 is
It can be arbitrarily set by adjusting the set pressure of the pressure control valve 32 by the current supplied to the proportional solenoid.

The disc valve 11 has the pressure on the cylinder lower chamber 2b side in the compression side communication passage 7 and the disc valve 11
The valve is opened by bending to a position where the elastic force of the pressure and the pressure in the back pressure chamber 21 are balanced. In this way, the cylinder upper chamber 2a
The damping force is determined by changing the passage area of the extension side communication passage 6 in accordance with the pressure. Therefore, a predetermined damping force is generated according to the current supplied to the proportional solenoid regardless of the piston speed.

As described above, by adjusting the set pressure of the pressure control valve 32 by the current supplied to the proportional solenoid, it is possible to directly control the extension side and the contraction side damping forces regardless of the piston speed.

The damping force characteristics in this case are, as shown in FIG. 2, that when the current supplied to the proportional solenoid is small, the set pressure of the pressure control valve 32 is low, and the damping forces on the extension side and the contraction side are small. Become. Then, as the energizing current is increased, the set pressure is increased and the damping force is increased. In this way, the damping force can be continuously adjusted according to the applied current. FIG. 2 shows, as an example, the relationship between the piston speed and the damping force when the current supplied to the proportional solenoid is changed in 10 steps from 0.1 A to 1.0 A.

In this embodiment, the pressure control valve 32 adjusts the set pressure by moving the needle 35 at the valve opening position to the valve closing position by the thrust of the proportional solenoid by the springs 39 and 40. However, the needle 35 may be urged in the valve closing direction by the springs 39 and 40 so that the thrust force of the solenoid acts in the valve opening direction so that the set pressure is adjusted according to the energized current. In this case, when the proportional solenoid does not operate due to disconnection or the like, the set pressure of the pressure control valve 32 becomes maximum and the damping force can be fixed to the hard side.

Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment has substantially the same structure as the first embodiment except that the structures of the back pressure passage and the check valve thereof are different. Therefore, the same members as those of the first embodiment will be described below. Are assigned the same numbers, and only different portions will be described in detail.

As shown in FIG. 3, the damping force adjusting hydraulic shock absorber 47 of the second embodiment is a case 1 which is connected to the piston 3.
The bottomed tubular passage members 48 and 49 are superposed on the outer casings 4 and 15 and are fitted to the outside, and the chamber 48a is provided between the case 14 and the passage members 48 and 49.
, 49a are formed. Also, the piston rod 4
Is composed of a rod 24 and a valve member 50. The valve member 50 has a small diameter portion formed at both ends and a large diameter portion formed at an intermediate portion, and the small diameter portion on the tip end side includes the piston 3, the disc valves 9, 11, the retainers 12, 13, and the springs 18, 19. The nuts 25 are inserted into the cases 14 and 15 and the passage members 48 and 49, and the nuts 25 are screwed to the distal ends thereof, so that they are integrally coupled and connected to the piston 3. The rod 24 is connected to the small diameter portion on the base end side.

The valve member 50 is provided with a back pressure passage 51 communicating with the extension side back pressure chamber 20 and the contraction side back pressure chamber 21 via the passages 12a, 13a provided in the retainers 12, 13.
The back pressure passage 51 communicates with the chamber 48a through the orifice 52, and further, the chamber 48a is connected from the cylinder lower chamber 2b side to the chamber 48a.
It is communicated with the lower cylinder chamber 2b via a check valve 53 that allows only the flow of the oil liquid to the a side. Further, the chamber 49a is communicated with the chamber 49a through an orifice 54, and the chamber 49a is connected through a check valve 55 which allows only the flow of the oil liquid from the cylinder upper chamber 2a side to the chamber 49a side. It is connected to 2a.

The valve member 50 is connected to one end of the back pressure passage 51, and the pressure oil in the back pressure passage 51 is relieved to relieve the back pressure chamber 20,
A pressure control valve 32 for adjusting the pressure of 21 is provided. Further, the drain passage 56 for communicating the relief chamber 34 of the pressure control valve 32 with the cylinder upper chamber 2a and the relief chamber 34 for the cylinder lower chamber
A drain passage 57 communicating with 2b is provided. Further, the drain passage 56 is provided with a check valve 58 which allows only the flow of the oil liquid from the relief chamber 34 side to the cylinder upper chamber 2a side, and the drain passage 57 is provided with a check valve from the relief chamber 34 side to the cylinder lower side. A check valve 59 that allows only the flow of the oil liquid to the chamber 2b side is provided.

The operation of the present embodiment configured as described above will be described below.

During the extension stroke of the piston rod 4, the high pressure oil liquid on the cylinder upper chamber 2a side flows to the cylinder lower chamber 2b side through the extension side communication passage 6 and is attenuated according to the opening degree of the disc valve valve 9. Power is generated. Also, the cylinder upper chamber 2a
Back pressure passage through the check valve 55 and orifice
51 is introduced into the back pressure chamber 20 by closing the check valve 53 to urge the disc valve 9 in the valve closing direction. When the pressure of the pressure oil in the back pressure passage 51 reaches the set pressure of the pressure control valve 32, the needle 35 retracts and the relief chamber 34, the check valve.
Cylinder lower chamber with low pressure through 59 and drain passage 57
Relieved to 2a.

During the compression stroke of the piston rod 4, the high pressure oil liquid on the cylinder lower chamber 2b side flows through the compression side communication passage 7 to the cylinder upper chamber 2a side, and the damping force corresponding to the opening degree of the disc valve 11 is increased. Occurs. Further, the pressure oil in the cylinder lower chamber 2b is introduced into the back pressure passage 51 via the check valve 53 and the orifice 52, and further, the check valve 55 is closed to be introduced into the back pressure chamber 21, so that the disc valve 11 is closed. Energize in the valve closing direction. Back pressure passage
When the pressure of the pressure oil in 51 reaches the set pressure of the pressure control valve 32, the needle 35 retracts and the pressure oil in the cylinder upper chamber 2a becomes low pressure via the relief chamber 34, the check valve 58 and the drain passage 56. To be done.

As in the first embodiment, the opening degrees of the disc valves 9 and 11 are changed according to the pressures in the cylinder upper chamber 2a and the cylinder lower chamber 2b to determine the damping force. Pressure control valve
By adjusting the set pressure of 32, the damping force on the extension side and the compression side can be directly controlled regardless of the piston speed.

[0043]

As described above in detail, according to the damping force adjusting type hydraulic shock absorber of the present invention, by adjusting the set pressure of the pressure control valve, the pressure of the back pressure chamber can be adjusted according to the set pressure. Since the opening degree of the disc valve changes and the opening degree of the disc valve is determined according to the pressure in the back pressure chamber and the pressure in one of the cylinder chambers, the damping force can be directly controlled regardless of the piston speed. As a result, when applied to a suspension device, the damping force can be controlled directly without the need to detect the piston speed, which has the excellent effect of reducing the load on the controller and enabling quick and appropriate damping force adjustment. Play.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a first embodiment of the present invention.

FIG. 2 is a diagram showing damping force characteristics of the device of FIG.

FIG. 3 is a vertical cross-sectional view of a main part of a second embodiment of the present invention.

[Explanation of symbols]

 1 Damping force adjustable hydraulic shock absorber 2 Cylinder 2a Cylinder upper chamber 2b Cylinder lower chamber 3 Piston 4 Piston rod 6 Expansion side communication passage 7 Compression side communication passage 9,11 Disc valve 20,21 Back pressure chamber 26,29 Back pressure passage 28,31 Orifice 32 Pressure control valve 47 Damping force adjustable hydraulic shock absorber 51 Back pressure passage 52,54 Orifice

Claims (1)

[Claims] 1. A cylinder in which an oil liquid is sealed, a piston which is slidably fitted in the cylinder and defines two cylinder chambers in the cylinder, and one end of which penetrates and is connected to the piston. A piston rod having an end extending to the outside of the cylinder, a communication passage provided in the piston for communicating the two cylinder chambers, and a valve opened by receiving the pressure of the one cylinder chamber provided in the communication passage Disc valve for generating damping force, a back pressure chamber provided on the back side of the disc valve for exerting pressure in the valve closing direction, the back pressure chamber provided along the piston rod and the one cylinder. A back pressure passage that communicates with the chamber via an orifice, and when the pressure in the back pressure chamber reaches a settable pressure that can be set arbitrarily, the oil liquid in the back pressure chamber is relieved to the other cylinder chamber and Pressure A damping force adjusting hydraulic shock absorber, comprising: a pressure control valve for controlling the pressure in the chamber.