JPH10281208A - Hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic buffer to maintain quality of hydraulic oil by removing a detecting spring always operated in an oil chamber to prevent mixture of a foreign matter in hydraulic oil in a hydraulic buffer through a detecting spring and perform regulation of damping force switching sensitivity depending upon a position and perform smooth continuous switching. SOLUTION: A hydraulic buffer comprises a differential pressure cylinder 2 located differently from a buffer; a gas chamber E or F partitioned by a piston 22 slidably inserted in a fitted in state in the differential pressure cylinder 2; a continuity means 3 to intercommunicate a reservoir R and a gas chamber G; a return spring 26 to energize the piston 22 of the differential pressure cylinder 2 into a neutral state: and a coupling means 4 to intercouple the piston rod 24 of the differential pressure cylinder 2 and a damping force switching mechanism 4. A damping force is regulated according to the pressure change of the reservoir R depending on the position of the piston rod 15 of the buffer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber suspended as a suspension system for a vehicle such as a four-wheeled vehicle, and more particularly, to a position-dependent damper capable of switching a damping force in relation to a vehicle height of the vehicle. The present invention relates to a force-adjustable hydraulic shock absorber.

[0002]

2. Description of the Related Art A conventional hydraulic shock absorber of this type is disclosed, for example, in FIG. 2 of Japanese Patent Publication No. 62-27294, which will be described. The hydraulic shock absorber includes an expansion damping valve that allows only the flow from the upper chamber to the lower chamber during extension operation between a sleeve that is slidable relative to the piston and the piston, and an upper damping valve that moves from the lower chamber to upper during compression operation. A compression-side damping valve that allows only the flow to the chamber is arranged in parallel, and a constant port and a variable port are arranged side by side in the middle of the upstream passage of the extension-side damping valve. A plurality of switching ports are provided in parallel with each other, and these variable ports and the switching ports are displaced in accordance with a relative position change of the piston by a spring interposed between the piston rod bearing and the piston. It is configured to open and close via a sleeve provided so as to operate.

[0003]

In the above-described hydraulic shock absorber, a detection spring is disposed in an upper oil chamber which is a pressure oil chamber, and the detection spring is moved in accordance with extension of a piston rod of the shock absorber. When compressed, torsion occurs at this time at both ends of the detection spring with the locking members at both ends. When sliding with this torsional movement,
At the center of the detection spring, the inner circumference of the inner cylinder buckles and comes into contact with each other, causing friction to occur. As a result, an abnormal sliding sound is generated, which causes discomfort to the occupants. Wear powder generated by friction contaminates hydraulic oil, and wear powder enters a main sliding portion such as a piston, starting from the fact that the wear powder blocks fine passages and causes an effect on damping characteristics. There is a problem that the abrasion of the parts is accelerated, and not only the performance is reduced but also the sealing performance is remarkably reduced due to the action on the oil seal portion, so that it is difficult to maintain the quality.

Further, as the piston rod is extended, the detection spring is compressed, and the damping force is always switched at a predetermined amplitude or more. Fluctuations always occur to reduce the continuity of the damping force, which leads to deterioration of the flooring during riding.
Furthermore, the detection spring is arranged in series with the piston for position detection and damping switching. Therefore, the maximum contraction length of the detection spring is longer than the dead dimension (minimum contraction length) of the shock absorber. In other words, there is a problem that the vehicle is poorly equipped and the vehicles that can be equipped are limited.

[0005] Therefore, the present invention is directed to a foreign matter mixture (contamination) by a detection spring into hydraulic oil in a hydraulic shock absorber.
In order to avoid the problem, the detection spring that always works in the oil chamber is removed to maintain the quality of the hydraulic oil, and the damping force switching sensitivity can be adjusted depending on the position to obtain smooth and continuous switching. It is another object of the present invention to provide a hydraulic shock absorber having characteristics and a minimum contraction length more than conventional shock absorbers.

[0006]

According to a first aspect of the present invention, a reservoir formed by an inner and outer cylinder sealed by an upper and lower sealing member, a reservoir formed by the inner and outer cylinders, and a piston slidably housed in the inner cylinder. And an operating rod that penetrates the piston rod and is freely rotatably inserted through the piston rod. In a damping force adjusting type hydraulic shock absorber having a damping force switching mechanism that varies the area of the communication passage between the upper and lower oil chambers through an adjustment valve means, a differential pressure cylinder separately provided from the shock absorber and a differential pressure cylinder are provided. A gas chamber defined by a piston which is freely slidably inserted, communication means for communicating the reservoir with the gas chamber, a return spring for urging the piston of the differential pressure cylinder to a neutral state, Pressure cylinder piston rod and damping force switching mechanism Consists of a connecting means for forming, reservoir depending on the position of the piston rod of the shock absorber - adjusting the damping force in response to pressure changes in the bar.

In the second invention, the reservoir is a gas chamber or an oil chamber.

In the third invention, a throttle valve is provided in the communication means.

In a fourth aspect, a return spring is interposed in a differential pressure cylinder.

[0010] In the fifth invention, the regulating valve means has a substantially rhombus shape in which the communication hole is continuously reduced.

In the sixth invention, the differential pressure cylinder is installed near the hydraulic shock absorber.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is applied to a front wheel or a rear wheel of a vehicle (not shown), and includes a hydraulic shock absorber 1 mounted on each wheel and a differential pressure operated by a pilot pressure from the hydraulic shock absorber 1 as shown in FIG. It comprises a cylinder 2, a communicating means 3 for guiding pilot pressure to the differential pressure cylinder 2, a damping force switching mechanism 4 for switching damping force, and a connecting means 5 for connecting the differential pressure cylinder 2 and the damping force switching mechanism 4. ing.

The hydraulic shock absorber 1 is a return-cylinder type hydraulic shock absorber of a damping force adjustment type, having an inner cylinder 11 and an outer cylinder 12 each formed of a sealed cylinder. Are inserted and partitioned by the piston 13 into an upper oil chamber A and a lower oil chamber B.

A piston rod 15 projects upward from the piston 13 through sealing members 14 and 17 engaged with the upper end of the inner cylinder 11, and a lower end of the inner and outer cylinders 11 and 12 is
Is closed.

The protruding end 15a of the piston rod 15 is connected to a vehicle body (not shown), and the lower end 16a of the sealing member 16 is connected to a wheel side (not shown).

The inner cylinder 11 and the outer cylinder 12 are concentrically held by the first and second sealing members 14 and 17 at the upper part and by the sealing member 16 at the lower part. An oil chamber D and a gas chamber G are formed in the annular reservoir R formed by the above.

The first and second sealing members 14 on the upper part of the inner cylinder 11,
The space C defined by 17 communicates with the gas chamber G through a passage 17 a provided in the second sealing member 17, and the first sealing member 14 is fitted to the piston rod 15 and sealed. A sealing member 18 is disposed.

The piston 13 has an extension damping valve 1a for blocking the flow from the upper oil chamber A to the lower oil chamber B, and a first pressure-side damping valve 1b for blocking the flow from the lower oil chamber B to the upper oil chamber A. It is arranged.

A second pressure side damping valve 1c for blocking the flow from the lower oil chamber B to the oil chamber D of the reservoir R is provided at the lower end sealing member 16.
And a check valve 1d for allowing a flow from the oil chamber D of the reservoir R to the lower oil chamber B.

Further, a damping force switching mechanism 4 is provided at an upper end of the piston rod 15, and the damping force switching mechanism 4 is provided at a lower portion inside the piston rod 15 to communicate and cut off the upper oil chamber A and the lower oil chamber B. Thus, the adjusting valve means 19 is inserted.

The adjusting valve means 19 has an operating rod 19a rotatably inserted into a through hole 15a provided in the piston rod 15, and an adjusting valve 19b provided at an end of the operating rod 19a is integrally engaged therewith. As shown in FIG.
The hole 19c provided in the adjustment valve 19b and the through-hole 15c formed in the piston rod 15 are engaged with each other so as to communicate with each other and to shut off the hole 19c provided in the adjustment valve 19b with the rotation of the valve 9a.

The differential pressure cylinder 2 includes a cylinder 21 composed of a sealed cylinder, a piston 22 slidably inserted into the cylinder 21, a piston rod 24 integrally formed with the piston 22, a piston rod 24 and a cylinder. 21,
And a sealing member 25 for sealing the sealing member 23.

The inside of the cylinder 21 is divided into left and right gas chambers E and F by a piston 22 and gas is sealed therein.

One protruding end 24a of the piston rod 24
Is connected via a wire 5 which is a connecting means for connecting the damping force switching mechanism 4 to the damping force switching mechanism 4.
The piston 22 is held in a neutral position, and a spring 26 biased to correct the slack of the wire 5 is arranged to be engaged.

The left gas chamber E formed in the differential pressure cylinder 2
Is connected to the gas chamber G of the hydraulic shock absorber 1 by a conducting pipe 3 which is a communicating means, and a throttle 3a is provided in the conducting pipe 3.

The damping force switching mechanism 4, as shown in FIG.
A bracket 31 screwed to the end 15a of the piston rod 15, and a switching lever 32 engaged with an operation rod 19a inserted into a through hole 15b provided in the piston rod 15;
And a return spring 33 provided so as to engage one with the switching lever 32 and the other with the bracket 31 to urge the two, and a pin 34 provided at the end of the switching lever 32 so as to be freely rotatable. The wire 35 is a connected member that is engaged.

When the wire 5 is displaced, the switching lever 32 is rotated against the spring force of the return spring 33, and the operating rod 19a is rotated by the rotation of the switching lever 32. I have.

The right gas chamber F of the differential pressure cylinder 2 is set to have the same pressure as the left gas chamber E at the neutral position of the piston 22.

Next, the operation will be described. In the hydraulic shock absorber 1, when the hydraulic oil in the upper oil chamber A is compressed by the piston 13 during the extension operation in which the piston 13 is extended, the compressed hydraulic oil is supplied to the extension side provided in the piston 13. The damping valve 1a is operated to flow into the lower chamber B.

Piston rod 15 retreated from inner cylinder 11
Hydraulic oil corresponding to the volume of? Flows into the lower oil chamber B from the oil chamber D of the reservoir R via the check valve 1d.

The pressure resistance when passing through the extension side damping valve 1a acts as a damping force, and the hole 19c in the regulating valve means 19
When the oil and the hole 15c of the piston 15 communicate with each other, the operating oil flows through the communication holes 15c and 19c, so that the pressure resistance is smaller and the damping force is lower than when the communication holes 15c and 19c are closed. .

During the compression operation, the piston 13 is moved to the lower oil chamber B
When hydraulic fluid is compressed, most of the compressed hydraulic fluid is
The first pressure-side damping valve 1b provided on the piston 13 is operated to flow into the upper oil chamber A.

The piston rod 15 which has entered the inner cylinder 11
Of hydraulic oil flows into the reservoir R by operating the second pressure-side damping valve 1c.

At this time, the pressure resistance of the second compression-side damping valve 1c is greater than that of the first compression-side damping valve 1b, but the compression-side damping force is reduced by the first compression-side damping valve 1b and the second compression-side damping valve. The damping force is exerted as the sum of the valves 1c.

On the other hand, in the differential pressure cylinder 2, when the pressures of the left and right gas chambers E and F are in a neutral state, the piston 22 is held neutral by the springs 26 and 33, and the piston rod 24 is also Held in neutral position.

As the hydraulic shock absorber 1 expands and contracts, the pressure in the gas chamber G of the reservoir R fluctuates, and the pressure in the gas chamber E also rises and falls, so that the pressure parallel state of the left and right gas chambers E and F changes. When collapsed, an acting force corresponding to the pressure difference is generated, and the piston 22
Moves to a lower pressure side to the left or right, and the amount of movement is determined by the parallel condition of the acting force and the spring force.

When the piston 22 moves, the damping force switching mechanism 4 is actuated by the wire 5 connected at the end 24a of the piston rod 24, the operating rod 19a is rotated, and the adjusting valve means 19 moves between the holes 15c and 19c. The communication is closed and closed according to the amount of rotation.

Further, a description will be given of a case where the hydraulic shock absorber 1 is mounted on a suspension device (not shown). In the suspension device, the extension side and the compression side are respectively set on the basis of the state of a prescribed occupant (weight). The required displacement is set, and it operates according to the road surface condition and the inertial force of the vehicle body, and the displacement of the hydraulic shock absorber 1 is similarly set to the extension side and the compression side.

Now, the input from the road surface and the inertial force are small,
When the vehicle is traveling on a stable good road, the posture of the vehicle body and the operation of the wheels are stable, so that the hydraulic shock absorber 1 operates slowly and with a small amplitude near the prescribed neutral position.

The pressure in the gas chamber G of the hydraulic shock absorber 1 is guided to the gas chamber E of the differential pressure cylinder 2 through the conduit 3. , F maintain an equilibrium state, the piston 22 of the differential pressure cylinder 2 does not move, stays at that position, and the piston rod 2
4 also does not work at all.

Further, the damping force switching mechanism 5 does not operate via the wire 5 connected to the piston rod 24, and the neutral state is maintained.

Accordingly, the upper oil chamber A and the lower oil chamber B of the hydraulic shock absorber 1 maintain the communication state, and the damping force with respect to the piston speed is maintained low as shown in FIG.

On the other hand, when the vehicle body fluctuates greatly on a undulating road or a circuit, the internal pressure of the gas chamber G of the hydraulic shock absorber 1 increases due to the piston rod 15 entering the shock absorber 1 during the compression operation. In the extension operation, the piston rod 1
The internal pressure is reduced by the protrusion 5 protruding from inside the shock absorber 1.

Therefore, the pressure of the gas chamber G guided from the gas chamber G of the hydraulic shock absorber through the conduit 3 cannot be completely eliminated by the throttle 3a, and is reduced to the pressure of the left and right gas chambers E and F of the differential pressure cylinder 2. A difference occurs, and the piston 22 of the differential pressure cylinder 2 moves due to the pressure difference, and the piston rod 24 also moves.

For this reason, the damping force switching mechanism 5 is operated via the wire 5 connected to the piston rod 24, and moves from the neutral state to either the forward or backward state, and the upper oil chamber A and the lower oil chamber of the hydraulic shock absorber 1 are moved. The communication holes 15c and 19c communicating with B are closed by the adjusting valve means 19, and as shown in FIG. 4, a high damping force suitable for suppressing the operation of the wheels and the posture of the vehicle body is exerted as shown in FIG. You. In addition, on a rough road surface, the wheels operate at random and at an early cycle.

At this time, the hydraulic shock absorber 1 also operates irregularly like wheels, and the pressure in the gas chamber G of the shock absorber also fluctuates irregularly.

However, the conduction pipe 3 for introducing pressure from the gas chamber G of the hydraulic shock absorber 1 to the differential pressure cylinder 2 through the conduction pipe 3
The dynamic portion of the pressure in the gas chamber G can be eliminated by the throttle 3a provided therein and the pipe resistance due to the length, thickness, etc. of the conduction pipe, and the gas chamber guided to the differential pressure cylinder 2 The pressure in E is maintained at approximately the average neutral pressure.

Therefore, the piston 22 of the differential pressure cylinder 2 does not move, stays at that position, and the piston rod 24 does not move either.

For this reason, the damping force switching mechanism 5 of the hydraulic shock absorber 1
Thus, the neutral state is maintained, the adjustment valve means 19 is similarly maintained at the current state, the low damping force state is maintained, and good ride comfort can be secured.

As described above, the pressure in the reservoir R of the hydraulic shock absorber 1 is detected, and the detected pressure is introduced into the gas chamber E of the differential pressure cylinder 2 to determine the state of the vehicle height, and the damping is performed. Via the force switching mechanism 4 and the regulating valve means 19, an appropriate damping force corresponding to the vehicle height state and the operating amplitude of the shock absorber is selectively obtained.

Further, since a spring which easily generates abrasion powder is not stored in the shock absorber, but is stored in the differential pressure cylinder 2 installed outside, the spring buckles and makes an abnormal sliding noise. And the operating oil is not contaminated by the abrasion powder generated by the spring. Also, the abrasion powder does not block the micro passages to cause a change in characteristics, and the sealing performance of the seal member is reduced. And the quality of the shock absorber can be maintained.

Further, as the piston rod is extended, the detection spring is compressed, and the damping force is always switched at a predetermined amplitude or more. Fluctuations do not occur at all times, so that the continuity of the damping force is not reduced and the flooring is not deteriorated when riding.In addition, a detection spring is connected in series with the piston for position detection and damping switching. It is not configured to be disposed, so the dead dimension (minimum shrinkage length) of the shock absorber is shortened irrespective of the maximum shrinkage length of the detection spring, so that the vehicle can be equipped easily and can be equipped. Is not limited, and it is easy to suppress the variation in the attitude of the vehicle and the excessive movement of the wheels, thereby improving the contact with the ground and improving the stability and riding comfort of the vehicle.

Then, the displacement position of the shock absorber is detected by the pressure of the reservoir R and introduced into the differential pressure cylinder 2.
The pressure fluctuation in the reservoir R is used as a pressing force with the diameter of the differential pressure cylinder 2 to amplify the phenomenon, and the position can be easily determined.

Further, the reservoir due to the temperature rise of the hydraulic shock absorber
With respect to pressure fluctuations in the oil chamber, the gas chamber on one side of the differential pressure cylinder is used as a dummy, and the differential pressure cylinder is installed near the shock absorber to equalize the temperature to the reservoir chamber. Correction can be made for temperature changes.

FIG. 5A shows another embodiment of the present invention. In this embodiment, the first embodiment differs from the first embodiment.
The pilot pressure to the differential pressure cylinder is guided from the oil chamber D of the reservoir R of the hydraulic shock absorber, and a spring for holding the piston 22 of the differential pressure cylinder 2 at a neutral position is housed in the differential pressure cylinder 2. Therefore, the same configuration is omitted, and only the different configuration will be described.

An oil chamber D of a reservoir R formed of an annular space formed by an inner cylinder 11 and an outer cylinder 12 is connected to a chamber E of a differential pressure cylinder 2 by a conducting pipe 3 as a communicating means via a throttle 3a. The pressure in the reservoir R is communicated to the chamber E in the differential pressure cylinder 2.

Then, in the E and F chambers of the differential pressure cylinder,
A spring 2 is used to hold the piston 22 in the neutral position.
7, 28 are mounted, the spring does not come off or break due to an external force, and it is not rusted and deteriorated, so that the durability is excellent.

FIG. 5 (b) shows another embodiment of the differential pressure cylinder 2, which is a one-sided rod type cylinder in which the left and right pressure receiving areas of the piston 22a are different.
In order to hold 2a at the neutral position, springs 27 and 28 having different pressing forces are mounted in the left and right chambers E and F of the cylinder, and the pressure in the reservoir R is introduced into the chambers having different pressure receiving areas. The operating sensitivity of the piston can be changed.

Further, the pilot pressure from the oil chamber D of the reservoir R can be introduced into the chamber F of the differential pressure cylinder having a large pressure receiving area of the piston 22a.

FIG. 6 shows another embodiment of the regulating valve means 19, which is the same as that of the first embodiment.
In the present embodiment, the hole 19c provided in the regulating valve 19b and the hole 15c of the piston rod are fully opened to the hole 19b only at the time of neutrality, and the hole 15c of the piston rod 15 is closed when moving past neutral. Then, the shape of the hole 19d of the regulating valve 19 is made substantially rhombic so that the width at the center is the largest and the width decreases toward both sides, and the opening area of the hole passing through the hole 15c is changed continuously. The change in the damping force is made smooth.

[0061]

According to the first aspect of the present invention, there is provided a damping force-adjustable hydraulic shock absorber having a damping force switching mechanism for varying the area of the communication passage between the upper and lower oil chambers via an adjusting valve means provided on the operating rod. A differential pressure cylinder provided separately from the shock absorber, a gas chamber defined by a piston slidably inserted in the differential pressure cylinder, communication means for communicating the reservoir with the gas chamber, A return spring for urging the piston of the pressure cylinder to a neutral state, and a connecting means for connecting the piston rod of the differential pressure cylinder and the damping force switching mechanism, and a reservoir depending on the position of the piston rod of the shock absorber. -Since the damping force is adjusted according to the pressure change of the bar, the spring that easily generates abrasion powder is not stored in the shock absorber. Without spring The operating oil is not contaminated by the abrasion powder, and the abrasion powder does not block the minute passage to cause a change in characteristics, and the sealing performance of the seal member is not reduced. Quality and excellent durability.

Further, with the extension of the piston rod, the detection spring is compressed as in the conventional example, and the damping force is always switched at the amplitude greater than a predetermined value, and the damping force repeats in the vicinity of the switching. The change in the switching does not occur at all times, and does not reduce the continuity of the damping force, does not cause the deterioration of the flooring when riding, and furthermore, the detection spring is used for the position detection and the switching of the damping. Is not arranged in series with the piston. Therefore, the dead dimension (minimum shrinkage length) of the shock absorber can be designed irrespective of the maximum shrinkage length of the detection spring, and the equipment for the vehicle is improved. As a result, vehicles that can be equipped are no longer limited, and it is easier to suppress changes in vehicle attitude and excessive movement of wheels, improve ground contact, improve vehicle stability and ride comfort. There is an effect that can be improved.

According to the second aspect of the present invention, since the reservoir is a gas chamber or an oil chamber, the degree of the throttling effect for eliminating the dynamic part of the pressure transmitted from the reservoir to the differential pressure cylinder is reduced by the gas or oil chamber. You can choose either.

According to the third aspect of the present invention, since the throttle valve is provided in the communicating means, the opening degree of the throttle valve is adjusted by adjusting the opening degree of the throttle valve in accordance with the line resistance due to the length and thickness of the conduction pipe. The dynamic part of the pressure in the conduit can be moderately eliminated and the pressure in the gas chamber E led to the differential pressure cylinder can be kept at approximately the average of the fluctuating pressure.

According to the fourth aspect, since the return spring is interposed in the differential pressure cylinder, the return spring does not come off or be damaged by an external force,
In addition, it is not rusted and deteriorated, and the durability can be improved.

According to the fifth aspect of the present invention, the shape of the communication hole of the regulating valve is substantially rhombic in which the width at the center is largest and the width continuously decreases toward both sides. By changing the opening area continuously, it is possible to smoothly change the damping force.

According to the sixth aspect of the present invention, since the differential pressure cylinder is installed near the hydraulic shock absorber, the one-side gas chamber of the differential pressure cylinder is protected against pressure fluctuations in the reservoir oil chamber due to temperature rise. Is used as a dummy, and by installing a differential pressure cylinder near the shock absorber, the temperature can be made the same as that of the reservoir, and correction can be made for temperature changes.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a hydraulic shock absorber according to an embodiment of the present invention.

2 is a view similar to FIG. 1 showing a control valve A-
It is an arrow A line enlarged sectional view.

FIG. 3 is an enlarged perspective view of the damping force switching mechanism in FIG. 1;

FIG. 4 is a graph showing a damping force characteristic of the shock absorber at a piston speed.

FIG. 5 (a) is a front sectional view of a hydraulic shock absorber according to another embodiment. (B) It is a front sectional view of a differential pressure cylinder showing other embodiments.

FIG. 6 (a) is an enlarged front view of a main part of an adjustment valve showing another embodiment. (B) It is sectional drawing in the BB arrow line of the adjustment valve in FIG.6 (a).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic shock absorber 1a Expansion side damping valve 1b 1st compression side damping valve 1c 2nd compression side damping valve 1d Check valve 2 Differential pressure cylinder 3 Conduction path 3a Restriction 4 Damping force switching mechanism 5 Connecting member 11 Inner cylinder 12 Outer cylinder DESCRIPTION OF SYMBOLS 13 Piston 14 Sealing member 15 Piston rod 15a Projecting end 15b Through hole 15c hole 16 Sealing member 17 Sealing member 18 Seal member 19 Adjusting valve means 19a Operating rod 19b Adjusting valve 19c Hole 21 Cylinder 22 Piston 23 Sealing member 24 Piston rod 24a Left gas chamber 24b Right gas chamber 25 Seal member 26 Return spring 27,28 Spring 31 Bracket 32 Switching lever 33 Spring 34 Pin 35 Wire A Upper oil chamber B Lower oil chamber C Space D Oil chamber E Left gas chamber F Right gas chamber G Gas chamber R Reservoir

Claims (6)

[Claims] 1. A reservoir formed by an inner and outer cylinder sealed by an upper and lower sealing member, an inner and outer cylinder, an upper and lower oil chamber defined by a piston slidably housed in the inner cylinder, and a piston. A damping valve for imparting resistance to the hydraulic oil flowing out and in with the vertical movement of the operating rod, an operating rod penetrating through the piston rod and rotatably inserted, and an adjusting valve means provided on the operating rod to control the upper and lower oil chambers. In a damping force-adjustable hydraulic shock absorber having a damping force switching mechanism for varying the area of a communication passage, a damping force adjusting type hydraulic shock absorber is defined by a differential pressure cylinder separately provided from the shock absorber and a piston slidably inserted in the differential pressure cylinder. Gas chamber, communication means for communicating the reservoir with the gas chamber, a return spring for urging the piston of the differential pressure cylinder to a neutral state, a piston rod of the differential pressure cylinder, and a damping force switching mechanism. And connecting means for connecting Lisa depending on the position of the piston rod - hydraulic shock absorber, characterized in that to adjust the damping force in response to pressure changes in the bar. 2. The hydraulic shock absorber according to claim 1, wherein said reservoir is a gas chamber or an oil chamber. 3. The hydraulic shock absorber according to claim 1, wherein a throttle valve is provided in said communication means. 4. The hydraulic shock absorber according to claim 1, wherein said return spring is interposed in said differential pressure cylinder. 5. The hydraulic shock absorber according to claim 1, wherein said adjusting valve means has a substantially rhombic shape in which a communication hole is continuously reduced. 6. The hydraulic shock absorber according to claim 1, wherein the differential pressure cylinder is installed near a hydraulic shock absorber.