JP2504423B2 - Variable damping force type hydraulic shock absorber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a damping force variable hydraulic shock absorber.

2. Description of the Related Art As a hydraulic shock absorber used for a suspension device of an automobile or the like,
There is known a so-called variable damping force type hydraulic shock absorber capable of adjusting the damping force of the hydraulic pressure shock absorber according to the running condition of an automobile or the like (for example, JP-A-60-196444).

This variable damping force type hydraulic shock absorber is a double cylinder type in which an outer cylinder is arranged outside the cylinder and a reservoir chamber is formed between the cylinder and the outer cylinder. The upper and lower liquid chambers are divided into two chambers, an upper liquid chamber and a lower liquid chamber, and the piston has a damping valve that operates during the extension stroke and the compression stroke to generate a damping force. With a variable orifice that adjusts the damping force of the damping valve,
The base valve arranged at the lower end of the cylinder includes a compression side damping valve that generates a damping force during the compression stroke, and a check valve that operates to open the valve during the extension stroke to allow liquid to flow from the reservoir chamber to the lower liquid chamber. It is trying to obtain a damping force according to the running condition of a car or the like.

Problems to be Solved by the Invention According to this conventional structure, the expansion side damping force generated when the liquid in the upper liquid chamber passes through the damping valve and flows into the lower liquid chamber during the stroke of the piston is generated in the piston. Can be variably set by the variable orifice installed. However, during the compression stroke of the piston, the damping valve installed on the piston and the compression-side damping valve installed on the base valve cooperate to generate a compression damping force. Therefore, when it is desired to increase the compression damping force, the damping force must be set in consideration of the damping force of the base valve, and the compression damping force cannot be arbitrarily set by the variable orifice installed on the piston. .
That is, even if you want to increase the compression side damping force by the variable orifice installed on the piston, if you do not variably set the damping force within the range where the pressure in the upper liquid chamber does not become negative pressure,
Since cavitation occurs in the upper liquid chamber, which causes abnormal noise and deterioration of riding comfort, there is a limit to increasing the compression-side damping force. It is also possible to change the compression damping valve of the base valve to a high damping type that generates a large damping force so that the pressure of the upper liquid chamber does not become negative pressure, but the damping force by the variable orifice installed on the piston is reduced. Even if it is selected, a high damping force is generated by the base valve, so that the damping force in the compression stroke cannot be reduced. Therefore, such a conventional technique has a problem that the variable width of the compression side damping force cannot be increased.
Therefore, an object of the present invention is to provide a damping force variable hydraulic shock absorber that solves such problems.

Means for Solving the Problems A piston defining an upper liquid chamber and a lower liquid chamber inside is housed in a cylinder, while a reservoir chamber is provided outside the cylinder between the cylinder and the cylinder. An outer cylinder to be formed is disposed, an expansion-side damping force generating means for generating a damping force by causing the liquid in the upper liquid chamber to be replaced and flown into the lower liquid chamber during the expansion process of the piston, and a compression of the piston. A piston check valve that allows the flow of liquid from the lower liquid chamber to the upper liquid chamber during the process is provided, and at the bottom of the cylinder, the liquid in the lower liquid chamber is replaced and flowed to the reservoir chamber during the compression process of the piston. Damping force generating means for generating a damping force by a compression force, and a damping force variable type liquid provided with a base check valve for allowing the liquid to flow from the reservoir chamber to the lower liquid chamber when the piston is extended. In the pressure buffer, a communication passage that connects the upper liquid chamber and the reservoir chamber is provided, and the communication passage is operated by the hydraulic pressure in the cylinder that changes according to the moving speed of the piston, And a dashpot mechanism for maintaining the operating position of the variable throttle during both the pressure-expanding steps.

Action During the stroke of the piston, the fluid pressure in the upper fluid chamber rises,
Since the hydraulic pressure in the lower liquid chamber decreases, the liquid in the upper liquid chamber is circulated by the expansion-side damping force generating means of the piston while being displaced to the lower liquid chamber to generate the expansion-side damping force. At this time,
Since the base check valve is opened to allow the liquid to flow from the reservoir chamber to the lower liquid chamber, the lower liquid chamber is replenished with the liquid for the piston rod withdrawal.

During the compression stroke of the piston, the hydraulic pressure in the lower liquid chamber and the upper liquid chamber rises, and the liquid in the lower liquid chamber is squeezed by the compression-side damping force generating means of the base check valve to be circulated through the reservoir chamber for displacement and compression. A side damping force is generated. Further, at this time, the liquid in the lower liquid chamber opens the piston check valve of the piston and flows into the upper liquid chamber, so that the lower liquid chamber and the upper liquid chamber have approximately the same pressure, causing a cavitation in the upper liquid chamber. Is prevented.

Further, since the internal liquid pressure of the upper liquid chamber rises during both the piston extending process and the compression process, the upper liquid chamber reaches the reservoir chamber through the communication passage from the upper liquid chamber. Liquid flow occurs. Then, when the moving speed of the piston increases, the variable throttle reduces the opening area of the communication passage due to the hydraulic pressure in the cylinder which changes according to the moving speed, and the duty pot mechanism maintains the operating pressure. Therefore, in any of the above steps, the flow in the communication passage is throttled and the damping force generated by the damping force generating means is strengthened. Further, when the moving speed of the piston becomes slow, the variable throttle increases the opening area of the communication passage as the hydraulic pressure in the cylinder decreases. The power is weakened.

Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 to 4 show one embodiment of the present invention.
Is a cylindrical cylinder defined by the piston 2 into an upper liquid chamber A and a lower liquid chamber B, and the inside of which is filled with a liquid such as oil. 3 is arranged outside the cylinder 1,
It is an outer cylinder that forms a reservoir chamber D between and. And
In the reservoir chamber D, gas is sealed in the upper part and liquid such as oil is filled in the other part. Reference numeral 4 denotes a piston rod which penetrates one end of the cylinder 1 and extends to the outside. A piston mounting step 5 is formed at the tip of the piston rod 4.
The piston 2 is fitted on the piston mounting step 5 together with the spacer 6 and is fastened with a nut 7. The piston 2 has a passage 8 that connects the upper liquid chamber A and the lower liquid chamber B.
Is formed, and a piston check valve 9 is attached to the open end of the passage 8 on the upper liquid chamber A side. This piston check valve 9 is an outer cylinder part fitted to the piston 2.
A retainer 10 including a flange portion 10b that is bent from the outer cylindrical portion 10a and fits into the spacer 6, a check spring 11 with a weak spring force supported by the retainer 10, and a lower portion due to the check spring 11 Made of an elastic plate that closes the check body 12 that is once urged toward (the end surface of the piston 2 on the upper liquid chamber A side), the through hole 13 formed in the check body 12, and the passage 8 formed in the piston 2. The extension side damping force generating means 14 of FIG. And
The check body 12 and the extension side damping force generating means 14 are fitted between the outer cylindrical portion 10a of the retainer 10 and the spacer 6 in a reciprocally movable state. Of these, the extension side damping force generating means 14
Since the notch 15 is formed on the surface of the piston 2 on the upper liquid chamber A side, the inner peripheral end can be flexibly deformed toward the lower liquid chamber B side. Reference numeral 16 is a passage formed in the retainer 10. Piston check valve 9 configured in this way
Is the extension side damping force generating means 14 during the compression stroke of the piston 2.
Receives the hydraulic pressure of the lower liquid chamber B, presses the check spring 11 through the check body 12 and contracts it to open the passage 8, and allows the liquid to flow from the lower liquid chamber B to the upper liquid chamber A. or,
In the piston check valve 9, the inner peripheral end portion of the expansion side damping force generating means 14 receives the hydraulic pressure of the upper liquid chamber A and is bent and deformed downward to open the through hole 13 during the extension stroke of the piston 2 to open the upper liquid. A damping force is generated in order to throttle the flow of the liquid that is displaced from the chamber A through the through hole 13 and the passage 8 to the lower liquid chamber B.

Reference numeral 17 is a base check valve attached to the lower portion of the cylinder 1. The base check valve 17 is, as shown in FIG. 2, specifically, a valve body 18 fixed to the lower end of the cylinder 1, a substantially hat-shaped retainer 19 fixed to the upper portion of the valve body 18, and the retainer. The check spring 20 supported by 19, the check body 21 urged by the check spring 20 toward the valve body 18 side below, and the check body 21 interposed between the check body 21 and the valve body 18 and the retainer 19. A compression-side damping force generating means 24 made of an elastic plate, which is fitted in a reciprocally movable state and closes a through hole 22 formed in the check body 21 and a passage 23 (see FIG. 4) formed in the valve body 18. It consists of 25 is a compression side damping force generating means of the valve body 18.
24 is a notch formed on the surface facing 24, and this notch
Since 25 is formed, the inner peripheral end of the compression-side damping force generating means 24 can be bent and deformed downward. Reference numeral 26 is a passage formed in the retainer 19, and 27 is a passage provided at the lower end of the valve body 18 to connect the lower liquid chamber B and the reservoir chamber D. In the base check valve 17 thus configured, the inner peripheral end of the compression side damping force generating means 24 receives the hydraulic pressure of the lower liquid chamber B during the compression stroke of the piston 2.
When the hydraulic pressure reaches a predetermined value, the inner peripheral end portion is bent and deformed downward to open the through hole 22, and the lower liquid chamber B is passed through the through hole 22 and the passage 2.
A damping force is generated in order to restrict the flow of the liquid that is replaced and circulated in the reservoir chamber D via 3,27. In the base check valve 17, the compression side damping force generating means 24 receives the reduced hydraulic pressure of the lower fluid chamber B on one side and the hydraulic pressure of the reservoir chamber D on the other side during the extension stroke of the piston 2.
The check spring 20 is pressed and contracted via 21 to open the passage 23 to allow the flow of liquid from the reservoir chamber D to the lower liquid chamber B.

28 is a communication passage that connects the upper liquid chamber A and the reservoir chamber D. In the case of the present embodiment, the communication passage 28 is formed as a double structure of the cylinder 1 and extends toward the lower end from the upper end of the cylinder 1, and the upper end portion is opened to the upper liquid chamber A through the communication hole 29. The cylinder side communication passage 28a and the side passage 30 formed in the valve body 18 of the base check valve 17 and opening to the lower end portion of the cylinder side communication passage 28a and the side passage 30 cooperate with the reservoir chamber D to communicate with each other. It is configured with a base check side communication passage 28b including passages 27a, 27.

Reference numeral 31 is a damping force variable mechanism attached to the side passage 30 of the base check side communication passage 28b. This damping force variable mechanism 31
A fixed orifice cylinder 34 having a substantially U-shaped cross section, which is fixed to the side passage 30 and has a plurality of orifices (passages) 32 that open in the passage 30 and a communication hole 33 that communicates with the passage 27a of the valve body 18. A shaft portion 35a fitted in the fixed orifice cylinder 34 in a reciprocating manner and a flange portion 3 fitted in the side passage 30.
5b spool with a substantially T-shaped cross section, and this spool
It is interposed between the flange portion 35b of 35 and one end of the fixed orifice cylinder 34, and is attached to one end side of the side passage 30 (in a direction away from the fixed orifice cylinder 34) with a predetermined elastic force. Energizing spring 36 and flange 35b of spool 35
It is composed of an oil reservoir 37 which is recessed at one end of the side passage 30 located outside the oil reservoir, and a pressure control orifice 38 which communicates the oil reservoir 37 with the lower liquid chamber B.

In this embodiment, a fixed orifice cylinder 34 having a plurality of orifices 32, a spool 35 and a spring.
36 constitutes a variable throttle operated by the hydraulic pressure in the cylinder 1, and the oil reservoir 37 and the pressure control orifice 38 constitute a dashpot mechanism for maintaining the operating position of the variable throttle.

39 is a valve body 18 for connecting the side passage 30 in which the spring 36 is accommodated and the reservoir chamber D via the passage 27.
Is a communication hole formed in the. In the damping force variable mechanism 31 configured as described above, when the traveling speed of the piston 2 becomes high and the hydraulic pressure in the lower liquid chamber B rises above a predetermined pressure during traveling on a bad road or the like, the spool 35 is pressure controlled. The liquid pressure in the lower liquid chamber B is received via 38, and the spring 36 is pressed and contracted to enter the fixed orifice tube 34, and some of the orifices 32 are closed, and the piston 2 is extended. Increases the damping force during the compression stroke. Further, when the piston speed is increased and the hydraulic pressure in the lower liquid chamber B is increased, the damping force varying mechanism 31 has a plurality of orifices 32 as shown in FIG.
Since all of the above are closed by the spool 35, the damping force during the extension stroke and compression stroke of the piston 2 is further strengthened.

On the other hand, when the moving speed of the piston 2 slows down during running on a good road, the hydraulic pressure in the lower liquid chamber B drops, so that the damping force varying mechanism 31 opens the orifice 32 by pushing the spool 35 back by the spring. Therefore, the damping force during the extension stroke and compression stroke of the piston 2 is weakened. As described above, the damping force varying mechanism 31 causes the spool 35 to respond to the moving speed of the piston 2 (that is, the change in the hydraulic pressure of the lower liquid chamber B), so that the extension side damping force generating means 14 and the compression side damping force generating means 24 are generated. The strength of the damping force generated by the
Since the liquid displacing and flowing between the oil reservoir 37 and the side passage 30 communicating therewith is squeezed by the pressure control orifice 38, the oil reservoir 37 and the pressure control orifice 38 act as a damper. As a result, sudden movement of the spool 35 is prevented. The moving speed of the spool 35 is determined by the set load of the spring 36, the spring constant, the diameter of the pressure control orifice 38, and the like.

A rod guide 40 is provided at the upper end of the cylinder 1 and slidably supports the piston rod 4. 41 is
The seal device is disposed outside the rod guide 40 and is in close contact with the outer circumference of the piston rod 4 and the inner circumference of the outer cylinder 3 to seal the upper ends of the cylinder 1 and the outer cylinder 3. Reference numeral 42 denotes a lid member that is fixed to the lower ends of the outer cylinder 3 and seals the lower ends of the cylinder 1 and the outer cylinder 3.

According to the above-described structure of the embodiment, during the extension stroke of the piston 2, the liquid pressure in the upper liquid chamber A rises and the liquid pressure in the lower liquid chamber B falls, so that the liquid in the upper liquid chamber A is transferred to the piston check valve 9 While being squeezed by the expansion-side damping force generating means 14, it is circulated through the lower liquid chamber B to generate an expansion-side damping force. This extension side damping force is a communication passage that connects the upper liquid chamber A and the reservoir chamber D.
By the damping force variable mechanism 31 attached to the piston 28, the piston 2
Adjusted according to the speed of. Further, at this time, the base check valve 17 is opened to move the reservoir chamber D to the lower liquid chamber B.
Since the liquid is allowed to flow into the lower rod chamber B, the liquid that has withdrawn from the piston rod 4 is replenished. On the other hand, during the compression stroke of the piston 2, the hydraulic pressure in the lower liquid chamber B rises, but this hydraulic pressure also opens the piston check valve 9 of the piston 2 to flow into the upper liquid chamber A, and When the hydraulic pressure in A is raised to approximately the same pressure as the lower hydraulic chamber B and the hydraulic pressure in the lower hydraulic chamber B reaches a predetermined value, the liquid in the lower hydraulic chamber B is applied to the compression side damping force generating means 24 of the base check valve 17. Therefore, the compressed side damping force is generated by the displacement and flow through the reservoir chamber D while being squeezed. This damping force on the compression side is changed by the damping force variable mechanism 31 attached to the communication passage 28 that connects the upper liquid chamber A and the reservoir chamber D.
It is adjusted according to the speed of the piston 2.

When the moving speed of the piston 2 increases, first, during the compression process, the spool 35 forming the variable throttle of the damping force adjusting mechanism 31 receives the pressure of the lower liquid chamber B and the opening area of the communication hole 28. Is operated in the right direction in the figure so as to reduce the pressure, and during the subsequent stretching process, the dash pot mechanism composed of the oil reservoir 37 and the pressure control orifice 38 acts so that the operating pressure received during the compression process is maintained almost as it is. Therefore, the generated damping force is strengthened in any process.

FIG. 5 shows an application example of the above-described embodiment. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals, and the description will be omitted without duplicating description. That is, in this application example, the damper liquid chamber C is formed at one end of the side passage 30 of the base check valve 17, and the damper liquid chamber C and the lower liquid chamber B are connected to each other by the valve body.
A communication passage 44 communicating with the pressure introduction hole 43 formed in the hole 18.
A check valve 45 that allows the flow of liquid from the lower liquid chamber B to the damper liquid chamber C is provided between the communication passage 44 and the damper liquid chamber C. And this check valve 45
Is composed of a valve body 47 that is seated on a seat portion 46 protruding from the open end of the communication passage 44, and a spring 48 that biases the valve body 47 toward the seat portion 46 with a weak spring force. A pressure control orifice 49 is bored substantially in the center of the valve body 47, and a communication groove 50 is cut out in the outer peripheral end of the valve body 47. With this configuration, when the hydraulic pressure in the lower liquid chamber B rises above the predetermined pressure, the check valve 45 is opened through the pressure introducing hole 43 and the communication passage 44 to enter the damper liquid chamber C. Lower liquid chamber B
The liquid pushes the spool 35 of the damping force varying mechanism 31 into the fixed orifice tube 34, and the opening area of the orifice 32 is reduced to adjust the damping force. On the other hand, when the hydraulic pressure in the lower liquid chamber B drops, the check valve 45 closes the communication passage 44, so the liquid in the damper liquid chamber C is throttled by the pressure control orifice 49 and the lower liquid chamber B is closed.
Flow to the spool 35, the spool 35 gently returns to a position where the urging force of the spring 36 and the hydraulic pressure of the lower liquid chamber B are balanced. In this way, the sudden return operation of the spool 35 is prevented, and the opening area of the orifice 32 is stably maintained.

In this application example, the damper liquid chamber C and the check valve 45 provided with the pressure control orifice 49 constitute a dump-pot mechanism.

6 to 7 show another embodiment of the present invention.
The same parts as those in the above embodiment are designated by the same reference numerals, and the description will not be repeated. That is, in this embodiment, the piston check valve 9 is attached to the piston 2 and the base check valve 17 is attached to the lower end of the cylinder 1 as in the above embodiment, but the damping force varying mechanism is arranged at The configuration is different. Here, 51 is a cylinder-side communication passage that extends from the upper part to the lower part of the cylinder 1 and has a lower end communicating with the reservoir chamber D through a communication hole 52. 53 is the rod guide 40
Is a rod guide side communication passage that connects the upper liquid chamber A and the cylinder side communication passage 51. This rod guide-side communication passage 53 has an axial passage 53a formed in the inner periphery of the rod guide 40, and one end is opened in this axial passage 53a and the other end is opened in the cylinder-side communication passage 51 in the radial direction. It is connected to the passage 53b. The cylinder side communication passage 51 and the rod guide side communication passage 53 form a communication passage 54 that connects the upper liquid chamber A and the reservoir chamber D. Reference numeral 55 is a damping force variable mechanism interposed in the passage 53b of the rod guide side communication passage 53. The damping force varying mechanism 55 is disposed at one end of a spool 56 that changes the passage cross-sectional area of the passage 53b and a spool valve chamber E that slidably accommodates the spool 56, and is arranged from the upper liquid chamber A to the spool valve chamber E. Is arranged at the other end of the check valve 51, the damper liquid chamber C provided between the check valve 57 and the spool 57, and the spool valve chamber E to open the spool 56 in the valve opening direction ( (One end side of spool valve chamber E)
It consists of a spring 58 that urges to. this house,
The check valve 57 is formed on the rod guide 40 as shown in detail in FIG. 7, and is mounted on the spool side end 60 of the pressure introducing hole 59 that connects the upper liquid chamber A and the spool valve chamber E. 61, a check spring 62 for urging the check valve body 61 toward the pressure introducing hole 59 with a weak spring force, and a support 63 for supporting the check spring 62. Further, the check valve body 61 is provided with a pressure control orifice 64 at a substantially central portion thereof, and a communication groove 65 is cut out at an outer peripheral end portion thereof.

In this embodiment, the spool 56 and the spring
58 constitutes a variable throttle operated by the hydraulic pressure in the cylinder 1, and the damper fluid chamber C and the check valve body 61 having a pressure control orifice 64 constitute a dump pot mechanism for maintaining the operating position of the variable throttle. It is about to do. With this configuration, when the moving speed of the piston 2 increases and the hydraulic pressure in the upper liquid chamber A rises above a predetermined pressure when traveling on a rough road, the liquid in the upper liquid chamber A is checked by the check valve 57.
Is opened to flow into the one end side of the spool valve chamber E from the pressure introducing hole 59, and the spool 56 is moved to the other end side of the spool valve chamber E. Therefore, the passage cross-sectional area of the passage 53b is narrowed down by the spool 56, and the damping force becomes stronger. At this time, the hydraulic pressure in the upper liquid chamber A fluctuates as the piston 2 moves, but the operating pressure of the spool 56 is maintained substantially constant by the dump pot mechanism including the damper liquid chamber C and the check valve body 61. To be done. On the other hand, when the traveling speed of the piston 2 becomes slow and the hydraulic pressure in the upper liquid chamber A drops when traveling on a good road,
The check valve 57 is closed, the liquid in the spool valve chamber E is throttled by the pressure control orifice 64 and flows out to the upper liquid chamber A side, so that the spool 56 is urged by the spring 58 and gently returns. In this way, the spool 56
It is possible to prevent the sudden return of the.

FIG. 8 shows an example of a damping force characteristic diagram obtained by the damping force variable type hydraulic shock absorber of the present invention. (I) shows damping obtained by the extension side damping force generating means 14. Showing power,
Since (II) shows the damping force obtained by the compression side damping force generating means 24, (III) shows the damping force obtained by the operation of the damping force varying mechanism 31. In the figure, point a is a spring 36 for urging the damping force varying mechanism 31, 55,
58 shows the set load of 58.

EFFECTS OF THE INVENTION As described above, the present invention provides a piston with an extension-side damping force generating means for generating a damping force by displacing and circulating the liquid in the upper liquid chamber into the lower liquid chamber during the piston stretching process, and the piston. A check valve that allows the liquid to flow from the lower liquid chamber to the upper liquid chamber during the compression process is provided, and at the bottom of the cylinder, the liquid in the lower liquid chamber is replaced and circulated to the reservoir chamber during the piston compression process. Damping force variable hydraulic buffer provided with a compression side damping force generating means for generating a damping force and a base check valve for allowing the liquid to flow from the reservoir chamber to the lower liquid chamber during the expansion process of the piston. In the container, a communication passage that connects the upper liquid chamber and the reservoir chamber is provided, and the communication passage is operated by the hydraulic pressure in the cylinder that changes according to the moving speed of the piston, and opens as the piston speed increases. With a variable throttle that reduces the mouth area, and a dashpot mechanism that maintains the operating position of the variable throttle during both compression and expansion processes, there is no cavitation in the upper liquid chamber, and there is no compression or expansion process. It is possible to obtain the optimum damping force according to the moving speed of the piston. Therefore, according to the present invention, a wide and wide damping force can be obtained according to the vehicle characteristics. Further, since an external actuator for activating the damping force variable mechanism is unnecessary, there is an effect that the product price can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
FIG. 3 is an enlarged view of the lower end of the figure, FIG. 3 is an operation state diagram of the damping force variable mechanism, FIG. 4 is a sectional view taken along line IV-IV of FIG. 2, and FIG. 6 is a sectional view showing another embodiment of the present invention, FIG. 7 is a partially enlarged view of the same damping force variable mechanism, and FIG. 8 is a damping force characteristic diagram. 1 ... Cylinder, 2 ... Piston, 9 ... Piston check valve, 14 ... Extension side damping force generating means, 17 ... Base check valve, 24 ... Compression side damping force generating means, 28,54
...... Communication passage, 31,55 …… Damping force variable mechanism, 32,53b ……
(Passage orifice), 35,56 ... Spool, A ... upper liquid chamber, B ... lower liquid chamber, D ... reservoir chamber.

Claims (1)

(57) [Claims] 1. A cylinder, in which a piston defining an upper liquid chamber and a lower liquid chamber is housed, and an outer chamber which forms a reservoir chamber with the cylinder outside the cylinder. A cylinder is provided, and an extension side damping force generating means for generating a damping force by displacing and circulating the liquid in the upper liquid chamber to the lower liquid chamber during the piston stretching process, and a lower portion during the piston compression process. A piston check valve that allows the liquid to flow from the liquid chamber to the upper liquid chamber is provided, and at the bottom of the cylinder, the liquid in the lower liquid chamber is replaced and circulated to the reservoir chamber during the compression process of the piston, and the damping force is generated. A damping force variable hydraulic shock absorber provided with a compression side damping force generating means and a base check valve that allows the liquid to flow from the reservoir chamber to the lower liquid chamber during the piston stretching process. A communication passage that connects the upper liquid chamber and the reservoir chamber is provided, and the communication passage is operated by the hydraulic pressure in the cylinder that changes according to the moving speed of the piston, and the opening area increases as the piston speed increases. A damping force variable type hydraulic shock absorber, wherein a variable throttle for reducing the pressure is interposed and a dashpot mechanism is provided for maintaining the operating position of the variable throttle during both the steps of compression.