JPH0413567B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a damping force adjustment structure for a hydraulic shock absorber, and particularly to a hydraulic shock absorber in which a piezoelectric element is used as an actuator of a mechanism for adjusting the damping force. This invention relates to a damping force adjustment structure.

[Conventional technology]

For example, a hydraulic shock absorber serving as a shock absorber for a vehicle is formed to provide a uniform, predetermined damping effect depending on the characteristics of the vehicle. However, if the damping mechanism is formed so that only a uniform predetermined damping effect is performed, the ride comfort cannot be improved depending on the road surface condition on which the vehicle travels.

Therefore, in recent years, various proposals have been made for so-called damping force adjustable hydraulic shock absorbers in which the damping force generated by the hydraulic shock absorbers can be made variable in accordance with road surface conditions.

[Problem that the invention seeks to solve]

However, among the various conventional proposals described above, a damping force adjustment mechanism is provided within the hydraulic shock absorber, and an actuator for operating the damping force adjustment mechanism is attached to the outside of the hydraulic shock absorber, for example, at the upper end of the piston rod. In this case, there are disadvantages such as restrictions on the installation position when installing the hydraulic shock absorber in a vehicle, etc., and the possibility of external failure after installation.

Therefore, in view of the above-mentioned circumstances, the present invention has been developed so that when it is installed on a vehicle etc., there is no restriction on the installation position.
Another object of the present invention is to provide a new damping force adjustment structure for a hydraulic shock absorber that can greatly reduce the risk of causing an extrinsic failure to the actuator after installation.

[Means for solving problems]

In order to solve the above problems, the basic structure of the present invention is modified so that the damping force generated when the piston rod connected to the piston part in the cylinder slides can be changed by operating an appropriate actuator. In the damping force adjustment structure of a hydraulic shock absorber formed in The member is formed to allow a pressing force to act in the axial direction of the piston rod, and a piezoelectric element as an actuator that applies a pressing force to the pressing member is housed inside near the lower end of the piston rod. It is characterized by:

〔Example〕

The present invention will be explained below based on the illustrated embodiments.

FIG. 1 shows a hydraulic shock absorber according to a preferred embodiment of the present invention, and the hydraulic shock absorber includes:
It has a piston part 2 that is slidably disposed within a cylinder 1, and a piston rod 3 that is connected to the piston part 2 and whose upper end projects outside the cylinder 1.

The interior of the cylinder 1 is divided by the piston portion 2 into a rod-side oil chamber A and a piston-side oil chamber B, which are formed so as to be able to communicate with each other via the piston portion 2. A base valve section 4 is disposed at the bottom of the lower end of the cylinder 1, and the piston side oil chamber B connects to an outer shell 5 disposed on the outer periphery of the cylinder 1 via the base valve section 4. It is formed so as to be in communication with the reservoir chamber C formed between them.

The piston part 2 has an inner oil passage 7 and an outer oil passage 8 formed by penetrating the thick part in the axial direction of the piston body 6, and has a piston ring 9 on the outer periphery thereof. . A pressure side valve 10 is disposed at the upper end opening of the outer oil passage 8, that is, the opening on the rod side oil chamber A side. The pressure-side valve 10 has an orifice 10a, is biased from above by a spring 11, and is formed to generate a predetermined pressure-side damping force during the compression-side stroke when the piston portion 2 moves downward within the cylinder 1.

In this embodiment, the main compression side damping force is generated by the base valve section 4, and therefore the base valve section 4
It has a check valve 4a, a throttle 4b and a relief valve 4c.

The piston portion 2 includes a rebound damping force generating portion 12.
are arranged in series, and the extension damping force in the extension damping force generating section 12 is formed so as to be able to change this.

That is, a support member 13 is screwed to the lower end of the piston body 6, and a rebound damping force generating valve 14 is disposed on the upper surface of the support member 13, and A pressing member 15 is arranged adjacent to the upper surface of the generating valve 14.

The lower end of the piston body 6 is formed into a cylindrical shape, and the inside thereof communicates with the inner oil passage 7 of the piston body 6. The support member 13 is screwed onto the lower end of the cylindrical shape from below, and is formed into a cylindrical shape as a whole, with an annular support point 13a formed on its upper end surface. The expansion damping force generating valve 14 is a so-called leaf valve, and is formed into a ring shape with a notch 14a in the center. The support point 13a is configured to abut against the thick lower surface of the expansion damping force generating valve 14. Further, the pressing member 15 closes the center notch 14a of the rebound damping force generating valve 14 from the upper surface, and also closes the central notch 14a of the rebound damping force generating valve 14.
An inner annular rib 15a and an outer annular rib 15 are formed so as to form a pressure receiving surface for oil flowing in through the inner oil passage 7 on the upper surface of the thick part of the inner annular rib 15a.
b on its lower surface. An oil passage 15 is provided in the axially thick portion of the pressing member 15 that is regulated by the inner annular rib 15a and the outer annular rib 15b.
c is drilled. And also, the oil passage 15
c communicates with the inner oil passage 7 of the piston body 6 through the inside of the lower end of the piston body 6.

Therefore, during the extension stroke in which the piston portion 2 moves upward within the cylinder 1, the oil in the rod side oil chamber A is
The oil inside the lower end of the piston body 6 flows through the inner oil passage 7 of the piston body 6, and the oil inside the lower end of the piston body 6 flows through the oil passage 7 of the pressing member 15.
5c. The oil in the oil passage 15c of the pressing member 15 causes the inner circumferential end of the rebound damping force generating valve 14 to bend, and the inner annular rib 15a of the pressing member 15 and the bent rebound damping force generating valve 14 support member 1 through a gap formed between the inner circumferential end of
3, that is, into the piston-side oil chamber B, and at that time, a predetermined extension-side damping force is generated.

The damping force generated by the rebound damping force generating valve 14 changes the initial load of the rebound damping force generating valve 14 when a pressing force is applied by the pressing member 15. Thus, the damping force is adjusted to a desired magnitude. In this embodiment, the shaft portion 1 of the pressing member 15 is
5d from above, the initial load of the rebound damping force generating valve 14 is changed, and this axial force is applied by the actuator according to the present invention. It is something.

That is, the vicinity of the lower end of the piston rod 3 is formed by the sub-rod 16, and the piston part 2 is disposed in the spigot part of the lower end of the sub-rod 16, and the piston rod 3 according to the present invention is provided within the sub-rod 16. Such an actuator is installed internally. The actuator includes a large number of laminated piezoelectric elements 17, and the displacement generated when voltage is applied to the piezoelectric elements 17 is transmitted as an axial force to the shaft portion 15d of the pressing member 15. It is designed so that it can be used.

That is, in this embodiment, in order to form a large number of laminated piezoelectric elements 17 into one rod-shaped body,
An upper block 19 and a lower block 20 are fixed to the upper and lower ends of a bolt 18 passing through the center of the stacked piezoelectric elements 17, and the stacked piezoelectric elements 17 are fixed between the upper block 19 and the lower block 20. It has a cover 21 arranged to protect it. A through hole 3 is bored in the axial center of the piston rod 3.
When a voltage is applied to the piezoelectric element 17 via a lead wire 23 inserted through the inside of the piezoelectric element 17 and connected to an appropriate external power source 22, etc., the piezoelectric element 17 is displaced so as to expand. At this time, in order to make the displacement appear as a pressing force that pushes down the lower block 20 at the lower end,
In this embodiment, the upper block 19
A holder 24 is interposed between the piston rod 3 and the lower end of the piston rod 3 above the holder 24.
is designed to prevent the upper block 19 from rising and to allow all of the displacement caused by the piezoelectric element 17 to be exposed to the lower block 20 side.

Therefore, the expansion-side damping force generated by the expansion-side damping force generating valve 14 increases the pressing force generated by voltage application to the piezoelectric element 17 from the pressing member 15.
The rebound damping force generating valve 14
The initial load is changed, and as a result, a desired damping force different from the initially predetermined damping force can be adjusted to the rebound damping force. Further, if the applied voltage is made variable, the pressing force by the pressing member 15 is made variable, and the initial load of the rebound damping force generating valve 14 can be adjusted as desired.

Further, in this embodiment, the holder 24 is formed to expand when heated, and the coefficient of thermal expansion of the sub-rod 16 as the piston rod 3 and the coefficient of thermal expansion of the piezoelectric element 17 are different. Since these do not necessarily match, in order to avoid differences in the pressing effect due to the amount of thermal expansion of the piezoelectric element 17, that is, the amount of displacement when voltage is applied, a thermal expansion correction member that is in tune with the amount of thermal expansion of the sub-rod 16 is used to correct the pressure. It is equipped. Similarly to the piezoelectric element 17, the holder 24 is connected to the external power source 22 and the like via a lead wire 23a.

A steel ball 25 is disposed between the lower block 20 and the lower pressing member 15 to prevent the piezoelectric element 17 from being damaged by the bending reaction force from the direction of the pressing member 15. It has a freely connecting structure to prevent this. Further, an O-ring 26 is attached to the outer periphery of the shaft portion 15d of the pressing member 15.
An O-ring 27 is installed at the upper end of the sub-rod 16 to prevent the hydraulic oil from entering the sub-rod 16, and an O-ring 27 is also installed at the upper end of the sub-rod 16 to prevent the hydraulic oil from entering the sub-rod 16. Care has been taken to prevent intrusion. moreover,
A rebound cushion 29 held by a rebound support 28 is disposed at the lower end of the piston rod 3, that is, at the outer circumference located above the upper end of the sub-rod 16.

FIG. 2 shows another embodiment of the rebound damping force generating section 12, and in this embodiment,
The contact point of the outer annular rib 15b of the pressing member 15 that comes into contact with the upper surface of the rebound damping force generating valve 14 disposed on the upper end surface of the support member 13 is the contact point of the rebound damping force generating valve 1.
The annular support point 13a on the upper end surface of the support member 13, which is in contact with the lower surface of the support member 4, is positioned on the outer peripheral side of the annular support point 13a.

As a result, when the pressing force from the piezoelectric element 17 serving as the actuator above the pressing member 15 is applied, the outer circumferential side of the expansion damping force generating valve 14 is bent, and its initial load is reduced. This makes it possible to adjust the damping force in the low and medium piston speed range.

In addition, in this embodiment, the above-mentioned pressing member 15
An inner annular rib 15a (see Fig. 1) is provided on the lower end surface of the
The formation of the oil passage 15c (see FIG. 1) is also omitted. Further, an oil passage 13b is formed in the support member 13, and the upper end central land portion 13c is inserted into the central notch portion 14a of the expansion side damping force generating valve 14. As a result, during the extension stroke in which the piston portion 2 moves upward, the inner oil passage 7 of the piston body 6
The oil from the upper rod-side oil chamber A flows into the lower end of the piston body 6 through the oil passage 13b of the support member 13 by bending the outer peripheral side of the rebound-side damping force generating valve 14. This will flow into the piston side oil chamber B.

Furthermore, in this embodiment, when the support member 13 is screwed onto the lower end of the piston main body 6, the screws are adjusted in advance so as to reduce the initial load of the expansion side damping force generating valve 14. It is also possible to try to make adjustments.

FIG. 3 shows the rebound damping force generating section 12 shown in FIG. 1.
This shows still another embodiment of the present invention, in which the pressing member 15 is in contact with the upper surface of the rebound damping force generating valve 14 disposed on the upper end surface of the supporting member 13. The support member 1 in which the contact point of the outer annular rib 15b contacts the lower surface of the expansion-side damping force generation valve 14
It is positioned on the inner circumferential side from the position of the annular support point 13a on the upper end surface of No.3. That is, instead of the pressing on the outer peripheral side as shown in FIG. 2, the pressing is applied on the inner peripheral side.

As a result, when a pressing force is applied to the pressing member 15 from the piezoelectric element 17, which is an actuator located above, the inner circumferential side of the expansion-side damping force generating valve 14 is bent, and the initial load is reduced. As a result, the damping force generated by the expansion-side damping force generating valve 14 is adjusted. In addition, during the extension stroke in which the piston portion 2 moves upward, the outer peripheral side of the extension damping force generating valve 14 is bent, and a predetermined extension damping force is generated.

FIG. 4 shows an embodiment of a modification of the rebound damping force generating section 12 according to FIG. 3, and includes:
Instead of the support member 13 being integrally formed, the support member 13 according to this embodiment is made up of a set nut 30, a support disk 31, and a steel ball 32. Then, the set nut 30 is screwed onto the lower end of the piston main body 6, and at this time, the support disk 31 is slidably housed inside the upper end thereof, and the support disk 31 and the set nut 30 are screwed together. Between the above steel balls 32
are interposed, and the whole is formed to have a freely connected structure.

As a result, even if the set nut 30 screwed onto the lower end of the piston main body 6 cannot maintain a horizontal direction with respect to the lower end of the piston main body 6, the lower surface of the rebound damping force generating valve 14 The support disk 31 that is in contact with the nut 30 always maintains a preferred horizontal direction, and the set nut 30
The effect of equalizing the screwing force due to this, that is, the supporting force of the support disk 31 with respect to the rebound damping force generating valve 14 is obtained.

The rebound damping force generating valve 14 is disposed on the upper end surface of the support disk 31, and the annular support point 31a formed on the upper end surface of the support disk 31 is connected to the rebound damping force generating valve 14. It is in contact with the bottom surface of. Furthermore, an oil passage 30a is formed in the set nut 30 in place of the oil passage 13b (see FIG. 3).

FIG. 5 shows the rebound damping force generating section 12 shown in FIG.
In this embodiment, a pressing force from a piezoelectric element 17 serving as an upper actuator acts on a pressing member 15 adjacent to the rebound damping force generating valve 14. When this occurs, the pressing force acts on the inner and outer peripheries of the rebound damping force generating valve 14, thereby causing the outer periphery to flex, thereby making it possible to adjust the initial load.

In this embodiment, the support member 13 is composed of a set nut 30, a support disk 31, and a steel ball 32, and has a freely connected structure, similar to the support member 13 shown in FIG. 4. Further, the pressing member 15 has an inner annular rib 15a on its lower end surface, and an outer annular rib 15a.
b (see FIG. 1), an annular land portion 15e
The inner annular rib 15a and the annular land portion 15e are brought into contact with the upper surface of the lower extension damping force generating valve 14.

FIG. 6 shows an embodiment according to a modification of the rebound damping force generating section 12 shown in FIG.
In any of the embodiments described above, the pressing member 15
Instead of being formed into an integral structure, they are formed to have a freely connected structure. That is, the pressing member 15 according to this embodiment is as follows:
A push rod 33 is arranged on the piezoelectric element 17 side which is an actuator in the upper part, and a push disk 34 is arranged in the lower part on the side of the expansion side damping force generation valve 14.
and a steel ball 3 between the push disk 34 and the push rod 33.
5 is inserted.

This allows the pressing force transmitted from the piezoelectric element 17 as an actuator to be applied to the push rod 3.
Even if there is a situation where the transmission is eccentric to 3,
Rebound damping force generation valve 1 by push disk 34
An effect can be obtained in which the pressing force against 4 is always uniform.

In this embodiment, the lower end surface of the push disk 34 is provided with an inner annular rib 34a and an outer annular land portion 34b that come into contact with the upper surface of the lower expansion damping force generating valve 14. As well as having
It has an oil passage 34c in a thick wall portion regulated by an inner annular rib 34a and an annular land portion 34b. The pressing force from the piezoelectric element 17 as the actuator is applied to the inner annular rib 34.
a and the annular land portion 34b to act on the inner and outer peripheries of the rebound damping force generating valve 14 to adjust its initial load, and its outer periphery is bent to produce the desired adjusted rebound damping force. Power is starting to be generated.

FIG. 7 shows another embodiment according to a modification of the rebound damping force generating valve 14 according to FIG. 5, and in this embodiment, the rebound damping force generating valve 14
In addition to adjusting the initial load by applying a pressing force to the upper pressing member 15, the adjustment is also performed by a biasing member 36 from below the rebound damping force generating valve 14. That is, the support disk 31 that comes into contact with the lower surface of the rebound damping force generating valve 14 is formed so that the contact force from the set nut 30 that is screwed onto the lower end of the piston body 6 acts on it. A biasing member 36 from below is provided on the lower surface of the outer peripheral side of the expansion side damping force generating valve 14.
It is formed in such a way that the auxiliary forces of
The biasing member 36 has spring receivers 3 at its upper and lower ends.
7, 38, and the upper spring receiver 37 is connected to the rebound damping force generating valve 1.
The lower spring receiver 38 is supported via a spacer 41 by a stopper 40 which is screwed onto the lower end of the piston body 6.

Therefore, the initial load of the rebound damping force generating valve 14 is adjusted by the pressing member 15 facing the set nut 30, and the urging member 3
6 will also be adjusted. In this embodiment as well, the expansion side damping force generating valve 14 receives pressing force on its inner and outer peripheries by the pressing member 15, and the desired adjusted expansion is achieved by the flexure of the outer periphery. It is assumed that side damping force is generated.

FIG. 8 shows a rebound damping force generating section 12 according to still another embodiment, and in the embodiment shown in FIGS. In addition to adjusting the initial load by pressing the inner and outer circumferences of the valve 14, the damping force is generated by the deflection of the outer circumference, whereas in this embodiment, the damping force is generated by the deflection of the inner circumference of the rebound damping force generating valve 14. That is. That is, the lower end surface of the push disk 34 constituting the pressing member 15 has an inner annular rib 34a and an outer annular rib 34d.
is formed, and each annular rib 34a, 34d is in contact with the upper surface of the expansion side damping force generating valve 14, respectively. On the other hand, an annular support point 13 a formed on the upper end surface of the lower support member 13 is in contact with the lower surface of the expansion-side damping force generating valve 14 . The annular support point 13a is positioned closer to the outer circumferential side of the expansion damping force generating valve 14. In addition,
In the embodiments shown in FIGS. 5 to 8,
The position where the annular support point 13a abuts against the expansion-side damping force generation valve 14 is set closer to the inner circumferential side of the expansion-side damping force generation valve 14.

Note that this embodiment is also an embodiment in which the pressing member 15 in the embodiment shown in FIG. 1 is modified to have a freely connecting structure.

FIG. 9 shows an embodiment as a modification of the embodiment shown in FIG.
A biasing member 42 is separately provided on the lower surface of the inner circumferential side of 4 to enable adjustment of the initial load. That is, the expansion side damping force generating valve 14
A stopper 43 is disposed on the lower surface of the inner peripheral side of the spring 43, and the upper end of a spring 45 whose lower end is supported by an adjuster 44 is brought into contact with the stopper 43. Then, the stopper 43
is slidably disposed inside the upper end of the support member 13 that abuts the annular support point 13a on the lower surface near the outer periphery of the rebound damping force generation valve 14, and is screwed into the lower end of the support member 13. By screwing and adjusting the adjuster 44 that is mounted together, the initial load of the rebound damping force generating valve 14 can be adjusted separately in addition to the adjustment of the initial load by the pressing member 15. be.

〔Effect of the invention〕

As described above, according to the present invention, the actuator that operates the damping force adjustment mechanism is housed in the piston rod that is inside the hydraulic shock absorber. This has the advantage of not being subject to the above limitations, and also eliminating the risk of causing an external failure to the actuator.

Furthermore, since a piezoelectric element is used as the actuator, only electrical operation is sufficient for operating the actuator, and the pressing force from the piezoelectric element is directly applied to the rebound damping force generation valve via the pressing member. , the responsiveness of adjusting the initial load of the rebound damping force generating valve is improved, and as a result,
This makes it possible to quickly adjust the desired damping force according to the road running conditions of the vehicle equipped with the hydraulic shock absorber.

Furthermore, since a piezoelectric element is used as an actuator, by selecting the applied voltage, the initial load of the rebound damping force generating valve can be adjusted as appropriate. Another advantage is that the optimum damping force can be selected.

Furthermore, since the contact force of the support member that comes into contact with the lower surface of the rebound damping force generating valve can be selected in advance, the initial load of the rebound damping force generating valve can be adjusted depending on the application of the hydraulic shock absorber. This also has the advantage of improving its versatility.

Furthermore, if a biasing force of a biasing member such as a spring is applied directly or indirectly to the rebound damping force generating valve to enable adjustment of its initial load, a wider variety of effects can be achieved. , the effect of enabling more precise damping force adjustment is also obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a hydraulic shock absorber according to an optimal embodiment of the present invention, and FIGS. 2 to 9 are partially enlarged views of other embodiments of the damping force generating structure according to the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Cylinder, 2... Piston part, 3... Piston rod, 6... Piston main body, 7... Inner oil passage, 12... Rebound side damping force generation part, 13... Support member, 14... Extension side Damping force generating valve, 15...pressing member, 16...subrod, 17...piezoelectric element,
24...Holder, 25...Steel ball, 3
0... Set nut, 31... Support disk, 32... Steel ball, 33... Push rod, 34... Push disk, 35... Steel ball, 36, 42... Force member, A...
Rod side oil chamber, B...Piston side oil chamber.

Claims (1)

[Scope of Claims] 1. Damping force of a hydraulic shock absorber formed so that the damping force generated when a piston rod connected to a piston portion in a cylinder slides can be changed by operating an appropriate actuator. In the adjustment structure, a pressing member is brought into contact with the upper surface of the rebound damping force generating valve that is supported by the upper surface of the supporting member attached to the lower end of the piston, and the pressing member is applied with a pressing force that acts in the axial direction of the piston rod. A hydraulic shock absorber characterized in that the piston rod is formed so as to enable the action of the piston rod, and a piezoelectric element as an actuator that applies a pressing force to the pressing member is housed inside the piston rod near the lower end thereof. damping force adjustment structure. 2. The damping force adjustment structure for a hydraulic shock absorber according to claim 1, wherein the rebound damping force generating valve is formed so as to be operated in the opening direction by a pressing force from a pressing member. 3. The hydraulic shock absorber according to claim 1, wherein the rebound damping force generating valve is formed such that its outer circumferential side is bent when the inner circumferential side of the support point on the upper surface of the support member is pressed by the pressing member. damping force adjustment structure. 4. The hydraulic shock absorber according to claim 1, wherein the rebound damping force generating valve is formed so that its outer circumferential side is bent when the inner and outer circumferences of the support point on the upper surface of the support member are pressed by the pressing member. Damping force adjustment structure. 5. The hydraulic shock absorber according to claim 1, wherein the rebound damping force generating valve is formed such that its inner circumferential side is bent when the inner and outer circumferences of the support point on the upper surface of the support member are pressed by the pressing member. damping force adjustment structure. 6 The pressing member consists of a push rod disposed on the actuator side and a push disk disposed on the rebound damping force generating valve, and a steel ball is interposed between the push rod and the push disk. A damping force adjustment structure for a hydraulic shock absorber according to claim 1, which has a freely connecting structure. 7. The support member consists of a support disk disposed on the rebound side damping force generation valve side and a set nut attached to the piston part, and a steel ball is interposed between the support disk and the set nut, so that the support member can be freely moved. A damping force adjustment structure for a hydraulic shock absorber according to claim 1, which is a connected structure. 8. In a damping force adjustment structure for a hydraulic shock absorber, which is formed so that the damping force generated during sliding of a piston rod connected to a piston part in a cylinder can be changed by operation of an appropriate actuator, the piston part A pressing member is brought into contact with the upper surface of the rebound damping force generation valve supported by the upper surface of the support member attached to the lower end, and the pressing member allows a pressing force to act in the axial direction of the piston rod. A piezoelectric element as an actuator that applies a pressing force to the pressing member is housed inside the piston rod near the lower end, and the piezoelectric element is moved by thermal expansion to the lower pressing member. What is claimed is: 1. A damping force adjustment structure for a hydraulic shock absorber, characterized in that a thermal expansion correction member is housed so as to be able to be pressed toward. 9 In a damping force adjustment structure for a hydraulic shock absorber formed in such a manner that the damping force generated during sliding of a piston rod connected to a piston part in a cylinder can be changed by operation of an appropriate actuator, the piston part A pressing member is brought into contact with the upper surface of the rebound damping force generation valve supported by the upper surface of the support member attached to the lower end, and the pressing member allows a pressing force to act in the axial direction of the piston rod. A piezoelectric element as an actuator that applies a pressing force to the pressing member is housed inside the piston rod near the lower end, and a piezoelectric element as an actuator that applies a pressing force to the pressing member is housed below the expansion damping force generating valve. A damping force adjustment structure for a hydraulic shock absorber, characterized in that a biasing member for correcting deflection of a damping force generating valve is provided. 10 In a damping force adjustment structure for a hydraulic shock absorber formed in such a manner that the damping force generated when a piston rod connected to a piston portion in a cylinder slides can be changed by the operation of an appropriate actuator, the piston portion A pressing member is brought into contact with the upper surface of the rebound damping force generation valve supported by the upper surface of the support member attached to the lower end, and the pressing member allows a pressing force to act in the axial direction of the piston rod. A piezoelectric element as an actuator that applies a pressing force to the pressing member is housed inside the piston rod near the lower end, and is brought into contact with the lower surface of the rebound damping force generating valve. A damping force adjustment structure for a hydraulic shock absorber, characterized in that a biasing member for correcting the deflection of the rebound damping force generating valve is disposed within the support member so that its biasing force can be freely adjusted.