JP2002227905A - Piston or valve case of hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain occurrence of extraordinary noise caused by discontinuity of damping force by smoothly making a check valve or a suction valve open with no delay without making deflection rigidity of the check valve or the suction valve opposed to upper face side of a piston or a valve case. SOLUTION: An outside window frame, which forms upper side opening ports 105D, 205D, 305D or 115D, 215D, 315D by connecting to a radial window frame 105F or 115F radially extending to outer peripheral side of an upper side boss part 105E or 115E on the piston 105 or the valve case 115, is so configured that distance R from axial center Z of the piston or the valve case to inner edge of the outside window flame is arc 105G or 115G or A-shaped form 205G or 215G which increases around a central part from both end parts connecting to the radial window frame or arc or V-shaped form which decreases around the central part from both the end parts or linear form 305G or 315G.

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 for suppressing vibration of a vehicle body such as a suspension system of an automobile, and more particularly to an improvement in a damping force generating structure.

[0002]

2. Description of the Related Art As this type of hydraulic shock absorber, for example,
FIG. 2 shows an example in which the technique disclosed in Japanese Unexamined Patent Application Publication No. 3-163234 is applied to the upper surfaces of a piston 5 and a valve case 15. First, an outline of the structure will be described with reference to the drawings. When the hydraulic shock absorber is mounted on the vehicle, the vertical relationship is the same as that in FIG. 2. Hereinafter, the position or location of the members of the hydraulic shock absorber will be described with reference to the vertical relationship in FIG.

[0003] A hydraulic shock absorber mounted between a vehicle body and a wheel via a coupling member is provided with a piston 5 and a piston valve for controlling an extension side damping force which are assembled at a lower end portion of a piston rod 1 mounted on the vehicle body side. A cylinder 21, which is slidably housed and has a base valve for controlling a compression damping force at the lower end, is housed in an outer cylinder 22 attached to the wheel side, and a seal 24 and a rod guide 23 for shutting off outside air are formed. After the accommodated packing case 25 is inserted from above the outer cylinder 22, the upper end of the outer cylinder 22 is sealed by welding all around. A tank chamber D is formed between the cylinder 21 and the outer cylinder 22.

When the piston rod 1 rises in the cylinder 21 filled with hydraulic oil, the hydraulic oil in the closed upper chamber A is supplied to the lower chamber via a piston valve attached to the lower end of the piston rod 1. B, and the passage resistance at this time becomes the extension-side damping force. Hydraulic oil corresponding to the piston rod withdrawal volume that is insufficient due to the rise of the piston rod 1 is supplied to the lower chamber B from the bottom chamber C connected to the tank chamber D via a base valve attached to the lower end of the cylinder 21.

Next, a piston valve for controlling the extension-side damping force will be described. The lower end of the piston rod 1 is provided with a spigot portion 1A having a smaller diameter than the upper portion, in which a valve stopper 2 for regulating the maximum deflection of the check valve CV composed of the leaf valve 3 and an outer peripheral edge of the check valve CV are bent. Ring 7, leaf valve 3, supporting surface of leaf valve 3
Are sequentially inserted.

[0006] A piston 5 having a cylinder 21 partitioned into an upper chamber A and a lower chamber B and having a guide 5S wound around the outer periphery thereof has a structure shown in FIG.
As shown in (D), an upper boss portion 5E formed on the inner peripheral side on the upper surface side, a radial window frame 5F connected to the upper end surface of the upper boss portion and extending radially outwardly, and the radial A plurality of fan-shaped upper opening windows 5D are connected to the window frame and surrounded by an arc-shaped outer window frame 5G having a constant radius R from the axis Z. An outer peripheral port 5A communicating with the lower chamber B is bored in each of the upper opening windows,
An inner peripheral port 5B communicating with the annular lower opening window 5C is bored in the concave portion 5K formed between the upper opening windows.

Subsequently, a notched leaf valve 4 provided with a notch 4A on the outer peripheral side facing the lower opening window 5C and a leaf damping valve PV comprising a leaf valve 6 superimposed on the back surface of the notched leaf valve. And a ring seat 7 whose outer peripheral edge is the supporting diameter of the bending of the extension side damping valve PV, and a valve stopper 8 for regulating the maximum deflection of the extension side damping valve PV, and finally the piston nut 9 is screwed into the threaded portion of the spigot portion 1A. And a piston valve is formed by fastening with a tightening tool.

In a so-called elongation step in which the piston rod 1 rises in the cylinder 21 filled with hydraulic oil, in a so-called low-speed range where the piston speed is small and the pressure difference between the lower opening window 5C of the piston 5 and the lower chamber B is small. , Extension damping valve P
V covers the lower opening window 5C. Therefore, upper chamber A
The pressurized oil in the upper surface side of the piston 5K and the inner peripheral port 5B
Through the notch 4A of the notch leaf valve 4 facing the lower opening window 5C, and flows out to the lower chamber B through the notch 4A. Generates an extension-side damping force in the low-speed range that is proportional to the square.

As the piston speed increases, the flow rate passing through the notch 4A increases and the pressure difference between the lower opening window 5C and the lower chamber B also increases. As the piston speed approaches the middle speed range, the outer peripheral side of the extension damping valve PV disposed opposite to the lower opening window 5C overcomes the combined flexural rigidity, and becomes outside the lower opening window 5C. The hydraulic oil is pushed open from the seat portion and flows out into the lower chamber B, and the passage resistance at this time and the passage resistance of the inner peripheral port 5B generate an extension side damping force in the middle speed range and thereafter. The required damping force characteristics can be obtained by appropriately selecting the flexural rigidity of the extension-side damping valve PV including the notched leaf valve 4 and the leaf valve 6 and the passage area of the inner peripheral port 5B.

Next, a base valve for controlling the compression side damping force will be described. First, on the shaft 11A of the guide 11,
A valve stopper 12 for regulating the maximum deflection of the suction valve DV comprising a leaf valve 13, a ring seat 17 whose outer peripheral edge serves as a support for the deflection of the suction valve DV, a leaf valve 13, and a valve case 15 whose upper surface faces the leaf valve 13. Are sequentially inserted.

A lower chamber B fitted to the lower end of the cylinder 21
FIG. 1 shows a valve case 15 that separates the
As shown in parentheses in (D), an upper boss portion 15E formed on the inner peripheral side is provided on the upper surface side, and a radial window frame extending to the outer peripheral side in a radial direction connected to the upper end surface of the upper boss portion. A plurality of fan-shaped upper opening windows 15D surrounded by the outer window frame 15G and an arc-shaped outer window frame 15G connected to the radial window frame and having a constant radius R from the axis Z are provided. Each upper opening window has an outer peripheral port 15 communicating with the bottom chamber C.
A is drilled, and an inner peripheral port 15B communicating with the annular lower opening window 15C is drilled in the recess 15K formed between the upper opening windows.

Subsequently, a notched leaf valve 14 having a notch 14A provided on the shaft portion 11A of the guide 11 opposed to the lower opening window 15C of the valve case 15 on the outer peripheral side thereof and a lower portion of the leaf valve 14 A pressure side damping valve BV including a leaf valve 16 to be superimposed, a ring seat 17 having an outer peripheral edge serving as a support diameter of the bending of the pressure side damping valve BV, and a valve stopper 18 for regulating the maximum bending of the pressure side damping valve BV are sequentially assembled. A base valve is formed by caulking the lower end of the shaft 11A of the guide 11 with a tool.

In a so-called contraction step in which the piston rod 1 descends in the cylinder 21 filled with hydraulic oil, in a so-called low-speed range where the piston speed is small and the pressure difference between the lower opening window 15C of the valve case 15 and the bottom chamber C is small. , The compression side damping valve BV covers the lower opening window 15C. For this reason, the pressure oil in the lower chamber B corresponding to the invasion volume of the piston rod 1 excluding the replenishment of the upper chamber A whose volume increases via the piston 5 is reduced by the recess 15 on the valve case upper surface side.
K and the notched leaf valve 1 guided to the lower opening window 15C via the inner peripheral port 15B and facing the lower opening window 15C.
4 flows into the bottom chamber C through the notch 14A, and at this time, the passage resistance generates a low-side pressure-side damping force proportional to the square of the piston speed.

As the piston speed increases, the flow rate passing through the notch 14A increases, the pressure difference before and after the notch increases, and the lower chamber B through the concave portion 15K on the valve case upper surface side and the inner peripheral port 15B. The pressure difference between the lower opening window 15C communicating with the bottom case C and the bottom chamber C also increases.

For this reason, as the piston speed approaches the middle speed range, the outer peripheral side of the pressure side damping valve BV composed of the cut-out leaf valve 14 and the leaf valve 16 disposed opposite to the lower opening window 15C becomes larger. Overcoming the combined flexural rigidity, the hydraulic fluid is pushed out from the outer sheet portion of the lower opening window 15C and flows out into the bottom chamber C, and the passage resistance at this time and the passage resistance of the inner peripheral port 15B cause the medium speed region to be depressed. A subsequent compression damping force is generated. Flexural rigidity and inner peripheral port 1 of pressure side damping valve BV composed of notched leaf valve 14 and leaf valve 16
By appropriately selecting the passage area of 5B, required damping force characteristics can be obtained.

Here, a description will be given of the amount that is supplied to the upper chamber A. In a so-called low speed region where the piston speed is small and the pressure difference between the outer opening window 5D communicating with the lower chamber B via the outer peripheral port 5A of the piston 5 and the upper chamber A is small, the check valve CV composed of the leaf valve 3 is located outside. The opening window 5D is covered. For this reason, the pressure oil in the lower chamber B passes through the outer peripheral port 5A of the piston 5 and the notch 4A of the notch leaf valve 4.
Is supplied to the upper chamber A whose volume is increased through.

As the piston speed approaches the medium speed range, the pressure oil in the lower chamber B excluding the invading volume of the piston rod 1 passes through the outer peripheral port 5A of the piston 5 and passes through the non-return valve CV comprising the leaf valve 3. By overcoming the combined flexural rigidity, the check valve CV facing the upper opening window 5D is pushed open, and flows out into the upper chamber A whose volume increases. As the piston speed increases from the middle speed range to the high speed range and the differential pressure between the lower chamber B and the upper chamber A increases, the deflection of the check valve CV increases and the hydraulic oil smoothly flows into the upper chamber A where the volume increases. Be replenished.

Conversely, when the piston rod 1 rises,
In the low-speed range of the piston speed, the leaf valve 1 passes from the bottom chamber C through the outer peripheral port 15A of the valve case 15.
3 to overcome the bending rigidity of the suction valve DV, push the suction valve DV through the upper opening window 15D, and open the lower chamber B.
Will be replenished. As the piston speed increases from the medium speed range to the high speed range and the differential pressure between the bottom chamber C and the lower chamber B increases,
The deflection of the suction valve DV facing the upper opening window 15D increases, and the suction is smoothly replenished from the bottom chamber C to the lower chamber B whose volume is increased.

[0019]

When the hydraulic shock absorber switches from the expansion stroke to the contraction stroke, especially in a very low piston speed range, the pressure in the lower chamber B which generates the compression side damping force and the upper part in which the volume increases. Since the differential pressure between chambers A is small,
It is difficult to smoothly open the check valve CV without delay with this small differential pressure. However, the suction valve DV closes promptly by a return force based on the bending rigidity of the suction valve itself and a pressure difference between the lower chamber B and the bottom chamber C.

On the other hand, when switching from the contraction stroke to the extension stroke, the check valve CV is quickly closed by the return force based on the flexural rigidity of the check valve itself and the differential pressure between the upper chamber A and the lower chamber B. I do. However, the pressure in the bottom chamber C is equal to the pressure of the gas sealed in the tank chamber D (standard type: 1 bar, low pressure gas type:
Since the pressure difference between the bottom chamber C and the lower chamber B cannot exceed the above-mentioned sealed gas pressure, it is difficult to smoothly open the suction valve DV without delay with this small pressure difference.

For this reason, when switching from the extension stroke to the contraction stroke, the upper chamber A
Insufficient suction into the upper chamber A causes the pressure in the upper chamber A to temporarily decrease, so that the piston rod has the original pressure-side damping force generated on the base valve side in addition to the upper chamber A due to the pressure drop in the upper chamber A. 3 (B) because suction force is applied to the side.
As shown by the M section, the rising gradient of the compression-side damping force becomes steep, and the damping force becomes discontinuous.

Similarly, when switching from the contraction stroke to the extension stroke, insufficient suction into the lower chamber B occurs in a low piston speed range, and the pressure in the lower chamber B temporarily decreases. Since the suction force to the lower chamber B side due to the pressure drop of the lower chamber B is added to the original expansion-side damping force generated on the piston valve side, as shown by the L section in FIG. The rising slope of the side damping force becomes steep, causing discontinuity in the damping force.

As described above, the problems of the check valve CV when switching from the expansion stroke to the contraction stroke and the suction valve DV when switching from the contraction stroke to the extension stroke are similar.
Hereinafter, the problem will be described together in the form of a check valve CV (suction valve DV). As a method of opening the check valve CV (suction valve DV) smoothly, the bending rigidity is reduced or
Alternatively, it is conceivable to increase the pressure receiving area of the upper opening window 5D (15D).

However, the check valve CV (suction valve DV)
Since it is necessary to withstand the pressure in the upper chamber A (lower chamber B) corresponding to the extension-side damping force during the extension stroke (the compression-side damping force during the contraction stroke), there is a limit to the reduction in flexural rigidity, but the upper opening There is a space restriction in increasing the pressure receiving area of the window 5D (15D).

The opening pressure of the check valve CV (suction valve DV) depends on the deflection rigidity of the check valve CV (suction valve DV) itself and the radial direction from the upper boss 5E (15E) shown in FIG. Connecting surface between the radial window frame 5F (15F) extending to the outside, the arc-shaped outer window frame 5G (15G) connected to the radial window frame and having a constant radius R from the axis Z, and the check valve CV (suction valve DV). It is known that it is determined by the attraction force. In particular, since the pressure difference between the bottom chamber C and the lower chamber B cannot exceed the gas pressure of the gas sealed in the tank chamber D, the suction valve DV must be operated with a small pressure difference.
The effect of the attraction force on the valve opening pressure is large.

Here, the check valve CV (suction valve DV)
Since the inner peripheral side is fixed and is gradually opened from the outer peripheral side, the influence of the suction force on the valve opening pressure of the check valve CV (suction valve DV) depends on the outer window frame 5G (15G), 5F (15F). However, the suction force against the radial window frame 5F (15F) extending in the radial direction is as follows.
The influence on the valve-opening pressure is small due to the fact that it is gradually peeled off in the radial direction and it is on the inner peripheral side, so that it can be almost ignored.

The present invention has been made in view of the above circumstances, and an object thereof is to smoothly open a check valve CV (suction valve DV) without delay without reducing bending rigidity. An object of the present invention is to provide a hydraulic shock absorber that can be valved to suppress generation of abnormal noise due to discontinuity of damping force.

[0028]

SUMMARY OF THE INVENTION The present invention relates to a method of dividing a cylinder into an upper chamber and a lower chamber through a piston fastened to a piston rod, and a lower chamber through a valve case provided at a lower part of the cylinder. A chamber and a bottom chamber communicating with the tank chamber are defined. On the upper surface side of the piston or the valve case, an upper boss formed on the inner peripheral side, and an outer periphery of the upper boss connected to the upper end surface of the upper boss. A radial window frame extending radially to the side and an outer window frame connected to the radial window frame surrounded by a plurality of upper opening windows communicating with the lower chamber or the bottom chamber, and a check valve or a suction valve is provided. At the same time, a lower opening window communicating with the upper chamber or the lower chamber is provided on the lower surface side of the piston or the valve case, the extension damping valve or the compression damping valve is opposed, and a check valve arranged on the piston is provided. For the extension side damping valve The hydraulic shock absorber controls the compression damping force when the piston rod descends, while controlling the extension damping force when the piston rod extends. I do.

In order to solve the problem, a first means adopted by the present invention is as follows: "an outer side which forms an upper opening window connected to a radial window frame extending radially to an outer peripheral side of an upper boss portion of the piston or the valve case. The window frame has an arc-shaped or rectangular shape in which the distance from the axis of the piston or the valve case to the inner edge of the outer window frame increases from both ends connected to the radial window frame to the center.
It is shaped like a letter ".

The second means is that the outer window frame forming an upper opening window connected to a radial window frame extending in the radial direction on the outer peripheral side of the upper boss portion of the piston or the valve case is a piston or a valve case. The distance from the axis of the outer window frame to the inner edge of the outer window frame is an arc shape, a V-shape, or a straight line shape that decreases from both ends connected to the radial window frame to the center.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic shock absorber according to the present invention has the same basic structure as that of the prior art, and a piston rod 1 is mounted on a lower end of a cylinder 105 through a piston 105 mounted on the lower end thereof.
1 and is movably inserted into the first compartment 1 to define an upper chamber A and a lower chamber B. Further, a valve case 115 is fitted to the lower end of the cylinder 21 to similarly define a bottom chamber C communicating with the lower chamber B and the tank chamber D. A plurality of upper opening windows connected to the lower chamber B or the bottom chamber C are provided on the upper surface side of the piston 105 or the valve case 115.

Since the hydraulic shock absorber according to the present invention has the same basic structure as that of the prior art, only the parts different from those of the prior art in FIG. Further, the piston 105 and the valve case 115
Since the upper opening windows are similar in shape, they will be described below together in the form of the piston side (valve case side). Further, the mechanism of generation of the damping force is the same as that of the prior art, and a detailed description thereof will be omitted.

On the upper surface side of the piston 105 (valve case 115) according to the present invention, as shown in the first embodiment of FIG. 1A, an upper boss portion 105E formed on the inner peripheral side.
(115E) and a radial window frame 105F (115) which is continuous with the upper end surface of the upper boss portion and radially extends on the outer peripheral side thereof.
F) and the outer window frame 105G (1) connected to the radial window frame.
15G) and a plurality of upper open windows 105 surrounded by
D (115D). The difference from the conventional structure is
The distance R from the axis Z of the piston 105 (valve case 115) to the inner edge of the outer window frame 105G (115G) has an arc shape that increases from both ends connected to the radial window frame to the center.

When the check valve CV (suction valve DV) covers the upper opening window 105D (115D), the check valve CV (suction valve DV) abutting on the oil film of the hydraulic oil is in contact with the upper side. Attraction force is generated on the joint surface with the opening window 105D (115D). When the check valve CV (suction valve DV) opens from the upper opening window 105D (115D), the check valve CV (suction valve DV) overcomes its bending rigidity and bends from the outer peripheral side. , The outermost window frame 105G (115G) farthest from the axis Z.
Will be pushed open from the center.

When the check valve CV (suction valve DV) opens from the upper opening window 105D (115D), the peeling force that pushes against the above-mentioned suction force is different from the shaft center Z as in the conventional structure. The piston 105 according to the present invention is better than the case where the distance R to the inner edge of the outer window frame 5G (15G) is constant and peels off at once.
(Valve case 115), as shown in FIG.
Since it is smaller that the (115G) gradually and smoothly peels from the center to both ends, the valve opening pressure of the check valve CV (suction valve DV) can be reduced accordingly.

The outer window frame 105G (1
15G), the check valve CV (suction valve DV) only needs to be gradually and smoothly peeled from the center to both ends, so that a circle having the same radius of curvature or an ellipse having a changed radius of curvature is used.
The shape may be an arc formed of a part, a parabola whose curvature radius changes, or an arc formed of a part of a sine wave.

As can be seen from the description of the first embodiment, in order to smoothly release the check valve CV (suction valve DV) from the center to both ends, the outer window frame of the upper opening window is formed by the first embodiment. The central part described in the above is not limited to the arc shape bulging outward, but the central part may swell outward.

The upper opening window 205D (215D) of the second embodiment shown in FIG.
G) has a Λ-shape that is bent outward at the center. Also in this embodiment, the check valve CV (suction valve D
V) is pushed open from the center of the outer window frame 205G (215G) farthest from the axis Z of the piston 205 (valve case 215).

The upper opening window 305D (315D) of the third embodiment shown in FIG.
G) is linear. In the present embodiment, the check valve CV (suction valve DV) is connected to the outer window frame 305G farthest from the axis Z of the piston 305 (valve case 315).
(315G) is pushed open from both ends. In addition, since it is easy to assume if the bulges of the first and second embodiments are reversed inward, it is not shown in the drawing, but the effect of reducing the attraction force is that the outer window frame of the upper opening window 305D (315D) is not shown. Not only a linear shape but also an arc shape depressed inward or a V-shape bent inward at the center can be obtained.

In the first and second embodiments, the outer window frame is gradually and smoothly peeled from the center to both ends, and in the third embodiment, it is gradually and smoothly peeled from both ends to the center. The CV (suction valve DV) opens with a smaller differential pressure than the conventional structure, and can smoothly open from a very low speed range of the piston speed where the differential pressure is small. As a result, as shown in FIG. 3A, the discontinuity of the damping force is eliminated, and it is possible to prevent the occurrence of noises caused by the discontinuity.

[0041]

As described in detail above, in the first and second embodiments of the present invention, from the center to the both ends of the outer window frame, and in the third embodiment, from both ends of the outer window frame to the center. The check valve (suction valve) opens with a smaller differential pressure compared to the conventional structure, and smoothly opens from a very low speed range of the piston speed where the differential pressure is small, since the peeling gradually and smoothly over the portion. be able to. As a result, the discontinuity of the damping force is eliminated, and it is possible to prevent the occurrence of a clicking noise caused by the discontinuity.

[Brief description of the drawings]

FIG. 1A is a top view of a piston (valve case) according to a first embodiment. (B) It is a top view of the piston (valve case) concerning 2nd Embodiment. (C) It is a top view of the piston (valve case) concerning 3rd Embodiment. (D) It is a top view of the piston (valve case) which concerns on a prior art.

FIG. 2 is a longitudinal sectional view of a hydraulic shock absorber according to the related art (the present invention).

FIG. 3A is an example of a damping force characteristic of the hydraulic shock absorber according to the present invention. (B) An example of a damping force characteristic of a hydraulic shock absorber according to the related art.

[Explanation of symbols]

A upper chamber B lower chamber C bottom chamber D tank chamber BV compression side damping valve CV check valve DV suction valve PV expansion side damping valve R Radius Z from axis to inner edge of upper opening window Z axis (of piston or valve case) DESCRIPTION OF SYMBOLS 1 Piston rod 21 Cylinder 105 Piston 105C, 115C Lower opening window (piston side, valve case side) 105D, 115D Upper opening window (piston side, valve case side) 105E, 115E Upper boss portion (piston side, valve case side) 105F, 115F Radial window frame (piston side, valve case side) 105G, 115G Outer window frame (piston side, valve case side) 115 Valve case

Claims (2)

[Claims] 1. A bottom chamber which is divided into an upper chamber and a lower chamber via a piston fastened to a piston rod, and which communicates with the lower chamber and the tank chamber via a valve case provided at a lower part of the cylinder. And an upper boss formed on the inner peripheral side on the upper surface side of the piston or the valve case, and a radial window frame connected to the upper end surface of the upper boss and extending radially to the outer peripheral side of the upper boss. And a plurality of upper opening windows, which are surrounded by an outer window frame connected to the radial window frame and communicate with the lower chamber or the bottom chamber, are opposed to a check valve or a suction valve, and a piston or a valve case. On the lower surface side, a lower opening window communicating with the upper chamber or the lower chamber is provided, and the extension damping valve or the compression damping valve is opposed,
While controlling the extension damping force when the piston rod is extended by the check valve and the extension damping valve arranged on the piston, the piston rod descends by the suction valve and the compression damping valve arranged on the valve case. In the hydraulic shock absorber for controlling the compression side damping force at the time, the outer window frame forming an upper opening window connected to a radial window frame extending in the radial direction on the outer peripheral side of the upper boss portion of the piston or the valve case is a piston or a valve. A piston or valve case for a hydraulic shock absorber, wherein a distance from an axis of the case to an inner edge of the outer window frame is formed in an arc shape or a letter shape that increases from both ends connected to the radial window frame to a center portion. . 2. A bottom chamber which divides the inside of a cylinder into an upper chamber and a lower chamber via a piston fastened to a piston rod, and which communicates with the lower chamber and the tank chamber via a valve case provided at a lower part of the cylinder. And an upper boss formed on the inner peripheral side on the upper surface side of the piston or the valve case, and a radial window frame connected to the upper end surface of the upper boss and extending radially to the outer peripheral side of the upper boss. And a plurality of upper opening windows, which are surrounded by an outer window frame connected to the radial window frame and communicate with the lower chamber or the bottom chamber, are opposed to a check valve or a suction valve, and a piston or a valve case. On the lower surface side, a lower opening window communicating with the upper chamber or the lower chamber is provided, and the extension damping valve or the compression damping valve is opposed,
While controlling the extension damping force when the piston rod is extended by the check valve and the extension damping valve arranged on the piston, the piston rod descends by the suction valve and the compression damping valve arranged on the valve case. In the hydraulic shock absorber for controlling the compression side damping force at the time, the outer window frame forming an upper opening window connected to a radial window frame extending in the radial direction on the outer peripheral side of the upper boss portion of the piston or the valve case is a piston or a valve. A piston for a hydraulic shock absorber, wherein a distance from an axis of the case to an inner edge of the outer window frame is formed in an arc shape, a V shape, or a straight line shape which decreases from both ends connected to the radial window frame to a center portion. Or a valve case.