JPH05231464A - Hydraulic shock absorber - Google Patents

Abstract

PURPOSE:To shorten the basic length and reduce machining manhours by disposing a gasket at the joint face between a piston and piston nut, as a sealing device for keeping a first-order lag pressure chamber oiltight, and bringing the inner peripheral surface of the gasket into contact with the outer peripheral surface of the socket-spigot joint part of a piston rod. CONSTITUTION:At the expansion stroke time when a piston 2 moves toward the upper operating oil chamber A side, oil in the upper operating oil chamber A passes the joint face between a piston 2 and the lower socket-spigot joint part 3e of a piston rod 3, and then the joint face between the socket-spigot joint part 3e and a piston nut 4 from the contact face between the piston 2 and piston nut 4 so as to leak onto the first-order lag pressure chamber R side, but the influence of this oil leak on the internal oil pressure is impeded by a gasket 18. Also the leak of oil onto the first-order lag pressure chamber R side from the joint face between the piston nut 4 and a block member 14 is impeded by an elastic body 17. With such constitution, there is no need to machine a seal groove in the joint face between the piston nut and the socket- spigot joint part of the piston rod so as to shorten the basic length of the whole hydraulic shock absorber and reduce machining manhours.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention aims to improve the riding comfort of a vehicle by automatically keeping the damping force low when the unsprung vibration frequency of a traveling vehicle enters a high frequency range above a set value. The present invention relates to an improvement in a seal structure of a variable frequency variable hydraulic shock absorber capable of appropriately adjusting a set high frequency range of an unsprung vibration frequency for keeping a generated damping force low.

[0002]

2. Description of the Related Art When a vibration frequency enters a high frequency range above a set value, a phase difference is imparted to the hydraulic pressure transmitted from the upper working oil chamber to the damping force adjusting pressure chamber, that is, the upper working oil chamber is generated. Hydraulic pressure is transmitted as a first-order lag to a pressure chamber for damping force adjustment (hereinafter referred to as first-order lag pressure chamber) to keep the generated damping force low, and it is also possible to appropriately adjust the set high-frequency range for keeping the generated damping force low. A variable frequency dependent hydraulic shock absorber that can be used is, for example, the first patent application published in 1991.
There is one disclosed in Japanese Patent No. 68435.

In this device, a variable orifice is provided in a passage connecting the upper hydraulic oil chamber and the first-order lag pressure chamber, and when the vibration frequency enters a high frequency range above a set value, the upper hydraulic oil is made to flow through the variable orifice. The generated hydraulic pressure in the chamber is transmitted to the primary delay pressure chamber with a phase difference, and the generated damping force is kept low by suppressing the hydraulic pressure rise in the primary delayed pressure chamber, and the generated damping force is kept low by adjusting the variable orifice. The range can be adjusted appropriately.

[0004]

However, in such a type of dependent frequency variable hydraulic shock absorber, the opening area of the variable orifice for controlling the pressure gain in the first-order lag pressure chamber is generally quite small. Therefore, if oil leaks from the upper hydraulic oil chamber to the temporarily delayed pressure chamber during the expansion stroke of the hydraulic shock absorber, the control of the pressure gain in the temporarily delayed pressure chamber by the variable orifice causes a serious error.

Therefore, in order to prevent this leakage, in the prior art, a seal member is interposed between the pilot rod inlay portion and the piston nut, and this seal member allows the piston and piston rod inlay portion, and the piston and piston. Oil is prevented from leaking from each joint surface of the nut through the joint surface of the piston rod inlay portion and the piston nut into the primary lag pressure chamber.

At the same time, a seal member is also provided on the joint surface between the through hole of the piston nut and the guide portion of the block member to prevent oil from leaking from this portion into the pressure chamber for a temporary delay. I am trying to do it.

Therefore, either the outer peripheral surface of the spigot portion of the piston rod or the inner peripheral surface of the through hole of the piston nut must be grooved to provide the former seal member. Not only does the length of the parts to be machined increase and the basic length of the entire hydraulic shock absorber increases, but it also leads to an increase in cost.

Similarly, in order to provide the latter seal member, either the inner peripheral surface of the through hole of the piston nut or the outer peripheral surface of the guide portion of the block member must be grooved. There is a problem that it leads to an increase in the basic length of the vessel itself and an increase in cost.

Therefore, an object of the present invention is to provide an improved seal capable of shortening the overall basic length of the hydraulic shock absorber, and at the same time cost reduction by reducing the number of processing steps and the number of parts. An object of the present invention is to provide a hydraulic shock absorber of a structure-dependent variable frequency type.

[0010]

In order to achieve the above object, according to the present invention, a variable orifice is interposed in a passage connecting an upper hydraulic oil chamber and a pressure chamber for adjusting a damping force, and vibration is caused. When the frequency enters the high frequency range above the set value, this variable orifice gives a phase difference to the hydraulic pressure transmitted from the upper hydraulic oil chamber to the damping force adjusting pressure chamber, and the damping force adjusting pressure chamber is set as the primary delay pressure chamber. In the hydraulic shock absorber of the variable frequency dependent type, the damping force can be adjusted appropriately by adjusting the variable orifice to keep the generated damping force low and the generated damping force kept low by adjusting the variable orifice. As a seal device that keeps the pressure chamber for oil in an oil-tight state, a gasket is arranged on the joint surface of the piston and piston nut,
The structure is such that the inner peripheral end of this gasket is brought into contact with the outer peripheral surface of the spigot portion of the piston rod.

Also, in this type of dependent frequency variable type hydraulic shock absorber, a sealing function is provided between the shoulder portion of the piston nut and the step portion of the block member as a sealing device for keeping the primary delay pressure chamber in an oil-tight state. The structure is such that an elastic body having

[0012]

As a result, according to the present invention, the oil that tries to enter the primary lag pressure chamber from the joint surfaces of the piston and the piston rod spigot portion and the piston and the piston nut through the joint surfaces of the piston rod spigot portion and the piston nut. Without a structure in which a seal member is placed in a processing groove formed in the joint surface part of the piston rod spigot part and the piston nut to prevent leakage, simply insert a gasket between the piston and the piston nut. It can be achieved simply by providing the structure.

Further, even when oil leaks from the joint surface between the through hole of the piston nut and the guide portion of the block member and tries to go around into the pressure chamber temporarily, the through hole of the piston nut and the block member are also prevented. An elastic body having a sealing function between the shoulder portion of the piston nut and the stepped portion of the block member without having a structure in which the seal member is housed in the processing groove formed in the joint surface portion of the guide portion to block the seal member. This can be achieved simply by adopting a structure in which it is sandwiched and intervened.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

As shown in FIG. 1, a hydraulic shock absorber according to an embodiment of the present invention comprises a cylinder 1 having a closed cylindrical body, a piston 2 slidably inserted into the cylinder 1, and a piston 2 to a cylinder. 1 and a piston rod 3 extending outwardly through the upper end sealed portion.

The piston 2 is interposed in the lower end fitting portion 3e of the piston rod 3, and is fixed to the piston rod 3 by a piston nut 4 screwed from below into the lower end spiral portion 3f of the piston rod 3. Divides the inside of the cylinder 1 into an upper hydraulic oil chamber A on the rod side and a lower hydraulic oil chamber B on the head side, and the hydraulic oil in the upper hydraulic oil chamber A is discharged from the piston 2 during the extension stroke of the hydraulic shock absorber. By letting it flow into the lower hydraulic oil chamber B through the extension side damping force generation mechanism, the extension side damping force generation mechanism part generates the damping force during the extension stroke.

To this end, the piston 2 is provided with two sets of port groups, an outer peripheral side port 2a and an inner peripheral side port 2b, which communicate the upper hydraulic oil chamber A and the lower hydraulic oil chamber B,
The outer peripheral side port 2a group has its lower end directly opened to the lower hydraulic oil chamber B, and its upper end communicates with the upper hydraulic oil chamber A via a non-return valve 5 that opens toward the upper hydraulic oil chamber A side.
The inner peripheral side port 2b group has a piston nut 4 at the lower end.
A presser foot is provided which communicates with the extension side damping force generating mechanism side through a passage 4b bored in the non-return valve 5 and has a spacer 19 between the through hole 5b bored in the non-return valve 5 and the non-return valve 5. It communicates with the upper hydraulic oil chamber A through the opening 6b of the leaf spring 6 and the through hole 7b of the valve stopper 7 that limits the lift amount of the non-return valve 5.

On the other hand, an extension side damping force generating mechanism is provided from inside the lower end of the piston nut 4 to inside the piston rod 3.
A control mechanism for controlling this extension side damping force generation mechanism is housed.

The extension side damping force generating mechanism is composed of a piston nut 4
Annular rib 8 of the supporting member 8 which is crimped to the inside of the lower end of the
e and the annular rib 9e of the valve seat 9 arranged so as to face the upper surface of the support member 8, the outer circumference is sandwiched between the fixed leaf valve 10 and the control mechanism is the valve seat 9 A push member 11 fitted vertically movable on the inner peripheral surface of the
2, a leaf spring 13 which is caulked, a block member 14 arranged above them, a control valve 15 having a variable orifice 15c rotatably accommodated in a through hole 3c penetrating the piston rod 3 and the like. It consists of

The valve seat 9 of the extension side damping force generating mechanism is
A plurality of through holes 9b arranged side by side on a concentric circle, and an annular groove 9d formed on the lower surface in communication with these through holes 9b,
Push member 11 on the control mechanism side, leaf spring 13
And the block member 14, the upper end of the cap-shaped member 16 having the opening 16b is hooked on the block member 14, and the lower end of the cap-shaped member 16 is fitted to the valve seat 9 to be preassembled as a sub-assembly. There is.

The stepped portion 14e of the block member 14 and the shoulder portion 4e of the piston nut 4 are sub-assembled.
By inserting the guide portion 14f of the block member 14 into the through hole 4c of the piston nut 4 with the elastic body 17 having a sealing function, which is one of the features of the present invention, interposed between The elastic body 17 seals the joint surface between the piston nut 4 and the block member 14 in an oil-tight manner, and always presses the entire sub-assembled parts downward.

Thus, the leaf valve 10 has the elastic body 1.
The outer periphery is sandwiched between the annular rib 8e of the support member 8 and the annular rib 9e of the valve seat 9 by the restoring force of 7, and the inner peripheral upper surface of the leaf valve 10 is seated on the seat portion 9f of the inner peripheral lower surface of the valve seat 9. The annular groove 9d formed between the annular rib 9e and the seat portion 9f of the valve seat 9 is closed by press contact, and the upper hydraulic oil chamber A is closed by the valve stopper 7
From the through hole 7b to the opening 6b of the leaf spring 6, the inner peripheral side port 2b of the piston 2, and the passage 4 of the piston nut 4.
The leaf valve 10 blocks the passage to the lower hydraulic oil chamber B through b, the opening 16b of the cap-shaped member 16, the through hole 9b of the valve seat 9 and the annular groove 9d.

The leaf valve 10 is clamped by utilizing the restoring force of the elastic body 17 because the leaf valve 10 is clamped by the dimension error of the support member 8, the valve seat 9, the cap-shaped member 16 and the like. This is to prevent backlash.

As a result, the elastic body 17 performs not only the sealing action between the piston nut 4 and the block member 14 but also the pushing action of the sub-assembly member. Therefore, the sealing groove machining required in the conventional apparatus is performed. Since the number of parts can be reduced, the number of processing steps can be reduced, and the spring member for pressing the sub-assembly member can be omitted. Therefore, the number of parts can be reduced, and the cost can be reduced in combination.

The control mechanism for controlling the extension side damping force generating mechanism is such that the push member 11 fitted vertically movably on the inner peripheral surface of the valve seat 9 and the pin 12 is caulked to the center of the push member 11. It has a leaf spring 13.

The leaf spring 13 is clamped at its outer peripheral portion between the valve seat 9 and the block member 14 at the time of the above subassembly, and the spring force of the leaf spring 13 normally keeps the push member 11 in the upper position.

Further, in this state, the valve seat 9
The lower surface sheet portion 11e of the push member 11, which is formed to have the same thickness as the above, is close to the upper surface on the inner peripheral side of the leaf valve 10 and faces or contacts the upper surface.

A first-order lag pressure chamber R for damping force adjustment is formed between the leaf spring 13 connected to the push member 11 with the pin 12 and the lower surface of the block member 14, and the first-order lag pressure chamber R is formed. The internal passage of the control valve 15 rotatably fitted into the through hole 14c of the block member 14 through the through hole 4c of the piston nut 4 and the adjusting through hole 3c formed in the piston rod 3. The variable orifice 15c leads from 15d.

On the other hand, the inner peripheral surface of the piston 2 is provided with an annular groove 2c located on the same plane as the variable orifice 15c. On the other hand, the annular groove 2c is, on the one hand, the lower end inlay portion 3e of the piston rod 3. The variable orifice 15c is communicated through the through hole 3d formed in the piston 2, and the other is communicated with the inner peripheral side port 2b of the piston 2 through the through hole 2d formed in the piston 2.

Thus, in the upper hydraulic oil chamber A, from the through hole 7b of the valve stopper 7 to the opening 6b of the leaf spring 6,
Inner peripheral side port 2b of piston 2, through hole 2d of piston 2, annular groove 2c, through hole 3d of lower end spigot portion 3e of piston rod 3, variable orifice 15c of control valve 15 and internal passage 15d, piston rod 3 Through hole 3c of lower end inlay part 3e and block member 1
To the primary delay pressure chamber R through the through hole 14c of 4,
The hydraulic pressure in the upper hydraulic oil chamber A is guided to the primary delay pressure chamber R via the variable orifice 15c.

From the control valve 15, the piston rod 3
The control rod 20 extends to the outside through the through hole 3c, and the opening area of the variable orifice 15c can be controlled by rotationally controlling the control valve 15 from the outside via the control rod 20.

A seal 21 is kept oil-tight between the control rod 20 and the through hole 3c of the piston rod 3, and
Below the control valve 15, a cylindrical stopper 22 for preventing the control valve 15 from slipping out of the control rod 20 is fitted inside the through hole 3c of the piston rod 3. There is.

On the other hand, above the valve stopper 7, there is provided a disk 23 having an annular groove 23c formed on its inner peripheral surface.

On the one hand, the annular groove 23c of the disk 23 communicates with the annular groove 15e formed on the outer peripheral surface of the control valve 15 from the through hole 3f formed in the lower end inlay portion 3e of the piston rod 3 and this annular groove 15e. Through hole 15f formed in the control valve 15 and the internal passage 1 of the control valve 15
5d through the through hole 3c in the lower end spigot portion 3e of the piston rod 3, and on the other hand, through the through hole 23d formed in the disk 23, it opens to the upper hydraulic oil chamber A side, whereby the primary lag pressure chamber R Through the through hole 14c of the block member 14, the through hole 4c of the piston nut 4, the through hole 3c of the lower end spigot portion 3e of the piston rod 3, the internal passage 15d of the control valve 15, the through hole 15f and the annular groove 15e. Irrespective of the rotation control of the control valve 15, the lower end fitting part 3 of the piston rod 3
e through hole 3f, annular groove 23c of disk 23 and through hole 23
It communicates with the upper hydraulic oil chamber A side through d.

A check valve 24 is provided on the upper portion of the disk 23 so as to open toward the upper hydraulic oil chamber A side. Further, a check spring 26 is provided on the upper portion of the check valve 24 with a spacer 25 interposed therebetween. And a valve stopper 27.

The valve stopper 27, check spring 26, spacer 25, check valve 24,
Disc 23, valve stopper 7, leaf spring 6, spacer 19, non-return valve 5, piston 2, and gasket 1 forming another feature of the present invention.
8 in succession so that the lower end fitting part 3 of the piston rod 3
By inserting the piston nut 4 into the lower end spiral portion 3f of the piston rod 3 from below and tightening them, the piston nut 4 is inserted between the upper end of the piston nut 4 and the step portion 3g of the piston rod 3. Is fixed.

As shown in FIGS. 1 and 2, the gasket 18 sandwiched between the lower surface of the piston 2 and the upper surface of the piston nut 4 is made of, for example, metal rubber or the like, and has an inner circumference of the piston 2. A through hole 18b is formed in a portion of the piston nut 4 that matches the passage 4b of the side port 2b, and the inner peripheral surface of the piston rod 3 abuts on the outer peripheral surface of the lower spigot portion 3e of the piston rod 3 to form the spigot portion 3e and the piston nut 4. The joint surface is oil-tightly sealed.

This eliminates the need for sealing groove machining, which is required on any of the joint surfaces of the lower end inlay portion 3e of the piston rod 3 and the piston nut 4 in the conventional apparatus, and the machining man-hours are reduced accordingly. Can be down.

According to the hydraulic shock absorber configured as described above, during the compression stroke in which the piston 2 moves toward the lower hydraulic oil chamber B side during the expansion / contraction operation, regardless of the vibration frequency. While the hydraulic oil in the lower hydraulic oil chamber B pushes the non-return valve 5 from the outer peripheral side port 2a of the piston 2 to flow into the upper hydraulic oil chamber A,
An amount of hydraulic oil corresponding to the intrusion volume of the piston rod 3 flows to the reservoir side through a well-known base valve or the like (not shown), and at this time, the base valve gives flow resistance to the oil to generate a compression side damping force.

On the contrary, during the extension stroke in which the piston 2 moves toward the upper working oil chamber A side, the working oil in the upper working oil chamber A is passed through the through hole 7b of the valve stopper 7.
To the opening 6b of the leaf spring 6, the inner peripheral port 2b of the piston 2, the through hole 18b of the gasket 18, the passage 4b of the piston nut 4, the opening 16b of the cap-shaped member 16.
Also, while passing through the through hole 9b of the valve seat 9 and bending the inner peripheral side of the leaf valve 10 downward to generate the extension side damping force, the flow proceeds to the lower hydraulic oil chamber B, while the extension side damping force itself is the upper part. The hydraulic pressure generated in the hydraulic oil chamber A is from the inner peripheral side port 2b of the piston 2 to the through hole 2d and the annular groove 2c, the through hole 3d of the lower spigot portion 3e of the piston rod 3, the variable orifice 15c of the control valve 15, and the same inside. Passage 1
5d, through hole 3c of piston rod 3, piston nut 4
Through the through hole 4c of the block member 14 and the through hole 14c of the block member 14 to the primary delay pressure chamber R, and the hydraulic pressure is used to push the push member 1
1 acts against the leaf spring 13 to push it downward.

In this case, the oil in the upper working oil chamber A flows from the joint surface of the piston 2 and the lower spigot portion 3e of the piston rod 3 and the contact surface of the piston 2 and the piston nut 4 to the spigot portion 3e and the piston nut 4. The gasket 18 prevents leakage to the first-order lag pressure chamber R side through the joint surface and affects the internal hydraulic pressure of the first-order lag pressure chamber R, and also the first-order lag from the joint surface of the piston nut 4 and the block member 14. The elastic body 17 blocks the leak to the pressure chamber R side.

Therefore, if the vibration frequency during the extension stroke is equal to or lower than the vibration frequency set by the variable orifice 15c at that time, the hydraulic pressure generated in the upper hydraulic oil chamber A (as described above = extension side damping force) is It acts on the first-order lag pressure chamber R through the variable orifice 15c, pushes down the push member 11 to bend the inner peripheral end of the leaf valve 10 downward, and increases the initial load of the leaf valve 10 to generate a predetermined damping force. When the vibration frequency in the extension stroke exceeds the vibration frequency set by the variable orifice 15c, the piston 2 moves to the compression stroke before the hydraulic pressure generated in the upper working oil chamber A is transmitted to the first-order lag pressure chamber R through the variable orifice 15c. Since the variable orifice 15c performs the primary delay action, the hydraulic pressure in the primary delay pressure chamber R does not rise and is kept at a low value. Since the push member 11 does not bend the inner peripheral end of the leaf valve 10 downward while keeping the raised position by the spring force of the leaf spring 13, the generated damping force becomes lower than a predetermined value, and the frequency-dependent type with a high cut effect is obtained. Acts as a hydraulic shock absorber.

From this, the control valve 15 is operated from the outside through the control rod 20 to change the variable orifice 15c.
If the opening area of is increased, the phase delay of the hydraulic pressure transmitted from the upper hydraulic oil chamber A to the first-order lag pressure chamber R is small and the gain is high. Therefore, the expansion side damping force characteristic becomes a high damping force and the opening area of the variable orifice 15c is reduced. If it is made smaller, the frequency dependence becomes larger and the extension side damping force characteristic becomes a high cut characteristic.Moreover, by appropriately selecting the size of this opening area, the high cut characteristic for the input frequency can be freely selected. If the opening area of the variable orifice 15c is set to zero, the hydraulic pressure in the primary lag pressure chamber R does not rise and is always kept low, so that the extension side damping force characteristic becomes a low damping force, and thus this hydraulic shock absorber It also functions as a variable frequency hydraulic shock absorber.

However, with this alone, the variable orifice 1
When the opening area of 5c is switched from a large state to a small state or a closed state, or the variable orifice 15
When the expansion stroke vibrates at a low frequency and the compression stroke vibrates at a high frequency regardless of the opening area of c, the upper hydraulic chamber A
The hydraulic pressure in the primary lag pressure chamber R hardly decreases even at the end of the compression stroke in which the hydraulic pressure generated in the upper hydraulic chamber A
The oil pressure in the first-order lag pressure chamber R is higher than the oil pressure in the inside, and in any case, the damping force generated in the extension stroke is always a high damping force, and the damping force frequency characteristic (damping force mode) However, in this case, the oil pressure in the upper hydraulic oil chamber A decreases during the compression stroke and the pressure in the primary delay pressure chamber R decreases. When a pressure difference is generated between the hydraulic pressure and the hydraulic pressure, the check valve 24 immediately opens to immediately return the amount of hydraulic oil that has flowed into the primary lag pressure chamber R to the upper hydraulic oil chamber A during the extension stroke, and by the end of the compression stroke. The hydraulic pressure in the primary delay pressure chamber R is made equal to the hydraulic pressure in the upper hydraulic oil chamber A.
Therefore, even in the continuous vibration state, the damping force frequency characteristic can be reliably switched by adjusting the opening area of the variable orifice 15c.

[0045]

As described above, according to the present invention, by adopting the seal structure according to claim 1, it is not necessary to form a seal groove on the joint surface of the spigot portion of the piston rod and the piston nut. The basic length of the shock absorber as a whole can be shortened, and the number of processing steps can be reduced to reduce the cost.

Further, according to the seal structure of the second aspect, it is possible to omit the processing of the seal groove on the joint surface of the piston nut and the block member. Therefore, as in the first aspect, the basic length of the entire hydraulic shock absorber is shortened. In addition to reducing the number of processing steps, the seal member itself also has a spring action for removing backlash, so the number of parts is reduced and the cost is greatly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of a hydraulic shock absorber according to an embodiment of the present invention in a cut-away manner.

FIG. 2 is a plan view of a gasket.

[Explanation of symbols]

 A Upper hydraulic oil chamber R Primary delay pressure chamber (pressure chamber for adjusting damping force) 2 Piston 3 Piston rod 3e Lower end spigot 4 Piston nut 14 Block member 15c Variable orifice 17 Seal member 18 Gasket 18b Through hole

Claims (2)

[Claims] 1. A variable orifice is provided in a passage connecting an upper hydraulic oil chamber and a pressure chamber for damping force adjustment, and when the vibration frequency enters a high frequency range equal to or higher than a set value, the variable hydraulic orifice is used for the upper hydraulic oil. Generated by operating the damping force adjusting pressure chamber as a first-order lag pressure chamber by giving a phase difference to the hydraulic pressure that is transmitted from the chamber to the damping force adjusting pressure chamber, and also by adjusting the variable orifice. A variable frequency dependent type hydraulic shock absorber capable of appropriately adjusting the high frequency range for keeping the damping force low.A gasket is provided on the joint surface of the piston and piston nut as a seal device for keeping the primary delay pressure chamber in an oil-tight state. Is provided and the inner peripheral end of the gasket is brought into contact with the outer peripheral surface of the spigot portion of the piston rod. 2. A variable orifice is provided in a passage connecting the upper hydraulic oil chamber and the damping force adjusting pressure chamber, and when the vibration frequency enters a high frequency range higher than a set value, the upper hydraulic oil is moved by the variable orifice. Generated by operating the damping force adjusting pressure chamber as a first-order lag pressure chamber by giving a phase difference to the hydraulic pressure that is transmitted from the chamber to the damping force adjusting pressure chamber, and also by adjusting the variable orifice. In a variable frequency dependent type hydraulic shock absorber capable of appropriately adjusting the high frequency range for keeping the damping force low, as a seal device for keeping the first-order lag pressure chamber in an oil-tight state, a step portion of a block member and a piston nut A hydraulic shock absorber in which an elastic body having a sealing function is interposed between shoulders.