JP2000283208A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of noise when middle/high damping force is produced. SOLUTION: A hydraulic shock absorber is formed with a low speed square hole 48 opening to a piston rod side oil chamber 43B, and a vertical hole 49 communicating with the square hole 48, extending in an axial direction of a piston rod 29, opening to a piston side oil chamber 43A, and having a larger diameter than the square hole 48, on the piston rod 29. The square hole 48 is used as only one low speed square hole which communicates the piston side oil chamber 43A and the rod side oil chamber 43B.

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 interposed between a vehicle body such as a motorcycle and a wheel to absorb a shock from a road surface.

[0002]

2. Description of the Related Art Conventionally, as a hydraulic shock absorber, Japanese Utility Model Publication No. 63-329
As shown in FIG. 1 of JP-A-92-92, there is a piston provided with a low-speed square hole (orifice) for communicating a piston side oil chamber and a piston rod side oil chamber (prior art 1). In the prior art 1, the low-speed square hole provided in the piston functions so as to generate a damping force mainly when the piston speed is low.

As another conventional hydraulic shock absorber, as described in Japanese Utility Model Application Laid-Open No. 5-71485, a lateral hole is formed in a piston rod so as to open to a piston rod side oil chamber, and is connected to the lateral hole. The piston rod extends in the axial direction of the piston rod, forms a vertical hole that opens to the piston side oil chamber, a needle valve is inserted into the piston rod, and the distal end of the needle valve has a vertical hole. There is one that is provided to be able to move forward and backward with respect to a communication port (prior art 2). This prior art 2
Then, in the communication port of the vertical hole provided in the piston rod,
The throttle resistance adjusted by the needle valve mainly generates a damping force when the piston speed is low.

[0004]

However, the prior art has the following problems. In the prior art 1, when a medium-to-high speed damping force is generated, for example, on the extension side of the hydraulic shock absorber, the oil in the high-pressure rod-side oil chamber passes through the orifice (low-speed square hole) provided in the piston to the low-pressure piston-side oil chamber. When flowing in, a sudden drop in pressure produces a large amount of foam, which generates an abnormal sound (swish noise).

The low-speed square hole is structurally used so that a damping force acts from a low-speed region to a high-speed region of the piston speed. However, the hole has a small diameter in order to control the damping force in a low-speed region. Therefore, the higher the speed, the greater the amount of oil passing, that is, the higher the flow velocity of the oil, which causes the generation of a swish noise.

In the prior art 2, since the tip of the needle valve has a frusto-conical shape, the oil in the high-pressure rod-side oil chamber is moved to the side of the piston rod when the hydraulic shock absorber is, for example, at a medium-to-high speed. When passing through the outer circumference of the needle valve through the hole to the vertical hole and heading toward the piston side oil chamber, a turbulent flow is generated behind the cutting surface of the tip of the needle valve, and a large amount of bubbles are generated. (Swish sound).

SUMMARY OF THE INVENTION It is an object of the present invention to prevent generation of abnormal noise when a medium-to-high-speed damping force is generated in a hydraulic shock absorber.

[0008]

According to a first aspect of the present invention, a piston is provided at a tip of a piston rod inserted into a cylinder, and a piston rod side oil chamber and a piston side are defined in the cylinder by the piston. In a hydraulic shock absorber in which an oil chamber is formed and a piston is provided with a flow path communicating the piston rod-side oil chamber and the piston-side oil chamber, and a valve that generates a damping force at medium to high speeds is provided in the flow path of the piston. A low-speed square hole that opens in the piston-rod-side oil chamber in the piston rod, communicates with the square hole, extends in the axial direction of the piston rod, and opens in the piston-side oil chamber; A vertical hole having a diameter larger than that of the hole is formed, and the low-speed square hole is the only low-speed square hole communicating the piston rod-side oil chamber and the piston-side oil chamber.

According to a second aspect of the present invention, a piston is provided at a distal end of a piston rod inserted into a cylinder, and a piston rod-side oil chamber and a piston-side oil chamber defined by the piston are formed in the cylinder. A piston is provided with a flow path that communicates between the piston rod-side oil chamber and the piston-side oil chamber, and a valve that generates a damping force at medium to high speeds is provided in the flow path of the piston. A lateral hole that opens into the chamber, and a communication port that communicates with the lateral hole is provided; a longitudinal hole that extends in the axial direction of the piston rod and opens into the piston-side oil chamber is formed; In a hydraulic shock absorber in which a needle valve is inserted and a distal end portion of the needle valve is provided so as to be able to advance and retreat with respect to a communication port portion of the vertical hole, an outer periphery of a base end portion of the needle valve is formed in the vertical hole.絡口 portion is opposed to the peripheral, the flow area is adjustable between a base end portion outer periphery and said communication port inner peripheral,
Further, the tip of the needle valve is sharpened in a conical shape so as to extend into the vertical hole as much as possible.

[0010] According to a third aspect of the present invention, in the second aspect of the present invention, a sharp angle of a tip portion of the needle valve is set to 30 degrees or less.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the communication side of the vertical hole with the horizontal hole has a large diameter, and the opening side to the piston side oil chamber is provided. Is formed in a small diameter, and a step formed between the large diameter portion and the small diameter portion is formed in a tapered shape.

[0012]

According to the first aspect of the present invention, the following operations are provided. In the hydraulic shock absorber, a low-speed square hole that opens to the rod-side oil chamber and a vertical hole that opens to the piston-side oil chamber are provided in the piston rod, and both holes communicate with each other. Therefore, for example, when the oil in the high-pressure rod-side oil chamber passes through the low-speed squaring hole of the piston rod during the middle-to-high speed on the extension side of the hydraulic shock absorber, the outlet side of the squaring hole is not immediately the piston-side oil chamber, Since it is a vertical hole and does not have a sudden pressure drop, it does not generate a large amount of bubbles. And
Even if a small amount of bubbles is generated at the portion flowing into the vertical hole from the square hole, the bubbles gradually disappear in the long flow path formed by the vertical hole, and no abnormal noise (swish noise) is generated.
In addition, the vertical hole has a larger diameter than the square hole, and when oil flows from the vertical hole into the piston side oil chamber, a sudden drop in pressure is not caused, and new bubbles are generated, and as a result, abnormal noise ( No swishing sound is generated.

According to the present invention, the following effects are obtained. In the hydraulic shock absorber, the tip of the needle valve was sharpened in a conical shape. Therefore, when the oil in the high-pressure rod-side oil chamber passes through the outer periphery of the needle valve via the horizontal hole to the vertical hole of the piston rod and travels toward the piston-side oil chamber, for example, at a low speed on the extension side of the hydraulic shock absorber, There is no laminar flow around the sharp conical tip of the needle valve to generate a large amount of bubbles and, consequently, no generation of abnormal noise (swish noise).

According to the third aspect of the present invention, the following operations are provided. By setting the sharp angle at the tip of the needle valve to 30 degrees or less, the flow of oil around the tip is more reliably laminarized, and the generation of bubbles can be further reduced.

According to the present invention, there is provided the following operation. Since the vertical hole has a large diameter on the needle valve side and a small diameter on the piston side oil chamber side, when a small amount of bubbles is generated in the oil flowing around the needle valve, this bubble can be eliminated at the small diameter part .
In addition, since the connection from the large diameter portion to the small diameter portion is formed as a tapered flow passage, and turbulence is prevented from occurring in the oil flow in this portion, no new bubbles are generated in this portion.

[0016]

FIG. 1 is a sectional view showing a first embodiment of a hydraulic shock absorber, FIG. 2 is a sectional view showing an essential part of FIG. 1 taken out, FIG. 3 is an enlarged sectional view of an essential part of FIG. 4 is an enlarged cross-sectional view of a main part of the second embodiment, FIG. 5 is an enlarged cross-sectional view of a main part of the third embodiment, and FIG. 6 is an enlarged cross-sectional view of a main part of the fourth embodiment.

(First Embodiment) (FIGS. 1 to 3) As shown in FIG. 1, a front fork 10 (hydraulic shock absorber) includes a vehicle body side tube (inner tube) 11, a wheel side tube (outer tube) 12, and Are slidably fitted to be erect, a suspension spring 13 is interposed between the tubes 11 and 12, and the single-tube type damper 14 is installed to be erect.

A bush 15, an oil seal 16, and a dust seal 17 are fitted on the inner peripheral portion of the upper end of the wheel side tube 12 so that the outer peripheral portion of the vehicle side tube 11 is in sliding contact therewith. A bush 18 with which the inner peripheral portion of the tube 12 slides is fitted.

The vehicle body side tube 11 is an upper bracket 1
9A, and is supported on the vehicle body side via a lower bracket 19B, and the wheel side tube 12 is connected to the axle via an axle bracket 20.

The lower end of the damper cylinder 21 of the damper 14 is erected on the axle bracket 20 connected to the wheel side tube 12 via a cylinder receiver 22. At this time, a housing holder 25 of a base valve device 50, which will be described later, is screwed to a bottom bolt 24 which is inserted into the axle bracket 20 through a sealing member 23 in a liquid-tight manner, and is engaged with a base end inner periphery of the damper cylinder 21. Stopper ring 2
The damper cylinder 21 is fixedly held by the base of the housing holder 25 being axially locked to the housing 6. A cap 27 is provided at the upper end of the body side tube 11.
The base end of the piston rod 29 of the damper 14 is screwed to the cap 27,
Locked by lock nut 30. The tip of this piston rod 29 is inserted into the damper cylinder 21.

Axle bracket 20 of wheel side tube 12
A spring receiver 32 is press-fitted into the opening at the upper end of the damper cylinder 21 that has been raised. On the other hand, the body side tube 1
Piston rod 29 screwed into one cap 27
, A spring seat 33 is carried via a spring seat 33A and a washer 33B, which are supported on the back surface of the nut 30 directly below the cap 27. The suspension spring 13 described above is interposed between the spring receiver 32 and the spring receiver 33.
Is interposed.

Body side tube 11 and wheel side tube 12
Is provided with an oil chamber 34 and a gas chamber 35, and the gas confined in the gas chamber 35 forms a gas spring.
The hydraulic oil in the oil chamber 34 adjusts the spring constant of the gas chamber 35,
It contributes to the lubrication of the sliding contact bushes 15 and 18 between the vehicle body side tube 11 and the wheel side tube 12 and the wetting of the oil seal 16 at the upper end of the vehicle body side tube 12. Then, the resiliency of the suspension spring 13 and the gas spring absorbs the impact force that the vehicle receives from the road surface.

As shown in FIG. 2, the damper 14 has a piston valve device (extension-side damping force generator) 40 and a base valve device (compression-side damping force generator) 50. The damper 14 uses the damping force generated by the piston valve device 40 and the base valve device 50 to absorb the impact force of the suspension spring 13 and the gas spring, so that the body-side tube 11
And the expansion and contraction vibration of the wheel side tube 12 is suppressed.

A rod guide case 31 is inserted into the upper end opening of the damper cylinder 21. The rod guide case 31 is provided with a stopper ring 36 provided on an inner peripheral portion near the upper end of the damper cylinder 21, and a rod guide case 31. 21
And the washer 37 supported by the swaged portion of the opening. And the rod guide case 31
Holds the guide bush 38, and the guide bush 38 is mounted on the rod guide case 31 via the O-ring 38A so that the piston rod 29 can be slidably supported.

A spring holder 39B supported by a stopper ring 39A is fixed to an intermediate outer peripheral portion of the damper cylinder 21, and a rebound spring 39C is held by the spring holder 39B. When the front fork 10 is fully extended, the rebound spring 39C abuts against a rebound stopper 39D provided on the inner peripheral portion of the lower end of the vehicle body side tube 11, and performs a buffering action of extension and cut.

Hereinafter, the damping mechanism of the front fork 10 will be described. (Piston valve device 40) Piston valve device 40
As shown in FIG. 3, a washer 41A, a valve stopper 41B, a pressure side valve (check valve) 45A, a piston 42, and an extension side valve 44 are provided at the distal end of the piston rod 29.
A, insert washer 41C, valve stopper 41D,
These are fastened and fixed with nuts 47. Piston 42
Slidably contacts the inside of the damper cylinder 21 and partitions the inside of the damper cylinder 21 into a piston-side oil chamber 43A in which the piston rod 29 is not housed and a rod-side oil chamber 43B in which the piston rod 29 is housed. The piston 42 includes an expansion-side valve 44A, and is provided with an expansion-side flow path 44 that enables communication between the piston-side oil chamber 43A and the rod-side oil chamber 43B, and a compression-side valve (check valve) 45A. And a pressure side flow passage 45 that allows communication between the pressure side flow passage 45 and the rod side oil chamber 43B.

As shown in FIG. 3, the piston valve device 40 includes a piston rod 29 and a rod-side oil chamber 43B.
A low-speed square hole 48 is formed, which communicates with the low-speed square hole 48, extends in the axial direction of the piston rod 29, and opens in the piston-side oil chamber 43A.
A vertical hole 49 having a larger diameter is formed. The low-speed square hole 48 is connected to the piston-side oil chamber 43A and the rod-side oil chamber 4.
It is the only low-speed square hole that communicates with 3B.

Therefore, when the front fork 10 is compressed, the oil in the piston-side oil chamber 43A passes through the pressure-side flow path 45, opens the pressure-side valve 45A, and is guided to the rod-side oil chamber 43B.

When the front fork 10 is extended, when the relative speed between the damper cylinder 21 and the piston rod 29 is low, the oil in the rod-side oil chamber 43B passes through the low-speed square hole 48 and the vertical hole 49, and the piston-side oil chamber. 43A, and the expansion side damping force is generated by the throttle resistance due to the low-speed square hole 48 during this time.

When the front fork 10 is extended,
When the relative speed between the damper cylinder 21 and the piston rod 29 is medium to high, the oil in the rod-side oil chamber 43 </ b> B
Deflects the expansion side valve 44A through the piston side oil chamber 43A, and in parallel with the expansion side flow path 44 of the piston 42, passes through the aforementioned low-speed squaring hole and the vertical hole 49 to form the piston side. It is guided to the oil chamber 43A and generates a damping force on the extension side.

(Base Valve Device 50) In the base valve device 50, the housing holder 25 is screwed to the bottom bolt 24 inserted into the axle bracket 20 of the wheel side tube 12 as described above, and the housing holder 25 and the housing A pressure side valve 54A, a valve housing 52, an extension side check valve 55A, and a valve stopper 51A are sandwiched between the housing bolt 51 screwed to the holder 25. The valve housing 52 is provided for the damper cylinder 21
Is provided in a lower portion of the piston-side oil chamber 43A.
, A base valve chamber 53 is formed below. The valve housing 52 includes a compression-side valve 54A, and includes a compression-side flow path 54 that enables communication between the piston-side oil chamber 43A and the base valve chamber 53, and an extension-side check valve 55A.
An extension-side flow path 55 (not shown) is provided to enable communication between the piston-side oil chamber 43A and the base valve chamber 53. A low-speed square hole 56 that constantly communicates with the berth valve chamber 53 is formed in the pressure-side flow path 54 in a branched manner.

Therefore, when the front fork 10 is compressed, the piston rod 29 that has entered the damper cylinder 21
From the piston-side oil chamber 43A through the pressure-side flow path 54 and the low-speed squaring hole 56.
3. From the oil passage 59 on the wall surface of the damper cylinder 21 to the oil chamber 34
Is discharged. At this time, when the relative speed between the damper cylinder 21 and the piston rod 29 is low, the compression damping force is obtained by the throttle resistance of the low-speed square hole 56. Also,
When the relative speed between the damper cylinder 21 and the piston rod 29 is medium to high, the oil passing through the compression side flow passage 54 from the piston side oil chamber 43A bends the compression side valve 54A and is guided to the base valve chamber 53, and the compression side damping force. Is generated.

When the front fork 10 is extended, oil corresponding to the retreat volume of the piston rod 29 retreating from the damper cylinder 21 flows from the oil chamber 34 and the base valve chamber 53 through the extension side flow path 55 of the valve housing 52 to the piston side. The oil is returned to the oil chamber 43A.

Accordingly, the front fork 10 performs a damping action as follows. (At the time of compression) When the front fork 10 is compressed, the base valve device 50 generates a compression damping force due to the oil flowing through the low-speed squaring hole 56 of the valve housing 52 or the compression valve 54A, and the piston valve device 40 hardly generates a damping force. .

(Extension) When the front fork 10 is extended, the piston valve device 40 generates an extension-side damping force due to oil flowing through the low-speed square hole 48 of the piston rod 29 and / or the extension valve 44A of the piston 42. The valve device 50 hardly generates a damping force.

Due to the damping forces on the compression side and the extension side, the expansion and contraction vibration of the front fork 10 is suppressed.

However, according to the present embodiment, the following operations are provided. The front fork 10 includes a piston rod 29
A low-speed square hole 48 opening in the rod-side oil chamber 43B and a vertical hole 49 opening in the piston-side oil chamber 43A are provided in the two holes 48 and 49 so as to communicate with each other. Therefore, the front fork 10
For example, at medium speed on the extension side, the high pressure rod side oil chamber 43B
When the oil passes through the low-speed square hole 48 of the piston rod 29, the outlet side of the square hole 48 immediately
Since it is not the 3A but the vertical hole 49 and does not have a sudden pressure drop, a large amount of bubbles are not generated. Even if a small amount of bubbles is generated at the portion flowing from the square hole 48 to the vertical hole 49, the bubbles are gradually eliminated in the long flow path formed by the vertical hole 49, and an abnormal noise (swish sound) is generated. Does not reach. The vertical hole 49 has a larger diameter than the square hole 48,
When the oil flows into the piston side oil chamber 43A from the vertical hole 49, no sudden pressure drop occurs, and no new bubbles are generated, and no abnormal noise (swish noise) is generated.

(Second Embodiment) (FIG. 4) The second embodiment of FIG. 4 is substantially different from the first embodiment in that the piston rod 2 of the front fork 10
9 is separately provided as a rod end 29A, and this rod end 29A is screwed into the piston rod 29, and the same piston valve device 40 as in the first embodiment is provided on the rod end 29A. is there.

(Third Embodiment) (FIG. 5) The third embodiment of FIG. 5 is substantially different from the first embodiment in that a body side tube 1 constituting a front fork 10 is formed.
1 is that a damping force adjusting device 60 including a damping force adjusting rod 61 coupled to an operation member (not shown) provided on a cap 27 provided at an upper end portion of the device 1 is added.

That is, the damping force adjusting device 60 forms a horizontal hole 62 that opens to the rod side oil chamber 43B in the rod end 29A screwed to the piston rod 29, and a communication port (communicating with the horizontal hole 62). Valve seat) 63A,
A vertical hole 63 extending in the axial direction of the piston rod 29 and opening to the piston side oil chamber 43A is formed. Then, the piston rod 29 is formed as a hollow rod, and the damping force adjusting device 6 is used.
Reference numeral 0 denotes a distal end of the needle valve 64 provided in the damping force adjusting rod 61 inserted into the hollow portion, and a communication port 63A of the vertical hole 63.
Is movable in the axial direction. As a result, the needle valve 64 moves the outer periphery of the base end to the communication port 63A of the vertical hole 63.
Opposing the inner periphery, the flow path area that forms a low-speed square hole between the outer periphery of the base end portion and the inner periphery of the communication port portion 63A can be adjusted, and the tip end portion is sharpened conically. It extends as far as possible into the vertical hole 63.

The sharp angle θ of the tip of the needle valve 64
₁ is 30 degrees or less, more preferably 20 degrees or less (1 in this embodiment).
5 degrees). The vertical hole 63 has a large-diameter portion 63L on the side of the communication port 63A and a small-diameter portion 63S on the opening side to the piston-side oil chamber 43.

The difference between the damping action of the front fork 10 of the third embodiment and that of the first embodiment is that when the front fork 10 is extended and the relative speed between the damper cylinder 21 and the piston rod 29 is low, the rod side The oil in the oil chamber 43B is guided to the piston side oil chamber 43A through the communication port 63A of the vertical hole 63 having the needle valve 64, and the throttle resistance caused by the needle valve 64 (a low-speed square hole around the needle valve 64) during this time. This causes a damping force on the extension side. This damping force is adjusted by adjusting the position of the needle valve 64 by the damping force adjusting device 60.

Therefore, according to the third embodiment, the following operations are provided. In the front fork 10, the tip of the needle valve 64 is sharpened in a conical shape. Accordingly, for example, when the front fork 10 is at a low speed on the extension side, the high-pressure oil in the rod-side oil chamber 43B passes through the outer periphery of the needle valve 64 via the horizontal hole 62 to the vertical hole 63 of the piston rod 29 and enters the piston-side oil chamber 43A. When heading, the oil does not form a laminar flow around the sharp conical tip of the needle valve 64 to generate a large amount of bubbles, and thus no generation of abnormal noise (swish noise).

The sharp angle at the tip of the needle valve 64 is set to 30.
By setting the temperature to not more than the degree, the flow of the oil around the tip can be more reliably laminar, and the generation of bubbles can be further reduced.

The vertical hole 63 has a large diameter on the side of the needle valve 64,
Since the diameter is reduced on the side of the piston side oil chamber 43A, when a small amount of bubbles is generated in the oil flowing around the needle valve 64, the bubbles can be eliminated by the small diameter portion 63S.

(Fourth Embodiment) (FIG. 6) The fourth embodiment of FIG. 6 is substantially different from the third embodiment in that a large diameter portion 63 of a vertical hole 63 provided in a piston rod 29 is provided.
L and the small-diameter portion 63S are formed into a tapered portion 6
3T. In the following taper angle theta ₂ is 45 degrees of the tapered portion 63T, and more preferably 30 degrees or less (30 degrees in this embodiment). According to the fourth embodiment, in addition to the above-described operations of the third embodiment, the connection from the large-diameter portion 63L to the small-diameter portion 63S is a tapered flow path (tapered portion 63T), and the oil in this portion is formed. Since the generation of turbulence in the flow of air is prevented, there is an effect that new bubbles are not generated in this portion.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and the design can be changed without departing from the scope of the present invention. The present invention is also included in the present invention.

[0048]

As described above, according to the present invention, it is possible to prevent generation of abnormal noise when a medium-to-high-speed damping force is generated in a hydraulic shock absorber.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a hydraulic shock absorber.

FIG. 2 is a sectional view showing a main part of FIG.

FIG. 3 is an enlarged sectional view of a main part of FIG. 2;

FIG. 4 is an enlarged sectional view of a main part of a second embodiment.

FIG. 5 is an enlarged sectional view of a main part of a third embodiment.

FIG. 6 is an enlarged sectional view of a main part of a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Front fork (hydraulic shock absorber) 21 Damper cylinder 29 Piston rod 42 Piston 43A Piston side oil chamber 43B Piston rod side oil chamber 44 Expansion side flow path 44A Expansion side valve 45 Pressure side flow path 45A Pressure side valve 48 Low speed square hole 49 Vertical hole 62 Horizontal hole 63 Vertical hole 63A Communication port 63L Large diameter section 63S Small diameter section 63T Tapered section 64 Needle valve

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Aigo Gokai, 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Inventor Atsushi Kawaguchi 1-4-1, Chuo, Wako-shi, Saitama No. F-term in Honda R & D Co., Ltd. (Reference) 3D014 DD02 DE13 3J069 AA50 CC15 DD26 DD35 EE02 EE39

Claims (4)

[Claims] A piston is provided at a distal end portion of a piston rod inserted into a cylinder, and a piston rod-side oil chamber and a piston-side oil chamber defined by the piston are formed in the cylinder. In a hydraulic shock absorber provided with a flow path communicating with the piston side oil chamber and a valve for generating a damping force at medium and high speeds in the flow path of the piston, the piston rod has an opening in the piston rod side oil chamber. A low-speed square hole that communicates with the square hole, extends in the axial direction of the piston rod, opens into the piston-side oil chamber, and forms a vertical hole having a diameter larger than that of the square hole. A hydraulic shock absorber wherein the hole is the only low-speed square hole communicating the piston rod side oil chamber and the piston side oil chamber. 2. A piston is provided at a tip of a piston rod inserted into a cylinder, and a piston rod-side oil chamber and a piston-side oil chamber defined by the piston are formed in the cylinder. A flow path communicating with the piston-side oil chamber is provided, and a valve that generates a damping force at medium and high speeds is provided in the flow path of the piston, and a lateral hole that opens in the piston rod-side oil chamber is formed in the piston rod. And a communication port portion communicating with the lateral hole, extending in the axial direction of the piston rod, forming a vertical hole opening in the piston side oil chamber, inserting a needle valve into the piston rod, In a hydraulic shock absorber in which a distal end of the needle valve is provided so as to be able to advance and retreat with respect to a communication port of the vertical hole, a base end outer periphery of the needle valve is opposed to an inner circumference of the communication port of the vertical hole, The flow path area can be adjusted between the outer periphery of the base end portion and the inner periphery of the communication port portion, and the distal end portion of the needle valve is sharpened conically so as to extend as far as possible into the vertical hole. A hydraulic shock absorber. 3. The needle valve according to claim 2, wherein the sharp angle at the tip of the needle valve is 30.
3. The hydraulic shock absorber according to claim 2, wherein the pressure is equal to or less than the degree. 4. A step formed between the large diameter portion and the small diameter portion, wherein the side of the vertical hole communicating with the horizontal hole has a large diameter, and the opening side to the piston side oil chamber has a small diameter. The hydraulic shock absorber according to claim 2, wherein the hydraulic shock absorber is formed in a tapered shape.