JPH10339346A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfy both control stability and comfortableness. SOLUTION: In a piston 4 of a liquid pressure shock absorber, a damping force generating mechanism 16 for generating damping force and a damping force variable mechanism 17 for changing damping force in accordance with a stroke of the piston 4 are provided. In the damping force variable mechanism 17, at small stroke time, spring force of an elastic unit 34, 35 is additionally applied to a piston rod 5 since between bypass passages 32e, 32f are interrupted by a slider 33. Consequently, even when damping force is decreased, virtual damping force is increased, control stability is improved by improving comfortableness. At large stroke time, spring force is increased, control stability can be ensured. At extremely large stroke time, by connecting the bypass passages 32e, 32f, spring force of the elastic unit 34, 35 is saturated, to be free from flapping or the like.

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, and more particularly, to a hydraulic shock absorber configured to satisfy both driving stability and riding comfort of an automobile.

[0002]

2. Description of the Related Art Hitherto, as a shock absorber for a vehicle, there has been known a hydraulic pressure damping device for damping an impact by a fluid resistance of a hydraulic fluid generated by an operation of a piston sliding in a cylinder. This type of hydraulic shock absorber has a configuration in which a piston slides in a cylinder due to an increase in load applied to wheels, and a disk valve provided on the piston that slides in the cylinder opens and closes according to a differential pressure. When the hydraulic fluid filled in the upper or lower fluid chamber in the cylinder passes through a passage provided in the piston and moves in the direction opposite to the sliding direction, a damping force is generated.

That is, in the hydraulic shock absorber, when the piston slides in the compression direction, the upper valve provided on the upper part of the piston operates in the opening direction, and the hydraulic fluid in the lower liquid chamber passes through the compression-side communication passage penetrating the piston. And move to the upper liquid chamber. When the piston slides in the extension direction, the lower valve provided in the lower part of the piston operates in the opening direction, and the hydraulic fluid in the upper liquid chamber passes through the communication passage on the extension side of the piston and moves to the lower liquid chamber.

[0004] An example of this type of hydraulic shock absorber is disclosed in Japanese Utility Model Laid-Open No. 63-147946. The hydraulic shock absorber described in this publication is provided with a first disk valve and a second disk valve that open and close in accordance with the piston speed on the piston. Only the disc valve opens and the hydraulic fluid passes through an orifice provided in the piston to generate a damping force.

Further, when the piston speed is equal to or higher than a predetermined value, both the first disc valve and the second disc valve open, and the flow rate of the hydraulic fluid flowing through the passage of the piston increases. Therefore, as the piston speed increases, the damping force increases at a constant rate. Therefore, in the hydraulic shock absorber, in the low speed range where the piston speed is small, the damping force generated by the first disk valve by reducing the flow rate of the working fluid is suppressed to a small value, and the medium speed range where the piston speed further increases and moves. Is set so that the damping force generated when the first disk valve is opened increases at a constant rate with respect to the piston speed. And
If a large load is input and the piston speed increases,
The first disc valve and the second disc valve are both set to open so that the damping force sharply increases with respect to the piston speed.

[0006]

In the above-mentioned hydraulic shock absorber, both the first and second disc valves are opened to increase the flow rate passing through the communication passage of the piston in order to enhance the riding comfort. As a result, the ride comfort can be improved by reducing the damping force, but on the other hand, there is a problem that the steering stability is reduced.

Further, if the second disk valve delays the valve-opening operation with respect to the piston speed to improve the steering stability, the damping force is increased and the riding comfort is reduced. For example, when the damping force of the hydraulic shock absorber is set to “large” in order to improve steering stability, rugged vibrations are transmitted to the occupants of the vehicle when traveling on a pavement with small irregularities.

That is, in the above-mentioned hydraulic shock absorber,
While the damping force required for ride comfort is "small",
Since the damping force required for steering stability is "large", the required damping force characteristics are inconsistent. Therefore, conventionally, in order to change the damping force according to the piston speed,
Even when piston strokes (strokes of the bound / rebound operation) are different, when the same piston speed is the same, the damping force becomes constant, and it is not possible to achieve both riding comfort and steering stability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a hydraulic pressure configured to improve both ride comfort and steering stability by changing a damping force according to a piston speed and a piston stroke. It is an object to provide a shock absorber.

[0010]

Means for Solving the Problems To solve the above problems, the present invention is characterized by taking the following means. The invention according to claim 1 includes a cylinder filled with liquid, a piston defined in the cylinder as an upper liquid chamber and a lower liquid chamber, and sliding according to a force input to a piston rod. A hydraulic pressure buffer having a valve that generates a damping force by opening or closing a communication hole provided in the piston according to a sliding operation direction of the piston, and a damping force variable mechanism that changes the damping force according to the piston speed. In the apparatus, the damping force variable mechanism is integrally coupled to the piston, and is slidable into the hollow member inserted into a lower liquid chamber of the cylinder formed below the piston and into the hollow member. And a sliding body that slides by a liquid pressure difference between a first liquid chamber and a second liquid chamber formed inside the hollow member, and a first fitting that urges the upper surface of the sliding body downward. The biasing member and the lower surface of the sliding body are urged upward. A second urging member, and a bypass passage provided in the hollow member and opened and closed according to a sliding position of the sliding body. When the piston is in a small stroke, the bypass passage is shut off. And wherein the spring force of the first urging member and the second urging member is applied to the piston rod in accordance with the sliding operation of the sliding body in the state of being performed. is there.

The invention according to claim 2 is provided with an inner cylinder filled with a liquid, a piston that slides in the inner cylinder in response to a force input to a piston rod, and the piston. A valve for generating a damping force by opening or closing the communication hole according to the sliding direction of the piston, an outer cylinder formed coaxially outside the inner cylinder, a bottom portion of the outer cylinder, and the inner cylinder; A base valve mechanism that opens and closes between the base valve mechanism and a damping force variable mechanism that changes the damping force according to the piston speed, wherein the damping force variable mechanism is integrated with the base valve mechanism. And a sliding member slidably inserted into the hollow member and slid by a liquid pressure difference between a first liquid chamber and a second liquid chamber formed inside the hollow member. A first urging member for urging the upper surface of the sliding body downward; A second urging member for urging the lower surface of the sliding body upward, and a bypass passage provided in the hollow member and opened and closed according to a sliding position of the sliding body, wherein an operation state of the piston is When the stroke is small, the spring force of the first urging member and the second urging member is added in accordance with the sliding operation of the sliding body while the bypass passage is shut off. It is characterized by the following.

According to a third aspect of the present invention, a cylinder filled with a liquid, an upper liquid chamber and a lower liquid chamber are defined in the cylinder, and the cylinder slides in response to a force input to a piston rod. A piston, a valve that opens or closes a communication hole provided in the piston according to a sliding operation direction of the piston to generate a damping force, and a damping force variable mechanism that changes the damping force according to a piston speed. In the hydraulic shock absorber having the damping force variable mechanism, the hollow member is integrally connected to the piston rod, and is inserted into an upper liquid chamber of the cylinder formed above the piston; A sliding member which is slidably inserted therein and slides by a liquid pressure difference between a first liquid chamber and a second liquid chamber formed inside the hollow member, and urges the upper surface of the sliding member downward; A first biasing member for A second urging member for urging the lower surface of the sliding member upward, and a bypass passage provided in the hollow member and opened / closed according to a sliding position of the sliding body, wherein the operation state of the piston is a small stroke. When the bypass passage is shut off, the spring force of the first urging member and the second urging member is applied to the piston rod in accordance with the sliding operation of the sliding body. It is characterized by the following.

Each of the above means operates as follows.
According to the first aspect of the present invention, when the operating state of the piston is a small stroke, the first urging member and the second urging member are responsive to the sliding operation of the sliding body with the bypass passage closed. Since the spring force of the member is added to the piston rod, the spring force of the first urging member and the second urging member is added to the piston rod so that even if the damping force is reduced to improve ride comfort, The damping force of the vehicle can be increased, whereby the steering stability can be secured.

Since the first urging member and the second urging member are independent of the damping force characteristics, they can be used with a low load.
Therefore, the durability is very high. For example, even if the piston moves in the extension direction or the compression direction, the sliding body can be slid with good responsiveness according to the stroke of the piston, and the followability of the sliding body to the piston speed can be improved.

According to the second aspect of the present invention, when the operating state of the piston is a small stroke, the hollow provided integrally with the base valve mechanism that opens and closes between the bottom of the outer cylinder and the bottom of the inner cylinder. The spring force of the first urging member and the second urging member is applied to the piston rod in accordance with the sliding operation of the sliding body that slides inside the member, so that the damping force is reduced to improve ride comfort. However, the spring force of the first urging member and the second urging member can be added to increase the apparent damping force, thereby ensuring steering stability.

According to the third aspect of the present invention, when the operating state of the piston is a small stroke, the sliding member slides in the hollow member inserted into the upper liquid chamber of the cylinder formed above the piston. Since the spring force of the first urging member and the second urging member is applied to the piston rod in accordance with the sliding operation, even if the damping force is reduced to improve ride comfort, the first urging member is In addition, the spring force of the second urging member can be added to the piston rod to increase the apparent damping force, thereby ensuring steering stability.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the entire structure of a hydraulic pressure damping device 1 according to one embodiment of the present invention, and FIG. 2 is an enlarged longitudinal sectional view showing a piston 4 and a damping force variable mechanism. In FIG. 1, a front wheel shock absorber used for a suspension mechanism for a vehicle is taken as an example of the hydraulic shock absorber 1.

The hydraulic shock absorber 1 comprises an outer cylinder 2, a cylinder 3 as an inner cylinder, a piston 4, a piston rod 5, a base valve mechanism 10, and the like. The outer cylinder 2 has a cylindrical shape, and a spring receiver 2a that abuts a coil spring (not shown) for supporting the load of the vehicle body is fixed to an outer periphery of the outer cylinder 2. A bracket 2b for supporting wheels is provided on an outer periphery of a lower end of the outer cylinder 2. It is fixed.

A cylindrical cylinder 3 filled with hydraulic fluid (hydraulic oil) having a predetermined viscosity is inserted into the outer cylinder 2. The cylinder 3 has a piston 4
Are slidably inserted in the vertical direction (A ₁ , A ₂ directions) in the figure. A piston rod 5 extending in the axial direction of the cylinder 3 is connected to the piston 4. The piston 4 is provided with a damping force generating mechanism 16 for generating a damping force and a damping force variable mechanism 17 for varying the damping force.
7 will be described later for convenience of explanation.

The interior of the cylinder 3 is defined as an upper liquid chamber 6 and a lower liquid chamber 7 by inserting the piston 4. A lower cap 9 is fixed to a lower end opening 2c of the outer cylinder 2 by welding or the like, and a base valve mechanism 10 is provided at a lower end opening of the cylinder 3. Further, a rod guide 11 is provided at an upper opening of the cylinder 3, and a piston rod 5 penetrates slidably in the center thereof.

The outer diameter of the cylinder 3 is set smaller than the inner diameter of the outer cylinder 2, so that the outer cylinder 2 and the cylinder 3
An annular space (hereinafter, referred to as a reservoir chamber 13) is formed between them. The lower half of the reservoir chamber 13 is filled with hydraulic fluid, and the upper half of the reservoir chamber 13 is filled with a gas of a predetermined pressure (for example, nitrogen gas). The base valve mechanism 10 is a valve mechanism that opens and closes between the lower liquid chamber 7 and the reservoir chamber 13 by sliding the piston 4, and the rod guide 11 communicates between the reservoir chamber 13 and the inside of the cylinder 3. It has a passage 11a.

A ring nut 14 is provided at the upper end opening of the outer cylinder 2 and is screwed to a screw. The ring nut 14 contacts the upper surface of the rod guide 11 and holds the rod guide 11 and the cylinder 3. Further, an oil seal 15 for sealing the outer periphery of the piston rod 5 is interposed between the ring nut 14 and the rod guide 11.

As shown in an enlarged manner in FIG. 2, the piston 4 has a small-diameter portion 5a provided at the lower end of the piston rod 5.
Is fitted and fixed. Specifically, a screw 5b is formed at the lower end of the small diameter portion 5a, and a washer 18, a disc valve 19, a piston body 20, a disc valve 21, a guide collar 22, and a coil spring 23 are formed on the small diameter portion 5a. Then, the variable damping force mechanism 17 is attached to the small diameter portion 5a.

Further, a plurality of grooves are formed on the outer periphery of the piston 4, and an annular seal member 24 is formed in the grooves.
Are arranged. The seal member 24 is configured to be in sliding contact with the inner wall of the cylinder 3 in a liquid-tight manner, so that the piston 4 can slide in the cylinder 3 in a liquid-tight manner. Next, the damping force generating mechanism 16 provided on the piston 4
Will be described.

The damping force generating mechanism 16 is roughly composed of an upper valve mechanism 25 provided above the piston body 20.
And a lower valve mechanism 26 provided below the piston body 20. The upper valve mechanism 25 includes the washer 18 and the disc valve 19, and the lower valve mechanism 26 includes the disc valve 21, the guide collar 22, and the coil spring 23.

In the piston body 20, a central hole 20a through which the small-diameter portion 5a of the piston rod 5 is inserted is axially penetrated at the center thereof, and a first communication passage 27 which penetrates vertically outside the central hole 20a. And a second communication passage 28. In the first communication passage 27, the piston 4 is moved in the compression direction (A
_It functions as a passage in the compression direction through which the hydraulic fluid passes when moved in _one direction), and is opened and closed by the disk valve 19 of the upper valve mechanism 25. Since disk valve 19 is a non-return valve (check valve), when the piston 4 is slid in the compression direction (A ₁ direction), most of the damping force is generated by the base valve mechanism 10.

Further, the second communication passage 28 functions as the elongation direction damping force generator for generating a damping force by passing the working fluid when moving the piston 4 is elongate direction (A ₂ direction),
It is opened and closed by the disc valve 21 of the lower valve mechanism 26. Here, the configuration of the damping force variable mechanism 17 constituting a main part of the present invention will be described.

The variable damping force mechanism 17 includes a piston rod 5
A fixing member 31 screwed to the small diameter portion 5a of the fixing member 3
1, a hollow cylindrical member 32 screwed to the lower part of
Sliding body 3 slidably fitted in internal space 32a of material 32
3 and slide body 33 downward (A ₁First press
The first body (first urging member) 34 and the sliding body 33 upward (A
_Two(Elastic body) 35 (second urging member) that presses in the
And a cap 36 screwed into the lower part of the hollow member 32
It is composed of The variable damping force mechanism 17 and the fixed
Annular fluid chamber 3 filled with hydraulic fluid
7 are formed.

In this embodiment, a configuration using a coil spring as the first elastic body 34 and the second elastic body 35 is given as an example. However, other than this, an elastic body made of rubber or the like may be used. Alternatively, the sliding body 33 may be urged from above and below using an elastic body such as a bellows formed in a bellows shape. The fixing member 31 has a screw hole 31a in the center of the upper end into which the small-diameter portion 5a of the piston rod 5 is screwed and extends in the axial direction, and a spring receiving portion 31b with which the lower end of the coil spring 23 abuts is provided on the outer periphery of the upper end. ing. The fixing member 31 has a central hole 31c penetrating in the axial direction.
And a passage 31d extending in the radial direction so as to communicate the central hole 31c and the intermediate liquid chamber 37.

Further, a female screw 31e for screwing the hollow member 32 is provided on the inner periphery of the lower opening of the fixing member 31, and a first elastic body 34 is provided at the center of the lower opening of the fixing member 31.
A spring receiving recess 31f with which the upper end of the spring contact is provided. Since the center hole 31c is opened in the spring receiving recess 31f, the internal space 32a is communicated with the intermediate liquid chamber 37 via the center hole 31c and the passage 31d.

The hollow member 32 has a fixed member 31
A male screw 32b screwed into a female screw 31e, and a male screw 32 screwed into a female screw 36a of a cap 36 on the lower outer periphery.
c, a sliding portion 3 that slides on the inner wall of the cylinder 3 around the outer periphery of the middle portion.
2d. A plurality of grooves are formed on the outer periphery of the sliding portion 32d, and an annular seal member 38 is provided in the grooves. The seal member 38 is configured to be in sliding contact with the inner wall of the cylinder 3 in a liquid-tight manner.

Further, the intermediate liquid chamber 37 and the internal space 3 of the hollow member 32
A first bypass passage 32e communicating with the second bypass passage 2a;
A second bypass passage 32f that connects the lower liquid chamber 7 and the internal space 32a of the hollow member 32 is provided on the lower outer periphery of the sliding portion 32d of the hollow member 32. The sliding body 33 inserted into the internal space 32a of the hollow member 32 is a piston formed in a disc shape, and a spring receiving recess 33a with which the lower end of the first elastic body 34 contacts is provided on the upper surface side, and on the lower surface side. A spring receiving recess 33b with which the upper end of the second elastic body 35 contacts is provided. Therefore, the sliding body 33 is provided with the first elastic body 34.
The spring force of the are held in the spring force is balanced position of the second elastic member 35, when the piston 4 is the hydraulic pressure in the hydraulic fluid to slide varies, slides in A ₁ direction or A ₂ direction .

The inner space 32a of the hollow member 32 is defined by a sliding body 33 as an upper chamber (first liquid chamber) 39 and a lower chamber (second liquid chamber) 40, and the sliding body 33 slides. At the same time, the volumes of the upper chamber 39 and the lower chamber 40 fluctuate. Hollow member 32
Of the upper chamber 39 and the lower chamber 40
Is zero, the sliding member 33 is maintained at an intermediate position where the spring force of the first elastic member 34 and the spring force of the second elastic member 35 are balanced. Therefore, usually, the sliding body 33
Is held at an intermediate position between the first bypass passage 32e and the second bypass passage 32f.
The sliding body 33 blocks between the first bypass passage 32f and the second bypass passage 32f.

The cap 36 has a female screw 36a screwed to the external thread 32c of the hollow member 32 on the inner periphery of the upper opening.
And a spring receiving recess 36b with which the lower end of the second elastic body 35 abuts is provided at the center of the upper opening. Further, a passage 36c penetrating in the axial direction is opened at the center of the spring receiving recess 36b. As described later, when the hydraulic pressure in the upper chamber 39 increases due to the movement of the piston 4 in the extending direction, the sliding body 33 moves downward (A).
Slide in _one direction). Further, when the liquid pressure in the lower chamber 40 by the movement of the compression direction of the piston 4 rises, correspondingly sliding body 33 slides upwardly (A ₂ direction).

Therefore, when the piston stroke is small, the stroke of the sliding member 33 is also small,
Since the gap between 2e and 32f is blocked, the elastic bodies 34 and 35 expand and contract by the force input to the piston rod 5. Further, when the piston operation is a large stroke, the operation of the sliding body 33 is large, and the upper liquid chamber 6 and the lower liquid chamber 7 are communicated via the bypass passages 32e and 32f.

The variable damping force mechanism 17 includes a piston 4
Independent of the damping force characteristic generated by the stroke of the stroke, the load to be generated can be reduced, whereby the followability of the sliding body 33 to the sliding operation of the piston 4 is improved. It is configured such that the sliding operation can be performed with good responsiveness according to the stroke of the piston 4 regardless of whether it moves in the extension direction or the compression direction. Therefore, the occurrence of cavitation due to the operation delay of the sliding body 33 is prevented.

The first elastic body 34 and the second elastic body 3
5 is advantageous in terms of durability because the pressure difference between the upper chamber 39 and the lower chamber 40 acting on the sliding body 33 is relatively small, and the load on the spring is small. Next, the operation of the variable damping force mechanism 17 configured as described above will be described with reference to FIG. FIG. 3 is a longitudinal sectional view showing a compression operation and an extension operation at the time of a small stroke. The left half in FIG. 3 shows a compression operation, and the right half in FIG. 3 shows an extension operation.

When the bound / rebound operation of the wheel is transmitted to the piston rod 5, the hydraulic shock absorber 1 performs a compression operation or an extension operation. When the piston 4 slides in A ₁ direction by the compression operation the hydraulic shock absorber 1, the damping force varying mechanism integrally provided in the lower portion of the piston 4 17 also slides in the same direction. Therefore, the pressure P ₁ of the upper liquid chamber 6 and the pressure of the intermediate liquid chamber 3
7 and the pressure P ₂ of the pressure P of the upper chamber 39 of the hollow member 32
_3, the pressure P ₄ of the lower chamber 40 of the hollow member 32, the pressure P ₅ in the lower liquid chamber 7 becomes _{P 1 <P 2 <P 3} <P 4 <P 5.

[0039] Thus, when the piston 4 is sliding with a small stroke A ₁ direction, by the pressure difference (P ₁ <P ₂₎ of the upper liquid chamber 6 and the intermediate liquid chamber 37 is a disk valve 19 of the upper valve mechanisms 25 The valve opening operation causes the working fluid in the intermediate fluid chamber 37 to flow into the upper fluid chamber 6 through the first communication passage 27 of the piston 4. Since the hydraulic fluid is made of viscous oil, a differential pressure is generated when the hydraulic fluid passes through the first communication passage 27.

Here, the small stroke refers to the sliding member 3
3 is the first bypass passage 32e or the second bypass passage 32
f (a predetermined range determined by the axial separation distance between the first bypass passage 32e and the second bypass passage 32f).
3 is the first bypass passage 32e or the second bypass passage 32
If the slider slides so as to pass f, the stroke becomes a large stroke exceeding a predetermined range.

The first bypass passage 32e is closed by a small stroke of the sliding member 33, and the intermediate liquid chamber 37 and the upper chamber 39 of the hollow member 32 communicate with the central hole 31c of the fixed member 31 and the passage 31d. intermediate liquid through the central hole 31c and the passage 31d of the hydraulic fluid fixing member 31 of the upper chamber 39 if it is communicated, the pressure difference between the upper chamber 39 and the intermediate liquid chamber 37 (P ₃ -P ₂₎ through It is supplied to the chamber 37. A differential pressure is also generated when the hydraulic fluid passes through the central hole 31c and the passage 31d. The hydraulic fluid in the lower liquid chamber 7 flows into the lower chamber 40 from the passage 36c of the cap 36, and the hydraulic fluid in the lower chamber 40 returns to the lower liquid chamber 7 through the second bypass passage 32f.

[0042] At this time, sliding body 33 which is inserted into the inner space 32a of the hollow member 32 slides in the A ₂ direction by the differential pressure between the lower chamber 40 and upper chamber 39 (P ₄ -P _3). At this time, since the hydraulic fluid is an incompressible fluid, the sliding body 33 is interlocked with the movement of the piston 4, and the stroke of the sliding body 33 is the flow rate of the hydraulic fluid moving with the sliding operation of the piston 4. Depends on

As described above, even when the sliding body 33 slides with a small stroke, the first bypass passage 32e and the second bypass passage 32 are formed in the same manner as when the sliding body 33 is at the intermediate position.
Since the gap between f and f is blocked by the sliding body 33, the hydraulic fluid in the lower liquid chamber 7 and the lower chamber 40 does not move to the intermediate liquid chamber 37 and the upper liquid chamber 6. Further, when the sliding body 33 slides in the A ₂ direction, the first elastic body 34 is compressed, the second elastic member 35
Since extends, the spring force of the second elastic member 35 F ₂ decreases with the spring force F ₁ of the first elastic body 34 is increased. The sliding body 33 is positioned at a position where the hydraulic pressure acting on the upper and lower surfaces (area A) and the spring force are balanced (F ₁ + P ₃ .A = F ₂ + P _4.
A position).

[0044] In this way, when the piston 4 is sliding with a small stroke A ₁ direction, the force generated by the damping force control mechanism 17 is small. Then, the piston 4 operates the hydraulic shock absorber 1 extends a description will be given of the operation in the case of small strokes slides in A ₂ direction. When the piston 4 slides with a small stroke A ₂ direction, to slide in the same direction the damping force varying mechanism 17, the pressure P ₁ of the upper liquid chamber 6, the pressure P ₂ of the intermediate liquid chamber 37, the hollow the pressure P ₃ of the upper chamber 39 of the member 32, and the pressure P ₄ of the lower chamber 40 of the hollow member 32, the pressure P ₅ in the lower liquid chamber 7, a _{P 1> P 2> P 3} > P 4> P 5 Become.

[0045] Thus, when the piston 4 is sliding with a small stroke A ₂ direction, the disc valve 21 of the lower valve mechanism 26 by the pressure difference between the upper liquid chamber 6 and the intermediate liquid chamber 37 (P ₁ -P ₂₎ When the valve opens, the hydraulic fluid in the upper fluid chamber 6 flows through the second communication passage 28 of the piston 4 and the disc valve 21 to flow into the intermediate fluid chamber 37, and a damping force is generated. And
Due to the pressure difference (P ₂ −P ₃ ) between the intermediate liquid chamber 37 and the upper chamber 39, the hydraulic fluid in the intermediate liquid chamber 37 is supplied to the upper chamber 39 via the passage 31 d of the fixing member 31 and the central hole 31 c. that time,
The sliding body 33 is provided with a differential pressure (P ₃ −P) between the upper chamber 39 and the lower chamber 40.
₄₎ slides in the A ₁ direction. At this time, the sliding body 33
Therefore, the second bypass passage 32 f is closed by the sliding body 33. Therefore, lower room 40
As for the hydraulic fluid, the flow rate corresponding to the volume of sliding of the sliding body 33 flows into the lower liquid chamber 7, and the hydraulic fluid corresponding to the volume change in the lower liquid chamber 7 is supplied.

[0046] Further, the sliding body 33 slides in the A ₁ direction, extends first elastic member 34, since the second elastic member 35 is compressed, the spring force F ₁ of the first elastic body 34 is reduced the spring force of the second elastic member 35 F ₂ increases with. Then, the sliding body 33 reaches a position where the hydraulic pressure acting on the upper and lower surfaces (area A) and the spring force are balanced (a position where F ₁ + P ₃ · A = F ₂ + P ₄ · A).

[0047] When such a piston 4 is slidably small stroke A ₂ direction, the force generated by the damping force control mechanism 17 is small. Therefore, even if the damping force due to the sliding of the piston 4 is reduced to improve the riding comfort, the piston 4
Slides, the spring force is increased by the expansion and contraction of the elastic bodies 34 and 35 by the damping force variable mechanism 17, and the apparent damping force is increased by the addition of the spring force to the piston rod 5, so that the steering stability is improved. Go up.

Next, the compression operation and the expansion operation during a large stroke will be described with reference to FIG. FIG. 4 is a longitudinal sectional view showing a compression operation and an expansion operation at the time of a large stroke. The left half in FIG. 4 shows the compression operation, and the right half in FIG. 4 shows the expansion operation. If the hydraulic shock absorber 1 is the piston 4 to compress operation is slid in a large stroke in the A ₁ direction, the damping force varying mechanism 17
Also move the same stroke in the same direction. Accordingly, the piston 4 slides in large strokes A ₁ direction, the intermediate liquid chamber 3
The disc valve 19 of the upper valve mechanism 25 opens due to the pressure difference (P ₂ −P ₁ ) between the pressure chamber 7 and the upper liquid chamber 6.
The working fluid in the intermediate fluid chamber 37 passes through the first communication passage 27 and flows into the upper fluid chamber 6. In this case, most of the damping force is generated in the base valve mechanism 10.

The pressure difference between the lower chamber 40 and the upper chamber 39 (P_Four
−P_Three), The sliding body 33 is A_TwoSliding in the same direction
Then, the hydraulic fluid in the upper chamber 39 flows through the central hole 31c of the fixing member 31.
The liquid is supplied to the intermediate liquid chamber 37 through the passage 31d. Further
In addition, the sliding body 33 is provided with a pressure difference between the lower chamber 40 and the upper chamber 39 (P_Four
−P_Three) By A _TwoIf you slide a large distance in the
After passing through the path passage 32e and from the first bypass passage 32e
Slide upwards. Therefore, the first bypass passage 32e and
The lower chamber 40 communicates with the lower chamber 40, and the hydraulic fluid in the lower chamber 7 is
And flows into the intermediate liquid chamber 37 through the first bypass passage 32e.
Then, the working fluid in the intermediate fluid chamber 37 is supplied to the first communication passage 2 of the piston 4.
7 and is supplied to the upper liquid chamber 6.

Therefore, until the first bypass passage 32e and the lower chamber 40 communicate with each other by the sliding of the sliding body 33, the spring force of the elastic body 34 increases and the apparent damping force increases. Thus when the piston 4 is sliding with a large stroke in the A ₁ direction, it is possible to generate a larger damping force than when a small stroke described above. Therefore, for example, when changing lanes (lane change) or cornering, even if the piston speed of the piston 4 is the same as when the stroke is small, the damping force increases with an increase in the stroke of the piston 4 to enhance the steering stability. be able to.

Next, the piston 4 operates the hydraulic shock absorber 1 extends a description will be given of the operation in the case where the slide in a large stroke in the A ₂ direction. When the piston 4 operates the hydraulic shock absorber 1 extends slides a large stroke A ₂ direction, the differential pressure between the upper fluid chamber 6 and the intermediate liquid chamber 37 (P ₁ -P ₂₎ of the lower valve mechanism 26 Since the disc valve 21 performs the valve opening operation, the hydraulic fluid in the upper fluid chamber 6 flows into the intermediate fluid chamber 37 through the second communication passage 28 and generates a damping force. Further, the sliding body 33 slides in the A ₁ direction by the differential pressure between the upper chamber 39 and lower chamber 40 (P ₃ -P _4), the hydraulic fluid in the lower chamber 40 through the passage 36c of the cap 36 Lower liquid chamber 7
Spilled to.

Further, the sliding body 33 includes an upper chamber 39 and a lower chamber 4.
Differential pressure from 0 (P_Three−P_Four) By A _TwoLarge sliding in the direction
Then, through the second bypass passage 32f, the second bypass
Slides below the passage 32f. Therefore, the second buy
The path passage 32 f and the upper chamber 39 communicate with each other,
The hydraulic fluid passes through the passage 31d and the central hole 31c of the fixed member 31.
When flowing into the upper chamber 39 via the first bypass passage 32e
In both cases, the hydraulic fluid in the upper chamber 39 passes through the second bypass passage 32f.
Then, it is supplied to the lower liquid chamber 7.

Accordingly, the spring force of the elastic body 35 increases and the apparent damping force increases until the second bypass passage 32f and the upper chamber 39 communicate with each other by sliding of the sliding body 33. When such a piston 4 is slidably large stroke A ₂ direction, hydraulic fluid second communication passage 28 of the upper liquid chamber 6, the intermediate liquid chamber 37, the first bypass passage 32e, the upper chamber of the hollow member 32 39, by moving to the lower liquid chamber 7 through the second bypass passage 32f, the piston speed is increased, so that a larger damping force can be generated as compared with a small stroke. Therefore, when changing lanes (lane change), cornering, or the like, even if the piston speed of the piston 4 is the same as that of a small stroke, the damping force increases with the increase in the stroke of the piston 4 to improve steering stability. Can be.

When the stroke of the piston 4 is maximized, the first bypass passage 32e and the lower chamber 40 or the second bypass passage 32f and the upper chamber 39 are in communication with each other. The power is saturated, and the occurrence of the tilt of the vehicle can be prevented. FIG. 5 shows a damping force variable mechanism 1.
7 is a graph showing characteristics of a spring force of No. 7 and a stroke of a piston 4.

In the graph shown in FIG. 5, since the inclination is determined by the spring constant, the first elastic body 34 and the second elastic body 3
By setting the spring constant of 5 to an arbitrary value, a change in the damping force with respect to the stroke of the piston 4 can be selected. When the stroke of the piston 4 is within the range of the small stroke (the inflection points a ₁ and a ₂ ), the stroke becomes large even if the damping force generated by the piston 4 is reduced in order to improve the riding comfort. , Elastic body 34,
As the spring force of 35 increases and the apparent damping force applied to the piston rod 5 increases, the steering stability improves.

When the stroke of the piston 4 is large (out of the range of the inflection points a ₁ and a ₂ ), the sliding body 33 passes through the first bypass passage 32 e and the second bypass passage 32 f and the upper liquid chamber 6. And the lower liquid chamber 7 are in communication with each other, and the spring force of the elastic bodies 34 and 35 is saturated. for that reason,
When the piston 4 reaches a maximum, the spring force of the elastic bodies 34 and 35 becomes constant.

Normally, when the coil spring constant for supporting the vehicle increases, tilting tends to occur. In the present embodiment, the upper liquid chamber 6 and the lower liquid chamber 7 are communicated with each other by the sliding operation of the sliding body 33. The spring force of the first elastic body 34 and the second elastic body 35 becomes saturated, and when the stroke is longer than a certain value, the apparent spring constant is reduced.

Further, the variable damping force mechanism 17 can have a compact structure housed in the cylinder 3 and
For example, the spring constants of the first elastic body 34 and the second elastic body 35, the total lengths of the first elastic body 34 and the second elastic body 35, and the positions and intervals of the first bypass passage 32e and the second bypass passage 32f are arbitrarily changed. By doing so, the inflection points a ₁ and a ₂ or b ₁ and b ₂ can be moved, so that the characteristics shown in FIG. 5 can be easily changed, and the running characteristics of the vehicle can be tuned freely. Can be.

Further, since the damping force variable mechanism 17 can be set independently of the damping force characteristics due to the sliding operation of the piston 4, the load can be set relatively small, and the inflection points a ₁ and a ₂ can be set.
The shock when passing through is reduced. FIG. 6 is a longitudinal sectional view of Modification Example 1 of the present invention. This modified example 1
This is a configuration in which a damping force variable mechanism 44 for changing the damping force is attached to the base valve mechanism 10. And, by attaching the damping force variable mechanism 44 to the base valve mechanism 10, it becomes possible to house the cylinder 3 compactly at the bottom of the cylinder 3, and it is possible to cope with downsizing of the hydraulic pressure absorber.

The base valve mechanism 10 comprises an upper valve mechanism 46 provided above a base 45 fitted and fixed to the lower end of the cylinder 3 and a lower valve mechanism 47 provided below the base 45. The upper valve mechanism 46 includes a disk valve 49 that opens and closes the first communication path 48 and a coil spring 50 that presses the disk valve 49 in the valve closing direction. The lower valve mechanism 47 includes a disc valve 52 that opens and closes the second communication path 51 and a pressing plate 53 that presses the disc valve 52 in a valve closing direction.

The bottom chamber 54 formed at the lower part of the base 45 is communicated with an annular reservoir chamber 13 formed between the outer cylinder 2 and the cylinder 3. Therefore, piston 4
Slides, and of the working fluid in the lower fluid chamber 7 or the reservoir chamber 13, the working fluid corresponding to the moved volume of the piston rod 5 passes through the first communication passage 48 or the second communication passage 51, and then flows into the reservoir chamber. 13 or into the lower liquid chamber 7.

Next, the configuration of the damping force variable mechanism 44 of the first modification will be described. The damping force variable mechanism 44 includes a base 45
A hollow member 55 mounted and fixed on top of
Sliding body 56 slidably fitted in internal space 55a of
When, a first elastic member 57 for pressing the slider 56 downward (A ₁ direction), and the second elastic member 58 for pressing the slider 56 upward (A ₂ direction), screwed into the upper portion of the hollow member 55 And a cap 59 to be formed.

The inner space 55a of the hollow member 55 is defined by an upper chamber 65 and a lower chamber 66 by a sliding body 56. The sliding body 56 slides and the volumes of the upper chamber 65 and the lower chamber 66 fluctuate. I do. The hollow member 55 has a lower liquid chamber 7 on the outer periphery.
A seal member 60 for sealing between the inner wall and the inner wall is mounted. As the seal member 60, for example, an O-ring or the like is used.

The outer periphery of the hollow member 55 has a first bypass passage 55 b located above the seal member 60.
And a second bypass passage 55c located below the seal member 60. At the bottom of the hollow member 55, there is provided a bottom passage 62 that communicates an intermediate liquid chamber 61 formed between the outer periphery of the hollow member 55 and the inner wall of the cylinder 3 and a lower chamber 66 of the hollow member 55. I have. The bottom passage 62 is a passage for sucking and discharging the hydraulic fluid to and from the lower chamber 66.

The cap 59 is provided with a passage 59 a penetrating the lower liquid chamber 7 and the internal space 55 a of the hollow member 55. The passage 59 a is a passage for sucking and discharging the hydraulic fluid to and from the upper chamber 65. Further, at the bottom of the hollow member 55, a male screw 63 inserted into the central hole 45a of the base 45 projects downward.
A nut 64 is screwed into the base 3 and fixed to the base 45.

Next, the operation of the variable damping force mechanism 44 configured as described above will be described with reference to FIG. FIG. 7 is a vertical cross-sectional view showing a compression operation and an extension operation at the time of a small stroke of Modification 1, and the left half in FIG. 7 shows a compression operation.
The right half in FIG. 7 shows the extension operation. When the piston 4 slides in A ₁ direction by the compression operation, the pressure in the lower fluid chamber 7 increases. Therefore, the sliding member 56 by the differential pressure between the upper chamber 65 and lower chamber 66 the pressure in the upper chamber 65 of the hollow member 55 rises and slides in the A ₁ direction. When the stroke of the piston 4 is small, the stroke of the sliding body 56 is also small.
The connection between the bypass passage 55b and the second bypass passage 55c is shut off.

Therefore, when the piston 4₁Small straw in the direction
When the sliding occurs, the sliding body 56 ₁Slide in the direction
The capacity of the chamber 65 is increased so that the hydraulic fluid in the lower liquid chamber 7 is supplied to the upper chamber 6.
5 At this time, the first elastic body 57 expands and the second
The elastic body 58 is compressed, and the elastic bodies 57 and 58 expand and contract.
Of hydraulic fluid due to small stroke sliding of piston 4
Changes are absorbed.

[0068] Also, when the piston 4 is slid in the A ₂ direction, the pressure in the lower fluid chamber 7 decreases. Therefore, the sliding member 56 by the differential pressure between the upper chamber 65 and lower chamber 66 the pressure in the upper chamber 65 of the hollow member 55 is lowered to slide the A ₂ direction. When the stroke of the piston 4 is small, the sliding member 5
6 is a first bypass passage 55b and a second bypass passage 55c.
Is shut off between

Therefore, when the piston 4 is_TwoSmall straw in the direction
When the sliding occurs, the sliding body 56 _TwoSlide in the direction
The volume of the chamber 65 is reduced and the hydraulic fluid in the upper chamber 65 is
Drain into 7. At that time, the first elastic body 57 is compressed.
Since the second elastic body 58 extends, the elastic bodies 57 and 58 expand and contract.
Hydraulic fluid caused by small stroke sliding of piston 4 by operation
Pressure change is absorbed.

Therefore, even if the damping force is reduced in order to improve the ride comfort, when the piston 4 strokes, the spring force is increased by the expansion and contraction of the elastic bodies 57 and 58 by the damping force variable mechanism 44, and the apparent damping force is reduced. Increases steering stability. Next, a compression operation at the time of a large stroke of the first modification,
The extension operation will be described with reference to FIG. FIG. 8 is a vertical cross-sectional view showing a compression operation and an extension operation at the time of a large stroke of the first modification. The left half in FIG. 8 shows the compression operation, and the right half in FIG. 8 shows the extension operation.

[0071] The piston 4 may slid large stroke A ₁ direction, the sliding body 56 by the pressure difference between the upper chamber 65 and lower chamber 66 of the hollow member 55 is largely slides in the A ₁ direction. Then, the sliding body 56 passes through the second bypass passage 55c to communicate the second bypass passage 55c with the upper chamber 65. Accordingly, the piston 4 when sliding a large stroke A ₁ direction, the sliding body 56 also communicating the upper chamber 65 and the second bypass passage 55c by increasing slides in A ₁ direction. Therefore, the working fluid in the lower fluid chamber 7 is supplied to the passage 59 a and the first bypass passage 55 b of the cap 59, the upper chamber 65, and the second bypass passage 5.
5c, flows into the intermediate liquid chamber 61.

Thus, the intermediate liquid chamber 61 and the reservoir chamber 1
The pressure difference between the disk valve 52 and the base 45 increases.
Opens the valve. Therefore, the working fluid in the intermediate fluid chamber 61 passes through the second communication passage 51, flows into the bottom chamber 54 formed below the base 45, and is then supplied to the reservoir chamber 13. Therefore, until the upper chamber 65 and the second bypass passage 55c communicate with each other by sliding of the sliding body 56, the spring force of the elastic body 58 increases and the apparent damping force increases.

Further, when the piston 4_TwoLarge straw in the direction
When sliding, the upper chamber 65 and the lower chamber 66 of the hollow member 55
Of the sliding body 56 due to the differential pressure_TwoSliding greatly in the direction.
Then, the sliding body 56 passes through the first bypass passage 55b.
Thus, the first bypass passage 55b communicates with the lower chamber 66.
Therefore, the piston 4 is A_TwoSliding a large stroke in the direction
In this case, the sliding body 56 is also A _TwoSlide in the direction of the lower chamber 66
And the first bypass passage 55b. This
As a result, the pressure of the intermediate liquid chamber 61 decreases and the
Disc valve of base 45 by differential pressure with
49 performs the valve opening operation. Therefore, the operation of the reservoir chamber 13
The liquid is supplied to the intermediate liquid chamber 61 through the second communication path 48
Is done. Further, the working fluid in the intermediate fluid chamber 61 is supplied to the bottom passage 6.
2, lower chamber 66, first bypass passage 55b
The liquid flows into the liquid chamber 7.

Accordingly, the sliding of the sliding body 56 causes the lower chamber 66 to slide.
Until the communication between the first bypass passage 55b and the first bypass passage 55b, the spring force of the elastic body 57 increases and the apparent damping force increases. As described above, when the piston 4 slides greatly, a larger damping force can be generated.
In the case of lane change (lane change), cornering, or the like, even if the piston speed of the piston 4 is the same as that of a small stroke, the damping force increases as the stroke of the piston 4 increases, and steering stability can be improved. .

Further, when the stroke of the piston 4 is maximized, the upper chamber 65 and the second bypass passage 55c communicate with each other, or the lower chamber 66 and the first bypass passage 55b communicate with each other. Since the spring forces of 57 and 58 become saturated, it is possible to prevent the occurrence of the tilt of the vehicle. FIG. 9 is a longitudinal sectional view showing the entire configuration of a hydraulic pressure damper 71 to which Modification 2 is applied, and FIG. 10 is an enlarged longitudinal sectional view showing the piston 4 and damping force variable mechanism 79 of Modification 2. It is.

FIG. 9 shows an example of a shock absorber for a rear wheel used in a suspension mechanism for a vehicle as the hydraulic pressure damping device 71. The hydraulic pressure damping device 71 is roughly composed of an outer cylinder 72, a cylinder 73 as an inner cylinder, and a piston 7
4, a piston rod 75, a base valve mechanism 76, an upper cap 77, and the like. The outer cylinder 72 has a cylindrical shape, and a spring receiver 72a for abutting a coil spring (not shown) for supporting the load of the vehicle body is fixed to an upper outer periphery thereof, and a connecting portion 7 for supporting wheels is provided at a lower end of the outer cylinder 72.
2b is fitted and fixed.

A cylindrical cylinder 73 filled with hydraulic fluid (hydraulic oil) having a predetermined viscosity is inserted into the outer cylinder 72. A piston 74 is inserted into the cylinder 73 so as to be slidable in the vertical direction (A ₁ , A ₂ directions) in the figure. This piston 74 has a cylinder 7
3 are connected to a piston rod 75 extending in the longitudinal direction.

The piston 74 is provided with a damping force generating mechanism 78 for generating a damping force and a damping force variable mechanism 79 for changing the damping force. The damping force variable mechanism 79 is locked while being inserted through a piston rod 75 extending above the piston 74. And the damping force variable mechanism 7
9 can be compactly accommodated in the upper part of the piston 74 by being attached to the piston rod 75, so that the apparatus can be downsized.

Further, the piston 74 and the damping force variable mechanism 79
An intermediate liquid chamber 88 is formed between the two. The intermediate liquid chamber 88 serves as a flow path through which the working liquid flowing according to the stroke of the piston 74 passes. The inside of the cylinder 73 is defined by an upper liquid chamber 80 and a lower liquid chamber 81 by inserting a piston 74. Also, at the bottom of the outer cylinder 72,
A free piston 82 is slidably fitted therein, and a lower chamber 83 below the free piston 82 is filled with high-pressure gas. The upper chamber 8 above the free piston 82
4 is filled with a working fluid. Free piston 82
Absorbs the vibration input to the piston rod 75 by sliding due to the pressure difference between the lower chamber 83 and the upper chamber 84 generated when the piston 74 slides.

An upper cap 77 is fitted and fixed to the upper ends of the outer cylinder 72 and the cylinder 73.
The reservoir chamber 85 formed between the inner circumference of the cylinder and the outer circumference of the cylinder 73 is communicated via a passage 77 a formed in the upper cap 77. The damping force generating mechanism 78 generally includes an upper valve mechanism 95 provided above the piston body 90 and a lower valve mechanism 96 provided below the piston body 90. The upper valve mechanism 95 includes the spring receiver 98, the coil spring 99, and the guide collar 10.
0, a disc valve 101, and a lower valve mechanism 9
Reference numeral 6 includes a disc valve 102, a guide collar 103, a coil spring 104, and a spring receiver 105. Spring support 10
5 is screwed and fixed to the small diameter portion 75a of the piston rod 75.

The piston body 90 has a central hole 90 through which the small diameter portion 75a of the piston rod 75 is inserted.
a is penetrated in the axial direction, and a first communication path 107 and a second communication path 108 are provided outside the center hole 90a in the radial direction. First communication passage 107 serves as a compression direction damping force generator for generating a damping force by passing the working fluid when the piston 74 moves in the compression direction (A ₁ direction), the disc valve 101 of the upper valve mechanisms 95 It is opened and closed by. Further, second communication passage 108 functions as the elongation direction damping force generator for generating a damping force by passing the working fluid when the piston 74 is moved in the extending direction (A ₂ direction), the lower valve mechanism 96 disk It is opened and closed by a valve 102.

Next, the configuration of the damping force variable mechanism 79 of the second modification will be described. The damping force variable mechanism 79 includes a hollow member 115 inserted through the piston rod 75 and a hollow member 11.
Sliding body 1 slidably fitted in the internal space 115a
16, a first elastic member 117 for pressing the sliding body 116 downward (A ₁ direction), and the second elastic body 118 for pressing the slide 116 upward (A ₂ direction), the piston rod 75 of the hollow member 115 And an engaging portion 119 which is engaged with the outer peripheral groove 75b.

The inner space 115a of the hollow member 115 is defined by a sliding body 116 into an upper chamber 125 and a lower chamber 126. The sliding body 116 slides and the volumes of the upper chamber 125 and the lower chamber 126 fluctuate. I do. Also, the hollow member 115
A seal member 120 for sealing between the outer periphery and the inner wall of the cylinder 73 is mounted on the outer periphery. The seal member 120
For example, an O-ring or a piston band is used.

The first bypass passage 11 located above the seal member 120 is provided on the outer periphery of the hollow member 115.
5b, and a second bypass passage 115c located below the seal member 120. At the upper end of the hollow member 115, a passage 115d communicating the upper liquid chamber 80 and the upper chamber 125 is provided, and at the lower end of the hollow member 115, a passage 115e communicating the intermediate liquid chamber 88 and the lower chamber 125 is provided. Have been.

Next, the operation of the variable damping force mechanism 79 configured as described above will be described with reference to FIG. still,
FIG. 11 is a vertical cross-sectional view showing a compression operation and an extension operation at the time of a small stroke in Modification Example 2. The left half in FIG. 11 shows the compression operation, and the right half in FIG. 11 shows the extension operation. When the piston 74 is slid in the A ₁ direction by the compression operation, the lower liquid chamber 8
1 increases. Therefore, the disc valve 101 of the upper valve mechanism 95 performs the valve opening operation, and the hydraulic fluid in the lower fluid chamber 81 flows into the intermediate fluid chamber 88 through the first communication passage 107.

The working fluid in the intermediate fluid chamber 88 is supplied to the passage 1
Since the gas flows into the lower chamber 126 of the hollow member 115 from 15e, the pressure of the lower chamber 126 increases. Thus, the sliding member 116 differential pressure between the upper chamber 125 and lower chamber 126 of the hollow member 115 is caused to slide in the A ₂ direction. When the stroke of the piston 74 is small, the stroke of the sliding body 116 is also small, and the connection between the first bypass passage 115b and the second bypass passage 115c is shut off.

[0087] Thus, when the piston 74 has a small stroke slide in A ₁ direction, passage hydraulic fluid of the intermediate liquid chamber 88 increases the volume of the lower chamber 126 sliding body 116 is slid in the A ₂ direction 115e To the lower chamber 126. that time,
Since the first elastic body 117 is compressed and the second elastic body 118 is expanded, the pressure change of the working fluid caused by the small stroke of the piston 74 is absorbed by the expansion and contraction of the elastic bodies 117 and 118. Therefore, the spring force of the elastic body 117 according to the sliding of the piston 74 is applied to the piston rod 75.

[0088] Further, the piston 74 when slid in the A ₂ direction, the pressure in the upper fluid chamber 80 is increased. Therefore, the working fluid in the upper liquid chamber 80 flows into the upper chamber 125 of the hollow member 115 from the passage 115d and the first bypass passage 115b.
Thereby, the upper chamber 125 and the lower chamber 126 of the hollow member 115 are formed.
Sliding body 116 difference occurs between pressure between the slides in the A ₁ direction.

At the same time, the hydraulic fluid in the lower chamber 126 is
After passing through 5e, it flows into the intermediate liquid chamber 88. Therefore, the disc valve 102 of the lower valve mechanism 96 performs the valve opening operation, and the hydraulic fluid in the intermediate fluid chamber 88 flows into the lower fluid chamber 81 through the second communication passage 108. When the stroke of the piston 74 is small, the sliding body 116 blocks between the first bypass passage 115b and the second bypass passage 115c. Thus, when the piston 74 has a small stroke sliding on A ₂ direction, discharging the working fluid in the lower chamber 126 to reduce the volume of the lower chamber 126 sliding body 116 is slid in the A ₁ direction to the intermediate liquid chamber 88 Let it.

At this time, since the first elastic body 117 is expanded and the second elastic body 118 is compressed, the pressure change of the working fluid caused by the small stroke of the piston 74 is reduced.
It is absorbed by the expansion and contraction operation of 118. Therefore, the spring force of the elastic body 118 according to the sliding of the piston 74 is applied to the piston rod 75. Therefore, even if the damping force due to the sliding of the piston 74 is reduced in order to improve the riding comfort, when the damping force variable mechanism 79 slides with the piston 74, the spring force increases due to the expansion and contraction of the elastic bodies 117 and 118, and the apparent force is increased. The damping force of the vehicle increases, and steering stability increases.

Next, the compression operation and the expansion operation at the time of a large stroke of the second modification will be described with reference to FIG. FIG.
FIG. 12 is a vertical cross-sectional view showing a compression operation and an expansion operation at the time of a large stroke of Modification Example 1, and a left half in FIG. 12 shows a compression operation;
The right half in FIG. 12 shows the extension operation. Piston 74 is A ₁
When sliding in the direction by a large stroke, the pressure of the lower liquid chamber 81 increases. The differential pressure between the lower liquid chamber 81 and the intermediate liquid chamber 88 causes the disc valve 101 of the upper valve mechanism 95 to move.
Is operated to open the first communication passage 1
07 and flows into the intermediate liquid chamber 88.

The working fluid in the intermediate fluid chamber 88 is supplied to the passage 1
Since the gas flows into the lower chamber 126 of the hollow member 115 from 15e, the pressure of the lower chamber 126 increases. Thus, the sliding member 116 differential pressure between the upper chamber 125 and lower chamber 126 of the hollow member 115 is caused to slide in the A ₂ direction. In this case, since the stroke of the piston 74 is large, the sliding body 116 also slides greatly, passes through the first bypass passage 115b, and
The bypass passage 115b communicates with the second bypass passage 115c.

[0093] Thus, when the piston 74 has a large stroke slide in A ₁ direction, since the sliding member 116 communicates the the lower chamber 126 the first bypass passage 115b by increasing slides in A ₂ direction, the lower liquid chamber 81 is supplied to the first communication passage 1
07, the intermediate liquid chamber 88, the passage 115e, the lower chamber 126, the first
The liquid flows into the bypass passage 115 b and the upper liquid chamber 80. Therefore, until the lower chamber 126 and the first bypass passage 115b communicate with each other by sliding of the sliding body 116, the spring force of the elastic body 117 increases and the apparent damping force increases.

[0094] Further, the piston 74 may have a large stroke sliding on A ₂ direction, the hydraulic fluid in the upper fluid chamber 80 the pressure in the upper fluid chamber 80 is increased to flow from the passage 115d in the upper chamber 125 of the hollow member 115 . As a result, a pressure difference is generated between the upper chamber 125 and the lower chamber 126 of the hollow member 115, and the sliding member 1
16 large stroke slide in A ₁ direction. Sliding body 116
Slides greatly, passes through the second bypass passage 115c, and passes through the first bypass passage 115b and the second bypass passage 115c.
And communicate.

[0095] Thus, when the piston 74 has a large stroke sliding on A ₂ direction, the hydraulic fluid in the upper fluid chamber 80 a passage 11
5d, flows into the upper chamber 125, the second bypass passage 115c, and the intermediate liquid chamber 88. Then, the intermediate liquid chamber 88 and the lower liquid chamber 8
The disc valve 102 of the lower valve mechanism 96 is opened by the pressure difference with the pressure of 1, and the hydraulic fluid in the intermediate fluid chamber 88 flows into the lower fluid chamber 81 through the second communication passage 108.

Therefore, the sliding of the sliding body 116 causes the upper chamber 1 to slide.
Until the connection between the second bypass passage 155c and the second bypass passage 155c, the spring force of the elastic body 118 increases and the apparent damping force increases. In this manner, when the piston 74 slides greatly, a larger damping force can be generated, so that when the lane is changed (lane change) or cornering is performed, the piston speed of the piston 74 is the same as that when the stroke is small. However, as the stroke of the piston 74 increases, the damping force increases and the steering stability can be improved.

Further, when the stroke of the piston 74 is maximized, the upper chamber 125 and the second bypass passage 115c communicate with each other, or the lower chamber 126 and the first bypass passage 115b
Are in communication with each other, so that the elastic bodies 117, 118
The spring force becomes saturated and the apparent spring constant decreases, so that the occurrence of the tilt of the vehicle can be prevented. In each of the above-described embodiments, the hydraulic shock absorber used for the suspension of the automobile is described as an example. However, the present invention is not limited to this, and may be applied to a hydraulic shock absorber used for vehicles other than the automobile. Of course.

[0098]

According to the present invention as described above, the following various effects can be realized. According to the first aspect of the present invention, when the operating state of the piston is a small stroke, the first urging member and the second urging member are responsive to the sliding operation of the sliding body with the bypass passage closed. Since the spring force of the member is added to the piston rod, the spring force of the first urging member and the second urging member is added to the piston rod so that even if the damping force is reduced to improve ride comfort, The damping force of the vehicle can be increased, whereby the steering stability can be secured.

Further, when the operating state of the piston is a large stroke, the sliding member slides greatly and the bypass passage is communicated, so that the spring force is increased and the steering stability is increased. The spring force of the urging member and the second urging member is saturated, and tilting can be prevented. Also, the first
Since the urging member and the second urging member are independent of the damping force characteristics of the piston, the applied force can be small, and the followability of the sliding body to the sliding operation of the piston is improved. For example, even if the piston moves in the extension direction or the compression direction, the sliding body can slide with good response according to the stroke of the piston, and cavitation of the hydraulic fluid can be prevented.

According to the second aspect of the present invention, when the operating state of the piston is a small stroke, the hollow provided integrally with the base valve mechanism that opens and closes between the bottom of the outer cylinder and the bottom of the inner cylinder. The spring force of the first urging member and the second urging member is applied to the piston rod in accordance with the sliding operation of the sliding body that slides inside the member, so that the damping force is reduced to improve ride comfort. However, the spring force of the first urging member and the second urging member can be added to increase the apparent damping force, thereby ensuring steering stability.

Further, by attaching the variable damping force mechanism to the base valve mechanism, it is possible to store the variable damping force mechanism compactly at the bottom of the cylinder, and it is possible to cope with the downsizing of the apparatus. According to the third aspect of the present invention, when the operating state of the piston is a small stroke, the sliding operation of the sliding body that slides in the hollow member inserted into the upper liquid chamber of the cylinder formed above the piston. The first urging member and the second urging member
To apply the spring force of the urging member to the piston rod,
Even if the damping force is reduced to improve ride comfort, the spring force of the first urging member and the second urging member can be added to the piston rod to increase the apparent damping force. Steering stability can be ensured.

Further, by attaching the damping force variable mechanism to the piston rod above the piston, it becomes possible to compactly house the piston rod above the piston, and it is possible to cope with downsizing of the device.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view showing the entire configuration of a hydraulic shock absorber according to one embodiment of the present invention.

FIG. 2 is an enlarged longitudinal sectional view showing a piston 4 and a damping force variable mechanism.

FIG. 3 is a longitudinal sectional view showing a compression operation and an expansion operation at the time of a small stroke.

FIG. 4 is a longitudinal sectional view showing a compression operation and an expansion operation at the time of a large stroke.

FIG. 5 is a graph showing characteristics of a spring force of a variable damping force mechanism and a stroke of a piston.

FIG. 6 is a longitudinal sectional view of Modification Example 1 of the present invention.

FIG. 7 is a vertical cross-sectional view showing a compression operation and an expansion operation at the time of a small stroke in Modification 1.

FIG. 8 is a longitudinal sectional view showing a compression operation and an expansion operation at the time of a large stroke according to a first modification.

FIG. 9 is a longitudinal sectional view showing the entire configuration of a hydraulic shock absorber to which Modification 2 is applied.

FIG. 10 is an enlarged longitudinal sectional view showing a piston and a damping force variable mechanism according to a second modification.

FIG. 11 is a vertical cross-sectional view showing a compression operation and an expansion operation at the time of a small stroke in Modification 2.

FIG. 12 is a longitudinal sectional view showing a compression operation and an expansion operation at the time of a large stroke in Modification 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic shock absorber 2 Outer cylinder 3 Cylinder 4,74 Piston 5,75 Piston rod 6,80 Upper fluid chamber 7,81 Lower fluid chamber 10,76 Base valve mechanism 13,85 Reservoir chamber 16,78 Damping force generating mechanism 17 , 44, 79 Variable damping force mechanism 19, 21, 52, 49 Disc valve 20 Piston body 25, 46 Upper valve mechanism 26, 47 Lower valve mechanism 27, 48, 107 First communication path 28, 51, 108 Second communication path 31 Fixed member 32, 55, 105 Hollow member 32e, 55b, 115b First bypass passage 32f, 55c, 115c Second bypass passage 33, 56, 116 Sliding body 34, 57, 117 First elastic body 35, 58, 118 2 elastic body 36, 59 cap 37, 61, 88 intermediate liquid chamber 39, 65, 125 upper chamber 40, 66, 26 lower chamber 45 base 82 free piston

Claims (3)

[Claims] 1. A cylinder filled with a liquid, a piston defined in the cylinder as an upper liquid chamber and a lower liquid chamber, which slide in response to a force input to a piston rod, and provided on the piston. A hydraulic pressure damper having a valve that generates a damping force by opening or closing a communication hole according to a sliding operation direction of the piston and a damping force variable mechanism that changes a damping force according to a piston speed; A force variable mechanism integrally coupled with the piston, a hollow member inserted into a lower liquid chamber of the cylinder formed below the piston, and slidably inserted into the hollow member; A sliding body that slides by a liquid pressure difference between a first liquid chamber and a second liquid chamber formed inside the hollow member; a first urging member that urges the upper surface of the sliding body downward; A second attachment for urging the lower surface of the sliding body upward And a bypass passage provided in the hollow member and opened and closed according to the sliding position of the sliding body. When the piston is in a small stroke, the bypass passage is shut off when the piston is in a small stroke. A hydraulic shock absorber wherein a spring force of the first urging member and the second urging member is applied to the piston rod in accordance with a sliding operation of a sliding body. 2. An inner cylinder filled with liquid, a piston that slides in the inner cylinder in response to a force input to a piston rod, and a communication hole provided in the piston moves the piston. A valve that generates a damping force by opening or closing according to the direction, and an outer cylinder formed coaxially outside the inner cylinder,
A hydraulic damping device comprising: a base valve mechanism that opens and closes between a bottom of the outer cylinder and a bottom of the inner cylinder; and a damping force variable mechanism that changes a damping force according to a piston speed. A hollow member integrally connected to the base valve mechanism, and a first liquid chamber and a second liquid chamber inserted slidably into the hollow member and formed inside the hollow member. A sliding body that slides by a liquid pressure difference, a first biasing member that biases the upper surface of the sliding body downward, a second biasing member that biases the lower surface of the sliding body upward, A bypass passage provided in the hollow member and opened and closed according to the sliding position of the sliding body; when the piston is in a small stroke, the sliding body slides in a state where the bypass passage is shut off; The first urging member according to a dynamic operation; A hydraulic pressure damper, wherein a spring force of the second urging member is added. 3. A cylinder filled with a liquid, a piston defined in the cylinder as an upper liquid chamber and a lower liquid chamber, and slid in response to a force input to a piston rod, and provided on the piston. A hydraulic pressure damping device comprising: a valve that opens or closes a communication hole according to a sliding operation direction of the piston to generate a damping force; and a damping force variable mechanism that changes a damping force according to a piston speed. A force variable mechanism is integrally coupled to the piston rod, and a hollow member inserted into an upper liquid chamber of the cylinder formed above the piston, and is slidably inserted into the hollow member, A sliding body that slides by a liquid pressure difference between a first liquid chamber and a second liquid chamber formed inside the hollow member; a first urging member that urges the upper surface of the sliding body downward; A second portion for urging the lower surface of the sliding body upward; And a bypass passage provided in the hollow member and opened and closed according to the sliding position of the sliding body, wherein the bypass passage is shut off when the operating state of the piston is a small stroke. A hydraulic pressure damper, wherein a spring force of the first urging member and the second urging member is applied to the piston rod in accordance with a sliding operation of the sliding body.