JP3034413B2 - Hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber for damping vibration from a road surface by interposing between a vehicle body (above a spring) and a wheel (below a spring) of a vehicle such as an automobile. The present invention relates to a hydraulic shock absorber that performs a damping action by utilizing a choke action by a gap between the hydraulic shock absorbers.

[0002]

2. Description of the Related Art In this type of hydraulic shock absorber, the outer diameter of a piston moving in a damper cylinder is controlled by using a large diameter portion which slides on the inner wall of the damper cylinder and an outer periphery made of a material made of a material having a high coefficient of thermal expansion. The collar having a compensating function is formed into a small-diameter portion having a small-diameter portion fitted therein, and an annular gap is formed between the outer periphery of the collar and the inner wall of the damper cylinder.

[0003] There has been known an oil chamber in which upper and lower oil chambers are communicated with each other through an annular gap to generate an extension damping force by using a choke effect of the annular gap.

Of course, the idea is that a collar having the same temperature compensation function is fitted to the outer periphery of the case of the base valve disposed at the lower end of the damper cylinder, and has a choke effect between the outer periphery of this collar and the inner wall of the damper cylinder. By forming the annular gap, it can be similarly applied to a base valve which is a compression-side damping force generating mechanism.

[0005] However, in the former piston portion, since the damper cylinder and the piston which move relative to each other form an annular gap having a choke action, the annular gap must be kept constant at all positions of the piston stroke. Is difficult, and as a result, there arises a problem that the damping force characteristic tends to vary.

Therefore, in order to solve these problems, a collar is fitted to a piston rod or a base valve guide located in a piston or base valve case, and the outer periphery of the collar and the inner wall of the piston or base valve are connected to each other. Thus, an annular gap having a choke effect may be formed between the two. As a result, the axial length of the piston or the base valve case can be reduced, so that this kind of hydraulic shock absorber can be configured without impairing the effective stroke.

On the other hand, in consideration of the thermal expansion of the collar, a predetermined distance is set between the inner diameter of the collar and the outer diameter of the piston rod or the base valve guide at normal temperature so that the contraction of the collar is not hindered even at a low temperature. The gap must be provided. As a result, when the collar is assembled at normal temperature, the collar is assembled eccentrically with respect to the piston rod or the base valve guide, and the flow resistance of the hydraulic oil passing through the annular gap decreases with the increase in the amount of eccentricity. As a result, the generated damping force is reduced, and the damping force characteristics vary.

In order to minimize this variation,
The collar may be assembled at a low temperature, or the length of the annular gap may be increased in the axial direction to reduce the influence of the decrease in the damping force due to the eccentricity, but the former means increases the assembly cost, In the latter case, there is a disadvantage that the axial length of the piston or the base valve becomes longer and the effective stroke as the hydraulic shock absorber becomes shorter.

Therefore, a collar having a temperature compensating function made of a material having a high coefficient of thermal expansion is disposed in the piston or the base valve, and the upper and lower oil chambers are interposed between the collar and the piston or the collar and the base valve. And an annular gap having a choke action that communicates with each other, and a center portion of the collar is interposed between the piston rod and the base valve guide with an elastic material for positioning interposed therebetween. No. 5-2290).

With the above configuration, even when the center portion of the collar is positioned with an elastic material at normal temperature and assembled, the collar can be elastically deformed and contracted at a low temperature. Therefore, even when the collar is assembled at room temperature, the shrinkage of the collar at the time of low temperature can be absorbed by the elastic material, so that the collar can be assembled while being kept concentric with the elastic material.

[0011]

In the above-described conventional hydraulic shock absorber, the collar contracts in accordance with the temperature, whereby the temperature of the damping force can be compensated.

However, in the above-mentioned conventional hydraulic shock absorber, it is difficult to obtain a high-strength material for the collar and the elastic member because the collar as the damping force generating member and the elastic member for temperature compensation are the same. However, there is a problem that durability is poor.

That is, if a material having a high coefficient of thermal expansion is used to improve the temperature compensation, the material having a high coefficient of thermal expansion generally has low strength and thus has a reduced durability. On the other hand, if a material having a high mechanical strength is used to improve the durability, a material having a high mechanical strength generally has a low coefficient of thermal expansion, so that the required temperature compensation cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has a temperature expansion and contraction member (extension and contraction member) for temperature compensation and a collar as a damping force generation member provided as separate members. An object of the present invention is to provide a hydraulic shock absorber with improved performance.

[0015]

Means for Solving the Problems To solve the above problems, the present invention is characterized by taking the following means.

According to the first aspect of the present invention, there is provided a piston which is connected to the piston rod and slides in the cylinder, and an annular first collar provided inside the piston. Between the pistons, a first and a second working fluid chamber which communicates with the upper and lower working fluid chambers and has a choke effect.
In the hydraulic shock absorber having the annular gap formed, the first collar is configured to be movable in a direction perpendicular to the axis of the piston rod, and between the piston and the first collar. A first thermal expansion member having a large thermal expansion coefficient is provided, and a first thermal expansion member formed between the first collar and the piston by the expansion and contraction of the first thermal expansion member.
Wherein the shape of the annular gap is changed.

According to the second aspect of the present invention, there is provided a base valve connected to a base valve guide and fixed to a cylinder, and an annular second collar provided in the base valve. A hydraulic shock absorber comprising an annular gap which communicates hydraulic fluid chambers above and below the base valve and forms a choke action between the second collar and the base valve. A second thermal expansion member having a large thermal expansion coefficient is provided between the base valve and the second collar, and the second thermal expansion member is configured to be movable in a direction perpendicular to the axis of the guide. It is characterized in that the configuration of the second annular gap formed between the second collar and the base valve is changed by the expansion and contraction effect of thermal expansion and contraction.

[0018]

The above-mentioned means operates as follows.

According to the first aspect of the present invention, a damping force is generated by the annular gap formed between the first collar and the piston. Further, since the annular gap changes due to a contraction action corresponding to the temperature of the first thermal expansion member disposed between the first collar and the piston, temperature compensation is performed.
On the other hand, since the first thermal expansion member as the temperature compensation member and the first collar as the damping force generating member are separate members, the first thermal expansion member and the collar act respectively. It is possible to adopt a material suitable for the function. That is, a material having a high coefficient of thermal expansion can be used as the first thermal expansion member, and the temperature compensation can be improved. Further, a material having high mechanical strength can be used as the first collar, so that durability can be improved.

According to the second aspect of the present invention, a damping force is generated by the annular gap formed between the second collar and the base valve. Further, since the annular gap changes due to a contraction action corresponding to the temperature of the second thermal expansion member disposed between the second collar and the base valve, temperature compensation is performed. On the other hand, the second thermal expansion member, which is a temperature compensation member, and the second collar, which is a damping force generating member, are separate members, so that the second thermal expansion member and the second collar are separately provided. It is possible to adopt a material suitable for the function to be operated. Therefore, a material having a high coefficient of thermal expansion can be used as the second thermal expansion member, and the temperature compensation can be improved. In addition, a material having high mechanical strength can be used as the second collar, so that durability can be improved.

[0021]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a hydraulic shock absorber 1 according to the present invention.
The hydraulic shock absorber 1 includes a cylindrical cylinder 2, a cylindrical outer shell 3 surrounding the cylinder 2 and arranged concentrically, and a cylinder 2 slidably in the cylinder 2. It comprises a piston 4 fitted therein, and a base valve 5 interposed between the lower shell of the cylinder 2 and the outer shell 3.

The upper ends of the cylinder 2 and the outer shell 3 are closed by a bearing case 6. A step 6 a formed in the bearing case 6 is fitted to the upper end of the cylinder 2, whereby the upper end of the cylinder 2 is closed. Is kept concentric with the outer shell 3.

The lower end of the outer shell 3 is closed by a bottom cap 7, and the lower end leg 5 a of the base valve 5 is pressed onto the bottom cap 7, whereby the cylinder 2 is moved through the base valve 5 and the bottom cap 7. Is concentrically held with respect to the outer shell 3.

From the piston 4, a piston rod 8
Extend upward, and the piston rod 8
Are projected through the bearing case 6 to the outside of the cylinder 2 while being guided by a bush 9 provided in the bearing case 6 and under an oil-tight state by a seal 10.

Thus, the piston 4 partitions the interior of the cylinder 2 into an upper oil chamber 11 on the piston rod 8 side and a lower oil chamber 12 on the base valve 5 side.
The lower oil chamber 12 is connected to the cylinder 2 and the outer shell 3.
It is isolated from the reservoir chamber 13 between them.

The piston 4 defining the upper oil chamber and the lower oil chamber 12 has a plurality of pressure ports 14 arranged concentrically. After the piston 4 is inserted into the lower part of the piston rod 8, the piston 4 is inserted from below. It is fixed to the lower end of the piston rod 8 by tightening with a bolt 15. The pressure port 14 of the piston 4 is
The upper opening to the upper oil chamber 11 is normally closed by a non-return valve 17 arranged by the urging force of a leaf spring 16, and the lower opening is always open to the oil chamber 12.

The piston rod 8 and the piston bolt 15 are each formed in a hollow shape, and the side wall of the piston rod 8 is provided with an extension port 18 communicating with the hollow portion 8a of the piston rod 8. Extension port 1
The upper oil chamber 11 and the lower oil chamber 12 communicate with each other through hollow portions 8 a and 15 a formed in the piston rod 8 and the piston nut 15. The upper oil chamber 11 is discharged from the gap between the piston rod 8 and the bush 9 to the reservoir chamber 13 through a check function portion (not shown) of the seal 10 and a through hole 19 formed in the seal case 6. is there.

The vicinity of the center of the piston bolt 15 is circular. A collar 22 is inserted into the outer periphery of the vicinity of the center of the piston bolt 15, and the inside of the piston bolt 15 near the center of the circular portion 15a. Is the spring 21
And the thermal expansion pin 20 are installed facing each other. The ends of the spring 21 and the thermal expansion pin 20 are collars 2 respectively.
2, the spring 21 eccentrically moves the collar 22 leftward in the figure with respect to the circular portion 15a of the piston bolt 15 (this direction is perpendicular to the axis of the piston rod 8). It is energizing. Figure 2 shows this situation.
Shown in FIG. 2 is a sectional view taken along line AA in FIG.

The thermal expansion pin 20 provided inside the piston bolt 15 is made of a material having a high thermal expansion coefficient whose length expands with temperature, and the temperature of the hydraulic oil in the shock absorber rises. At the same time, the temperature of the thermal expansion pin 20 also increases, the length of the thermal expansion pin 20 increases, and the collar 22 is moved rightward in FIG.
The annular gap 40 is changed so as to be concentric (see FIG. 3).
Indicates this state). Further, an upper end opening of the annular gap 40 communicates with the extension port 18 through the hollow portions 8 a and 15 a of the piston rod 8 and the piston bolt 15, and a lower end opening directly communicates with the lower oil chamber 12. I have.

Thus, the annular gap 40 provides flow resistance to the flow of hydraulic oil from the upper oil chamber 11 toward the lower oil chamber 12 through the extension port 18 and the hollow portions 8a, 15a of the piston rod 8 and the piston bolt 15. , And functions as an oil passage that generates the extension-side damping force. Further, as the temperature of the hydraulic oil rises, the thermal expansion pin 20 extends,
The annular gap 40, which has been eccentric due to the displacement of the collar 22, changes in a direction concentric with the circular portion of the piston bolt 15, thereby performing a temperature correction function for always maintaining a constant damping force regardless of the temperature of the hydraulic oil. (FIG. 3 shows the color 22
Is displaced).

On the other hand, in the same manner as in the case of the piston 4 in the base valve 5, a collar 29 is formed on the outer periphery of the base valve bolt 27, and a spring 31 and a temperature compensation made of a material having a high coefficient of thermal expansion are formed inside. Thermal expansion pin 3 with function
0 to form an annular gap 41 between the outer periphery of the collar 29 and the inner peripheral wall of the base valve 5. Since the base valve 5 and the piston 4 have a similar structure, the base valve 5
In the configuration described above, the components corresponding to the configuration of the piston 4 are denoted by the same reference numerals, and description thereof is omitted.

Thus, the lower oil chamber 12 isolated by the base valve 5 is a pressure-side oil passage that passes through the annular gap 41 from the hollow portion of the base valve bolt 27 and passes between the lower leg portions 5a of the base valve 5. It will be communicated with the reservoir chamber 13. At the same time, the reservoir chamber 13 is moved between the lower leg 5a of the base valve 5 and the oil hole 26 of the base valve 5.
A non-return valve 25 that opens toward the lower oil chamber 12 is provided at the upper opening of the oil hole 26 serving as the expansion-side oil path. is there.

Next, the operation of the hydraulic shock absorber 1 according to this embodiment configured as described above will be described.

During the extension stroke of the hydraulic shock absorber 1 operating in the direction in which the piston rod 8 comes out of the cylinder 2 (upward), the hydraulic oil in the upper oil chamber 11 flows from the extension port 18 of the piston rod 8. It passes through the hollow part of the piston rod 8 and flows into the hollow part of the piston bolt 15. Then, the fluid further flows through the annular gap 40 between the piston bolt 15 and the collar 22 to the lower oil chamber 12, and at this time, the expansion resistance according to the elongation speed is determined by the flow resistance of the hydraulic oil passing through the annular gap 40. Generates side damping force. At the same time, an amount of hydraulic oil equivalent to the rejected volume of the piston rod 8 passes from the reservoir chamber 13 to the lower leg portion 5a, which is the extension-side oil passage of the base valve 5, through the oil hole 26, and to the non-return valve 25. Is supplied to the lower oil chamber 12 while pushing open.

On the other hand, on the other hand, during the pressure side stroke of the hydraulic shock absorber 1 which operates in the direction in which the piston rod 8 enters, the hydraulic oil in the lower oil chamber 12 is supplied from the pressure side port 14 of the piston 4 to the non-pressure side. It flows into the upper oil chamber 11 while pushing and opening the return valve 17. In parallel with this, an amount of hydraulic oil corresponding to the invading volume of the piston rod 8 passes through the hollow portion of the base valve bolt 27 and passes through the base valve 5.
Gap 41 between base and collar 29 and base valve 5
Flows into the reservoir chamber 13 through the space between the lower leg portions 5a of the first and second portions, and at this time, a damping force corresponding to the compression speed is generated by the flow resistance of the hydraulic oil passing through the annular gap 41.

On the other hand, regarding the temperature compensation, when the hydraulic oil is in a low temperature state as described above, the thermal expansion pin 20 is in a contracted state as shown in FIG. It is biased by 22 and is in an eccentric position. When the temperature of the hydraulic oil rises, the thermal expansion pin 20 having a high coefficient of thermal expansion expands and the collar 22
Is pressed against the spring force of the spring 22, and the collar 22 is displaced to a position substantially concentric with the circular portion 15a of the piston bolt 15, as shown in FIG.

Here, the amount of oil (Q) flowing through the annular gap in the eccentric state shown in FIG. 2 and the concentric state shown in FIG. 3 will be considered. The collar 22, the thermal expansion pin 20, the spring 21, and the annular gap 4 in the piston 4
Numeral 0 has the same structure as the collar 29, the thermal expansion pin 30, the spring 31, and the annular gap 50 in the base valve 5, and performs the same operation. Therefore, only the oil amount Q flowing through the annular gap 40 in the piston 4 will be described. I do.

Now, the length of the annular gap 40 (length in the vertical direction in FIG. 1) is L, the viscosity of the hydraulic oil is μ, the density of the hydraulic oil is ρ, the hydraulic oil inflow portion and the hydraulic oil outflow of the annular gap 40. Δp, the outer diameter of the circular portion 15a of the piston bolt 15 is d, the gap between the inner wall of the collar 22 and the circular portion 15a is h, and the amount of eccentricity when the collar 22 is eccentric. Are defined as e, respectively.

Then, the flow rate Q when the collar 22 is concentric with the circular portion 15a is expressed by the following equation.

[0041]

(Equation 1)

On the other hand, the collar 22 has the circular portion 15a.
And the flow rate Q in the eccentric state is expressed by the following equation.

[0043]

(Equation 2)

As is apparent from the above equations, the flow rate of the hydraulic oil flowing through the annular gap 40 varies when the collar 22 is eccentric with the circular portion 15a and when the collar 22 is concentric. In addition, since the eccentricity of the collar 22 is caused by the thermal expansion pin 20 which expands in accordance with the temperature of the hydraulic oil, the flow rate flowing through the annular gap 40 changes depending on the temperature of the hydraulic oil, thereby performing temperature compensation. be able to. Specifically, when e = h (that is, when eccentricity with low hydraulic oil temperature occurs), when e = h (that is, when
The flow rate is about 2.5 times as large as that in the case of concentric operation where the hydraulic oil temperature is high, and temperature compensation can be performed in this range.

The above formulas are described in "New Edition Hydraulic and Pneumatic Handbook (Japan) Hydraulic and Pneumatics Society, Ohmsha", Chapter I, Fundamentals, Chapter 3 Fluid Dynamics Theory in Hydraulic and Pneumatic and its Applications (Pages 35-36).

As described above, in this embodiment, the color 2
A damping force is generated by the annular gap 40 (50) formed between the piston 2 (29) and the piston 4 (base valve 5), and a buffer function can be realized. The annular gap 40 (50) is provided between the collar 22 (29) and the piston 4 (base valve 5).
Since the temperature changes due to the contraction effect corresponding to the temperature of 0), temperature compensation is performed. On the other hand, a thermal expansion pin 20 (30) as a temperature compensating member and a collar 22 (2) as a damping force generating member are provided.
9) is a separate member from the thermal expansion pin 20 (3).
0) and the collar 22 (29) can be formed of a material suitable for each function, and it is possible to improve both temperature compensation and durability.

[0047]

As described above, according to the present invention, the first and second thermal expansion members serving as temperature compensating members and the first and second collars serving as damping force generating members are separate members. Therefore, the first and second thermal expansion members and the first and second collars can employ materials suitable for their respective functions.

That is, it is possible to use a material having a high coefficient of thermal expansion as the first and second thermal expansion members.
In addition, a material having high mechanical strength can be used as the second collar, and both temperature compensation and durability can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a hydraulic shock absorber according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, showing a state in which the collar is eccentric.

FIG. 3 is a cross-sectional view taken along line AA in FIG. 1, showing a state in which a collar is concentric with a circular portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic shock absorber 2 Cylinder 3 Outer shell 4 Piston 5 Base valve 6 Bearing case 6a, 15b Step 7 Bottom cap 8 Piston rod 8a, 15a Hollow chamber 11 Upper oil chamber 12 Lower oil chamber 13 Reservoir chamber 14 Pressure port 15 Piston bolt 15a circular portion 16, 32 leaf spring 17 non-return valve 18 extension side port 19 through hole 20, 30 thermal expansion pin 21, 31 spring 22, 29 collar 25 non-return valve 26 oil hole 27 base valve bolt 40, 50 annular gap

Continuation of the front page (56) References JP-A-56-76743 (JP, A) JP-A-51-39370 (JP, A) JP-A-57-110342 (JP, U) JP-A-59-63243 (JP, A) , U) Fully open 1986-89539 (JP, U) Fully open 1979-15191 (JP, U) Fully open 3-119187 (JP, U) Fully open 4-117941 (JP, U) Fully open 6-1879 (JP, U) JP-A-6-1880 (JP, U) JP-A 6-73486 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16F 9/52 F16K 31/64

Claims (2)

(57) [Claims] 1. A piston connected to a piston rod and sliding in a cylinder, and an annular first collar provided inside the piston, between the first collar and the piston. , A first hydraulic fluid chamber communicating with the upper and lower hydraulic fluid chambers and having a choke action.
In the hydraulic shock absorber having an annular gap formed therein, the first collar is configured to be movable in a direction perpendicular to the axis of the piston rod, and between the piston and the first collar. A first thermal expansion member having a large thermal expansion coefficient is provided, and the shape of a first annular gap formed between the first collar and the piston by the expansion and contraction action of the first thermal expansion member is provided. A hydraulic shock absorber characterized by being configured to change. 2. A base valve connected to a base valve guide and fixed to a cylinder, and an annular second collar provided in the base valve, wherein the second collar and the base valve are provided. Between the upper and lower hydraulic fluid chambers of the base valve, and an annular gap for performing a choke action is formed, wherein the second collar is perpendicular to the axis of the base valve guide. And a second thermal expansion member having a large thermal expansion coefficient is provided between the base valve and the second collar to expand and contract the second thermal expansion member. A hydraulic shock absorber characterized in that the shape of a second annular gap formed between the second collar and the base valve is changed.