JP3114135B2 - 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 interposed between a vehicle body and an axle for damping vibration from a road surface.

[0002]

2. Description of the Related Art In this type of hydraulic shock absorber, a piston rod is movably inserted into a cylinder via a piston, and the piston divides two upper and lower oil chambers into the cylinder. Is provided.

In general, a cylinder is provided with a communication port for connecting two upper and lower oil chambers, and a damping valve is provided at the outlet end of the port so as to be openable and closable. It has occurred.

[0004] Similarly, the base valve is provided with a port for communicating the lower oil chamber with the reservoir, and a damping valve is provided at the outlet end of this port so as to be openable and closable. Generates the opening pressure side damping force.

[0005]

In the above-mentioned conventional hydraulic shock absorber, for example, when the oil temperature rises at a high temperature, the viscosity of the oil changes due to the oil temperature change so that the oil viscosity decreases so that the damping force decreases. Therefore, there is a problem that the damping force changes.

[0006] Further, since the damping force is generated when the damping valve is opened from the port, there is a problem that abnormal noise is generated due to the damping valve.

Therefore, an object of the present invention is to change the oil temperature,
An object of the present invention is to provide a hydraulic shock absorber in which the damping force does not change even if the viscosity of the oil changes, the damping force can be varied depending on the piston speed, and the noise does not occur.

[0008]

According to a first aspect of the present invention, a piston rod is movably inserted into a cylinder via a piston, and the piston is provided with two upper and lower oils in the cylinder. In a hydraulic shock absorber in which a lower oil chamber communicates with a reservoir via a base valve, a piston main body is configured to be hollow, a collar is provided inside the piston main body, and an outer periphery of the collar and the piston main body are partitioned. A gap for generating a damping force which communicates the upper and lower oil chambers with the inner periphery is formed, and the collar is formed of a material having a large coefficient of thermal expansion and being elastically deformable.

According to a second aspect of the present invention, a piston rod is movably inserted into a cylinder via a piston.
The piston divides the upper and lower oil chambers inside the cylinder, and the lower oil chamber is a hydraulic shock absorber that communicates with the reservoir via the base valve.The base valve forms a hollow part that communicates the lower oil chamber with the reservoir. Equipped with a valve case,
A hollow collar is provided inside the valve case, and a gap for damping force generation is formed between the outer periphery of the collar and the inner periphery of the valve case to communicate upper and lower oil chambers. It is characterized by being molded from a large and elastically deformable material.

[0010]

During the expansion and contraction operation, the oil passes through the gap between the collar and the piston body or between the collar and the valve case, and a flow resistance, that is, a damping force is generated by the choke throttle.

When the oil temperature rises, the collar expands and narrows the gap, so even if the viscosity of the oil decreases, a decrease in the damping force is prevented. Since the contraction increases the gap, the damping force is prevented from increasing.

The oil flows through the gap as a choke, and no noise is generated because the damping valve is not used.

When the piston speed is high, the collar elastically deforms due to the pressure difference and changes the size of the gap, so that the damping force also changes depending on the piston speed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In FIG. 1, the right half shows an expanded state and the left half shows a compressed state.

A piston rod 11 is movably inserted into the cylinder 3 via a piston 12, and a hollow piston body 7 serving as a partition member constituting a body of the piston 12 has two upper and lower oil chambers 10, 5 in the cylinder 3. Is partitioned.

The piston body 7 has a hollow portion 24 and a port 25.
And the hollow portion 24 and the port 25 are connected to the upper and lower oil chambers 10,
5 is connected.

An outer tube 13 is provided concentrically outside the cylinder 3, and a reservoir 14 is defined inside the outer tube 13.

A base valve 1 is provided inside a lower portion of the cylinder 3.
The hollow valve case 1 serving as a partition member constituting the main body of the base valve 15 partitions the lower oil chamber 5 and the reservoir 14.

The valve case 1 has a hollow portion 26 and a port 27.
The hollow portion 26 and the port 27 allow the lower oil chamber 5 and the reservoir 14 to communicate with each other.

A collar 8 formed of a material having a larger coefficient of thermal expansion and elastic deformation than the piston body 7, for example, a synthetic resin, aluminum or the like, is provided inside the piston body 7 so as to be vertically movable. An annular or partial gap 19 for generating a damping force is formed between the outer periphery of the collar 8 and the inner periphery of the piston body 7 for generating a damping force in the axial direction. Through the lower oil chamber 5.

The rigidity of the collar 8 is reduced by selecting the material or changing the thickness.

The collar 8 is guided up and down by a guide 28, and is pushed by a lower sheet 34 by a spring 32 normally arranged in the hollow portion 29.

The collar 8 has a hollow portion 29, a port 30, and a notch 31 on the upper portion, thereby having a function of a check valve.

The valve case 1 of the base valve 15 has a port 27 for connecting the lower oil chamber 5 and the reservoir 14 and a notch 22.

A collar 2 that moves up and down along a guide 33 is disposed in the hollow portion 26 as an inner side of the valve case 1 so as to be movable up and down, and between the outer periphery of the collar 2 and the inner periphery of the valve case 1. An annular or partial gap 21 for generating a damping force is provided along the axial direction.

The gap 21 opens to the lower oil chamber 5 and communicates with the reservoir via a port 27.

The collar 2 has a port 35 and is normally held down by a seat 37 by a spring 37, and has the function of a check valve.

Further, the collar 2 is formed of an elastically deformable material having a larger coefficient of thermal expansion than the valve case, like the collar 8.

During the extension operation, the collar 8 is pushed by the seat 34 to close the port 30, whereby the upper oil chamber 1 is closed.
0 flows out to the lower oil chamber 5 through the gap 19 and the gap 1
An expansion damping force is generated by the choke effect of 9, and the oil corresponding to the discharge volume of the piston rod 11 is pushed up from the port 27 from the reservoir 27 by the reservoir 14 and is sucked into the lower oil chamber 5.

At the time of compression, the oil in the lower oil chamber 5 pushes up the collar 8 from the port 25 and flows out to the upper oil chamber 10, and the oil corresponding to the volume of the piston rod 11 penetrating the base valve 15
Flows out to the reservoir 14 through the gap 21, the port 27, and the notch 22, and generates a compression-side damping force due to the flow resistance of the gap 21.

Even if the oil temperature changes, for example, the oil temperature rises and the viscosity of the oil decreases, the collars 2 and 8 expand with the increase in the oil temperature, and the gaps 21 and 19 are narrowed. Therefore, a decrease in the damping force is prevented, and when the oil temperature similarly drops, the collars 2 and 8 contract and enlarge the gaps 21 and 19, so that the damping force does not increase and a constant damping force is always generated.

When the piston speed is low during the expansion / contraction operation, the pressure in the upper oil chamber 10 or the lower oil chamber 5 is low as shown in the right-hand cross section in FIGS. There is no pressure difference between the outside and the outside.

Therefore, the collars 8 and 2 are not elastically deformed, the size of the gaps 19 and 21 is not changed, and the damping force characteristic is shown by a linear graph a shown in FIG.

However, as shown in FIGS. 2 and 3, when the piston speed is high, the damping force increases depending on the piston speed.

That is, the pressure in the upper oil chamber 10 increases during extension, and this pressure acts on the inner peripheral side and the outer peripheral side of the collar 8 as shown in FIG. 2, and the pressure below the gap 19 is small. Due to the pressure difference, the lower part of the collar 8 is elastically deformed toward the outer side of the piston body 7 as shown in the left cross section of FIG. 2 and narrows the gap 19, so that the damping force characteristic is high as shown in the graph b of FIG. It becomes an increase type.

Similarly, the lower part of the collar 2 on the side of the base valve 15 is elastically deformed due to the pressure difference as shown in the left-hand cross section.

FIG. 4 shows another embodiment of the present invention.

In this embodiment, a check valve is provided on the upper part of the collar on the piston side so as to be openable and closable, and other structures, operations and effects are basically the same as those of the embodiment of FIG.

The components having the same structure are denoted by the same reference numerals and their details are omitted.

The collar 8 is provided in the piston body 7, and a gap 19 is formed between the outer periphery of the collar 8 and the inner periphery of the piston body 7.

The collar 8 is provided with an axial port 30a opening to the upper oil chamber 10 and the port 25.
a check valve 3 urged by a spring 37 at the upper end of a
8 is provided to be freely opened and closed.

The collar 8 is formed of an elastically deformable material having a larger thermal expansion force than the piston body 7.

During the extension operation, the oil in the upper oil chamber 10
The oil in the lower oil chamber 5 flows out of the ports 25 and 30a through the check valve 38 during the compression operation.
To open and flow out into the upper oil chamber 10.

When the piston speed is low at the time of extension, the pressure in the upper oil chamber 10 is low and the collar 8 is not elastically deformed, as shown in the right section of FIG.

However, when the piston speed is high, the pressure in the upper oil chamber 10 increases, and this pressure acts on the gap 21, but acts on the port 30 a of the collar 8 because the check valve 38 exists. Without doing so, the pressure inside the hoat 30a is low.

For this reason, the collar 8 is elastically deformed inward by the pressure in the gap 21 so as to be separated from the piston body 7 by the pressure in the gap 21, and the gap 21 becomes large, as shown in the cross section on the left side of FIG. 4.

For this reason, the damping force characteristic when the piston speed is high becomes a saturation type as shown by the graph c in FIG.

FIG. 5 similarly shows another embodiment of the present invention.
In this embodiment, a check valve is provided above the collar on the base valve side as in the embodiment of FIG.

That is, a port 40 and a notch 41 are provided in the collar 2, and a check valve 38 b urged by a spring 42 is provided above the port 40.

Other structures, operations and effects are basically the same as those in FIG.
This is the same as the embodiment.

In this case, during the compression operation, when the piston speed is low, the collar 2 does not elastically deform and the gap 2
Although the size of 1 does not change, when the piston speed is high, the pressure in the lower oil chamber 5 increases, and this pressure acts on the gap 21.

In the hollow portion of the collar 2, a check valve 3 is provided.
At 8b, no pressure acts and the pressure is low.

Therefore, the upper portion of the collar 2 is elastically deformed in a direction away from the valve case 1 by the pressure of the gap 21, and
In order to increase 1, the damping force characteristic becomes a saturation type shown by a graph c in FIG.

FIG. 6 shows another embodiment of the present invention, in which a check valve is provided below the collar on the base valve side.

Other structures, functions and effects are basically the same as those in FIG.

In this case, a port 46 is provided on the upper part of the collar 2, a check valve 43 urged by a spring 44 is provided on the upper part of the port 27 of the valve case 1 so as to be openable and closable. A port 45 communicating with the reservoir 14 is formed.

In this case, during the compression operation, when the piston speed is low, as shown in the right-hand section of FIG.
Does not change in size.

However, when the piston speed is high, the pressure in the lower oil chamber 5 increases, and this pressure is
Also acts in the hollow part of

At this time, since the pressure below the gap 21 is lower than that above, the lower part of the body of the collar 2 is elastically deformed and bent toward the outer valve case 1 side, and the gap 21 is narrowed.

For this reason, the damping force characteristic is of the increasing type shown by the graph b in FIG.

The collar in each of the above embodiments can be made elastically deformable depending on the material, made thinner as a whole, or cut out at several or one of the inner peripheral wall or outer peripheral wall to make it partially thin. .

[0063]

According to the present invention, the following effects can be obtained.

A collar having a large coefficient of thermal expansion is provided inside the piston body or the valve case, and a gap for damping force is provided between the collar and the piston body or the valve case. Damping force is generated by the resistance.

The collar expands or contracts due to a change in the oil temperature, and the size of the gap changes. Therefore, even if the viscosity of the oil changes due to the change in the oil temperature, the damping force does not change.

The damping force of the choke effect is generated by utilizing the gap, and the generation of abnormal noise can be prevented since the damping valve is not used.

Since the collar is provided inside the piston body or the valve case, the dimensions of the cylinder itself do not change, and the design and management of only the internal structure of the piston or the valve case are sufficient, so that the workability is good and the cost is advantageous. is there.

Since the collar is provided in the piston body or the valve case, the piston body or the valve case itself does not need to be formed long in the axial direction, and the effective stroke increases.

Since the temperature characteristic of the damping force is compensated for by the thermal expansion difference between the piston body or the valve case and the collar, the degree of freedom in setting the material is large.

Since the collar is formed of an elastically deformable material and is hollow, when the piston speed is high, the collar elastically deforms due to the pressure difference between the inside and the outside of the collar, and changes the size of the gap. Thus, the damping force can be changed depending on the piston speed.

[Brief description of the drawings]

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

FIG. 2 is an enlarged cross-sectional view of a piston portion showing an operation state of FIG.

FIG. 3 is an enlarged cross-sectional view of a base valve showing an operation state of FIG. 1;

FIG. 4 is a sectional view of a piston portion according to another embodiment of the present invention.

FIG. 5 is a sectional view of a base valve unit according to another embodiment of the present invention.

FIG. 6 is a sectional view of a base valve according to another embodiment of the present invention.

FIG. 7 is a graph showing damping force characteristics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve case 2,8 Collar 3 Cylinder 5,10 Oil chamber 7 Piston body 11 Piston rod 12 Piston 14 Reservoir 19,21 Clearance

Continuation of the front page (56) References JP-A-56-76743 (JP, A) JP-A-61-52438 (JP, A) JP-A-56-35832 (JP, A) , U) Fully open sho 56-87645 (JP, U) Really open sho 59-70945 (JP, U) Real open sho 59-96440 (JP, U) Real open sho 59-115140 (JP, U) 34-6011 (JP, B1) US Patent 2,821,268 (US, A) German Patent Application Publication 2002078 (DE, A1) German Patent Application Publication 2932245 (DE, A1) French Patent Invention 2070395 (FR, B1) (58) Field surveyed (Int.Cl. ⁷ , DB name) F16F 9/52 F16F 9/34 F16F 9/50 B60G 13/08

Claims (2)

(57) [Claims] 1. A piston rod is movably inserted into a cylinder via a piston, the piston partitions upper and lower oil chambers into the cylinder, and a lower oil chamber communicates with a reservoir via a base valve. In the hydraulic shock absorber, the piston main body is configured to be hollow, a hollow collar is provided inside the piston main body, and a damping force for communicating upper and lower oil chambers between the outer circumference of the collar and the inner circumference of the piston main body is provided. A hydraulic shock absorber, wherein a gap is formed, and the collar is formed of a material having a large coefficient of thermal expansion and elastic deformation. 2. A piston rod is movably inserted into a cylinder via a piston, the piston partitions upper and lower oil chambers into the cylinder, and a lower oil chamber communicates with a reservoir via a base valve. In the hydraulic shock absorber, the base valve includes a valve case having a hollow portion communicating the lower oil chamber and the reservoir, a hollow collar is provided inside the valve case, and an outer circumference of the collar and an inner circumference of the valve case are provided. A hydraulic shock absorber, wherein a gap for generating a damping force is formed between the upper and lower oil chambers, and the collar is formed of a material having a large coefficient of thermal expansion and being elastically deformable.