JPH0432254B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a shock absorber, and particularly to a shock absorber for vehicles such as automobiles.

"Prior Art" Conventionally, a cylinder with a smaller diameter is housed inside a larger diameter outer shell, and the outer shell is fitted onto the outer circumferential surface of the large diameter portion of a stepped rod guide, and the cylinder is fitted onto the outer circumferential surface of the small diameter portion of a stepped rod guide. By doing so, both are held concentrically, and a piston rod carrying a piston that slides in sliding contact with the cylinder inner circumferential surface near the inner end slides on the inner circumferential surface of the guide bush fitted to the rod guide inner circumferential surface. A shock absorber that is movably inserted and has a straight inner circumferential surface of the hole provided in the shaft portion of the rod guide and guide bush, or a shock absorber that has a small inner diameter at the center and a large inner diameter at both ends. It is well known.

``Problem to be solved by the invention'' This type of shock absorber, especially a shock absorber for automobiles, is usually installed in an inclined position, so the piston rod may be inclined with respect to the cylinder while the automobile is running. Due to the axial misalignment that occurs between the piston rod and the rod guide due to bending, the end of the rod guide comes into partial contact. If the piston rod and rod guide make uneven contact, the lubrication between the two deteriorates, reducing the durability of the rod guide.Furthermore, the frictional resistance of the rod guide, especially static frictional resistance or frictional resistance at very slow speeds, increases, resulting in a shock. Another drawback is that the ride quality of the absorber becomes unstable. This drawback is particularly noticeable when the wheels run over uneven road surfaces.

In particular, when the piston rod is greatly bent,
Even if the guide bushing was simply provided with a drum shape, uneven contact sometimes occurred. In order to avoid this, if a large drum shape was provided in the guide bush, the guiding function itself would deteriorate and the piston rod would be more likely to deflect. Due to the bending of the piston rod, conventional guide bushes suffer from a lot of wear and have the disadvantages of poor durability as described above.

"Means for Solving the Problems" In view of such circumstances, the present invention has a cylinder with a smaller diameter installed inside a larger diameter outer shell, and the outer shell is attached to the outer circumferential surface of the large diameter portion of a stepped rod guide. By fitting the cylinders to the outer circumferential surface of the small diameter portion, they are held concentrically, and the inner circumferential surface of the guide bush fitted to the inner circumferential surface of the rod guide has a cylinder near the inner end. In a shock absorber in which a piston rod carrying a piston that is in sliding contact with an inner circumferential surface is slidably inserted, there is a gap between at least the upper inner circumferential surface of the stepped rod guide and the outer circumferential portion of the guide bush. and the guide bush is provided with an elastically deformable end that can be deformed in a radial outer circumference in a direction that closes the gap when the piston rod swings, at the end on the side where the gap is provided. This is achieved by a shock absorber characterized by:

"Function" According to the configuration of the present invention, even if the piston rod swings relative to the rod guide and axial misalignment occurs, at least the upper inner circumferential surface of the stepped rod guide has the outer circumference of the guide bush. A gap is set between the guide bush and the guide bush, and the guide bush has an outer periphery that is deformable in the radial direction, which is the direction to close the gap when the piston rod swings, at the end on the side where the gap is provided. Since the elastically deformable end is provided, the end of the guide bush deforms toward the rod guide when the piston rod deforms excessively, resulting in uneven contact between the outer peripheral surface of the piston rod and the end of the guide bush. The degree of friction is reduced, and wear caused by uneven contact can be significantly reduced. Then, when the axial misalignment of the piston rod is reduced and the excessive deformation is released, the elastically deformed end of the guide bush substantially returns to its original shape due to its elasticity, maintaining good guiding function. . The elasticity of the elastically deformed end of the guide bush serves as an auxiliary action to return the piston rod in a direction that eliminates deformation and axial misalignment.

"Example" The present invention will be described below with reference to the illustrated example.
In FIG. 2, the lower end of an outer shell 2 housing a cylinder 1 therein is connected to a wheel (not shown), and the piston rod 4 of a piston 3 slidably fitted into the cylinder 1 is connected to its upper end. is connected to the vehicle body.

A large diameter portion 5a of a stepped rod guide 5 is fitted into the upper part of the outer shell 2, and a small diameter portion 5b of the rod guide 5 is fitted into the upper end opening of the cylinder 1 (see Fig. 1). . Then, a guide bush 7 is fitted into the inner peripheral surface 6 of the shaft portion of the rod guide 5, and the piston rod 4 is inserted into the guide bush 7.
At the same time, the inner circumferential surface 7a of the
An oil seal 8 sealing the upper part of the outer shell 2 is slidably penetrated and projected to the outside. Further, an outer cylinder 9 is attached to the upper end of the piston rod 4 to cover the oil seal 8 portion.

A valve 10 is provided inside the piston 3, and the inside of the cylinder 1 is filled with oil, and a reservoir 11 is provided between the cylinder 1 and the outer shell 2.

This configuration is basically the same as the conventional one, and when the cylinder 1 is moved forward or backward, the oil in the cylinder 1 passes through the valve 10 inside the piston and is connected to the piston rod and the cylinder 1. It allows the relative movement of the oil and provides a damping effect based on the viscous resistance of this oil.

However, FIG. 1 is an enlarged view of the main part of the present invention,
An enlarged portion 5c is provided on the inner circumferential surface of the upper end of the rod guide 5, which is wider than the inner diameter of the central portion, and an enlarged portion 7c is provided on the inner circumferential surface of the upper end of the guide bush 7, which is wider than the inner diameter of the central portion, and A distance C is set between the expanded portion 5c of the rod guide 5 and the expanded portion 7c of the guide bush 7. During this time, the end of the guide bush 7 on the side C is an elastically deformed end.

The expanded portions 5c and 7c have a tapered upper end, a cylindrical shape extending to the lower end, and a smooth continuity between them.

The above distance C is generally desirably 1 to 300μ,
A range of 30 to 60μ is more desirable, but it should be set within a range that allows for deformation of the end of the guide bush 7. In other words, this portion serves as an elastically deformed end. Although the deformation is described as elastic deformation, it may be substantially elastic deformation including some plastic deformation. This means that it is important to allow elastic deformation in consideration of the durability life of the shock absorber. From this point of view, as long as the elasticity of the elastically deformable end, which can be deformed in the radial direction outer periphery in the direction that closes the gap when the piston rod swings, is not completely lost, oil or grease can be applied to the gap C. , an elastic body or the like may be interposed.

In the above configuration, when there is a gap 〓C, an oil film is formed between the expanded portion 7c of the guide bush 7 and the piston rod 4, so the lubrication state is very good. When the rod guide 5 swings relative to the piston rod 4, the upper end of the rod guide 5 where uneven contact is particularly noticeable comes into smooth sliding contact with the outer circumferential surface of the piston rod 4. Furthermore, when the piston rod 4 swings greatly, the expanded portion 7c of the guide bush 7 closes the gap and is elastically deformed toward the expanded portion 5c of the rod guide 5, further preventing uneven contact and causing a large lateral load. Even in the past, it is possible to suppress the increase in wear due to uneven contact. Therefore, it is possible to reduce the static frictional resistance and the dynamic frictional resistance between these two parts, allowing the piston rod 4 to operate smoothly, improving the feeling during running, and stabilizing the damping force of the shock absorber. I can do it. Moreover, in the direction in which the piston rod swings are eliminated, the elastically deformed end of the guide bush also substantially returns to its original shape, and the reliable guiding function of the guide bush is restored. , the elasticity of the guide bush causes a force to return the piston rod to its original position. In this way, by providing the guide bush with an elastically deformable end that can be deformed in the radial outer circumference in the direction that closes the gap when the piston rod swings, an extremely excellent shock absorber can be provided.

In order to install the guide bush 7 into the inner circumferential surface 6 of the shaft portion of the rod guide 5, insert the guide bush 7 into the inner circumferential surface 6, and then align the outer circumferential surface of the guide bush 7 with the expanded portion 5c side of the rod guide 5. It is only necessary to press with enough force to leave elastic deformation, and therefore, it is possible to attach it while leaving a gap C. Furthermore, if the outer diameter of the guide bush 7 before insertion is set to be larger than the diameter of the center portion of the shaft inner peripheral surface 6 of the rod guide 5 with the smallest inner diameter by a predetermined amount or more, the guide bush 7 can be inserted without applying the pressing force. It is possible to install it within the inner circumferential surface 6 while leaving a gap 〓C.

The rod guide 5 may be made of aluminum die casting (e.g. ADC-12), aluminum casting (e.g. AC8A), aluminum forging, mechanical cutting from an aluminum drawn rod, sintering or forging of iron,
The guide bushing 7 can be manufactured from zinc or magnesium alloy, plastic, etc. On the other hand, the guide bushing 7 can be manufactured by impregnating polytetrafluoroethylene (PTFE) into a copper-based sintered layer sintered on the back metal. is desirable.

FIG. 3 shows test results showing the effects of the embodiment of the present application. This test was conducted using a shock absorber physical durability tester with a stroke of 60 mm and a frequency of 8 Hz.
This is the amount of wear measured after repeating 2 million times.

In Fig. 3, sample A is an embodiment of the present invention with a gap C of 30μ, sample B is a configuration of the present invention with a gap C of 0, and sample C has a guide bush with a straight inner peripheral surface. It shows what was done.

As is clear from the test results in the figure, Sample A, which is an example of the present invention, has a better effect than Samples B and C, which are comparative materials.

4 to 6 show essential parts of other embodiments of the present invention, and the embodiment shown in FIG. A portion 5c is provided, and a straight-shaped guide bush 7 is fitted onto the inner circumferential surface 6 of the portion 5c to provide a gap C. Note that the length of the guide bush 7 in the axial direction of the embodiment shown in FIG. 4 is shorter than the length of the rod guide 5 in the axial direction, and is fitted on the upper side of the rod guide 5.

With such a configuration, the load applied to the oil seal 8 is smaller than that of a conventional shock absorber, and there is less fear that the oil seal will wear out and lead to oil leakage.

In the embodiment shown in FIG. 5, the inner circumferential surface 6 of the rod guide 5 is straight, and only the outer circumferential surface of the upper end of the fitted guide bush 7 is reduced in diameter, thereby providing a gap C.

Incidentally, although the phenomenon of uneven contact of the piston rod 4 is noticeable at the upper end of the guide bush 7, it also occurs at the lower end. This is because the lower part of the piston rod 4 is supported by the guide bush 7 and the piston 3, so it is relatively easy to maintain its axial position, but the upper part of the piston rod 4 is substantially free and therefore curves. This is because it is easy to do.

In order to eliminate this uneven contact phenomenon at the lower end of the rod guide 5, a gap should be provided between the rod guide 5 and the guide bush 7 at the lower end in addition to or in addition to the configuration shown in FIG. 1. You can also do it.

In the embodiment shown in FIG. 6, an enlarged part 5c is provided on the inner peripheral surface of the upper end of the rod guide 5, which is wider than the inner diameter of the central part, and an enlarged part 5c is also provided on the inner peripheral surface of the upper end of the guide bush 7, which is wider than the inner diameter of the central part. The rod guide 5 is formed by making the opening 7c have an arcuate cross-section in the axial direction, setting the degree of expansion to be 5c>7c so that a gap C exists, and also providing an expanded portion 5c and an expanded portion 7c at the lower end.
A gap is provided between the guide bush 7 and the guide bush 7.

In addition, any shape may be used as long as the gap is set within a range that allows deformation of the end of the guide bush. In addition, also in the other embodiments shown in FIGS. 4 to 6 above, the guide bush is provided with an elastically deformable end at the end on the side where the gap C is provided.

"Effects of the Invention" According to the present invention, even when the piston rod swings relative to the rod guide and misalignment occurs, at least the upper inner circumferential surface of the stepped rod guide is connected to the outer circumference of the guide bush. Between 〓
is set, and the guide bush is provided with an elastically deformable end that can be deformed in the outer circumference in the radial direction in the direction of closing the gap when the piston rod swings, at the end on the side where the gap is provided. Therefore, the end of the guide bush can deform toward the rod guide side in response to excessive deformation of the piston rod, and as a result, the degree of uneven contact between the outer peripheral surface of the piston rod and the end of the guide bush decreases, and The effect is that wear can be significantly reduced. When the axial misalignment of the piston rod is reduced and the excessive deformation is released, the elastically deformed end of the guide bush substantially returns to its original shape due to its elasticity, which has the effect of maintaining good guiding function. In addition, the elasticity of the elastically deformed end of the guide bush has an auxiliary effect of returning the piston rod in a direction that eliminates deformation and axial misalignment.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of essential parts showing one embodiment of the present invention, FIG. 2 is a cross-sectional view of the entirety of FIG. 1, and FIG. 3 is a diagram showing test results for explaining the effects of the present invention. , and FIGS. 4 to 6 show essential parts of other embodiments of the present invention. 1...Cylinder, 2...Outer shell, 3...
... Piston, 4... Piston rod, 5... Rod guide, 5c... Large diameter part of rod guide, 7...
...Guide bush, 7a...Inner peripheral surface of guide bush, 7c...Large diameter portion of guide bush, 8...Oil seal, C...Gap.

Claims (1)

[Scope of Claims] 1. A cylinder with a smaller diameter is housed inside a larger diameter outer shell, and the outer shell is fitted onto the outer circumferential surface of the large diameter portion of a stepped rod guide, and the cylinder is fitted onto the outer circumferential surface of the small diameter portion of the stepped rod guide. By doing so, both are held concentrically, and a piston rod carrying a piston that slides in sliding contact with the cylinder inner circumferential surface near the inner end slides on the inner circumferential surface of the guide bush fitted to the inner circumferential surface of the rod guide. In the shock absorber that is movably inserted, a gap is set between at least an upper inner circumferential surface of the stepped rod guide and an outer circumference of the guide bush; 1. A shock absorber characterized in that an elastically deformable end part is provided on the end part on the side where the piston rod is provided with an elastically deformable end part that can be deformed in the outer circumference in the radial direction, which is the direction in which the gap is narrowed when the piston rod swings.