JPS61136031A - Shock absorber - Google Patents

Abstract

PURPOSE:To greatly reduce abration due to ununiform contact, by forming the inner peripheral surface of a rod guide hole for a piston rod, in a barrel shape to prevent the piston rod from making into ununiform contact with the end section of the rod guide. CONSTITUTION:The inner peripheral surface of a hole 6 formed in a rod guide 5 has a barrel shape having a smaller inner diameter in its center section while having a large inner diameter in its end sections, and a guide bushing 6 is formed in a shapecorresponding to the shape of the inner peripheral surface of the hole 6. The barrel shape slide surface of the guide bushing 7 may be always made into smooth contact with the outer peripheral surface of a piston rod 4 even if the piston rod 4 swings relative to the guide bushing 7.

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 a vehicle such as an automobile.

``Prior Art'' Conventionally, the large diameter portion of a stepped rod guide is fitted into an outer shell, and the small diameter portion of the stepped rod guide is fitted into a cylinder provided within the outer shell and slides into the cylinder. A shock absorber in which a piston rod of a movably fitted piston is slidably inserted into a hole in the rod guide shaft portion is well known.

``Problem to be solved by the invention'' This type of shock absorber, especially for automobiles, is usually installed in an inclined position, so the piston rod is inclined with respect to the cylinder while the automobile is running. When the piston rod bends or bends, the end of the rod guide comes into partial contact due to the misalignment of the axis between the piston rod and the rod guide. If the piston rod and the rod guide make uneven contact, the lubrication between the two deteriorates and the durability of the rod guide decreases.Furthermore, the frictional resistance of the rod guide, especially the static frictional resistance, increases, which reduces the damping force of the shock absorber. It also has the disadvantage of being unstable. This drawback is particularly noticeable when the wheels run over uneven road surfaces.

``Means for Solving the Problems'' In view of the circumstances, the present invention provides an annular protrusion that surrounds the hole and forms an annular protrusion on at least the large-diameter side of the rod guide, so that the outer circumferential surface of the annular protrusion is In addition to being separated from the outside, the inner circumferential surface of the hole is formed into a drum shape with a smaller inner diameter at the center and larger inner diameters at both ends.

"Operation" According to such a configuration, even if the piston inner pin swings relative to the rod guide and misalignment occurs,
Since the inner circumferential surface of the hole is shaped like a drum, the degree of uneven contact between the outer circumferential surface of the piston rod and the end of the rod guide is reduced.

At the same time, in the event that the outer circumferential surface of the piston rod and the large-diameter end of the rod guide come into strong pressure contact even though the inner circumferential surface of the hole is shaped like a drum, The annular protrusion is elastically deformed outward by the pressure contact force, reducing the pressure contact force between it and the piston rod. This, combined with the fact that the inner peripheral surface of the hole is shaped like a drum, reduces wear due to uneven contact. can be significantly reduced.

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

A stepped rod guide 5 is provided at the upper end of the outer shell 2.
The 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 bushing 7 is fitted into a hole 6 formed in the shaft portion of the rod guide 5, and the piston rod 4 is
A gasket 8 that slidably passes through the guide bookure and at the same time seals the upper end opening of the outer shell 2.
is slidably penetrated and protruded to the outside.

Further, an outer cylinder 9 is attached to the upper end of the piston rod 4 to cover the gasket 8 portion.

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

Such a configuration is basically the same as conventionally known ones, 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 has a damping effect based on the viscous resistance of this oil.

However, as shown in an enlarged view in FIG. 1, the inner peripheral surface of the hole 6 formed in the rod guide 5 is shaped like a drum, with a smaller inner diameter at the center and larger inner diameters at both ends. The guide bush 7 is also formed in a drum shape, corresponding to the inner peripheral surface of the hole 6, with a smaller inner diameter at the center and larger inner diameters at both ends. The sliding surface of such a drum-shaped guide bujua is
Even when the piston rod 4 swings relative to the guide guide, it always comes into smooth sliding contact with the outer peripheral surface of the piston rod 4.

In order to install the guide bush 7 in the hole 6, it is sufficient to insert the guide bush 7 into the hole 6 and then size the guide bush 7 so that the outer circumferential surface of the guide bush 7 comes into close contact with the inner wall surface of the hole 6. The guide bush 7 is plastically deformed so that its outer circumferential surface and inner circumferential sliding surface are formed into a shape corresponding to the inner wall surface of the hole 6, that is, a drum shape having an arc-shaped axial cross section.

In this case, it is desirable that the outer diameter of the guide bushing 7 before insertion be set equal to or slightly larger than the diameter of the smallest center part of the inner diameter of the hole 6, and If the diameter of the guide bushing 7 is set at least a predetermined amount larger than the inner diameter of the hole 6, the guide bushing 7 can be made to follow the shape of the inner circumferential surface of the hole 6 by simply press-fitting the guide bushing 7 into the hole 6 without sizing. It is possible.

Note that the amount of bulge of the central portion of the hole 6 with respect to both ends is as follows:
If the axial length of the guide bookure is 20 mm, lO
It is desirable to set it so that it bulges inward by about 1100 JL. 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, zinc or magnesium alloy, or The guide bushing 7 can be made of plastic or the like, and it is preferable that the guide bushing 7 is made by impregnating polytetrafluoroethylene (PTFE) into a copper-based sintered layer sintered on a backing metal.

Furthermore, in this embodiment, - the mouth/end guide 5
An annular protruding portion 5c surrounding the hole 6 is provided on the large diameter portion 5a side of the
The annular protrusion 5c is formed to protrude so that its outer peripheral surface is separated from the outside, so that the annular protrusion 5c can be elastically deformed relatively easily. Naturally, the wall thickness of this annular protrusion 5C is the same as that of the rod guide 5.
For example, 2 mm is appropriate for iron-based sintered metal, but for aluminum or FRP
If the film is manufactured using, for example, it is necessary to make it even thicker. Such thickness can be determined by simple preliminary experiments.

According to the above configuration, even if the piston rod 4 swings relative to the guide budua and axial misalignment occurs, -
1- Since the inner circumferential surface of the hole 6 is drum-shaped, it is possible to effectively prevent uneven contact between the outer circumferential surface of the piston rod 4 and the end of the guide budua. In addition, if the outer circumferential surface of the piston rod 4 and the upper end of the guide guide are strongly pressed against each other even though the inner circumferential surface of the two piping holes 6 is shaped like a drum, the annular protrusion may occur due to the pressure force. Since the portion 5C is elastically deformed in the long direction to reduce the pressing force between the piston rod 4 and the piston rod 4, wear caused by uneven contact can be significantly reduced.

Further, the drum-shaped inner peripheral surface of the hole 6 is connected to the piston rod 4.
A wedge shape is formed between the two, and this wedge effect facilitates the formation of an oil film, resulting in very good lubrication. Therefore, the static+1-frictional resistance and the dynamic frictional resistance between these two components can be reduced to allow the piston rod 4 to operate smoothly, resulting in a better feeling during driving and stabilizing the damping force of the shock absorber. be able to.

Furthermore, since the guide bushing 7 has a drum-shaped shape that is in close contact with the inner wall surface of the drum-shaped hole 6, the force with which the rod guide 5 holds the guide bushing is applied to the cylinder inside the simple cylindrical hole as in the conventional case. This is much larger than when a guide bushing with a shape is press-fitted, and as a result, the load when removing the guide bushing increases, which improves the durability of the guide bushing and improves the durability and safety of the shock absorber. become able to.

Incidentally, although the phenomenon of uneven contact of the piston rod 4 also occurs at the lower end of the guide bushing, it is more noticeable at the upper end of the guide bushing 7. 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. This is because it is easily curved.

Therefore, most of the uneven contact phenomenon can be eliminated simply by forming the annular protrusion 5c in the upper part of the rod guide 5, but in order to completely eliminate the uneven contact phenomenon in the lower part of the rod guide 5, As shown in FIG. 3, it is clear that an annular protrusion 5d may be formed to surround the cylindrical hole 6 and whose outer peripheral surface is spaced apart from the outside.

In addition, in the embodiment shown in FIG. 3, the guide budua is omitted and the piston rod 4 is brought into direct sliding contact with the inner circumferential surface of the hole 6 having the shape of a drum. It has a drum shape in which the center part bulges out from both ends.

Therefore, in this embodiment, the same effect as in the above embodiment can be obtained by the drum-shaped inner circumferential surface of the hole 6 and the upper and lower annular protrusions 5c and 5d, and the rod guide is provided by the drum-shaped large diameter part 5a. Since the piston rod 5 itself can be tilted in the direction of the load, the pressure contact force with the piston rod 4 can be further reduced.

Next, although the effect of reducing wear due to uneven contact can be achieved by forming the guide beadure into a drum shape or by providing the annular protrusion 5c, the effect of reducing the wear due to uneven contact can be achieved even more by combining the two. A synergistic effect can be expected.

FIG. 4 shows test results showing such an effect. This test tested shock absorbers with built-in guide bushes.
It was operated 2 million times at a load of 250 kg, a stroke of 50 mm, and 3 times per second, and the friction force before and after the test was measured to determine the amount of increase in the friction force. Note that the frictional force described in "-" was measured when operating at a load of 250 kg, a stroke of 10 mm, and a rate of 0.05 times per second.

In FIG. 4, sample A is the one according to the present invention, and sample B is the one in which the annular protrusion is omitted and the guide bush is formed into a drum shape.
Sample C has an annular protrusion formed and the guide bush has a simple cylindrical shape, and sample C has an annular protrusion formed and the guide bush has a simple cylindrical shape. There is.

As is clear from the test results in the same figure, better results were obtained for sample B with the guide bush shaped like a drum and sample C with an annular protrusion than with the conventional sample. In sample A according to the present invention, a far superior effect was obtained than those obtained alone.

In the above example, the drum shape is formed so that the axial cross section is arcuate, but other shapes may be used, for example, where the center part is cylindrical and both ends are tapered, and the cylindrical part and the tapered part are smoothly continuous. In other words, it is sufficient as long as it has a drum shape as a whole.

"Effects of the Invention" As described above, according to the present invention, it is possible to obtain the effect that wear caused by uneven contact can be significantly reduced.

[Brief explanation of the drawing]

1 is a cross-sectional view of essential parts showing one embodiment of the present invention, FIG. 2 is a cross-sectional view showing the entirety of FIG. 1, FIG. 3 is a cross-sectional view showing another embodiment of the present invention, The figure is a diagram showing test results for explaining the present invention in detail. 1...Cylinder 2...Outer shell 3.
...Piston 4...Piston port/end 5...
・Rod guide 5a... Large diameter part 5b... Small diameter part 5C15d... Annular protrusion 6... Hole
7...Guide bushing Figure 3 Figure 4 A'B CD Procedural amendment (voluntary) January 7, 1985

Claims (1)

[Claims] A piston in which a large diameter portion of a stepped rod guide is fitted into an outer shell, a small diameter portion of the rod guide is fitted into a cylinder provided within the outer shell, and the piston is slidably fitted into the cylinder. In a shock absorber in which a rod is slidably passed through a hole in the rod guide shaft portion, an annular protrusion surrounding the hole is formed protrudingly at least on the large diameter side of the rod guide, and the outer peripheral surface thereof A shock absorber characterized in that the inner circumferential surface of the hole is formed in the shape of a drum with a smaller inner diameter at the center and larger inner diameters at both ends.