JPS61248933A - Shock absorber - Google Patents

Abstract

PURPOSE:To suppress the flow of oil in the leaking direction between a piston rod and a rod guide by providing an expanded diameter section so as to form a gap with the piston rod at the lower portion of the rod guide. CONSTITUTION:The lower portion of a rod guide 5 is expanded so as to form a gap C with the outer periphery of a piston rod 4 over the whole circumference. The flow of oil in a cylinder 1 in the leaking direction between the piston rod 4 and rod guide 5 is suppressed due to this gap C. Accordingly, oil is prevented from flowing into grease filled in an oil seal 8, thus the deterioration and abrasion of the oil seal 8 can be prevented.

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, a stepped rod guide has a large diameter portion fitted into an outer shell and a small diameter portion fitted into a cylinder provided within the outer shell, and an oil seal provided on the top of the rod guide. a piston rod of a piston that is slidably fitted into the cylinder is slidably inserted into the shaft hole of the rod guide and oil seal, and the inner periphery of the hole provided in the rod guide shaft is Shock absorbers having straight surfaces are well known.

``Problems to be Solved by the Invention'' This type of shock absorber generally has a structure shown in FIG. 2. That is, the lower end of the outer shell 2 housing the cylinder 1 therein is connected to a wheel (not shown), and the piston rod 4 of the piston 3 slidably fitted into the cylinder 1 has its upper end connected to the vehicle body. Connected to the side.

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, connect the rod guide 5 to the piston rod 4.
At the same time, an oil seal 8 that seals the upper end opening of the outer shell 2 is slidably passed through the outer shell 2 and protrudes 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 the gap between the cylinder 1 and the outer shell 2 is used as a reservoir 11.

In such a configuration, when the cylinder 1 is moved forward or backward, the oil in the cylinder 1 flows into the valve 1 inside the piston.
0 to allow relative movement between the piston rod 4 and the cylinder 1, and also provide a damping effect based on the viscous resistance of this oil. Oil in the cylinder 1 leaks from between the piston rod 4 and rod guide 5 when traveling at high speed.

There is a problem in that the grease filled in the oil seal 8 is washed away, leading to deterioration and wear of the oil seal 8, which makes the damping force of the shock absorber unstable.

In view of these circumstances, the present invention provides a stepped rod guide in which a large diameter portion is fitted into an outer shell, and a small diameter portion is fitted into a cylinder provided within the outer shell. and an oil seal provided at the upper part of the rod guide, the piston rod of the piston being slidably fitted into the cylinder being slidably penetrated through the inner peripheral surface of the shaft portion of the rod guide and the oil seal. In the shock absorber.

The inner diameter of the lower portion of the small diameter portion of the rod guide is made large, thereby forming a gap over the entire circumference between the inner circumferential surface of the portion of the rod guide and the outer curved surface of the piston rod. Achieved by shock absorbers.

"Operation" According to the configuration of the present invention, the inner diameter of the lower part of the small diameter part of the rod guide is made large, so that the entire circumference is between the inner circumferential surface of this part of the rod guide and the outer circumferential surface of the piston rod. Since a gap is formed across the cylinder, the flow of oil in the cylinder in the direction of leakage from between the piston rod and the rod guide is suppressed, preventing the grease filled in the oil seal from flowing out and preventing deterioration and wear of the oil seal. can be prevented and, therefore, the function of the shock absorber can be maintained.

[Example" The present invention will be described below with reference to the illustrated embodiments.

In FIG. 1, 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. . Then, a guide bushing 7 is fitted into the inner peripheral surface 6 of the shaft portion of the rod guide 5, and the piston rod 4 is slidably passed through the inner peripheral surface 7a of the guide bushing 7, and at the same time, the upper end opening of the outer shell 2 is opened. An oil seal 8 that seals the part is slidably penetrated and protruded to the outside.

However, since the axial length of the guide bushing 7 is set shorter than the axial length of the rod guide 5, there is a gap between the inner circumferential surface of the rod guide 5 and the outer circumferential surface of the piston rod 4 over the entire circumference. A gap C is formed throughout.

The gap C was set at 1.5 mm, but it was set at 0.5-3 mm.
is appropriate. Further, the axial length of the guide bushing 7 was set to be 5 m shorter than the axial length of the rod guide 5, but a suitable length is 1 to 10 m++.

In any case, the difference in the length of the gap C and the guide bushing 7 reduces the oil pressure generated when the cylinder 1 and the outer shell 2 descend, and the difference in the length of the gap C and the guide bushing 7 reduces the oil pressure generated when the cylinder 1 and the outer shell 2 descend. It should be set so that the flow velocity can be reduced.

In the embodiment shown in FIG. 1, the guide bushing 7 is fitted into the inner circumferential surface 6 of the shaft portion of the rod guide 5. Of course, the inner diameter of the piston rod 4 may be made large, thereby forming a gap C over the entire circumference between the inner circumferential surface of this portion of the rod guide 5 and the outer circumferential surface of the piston rod 4.

Next, another embodiment of the present invention will be described based on FIG. In addition to the embodiment shown in FIG. 1, the embodiment shown in FIG. An expanded portion 7c is provided that is expanded from the inner diameter of the central portion, and the expanded portion 5c of the rod guide 5 and the expanded portion 7 of the guide bush 7 are provided.
There is a gap between C and C.

Generally, this gap is desirably 1 to 300μ, and 30μ
Although a range of ~60μ is more desirable, it should be set within a range in which the expanded portion 7c of the guide bush 7 is elastically deformed.

The deformation is preferably elastic deformation, but may include some plastic deformation, or may include oil, grease, or an elastic body in the gap.

In the above configuration, when there is one gap, an oil film is likely to be formed between the expanded portion 7c of the guide bushing 7 and the piston rod 4, so the lubrication state is good. For the upper end of the rod guide 5, where uneven contact is particularly noticeable when the rod guide 5 swings
It comes into smooth sliding contact with the outer peripheral surface of the piston rod 4. Furthermore, when the piston rod 4 swings greatly, the widened part 7c of the guide bushing 7 closes the gap and is elastically deformed toward the widened part 5c of the rod guide 5, further preventing uneven contact and reducing large lateral loads. Even if it is applied, it is possible to prevent an increase in wear due to uneven contact.

Therefore, in the embodiment shown in FIG. 3, the flow of oil in the cylinder 1 in the direction in which it leaks from between the piston rod 4 and the guide bush 7 is suppressed.

It is possible to prevent deterioration and wear of the oil seal without causing the grease filled in the oil seal 8 to flow out, and to reduce the static frictional resistance and dynamic frictional resistance between the piston rod 4 and the guide bushing 7, so that the piston Since the rod 4 can be moved smoothly, the driving feeling is improved, and the damping force of the shock absorber can be stabilized.

In the above embodiment, an expanded portion 5C1 on the inner peripheral surface of the upper end of the rod guide 5 that expands from the inner diameter of the central portion, and an expanded portion 7c that expands from the inner diameter of the central portion on the inner peripheral surface of the upper end of the guide bush 7. The axial cross section is arcuate to create a gap, but in addition, for example, the upper end is tapered, the lower end is cylindrical, and the space between them is smoothly continuous, and the inner peripheral surface 6 is made into a cylindrical shape. The guide bush 7 may be fitted with a straight-shaped guide bush 7, or only the outer peripheral surface of the upper end of the fitted guide bush 7 may be reduced in diameter to provide a gap.

Further, 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. On the other hand, the guide bushing 7 can be made of polytetrafluoroethylene (P) on a copper-based sintered layer sintered on the back metal.
Preferably, the material is impregnated with a material containing TFE).

Next, the present invention will be explained in detail. Using a shock absorber physical durability testing machine as a testing machine, the oil seal after 2 million repetitions with a lateral load of 300 kg, a stroke of 0 + am, and a frequency of 10.6 Hz is compared to III. The conventional product shown in Figure 2 has almost no grease. In contrast, in the product of the present invention shown in FIG. 1, almost no grease remained without flowing out. Further, when the amount of wear after the test under the same conditions was measured, the conventional product shown in FIG. 2 had a wear amount of 60μ, while the product of the present invention shown in FIG. 3 had an excellent effect of 25μ.

"Effects of the Invention" The invention makes the inner diameter of the lower part of the small diameter part of the rod guide larger, thereby creating a gap over the entire circumference between the inner peripheral surface of this part of the rod guide and the outer peripheral surface of the piston rod. This prevents the oil in the cylinder from flowing in the direction of leakage from between the piston rod and rod guide, preventing the grease filled in the oil seal from escaping and preventing deterioration and wear of the oil seal. It is possible,
Therefore, it is possible to maintain the function of the shock absorber.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of essential parts showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the entire conventional shock absorber, and FIG.
The figure is a sectional view of essential parts showing another embodiment of the present invention. 1...Cylinder 2...Outer shell 3...
・Piston 4...Piston rod 5...Rod guide 5c...Large diameter part 6...Inner peripheral surface of the rod guide 5b...Small diameter part 7 of the rod guide...
Guide bush 7a... Inner peripheral surface 8 of guide bush...
·Oil seal

Claims (1)

[Claims] A stepped rod guide having a large diameter part fitted into the outer shell and a small diameter part fitted into a cylinder provided in the outer shell, and an oil seal provided on the upper part of the rod guide, the stepped rod guide being slidable into the cylinder. In a shock absorber in which a piston rod of a movably fitted piston is slidably penetrated through an inner peripheral surface of a shaft portion of the rod guide and an oil seal, an inner diameter of a lower portion of a small diameter portion of the rod guide is made a large diameter. A shock absorber characterized in that a gap is formed over the entire circumference between the inner circumferential surface of the portion of the rod guide and the outer circumferential surface of the piston rod.