JPS6152438A - Shock absorber - Google Patents

Abstract

PURPOSE:To decrease sliding resistance by forming taper portions on both end portions in the sliding direction of a synthetic resin layer disposed on the outer peripheral surface of a piston, whereby even if lateral load is imposed upon the piston to elastically deform the synthetic resin layer, oil is always guided to the sliding surface. CONSTITUTION:A synthetic resin layer 13 disposed on the outer peripheral surface of a piston 3 has a thickness of about 0.4mm. and more to secure temperature compensating effect. Both end portions in the sliding direction of the synthetic resin layer 13 are formed to be tapered at an angle of about 2-25 deg. in such a manner that even if lateral load is imposed upon the piston 3 to elastically deform the synthetic resin layer 13, oil is always guided to the sliding surface favorably. The axial width of the tapered portions 13b is about 1mm. and more.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shock absorber used in automobiles and the like, and more particularly to a shock absorber having a piston provided with a synthetic resin layer.

[Prior Art] Conventionally, a shock absorber includes a piston fitted into a cylinder and a synthetic resin layer provided on the outer circumferential surface of the piston, and the synthetic resin layer is brought into sliding contact with the inner circumferential surface of the cylinder. It is known what has been done. The synthetic resin layer is generally used to reduce sliding resistance, but is also used to compensate for changes in shock absorber performance due to changes in oil viscosity.

In other words, the viscosity of the oil sealed in the shock absorber decreases as the temperature increases, so the damping force of the shock absorber decreases as the temperature increases. On the other hand,
Since the coefficient of thermal expansion of the synthetic resin layer is quite large, the clearance between this synthetic resin layer and the inner peripheral surface of the cylinder decreases as the temperature increases, and as a result, at high temperatures when the viscosity of the oil decreases, the above clearance decreases. This reduces the amount of oil flowing in that area, and prevents the damping force from decreasing.

[Problems to be Solved by the Invention] However, in order to obtain the above-mentioned temperature compensation effect with the synthetic resin layer, a certain thickness of 0 degrees is required, and moreover, the synthetic resin layer and the outer circumferential surface of the piston need to have a thickness of 0 degrees. It is desirable that the synthetic resin layer is not bonded and can freely thermally expand. For example, in the case of a piston whose outer peripheral surface is coated with synthetic resin, its thickness is generally as thin as 0.001 = 0.21, and the material is also glued to the outer peripheral surface of the piston, so sufficient thermal expansion cannot be expected. It becomes difficult to obtain a temperature compensation effect.

In this way, in order to obtain a sufficient temperature compensation effect, the thickness of the synthetic resin layer needs to be approximately 0.4 m + m or more, but conventional shocks with a synthetic resin layer thickness within this range It has been found that the absorber has extremely little effect in reducing sliding resistance, especially when a lateral load, that is, a radial load is applied to the piston.

As a result of conducting various experiments to find out the cause of this problem, we found that conventional synthetic resin layers usually have a circular arc section at the end of the width Ff in the sliding direction, and the arc section is used to transfer oil between the synthetic resin layer and the cylinder. However, as mentioned above, if the thickness of the synthetic resin layer is about 0.41 or more, the synthetic resin layer will elastically deform when the above lateral load is applied. It was found that both ends of the cylinder were deformed into a rectangular shape, which obstructed the smooth introduction of oil to the sliding surface and increased sliding resistance.

[Means and effects for solving the problems] In view of the above circumstances, the present invention provides a shock absorber in which the thickness of the synthetic resin layer is set to approximately 0.4 mm or more, thereby making it possible to obtain a temperature compensation effect. By forming both ends of the synthetic resin layer in the sliding direction into a tapered shape with an angle of about 2 to 25 degrees, and at the same time making the axial width of the tapered part 1 mm or more, a lateral load is applied to the piston. To provide a shock absorber that constantly guides oil to a sliding surface to reduce sliding resistance even when a synthetic resin layer is elastically deformed.

[Example] The present invention will be described below with reference to the illustrated example. In the IF diagram, 1 is a cylinder of a shock absorber used for a front suspension etc., 2 is a piston rod,
A piston 3 made of sintered metal is integrally connected to the piston rod 2 by a nut 4. A plurality of axial passages 5 are formed concentrically on the outer circumference of the piston 3 to communicate between the upper and lower sides of the piston 3, and a ring-shaped valve body 6 whose upper end opening is in elastic contact with the upper surface of the piston 3 It is possible to close it with The valve body 6 is brought into elastic contact with the piston 3 by a spring 8 loaded between the valve body 6 and a support member 7, and the support member 7 is sandwiched between the stepped portion of the piston rod 2 and the piston 3. There is.

Also, a plurality of axial passages 9 are provided in the inner circumference of the piston 3.
are formed concentrically, and the upper and lower sides of the piston 3 are communicated via the passage 9 and a through hole IO formed in the valve body 6. The lower end opening of each passage 9 can be closed by a ring-shaped valve body 11 which is brought into elastic contact with the lower surface of the piston 3, and this valve body 11 is supported by a spring 12 mounted between the valve body 11 and the nut 4. It is intended to be biased upward.

Further, a synthetic resin layer 13 is provided on the outer circumferential surface of the piston 3, and this synthetic resin layer 13 has a roughly U-shaped cross section, and its both ends 13a are fitted into stepped portions 3a provided at upper and lower positions on the outer circumferential surface of the piston 3. In addition, the synthetic resin layer 13 forms the piston 3.
This prevents it from falling off. The thickness t of the synthetic resin layer 13 is set to about Q, 41001 or more to ensure the above-mentioned temperature compensation effect, and both ends of the synthetic resin layer 13 in the sliding direction are tapered at an angle of about 2 to 25 degrees. By forming the tapered portion 13b into a shape and making the axial width of the tapered portion 13b approximately lam or more, even if a lateral load is applied to the piston 3 and the synthetic resin layer 13 is elastically deformed, oil can always be well applied to the sliding surface. I will be able to guide you.

If the angle of the tapered portion 13b is too small or too large, a good oil guiding effect cannot be expected, and it is affected by the hardness of the synthetic resin layer 13, but in general, a good oil guiding effect cannot be expected. In order to expect a guidance effect, it is necessary to set it within the above-mentioned range. Furthermore, when setting the angle and width in the other direction of the tapered portion 13b, it is desirable that the smaller the angle, the larger the width in the axial direction.As a more preferable range, the angle of the tapered portion 13b is 3 to 20 degrees. , the thickness of the synthetic resin layer is
It is 0.8llll11-3mff1.

In the above configuration, when the piston 3 descends, oil below the piston pushes open the valve body 6 against the spring 8 and flows upward through the piston 5, and when the piston 3 ascends, the oil above the piston pushes open the valve body 6 against the spring 8. 12, the valve body 11 is pushed open, and the liquid begins to flow downward through the through hole IO and the passage 9.
The orifice effect of these passages 5.9 generates a damping force in the shock absorber.

The synthetic resin layer 13 has a sufficiently thick thickness,
Furthermore, since it is fitted and supported by the piston 3 without adhesion by its both ends 13a, it can freely expand thermally, and as a result, there is a large gap between the synthetic resin layer 13 and the cylinder l at room temperature when the viscosity of the oil is high. It is possible to secure a large flow path area for oil by ensuring clearance, and since the clearance becomes smaller at high temperatures, it is possible to compensate for the decrease in damping force due to the decrease in oil viscosity. .

Further, when a lateral load is applied to the piston 3, a part of the synthetic resin layer 13 is pressed against the cylinder l and is shaped by the cylinder l. 1m
Since the tapered portion 13b is formed with a diameter of m or more, even if the synthetic resin layer I3 is elastically deformed, both ends of the tapered portion 13b will maintain their shape, allowing the oil to smoothly flow into the synthetic resin layer 13. It can be introduced between the cylinder 1 and the cylinder 1 to prevent an increase in sliding resistance.

Next, the effects of the present invention will be explained based on the experimental results shown in FIG. In this experiment, a synthetic resin layer 13 with a thickness of 0°8+am having the above-mentioned structure was provided on the piston 3 of an actual shock absorber, and the sliding resistance of the piston 3 was measured with a lateral load of 50 kg applied to the piston 3. This is what I did.

In Fig. 2, A is a product of the present invention in which tapered portions 13b are provided at both ends of the synthetic resin layer 13, B is a conventional product in which both ends are arcuate, and C is a conventional product in which both ends are corner portions. In this experiment, the angle of the tapered portion 13b is 10 degrees,
The axial width is 2II11, and the radius of the arc portion is 0.
．． It is set as 5+++m. Furthermore, the white bar graph in Figure 2 shows the maximum piston speed of 0.003 m/sac.
The shaded bar graph indicates piston speed up to 0.
．． 3m/Sec.

As shown in the experimental results in Fig. 2, product A of the present invention obtained better results than conventional products B and C even when subjected to lateral loads, and the effect of providing the tapered portion 13b was Is recognized. Conventional product B, which has arcuate ends at both ends, and conventional product C, which has corner ends at both ends, have the same results.
From this, it is understood that when the arcuate portion receives a lateral load, it elastically deforms and essentially becomes a corner portion.

The relationship between piston speed and sliding resistance in product A of the present invention is as shown in FIG. 3, and the higher the piston speed, the smaller the sliding resistance. This taper part increases as the piston speed increases! 3
This is thought to be because the oil guiding effect by b increases.

In addition, in the above conventional product B, it is clear that when the radius of the circular arc portion is made small, it becomes a corner portion due to the above-mentioned unilateral deformation, and on the other hand, when the radius of the circular arc portion is made large, the circular arc portion remains even if it is elastically deformed. However, the angle of the arcuate portion with respect to the cylinder 1 becomes too large, and in the end, the arcuate portion cannot provide a good oil guiding effect.

Next, FIG. 4 shows another embodiment of the present invention. In this embodiment, two annular grooves 21 are formed on the outer peripheral surface of the piston 20, and two annular grooves 21 are formed on the inner peripheral surface of the synthetic resin layer 22. An annular rib 23 is formed to fit into the annular groove 21, and the synthetic resin layer 22 can be attached to the piston 20 without adhesive. It goes without saying that the synthetic resin layer 22 is provided at both ends with tapered portions 22a corresponding to the tapered portions 13b described above.

It is clear that even in such a configuration, the same effects as those of the above embodiment can be obtained.

[Effects of the Invention] As described above, the present invention includes a piston fitted in a cylinder and a synthetic resin layer having a thickness of about 0.4 mm or more provided on the outer circumferential surface of the piston. In a shock absorber in which a synthetic resin layer is in sliding contact with the inner peripheral surface of a cylinder, both ends of the synthetic resin layer in the sliding direction are formed into a tapered shape with an angle of approximately 2 to 25 degrees, and the tapered portion is tapered in the axial direction. Since the width is approximately 1 mm or more, it is possible to ensure a temperature compensation effect, and at the same time, even when a lateral load is applied to the piston and the synthetic resin layer is elastically deformed, oil is always guided to the sliding surface. The effect is that sliding resistance can be reduced.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, Figure 2 is a diagram showing the experimental results of measuring the magnitude of sliding resistance for a product of the present invention and a conventional product, and Figure 3 is a diagram of the product of the present invention. FIG. 4 is a diagram showing the relationship between piston speed and sliding resistance, and FIG. 4 is a sectional view of a main part showing another embodiment of the present invention. 1...Cylinder 2...Piston rod 3
．． 20...Piston 13.22...Synthetic resin layer 13b, 22a...Tapered portion Fig. 1 Fig. 4

Claims (1)

[Claims] A shock comprising a piston fitted into a cylinder and a synthetic resin layer with a thickness of approximately 0.4 mm or more provided on the outer circumferential surface of the piston, the synthetic resin layer being in sliding contact with the inner circumferential surface of the cylinder. A shock absorber characterized in that both ends of the synthetic resin layer in the sliding direction are tapered at an angle of about 2 to 25 degrees, and the width of the tapered part in the axial direction is about 1 mm or more.