JPS6152437A - Shock absorber - Google Patents

Abstract

PURPOSE:To effectively prevent noise and vibration and to attain effective temperature compensating action by providing a synthetic resin layer on the outer peripheral surface of a piston, which comprises portions which are brought into sliding contact with the inner peripheral surface of a cylinder at the normal temperature and portions which are separated from the inner peripheral surface of the cylinder at the normal temperature. CONSTITUTION:The thickness (t) of a synthetic resin layer 5 disposed on the outer peripheral surface of a piston 3 is uniform, and the outer peripheral surface of the cylinder resin layer 5 is substantially quadrilateral. Four corners of the substantial quadrilateral are formed in a circular-arc to construct portions 5a brought into sliding contact with the inner peripheral surface of a cylinder 1, and the other portions thereof construct separate portions 5b separated from the inner peripheral surface of the cylinder 1. Thermal expansion is larger in the peripheral direction, and the thermal expansion is consumed by clearances at the separate portions 5b. Accordingly, at the sliding portions 5a, thermal expansion in direction of thickness (t) may be considered, so that the clearances can be reduced to reliably prevent vibration and noise.

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.

That is, 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 conventional shock absorbers, a circular piston is fitted into a circular cylinder and a circular synthetic resin layer is provided on the outer peripheral surface of the piston. In consideration of the thermal expansion of the layer, it is necessary to provide a large clearance at room temperature, and the large clearance may cause vibration and noise.

Furthermore, even when a synthetic resin layer is used for the purpose of temperature compensation mentioned above, at least the above-mentioned clearance must be kept so that the piston does not stick at high temperatures, so that it does not become so large as to cause vibration or noise at room temperature. It is necessary to take care to ensure that the temperature compensation effect does not occur, and it is necessary to have a temperature compensation effect within that range, so there is little freedom in setting the above clearance, and depending on the shock absorber, it may not be possible to obtain the required temperature compensation effect. There were drawbacks.

[Means for Solving the Problems] The present invention focuses on the fact that the synthetic resin layer provided on the piston expands greatly in the circumferential direction, but only slightly in the thickness direction. It was done by
By providing the synthetic resin layer with a sliding portion that is close to and in sliding contact with the inner circumferential surface of the cylinder at least at room temperature, and a separate portion that is separated from the inner circumferential surface of the cylinder, noise and vibration can be reduced at room temperature. To provide a shock absorber that does not generate shock and can achieve effective temperature compensation.

[Embodiment] The present invention will be described below with reference to the illustrated embodiment. In Fig. 1, 1 is a cylinder of a shock absorber used for a front suspension system, 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, and a synthetic resin layer 5 is provided on the outer peripheral surface of the piston 3.

In this embodiment, the piston 5 is formed into a roughly rectangular shape as shown exaggeratedly in FIG. 2, and the thickness t of the synthetic resin layer 5 provided on the outer peripheral surface of the piston 3 is uniform. As such, the outer circumferential surface of the synthetic resin layer 5 is also approximately square. The four corners of this roughly square synthetic resin layer 5 are formed in an arc shape along the inner circumferential surface of the piston 5, so that the synthetic resin layer 5 is close to the inner circumferential surface of the cylinder 1 at least at room temperature. An arc-shaped sliding contact portion 5a that slides thereon and a separation portion 5b that is spaced apart from the inner circumferential surface of the cylinder l are provided.

According to such a configuration, the thermal expansion of the synthetic resin layer 5 is large in the circumferential direction, and the thermal expansion is consumed by narrowing the clearance of the separation portion 5b, so that the thickness L in the sliding contact portion 5a is large. It is only necessary to consider the thermal expansion in the direction, so the amount of variation in the clearance at the sliding contact portion 5a is small, and the above-mentioned clearance at room temperature can be made much smaller than in the past. Vibration and noise can be reliably prevented. −
For example, while the conventional device required a clearance of about 100 gm at room temperature, the device of this embodiment was able to reduce the clearance to about IQgm.

Furthermore, at room temperature when the viscosity of the oil is high, a large clearance can be ensured in the separated portion 5b to ensure a large flow path surface of the oil, and at high temperatures, the oil can be moved in the cylinder direction (radial direction) due to thermal expansion in the circumferential direction. The spread of the sliding contact portion 5a
As a result, the synthetic resin layer bulges in the radial direction at the separated portion 5b, which reduces the clearance of the separated portion 5b, thereby compensating for the decrease in damping force due to the decrease in oil viscosity. Moreover, the size of the clearance of the separated portion 5b is such that there is no need to consider the generation of vibrations and noise at room temperature and stickiness at high temperatures at the same time as in the conventional case, and at least the size of the clearance is such that it does not cause stickiness at high temperatures. Since it is only necessary to consider the clearance, it is possible to set the size of the clearance much more freely than in the past, and therefore it is possible to have a more effective temperature compensation effect than in the past. .

In the above embodiment, the shapes of the piston 3 and the synthetic resin layer 5 are approximately square, but the shapes may be changed to a triangle, an ellipse, a half-moon, or a pentagon, taking into consideration the size of the clearance in the separated portion 5b. It can be made into an appropriate shape such as the above polygon. At this time, the separation part is 1 to 3000 JLm, preferably 10 to 3000 JLm, relative to the sliding part.
5004m more preferably 100-2007pm
If the distance is too small, the desired effect will not be obtained, and if it is too large, the damping force will be reduced.

Furthermore, the piston 3 may be circular and the outer peripheral surface of the synthetic resin layer 5 may be shaped as described above, or the synthetic resin layer 5 may be circular and the shape on the cylinder 1 side may be a shape other than the circular shape described above. It is.

[Effects of the Invention] As described above, the present invention provides a synthetic resin layer provided on the outer circumferential surface of the piston with a sliding contact portion that is close to and slides into contact with the inner circumferential surface of the cylinder at least at room temperature, and a sliding contact portion of the cylinder. Since the spacer is provided with a spaced portion spaced apart from the inner circumferential surface, it is possible to effectively prevent noise and vibration at room temperature, and at the same time, it is possible to obtain an effective temperature compensation effect.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along line II--II in FIG. 1.

Claims (1)

[Claims] In a shock absorber comprising a piston fitted in a cylinder and a synthetic resin layer provided on the outer circumferential surface of the piston, the synthetic resin layer is in sliding contact with the inner circumferential surface of the cylinder, the synthetic resin layer having at least A shock absorber comprising: a sliding portion that is close to and slides in contact with the inner circumferential surface of the cylinder at room temperature; and a separation portion that is spaced apart from the inner circumferential surface of the cylinder.