JPH042821B2 - - Google Patents

Description

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

Conventional technology and its problems Generally, a cylindrical shock absorber used in the suspension of passenger cars, trucks, etc. has a cylinder with a smaller diameter inserted and fixed into the outer shell of the largest diameter, and an oil seal is attached to the upper end of the cylinder. In addition, a base valve is provided at the lower end, and a piston rod is inserted through a guide bush through a rod guide provided below the oil seal of the cylinder, and a piston that slides on the inner peripheral surface of the cylinder is installed near the inner end of the rod guide. is fixedly installed to divide the inside of the cylinder into upper and lower chambers. Hydraulic oil is stored inside the cylinder and between the cylinder and the outer shell, and the amplitude of the relative movement between the cylinder and piston rod caused by vehicle vibration is controlled by the flow resistance of the hydraulic oil passing through the orifice provided in the piston and the base. It has a function of damping the leaf valve by the resistance when pushing it open. That is, in a shock absorber, there is a sliding relationship between the inner peripheral surface of the cylinder and the piston, and between the piston rod and the guide bush that supports it.

In conventional shock absorbers, the frictional resistance at the sliding part tends to increase after long-term use, and as a result, the original design conditions have changed.
Problems have arisen in which the ride comfort of automobiles deteriorates and the steering stability deteriorates.

According to research conducted by the present inventors, these causes are thought to be as follows. To prevent damage to the inner circumferential surface of the cylinder, the piston is in sliding contact with the cylinder through a piston ring fitted into a groove provided on the outer circumference of the piston. The surface is made relatively soft by forming a sintered layer or using a material made of reinforced resin. However, cylinders are usually made of drawn steel pipes due to cost advantages.
Its hardness is about Hv160, and when observed microscopically, there are minute irregularities of several micrometers on the surface.
It has a relatively rough surface. Due to long-term sliding, the protrusions on this rough surface are shaved off and fall off as metal powder, but when this gets into the space between the sliding surface of the piston ring, the cutting action causes deeper damage to the inner circumferential surface of the cylinder. This increases the dynamic resistance, and especially when the piston ring is made of resin, the fallen metal powder gets stuck in the piston ring and constantly rubs against the inner peripheral surface of the cylinder, promoting the generation of metal powder, resulting in a repeating vicious cycle. In addition, foreign matter often exists in the system from the beginning due to chips during manufacturing or carelessness when injecting hydraulic oil. The above situation is the same in the case of the guide bush and piston rod, and the sliding surfaces of both are damaged and frictional resistance increases.

Object and Structure of the Invention The present invention provides that metal powder generated at the sliding contact portion of the shock absorber as described above enters between the sliding surfaces and causes grinding damage to the inner peripheral surface of the cylinder or the surface of the piston rod, further promoting the generation of metal powder. The aim is to prevent this vicious cycle.

This purpose is to provide a shock absorber in which a piston rod, which is slidably housed in a cylinder, is guided by a rod guide, and which is provided with a piston that slides on the inner peripheral surface of the cylinder near the inner end of the piston rod. A pair of grooves that are inclined at a predetermined angle with respect to the sliding direction and intersect with each other are provided on the sliding surface of the piston and/or the sliding surface of the piston and the cylinder, and each groove is located above and below the sliding surface. Extends to near both edges,
This is achieved by a shock absorber characterized in that both ends are closed.

Furthermore, by fitting a guide bush on the sliding surface of the rod guide with the piston rod and/or a piston ring on the sliding surface of the piston with the cylinder, a low-cost, high-precision shock absorber can be obtained.

Specific Means for Solving the Problems The present invention will be described in more detail below based on embodiments shown in the drawings.

FIG. 2 is a schematic side sectional view of the shock absorber 1 of the present invention, in which a small-diameter cylinder 3 is fixed coaxially within a large-diameter outer shell 2.
An oil seal 4 is tightly fitted to the upper end of the cylinder 3, and a base valve 5 is tightly fitted to the lower end to separate the outer shell 2 and the cylinder 3. A rod guide 6 is located inside the cylinder 3 directly below the oil seal 4.
is fixed, and a piston rod 7 is inserted into the cylinder 3 from above in the axial direction through this central hole. A guide bush 6a that comes into sliding contact with the piston rod 7 is fitted and fixed into the inner peripheral surface of the center hole of the guide 6. Further, a piston 9 having an orifice 8 is fixedly installed near the inner end of the piston rod 7, and a piston ring 9a which is in sliding contact with the inner circumferential surface of the cylinder 3 is fitted onto the outer circumferential surface of the piston 9. The piston 9 divides the inside of the cylinder 3 into upper and lower chambers. Further, hydraulic oil is stored inside the cylinder 3 and in the space between the cylinder 3 and the outer shell 2, and the vibration displacement in the axial direction of the cylinder transmitted to the piston rod 7 due to the vibration of the vehicle is caused by the vibration displacement inside the cylinder 3. This results in a change in the volume of both the upper and lower chambers, and the resulting flow resistance during movement of the hydraulic oil through the orifice 8 or the base valve 5 damps the amplitude of the vibrations.

The rod guide 6 has the function of correctly regulating the vertical displacement of the piston rod 7 in the axial direction.

It will be understood that in the above-described configuration, there is a sliding relationship between the inner circumferential surface of the cylinder 3 and the piston ring 9a, and between the outer circumferential surface of the piston rod 7 and the guide bush 6a. The present invention is characterized in that a recess 10 is provided in the sliding surfaces of the piston ring 9a and the guide bush 6a, as shown in FIG. This recess 10 is formed by metal powder generated from the sliding surface, especially the inner peripheral surface of the cylinder, due to friction during sliding, cutting powder generated during manufacture and assembly of the shock absorber and remaining inside, or when hydraulic oil is injected. It is necessary to have a depth and width that can accommodate mixed foreign matter etc. with sufficient margin. In addition, its shape is a pair of inclined grooves that intersect with each other at opposite inclinations between the upper and lower edges of the sliding surface, and intersect with each other at the center. It doesn't reach the target and becomes a blind groove.

In the shock absorber of the present invention having such a structure, metal powder that falls off from the sliding surface inside the cylinder, especially the inner circumferential surface of the cylinder that makes sliding contact with the piston ring, due to long-term use, is removed from the recess provided in the sliding surface. 10, it is pressed against the sliding surface between the piston ring 9a and the inner circumferential surface of the cylinder 3, like a conventional shock absorber, and may further damage the inner circumferential surface of the cylinder or damage the piston ring. 9
This phenomenon can be avoided by inserting it into the hole and constantly performing the cutting action. In addition, even if foreign matter that has been mixed into the cylinder since the beginning of use or newly mixed into the hydraulic oil as described above reaches the sliding surface due to the circulation of the hydraulic oil, it can be removed in the recess 10. This prevents secondary damage to the sliding contact surface caused by these foreign objects. Furthermore, since the recess 10 also functions as a type of oil reservoir and is always filled with hydraulic oil, seizure of the sliding surface can be prevented.

Effects of the Invention As detailed above, according to the present invention, a recess is provided in the sliding surface of the piston and the cylinder and/or the sliding surface of the rod guide and the piston rod, so that foreign matter such as metal powder can be taken into the recess and prevent the piston from sliding. Therefore, it is possible to prevent scratches on the inner circumferential surface of the cylinder and the outer circumferential surface of the piston rod caused by the cutting effect of the metal powder.
Further, since the recess is formed as a discontinuous closed groove or recess so as not to communicate between the upper and lower edges of the sliding surface, the oil sealing effect of the piston ring and guide bush is not impaired. This avoids an increase in sliding resistance due to long-term use of the shock absorber, thereby increasing its lifespan.

[Brief explanation of drawings]

FIG. 1 is a developed view of a sliding surface of a piston ring or guide bush of the present invention, and FIG. 2 is a schematic side sectional view of a shock absorber to which the present invention is applied. 1...Shock absorber, 2...Outer shell, 3...Cylinder, 4...Oil seal, 5...
...Base valve, 6...Rod guide, 6a...
Guide bush, 7... Piston rod, 8...
Orifice, 9...piston, 9a...piston ring, 10...recess.

Claims (1)

[Scope of Claims] 1. A shock absorber in which a piston rod slidably installed in a cylinder is guided by a rod guide, and a piston that slides on the inner peripheral surface of the cylinder is provided near the inner end of the piston rod. A pair of grooves that are inclined at a predetermined angle with respect to the sliding direction and intersect with each other are provided on the sliding surface of the rod guide with the piston rod and/or the sliding surface of the piston with the cylinder, and each groove is A shock absorber characterized by extending to near both upper and lower edges of a surface and having both ends closed. 2. The shock absorber according to claim 1, wherein a guide bush is provided on the sliding surface of the rod guide with respect to the piston rod. 3. The shock absorber according to claim 1 or 2, wherein a piston ring is fitted on a sliding surface of the piston with respect to the cylinder.