JP2002364695A - Hydraulic damper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic damper capable of always providing a specified friction to a piston rod in the very slow speed range of a piston irrespective of the type of an oil seal. SOLUTION: In this hydraulic damper, a rod guide 2 and an oil seal 3 are fitted to the end part of a cylinder 1, and the piston rod 4 movably inserted into the cylinder 1 through the piston is led to the outside in slidable contact with the inner peripheral surfaces of the rod guide 2 and the oil seal 3. A bush 6 providing the specified friction to the piston rod 4 when the piston speed is very low is fitted into the inner periphery of the rod guide 2. The bush 6 comprises a cylindrical core metal 22, an elastic cylindrical bush body 20 installed inside the core metal 22, and a check valve 8 facing diagonally upward and continuously connected to the bush body 20 in slidable contact with the outer peripheral surface of the piston rod 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber used as a suspension for a vehicle, and more particularly to a hydraulic shock absorber for applying a constant friction to a piston rod in a low speed range of the piston.

[0002]

2. Description of the Related Art A hydraulic shock absorber generally used as a suspension for an automobile or the like is provided with a rod guide and an oil seal at an end of a cylinder, and a piston rod is movably inserted into the cylinder via a piston. The piston rod extends to the outside while sliding on the inner periphery of the rod guide and the inner periphery of the oil seal. The rod guide cooperates with the piston to guide the piston rod in the axial direction, and the oil seal prevents oil in the cylinder from leaking to the outside. A band is provided on the outer circumference of the oil seal, and a certain friction is generated between the inner circumference of the oil seal and the outer circumference of the piston rod by the tightening force of the band and the elasticity of the oil seal itself. ing.

[0003]

Generally, in a low-speed range of a piston speed, almost no flow resistance is generated in an orifice or a damping valve provided in a piston or the like, so that no damping force is generated. Friction affects the slidability of the piston rod, and thus also affects the riding comfort of the vehicle.

For this reason, when designing a hydraulic shock absorber, the magnitude of friction between the oil seal and the piston rod is calculated, and based on this calculation, the oil seal is mounted on the outer periphery of the piston rod, and in the low speed range of the piston, Also, a certain friction is generated.

However, if the oil seal repeatedly slides on the piston rod during long-term use, the oil seal may be deteriorated. In this case, the friction of the oil seal against the piston rod does not work as intended, and as a result, it becomes difficult to suppress minute vibrations of the piston and the piston rod in a low-speed range of the piston. If the fine vertical vibration remains afterwards and continues forever, a problem may occur that the vehicle body vibrates forever and the ride comfort is deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic shock absorber which can always apply a constant friction to a piston rod in a very low speed range of a piston regardless of an oil seal.

[0007]

In order to achieve the above object, the present invention provides a piston provided with a rod guide and an oil seal at an end of a cylinder, and movably inserted into the cylinder via a piston. In a hydraulic shock absorber in which the rod slides between the rod guide and the inner periphery of the oil seal and extends to the outside, constant friction is applied to the piston rod when the piston speed is very low at the inner periphery of the rod guide. The bush to be fitted is fitted, the bush is a cylindrical metal core, an elastic cylindrical bush body provided inside the metal core, and an obliquely upward facing sliding contact with the outer periphery of the piston rod connected to the bush body. And a check valve.

In this case, it is preferable that the check valve connected to the bush body is formed of a conical lip integrally provided at the upper end of the bush body.

Similarly, the check valve connected to the bush main body may be composed of a cylindrical portion erected at the upper end of the bush main body and a conical lip formed at the upper end of the cylindrical portion.

[0010] Similarly, a check valve connected to the bush main body may be provided integrally with the bush main body in an inner space portion of the bush main body.

Similarly, when a check valve is connected to the bush body, an annular groove is formed inside the bush body, and a cylindrical portion and one or more lips provided on the inner periphery of the cylindrical portion are formed in the annular groove. May be provided.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

A hydraulic shock absorber used as a vehicle suspension according to each embodiment of the present invention is provided with a rod guide 2 and an oil seal 3 at an end of a cylinder 1 as shown in FIG. A piston rod 4 movably inserted through a piston through the rod guide 2
And the inner circumference of the oil seal 3 is slidably brought out to the outside. Further, in the present invention, a bush 6 that applies a constant friction to the piston rod 4 when the piston speed is very low is fitted to the inner periphery of the rod guide 2 to prevent backflow of air and oil into the bush 6. The check valve 8 is connected.

The details will be described below.

An outer shell 9 is disposed concentrically with the cylinder 1, and a rod guide 2 is fixed to upper ends of the cylinder 1 and the outer shell 9.

An oil seal 3 composed of upper and lower lips urged by a band 11 is provided on the outer side above the rod guide 2, and the oil seal 3 is supported by a support projection 13 of the rod guide 2 via a support fitting 12. And is held by the caulking portion 9 a of the outer shell 9 and the support plate 14.

The oil seal 3 is in sliding contact with the outer periphery of the piston rod 4, and the oil and air stored in the oil storage chamber 15 of the rod guide 2 pass through an oil passage 16 formed in the rod guide 2 and a reservoir 17 inside the outer shell 9. Is to be collected.

The inner periphery of the bush 6 is in sliding contact with the piston rod 4 so as to apply a certain friction to the piston rod 4 in the low speed range of the piston.

The cylinder 1 has an oil chamber 18 defined by a piston. Air mixed with oil in the oil chamber 18 flows upward through the inner periphery of the bush 6 and the check valve 8. However, the check valve 8 prevents backflow of oil and air flowing out above the bush 6, and these are always collected in the reservoir 17 from the oil sump chamber 15. The bush 6 has a metal core 22 on the outer peripheral side as described later, and this metal core 22 abuts on the inner circumference of the rod guide 2 and imparts friction to the piston rod 4 of the bush 6 by the elasticity of the bush 6 itself. I have.

As shown in FIG. 1, the bush 6 has a cylindrical core 22, an elastic cylindrical bush body 20 provided inside the core 22, and a piston rod 4 connected to the bush 20. And an obliquely upward check valve 8 slidably in contact with the outer periphery of the valve.

The core metal 22 may be made of a metal plate such as copper, or may be made of an elastic material and generate a repulsive force. The bush body 20 is preferably formed of an elastic material such as rubber such as NBR or urethane resin, and is preferably formed of a composite material having high durability and elasticity. The elasticity of the bush body 20 imparts friction to the piston rod 4.

A slight gap 25 is formed between the inner circumference of the bush body 20 and the outer circumference of the piston rod 4 to allow oil and air to flow out. Backflow to the oil chamber 18 is prevented.
The check valve 8 is formed of a conical lip integrally rising upward from the upper end of the bush body 20. This lip is raised from the position of the dotted line and contacts the outer periphery of the piston rod 4 with an arbitrary interference as shown by the solid line. Check valve 8
May be molded into a so-called dug-bill mold.

According to the hydraulic shock absorber according to the above-described embodiment, a fixed friction can be applied to the piston rod 4 by the bush 6 irrespective of the friction caused by the oil seal 3. For this reason, even when a large vibration is generated in the vehicle body due to the rough road while the vehicle is running, and the fine vibration remains thereafter, the fine vibration suppresses the vertical movement of the piston rod 4 due to the friction of the bush 6 with the piston rod 4. It is solved by doing. In other words, the slight vibration of the vehicle body in the very low speed range of the piston speed is suppressed by the friction, and the riding comfort can be improved.

FIGS. 2, 3, 4 and 5 relate to other embodiments of the present invention, in which the structure of the bush, particularly the structure of the check valve, is modified. Other structures,
The operation and effect are the same as those in the case of FIG. 1, and the same structures are denoted by the same reference numerals and the details are omitted.

That is, the bush 6 shown in FIGS. 2, 3, 4, and 5 is the same as that of FIG. In this case, the check valve 8 shown in FIG. 2 is composed of a cylindrical portion 8a erected at the upper end of the bush body 20 and a conical dug-billed lip 8b formed at the upper end of the cylindrical portion 8a. The check valve 8 may be bonded to the core metal 22 and the upper end of the bush body 20 or may be press-fitted into the inner periphery of the rod guide 2.

Similarly, the check valve 8 of the bush 6 shown in FIG. 3 is provided upward in the inner space 26 of the bush body 20 integrally with the bush body 20. The space 26 is formed in an annular shape, and allows oil as lubricating oil to accumulate therein.

Similarly, in the bush 6 shown in FIGS. 4 and 5, an annular groove 27 is formed inside the push body 20, and a cylindrical portion 8c and a lip provided on the inner periphery of the cylindrical portion 8c are formed in the annular groove 27. 8d is provided.

In this case, the check valve 8 shown in FIG.
d, but in the case of FIG.
Are provided. It is possible to adjust the size of the friction according to the number of the lips 8d.

[0029]

According to the present invention, the following effects can be obtained.

(1) According to the invention of each claim, a bush is fitted to the inner periphery of the rod guide, and the bush applies a constant friction to the piston rod in a very low speed region of the piston. For example, even if a minute vibration remains after a large vibration of the vehicle body, this vibration is suppressed by the above-mentioned friction, and the minute vibration is prevented from continuing forever. As a result, the vehicle body is stabilized and riding comfort is improved.

(2) Similarly, the bush is provided with a passage means and a check valve for preventing backflow, so that oil and air in the cylinder are allowed to leak from the oil chamber of the cylinder. Backflow can be prevented, and the damping force in a damping force generating mechanism such as a port provided in a piston or a damping valve can be stabilized.

(3) Similarly, since friction can be generated by the bush regardless of the oil seal or the like, even if the oil seal is deteriorated, the friction on the piston rod can always be exerted.

(4) Similarly, the durability of the bush main body can be improved because the bush main body is reinforced by the cored bar.

[Brief description of the drawings]

FIG. 1 is a partially enlarged longitudinal sectional front view of a hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a partially enlarged longitudinal sectional front view of a hydraulic shock absorber according to another embodiment.

FIG. 3 is a partially enlarged longitudinal sectional front view of a hydraulic shock absorber according to another embodiment.

FIG. 4 is a partially enlarged longitudinal sectional front view of a hydraulic shock absorber according to another embodiment.

FIG. 5 is a partially enlarged longitudinal sectional front view of a hydraulic shock absorber according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Rod guide 3 Oil seal 4 Piston rod 6 Bush 8 Check valve 8a Cylindrical part 8b Lip 8d Lip 20 Bush body 22 Core metal

Claims (5)

[Claims] 1. A rod guide and an oil seal are provided at an end of a cylinder, and a piston rod movably inserted into the cylinder via a piston slides on the inner periphery of the rod guide and the oil seal and is led out. In the hydraulic shock absorber, a bush that gives a certain friction to the piston rod when the piston speed is very low is fitted to the inner periphery of the rod guide, and the bush is fitted with a cylindrical core metal and a core. A hydraulic shock absorber comprising: an elastic cylindrical bush main body provided inside gold; and an obliquely upward check valve connected to the bush main body and slidingly contacting the outer periphery of a piston rod. 2. The hydraulic shock absorber according to claim 1, wherein the check valve comprises a conical lip integrally provided at an upper end of the bush body. 3. The hydraulic shock absorber according to claim 1, wherein the check valve comprises a cylindrical portion erected at the upper end of the bush main body and a conical lip formed at the upper end of the cylindrical portion. 4. The hydraulic shock absorber according to claim 1, wherein the check valve is provided integrally with the bush body in an inner space portion of the bush body. 5. An annular groove is formed inside the bush body,
2. The hydraulic shock absorber according to claim 1, wherein a check valve comprising a cylindrical portion and one or a plurality of lips provided on an inner periphery of the cylindrical portion is provided in the annular groove.