JP2003120741A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the deterioration of a damping force characteristic by securing concentricity of a center rod and a piston rod and concentricity of the piston rod and a piston, and to stabilize damping force by preventing generation of vibration of a needle valve caused by a jet of a hydraulic fluid. SOLUTION: An inserting part 26 on the end of the center rod 25 is fitted in the piston rod 8, and both are calked and joined. A part of a bypass is formed on the outer periphery of the center rod 25. A cutout passage 31 is formed for communicating a rod side oil chamber 17 with the inside of the piston rod 8.

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 which is interposed between a vehicle body and a wheel in a vehicle such as a motorcycle and is suitable for use in a front fork or the like for damping vibrations from the road surface.

[0002]

2. Description of the Related Art As shown in FIG. 3, a front fork mounted between a vehicle body and a wheel of a motorcycle has a vehicle body side tube 1 and a wheel side tube 2 slidably fitted to each other and a wheel side. A damper 3 is erected at the center of the tube 2, and a cap 4 side of the vehicle body side tube 1 and a cylinder 5 of the damper 3 are provided.
A suspension spring 6 is interposed between the suspension spring 6 and.

Further, an adjuster 7 for adjusting the spring load of a suspension spring 6 is screwed into the cap 4, and an upper end of a piston rod 8 of a damper 3 is screwed into the adjuster 7 so that the piston rod 8 An adjuster 10 for adjusting the position of the control rod 9 for damping adjustment is provided therein.

Further, the lower end side of the piston rod 8 is guided through the rod guide 11 that closes the upper end of the cylinder 5 into the cylinder 5, and as shown in FIG. The inner circumference of the part is screwed.

The center rod 13 has a threaded connecting portion 12 having a larger diameter than the other portions, and is located on the side opposite to the threaded connecting portion 12, that is, the center rod 1.
At the lower end of 3, the piston 1 sliding on the inner circumference of the cylinder 5
4 is attached. In addition, the center rod 1
A needle valve 15 is provided in the cylindrical hole 13a of No. 3 so as to be slidable in the axial direction, and its upper end surface is controlled by a spring 16 housed in the cylindrical hole 13a.
Is urged in the direction of contacting the lower end surface of the.

Further, the inside of the cylinder 5 is divided into a rod side oil chamber 17 and a non-rod side oil chamber 18 by a piston 14, and these oil chambers 17 and 18 are ports provided in the piston 14 and the damping valve. 20 is composed of a perforated leaf valve and a leaf valve superposed on the perforated leaf valve so as to open and close the holes of the perforated leaf valve,
At the time of compression, these two valves work together to open the port provided in the piston, while at the time of expansion, only the leaf valve is opened to allow the hydraulic oil to pass through the port.

Although not shown, a base portion (not shown) for closing the lower end of the cylinder 5 and the lower end of the wheel side tube 2
Is equipped with a base valve, which is the opposite rod side oil chamber 1.
8 and the cylinder 5 and the wheel side tube 2 function to open and close a port communicating with an oil chamber (reservoir chamber).

The center rod 13 has an oil hole 21 penetrating in and out of the cylinder hole 13a in the radial direction, and a center oil hole 22 communicating axially with the cylinder hole 13a and the non-rod side oil chamber 18.
Are provided, and these oil holes 21 and the central oil hole 22 form a bypass of the hydraulic oil that bypasses the damping valve 20 and the port 19.

The tip of the needle valve 15 faces the inner end of the opening of the central oil hole 22, and the needle valve 15 is opened and closed with respect to the central oil hole 22 by operating the control rod 9. The amount of oil flowing through is adjustable.

Therefore, the driver adjusts the adjuster 1 from the vehicle body side.
By rotating 0, the control rod 9 moves up and down, and the flow path area of the bypass, that is, the opening area of the central oil hole 22 is adjusted by the needle valve or the like in the damper 3 to adjust the damping force high or low. Be seen.

The suspension spring 6 expands and contracts by rotating the adjuster 7 and moving it up and down, whereby the initial spring load as a hydraulic shock absorber is adjusted.

[0012]

Since the conventional front fork is constructed as described above, the damping force is adjusted by adjusting the flow passage area of the hydraulic oil by the needle valve 15 and the damping valve 20 in the center rod 13. Although the adjustment is possible and the initial spring load of the suspension spring 6 can be adjusted, in particular, since the center rod 13 for accommodating the needle valve 15 and the piston rod 8 are screwed together, these are adopted. It is difficult to accurately obtain the coaxiality of the piston rod 8, the center rod 13, and the cylinder 5 due to a coupling play between the meshing parts of
As a result, the sliding resistance between the piston 14 and the cylinder 5 is locally increased and becomes large, which is a factor that causes generation of chips and deterioration of the damping force characteristic associated therewith.

Further, the oil hole 21 provided in the center rod 13 is formed so as to penetrate radially inside and outside the cylindrical hole 13a.
In other words, since it is provided in a direction orthogonal (crossing) to the axial direction of the needle valve 15, the working oil flowing as a high-pressure jet flow through the oil hole 21 directly acts on the needle valve 15 in the radial direction. , This needle valve 1
However, there is a problem in that the damping force obtained as described above becomes unstable as a result of the slight vibration of 5 itself.

The present invention solves the above-mentioned conventional problems, and ensures the coaxiality between the center rod and the piston rod and the coaxiality between the piston rod and the piston to allow the piston to slide with respect to the cylinder. The purpose of the present invention is to obtain a hydraulic shock absorber capable of stabilizing the damping force by preventing the deterioration of the damping force characteristic, preventing the needle valve from vibrating due to the jet of hydraulic oil, and stabilizing the damping force. To do.

[0015]

[Means for Solving the Problems] To achieve the above object,
In the hydraulic shock absorber according to the invention of claim 1, a hollow piston rod is movably inserted into a cylinder via a piston, and the cylinder is partitioned by the piston into a rod side oil chamber and an anti-rod side oil chamber. The rod-side oil chamber and the anti-rod-side oil chamber are opened and closed via a port provided in the piston and a damping valve provided at the open end of this port, and the piston is further provided with a center rod provided in the center of the piston. In the hydraulic shock absorber in which a bypass bypassing the damping valve is formed in the center rod and the opening area is adjusted by a needle valve movably inserted in the piston rod. The insertion part at the end of the center rod is fitted into the piston rod, and both are crimped together. , Characterized in that the formation of the cutout passage connecting the rod side oil chamber and a piston the rod and forming a part of the bypass.

As a result, the piston rod is fixed to the center rod in a state where the coaxiality is maintained, the coupling backlash does not occur between them, and the coaxiality between the piston and the piston rod is secured, and It is possible to ensure smooth sliding of the piston with respect to the cylinder.

Further, the oil passage forming the bypass is formed as a notch passage on the outer peripheral side of the center rod where the jet of hydraulic oil does not directly collide with the needle valve in the direction intersecting the axial direction of the needle valve. It is possible to prevent the generation of the vibration and the destabilization of the damping force.

Further, in the hydraulic shock absorber according to the invention of claim 2, the center rod has a body into which the center rod is inserted in the center of the piston, a flange integrally connected to the body, and an insertion portion standing upright from the flange. An oil hole is formed in the center of the body, the flange, and the insertion part to connect the anti-rod side oil chamber to the piston rod.There is a notch passage on the surface of the flange facing the rod side oil chamber and the outer periphery of the insertion part. It is characterized in that a bypass is formed by the oil hole and the cutout passage.

As a result, the coaxiality of the center rod and the piston rod can be ensured by a simple insertion structure for these, the weight of these joints can be reduced, and a part of the oil hole forming the bypass can be inserted into the insertion portion. By providing it on the outer periphery, it is possible to prevent the jet flow of the hydraulic oil from directly interfering with the tip portion of the needle valve in the radial direction.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged cross-sectional view showing the structure of a main part of the present invention, which is shown in FIG. The same components as those of the above are denoted by the same reference numerals, and duplicate description thereof will be omitted.

However, although the cylinder 5 described later is described as a cylinder for a damper in a front fork with built-in damper, it can also be applied as a cylinder of a general hydraulic shock absorber.

In the figure, reference numeral 8A is a piston rod, and a control rod 9 for adjusting the amount of attenuation, the amount of which is adjusted by the adjuster 10, is inserted into the piston rod 8A.

The lower end surface of the control rod 9 is in contact with the upper end surface of the needle valve 15 as shown in the drawing.
The needle valve 15 is axially slidably provided in a small diameter cylindrical hole 23 at the end (lower end) of the piston rod 8A.

Further, in the large-diameter cylindrical hole 24 at the lowermost end of the piston rod 8A, the insertion portion 26 following the main body 28 of the center rod 25 as shown in FIG. 2 is tightly fitted, and both are denoted by reference numeral 27 in the drawing. They are caulked by the caulking joints shown.

The center rod 25 is formed by the piston 14
A main body 28 inserted in the center of the main body 28, a flange 29 integrally connected to the main body 28, and the insertion portion 26 standing upright from the flange 29. The main body 28, the flange 29, and the center portion of the insertion portion 26 The central oil hole 3 that connects the anti-rod side oil chamber 18 and the inside of the piston rod 8A.
0 is formed.

As shown in FIG. 2, a continuous cutout passage 31 is formed on the surface of the flange 29 facing the rod-side oil chamber 17 and on the outer periphery of the insertion portion 26. The central oil hole 30, which is an oil hole,
A bypass is formed to bypass the damping valve 20 and the port 19.

As shown in FIG. 2, a ring-shaped concave groove 32 is formed in advance on the outer periphery of the insertion portion 26, and the lower end portion (cylindrical portion) of the piston rod 8A is formed in the concave groove 32. The center rod 25 is coaxially connected to the piston rod 8A by being crimped.

Therefore, in the hydraulic shock absorber according to this embodiment, during the compression stroke of the piston rod 8A, the bypass consisting of the central oil hole 30 and the cutout passage 31 is provided in the anti-rod side oil chamber 18 in the low speed region of the piston. Hydraulic oil is the rod side oil chamber 1
7, the damping valve 20 is opened in the medium and high speed range, and the working oil flows into the rod-side oil chamber 17, which also produces a compression-side damping force.

Then, the hydraulic oil corresponding to the intruding volume of the piston rod 8A flows out into the reservoir chamber by opening the base valve provided in the base portion.

On the other hand, during the extension stroke of the piston rod,
In the low speed range of the piston rod, the hydraulic oil in the rod side oil chamber 17 flows to the anti-rod side oil chamber 18 through the bypass consisting of the central oil hole 30 and the cutout passage 31, and in the middle and high speed range the damping valve 20 is opened to operate. Oil flows into the oil chamber 18 on the side opposite to the rod side, whereby a pre-calculated extension side damping force is generated.

Then, the hydraulic oil corresponding to the withdrawn (raised) volume of the piston rod 8A is replenished from the reservoir chamber to the non-rod side oil chamber 18 through the base valve provided in the base portion.

In such a hydraulic shock absorber, the piston rod 8
Since A and the center rod 25 have their axes aligned with each other and are caulked and fixed by the caulking joint portion 27, mutual coaxiality is maintained, and therefore, coaxiality between the piston rod 8A and the piston 14 is also maintained, The piston 14 can smoothly slide in the axial direction along the inner peripheral surface of the cylinder 5.

As a result, there is no generation of chips and the like as in the conventional screw-coupled one, and stable damping force characteristics can be obtained.

In the conventional screw connection, the thickness of the threaded portion of the center rod 25 needs to be sufficiently thick. However, in the present invention, only the caulking connection is performed. It is not necessary to have a wall thickness, and the weight can be sufficiently reduced.

During the compression stroke and extension stroke of the piston rod 8A, the working oil flows from the anti-rod side oil chamber 18 into the rod-side oil chamber 17, or from the rod-side oil chamber 17 to the anti-rod side oil chamber 18. When inflowing, the working oil flows through the central oil hole 30 and the cutout passage 31 forming the bypass.

However, this flow does not collide with the needle valve 15 in a direction intersecting (orthogonal to) the axial direction of the needle valve 15.
Therefore, the generation of the slight vibration is prevented, so that the damping force generated can be stabilized.

In the above embodiment, the connecting structure of the piston rod 8A and the center rod 25 in the front fork has been described. However, the connecting structure of the piston rod and the center rod in a general hydraulic shock absorber is as follows.
It goes without saying that the present invention can be applied.

[0038]

As described above, according to the present invention, the insertion portion at the end of the center rod is fitted into the piston rod to crimp the two, and further, a part of the bypass is provided on the outer periphery of the center rod. Since the notch passage that connects the oil chamber on the rod side and the inside of the piston rod is formed at the same time,
The piston rod can be fixed to the center rod while maintaining the coaxiality, and it is possible to prevent the coupling backlash from occurring between them, to secure the coaxiality in the piston and the piston rod and to smoothly slide the piston on the cylinder. Motion can be secured.

Further, the oil passage forming the bypass is a notched passage on the outer peripheral side of the center rod where the jet of hydraulic oil does not directly collide with the needle valve in the direction intersecting the axial direction of the needle valve. It is possible to obtain an effect that it is possible to prevent the generation of the vibration and the destabilization of the damping force accompanying the vibration.

Further, the center rod is composed of a main body inserted into the center of the piston, a flange integrally connected to the main body, and an insertion portion standing upright from the flange,
An oil hole is formed in the center of the body, flange, and insertion part to connect the anti-rod side oil chamber to the inside of the piston rod. Since the notch passage that forms a bypass with the passage is provided, the coaxiality of the center rod and piston rod can be secured by these simple insertion structures, and part of the oil hole that forms the bypass is located on the outer periphery of the insertion part. By providing it, it is possible to reliably prevent the jet flow of the hydraulic oil from directly interfering with the tip portion of the needle valve in the radial direction.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part showing a hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a center rod in FIG.

FIG. 3 is a front view showing the whole of a conventional hydraulic shock absorber, which is partially broken.

FIG. 4 is an enlarged vertical sectional view showing a main part of the hydraulic shock absorber in FIG.

[Explanation of symbols]

5 cylinders 8 piston rod 9 Control rod 14 pistons 15 Needle valve 17 Rod side oil chamber 18 Oil chamber on the non-rod side 19 ports 20 damping valve 25 Center rod 26 Insert 28 body 29 flange 30 Central oil hole (oil hole) 31 notch passage

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ikko Minekawa             2-4-1, Hamamatsucho, Minato-ku, Tokyo World Trade             Yasu Center Building Kayaba Industry Co., Ltd. F term (reference) 3J069 AA46 CC15 DD02 DD47 EE02                       EE39

Claims (2)

[Claims] 1. A hollow piston rod is movably inserted into a cylinder through a piston, and the inside of the cylinder is divided by a piston into a rod-side oil chamber and a non-rod-side oil chamber. The anti-rod side oil chamber is opened and closed via a port provided on the piston and a damping valve provided at the open end of the port, and the piston is further coupled to the piston rod via a center rod provided at the center of the piston, A bypass that bypasses the damping valve is formed in the center rod, and in the hydraulic shock absorber in which the opening area is adjusted by a needle valve that is movably inserted into the piston rod, the insert portion at the end of the center rod is Fitted inside the piston rod and caulked together, and further around the center rod,
A hydraulic shock absorber, characterized in that a cutout passage is formed which forms a part of the bypass and connects the rod-side oil chamber and the inside of the piston rod. 2. The center rod comprises a main body into which the center of the piston is inserted, a flange integrally connected to the main body, and an insertion portion standing upright from the flange. An oil hole that connects the anti-rod side oil chamber and the inside of the piston rod is formed, and a cutout passage is formed on the surface of the flange facing the rod side oil chamber and the outer periphery of the insertion portion. The hydraulic shock absorber according to claim 1, wherein a bypass is formed.