JPH0942355A - Centering device for cylinder in hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out centering of a cylinder in a hydraulic buffer without using a centering washer. SOLUTION: In a hydraulic buffer formed in such a constitution that a cylinder 17 for slidably guiding a piston assembled on the bottom end part of a piston rod is housed concentrically with the axis line of an outer shell 8, a projection is arranged to guide the cylinder 17 from the outer peripheral surface of the outer shell 8 toward an inner side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a hydraulic shock absorber which is used in a suspension system of an automobile or the like and which suppresses vibration of a vehicle body.

[0002]

2. Description of the Related Art Generally, a hydraulic shock absorber mounted between a vehicle body and a wheel via a connecting member is formed by previously assembling each part into three subassemblies, and finally combining and connecting them. To be done. The outline is shown in FIG. 4A.
The description will be made based on a conventional hydraulic shock absorber whose internal structure is shown in FIG.

First, in the outer shell sub-assembly which is the first sub-assembly, a spring seat 14 is welded to a predetermined position on the outer peripheral surface of the outer shell 8, and a knuckle bracket 13 is press-fitted on the outer peripheral surface of the lower end portion and an inner peripheral surface of the lower end portion. The lower cap 12 is inserted into the lower cap, and the outer peripheral lower end surface of the lower cap is integrally welded together with the outer shell 8 and the knuckle bracket 13.

Next, a piston rod subassembly, which is a second subassembly, has a rebound cushion 3, a seal 5 for shutting off the outside air, and a stopper 2 fixed on a predetermined position of the piston rod 1 by spot welding or the like. A packing case 4 equipped with a rod guide 6 for slidably guiding a piston rod is successively fitted and inserted, and a piston valve 9 is attached to a small diameter portion of a lower end. The cylinder subassembly, which is the third subassembly, has the base valve 10 press-fitted on the lower surface of the cylinder 7 with the centering washer 11 interposed therebetween.

To assemble the above three subassemblies, the outer shell subassembly is first fixed to the base, and the cylinder subassembly is inserted therein. In this case, since the centering washer 11 having an outer diameter slightly smaller than the inner diameter of the outer shell 8 is attached to the lower end of the cylinder subassembly,
The base valve support leg 10A at the lower end of the cylinder sub-assembly is guided by the inner diameter of the outer shell 8 through the outer diameter of the centering washer 11, and is seated in the lower cap 12 at the bottom of the outer shell while being concentric. To do. The outer periphery of the centering washer 11 is shown in FIG.
As shown in FIG. 11, a cutout 11A is provided as a passage for hydraulic oil.

Next, the piston valve 9 assembled at the lower end of the piston rod subassembly is inserted into the cylinder 7 into which the hydraulic oil is injected, and the rod guide 6 which is attached to the packing case 4 together with the seal 5 has a small diameter. Insert the portion 6A into the cylinder 7 and seal the packing case 4
Let the lower end large diameter portion 4A of the outer shell 8 face the upper end of the outer shell 8,
A load is applied to the upper surface of the packing case 4 and press-fitted, and then the upper end of the outer shell 8 is sealed by welding or the like to form a hydraulic shock absorber.

In the prior art described above, the centering washer 11 is used as a centering dedicated part of the cylinder 7, but a structure in which a bubbling prevention ring is mounted is known as having a similar effect. Figure 4A
The bubble-prevention ring 15 using a sealing O-ring additionally shown in FIG. 1 is mounted in a fixed position by giving a tightening margin to the outer periphery of the cylinder 7. Its main purpose is to prevent foaming of the hydraulic oil in the tank chamber that is subjected to a stirring action when the tank chamber C coupled to the wheels via a knuckle (not shown) vibrates up and down violently when driving on a rough road. An appropriate gap is formed between the outer diameter of the ring 15 and the inner diameter of the outer shell 8 to resist the vertical movement of the hydraulic oil and suppress the stirring action.

The mounting position of the bubbling prevention ring 15 is the lowest oil level position of the tank chamber C (the piston rod is in the most extended state).
It is said that the position slightly lower is effective. Also in this case, when inserting the cylinder 7 into the outer shell 8,
Foaming prevention ring 1 mounted on the outer circumference of the cylinder 7.
When the outer diameter of 5 comes into contact with the inner diameter of the outer shell 8, the cylinder 7 is pushed back in the axial direction of the outer shell 8 through the foam prevention ring 15, so that the cylinder 7 is concentric with the axial line of the outer shell 8. It also has the effect of guiding to. As the bubble-prevention ring, in addition to the O-ring shown, a metal C pin having a joint in a part of an annular ring, a rubber band having a rectangular cross section, or a spiral coil spring may be used. In any case, a proper tightening margin is given to the outer circumference of the cylinder 7 to hold it in a fixed position. The centering washer 11 and the anti-foaming ring 15 can be used together,
Usually, only one of them is used.

In the hydraulic shock absorber formed as described above, when the piston rod 1 rises in the cylinder filled with hydraulic oil, the hydraulic oil in the sealed piston upper chamber A is passed through the piston valve 9. , Flows out into the piston lower chamber B. The passage resistance at this time becomes the extension side damping force. The withdrawal volume of hydraulic oil that is insufficient due to the rise of the piston rod 1 is sucked from the tank chamber C via the suction valve 10B attached to the base valve 10 arranged at the lower end of the cylinder 7.

On the contrary, when the piston rod 1 descends,
A part of the hydraulic oil in the piston lower chamber B moves to the piston upper chamber A through the non-return valve 9A attached to the piston valve 9, and at the same time, the hydraulic oil in the volume advancing the piston rod 1 causes the base valve 10 to move. It is discharged from the piston lower chamber B to the tank chamber C via the. The passage resistance at this time becomes the compression side damping force.

[0011]

As described above, when the cylinder sub-assembly is inserted into the outer shell sub-assembly, the lower end of the cylinder 7 is guided by the centering washer 11 to the inner diameter of the outer shell 8 so as to be concentric. It can be assembled in the secured state,
Since the centering washer 11 is formed by punching out a thin steel plate by a press, an operator is easily injured, and even if it is used for a cylinder of the same size because it is a single part, the inner diameter of the outer shell is different. Therefore, various types of parts are required, and management costs such as storage and man-hours for assembling occur in addition to the parts cost.

The present invention has been made in view of the above situation, and an object thereof is to provide a centering device capable of centering a cylinder without using a centering washer. is there.

[0013]

The means adopted by the present invention for solving the above-mentioned problems are as follows: "A cylinder attached to the lower end of the piston rod is slidably guided to the cylinder of the outer shell. On the other hand, a cylinder centering device for a hydraulic shock absorber characterized in that a projection for guiding the cylinder from the outer peripheral surface of the outer shell to the inner side is provided in the hydraulic shock absorber housed concentrically " Is.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The function of the centering washer 11 in the conventional structure shown in FIG. 4A is to guide the cylinder 7 concentrically with the axis of the outer shell 8, and the function is press-fitted into the lower end of the cylinder. Base valve 1
It suffices if the 0 support leg 10A is exerted in a section of only a few cm until it is seated on the lower cap 12 welded to the lower end of the outer shell. In other words, the outer shell 8
It is not necessary to maintain the concentricity in the middle of the insertion most of the depth from the upper end to the lower cap 12 at the bottom.

The present invention has been made paying attention to the above points, and its details will be described based on the first embodiment shown in FIG. 1A. The same parts as those of the conventional example will be described using the same reference numerals. At least three or more protrusions 8A having the same height from the outer peripheral surface of the outer shell 8 having a predetermined height from the lower cap 12 at the bottom of the outer shell toward the inside.
In addition, the inscribed circle at the apex of the protrusion is slightly enlarged so as to form a proper fitting gap with respect to the outer diameter of the cylinder 17. Practically, the fitting gap is about 1 mm
Set to a degree. Since the protrusion 8A can be formed into a bowl shape having a smooth curved surface by devising the shape of the processing jig, even if the base valve 10 at the lower end of the cylinder eccentrically contacts the protrusion 8A, the contact The part slides on the smooth curved surface and is pushed back inward. This action is performed in the same way when any of the protrusions is contacted, so that the base valve 10 at the lower end of the cylinder is pushed back until it becomes concentric with the axis of the outer shell 8 in the process of passing through the protrusion, so that the concentricity is maintained. Will be seated on the lower cap 12 in the state of being secured.

In this embodiment, since the projection 8A is provided in the section into which the knuckle bracket 13 is press-fitted, the external appearance of the hydraulic shock absorber is exactly the same as that of the conventional example. Further, the outer shell 8 of the hydraulic shock absorber has a wheel attached to the knuckle bracket 13 via a knuckle (not shown) and, after being assembled to the vehicle body, receives a bending moment due to the weight of the vehicle body, but is a protrusion that is weak against the bending moment. Since the 8A portion is provided in the press-fitting section of the knuckle bracket 13 having high rigidity, the bending strength is not reduced.

The projection 8A in FIG. 1B showing the XX cross section of FIG. 1A and FIG. 1A shows the case where it is arranged in a plane perpendicular to the axis of the outer shell 8.
The heights of A from the lower cap 12 do not necessarily have to be the same, and they may be provided slightly above and below. Even when the protrusions are provided vertically, the action of pushing the cylinder 17 back in the axial direction of the outer shell 8 is
The protrusions are sequentially contacted first, and the lower end of the cylinder is concentric with the axis of the outer shell 8 at a position where all the protrusions have passed.

In the first embodiment, the case where the protrusions are bowl-shaped protrusions independent of each other has been described, but the centering action can be realized even if the protrusions are not necessarily independent.

The second embodiment shown in FIG. 2A shows a case where the projection 8B is a continuous annular projection formed by roll processing or the like. By devising the shape of the roll processing jig so that the inner surface of the annular protrusion is a smooth curved surface, it is possible to realize the same centering action as that of the first embodiment described above. However, in this case, it is necessary to secure an appropriate gap between the inner diameter of the annular protrusion and the outer diameter of the cylinder to allow the working oil to flow, so there is a possibility of misalignment corresponding to this gap. Although it remains, there is no substantial misalignment, and since there is a self-centering function between the support leg of the base valve and the dish-shaped tapered contact surface of the lower cap, there is practically no problem.

Further, if the annular projection is provided in the vicinity of the lowest oil level position in the tank chamber, the stirring action of the hydraulic oil in the tank chamber during traveling on a bad road can be suppressed and the foaming of the hydraulic oil which makes the damping force unstable can be suppressed. Can be suppressed. FIG. 2B shows an annular projection 8B formed on the lower portion of the outer shell 8 as an external shape before the knuckle bracket 13 is press-fitted.

In the third embodiment shown in FIG. 3A, a continuous protrusion is formed in a spiral shape, and the gap between the inner diameter of the spiral protrusion and the cylinder outer diameter is suppressed to a small gap similar to that of the first embodiment. The centering performance is improved. Since the hydraulic oil can pass through the spiral passage formed between the spiral protrusions, the gap between the inner diameter of the spiral protrusion and the outer diameter of the cylinder can be reduced.

In this case, since the lower end of the cylinder comes into continuous contact with the spiral projection from the upper end to the lower end, the action of pushing the cylinder 17 back in the axial direction of the outer shell 8 is continuously performed, and the lower end of the cylinder is pushed. Outer shell 8
The cylinder 17 is concentric with the axis of the outer shell 8 at the position where the cylinder 17 has passed the spiral protrusion. The number of turns of the spiral protrusion for the centering action is about one, but the passage between the spiral protrusions can also be used as a resistance against the fluctuation of the oil level in the tank chamber during traveling on a rough road. Therefore, it is possible to suppress the stirring action of the hydraulic oil in the tank chamber and suppress the foaming of the hydraulic oil that makes the damping force unstable. Therefore, in order to enjoy this effect, the pitch of the spiral and the number of turns may be determined as necessary.

Although not shown, in any of the above-described embodiments, the protrusion may be provided not only on the lower end of the outer shell but also on the upper end of the outer shell. In this case, both the upper and lower ends of the cylinder 17 are concentric with the axis of the outer shell 8. Therefore, when press-fitting the packing case 4 into the cylinder 17 and the outer shell 8, be careful not to be concentric. You can

[0024]

As described above in detail, according to the present invention, as illustrated in the above embodiment, a part of the outer shell is formed from the outer peripheral surface toward the inner side without using a special part for centering. The centering effect is achieved by providing individual independent bowl-shaped projections, or continuous annular projections or spiral projections, so the cost of parts and storage costs when using special parts for centering Therefore, the number of assembling steps can be omitted, and the injury of the worker in the manufacturing process of the hydraulic shock absorber can be prevented. Further, in the case of a continuous annular projection or spiral projection, in addition to the above-mentioned effect, it is possible to suppress the stirring action of the hydraulic oil in the tank chamber and suppress the foaming of the hydraulic oil that makes the damping force unstable.

[Brief description of drawings]

FIG. 1A is a vertical cross-sectional view showing a first embodiment of the present invention.

FIG. 1B

FIG. 1A is an end view of the XX section of FIG.

FIG. 2A is a vertical sectional view showing a second embodiment of the present invention.

FIG. 2B

FIG. 2A is an external view of the lower portion of the outer shell showing the shape of the annular projection 8B of FIG. 2A.

FIG. 3A is a vertical cross-sectional view showing a third embodiment of the present invention.

FIG. 3B

FIG. 3A is an external view of the lower portion of the outer shell showing the shape of the spiral protrusion 8C of FIG. 3A.

FIG. 4A is a vertical cross-sectional view showing a centering structure according to a conventional technique.

FIG. 4B

FIG. 4A is a plan view showing the shape of the centering washer 11 of FIG.

[Explanation of symbols]

 1 Piston rod 7,17 Cylinder 8 Outer shell 8A Bowl-shaped protrusion 8B Annular protrusion 8C Spiral protrusion 9B Piston

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[Procedure amendment]

[Submission date] December 20, 1995

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

[Fig. 2]

[Figure 3]

FIG. 4

Claims (4)

[Claims] 1. A hydraulic shock absorber in which a cylinder, which is slidably guided to a piston attached to a lower end portion of a piston rod, is housed concentrically with respect to an axis line of the outer shell, from an outer peripheral surface of the outer shell. A centering device for a cylinder in a hydraulic shock absorber, comprising a protrusion for guiding the cylinder inward. 2. The projection for guiding the cylinder is a bowl-shaped projection that is formed from the outer peripheral surface of the outer shell toward the inside and is provided on the circumference of at least three equal parts. The cylinder centering device in the hydraulic shock absorber according to claim 1. 3. The centering of the cylinder in the hydraulic shock absorber according to claim 1, wherein the projection for guiding the cylinder is an annular projection continuously formed from the outer peripheral surface of the outer shell toward the inner side. apparatus. 4. The centering of the cylinder in the hydraulic shock absorber according to claim 1, wherein the projection for guiding the cylinder is a spiral projection continuously formed from the outer peripheral surface of the outer shell toward the inner side. apparatus.