JPH03219134A - Hydraulic buffer - Google Patents

Abstract

PURPOSE:To prevent the generation of noise and obtain a stable damping force characteristic by providing a seal ring with throttle passages communicating with an inner cylinder side gap between a piston rod and a rod guide, and a gas return passage. CONSTITUTION:In a case when gas in a reservoir chamber 29 enters into an inner cylinder 20 due to vibration or the like, the gas accumulated at the upper part in an upper chamber flows upward together with oil liquid from a gap 49 between a piston rod 31 and a bush 35 and passes upward through the throttle passages 45, 46 of a seal ring 40. Because of the small passage area of the throttle passages 45, 46, oil liquid in this case hardly flows, but only gas flows, and the gas having passed through upward opens a check valve mechanism 47 so as to be returned to the reservoir chamber 29. The seal ring 40 is thus fitted into the recessed groove 39 of a rod guide 33 in such a state as to be substantially restricted in its axial movement, so that the seal ring 40 is prevented from colliding with both side faces 43, 44 of the recessed groove 39, and therefore the generation of noise is prevented.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a hydraulic shock absorber used in vehicles and the like.

(Prior technology) Hydraulic shock absorbers have two
The damping force is reduced by restricting the flow of oil between the two chambers caused by the movement of the piston and the flow of oil between the inner cylinder and the reservoir chamber between the inner and outer cylinders. There is a dual-tube hydraulic shock absorber that generates it. This type of hydraulic shock absorber is designed to compensate for the excess or deficiency of oil in the inner cylinder caused by the movement of the piston rod, which has one end to which the piston is fixed and the other end to protrudes outside, into the inner cylinder. Oil fluid is allowed to flow between the inside of the cylinder and the reservoir chamber, and low-pressure gas is sealed in the reservoir chamber.

However, in such a case where gas is sealed in the reservoir chamber, the gas may leak from the reservoir chamber into the inner cylinder due to vibration or the like.

Therefore, a mechanism is provided to return this leaked gas to the reservoir chamber.

Since this mechanism is normally attached to the vehicle body by projecting the piston rod upward, the hydraulic shock absorber is provided on the protruding side of the piston rod, and has the structure shown in FIGS. 5 and 6.

To roughly explain this structure, a piston rod l fixed to a piston (not shown) or a shock absorber main body 2 protruding outside.
A rod guide 3 for slidably guiding the piston rod 1 and an oil seal 4 for preventing oil from leaking to the outside are provided at the upper end of the piston rod. A notch 5 is formed on the outer periphery of the rod guide 3, and this notch 5 forms a space 6 between the rod guide 3 and the oil seal 4, and a space between the inner cylinder 7 and the outer cylinder 8. It is connected to reservoir chamber 9. Then, the space 7 and the notch 5
Thus, a gas return passage II is formed for returning the gas that has passed through the gap 10 between the piston rod 1 and the rod guide 3 to the reservoir chamber 9.

A concave groove 12 is formed in the circumferential direction on the inner periphery of the funnel guide 3 between the piston rod l and the rod guide 3, and a seal ring 13 that fits around the piston rod l is disposed in the concave groove 12. has been done. This seal ring 1
3 allows only gas to flow as much as possible while regulating the flow of liquid, and is arranged movably in the axial direction of the piston rod l in the groove 12, and has a plurality of grooves 14 extending in the radial direction on the upper end surface. It is formed. This groove 14 connects the gap 10 between the piston rod l and the rod guide 3 and the gas return passage 11 when the seal ring 13 separates from the lower side surface 15 of the groove 12 and comes into contact with the upper side surface 16. A throttle passage 17 with a small communicating flow area is constructed (the state shown in FIG. 6).

A check valve mechanism 18 is provided in the middle of the gas return passage 11 to allow the flow of gas from the inside of the inner cylinder 7 to the inside of the reservoir chamber 9 and to restrict the flow of gas from the inside of the reservoir chamber 9 to the inside of the inner cylinder 7. It is provided.

According to this configuration, during the extension stroke of the hydraulic shock absorber, the inner cylinder 7
The oil pressure inside rises, and the gas accumulated in the upper part of the inner cylinder 7 flows upward through the gap 1o between the piston rod 1 and the rod guide 3 along with the oil, pushing up the seal ring 13 and pushing up the upper side surface 16 of the groove 12. bring it into contact with. Then, the flow of the oil is suppressed by the throttle passage 18 of the seal ring 13, and only the gas passes through the upper part of the rod guide 3 and is returned to the reservoir chamber 9 from the gas return passage 11.

(Problems to be Solved by the Invention) However, the above-mentioned conventional hydraulic shock absorber had the following problems.

The seal ring 13 moves up and down within the groove 12 in response to changes in the oil pressure in the inner cylinder 7 due to the expansion and contraction strokes of the hydraulic shock absorber. There was a problem in that each time the vehicle collided with the vehicle, it would make an abnormal noise.

Also, as the seal ring 13 moves upward and the oil inside the inner cylinder 7 flows into the groove 12, the volume inside the cylinder 7 increases accordingly, causing fluctuations or discontinuity in the oil pressure. There was a problem in that it caused disturbances in the damping force characteristics.

The present invention has been made in view of the above problems, and an object thereof is to provide a hydraulic shock absorber that does not generate abnormal noise and can obtain stable damping force characteristics.

(Means for Solving the Problems) The hydraulic shock absorber of the present invention has a seal ring externally fitted onto a piston rod, and a concave groove formed in a circumferential direction on the inner periphery of a rod guide that substantially prevents axial movement. the piston rod and the rod guide, and the seal ring is provided with a throttle passage that communicates the gas return passage with the gap on the inner cylinder side between the piston rod and the rod guide. It is.

(Function) With the above configuration, the seal ring is fitted into the concave groove of the rod guide with its movement in the axial direction substantially restricted, so pressure fluctuations inside the inner cylinder cause the seal ring to move inside the concave groove. It will no longer move around, and will no longer collide with the sides of the groove and produce abnormal noises. Furthermore, since the seal ring does not move upward and the oil inside the inner cylinder does not flow into the groove, the volume inside the inner cylinder does not change significantly, so there is no possibility of fluctuations or discontinuities in the oil pressure. The damping force characteristics will not be disturbed.

(Example) Next, a first example of the present invention will be described based on FIGS. 1 to 3.

The overall structure of the hydraulic shock absorber will be briefly explained based on FIG. It matches. The piston 22 is formed with communication passages 25 and 26 that communicate between the two chambers (upper chamber 23 and lower chamber 24) partitioned by the piston 22, and further includes:
The communication passages 25 and 26 created by the movement of the piston 22
Damping force generating mechanisms 27 and 28 are provided, each of which includes a disc valve or the like that generates a damping force by restricting the flow within.

A reservoir chamber 29 is configured between the inner cylinder 20 and the outer cylinder 21, and a low pressure (for example, 5 kg) is contained in the reservoir chamber 29.
/cta2) gas is enclosed. The inside of the inner cylinder 20 and the inside of the reservoir chamber 29 communicate with each other on the bottom side, and on this bottom side, there is a disk that restricts the flow of oil from the inside of the inner cylinder 2o to the inside of the reservoir chamber 29 and generates a damping force. A damping force generating mechanism 30 consisting of a valve or the like is provided.

Next, a configuration for returning gas leaked into the inner cylinder 2o to the reservoir chamber 29, which is a main part of the present invention, will be explained based on FIGS. 1 and 2.

At the upper end of the piston rod 31 to which the piston 22 is fixed, which protrudes from the shock absorber body 19, a packing cap 32 is fitted into the outer cylinder 21 and fixed by welding. A rod kite 33 that guides the piston rod 31 and an oil seal 34 that prevents oil from leaking to the outside are provided. A bush 35 that directly slides on the piston rod 31 is inserted into the inner periphery of the rod guide 33, and a space 36 between the rod guide 33 and the oil seal 34 and a reservoir are inserted into the outer periphery of the rod guide 33. A notch 37 is formed for communicating with the chamber 29. The space 36 and the notch 37 form a gas return passage 38.
or consists of

A concave groove 39 is formed in the inner circumference of the rod guide 33 between the piston rod 31 and the rod guide 33 in the circumferential direction. An annular seal ring 40 that is slidably fitted onto the piston rod 31 is fitted into the concave groove 39 so that movement in the axial direction is substantially restricted.

That is, the axial dimension of the groove 39 and the seal ring 40
The axial dimensions of the seal ring 40 are approximately equal.
It is said that there is almost no stiffness in the axial direction.

A plurality of grooves 41 and 42 are formed on both end faces of the seal ring 40 and extend in the radial direction.
1.42 and the upper side surface 43 or lower side surface 44 of the groove 39
A throttle passage 45, 46 having a small flow area is formed by this. Note that it is not necessary to reduce the flow area of both of the throttle passages 45 and 46, and it is also possible to reduce the flow area of only one of them so that the oil does not flow.

A check valve mechanism 47 is provided in the space 36 in the middle of the gas return passage 38. The check valve mechanism 47 allows gas to flow from inside the inner cylinder 20 into the reservoir chamber 29,
It has a lip shape that restricts the flow of gas from the inside of the reservoir chamber 29 to the inside of the inner cylinder 20, and is urged and held toward the oil seal 34 by a spring 48.

The operation of the hydraulic shock absorber having the above configuration will be explained.

During the extension stroke of the hydraulic shock absorber, oil fluid flows from the upper chamber 23 to the lower chamber 24 in the inner cylinder 20, and at this time, the damping force generating mechanism 2
7 generates a damping force. At that time, piston rod 3
If there is a shortage of oil in the inner cylinder 20 by the volume of oil that protrudes to the outside, it is supplemented by being supplied from the reservoir chamber 29. Also, during the retraction stroke, oil flows from the lower chamber 24 in the inner cylinder 20 to the upper chamber 23, and at this time, the damping force generating mechanism 28
At the same time, a damping force is generated by the piston rod 3.
The volume of oil that has entered the inner cylinder 20 flows from the bottom side to the reservoir chamber 29, and at this time, a damping force is also generated by the damping force generating mechanism 30 on the bottom side.

By the way, if gas in the reservoir chamber 29 enters the inner cylinder 20 due to vibrations or other causes, during the contraction stroke,
Flows upward from the gap 49 between the piston rod 31 and the bushing 35 together with the gas or oil accumulated above in the upper chamber 23,
It exits upwardly through the throttle passages 45, 46 of the sealing ring 40. At this time, since the flow area of the throttle passages 45 and 46 is made small, almost no oil flows and only gas flows. Then, the gas that has escaped upward is returned to the reservoir chamber 29 by opening the check valve mechanism 47.

In this way, since the seal ring 40 is fitted into the groove 39 of the rod guide 33 with its axial movement substantially restricted, the seal ring 40 does not collide with the side surfaces 43 and 44 of the groove 39 on both sides. It will disappear and no abnormal noise will occur. Furthermore, since the amount of oil flowing toward the seal ring 40 side entering the gap 49 between the piston rod 31 and the bushing 35 is extremely small, the volume within the inner cylinder 20 does not increase or decrease so much that the oil pressure may fluctuate or become discontinuous. It does not significantly affect the damping force characteristics.

Next, a second embodiment of the present invention will be described based on FIG. 4. The second embodiment has almost the same overall configuration as the first embodiment, and differs only in the structure for returning gas to the reservoir chamber 29. Therefore, only that structure will be explained in detail, and the structure will be explained in detail. The same reference numerals are given to members corresponding to those described in the embodiments, and detailed explanations thereof will be omitted.

A step is formed on the upper surface of the rod guide 50, and the retainer 51 is placed over the step to form a groove 53 into which the seal ring 52 is fitted. Therefore, the seal ring 52 can be assembled by placing the seal ring 52 on the stepped portion of the rod guide 50 and then covering the retainer 51.
The work of assembling the groove 53 into the groove 53 becomes easier.

A groove 5 extending in the radial direction is formed on the lower end surface of the seal ring 52.
A plurality of four or more grooves are formed, and this groove and the lower side surface 55 of the groove 53 constitute a throttle passage 56 with a small flow path area.

Further, a throttle passage 57 having a small flow path area is formed at the contact portion of the rod guide 50 with the retainer 51. These throttle passages 56 and 57 form a gap 49 between the piston rod 31 and the rod guide 50 and the gas return passage 3.
8 will be communicated. Note that it is not necessary to reduce the flow area of both of the throttle passages 56 and 57, and it is also possible to reduce the flow area of only one of them so that the oil does not flow.

Note that the operation of this embodiment is the same as that of the first embodiment, so a description thereof will be omitted.

(Effects of the Invention) As described above in detail, the seal ring is fitted into the concave groove of the rod guide with axial movement substantially restricted, and the seal ring is fitted into the groove between the piston rod and the rod guide. A constriction passage is formed that communicates the gap with the gas return passage, and the gap and the gas return passage communicate with each other.
The seal ring does not move and only allows gas to pass through, which can suppress the occurrence of abnormal noise.Furthermore, the amount of oil flowing toward the seal ring is also small due to the gap between the piston rod and rod guide, so it is possible to reduce the amount of oil inside. There is little increase or decrease in the volume inside the cylinder, and there are no fluctuations or discontinuities in the oil pressure, making it possible to stabilize the damping force characteristics.

Moreover, since no parts are added to conventional hydraulic shock absorbers, only the shape is changed, the product cost does not increase.

[Brief explanation of drawings]

FIG. 1 is an enlarged vertical cross-sectional view of the main part of the first embodiment of the hydraulic shock absorber of the present invention, FIG. 2 is a detailed view of section A in FIG. 1, and FIG. 3 is the hydraulic pressure shown in FIG. 1. FIG. 4 is an enlarged vertical sectional view of the main part of the second embodiment of the hydraulic shock absorber of the present invention, and FIG. The top view, FIG. 6 is a detailed view of the B part in FIG. . 21... Outer cylinder 31... Piston rod 38... Gas return passage 40... Seal ring 49... Gap No. 1 250-

Claims (1)

[Claims] (1) A gas return passage that communicates the gap between the piston rod and the rod guide that guides the piston rod with the reservoir chamber between the inner and outer cylinders, and a gas return passage that is arranged between the piston rod and the rod guide to remove the gas in the inner cylinder. A hydraulic shock absorber comprising a seal ring for allowing gas to flow into the gas return passage, and a check valve mechanism provided in the middle of the gas return passage and allowing gas to flow only from the inside of the inner cylinder to the reservoir chamber side. , the seal ring is fitted onto the piston rod and fitted into a groove formed in a circumferential direction on the inner periphery of the rod guide so as to substantially restrict movement in the axial direction; A hydraulic shock absorber characterized in that a seal ring is provided with a throttle passage that communicates a gap on the inner cylinder side between the piston rod and the rod guide with the gas return passage.