JPH04102737A - Hydraulic buffer - Google Patents

Abstract

PURPOSE:To obtain a stable damping force the switching to a compression cycle by installing a valve mechanism which closes a communication passage in an extension cycle by a groove and a piston ring and opens the communication passage and allows two chambers to communicate in the switching to a contraction cycle. CONSTITUTION:In the switching from an extension cycle to a contraction cycle, a piston ring 21 is held on the inner peripheral surface of an inner cylinder 12 by the frictional force, and the piston ring 21 is separated instantly from the side surface part 20b of a groove 20 by the change of the sliding direction of a piston 13, and a communication passage 20a for the communication between the upper chamber 12a of the cylinder and the lower chamber 12b of the cylinder is opened. Accordingly, the oil liquid in the upper chamber 12a of the cylinder speedily flows into the lower chamber 12b of the cylinder, and pressures in the upper chamber 12a of the cylinder and the lower chamber 12b of the cylinder become nearly equal, and the shift of the piston 13 by the pressure difference between two chambers in the inner cylinder 12 is prevented, and a state damping force is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic shock absorber provided in a suspension system of a vehicle such as an automobile.

(Prior Art) Conventionally, a hydraulic shock absorber having a double cylinder structure as shown in FIG. 2, for example, is known. This hydraulic shock absorber will be explained based on the drawings.

In FIG. 2, a piston 5 with a rod 4 connected thereto is slidably fitted into the inner cylinder 1 of a cylinder 3 having a double cylinder structure consisting of an inner cylinder 1 and an outer cylinder 2. The interior of the inner cylinder 1 is divided into an upper cylinder chamber 3a and a lower cylinder chamber 3b. In addition, a reservoir chamber 3c is formed between the inner and outer cylinders, and a cylinder upper chamber 3a and a cylinder lower chamber 3.
b is filled with oil liquid, and the reservoir chamber 3c is filled with oil liquid and gas. The piston 5 is provided with a communication hole 6 that communicates the cylinder upper chamber 3a and the cylinder lower chamber 3b.
The communication hole 6 is provided with a damping force generating mechanism 7 and a check valve mechanism 8 that opens and closes depending on the pressure difference between the two chambers in the inner cylinder 1 and allows flow from the cylinder lower chamber 3b to the cylinder upper chamber 3a. A base valve mechanism 9 is provided on the bottom side of the cylinder 3 so as to communicate the cylinder lower chamber 3b and the reservoir chamber 3C. The base valve mechanism 9 has a damping force generating mechanism 10.
A check valve mechanism 11 is provided which opens and closes depending on the pressure difference between the cylinder lower chamber 3b and the reservoir chamber 3c and allows flow from the reservoir chamber 5c to the cylinder lower chamber 5b.

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

In the case of the extension stroke, the oil in the upper cylinder chamber 3a is pressurized and flows into the lower cylinder chamber 3b through the communication hole 6. At this time, the check valve mechanism 8 closes and the damping force generating mechanism 7 generates a damping force. Further, the oil liquid corresponding to the amount of the rod 4 withdrawn from the cylinder 3 opens the check valve mechanism 11 of the base valve mechanism 9 and flows into the cylinder lower chamber 3b from the reservoir chamber 3c with almost no resistance.

In the case of the contraction stroke, the oil in the cylinder lower chamber 3b is pressurized, opens the check valve mechanism 8, and flows into the cylinder upper chamber 3a through the communication hole 6 with almost no resistance. The amount of oil that has entered the chamber 3a flows into the cylinder lower chamber 3b.
The water flows from the base valve mechanism 9 to the reservoir chamber 3C. At this time, the check valve mechanism 11 closes and a damping force is generated by the damping force generating mechanism IO.

In this way, damping force is generated by the damping force generating mechanism 7 of the piston 5 during the extension stroke, and by the damping force generating mechanism 10 of the base valve mechanism 9 during the retracting stroke.

(Problems to be Solved by the Invention) However, the conventional hydraulic shock absorber described above has the following problems.

The check valve mechanism 8 of the piston 5 opens when the pressure in the lower cylinder chamber 3b becomes higher than the pressure in the upper cylinder chamber 3a during the contraction stroke.

However, during the extension stroke, the upper cylinder chamber 3a is pressurized and has a higher pressure than the lower cylinder chamber 3b, and this pressure presses the check valve mechanism 8 into the closed state, so that it contracts from the extension stroke. Even when the stroke is switched, the check valve mechanism 8 is not opened immediately. Therefore, since the check valve mechanism 8 is in a closed state immediately after switching from the extension stroke to the contraction stroke, the piston 5 is pressed toward the cylinder lower chamber 3b by the pressure in the cylinder upper chamber 3a, and the rod 4 is shortened. Therefore, there is a problem that the damping force tends to become unstable.

The present invention has been made in view of the above points, and an object of the present invention is to provide a hydraulic shock absorber that can provide a stable damping force when switching from an extension stroke to a contraction stroke.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a structure in which a piston that divides the inside of the inner cylinder into two chambers is slidable in the inner cylinder of a cylinder having a dual-tube structure. A base valve mechanism is provided that fits into the piston and generates a damping force during an extension stroke, and connects the inside of the inner cylinder and the inside of the outer cylinder on the bottom side of the cylinder to generate a damping force during a contraction stroke. In the hydraulic shock absorber, a groove is formed on the outer periphery of the piston, a piston ring movable in the axial direction of the piston is provided in the groove, and a communication passage that allows the two chambers to communicate with each other is provided in the groove. The groove and the piston ring constitute a valve mechanism that closes the communication passage during the extension stroke and opens the communication passage when switching from the extension stroke to the contraction stroke to communicate the two chambers with each other. shall be.

(Function) With this configuration, when the sliding direction of the piston changes from the extension stroke to the contraction stroke, the piston ring is held in the inner cylinder by frictional force, so that the piston slides inside the groove. The communication passage is opened and the two chambers separated by the piston are communicated with each other, and the pressures in the two chambers immediately become almost equal.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 shows the main parts of the hydraulic shock absorber of this embodiment. Note that the left side of the figure shows the extension stroke, and the right side shows the contraction stroke.

In FIG. 1, a piston 13 is slidably fitted into an inner cylinder 12 of a cylinder with a double cylinder structure.
The interior of the inner cylinder 12 is divided into an upper cylinder chamber 12a and a lower cylinder chamber 12b. One end of a rod 14 is fixed to the piston 13 with a nut 15. The piston 13 has a cylinder upper chamber 12a and a cylinder lower chamber 12b.
Communication holes 16 and 17 are drilled through which the two are communicated with each other. A disc valve mechanism 18 is provided on the end surface of the piston 13 on the cylinder lower chamber 12b side, which controls the flow of oil in the communication hole 16 during the extension stroke to generate a damping force. The disc valve mechanism 18 has a communication hole 16 and a cylinder lower chamber 12b.
A well-known fixed orifice (not shown) is provided to provide constant communication between the two. In addition, the cylinder upper chamber 1 of the piston 13
On the end face on the 2a side, there is a reverse valve that opens and closes depending on the pressure difference between the cylinder upper chamber 12a and the cylinder lower chamber 12b, allows oil to flow through the communication hole 17 with almost no resistance during the contraction stroke, and closes the communication hole 17 during the extension stroke. A stop valve mechanism 19 is provided. Further, a groove 20 having a rectangular cross section is formed on the outer periphery of the piston 13, and a piston ring 21 interposed between the inner cylinder 12 and the piston 13 is provided within the groove 20. The piston ring 21 presses its outer circumferential surface against the inner circumferential surface of the inner cylinder 12 by its own elastic force, so as to bring the piston ring 21 into liquid-tight and slidable contact therewith. The width and depth of the groove 20 are set larger than that of the piston ring 21, so that the piston ring 21 can move within the groove 20 in the axial direction of the piston 13. Cylinder upper chamber 12a and cylinder lower chamber 1 inside
A communication path 20a is formed to communicate with 2b. A side surface 20b of the groove 20 on the cylinder lower chamber 12b side and an end surface 21a of the piston ring 21 on the cylinder lower chamber 12b side.
can be brought into contact with each other in a liquid-tight manner, and when the side surface portion 20b and the end surface 21a come into contact with each other, the communicating path 20a is closed. In addition, the cylinder upper chamber 1 of the piston ring 21
An uneven portion 21b is formed on the end surface of the groove 2a, and the uneven portion 21b is formed on the side surface 20 of the groove 20 on the cylinder upper chamber 12a side.
When it comes into contact with c, an oil passage is formed in the contact part and the communication passage 2
0a is open. In this way, the groove 20 and the piston ring 21 constitute a valve mechanism that can communicate the two chambers in the inner cylinder 12 with each other. Instead of providing an uneven portion on the end surface on the chamber 12a side, an uneven portion may be provided on the side surface of the groove 20 on the cylinder upper chamber 12a side.

Furthermore, although not shown in the drawings, the hydraulic shock absorber of this embodiment has an outer cylinder provided outside the inner cylinder 12 to form a reservoir chamber, similar to the conventional example shown in FIG. A base valve mechanism is provided on the bottom side of the cylinder 12 so as to communicate between the cylinder lower chamber 12b and the reservoir chamber. This base valve mechanism is provided with a damping force generating mechanism and a check valve mechanism that opens and closes depending on the pressure difference between the reservoir chamber and the cylinder lower chamber 12b and allows flow from the reservoir chamber to the cylinder lower chamber 12b. The inner cylinder 12 is filled with oil, and the reservoir chamber is filled with oil and gas.

The operation of this embodiment configured as above will be explained next.

During the extension stroke of the hydraulic shock absorber, the pressure within the cylinder upper chamber 12a increases, the check valve mechanism 19 closes, and the communication hole 17 is closed. Further, the piston ring 21 is brought into fluid-tight contact with the side surface 2 (lb) of the groove 20 due to the frictional force with the inner circumferential surface of the inner cylinder 12 and the pressure difference between the cylinder upper chamber 12a and the cylinder lower chamber 12b. It slides together with the piston 13.

Therefore, as the piston 13 slides, the oil in the cylinder upper chamber 12a flows through the communication hole 16, passes through the disc valve mechanism 18, and flows into the cylinder lower chamber 12b.

On the other hand, the amount of oil that the rod 14 has withdrawn from the cylinder upper chamber 12a is transferred to the check valve mechanism (not shown) of the base valve mechanism.
It opens and flows from the reservoir chamber (not shown) into the cylinder lower chamber 12b with almost no resistance. In this way, a damping force is generated by the oil flowing through the disc valve mechanism 18.

During the contraction stroke of the hydraulic shock absorber, the pressure inside the cylinder lower chamber 12b increases, the check valve mechanism 19 opens, and the cylinder lower chamber 1
The oil inside 2b flows into the cylinder upper chamber 12a with almost no resistance. Further, the piston ring 21 slides together with the piston 13 while being in contact with the side surface 20c of the groove 20 due to the frictional force with the inner peripheral surface of the inner cylinder 12 and the pressure difference between the cylinder upper chamber 12a and the cylinder lower chamber 12b. . and,
The oil in the cylinder upper chamber 12a flows into the cylinder lower chamber 12b through an oil passage formed at the abutting portion between the concavo-convex portion 21b of the piston ring 21 and the side surface 20c with almost no resistance. Therefore, when the rod 14 enters the cylinder upper chamber 12a, the oil in the cylinder lower chamber 12b passes through the base valve mechanism (not shown) and enters the reservoir chamber (
(not shown). At this time, the reverse valve mechanism of the base valve mechanism closes and a damping force is generated by the damping force generating mechanism of the base valve mechanism.

When switching from extension stroke to compression stroke, piston ring 2
1 is held on the inner circumferential surface of the inner cylinder 12 by frictional force, so that when the sliding direction of the piston 13 changes, the piston ring 21 immediately separates from the side surface 20b of the groove 20, thereby separating the cylinder upper chamber 12a and the cylinder. A communication path 20a communicating with the lower chamber 12b is opened. Therefore, the oil in the cylinder upper chamber 12a quickly flows into the cylinder lower chamber 12b, and the pressures in the cylinder upper chamber 12a and cylinder lower chamber 12b become almost equal, so that the pressure difference between the two chambers in the inner cylinder 12 A stable damping force can be obtained without the piston 13 moving.

In this embodiment, the piston 13 is provided with the communication hole 17 and the check valve mechanism 19, but the same effect can be obtained by using only the groove 20 and the piston ring 21. can also be omitted.

Furthermore, in this embodiment, the concavo-convex portion 21b is provided on the end face of the piston ring so that the communication passage 20a is always open during the contraction stroke, but the concave-convex portion 21b is omitted and the concave-convex portion 21b is provided on the end face of the piston ring. Communication path 20 only when switching
a opens and immediately makes the pressures in the upper cylinder chamber 12a and lower cylinder chamber 12b almost equal, and the subsequent contraction stroke is as follows:
The check valve 19 of the communication hole 17 may be opened (by which the cylinder upper chamber 12a and the cylinder lower chamber 12b may be communicated with each other).

(Effects of the Invention) By having the hydraulic shock absorber of the present invention configured as detailed above, the piston ring is held in the inner cylinder by frictional force when switching from the extension stroke to the contraction stroke, so that the piston ring is held in the inner cylinder by frictional force. Due to the sliding, a communication path in the groove is opened, and the two chambers separated by the piston communicate with each other, so that the pressures in the two chambers become almost equal immediately. As a result, when switching from the extension stroke to the contraction stroke, the discontinuity in force due to the pressure difference between the two chambers partitioned by the piston is eliminated, and a stable damping force can be obtained, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the main part of an embodiment of the present invention; FIG. 12...Inner cylinder 12a... Cylinder upper chamber 12b...Cylinder lower chamber 13...Piston 16, 17...Communication hole 18... Disc valve mechanism 20...groove 20a...Communication path 21... Piston ring

Claims (1)

[Claims] (1) A piston that divides the inside of the inner cylinder into two chambers is slidably fitted into the inner cylinder of a cylinder with a double inner and outer cylinder structure, and a piston valve mechanism is provided that generates a damping force during the extension stroke of the piston. A hydraulic shock absorber is provided with a base valve mechanism on the bottom side of the cylinder that connects the inside of the inner cylinder and the inside of the outer cylinder and generates a damping force during a contraction stroke, a groove is formed on the outer periphery of the piston, A piston ring movable in the axial direction of the piston is provided in the groove, a passageway is provided in the groove that can communicate the two chambers, and the groove and the piston ring close the communication path during an extension stroke. A hydraulic shock absorber comprising a valve mechanism that opens the communication passage and communicates the two chambers with each other when switching from an extension stroke to a contraction stroke.