JP2002310217A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder for a shock absorber. SOLUTION: The cylinder for the shock absorber has a cylinder body with both ends opening, and a peripheral groove is formed on the inner side of the cylinder body. The cylinder also has a first cap to be screwed and engaged with one opening end of the cylinder body. The first cap has a check valve, which allows injection of a gas into the cylinder body from the outside but prevents leakage of the gas to the outside. The cylinder also has a second cap to be screwed and engaged with the other opening end of the cylinder body, and a through hole is formed on the second cap for supporting a piston rod slidably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to vehicle shock absorbers with wheels, and more particularly to automotive shock absorbers.

[0002]

2. Description of the Related Art As a component of a vehicle suspension, a shock absorber for damping the vibration of a vehicle has been conventionally known. As one type of such a shock absorber, a so-called de-carbon type or monotube type is used. Shock absorbers are known.

[0003] In this de-Carbon shock absorber, for example, a tube or cylinder whose upper end is slidably attached to a piston rod attached to a vehicle body is divided into three chambers or chambers.
That is, the cylinder is divided into a first chamber and a second chamber by a piston attached to the lower end of the piston rod, and the second chamber is slidably mounted in the cylinder below the piston of the piston rod. The free piston has two more chambers, a second chamber and a third chamber.
Divided into rooms.

[0004] The first chamber and the second chamber of the cylinder are filled with oil, and the third chamber is filled with a gas, for example, nitrogen gas at a predetermined pressure. The cylinder in which each chamber is filled with an appropriate fluid in this manner is attached to the suspension arm via various connecting members attached to its lower part.

[0005] The structure of the conventional shock absorber and its assembling method are as follows.

That is, as shown in FIG.
The carvone shock absorber has a cylinder,
This cylinder comprises a cylinder body 1 having an upper open end and a lower closed end, and an upper lid 23 described later. Circular grooves 2 and 3 are formed on the inner surface of the upper end of the cylinder body 1.

In order to fill the gas in such a cylinder, a gas filling jig indicated generally by reference numeral 10 is used. This gas filling jig 10 is entirely cylindrical.
A main body 11 having a lower surface 11a mounted on an upper open end surface of the cylinder main body 1;
And a lower skirt portion 12 extending downward from the lower surface 11a of the main body 11 so as to cover the upper outer surface of the cylinder main body 1 when attached to the main body. The main body 11 has a top wall 13,
The top wall 13 has a through hole 14 through which the piston rod 20 of the shock absorber can pass. The main body 11 of the gas filling jig 10 is also provided with a gas filling hole 15 penetrating the peripheral wall of the main body 11, and the inner surface of the main body 11 is formed flush with the inner surface of the cylinder main body 1.
Further, an annular groove 16 is formed on the lower surface 11a of the main body 11 inward of the lower skirt portion 12 in the radial direction.
Is provided with an O-ring 17.

When filling the cylinder with gas,
As shown in FIG. 1, the gas filling jig 10 is fitted to the upper end of the cylinder body 1, and the free piston 21 and the piston rod 20 are inserted into the body 11 of the gas filling jig 10 above the gas filling hole 15. Position. Free piston 21
An O-ring 21 a for slidably sealing the inner surface of the cylinder (and also the inner surface of the main body 11 of the gas filling jig 10) is attached to the outer circumference of the cylinder, and a piston 20 a is attached to the lower end of the piston rod 20. I have. A piston ring for slidably sealing the inner surface of the cylinder (and thus the inner surface of the main body 11 of the gas filling jig 10) is attached to the outer periphery of the piston 20a, but is not shown.

After fitting the gas filling jig 10 into the cylinder body 1, a predetermined amount of gas G is supplied from the gas filling hole 15.
Next, by moving the piston rod 20 downward, the free piston 21 located below the piston rod 20 is moved downward in the cylinder body 1 to compress the gas G previously charged to a desired pressure.

Next, as shown in FIG. 2, the gas filling jig 10 is removed from the cylinder body 1 and the cylinder body 1 is removed.
The C-ring 22 is fitted into the circumferential groove 2. This C ring 22
Constitutes a stopper for the piston 20a and prevents the piston 20a from moving upward beyond the C-ring 22.

Subsequently, the oil F is poured into the cylinder body 1 up to its upper end. This oil F is used for the piston 2
Orifice formed in the piston 20a as well as in the portion of the cylinder body 1 located above
(Not shown), and a portion of the cylinder body 1 located below the piston 20a through communication holes formed in the piston rod 20 above and below the piston 20a and a bypass passage extending between these communication holes. Also meet.

Then, as shown in FIG. 3, the upper lid 23 constituting the cylinder is fitted into the upper open end of the cylinder body 1. A through hole is formed in the center of the upper lid 23 to slidably support the piston rod 20, and an O-ring 24 for sealing the piston rod 20 is attached to the inner surface of the through hole. An O-ring 25 for sealing the inner surface of the cylinder body 1 is attached to the outer periphery of the upper lid 23. Then, the upper lid 23 is attached to the piston rod 20.
The upper cover 23 is pushed into the cylinder main body 1 by passing through the through hole of
Push down below. Since the oil F contained in the cylinder body 1 is not considered to be compressed even when the upper lid 23 is pushed down, the free piston 21 is temporarily pushed down by pushing down the upper lid 23, whereby the gas is further reduced. Pressurized.

Next, a C ring 26 is fitted into the circumferential groove 3.
The C ring 26 constitutes a stopper for the upper lid 23 and prevents the upper lid 23 from moving upward beyond the C ring 26.

Next, the downward force applied to the piston rod 20 to release the free piston 21 downward is released. Then, the pressurized gas G acts on the free piston 21 so as to push up the slidable free piston 21. As a result, the free piston 21
Acts to pressurize the oil. However, the oil pressurized in this manner, however, is considered that the upper lid 23 is fixed by the C-ring 26 and the oil itself is not compressed. Acts on the piston rod 20 so that 20 is pushed out of the cylinder body 1.

The gas pressurized under the desired pressure always acts on the free piston 21 so as to pressurize the oil.

[0016]

However, in the de-Carbon shock absorber and the assembling method thereof described above, first, a gas filling jig 10 is required for gas filling. Since the gas is introduced into the cylinder main body 1 from a position higher than the upper end of the cylinder main body 1, the gas distributed over the entire cylinder main body 1 is compressed when the gas is compressed. There is a problem that the gas has to be compressed toward the lower part, so that the volume change of the gas is large, and it is difficult to accurately compress the gas to a desired pressure value.

Further, when the disassembly and maintenance is required due to aging, in the above-described structure of the shock absorber and the cylinder, for example, when the gas is refilled, the gas chamber cannot be directly accessed. Even components not directly related to gas filling had to be removed.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to reduce a volume change at the time of gas compression and to easily disassemble and maintain a cylinder, a shock absorber, and It is an object of the present invention to provide a method of assembling a shock absorber.

[0019]

In order to achieve the above object, a cylinder for a shock absorber according to the present invention has a cylinder body with both ends open, and a circumferential groove is formed on an inner surface of the cylinder body. A first lid adapted to be threadedly engaged with one of the open ends of the body, the first lid allowing externally injecting gas into the cylinder body; However, it has a check valve for preventing gas from leaking out of the cylinder body to the outside, and has a second lid adapted to be screw-engaged with the other of the open ends of the cylinder body. The second lid has a through hole for slidably supporting the piston rod.

According to the shock absorber cylinder having the above-described structure, the circumferential groove for mounting the C-ring for restricting the movement of the free piston is formed. Therefore, the C-ring is mounted on the circumferential groove to limit the movement of the free piston. Meanwhile, the gas can be charged into the gas chamber through the check valve of the first lid. Further, since the first lid and the second lid can be screw-engaged with the open end of the cylinder body, the cylinder can be easily disassembled and maintained. Furthermore, the first
Since the check valve is provided on the lid, the gas can be easily refilled.

According to another aspect of the present invention, there is provided a shock absorber including a cylinder and a piston rod having a piston slidably supported by the cylinder, wherein the piston is connected to the cylinder. A first chamber and a second chamber, an orifice communicating the first chamber and the second chamber, and a free piston slidably supported by the cylinder; Subdividing the second chamber of the cylinder into the second chamber and the third chamber, the first chamber and the second chamber are filled with oil, and the third chamber is filled with gas; A shock absorber, wherein the cylinder is open at both ends,
A cylinder body having a circumferential groove formed on an inner surface thereof; a C-ring fitted in the circumferential groove of the cylinder body for restricting movement of the free piston toward the piston; and an open end of the cylinder body. A first lid adapted to be screwed into one of the third chambers, wherein the first lid allows gas to be injected from the outside into the third chamber, A second check valve for preventing gas from leaking out of the cylinder body; and a second lid adapted to be threadedly engaged with the other of the open ends of the cylinder body. The lid is formed with a through-hole for slidably supporting the piston rod.

According to the shock absorber having the above structure, the first lid and the second lid can be screw-engaged with the open end of the cylinder body, so that the shock absorber can be easily disassembled and maintained. In addition, since the first lid is provided with the check valve, the gas can be easily refilled.

In the present invention, it is preferable that at least one of the ends of the C-ring is bent inward in the radial direction.

Further, in order to achieve the above object, a method of assembling a shock absorber according to the present invention includes a cylinder and a piston rod having a piston slidably supported by the cylinder, wherein the piston is: The cylinder is divided into a first chamber and a second chamber, an orifice communicating the first chamber and the second chamber is provided, and a free piston slidably supported by the cylinder is provided. But the second chamber of the cylinder and the second chamber,
A method for assembling a shock absorber, wherein the shock absorber is divided into a third chamber, the first chamber and the second chamber are filled with oil, and the third chamber is filled with gas. A C-ring for restricting the movement of the free piston is fitted into the circumferential groove of the cylinder body having a circumferential groove formed on the inner surface, and the free piston is inserted into the cylinder body. A first lid is screw-engaged with one of the open ends of the cylinder body so as to be positioned between the cylinder body and the inside of the cylinder body via a check valve provided on the first lid. The cylinder body is filled with gas, oil is poured into the cylinder body from the other of the open ends of the cylinder body, and the piston rod is inserted into the cylinder body from the other open end of the cylinder body. Type, the second lid, by passing the through hole in the piston rod, threaded engagement to the other open end of the cylinder body, characterized in that it comprises.

According to the above method, the gas can be charged into the third chamber through the check valve of the first lid while restricting the movement of the free piston by the C-ring. Need not be compressed by the free piston and piston rod.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In this embodiment, the present invention is applied to a cylinder for a de-Carbon shock absorber in which an upper end of a piston rod is attached to a vehicle body and a lower part of the cylinder is attached to a suspension arm.

As shown in FIG. 4, a cylinder according to the present invention, generally designated by the symbol C, has a cylinder body 30 having an upper open end 31 and a lower open end 32.

The lower end of the cylinder body 30 has a smooth inner surface portion 33, and the female screw 3 is provided above the smooth inner surface portion 33.
4 is cut off. Similarly, the upper end of the cylinder body 30 has a smooth inner surface 35, and a female screw 36 is cut below the smooth inner surface 35. A circumferential groove 37 is formed in the lower inner surface of the cylinder body 30.

The cylinder C is also provided with a cylinder body 30.
Lid 4 adapted to be screw-engaged with lower open end 32 of
Has zero.

The lower lid 40 has an enlarged base 41 having an abutment surface 41a that comes into contact with the lower end surface of the cylinder body 30 when the lower lid 40 is attached to the cylinder body 30, and a contraction base extending upward from the enlarged diameter base 41. And a diameter cylindrical portion 42. On the outer surface of the upper end of the reduced-diameter cylindrical portion 42, a male screw 43 adapted to engage with the female screw 34 of the cylinder body 30 is cut. A smooth outer surface portion 44 is formed below the male screw 43, and a circumferential groove 45 is formed in the smooth outer surface portion 44, and an O-ring 46 is attached to the circumferential groove 45.

Although the lower lid 40 allows gas to be injected into the cylinder C from the outside, the cylinder C
A check valve 47 for preventing gas from leaking from the inside to the outside is provided.

The check valve 47 is attached to an internal passage 49 of a cylindrical projecting engaging portion 48 extending downward from the enlarged diameter base portion 41. Since the check valve 47 has a conventional structure that can be opened by displacing the shaft 47a against a spring, its details will not be described here. The internal passage 49 to which the check valve 47 is attached communicates with a communication passage 50 formed in the enlarged diameter base 41, and the communication passage 50 also communicates with the internal passage 51 of the reduced diameter cylindrical portion 42. An external thread 52 that can be screw-engaged with a gas filling device (not shown) is formed on the outer surface of the cylindrical projecting engagement portion 48. Thus, the gas filling device is screw-engaged with the male screw 52 of the cylindrical projecting engagement portion 48 of the lower lid 40, and the shaft 47a of the check valve 47 is spring-loaded (not shown) by the gas filling device (operating rod). 4), the cylinder body 30 is pushed upward when viewed in FIG.
9, communication with the gas filling device is made via the communication passage 50 of the enlarged diameter base portion 41 and the internal passage 51 of the reduced diameter cylindrical portion 42.

The cylinder C further includes a cylinder body 30
Lid 5 adapted to be screw-engaged with upper open end 31 of
Has zero.

The upper lid 50 has a diameter-increasing base 51 having a contact surface 51a that comes into contact with the upper end surface of the cylinder body 30 when the lid 50 is attached to the cylinder main body 30, and a diameter-reducing base extending downward from the diameter expansion base 51. And a cylindrical portion 52. On the outer surface of the lower end of the reduced diameter cylindrical portion 52, a male screw 53 adapted to engage with the female screw 36 of the cylinder body 30 is cut. A smooth outer surface portion 54 is formed above the male screw 53, a peripheral groove 55 is formed in the smooth outer surface portion 54, and an O-ring 56 is attached to the peripheral groove 55.

The upper lid 50 is also formed with a through hole 57 at the center thereof for slidably supporting the piston rod PR (see FIGS. 6 and 7). A peripheral groove 58 is formed in the through hole 57, and an O-ring 59 for sealing the outer surface of the piston rod PR is attached to the peripheral groove 58.

Next, a method for filling the cylinder C with gas and oil will be described.

First, C is inserted into the circumferential groove 37 of the cylinder body 30.
The ring 60 is fitted. When the C ring 60 is fitted in the circumferential groove 37, it expands or recovers radially outward of the cylinder main body 30, and has an inner diameter smaller than the inner diameter of the cylinder main body 30. Also,
As shown in FIG. 8, the end of the C-ring 60 is bent inward in the radial direction to form an engagement end 60a.

Next, the free piston FP is inserted into the cylinder body 30 from the lower open end 32. The free piston FP has a conventional structure provided with an O-ring 61 for sealing the inner surface of the cylinder body 30 on the outer periphery thereof.

Subsequently, the lower cover 40 is threadedly engaged with the lower open end 32 of the cylinder body 30 by screwing the male screw 43 of the lower cover 40 into the female screw 34 of the cylinder body 30. The lower lid 40 is screwed into the cylinder body 30 until the O-ring 46 contacts the smooth inner surface 33 of the cylinder body 30 and the contact surface 41a contacts the lower end surface of the cylinder body 30.

Next, the cylindrical projecting engagement portion 48 of the lower lid 40
After screw-engaging a gas filling device (not shown) provided with a gas pressure gauge, gas is supplied to the gas chamber GC constituted by the free piston FP, the lower lid 40 and the cylinder body 30 by the gas filling device. Supply. In supplying the gas, it goes without saying that the cylindrical projecting engagement portion 48 of the lower lid 40 and the gas filling device (not shown) are sealed by a suitable sealing means. With the filling of the gas, the free piston FP is moved upward in the cylinder body 30 as viewed in FIG. 5, but this upward movement of the free piston FP is caused by the movement of the free piston FP attached to the cylinder body 30. It is limited by a C-ring 60 having an inner diameter smaller than the outer diameter. Subsequently, a gas is supplied to the gas chamber GC by a gas filling device (not shown), and the gas in the gas chamber GC is set to a desired pressure. Gas chamber GC
After setting the gas at the desired pressure, the gas filling device (not shown) is removed from the lower lid 40. According to this gas filling method, a change in volume of the charged gas can be avoided.

Next, oil F is poured from the upper open end 31 into the cylinder body 30 to the upper end thereof.

Subsequently, as shown in FIG. 6, a piston rod PR having a piston P at a lower portion is inserted into the cylinder body 30 from the upper open end 31. This piston rod PR has an orifice OR formed in the piston as described in the section of the prior art, and optionally, communication holes formed in the piston rod above and below the piston, and a bypass passage is formed between these communication holes. Is of a conventional construction, and therefore will not be described in detail here. Therefore, when the piston rod PR is inserted into the cylinder body 30,
The oil below the piston P moves above the piston P through an orifice OR or the like. When the piston rod PR is inserted into the cylinder body 30, the oil F poured into the cylinder body 30 overflows from the volume of the inserted piston rod PR and the upper open end 31 of the cylinder body 30.

The piston rod PR is connected to the cylinder body 30.
Of the cylinder body 30 by passing the through hole 57 through the piston rod PR.
, And the male screw 53 of the upper lid 50 is screwed into the female screw 36 of the cylinder body 30 so that the upper lid 5
0 is screwed into the upper open end 31 of the cylinder body 30. The upper cover 50 is screwed into the cylinder body 30 until the O-ring 56 contacts the smooth inner surface 35 of the cylinder body 30 and the contact surface 51a contacts the upper end surface of the cylinder body 30.

When the upper lid 50 enters the cylinder main body 30, the oil F in the cylinder main body 30 further overflows from the upper open end 31, but the O-ring 56 of the upper lid 50 comes into contact with the smooth inner surface 35 of the cylinder main body 30. The oil F starts to be pressurized by the upper lid 50 from the moment when is sealed. However, since the volume of the oil F is not substantially compressed even if it is pressurized, the free piston FP is pushed down by pushing down the upper lid 50, and the gas G is further pressurized.

After the upper lid 50 is moved downward until the contact surface 51a of the upper lid 50 comes into contact with the upper end surface of the cylinder body 30, the gas under pressure is released so as to push up the slidable free piston FP. Acts on piston FP,
As a result, the free piston FP acts to pressurize the oil. The oil thus pressurized, however, has the upper lid 50 fixed to the upper open end 31 of the cylinder body 30, and the oil itself is not substantially compressed, so that the upper lid 50 (the O-ring 56) Acts on the piston rod PR so as to push out the moved volume and slidable piston rod PR from the cylinder body 30, and the piston rod PR moves upward and finally comes into contact with the upper lid 50.

However, the piston rod PR is
, The free piston FP is still held under pressure, that is, the C-ring 6
It is kept in a state of moving away from 0 below. That is,
The gas in the gas chamber GC always acts on the free piston so as to pressurize the oil. Thus, this gas pressure, which always acts to pressurize the oil, is generated in the cylinder body 30 when the upper lid 50 is inserted into the cylinder body 30.
It is determined by a function of the position of the piston rod PR (relative to the cylinder body 30) and the amount by which the O-ring (of the O-ring 56) is moved in the cylinder body 30.

In the cylinder C having the above structure, the gas chamber GC
When the gas pressure of the gas chamber drops and the original performance of the shock absorber cannot be exhibited,
When the gas needs to be refilled into the gas chamber GC, the gas chamber G is filled in the same manner as described above.
C can be refilled with gas. That is, the lower lid 4
The gas chamber GC can be easily refilled with gas at a desired pressure via a gas filling device (not shown) provided with the gas pressure gauge described above, which is connected to the cylindrical projecting engagement portion 48 of FIG. it can. Therefore, when refilling the gas into the gas chamber GC,
Upper lid 50 and piston rod PR irrelevant to gas chamber GC
Need not be removed from the cylinder body 30, and there is no need to remove oil from the cylinder body 30.

Further, in the cylinder C having the above-described structure, the lower lid 40 and the upper lid 50 are merely engaged with the cylinder body 30 by screws, and can be easily detached.
Disassembly and maintenance of the cylinder C is easy, and the end of the C ring 60 constitutes an engagement end 60a bent inward in the radial direction. The C ring 60 can be easily removed from the circumferential groove 37 of the cylinder body 30 by engaging with the portion 60a.

The present invention is not limited to the above-described embodiment, but allows various modifications as described below.

For example, in the above embodiment, the shock absorber using a cylinder has been described with an example in which the upper end of the piston rod is attached to the vehicle body and the lower part of the cylinder is attached to the suspension arm. Of course, it can be used for a so-called inverted shock absorber in which the lower end of the piston rod is attached to the suspension arm and the upper part of the cylinder is attached to the vehicle body.

In the above embodiment, the engagement end portion 60a of the C ring 60 is formed in a U-shape.
Any shape may be used as long as it is bent inward in the radial direction and can be easily removed from the circumferential groove 37 of the cylinder body 30 with the tip of a tool such as a screwdriver.

[0052]

As described above, the present invention can provide a cylinder, a shock absorber, and a method of assembling a shock absorber, which can reduce a change in volume during gas compression and can be easily disassembled and maintained. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a state in which a gas filling jig is attached to a cylinder body of a conventional shock absorber.

FIG. 2 is a schematic sectional view showing a state in which gas and oil are filled in a cylinder body of a conventional shock absorber.

FIG. 3 is a schematic sectional view showing a state in which an upper lid is attached to the cylinder main body of FIG. 2;

FIG. 4 is an exploded schematic sectional view showing an embodiment of the cylinder of the present invention.

FIG. 5 is a schematic cross-sectional view showing a step of filling gas into the cylinder body of FIG.

FIG. 6 is a schematic sectional view showing a step of filling the cylinder body of FIG. 4 with oil;

FIG. 7 is a schematic sectional view showing a state in which an upper lid is attached to the cylinder body of FIG. 4;

FIG. 8 is an enlarged schematic plan view of a C-ring attached to the cylinder body of FIG.

[Explanation of symbols]

 C cylinder 30 cylinder body 31 upper open end 32 lower open end 37 peripheral groove 40 lower lid (first lid) 47 check valve 50 second lid (upper lid) 57 through hole

Claims (4)

[Claims] 1. A cylinder for a shock absorber, comprising: a cylinder body having both ends opened; a circumferential groove formed on an inner surface of the cylinder body; and a screw on one of the open ends of the cylinder body. Having a first lid adapted to be engaged, wherein the first lid allows gas to be injected into the cylinder body from the outside, but gas leaks from the cylinder body to the outside; Having a second lid adapted to be threadedly engaged with the other one of the open ends of the cylinder body, the second lid having a piston rod. A through hole for slidably supporting the cylinder. 2. A cylinder, comprising: a cylinder; and a piston rod having a piston slidably supported by the cylinder, wherein the piston divides the cylinder into a first chamber and a second chamber; Chamber and the second
An orifice communicating with the chamber; and a free piston slidably supported by the cylinder, the free piston reconnecting the second chamber of the cylinder to the second chamber and the third chamber. A shock absorber in which the first chamber and the second chamber are filled with oil and the third chamber is filled with gas, wherein both ends of the cylinder are open, and a circumferential groove is formed on an inner surface. A C-ring fitted in a circumferential groove of the cylinder body for restricting movement of the free piston toward the piston; and a C-ring on one of the open ends of the cylinder body. A first lid adapted to be threadedly engaged, wherein the first lid allows for injecting gas from outside into the third chamber, but wherein gas from the third chamber is external. To prevent leakage A second lid adapted to be screw-engaged with the other of the open ends of the cylinder body, wherein the second lid slides a piston rod. The above-mentioned shock absorber, wherein a through-hole for freely supporting is formed. 3. The shock absorber according to claim 2, wherein at least one of the ends of the C-ring is bent radially inward. 4. A cylinder having a piston and a piston rod having a piston slidably supported by the cylinder, wherein the piston divides the cylinder into a first chamber and a second chamber, An orifice communicating the chamber with the second chamber, the cylinder having a free piston slidably supported by the cylinder, the free piston connecting the second chamber of the cylinder to the second chamber, Subdivided into three rooms,
A method of assembling a shock absorber, wherein the first chamber and the second chamber are filled with oil and the third chamber is filled with gas, wherein the cylinder is open at both ends and has a circumferential groove formed on an inner surface. A C-ring for restricting the movement of the free piston is fitted into the peripheral groove of the main body, the free piston is inserted into the cylinder main body, and the free piston is positioned between the free piston and the C-ring. A first lid is screw-engaged with one of the open ends of the cylinder body, and the third chamber is filled with gas via a check valve provided on the first lid, Pour oil into the cylinder body from the other of the open ends of the cylinder; insert the piston rod into the cylinder body from the other open end of the cylinder body; A threaded engagement with the other open end of the cylinder body by passing a through hole through the piston rod.