JP2003336678A - Gas spring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas spring capable of always providing constant sealing action irrespective of use environment and ensuring stable operation of a piston rod. <P>SOLUTION: This gas spring is constituted in such a way that a piston rod 3 is movably inserted into a cylinder 1 through a piston 2, the piston rod is always energized in the direction of elongation by gas pressure in the cylinder, the piston partitions a rod side chamber 4 and a piston side chamber 5 in the cylinder, the rod side chamber and the piston side chamber are mutually communicated through a passage 6 formed in at least the piston, and a check ring 24 opposing to the piston is slidably inserted into inner periphery of the cylinder to open and close the passage by the move of the check ring in the axial direction. The check ring is provided with a basic part 28 provided with an insertion hole 27 at the center and a lip part 29 formed by bending it at outer periphery of the basic part and coming into slide-contact with an inner peripheral face of the cylinder and is formed by a platelike raw material having a shape memory characteristic. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to opening / closing operations of a back door, an engine hood, a window, etc., which is interposed between a vehicle body of a vehicle and a back door, between the vehicle body and an engine hood, or in a window of a building. It relates to a gas spring suitable for improving.

[0002]

2. Description of the Related Art Generally, in a vehicle such as an automobile, for example, a gas spring, which is constantly urged in an extension direction by gas pressure, is interposed between a vehicle body and a back door.

This gas spring generates a large damping force to open the back door slowly against the urging force when the back door is unlocked, and a small operating force to close the opened back door. It is designed to generate only a small damping force so that
The configuration is as shown in FIGS.

That is, a piston rod 3 having a threaded portion 12 screwed to the vehicle body at the tip is also provided in a cylinder 1 having a bracket 11 connected to the back door at the tip. It is inserted freely.

The piston 2 divides the inside of the cylinder 1 into a piston side chamber 4 and a rod side chamber 5, and these chambers 4 and 5 are formed in the piston 2 and a piston side orifice 6 and a cylinder formed in the cylinder 1. The side orifices 10 communicate with each other.

The piston 2 has a plurality of notched grooves 13 forming the piston side orifice 6 formed on the outer peripheral portion thereof, and a plate-shaped stopper member 22 having a plurality of notched portions 21 on the outer periphery thereof, together with the piston rod 3. It is fixed by swaging to the base end spigot.

Further, the outer periphery of the piston 2 on the rod side chamber 5 side is notched in a stepped shape except for the stopper member 22.
An annular groove 23 is formed on the outer circumference of the piston 2 in cooperation with the stopper member 22.

An annular check ring 24 is mounted in the annular groove 23 so as to be movable in the axial direction, and the check ring 24 abuts on a piston side wall portion 25 constituting the annular groove 23 so that the annular check ring 24 is attached to the wall portion 25. It has a so-called check valve function of closing the end of the opened piston side orifice 6 on the rod side chamber 5 side and opening the end of the rod side chamber 5 by separating from the piston side wall portion 25.

The check ring 24 has an outer diameter slightly larger than the inner diameter of the cylinder 1 at room temperature and is press-fitted into the cylinder 1 to form an outer peripheral surface of the piston 2 and an inner peripheral surface of the cylinder 1. Between the check ring 24 and the inner peripheral surface of the cylinder 1, a so-called sealing function is provided to prevent gas leaking from the space between the piston side orifice 6 and the rod side chamber 5 side end portion.

Therefore, during the extension stroke of the gas spring, the check ring 24 abuts the piston side wall 25 to close the end on the rod chamber side 5 of the piston side orifice 6, and the gas passing through only the cylinder side orifice 10 causes a large amount. During the compression stroke, the check ring 24 moves to the stopper member 22 side to open the rod side chamber 5 side end portion of the piston side orifice 6, and the piston side orifice 6 and the cylinder side orifice 10 are generated. Only a small damping force is generated by the gas passing through.

The piston rod 3 is axially guided by a bearing 7 and a retainer 8 provided in the vicinity of the end of the cylinder 1 and approximately in the middle, and a seal 9 is provided on the inner end side of the bearing 7. This seal 9 is a synthetic rubber main lip 15 that is in sliding contact with the outer circumference of the piston rod 3.
And a metal cored bar 16 integrally formed with the main lip 15.

In the figure, O is a lubricating oil stored in the cylinder 1, and G is a high pressure gas sealed in the cylinder 1.

In the gas spring constructed as described above, when the lock of the back door is released, the gas pressure filled in the cylinder 1 causes the piston rod 3 to move due to the difference in pressure receiving area between the piston side chamber 4 and the rod side chamber 5. Extend and automatically open the back door.

In the extension process of this gas spring, as shown in FIG.
As shown in, the inner surface of the cylinder 1 and the check ring 24
Due to the friction of the outer peripheral surface and the gas pressure of the rod side chamber 5, the check ring 24 moves so as to contact the piston side wall portion 25 and closes the end portion of the piston side orifice 6 on the rod side chamber 5 side. And the cylinder side orifice 10 provided in the cylinder 1 communicate with each other.

Therefore, the high pressure gas on the rod chamber side 5 passes through the cylinder side orifice 10 and moves to the piston side chamber 4 as shown by the arrow X in FIG. 7, and at that time, a large damping force is generated. The back door opens slowly as you did.

When the open back door is closed, the gas spring is in the compression stroke, and as shown in FIG. 8, due to the friction between the inner peripheral surface of the cylinder 1 and the outer peripheral surface of the check ring 24 and the gas pressure in the piston side chamber 4. Since the check ring 24 moves to the stopper member 22 side to open the end portion of the piston side orifice 6 on the rod side chamber 5 side, the rod side chamber 5 and the piston side chamber 4 communicate with each other through the cylinder side orifice 10 and the piston side orifice 6. It will be.

Therefore, the high pressure gas in the piston side chamber 4 is shown in FIG.
As indicated by the arrow Y, the piston moves toward the rod side chamber 5 through the piston side orifice 6, the inside of the check ring 24 and the cylinder side orifice 10, and at that time, a small damping force is generated. It can be closed by force.

[0018]

In the gas spring constructed as described above, the check ring 24 housed in the annular groove 23 as the piston rod 3 moves back and forth.
Since it constantly slides on the inner peripheral surface of the cylinder 1, it moves repeatedly from the piston side wall portion 25 to the stopper member 22. Therefore, in order to fully exert the above-mentioned check valve function and seal function, the check ring 24 It itself is required to be a low sliding friction body.

Therefore, the check ring 2 is conventionally used.
4 is a polytetrafluoroethylene resin (hereinafter, PTF
It is made of a material having a low coefficient of friction such as E resin).

However, this PTFE resin has a creep (sagging) characteristic that the deformation gradually progresses when a constant stress is applied, and this characteristic tends to increase as the temperature rises. .

For this reason, in a gas spring in which a high temperature condition of 120 ° C. is a working environment, it is particularly susceptible to the creep characteristics, and the check ring 24 press-fitted into the cylinder 1 in an elastically deformed state contracts. Creates a gap between the inner diameter of the cylinder 1 and the outer diameter of the check ring 24,
There is a problem in that the initial sealing function and check valve function are lost.

Therefore, it is necessary to set the outer diameter of the check ring 24 large in consideration of the above-mentioned contraction, but if it is set too large, the frictional resistance will increase too much and the movement of the check ring 24 will worsen. However, there is a problem that it is difficult to set the outer diameter of the check ring 24.

Therefore, an object of the present invention is to provide a gas spring which always exhibits a constant sealing action regardless of the use environment and can secure a stable operation of the piston rod.

[0024]

In order to achieve the above object, according to the present invention, a piston rod is movably inserted into a cylinder via a piston, and the piston rod is always extended by a gas pressure in the cylinder. Energized, the piston defines a rod side chamber and a piston side chamber in the cylinder,
The rod-side chamber and the piston-side chamber communicate with each other through at least a passage formed in the piston, and a check ring facing the piston is slidably inserted into the inner circumference of the cylinder.
In a gas spring that opens and closes the passage by moving the check ring in the axial direction, the check ring has a base portion having an insertion hole in the center and a lip formed by bending the outer circumference of the base portion and slidingly contacting the inner peripheral surface of the cylinder. And a plate-shaped material having shape memory characteristics.

In this case, it is preferable that the check ring is formed in a U-shaped, U-shaped or trapezoidal cross section at the base portion and the lip portion.

Similarly, it is preferable that a stop member is provided on the piston rod so as to face the piston at an arbitrary interval, and a check ring is axially movable between the piston and the stop member.

Similarly, it is preferable to provide a cylinder side orifice on the inner peripheral side of the cylinder for constantly communicating the rod side chamber and the piston side chamber.

Further, the material having the shape memory characteristic is preferably a disc-shaped polytetrafluoroethylene resin.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is embodied in a gas spring used for a back door of an automobile will be described below with reference to FIGS.

This gas spring is characterized by the shape of the check ring 24 attached to the piston 2, and the other structures are the same as those of the conventional gas spring shown in FIGS. Only the same reference numerals are given inside, and the description thereof is omitted.

That is, the check ring 24 is made of PTF.
It is formed by plastically deforming a disk-shaped material 26 made of E resin into a U-shaped cross section by cold or hot forming, and has an insertion hole 27 that can be inserted into the annular groove 23 and also serves as a passage for high-pressure gas at the center. It is composed of a horizontal plate-shaped base portion 28 and a lip portion 29 formed by bending the base portion 28 in a substantially perpendicular direction.

The outer diameter of the lip portion 29 is slightly larger than the inner diameter of the cylinder 1.
The lip portion 29 is pressed into the cylinder 1
It is configured to elastically contact the inner peripheral surface.

Further, this PTFE resin has a shape memory characteristic that it returns to the shape before plastic deformation when a temperature is applied to a plastically deformed product in a free state. In this embodiment, it has a U-shaped cross section. The bent check ring 24 is a phenomenon in which a bent portion extending from the base portion to the lip portion 29 expands when heat is applied, and the check ring 24 returns to the original disc shape as a whole.

Therefore, when heat is applied to the check ring 24 press-fitted into the cylinder 1, the check ring 24 itself tries to return to the original disk state due to the shape memory characteristic, so that the lip portion 29 is provided inside the cylinder 1. Since the sliding contact is made with a large tightening margin on the peripheral surface, sufficient creeping performance can be ensured even if the check ring 24 has a reduced diameter due to the creep characteristics.

Here, a method of forming the check ring 24 will be briefly described with reference to FIGS.

This molding method is a cold or hot-melting method having a melting point or less, and as shown in FIG.
The lower die 32 having the guide pin 31 standing upright in the center, the disc-shaped material 26 is inserted into the insertion hole 27 of the guide pin 3
It is arranged so that 1 is inserted.

Then, as shown in FIG. 4, when the annular upper die 33 is lowered along the guide pin 31, the disc-shaped material 26 is plastically deformed along the molding surface 30,
The check ring 24 has a U-shaped cross section as described above.

In the gas spring constructed as described above, in the extension stroke thereof, as shown in FIG. 1, the check ring 24 is caused by friction between the inner peripheral surface of the cylinder 1 and the outer peripheral surface of the check ring 24 and the gas pressure of the rod side chamber 5. Moves toward the piston side wall portion 25 to close the end portion of the piston side orifice 6 on the rod side chamber 5 side, so that the rod side chamber 5 and the piston side chamber 4 communicate with each other only through the cylinder side orifice 10 provided in the cylinder 1. It will be.

Therefore, the high pressure gas on the rod chamber side 5 is as shown in FIG.
As indicated by the arrow X, the cylinder passes through the cylinder side orifice 10 and moves to the piston side chamber 4, and at that time, a large damping force is generated, so that the back door slowly opens as described above.

When the open back door is closed, the gas spring is in the compression stroke, and as shown in FIG. 2, due to the friction between the inner peripheral surface of the cylinder 1 and the outer peripheral surface of the check ring 24 and the gas pressure in the piston side chamber 4. Since the check ring 24 moves so as to come into contact with the stopper member 22 and opens the end of the piston side orifice 6 on the rod side chamber 5 side, the rod side chamber 5 and the piston side chamber 4 communicate with each other by the cylinder side orifice 10 and the piston side orifice 6. Will be done.

Therefore, the high-pressure gas in the piston side chamber 4 passes through the piston side orifice 6, the insertion hole 27 and the cylinder side orifice 10 and moves to the rod side chamber 5 as shown by the arrow Y in FIG. Since only a small damping force is generated, the back door can be closed with a small operating force.

When the expanding and contracting operation of the piston rod 3 is repeated in a high temperature use environment of, for example, 120 degrees, the gas spring itself is also heated to a considerably high temperature and is installed in the cylinder 1. The piston 2 part is also heated.

At this time, the check ring 24 provided so as to face the piston 2 will of course be heated, but the check ring 24 is made of a PTFE resin disc-shaped material 26 cold or below the melting point. Since it is formed by plastically deforming in a U-shaped cross section by hot forming, the lip portion 29 comes into sliding contact with the inner peripheral surface of the cylinder 1 with a large interference due to the shape memory characteristic.

Therefore, even if the check ring 24 has a reduced diameter due to the creep characteristic in which the progress is increased due to high heat, a sufficient sealing property can be secured, so that a stable damping force is always generated to stably operate the piston rod. You can

Further, since the deformation amount due to the shape memory characteristic is much larger than the diameter reduction amount due to the creep characteristic, no special consideration is required to set the outer diameter of the check ring as in the conventional case. Therefore, the design is facilitated, and the manufacturing cost of the gas spring itself can be reduced.

Further, since the check ring is formed by using the PTFE resin, it is possible to exhibit the same low sliding friction as that in the conventional case and smoothly move the check ring.

In this embodiment, the PTFE resin is used as the synthetic resin having the shape memory characteristic, but the present invention is not limited to this, and other synthetic resins may be used.

Further, the cross-sectional shape of the check ring is not limited to the above-mentioned embodiment as long as it can return to a plate-shaped material, and may be formed into a trapezoidal shape or a U-shape.

[0049]

The present invention has the following effects.

1) According to the inventions of the respective claims, not only the constant sealing action is always exhibited irrespective of the use environment to ensure the stable operation of the piston rod, but also the outer diameter of the check ring is set. Since no special consideration is required, the design is easy and the manufacturing cost of the gas spring itself can be reduced.

2) According to the invention of claim 2, the check ring can be easily molded, and the lip portion can always be slidably contacted with the inner periphery of the cylinder with an arbitrary interference regardless of the temperature change.

3) According to the third aspect of the invention, the amount of movement of the check ring can be regulated, and the piston-side orifice can be opened and closed reliably.

4) According to the invention of claim 4, the damping force can be increased or decreased with the opening and closing of the piston side orifice.

5) According to the invention of claim 5, the check ring can be easily molded by plastic deformation and low sliding friction can be obtained, so that the check ring can be moved smoothly.

[Brief description of drawings]

FIG. 1 is a fragmentary front view showing the extension process of a gas spring according to an embodiment of the present invention.

FIG. 2 is a fragmentary front view showing the compression stroke of the gas spring according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a lower mold for check ring molding.

FIG. 4 is a cross-sectional view showing a lower mold and an upper mold for forming a check ring.

FIG. 5 is a cross-sectional view showing a conventional gas spring.

6 is a cross-sectional view of the gas spring of FIG. 5 taken along the line AA.

7 is a fragmentary front view showing the extension process of the gas spring of FIG.

8 is a fragmentary front view showing the compression stroke of the gas spring of FIG.

[Explanation of symbols]

1 cylinder 2 pistons 3 piston rod 4 Piston side chamber 5 Rod side chamber 6 passages (orifice on piston side) 10 Cylinder side orifice 24 check ring 25 Stop member 26 Disc-shaped material 27 insertion hole 28 base 29 Lip G high pressure gas

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshikazu Hirota             2-4-1, Hamamatsucho, Minato-ku, Tokyo World Trade             Yasu Center Building Kayaba Industry Co., Ltd. (72) Inventor Etsuro Nakata             2-4-1, Hamamatsucho, Minato-ku, Tokyo World Trade             Yasu Center Building Kayaba Industry Co., Ltd. F-term (reference) 3J069 AA01 CC13 EE02

Claims (5)

[Claims] 1. A piston rod is movably inserted into a cylinder via a piston, the piston rod is constantly urged in an extending direction by gas pressure in the cylinder, and the piston has a rod side chamber and a piston side chamber in the cylinder. Partition the
The rod-side chamber and the piston-side chamber communicate with each other through at least a passage formed in the piston, and a check ring facing the piston is slidably inserted into the inner circumference of the cylinder.
In a gas spring that opens and closes the passage by moving the check ring in the axial direction, the check ring has a base portion having an insertion hole in the center and a lip formed by bending the outer circumference of the base portion and slidingly contacting the inner peripheral surface of the cylinder. And a gas spring formed of a plate-shaped material having shape memory characteristics. 2. The check ring is formed in a U-shaped, U-shaped or trapezoidal cross-section by the base portion and the lip portion.
Gas spring described in. 3. The piston rod according to claim 1 or 2, wherein a stop member facing the piston is provided at an arbitrary distance from the piston rod, and a check ring is axially movable between the piston and the stop member. Gas spring. 4. The gas spring according to claim 1, wherein a cylinder side orifice is provided on the inner peripheral side of the cylinder so as to always connect the rod side chamber and the piston side chamber. 5. The material having the shape memory characteristic is a disc-shaped polytetrafluoroethylene resin.
The gas spring according to 3 or 4.