JPH1054435A - gas spring - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To always maintain a lubricated state between a sliding surface of a seal member and a piston rod in an extension stroke and a contraction stroke, and to greatly extend the life of the seal member. SOLUTION: A seal member 6 is provided between a cylinder 1 and a piston rod 4, and a lip portion 6B of the seal member 6 is provided.
The gas pressure from the gas chambers A and B in the cylinder 1 is directly received by the lip portion 6B of 6C. Then, an annular oil sump space 7 is formed on the outer peripheral surface side of the piston rod 4 between the lip portions 6B and 6C of the seal member 6, and the oil sump space 7 is filled with the oil liquid 2. Also, the lip portions 6B, 6
C, the sliding surface side of the lip portion 6B is formed as an arc surface having a convexly curved cross section, and a part of the oil liquid on the gas chamber B side is formed between the sliding contact surface and the piston rod 4 in an oil sump space. 7 to allow it to seep (leak) by a very small amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas spring suitable for opening and closing, for example, a back door of a wagon car.

[0002]

2. Description of the Related Art Generally, a cylindrical cylinder in which a pressurized gas is sealed together with an oil liquid, and a piston which is slidably fitted into the cylinder and defines two gas chambers in the cylinder. And a piston rod having one end connected to the piston and the other end protruding outside the cylinder, and provided between the piston rod and the cylinder to prevent the oil liquid in the cylinder from leaking to the outside. A gas spring composed of a sealing member that performs
No. 6 (hereinafter referred to as a first prior art) and the like.

[0003] The gas spring according to the first prior art is applied to, for example, a back door of a wagon car, and is mounted on a vehicle body side and a back door side.
When the door is closed, the piston rod is extended and retracted with respect to the cylinder.

The extension of such a piston rod,
When the piston rod moves in and out of the cylinder in response to the contraction operation, each gas chamber in the cylinder expands and contracts, thereby providing a predetermined repulsive force (spring force) in each gas chamber.
Generate. At this time, a predetermined damping force (buffering effect) is generated by flowing a pressurized gas between the gas chambers through an orifice or the like provided in the piston.

[0005] Here, a space is formed below the seal member provided between the cylinder and the piston rod for storing an oil liquid between the cylinder and the outer periphery of the piston rod. When a part of the oil liquid (oil film) adhered to the piston rod in the cylinder is scraped off by the seal member during the expansion and contraction operation, the scraped oil liquid is temporarily removed in the space. Is to be stored (captured).

[0006] The oil stored in the space prevents the pressurized gas in the cylinder from leaking.
In the extension stroke of the piston rod, a state in which the oil liquid is previously attached to the piston rod in the space and the oil liquid is contained between the sliding surfaces of the piston rod and the seal member, that is, a state of so-called "wet contact" Thus, the piston rod is slid with respect to the seal member, thereby reducing the sliding resistance between the sliding surfaces and obtaining good sliding characteristics.

A second prior art is disclosed in Japanese Utility Model Application Laid-open No.
A gas spring described in Japanese Patent No. 72945 is known. In the second conventional technique, a first seal member is provided between a cylinder and a piston rod, and the first seal member directly receives gas pressure from a pressurized gas, and the cylinder and the piston rod are connected to each other. A second seal member is disposed between the first seal member and the air side opposite to the gas chambers in the cylinder with the first seal member interposed therebetween.
An oil reservoir space for filling the oil liquid is formed on the outer peripheral side of the piston rod between the seal members.

[0008] In this case, when the piston rod slides with respect to the first seal member during the reduction stroke of the piston rod, the oil liquid can be previously attached to the piston rod in the oil reservoir space. This also allows the piston rod to slide in a "wet contact" state with respect to the seal member as in the case of the first prior art, so that good sliding characteristics can be obtained.

[0009]

In the first prior art described above, when the piston rod is kept in contact with the outside air for a long time while the piston rod is extended from the cylinder, the piston rod is not extended. The oil liquid adhering to the outer peripheral surface may evaporate in the atmosphere, and if the next reduction stroke is performed in this state, the oil liquid will hardly be contained between the sliding surfaces of the piston rod and the seal member. That is, the piston rod is reduced and moved into the cylinder in a so-called "dry contact" state.

[0010] As a result, the sliding resistance between the piston rod and the seal member becomes extremely large, and the seal member is worn out or damaged at an early stage, and the life of the seal member is shortened. is there.

On the other hand, in the second prior art, a second seal member is provided above (atmospheric side) a first seal member which directly receives gas pressure in a cylinder, and an oil liquid is provided between the seal members. Is formed, the piston rod can be slid in the state of "wet contact" with the first seal member by the oil liquid in the oil reservoir space even in the reduction stroke. Thus, the problem of the first related art can be solved.

However, in such a conventional technique,
It is necessary to newly provide a second seal member and the like in addition to the first seal member, which increases the number of parts,
There is a problem that the entire structure and the like are complicated.

It has also been studied to improve the corrosion resistance and wear resistance of the piston rod by subjecting the surface of the piston rod to hard chrome plating or the like. Since a plurality of fine “cracks” called channel cracks are formed on the surface of the hard chromium plating layer, a part of the oil liquid in the cylinder retained on the seal member side is partially filled with the hard chrome. The gas spring oozes out to the sliding surface between the seal member and the piston rod through the “crack” of the plating so as not to affect the life of the gas spring.

Thus, it is possible to always maintain a lubricated state between the sliding surfaces between the seal member and the piston rod in both the extension stroke and the contraction stroke of the piston rod. In this case, there is an advantage that it is not necessary to specially provide the second seal member or the like as described in the second related art, and the entire structure can be simplified.

On the other hand, in recent years, in order to enhance the corrosion resistance and abrasion resistance of the piston rod due to environmental considerations, the outer peripheral surface of the piston rod is subjected to gas nitrocarburizing treatment and oxidation in place of the hard chrome plating treatment. A method of protecting the sliding (outer peripheral) surface of the piston rod by performing a treatment has been studied.

However, the piston rod which has been subjected to the gas nitrocarburizing treatment and the oxidizing treatment does not have any of the "cracks" generated when the hard chromium plating treatment is performed. The amount of seepage (supply amount) of the oil liquid between the sliding surfaces of the member and the piston rod is significantly reduced. As a result, there is a problem that the sliding resistance between the sliding surfaces increases, which also causes the seal member to be worn and damaged early.

The present invention has been made in view of the above-mentioned problems of the prior art, and the present invention provides a method of forming a seal member and a piston rod even when a piston rod subjected to a gas soft nitriding treatment and an oxidation treatment is used. An object of the present invention is to provide a gas spring in which the sliding surfaces are always kept in a lubricated state, the sliding resistance between the sliding surfaces can be greatly reduced, and the life and the like of the seal member can be greatly extended. The purpose is.

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a cylindrical cylinder in which a pressurized gas is sealed together with an oil liquid, and the cylinder is slidably inserted into the cylinder. A piston that slides in the cylinder, a piston rod having one end connected to the piston and the other end protruding out of the cylinder, and provided between the piston rod and the cylinder. The present invention is applied to a gas spring including a sealing member for preventing oil liquid and pressurized gas from leaking to the outside.

The first aspect of the present invention is characterized in that a plurality of lips slidingly contact the outer peripheral surface of the piston rod with the seal member with respective interferences, and are spaced apart in the axial direction of the piston rod. And a concave portion that is located between the lip portions and forms an oil sump space between the outer peripheral surface of the piston rod and the lip portion that receives pressure in the cylinder among the lip portions is provided. The sliding contact surface with the piston rod is formed as a convexly curved arc surface.

With such a configuration, of the lip portions of the seal member provided between the piston rod and the cylinder, a contact (sliding contact) surface of the lip portion for receiving pressure in the cylinder with the piston rod. By forming the sliding contact surface side of the lip portion as a convexly curved arc surface, the whole can be made smoother, and the sliding resistance between the lip portion and the piston rod can be reduced.

When the gas spring is used in an inverted state, a small amount of oil liquid in the cylinder is allowed to seep into the oil sump space between the lip and the piston rod. Even if the oil liquid slightly leaks out of the oil sump space, the oil liquid from the cylinder can always be supplied into the oil sump space, and the oil sump space is filled with the oil liquid. Can be kept.

Thus, the piston rod can be brought into contact with the oil liquid both in the gas chamber in the cylinder on the high pressure side and in the oil reservoir space on the atmospheric pressure side. When the piston rod extends out of the cylinder through each lip portion of the seal member provided between the cylinder and the cylinder during the extension stroke, it is necessary to previously apply an oil liquid to the outer peripheral surface of the piston rod in the cylinder. With this oil solution, the sliding surfaces of the piston rod and the lip portion of the seal member can be brought into sliding contact with each other in a "wet contact" state.

Also, when the piston rod is contracted into the cylinder through each lip of the seal member in the contraction stroke, the outer periphery of the piston rod in the oil sump space is similar to the case of the extension stroke. An oil liquid can be applied to the surface in advance, and the oil liquid can cause the sliding surfaces of the piston rod and the lip portion of the seal member to make sliding contact with each other in a "wet contact" state.

Further, in the invention described in claim 2, the arc surface of the lip portion is formed with an arc radius of 0.1 to 1.0 mm. As a result, the contact area between the arc surface of the lip portion and the piston rod can be reduced, whereby the oil liquid in the cylinder is favorably introduced into the oil sump space through the space between the piston rod and the arc surface of the lip portion. The sliding resistance between the lip portion and the piston rod can be reliably reduced.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a case where a gas spring according to an embodiment of the present invention is mounted in an inverted state (a rod projecting end of a cylinder is directed downward) will be described as an example.

Here, the embodiment of the present invention will be described with reference to FIGS.
It will be described based on.

In the drawing, reference numeral 1 denotes a cylinder having a closed cylindrical shape.
A pressurized gas and a certain amount of oil liquid 2 are sealed in the cylinder 1 via a seal member 6 described later, and the oil liquid 2 is sealed on the seal member 6 side. Reference numeral 3 denotes a piston slidably provided in the cylinder 1. The piston 3 defines two gas chambers A and B in the cylinder 1 above and below. The piston 3 has an orifice passage 3A communicating between the gas chambers A and B.

Reference numeral 4 denotes a piston rod. The upper end of the piston rod 4 is provided integrally with the piston 3, and the lower end of the other end protrudes out of the cylinder 1 via a rod guide 5 described later. ing. Here, the outer peripheral surface of the piston rod 4 is subjected to a gas nitrocarburizing treatment and an oxidation treatment so as to enhance the wear resistance and the corrosion resistance of the entire piston rod 4 and to take environmental consideration into consideration. I have. The outer peripheral surface of the piston rod 4 is formed as a sliding surface for each lip portion 6B, 6C of the seal member 6 described later.

Reference numeral 5 denotes a rod guide provided on the open end side (lower end side) of the cylinder 1. The rod guide 5 is formed as a short-axis cylindrical body, and its outer peripheral side is the inner peripheral side of the open end side of the cylinder 1. It is fitted to. Then, the rod guide 5 allows the piston rod 4 to pass through a small gap on the inner peripheral side thereof, and moves the piston rod 4 in the axial direction (up,
(Downward). A projection 5 for attaching the seal member 6 is provided on the upper end surface of the rod guide 5.
A is protruded as shown in FIG.

Reference numeral 6 denotes a seal member located at the lower end side of the cylinder 1 and provided between the cylinder 1 and the piston rod 4. As shown in FIGS. The base 6A1 which contacts the inner surface and the base 6
An annular mounting portion 6A having a substantially L-shaped cross section formed by a bridging portion 6A2 extending radially inward from A1, and an annular mounting portion 6A2 of the mounting portion 6A extending diagonally upward diagonally inward in the radial direction. It comprises a first lip portion 6B and an annular second lip portion 6C projecting radially inward from the bridging portion 6A2 of the mounting portion 6A. A circumferential portion is provided between the lip portions 6B and 6C. An annular concave portion 6D having a substantially V-shaped cross section is formed. A mounting groove 6E is formed on the lower end surface of the mounting portion 6A. Then, the mounting portion 6A
The outer peripheral surface is fitted to the inner peripheral surface of the cylinder 1, and the lower surface is integrally attached to the upper end surface of the rod guide 5 with the concave groove 6E fitted to the convex portion 5A.

The lip portions 6B and 6C are slidably contacting the outer peripheral surface of the piston rod 4 with their inner peripheral ends serving as sliding contact surfaces 6B1 and 6C1, respectively. The annular recess 6D forms an annular oil sump space 7 having a substantially triangular cross section between the lip portions 6B and 6C and the outer peripheral surface of the piston rod 4, and the oil sump space 7 has oil therein. Liquid 2 is filled.

The lip portion 6B of the lip portions 6B and 6C directly receives the gas pressure from the gas chambers A and B, and pressurizes the gas chambers A and B above the lip portion 6B to, for example, 70 atm. Oil reservoir space 7 and the lip portion 6 below the lip portion 6B.
The C side is kept at atmospheric pressure.

Here, the sliding contact surface 6B1 of the lip portion 6B
As shown in FIGS. 3 and 4, the vertical section is formed as a circular arc surface having a convex curved shape, and the contact surface of the sliding contact surface 6B1 with the piston rod 4 is entirely smooth and the lip portion 6 is formed.
It is rounded to reduce the sliding resistance between B and the piston rod 4. The lip portion 6 </ b> B is configured to allow a part of the oil liquid 2 on the gas chamber B side to seep (leak) by a minute amount into the oil reservoir space 7 between the lip portion 6 </ b> B and the piston rod 4. .

The arc surface of the sliding surface 6B1 has an arc radius of 0.5 mm. When this radius is smaller than 0.1 mm, the seepage of the oil liquid from the gas chamber B into the oil sump space 7 occurs. Experiments have shown that the sliding resistance increases and the sliding resistance increases, and if it exceeds 1 mm, the contact area with the piston rod 4 increases and the sliding resistance increases. Therefore, this radius is desirably about 0.5 mm to 1.0 mm.

The sliding contact surface 6C1 of the lip 6C has a substantially triangular longitudinal section and is formed to have substantially the same inner diameter as the lip 6B. The lip portion 6C keeps the space between the lip portion 6C and the outer peripheral surface of the piston rod 4 in a liquid-tight manner.
From the oil sump space 7 to the rod guide 5 and the piston rod 4
It is configured to minimize leakage to the outside through a gap between the two.

Here, even if the oil liquid 2 in the oil sump space 7 slightly leaks outside from between the lip portion 6C and the piston rod 4, a part of the oil liquid on the gas chamber B side as described above. Is supplied from the space between the sliding contact surface 6B1 of the lip portion 6B and the piston rod 4 into the oil reservoir space 7.

The gas spring according to the present embodiment has the above-described configuration. When the gas spring is mounted on, for example, a back door of a wagon car, the mounting bracket 8 provided on the upper end side of the cylinder 1 is used. Is mounted on the body side of the wagon car, and the mounting bracket 9 provided on the lower end side of the piston rod 4 is mounted on the back door side, and the gas spring body rotates with the opening and closing of the back door, and further, the piston rod 4 Is extended and retracted with respect to the cylinder 1. In this case, when the back door is closed, the protruding end side of the piston rod 4 is in a state of standing downward, but when the back door is opened, the protruding end side of the piston rod 4 is in an upright state.

When the piston 3 moves (slids) in the cylinder 1 in response to the extension and contraction of the piston rod 4 when the back door is opened and closed, the gas chambers A and B in the cylinder 1 are expanded. As a result, a predetermined repulsive force (spring force) is generated in each of the gas chambers A and B. At this time, a predetermined damping force is generated by the pressurized gas flowing between the gas chambers A and B via the orifice passage 3A of the piston 3 and the like.

Here, a seal member 6 is disposed between the cylinder 1 and the piston rod 4, and the lip portion 6B of the lip portions 6B and 6C of the seal member 6 causes the cylinder 1 to move.
Since the gas pressures from the gas chambers A and B are directly received, the sliding contact surface 6B1 of the lip portion 6B slides while strongly pressed against the outer peripheral surface of the piston rod 4 as shown in FIG. Be in touch. For this reason, it is necessary to maintain the lubrication state between the sliding contact surface 6B1 of the lip portion 6B and the outer peripheral surface of the piston rod 4 with the oil liquid 2 to reduce the sliding resistance generated between the two.

In this embodiment, the piston rod 4
By performing a gas nitrocarburizing treatment and an oxidation treatment on the outer peripheral surface of the piston rod 4, the wear resistance and corrosion resistance of the entire piston rod 4 are enhanced, and further consideration is given to environmental aspects.
As a result, fine "cracks" such as the hard chrome plating layer described in the related art are not formed on the outer peripheral surface of the piston rod 4.

However, in this embodiment, the oil spring 2 in the gas chamber B is retained on the lip portion 6B side of the sealing member 6 by mounting the gas spring so that the gas spring is in an inverted state when the back door is closed, and the sealing is performed. Lip 6 of member 6
Since an annular oil sump space 7 is formed between B and 6C on the outer peripheral surface side of the piston rod 4, when the back door is opened, the gas spring main body rotates and the erecting (cylinder rod 4
The oil reservoir 2 can be filled with the oil liquid 2 even if the protruding end of the oil reservoir 2 faces upward.

Since the sliding surface 6B1 side of the lip 6B is formed as a circular arc surface having a convexly curved cross section, the sliding contact surface 6B1 with the piston rod 4 is smooth. And the sliding resistance between the lip portion 6B and the piston rod 4 can be reduced.

Then, between the sliding surface 6B1 of the lip portion 6B and the piston rod 4, a part of the oil liquid on the gas chamber B side oozes (leaks) a small amount into the oil reservoir space 7. And the oil liquid 2 in the oil sump space 7 is
Even if there is a slight leak to the outside from between C and the piston rod 4, the oil liquid 2 can be constantly supplied from the gas chamber B side into the oil sump space 7, and the oil liquid 2 in the oil sump space 7 Can be reliably prevented from disappearing.

Thus, the outer peripheral surface of the piston rod 4 can be brought into contact with the oil liquid 2 on both the gas chamber B side on the high pressure side and the oil reservoir space 7 side on the atmospheric pressure side. And
When the piston rod 4 extends out of the cylinder 1 through the lip portions 6B and 6C of the seal member 6 during the extension stroke, the oil liquid 2 adheres to the outer peripheral surface of the piston rod 4 in the gas chamber B of the cylinder 1 in advance. The outer surface of the piston rod 4 and the lip 6
The sliding surfaces 6B1 and 6C1 of B and 6C can be brought into sliding contact with each other in a "wet contact" state.

Also, in the contraction stroke, the oil liquid can be previously attached to the outer peripheral surface of the piston rod 4 in the oil reservoir space 7 in the same manner as in the above-described extension stroke. 4 and lip portions 6B, 6
The sliding surfaces 6B1 and 6C1 of C can be brought into sliding contact with each other in a "wet contact" state.

Here, the sliding surface 6B1 of the lip portion 6B
An experiment was conducted to investigate the effects of the shape and the presence or absence of the oil sump space 7 on the sliding characteristics between the piston rod 4 and the seal member 6 and the durability of the seal member 6.
Based on the first to third comparative examples shown below, the experimental results shown in Table 1 could be obtained.

In this experiment, the piston rod 4 was set at 0.
Stretching and contracting were performed up to 50,000 times at a cycle of 17 Hz (100 mm / s). Further, the sliding resistance shown in Table 1 depends on the gas chamber A when the piston rod 4 is at maximum extension and at minimum contraction.
The sliding resistance is calculated as the difference between the two gas pressures by measuring the gas pressures inside. Further, “───” shown in Table 1 indicates a case where measurement has not been performed.

[0048]

[Table 1]

First, in the first comparative example shown in FIG. 5, a seal member 11 is used in place of the seal member 6. Here, the seal member 11 is formed substantially in the same manner as the seal member 6 described in the above embodiment, and the first and second lip portions 11A,
Although the lip portion 11A has the lip portion 11A, the lip portion 11A has a substantially triangular cross section similarly to the lip portion 11B, and the sliding surface 11A1 for the piston rod 4 is formed as a flat inclined surface. The seal member 11 has an annular concave portion 11C between the lip portions 11A and 11B which forms an annular oil sump space (not shown) with the piston rod 4.

Then, the sealing member 1 according to the first comparative example
When the piston rod 4 is extended and contracted from the first few times to ten times as shown in Table 1,
The sliding resistance values were 90N and 80N, respectively, and it was found that the same sliding characteristics as those of the seal member 6 were obtained.

However, in the case of the first comparative example, the sliding contact surface 11A1 of the lip portion 11A is formed as a flat surface. The sliding resistance between the surface 11A1 and the piston rod 4 is increased, and after the durability test of 50,000 times, the seal member 11 is peeled off and oil leakage occurs. Then, the supply amount of the oil liquid 2 from the gas chamber B side to the oil sump space via the sliding contact surface 11A1 decreases, and the sliding contact surface 11A1 slides on the piston rod 4 in a "dry contact" state. Probably moved.

Next, in the second comparative example, a seal member 21 shown in FIG. Here, the seal member 21 has a single lip portion 21A (sliding contact surface 21A1). When the seal member 21 is used, the sliding resistance at the time of the initial extension and contraction of the piston rod 4 becomes 160 N as shown in Table 1, which is about 80 N compared to the case of this embodiment (90 N). %, It was determined to be unacceptable.

This is because the gas chamber B is sandwiched between the lip portions 21A.
It is impossible to bring the outer peripheral surface of the piston rod 4 into contact with the oil liquid 2 on the atmosphere side opposite to the above, and the sliding contact surface 21A1 comes into "dry contact" with the piston rod 4 during the reduction stroke of the piston rod 4. It is considered that the sliding resistance becomes excessive by sliding in the state.

Next, in the third comparative example, a seal member 31 shown in FIG. Here, the seal member 31 has a first lip portion 31A (sliding contact surface 3A) substantially in the same manner as the seal member 21 described in Comparative Example 2.
1A1), the sliding surface 31A1 of the lip 31A is formed as a convexly curved arc surface.

When the seal member 31 is used, as in the case of the first comparative example, when the piston rod 4 is extended and contracted from the first several times to ten times, the seal member 6 It was found that the same sliding characteristics as described above were obtained. However, in this case, the oil liquid 2 leaked from between the lip portion 31A and the piston rod 4 and was determined to be unacceptable.

Therefore, in the present embodiment, the outer peripheral surface of the piston rod 4 and the lip portion 6C of the seal member 6 are caused by the oil liquid 2 in the gas chamber B and the oil reservoir space 7 in both the extension stroke and the contraction stroke of the piston rod 4. , 6B can be kept in a lubricated state at all times, so that the durability and abrasion resistance of the seal member 6 can be improved, and the life and the like can be greatly extended. Further, it is not necessary to additionally provide the second seal member and the like as described in the second related art, and the entire structure and the like can be simplified. further,
The piston rod 4 which has been subjected to the gas nitrocarburizing treatment and the oxidation treatment can be easily applied to the gas spring.

In the above embodiment, the seal member 6
Although it is described that the lip portions 6B and 6C are provided,
The present invention is not limited to this. For example, the lip portions 6B, 6C
A plurality of lip portions similar to the above may be further provided between the lip portions 6B and 6C, and a plurality of oil reservoir spaces may be provided between these lip portions.

In the above-described embodiment, the gas spring is described as being applied in an upright state. Alternatively, the gas spring may be applied in an upright state.

Further, in the above-described embodiment, the description has been given as applied to the door opening device for the back door. However, the present invention is not limited to this, and may be applied to a hood, a rear window of a vehicle, a door opening device other than a vehicle, or the like. May be applied.

[0060]

As described in detail above, according to the present invention, each lip portion of the seal member is slidably contacted with the outer peripheral surface of the piston rod with an interference, as described in the first aspect. An oil reservoir space is formed between the outer peripheral surface of the piston rod and the lip portion of each of the lip portions that receives pressure in the cylinder. Since it is formed as a surface, a part of the oil liquid on the gas chamber side between the sliding surface of the lip portion and the piston rod is allowed to seep (leak) by a minute amount into the oil sump space. Even if the oil liquid in the oil sump space leaks outside, the oil liquid can be constantly replenished from the gas chamber into the oil sump space.

Therefore, the outer peripheral surface of the piston rod can be brought into contact with the oil liquid on the gas chamber side on the high pressure side and on the oil reservoir space side on the atmospheric pressure side. Lubrication between the outer peripheral surface of the rod and each lip of the seal member can be maintained,
The durability and abrasion resistance of the seal member can be improved, and the life and the like can be greatly extended. Also,
It is not necessary to additionally provide the second seal member as described in the second related art, and the entire structure and the like can be simplified. Further, a piston rod that has been subjected to a gas nitrocarburizing treatment and an oxidation treatment can be easily applied to the gas spring.

According to the second aspect of the present invention, the arc surface of the lip is formed to have an arc radius of 0.1 to 1.0 mm. It becomes possible to swell well into the oil sump space through the space between the circular arc surface and the sliding resistance between the lip portion and the piston rod can be reliably reduced,
The durability, wear resistance, and the like of the seal member can be further improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a gas spring according to an embodiment of the present invention.

FIG. 2 is an enlarged partial cross-sectional view showing a rod guide, a seal member, and the like in FIG. 1;

FIG. 3 is an enlarged view of a main part in FIG. 2 showing each lip portion of the seal member, an oil sump space, and the like.

FIG. 4 is a partial cross-sectional view showing a state where a seal member in FIG. 3 is removed from a gas spring.

FIG. 5 is a cross-sectional view similar to FIG. 4, illustrating a seal member used in a first comparative example.

FIG. 6 is a sectional view similar to FIG. 4, showing a seal member used in a second comparative example.

FIG. 7 is a sectional view similar to FIG. 4, showing a seal member used in a third comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Oil liquid 3 Piston 4 Piston rod 6 Seal member 6B, 6C Lip part 6B1 Sliding surface 6D Annular recess (recess) 7 Oil storage space A, B Gas chamber

Claims (2)

[Claims] 1. A cylindrical cylinder in which a pressurized gas is sealed together with an oil liquid, a piston slidably fitted in the cylinder, and sliding in the cylinder. A piston rod connected to the other end thereof and protruding out of the cylinder, and a seal member provided between the piston rod and the cylinder to prevent oil liquid and pressurized gas in the cylinder from leaking outside. A plurality of lip portions slidingly contacting with an outer peripheral surface of the piston rod with respective interferences in an axial direction of the piston rod, and the seal member is located between the lip portions. A concave portion that forms an oil sump space is provided between the piston rod and the outer peripheral surface; Gas spring, characterized in that the sliding surface formed as a convex curved arc surface with. 2. An arc surface of the lip portion is 0.1-1.
2. The gas spring according to claim 1, wherein the gas spring is formed with an arc radius of 0 mm.