JP4019234B2 - Gas spring shaft seal device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a shaft seal device for a gas spring.
[0002]
[Prior art]
In recent years, most vehicles having a back door BD as shown in FIG. 2 (C) use a small amount of hydraulic oil 12 to add a damping force in the vicinity of the extended end in order to assist the opening / closing force of the back door BD. The enclosed gas spring SD is used.
The structure of the gas spring SD will be described with reference to FIG. 2 (A). A non-return valve 7 and a piston 8 which are guided by a back projection of the valve stopper 6 and the piston 8 in the back portion of the piston stopper 1 in the inlay portion 1A of the piston rod 1. Are sequentially inserted and fastened with a piston nut 9. The piston 8 is accommodated in the cylinder 2 so as to be movable up and down, and divides the inside of the cylinder into an upper chamber A and a lower chamber B.
[0003]
The piston rod 1 is slidably guided by a guide member 3 fixed to the lower end of the cylinder 2 and seals the lower chamber B with a seal 4 and a backup ring 14 that assists the seal rod 4.
Gas and hydraulic oil 12 are sealed in the cylinder through a plug 13 and are completely sealed by welding the mounting member 10 after sealing. The stopper 5 is fixed to the cylinder 2 by tightening the central portion of the outer surface, and the valve stopper 6 abuts when the piston rod 1 extends to restrict the maximum extension of the gas spring.
Here, the piston rod 1 is always urged in the extending direction by a repulsive force calculated by multiplying the sectional area of the piston rod itself by the gas pressure in the upper chamber A.
[0004]
The piston 8 is provided with a piston port 8A that communicates the upper chamber A and the lower chamber B. The back seat surface 8B provided at the lower portion of the piston port 8A has an upper and lower piston when the piston rod 1 is extended. A non-return valve 7 having an orifice 7A for restricting the communication area of the chamber is seated.
When the piston rod 1 is contracted, the non-return valve 7 floats up from the back seat surface 8B, and the entire gap between the back seat surface 8B and the non-return valve 7 has a larger opening area than the piston port 8A. The communication area is the area of the orifice 7A when extended, and the area of the piston port 8A when contracted.
[0005]
Next, the operation of the gas spring will be described by taking as an example an attachment method called a reversal type shown in FIG. When the piston rod 1 is attached to the vehicle so that the piston rod 1 is on the lower side when the back door is closed, the hydraulic oil 12 stays in the lower chamber B. As the back door opens, the piston 8 is gradually immersed in the hydraulic oil 12 so as to cover the orifice 7A, and the hydraulic oil 12 staying on the lower chamber B side when the back door is closed passes through the orifice 7A. Move from the lower chamber B to the upper chamber A.
Since the passage resistance when the hydraulic oil 12 passes is larger than when the gas passes through the orifice 7A due to the difference in viscosity resistance, the opening speed in the vicinity of the extended end becomes a moderated buffered speed, The impact at the extended end is alleviated.
[0006]
[Problems to be solved by the invention]
The guide member 3 is made of a resin added with glass fiber (for example, 6 nylon) so that it can soften in a high heat environment and release the high-pressure gas in the gas spring to the atmosphere in order to prevent explosion of the gas spring in the event of a vehicle fire. It has become. Glass fiber is added at a constant rate to ensure mechanical strength at room temperature, but the glass fiber protruding to the inner diameter side during molding causes sliding scratches on the surface of the piston rod 1 fitted therein. As a result, external leakage of high-pressure gas in the gas spring is caused and durability is lowered.
Further, the fitting gap at room temperature must be widened in consideration of the difference in thermal expansion between the resin guide member 3 and the metal piston rod 1. Therefore, when the sealed gas pressure is high, in order to prevent the seal 4 from protruding from the fitting gap due to the internal pressure, the backup ring 14 is made of a resin material having good sliding properties (for example, Teflon) and the fitting gap inside and outside is narrowed. Need to be used together.
[0007]
On the other hand, in the case of a gas spring used in a commercial vehicle or the like where there are many opportunities to carry goods packaged with a vinyl sheet or the like, it corresponds to FIG. 3 of Japanese Utility Model Publication No. 61-6340 already proposed by the present applicant. Like the guide member 3 in FIG. 2, a seal lip 3A is formed on the atmosphere side of the lower end portion to prevent foreign matters such as dust and a thin film sheet from entering the fitting gap from the outside.
However, since the guide member 3 is made of resin containing glass fiber in order to achieve both slidability and mechanical strength at normal temperature, the seal lip 3A is provided with several slits on the circumference. It is divided and has a shape that gives a fastening allowance to the piston rod 1. Due to the presence of slits, it is difficult to completely prevent the entry of foreign matter such as dust and thin film sheets.
[0008]
The present invention has been made in view of the above circumstances, and the object of the present invention is to protrude from the fitting gap of the seal 4 due to internal pressure, and foreign matter such as dust or a thin film sheet from the outside. It is an object of the present invention to provide a shaft seal device for a gas spring that is easy to prevent intrusion.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the means taken by the present invention is that a piston rod that is fastened to a piston slidably mounted on a cylinder and guided by a guide member fixed to the cylinder end is separated from the cylinder. In the gas spring that protrudes freely,
The guide member includes a guide for the high-pressure gas in the gas spring softens at high heat environment is guaranteed to be formed of a resin added with the glass fiber and the mechanical strength so that it can be released to the atmosphere, the resin sliding property is guaranteed seal manufactured by dividing a flanged bush to back, to the in being formed with a flange covering the end portion of the in contact with the inner surface of the cylinder guide of the cylinder inner side with guiding the piston rod, “These two parts are fitted and connected.” If a seal lip is formed on the atmosphere side of the bush with a flange, it is possible to prevent foreign matters such as dust and a thin film sheet from entering the fitting gap.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The structure of the gas spring of the present invention will be described based on the first embodiment shown in FIG. The same parts as those in the conventional structure are designated by the same part numbers, and the description thereof is omitted unless particularly required.
A non-return valve 7 and a piston 8 that are guided in a vertically movable manner by a valve stopper 6 and a rear projection of the piston 8 are sequentially inserted into an inlay portion 1A of the piston rod 1 and fastened by a piston nut 9. The piston 8 is slidably accommodated in the cylinder 2 and divides the inside of the cylinder into an upper chamber A and a lower chamber B. The piston rod 1 is slidably guided by a hooked bush 113 that also serves as a backup and is fitted to a guide 103 fixed to the upper end of the cylinder 2, and the lower chamber B is sealed with a seal 4. is doing.
[0011]
Here, the guide 103 is made of a resin containing glass fiber like the guide member 3 described in the prior art, but the flanged bush 113 fitted to the guide 103 is reinforced so as to cause a sliding damage to the piston rod 1. Molding is performed with a resin material (for example, Teflon) having good slidability to which no agent is added.
While the guide 103 ensures the mechanical strength at normal temperature, the flanged bush 113 prevents the seal 4 from protruding from the fitting gap and ensures the slidability of the piston rod 1. In addition to the improvement, the occurrence of sliding flaws of the piston rod 1 can be prevented and gas leakage can be prevented.
[0012]
The flanged bush 113 is flexible because it does not contain a reinforcing agent that causes sliding flaws on the piston rod, so that the fitting gap with the piston rod 1 can be reduced. Therefore, it is possible to improve the durability of the seal 4 by preventing protrusion from the fitting gap, and it is relatively easy to prevent foreign matters such as dust and a thin film sheet from entering the fitting gap from the outside. It is.
[0013]
In the second embodiment of the present invention shown in FIG. 1 (B), since the seal lip 213A having good sliding property and flexibility is formed at the lower end portion of the bushed bush 213, the tightening margin for the piston rod 1 is reduced. It can be applied and molded, and foreign matter such as dust and thin film sheet can be effectively prevented from entering the fitting gap from the outside.
[0014]
【The invention's effect】
As described above in detail, in the gas spring according to the first embodiment of the present invention, the guide secures the mechanical strength at room temperature, while the bush with a hook prevents the seal rod from protruding from the fitting gap and the piston rod Since the slidability is ensured, the durability of the seal can be improved and the occurrence of sliding scratches on the piston rod can be prevented in advance and gas leakage can be prevented.
The gas spring according to the second embodiment of the present invention is formed by forming a slidable and flexible seal lip at the lower end of the flanged bush, and giving a tightening margin to the piston rod. Therefore, it is possible to effectively prevent foreign matters such as dust and a thin film sheet from entering the fitting gap from the outside.
[Brief description of the drawings]
FIG. 1A is a longitudinal sectional view of a gas spring according to a first embodiment of the present invention.
(B) It is a longitudinal cross-sectional view of bushed bush vicinity which concerns on 2nd Embodiment.
FIG. 2A is an explanatory diagram of a prior art.
(B) It is explanatory drawing which shows the movement of the hydraulic fluid in a gas spring accompanying opening and closing of a back door.
(C) It is explanatory drawing of the attachment state to a reversing type back door.
[Explanation of symbols]
SD Gas spring 1 Piston rod 2 Cylinder 4 Seal 8 Piston 103 Guide 113, 213 Bushing 213A Seal lip

Claims (2)

In a gas spring that is fastened to a piston slidably mounted on a cylinder and guided by a guide member fixed to the end of the cylinder, a piston spring that protrudes freely from the cylinder.
The guide member
A guide made of a resin added with glass fiber so as to be softened in a high heat environment and release high-pressure gas in the gas spring to the atmosphere, and guaranteed in mechanical strength;
A flanged bush to back up the seal has a flange covering the end portion of the in contact with the inner surface of the cylinder guide of the cylinder inner side with and sliding properties is formed a guaranteed resin for guiding the piston rod , divided and made into shaft seal device for a gas spring, characterized in that these 2 components were fitted bound. 2. The shaft seal device for a gas spring according to claim 1, wherein a seal lip for preventing foreign matter such as dust and a thin film sheet from entering the fitting gap is formed on the atmosphere side of the bush with a flange.

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