JP2008051210A - Gas barrier structure and forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas barrier structure capable of improving a heat radiating property of a diaphragm rubber film of a sealed hydraulic damper, and a forming method thereof. <P>SOLUTION: The gas barrier structure for a rubber film 10 constituting a diaphragm for a sealed hydraulic damper comprises an aluminum thin film 14 formed on the surface of the rubber film 10 and a flexible DLC film 18 formed on the aluminum thin film 14. The aluminum thin film 14 and the flexible DLC film 18 are bonded to each other by an aluminum-silicon eutectic layer 14 interposed between the films. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gas barrier structure of a diaphragm rubber film of a hermetic hydraulic damper and a manufacturing method thereof.

  A tappet clearance is provided to absorb dimensional changes due to thermal expansion and wear of the engine valve mechanism and to prevent the valve from being pushed up. A sealed hydraulic damper (lash adjuster) 1 shown in FIG. 1 always maintains and adjusts this tappet clearance within a specified range. In the figure, a plunger 3 is inserted into a cylindrical body (body) 2 opened upward and closed at the lower end so as to be slidable back and forth. A stem portion 4 projects from the central portion of the plunger 3, and a diaphragm 5 is attached between the upper end of the stem portion 4 and the cylindrical main body 2 so as to connect the two to each other and cover the open end.

  The diaphragm 5 is made of a rubber film having excellent oil resistance and heat resistance, such as fluorosilicone rubber and fluororubber. Various measures have been taken so far to improve the gas barrier property of the rubber film 5 so that the sealed oil in the reservoir chamber 6 covered with the diaphragm 5 does not deteriorate due to contact with outside air.

  In Patent Document 1, a gas-impermeable film is provided on the rubber film via a protective film in order to prevent damage such as cracking and peeling of the gas-impermeable film such as resin and metal adhered on the diaphragm rubber film. Furthermore, a structure covered with a protective film is disclosed.

  Furthermore, aluminum is vapor-deposited on rubber as a gas impermeable film (Non-Patent Document 1), a carbon film (DLC) is formed on the surface of a soft substrate (Patent Document 2), and a carbon film with good adhesion is formed ( Patent Document 3), a diaphragm structure of a hydraulic lash adjuster (Non-Patent Document 2) and the like are disclosed.

  However, it has been necessary to further improve the gas barrier properties as a diaphragm rubber film of a hermetic hydraulic damper.

  Therefore, we focused on the commercialization of PET bottles for beverages with a DLC film on the inner surface for the purpose of gas barrier properties of soft base materials such as rubber and plastic.

  However, even if the DLC film in the beverage bottle is directly applied to the diaphragm of the sealed hydraulic damper, sufficient gas barrier properties cannot be obtained.

  That is, referring again to FIG. 1, in the case of the sealed hydraulic damper 1, frictional heat is generated when the plunger 3 slides with the cylindrical body 2. In this case, if the conventional DLC film is coated on the diaphragm rubber film 5 as a gas barrier measure, since the heat dissipation is insufficient, the temperature of the sealed oil in the reservoir chamber 6 rises, and oil deterioration due to gelation or the like occurs. Get up.

Japanese Utility Model Publication 5-33328 JP 2002-121669 A JP 2000-96233 A Japan Society of Invention Disclosure Techniques 2004-505039 Invention Association Open Technique 2003-503805

  An object of the present invention is to provide a gas barrier structure in which the heat dissipation of a diaphragm rubber film of a hermetic hydraulic damper is improved and a manufacturing method thereof.

In order to achieve the above object, according to the present invention, a gas barrier structure of a rubber film constituting a diaphragm of a sealed hydraulic damper,
An aluminum thin film formed on the surface of the rubber film and a flexible DLC film formed on the aluminum thin film, and an aluminum / silicon eutectic layer in which the aluminum thin film and the flexible DLC film are interposed therebetween A gas barrier structure is provided which is characterized by being joined together.

Furthermore, according to the present invention, there is provided a method for producing the gas barrier structure of the present invention, comprising the following steps:
Forming the aluminum thin film on the rubber film in a hydrogen gas atmosphere at a temperature of 120 ° C. or lower; and forming the DLC film on the aluminum thin film by low temperature plasma CVD at 60 ° C. or lower. A method for producing a gas barrier structure is provided.

  In the gas barrier structure of the present invention, the gas barrier property is ensured by the flexible DLC film, and the heat dissipation can be enhanced by the heat sink action of the aluminum thin film directly in contact with the rubber film.

  Furthermore, since the flexible DLC film and the aluminum thin film are firmly joined by the aluminum / silicon eutectic layer interposed between them, the gas does not peel off due to the expansion / contraction operation of the diaphragm, and has excellent gas barrier properties and heat dissipation. You can always combine.

  In the method for producing the gas barrier structure of the present invention, the aluminum thin film is formed on the rubber film at a low temperature of 120 ° C. or less in a hydrogen gas atmosphere, whereby the aluminum thin film can be prevented from being oxidized. Further, the formation of the DLC film on the aluminum thin film is performed by low temperature plasma CVD at 60 ° C. or lower, so that the underlying aluminum thin film is not deteriorated, and even if the DLC film contains hydrogen, It can be easily dehydrogenated by heating at a low temperature of about 100 ° C.

  FIG. 2 schematically shows a gas barrier structure of a rubber film according to a preferred embodiment of the present invention.

  The illustrated gas barrier structure is configured by laminating an aluminum thin film 14, an aluminum-silicon eutectic layer 16, and a flexible DLC film 18 in this order on a rubber film 10 constituting the diaphragm 5 (FIG. 1). The surface 12 of the rubber film 10 is previously roughened by ion bombardment, and the aluminum thin film 14 is firmly bonded to the surface of the rubber film 10 by a mechanical anchor effect.

  The aluminum thin film 14 and the flexible DLC film 18 are firmly bonded to each other by an aluminum / silicon eutectic layer 16 formed therebetween. The aluminum-silicon eutectic layer 16 is generated in association with the formation process of the flexible DLC film 18. This is due to the following reasons.

  As shown in FIG. 3, the flexible DLC film 18 contains Si and H as impurities in amorphous carbon. Of these, Si is covalently bonded to C, but at the same time forms an extremely fine eutectic layer with the underlying Al. As a result, the eutectic layer firmly bonds the upper C and the lower Al.

  Thus, the gas barrier structure of the present invention is such that the base rubber film 10 is firmly bonded to the aluminum thin film 14 by the roughened surface 12, and at the same time, the aluminum thin film 14 is a flexible DLC film by the Al—Si eutectic layer. 18, the rubber film 10 can be deformed by following the expansion and contraction of the rubber film 10, and the gas barrier property by the flexible DLC film and the heat dissipation property by the aluminum thin film can be stably exhibited.

  A method of manufacturing a gas barrier structure according to a preferred embodiment of the present invention can be performed as follows.

  First, as the rubber film 10 serving as the base material, a rubber film having good oil resistance and heat resistance with fluorosilicone rubber and fluororubber is selected.

  Next, the surface 12 of the rubber film is roughened by ion bombardment with Ar ions or the like. This simultaneously cleans the rubber film surface. Both have the effect of increasing the adhesion of the aluminum thin film formed thereon.

  Next, an aluminum thin film 14 is formed on the surface of the rubber film that has been subjected to the ion bombardment treatment at a temperature of 120 ° C. or less in a hydrogen atmosphere by a low temperature film forming method such as sputtering. The film thickness is about 15 nm or less, and it also has ductility that can follow the expansion and contraction of the rubber film while ensuring sufficient thermal conductivity.

  Next, a flexible DLC film 18 is formed on the aluminum thin film 14. This is performed by the following procedures 1) to 2).

1) Pretreatment: Cleaning of the surface of the aluminum thin film In a vacuum, a natural oxide film and other contaminants on the surface of the aluminum thin film 14 are removed by hydrogen plasma cleaning to expose a fresh aluminum surface. This enhances the adhesion of the flexible DLC film. Details of this method are disclosed in Japanese Patent No. 33555892.

2) Main treatment: Formation of flexible DLC film A flexible DLC film is formed on the aluminum thin film after the purification treatment by low-temperature plasma CVD at a temperature of 60 ° C or lower. Specifically, for example, methane (CH ₄ ) and tetraethoxysilane (TEOS) are used as raw materials by the method disclosed in Patent Document 2. In this DLC formation process, Si contained by several percent as an impurity derived from the raw material forms an eutectic layer with Al of the aluminum thin film as described above, and acts as a bonding layer between the Al thin film and the DLC film. Similarly, H is also present as an impurity derived from the raw material, but this does not substantially affect the adhesion between the Al thin film and the DLC film.

  The above treatment provides a gas barrier structure according to a preferred embodiment of the present invention.

  In a more desirable embodiment, after the DLC film is formed, a post-treatment is performed in an inert gas such as nitrogen at 100 ° C. or higher for about 30 minutes to remove the residual hydrogen. Thereby, as conventionally known, the thermal conductivity of the DLC film is improved by removing hydrogen.

  The dehydrogenated DLC film is estimated to have a high thermal conductivity of about 300 W / mk. This is an extremely high thermal conductivity, whereas the thermal conductivity obtained with a DLC film not containing Si is several tens of W / mk. In general, the thermal conductivity obtained with an aluminum vapor deposition film is rather high as compared with 170 to 200 W / mk, and the action of the aluminum thin film as a heat sink on the rubber film can be effectively utilized. High heat dissipation can be realized.

  Further, when the aluminum thin film is formed, the aluminum thin film is wrinkled when the rubber is returned to the original state by applying the rubber in a tensioned state, and there is a method of forming a DLC film in that state. According to this method, cracks do not occur in the aluminum film or the DLC film even if the film is expanded or contracted in the product state.

  As described above, the gas barrier structure of the present invention combines the gas barrier property and heat dissipation of the diaphragm, so that even if frictional heat is generated by sliding between the plunger and the main body, the temperature rise of the sealed oil is suppressed. It is possible to improve the operating life by suppressing thermal deterioration of the encapsulated oil and the diaphragm.

  As described above, according to the present invention, there are provided a gas barrier structure in which the heat radiation property of the diaphragm rubber film of the hermetic hydraulic damper is improved and a manufacturing method thereof.

It is a longitudinal cross-sectional view of the sealing type hydraulic damper (lash adjuster) provided with the diaphragm which applies the gas barrier structure of this invention. It is sectional drawing of the gas barrier structure of this invention. It is a schematic diagram which shows the molecular structure of a flexible DLC film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rubber film 12 Roughened surface of rubber film 10 Aluminum thin film 16 Al-Si eutectic layer 18 Flexible DLC film

Claims (4)

A gas barrier structure of a rubber film constituting a diaphragm of a sealed hydraulic damper,
An aluminum thin film formed on the surface of the rubber film and a flexible DLC film formed on the aluminum thin film, and an aluminum / silicon eutectic layer in which the aluminum thin film and the flexible DLC film are interposed therebetween A gas barrier structure characterized by being bonded to each other.   2. The gas barrier structure according to claim 1, wherein the aluminum thin film is formed on an ion bombarded roughened surface of the rubber film. A method for producing a gas barrier structure according to claim 1, wherein:
Forming the aluminum thin film on the rubber film in a hydrogen gas atmosphere at a temperature of 120 ° C. or lower; and forming the DLC film on the aluminum thin film by low temperature plasma CVD at 60 ° C. or lower. A method for producing a gas barrier structure characterized by comprising:   3. The method for producing a gas barrier structure according to claim 2, further comprising a step of roughening a surface of the rubber film by ion bombarding before the step of forming the aluminum thin film. Manufacturing method.

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