Connection structure for conductive rubber member

Abstract

To provide a connection structure for a conductive rubber member which can prevent galvanic corrosion from generating in a metal tightening member at low cost without any defect, in a connection structure including a metal tightening member for tightening and connecting a tubular or ring-shaped conductive rubber member including free sulfur to a pipe to be inserted thereto.SOLUTION: A connection structure includes: a conductive rubber member 20 including free sulfur S; a pipe inserted into the conductive rubber member 20; and a tightening member 10 for tightening and connecting the conductive rubber member to the pipe. The tightening member 10 includes: a metal member body 11; a non-conductive coating film 12 that is formed at a contact surface of the member body 11 to the conductive rubber member 20; and zinc oxide particulates or zeolite particulates 13 included in the coating film 12.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a connection structure for conductive rubber members, and more particularly to a connection structure that includes a metal fastening member that fastens and connects a tubular or ring-shaped conductive rubber member containing free sulfur to a pipe that is inserted into the conductive rubber member. [Background technology]

[0002] Conductive rubber hoses are used in automobiles and other vehicles to prevent ignition due to static electricity that can occur between the rubber hose and the fuel. These hoses are able to dissipate static electricity from the hose to the outside. The most common method for imparting conductivity is to disperse conductive fillers such as carbon or metals into the rubber. Carbon black, in particular, is widely used because it achieves conductivity with a small amount of additive. However, carbon has a natural potential that is more noble than silver (Ag) and copper (Cu), which means that it can cause galvanic corrosion with most metals except for gold (Au) and platinum (Pt).

[0003] In order to prevent galvanic corrosion from occurring in a metal tube connected to a rubber hose, Patent Document 1 describes a method in which a piping system having a metal tube, a flexible hose, and a connection between the two is provided with a coating made of a non-metallic material on the outer periphery of the metal tube near the open end face of the flexible hose when the metal tube is inserted into the flexible hose. Patent Document 1 gives an example of a thermoplastic synthetic resin material such as a polyethylene resin as this non-metallic material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-101390 Summary of the Invention [Problem to be solved by the invention]

[0005] In the typical manufacturing process of rubber hoses and rings, a mandrel is inserted into the inner surface, and the outer surface is left exposed while undergoing a vulcanization process, resulting in unevenness on the outer surface. When a metal fastening member such as a clip or clamp is attached to the outer periphery of such a rubber hose or ring, these unevenness creates many gaps at the contact surface between the rubber product and the fastening member. If water penetrates these gaps, electrical conduction occurs between the conductive filler, such as carbon, in the rubber product and the metal surface of the fastening member, rapidly progressing the galvanic corrosion described above.

[0006] Rubber products are typically vulcanized with sulfur, leaving trace amounts of free sulfur, which is a sulfur component that does not participate in the crosslinking reaction and is unbonded or weakly bonded to rubber molecules. When the rubber product is in use, this free sulfur converts to hydrogen sulfide (H2S) due to temperature rises and other factors, and is released to the outside as hydrogen sulfide gas. It also converts to hydrogen sulfide when it reacts with water that has penetrated into gaps. Even trace amounts of hydrogen sulfide penetrate organic and inorganic materials and strongly accelerate their deterioration. Therefore, if hydrogen sulfide penetrates the nonmetallic coatings used to prevent galvanic corrosion, the deterioration progresses, causing the coating to peel off or disappear, resulting in a loss of its effectiveness in preventing galvanic corrosion.

[0007] Countermeasures against deterioration caused by hydrogen sulfide include thickening the coating or using sulfur-resistant electrodeposition coating, but because the fastening components of clips and clamps must be deformed during installation, applying a thick surface treatment such as electrodeposition coating makes the components less likely to deform, making installation difficult and causing problems such as cracking and peeling of the coating. Another countermeasure is to prevent galvanic corrosion by using gold or platinum, which have a natural potential equally or more noble than carbon, as the base material or plating, but this has the problem of gold and platinum being very expensive.

[0008] In view of the above problems, the present invention aims to provide a connection structure for conductive rubber members that includes a metal fastening member that fastens and connects a tubular or ring-shaped conductive rubber member containing free sulfur to a pipe that is inserted into the conductive rubber member, and that can prevent galvanic corrosion from occurring in the metal fastening member at low cost and without any problems. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a connection structure comprising a tubular or ring-shaped conductive rubber member containing free sulfur, a pipe inserted into the conductive rubber member, and a fastening member that fastens and connects the conductive rubber member to the pipe, wherein the fastening member comprises a metal member body, a non-conductive coating formed on the contact surface of the member body with the conductive rubber member, and zinc oxide particles or zeolite particles contained in the coating. [Effects of the Invention]

[0010] Thus, according to the present invention, the non-conductive coating formed on the metal body of the fastening member contains zinc oxide particles or zeolite particles, so that even if the free sulfur contained in the conductive rubber member is converted into hydrogen sulfide, the zinc oxide particles or zeolite particles can neutralize the hydrogen sulfide, thereby maintaining the effect of preventing galvanic corrosion of the conductive rubber member. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically showing an embodiment of a connection structure for conductive rubber members according to the present invention. [Figure 2] 2 is a partially enlarged cross-sectional view schematically showing a fastening member of the connection structure shown in FIG. 1. FIG. [Figure 3] 2 is a partially enlarged cross-sectional view showing the connection structure within the dotted frame II in FIG. 1. FIG. [Figure 4] FIG. 10 is a partially enlarged cross-sectional view showing a connection structure of a comparative example in which the fastening member does not have a non-conductive coating. [Figure 5] FIG. 10 is a partially enlarged cross-sectional view showing a connection structure of a comparative example in which zinc oxide particles are not present in the non-conductive coating of the fastening member. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a connection structure for conductive rubber members according to the present invention will be described with reference to the accompanying drawings. Note that the drawings are illustrated to make the configuration simple and clear, and are not necessarily drawn to scale.

[0013] 1, the connection structure for conductive rubber members of this embodiment mainly comprises a conductive rubber hose 20, a pipe 30 inserted into this conductive rubber hose 20, and a metallic fastening member 10 that fastens and connects the conductive rubber hose 20 to the pipe 30. This allows a fluid 1, such as gasoline, to flow from the conductive rubber hose 20 to the pipe 30.

[0014] The rubber material that is the main component of conductive rubber hose 20 is not particularly limited as long as it is a rubber material used for hoses, but it is preferable to use, for example, epichlorohydrin rubber (ECO), acrylonitrile butadiene rubber (NBR), fluororubber (FKM), chlorosulfonated polyethylene rubber (CSM), etc. Rubber hoses that contain these as their main components have the flexibility required for a rubber hose and also exhibit excellent impermeability to gasoline, making them suitable for use as fuel hoses for automobiles.

[0015] Furthermore, conductive fillers (not shown) such as carbon (C) and metals are added to the conductive rubber hose 20 to impart conductivity. Examples of carbon include carbon black, graphite, and carbon fiber. Examples of metals include silver (Ag), copper (Cu), and stainless steel. Among these, carbon black is particularly preferred because it can provide conductivity with a small amount added. Furthermore, the conductive rubber hose 20 contains a trace amount of free sulfur (S).

[0016] The pipe 30 is not particularly limited as long as it can be inserted into the conductive rubber hose 20 and can be connected to the conductive rubber hose 20 by the fastening member 10, but a metal pipe 30 is preferred. The metal material is not particularly limited, but examples include iron (Fe), aluminum (Al), and alloys thereof.

[0017] The fastening member 10 has a structure that fastens the conductive rubber hose 20 from its outer surface as shown by the arrow in FIG. 1 in order to prevent the pipe 30 from coming loose from the conductive rubber hose 20, and although not limited thereto, it is preferable that the fastening member 10 has a structure such as a clip or clamp.

[0018] 2, the fastening member 10 comprises a metal member body 11, a non-conductive coating 12 formed on the surface of the member body 11, and zinc oxide (ZnO) particles 13 contained in the non-conductive coating 12. The non-conductive coating 12 must be formed on at least the surface that comes into contact with the conductive rubber hose 20, but may be formed on the entire surface of the member body 11.

[0019] The metal material of the component body 11 is not particularly limited as long as it has a lower potential than the conductive filler of the conductive rubber hose 20 and is strong enough to fasten the conductive rubber hose 20 to the pipe 30, but examples include iron (Fe), aluminum (Al), zinc (Zn), magnesium (Mg), and alloys thereof.

[0020] The material for the non-conductive coating 12 is not particularly limited as long as it can prevent galvanic corrosion by interrupting conduction between the component body 11 and the conductive rubber hose 20, and organic materials, inorganic materials, and composite materials of organic and inorganic materials can be used. For example, organic materials include epoxy and phenolic resin materials, inorganic materials include glass and ceramics, and composite materials of organic and inorganic materials include silicates using the above resin materials as binders.

[0021] The zinc oxide particles 13 contained in the non-conductive coating 12 can prevent deterioration of the non-conductive coating 12 even if free sulfur contained in the conductive rubber hose 20 is released as hydrogen sulfide into the non-conductive coating 12, and have the function of maintaining the prevention of galvanic corrosion by the non-conductive coating 12. This will be described in detail with reference to Figs. 3 to 5.

[0022] First, as shown in Figure 4, the outer surface 21 of the conductive rubber hose 20 has irregularities (heights of several microns to several tens of microns), so even when fastened with the fastening member 10, many gaps of several microns to several tens of microns are formed between the conductive rubber hose 20 and the fastening member 10. In particular, when the fastening member 10 is a clip, the only fastening force is the elastic force of the spring, so the surface pressure on the contact surface is lower than in the case of a clamp, and gaps are more likely to occur. When this connection structure is used, water 2 penetrates into these gaps.

[0023] Figure 4 shows a comparative example in which the clamping member 10 does not have a non-conductive coating 12, and the metallic member body 11 comes into direct contact with the conductive rubber hose 20. In this case, water 2 seeps into gaps created by the unevenness, causing conduction between the conductive filler such as carbon in the conductive rubber hose 20 and the metal surface of the member body 11, as shown by the arrow in Figure 4, resulting in galvanic corrosion, and corrosion 15 of the member body 11 of the clamping member 10 progressing rapidly.

[0024] To prevent such galvanic corrosion, Figure 5 shows a comparative example in which a non-conductive coating 12 is provided on a fastening member 10, but the non-conductive coating 12 does not contain zinc oxide particles 13. This non-conductive coating 12 prevents electrical conduction between the conductive filler, such as carbon, in the conductive rubber hose 20 and the metal surface of the member body 11, thereby preventing the occurrence of galvanic corrosion. However, the conductive rubber hose 20 contains free sulfur (S), which can be converted to hydrogen sulfide (HS) due to temperature rise or can react with water 2 that has entered the gap to generate hydrogen sulfide as follows: 3S+2H2O→2H2S+SO2

[0025] Hydrogen sulfide deteriorates the non-conductive coating 12, causing it to partially peel off or disappear, resulting in holes 16 in the non-conductive coating 12. This prevents the non-conductive coating 12 from being effective in preventing galvanic corrosion.

[0026] In contrast to these comparative examples, in this embodiment, as shown in FIG. 3, hydrogen sulfide generated from the conductive rubber hose 20 reacts with zinc oxide particles 13 dispersed in the non-conductive coating 12 as follows, and is converted into zinc sulfide (ZnS) and water. ZnO+H2S → ZnS+H2O

[0027] Zinc sulfide does not deteriorate the non-conductive coating 12, but can significantly suppress the progression of deterioration due to the penetration of hydrogen sulfide, thereby maintaining the effect of preventing galvanic corrosion. The amount of free sulfur contained in the conductive rubber hose 20 is very small, and after the conductive rubber hose 20 is used for a certain period of time, most of the free sulfur is released as hydrogen sulfide, and the free sulfur is depleted, and hydrogen sulfide is no longer generated. Therefore, although zinc oxide particles 13 are consumed as zinc sulfide particles 14 through the above reaction, as long as a certain amount of zinc oxide particles 13 is contained in the non-conductive coating 12, hydrogen sulfide generated from the conductive rubber hose 20 can be sufficiently converted into zinc sulfide.

[0028] The zinc oxide particles 13 do not need to be exposed on the surface of the non-conductive coating 12, and can be converted to zinc sulfide through the above-mentioned reaction with hydrogen sulfide even if they are embedded in the non-conductive coating 12. The thicker the non-conductive coating 12, the more effective it is in preventing galvanic corrosion. However, if the coating is too thick, the workability of the fastening member 10 decreases and the coating is more likely to crack or peel off, so the thickness is preferably 3 μm to 300 μm, and more preferably 10 μm to 100 μm, for example.

[0029] The average particle size of the zinc oxide particles 13 is not particularly limited, but is preferably 0.02 μm to 3 μm, and more preferably 0.1 μm to 1 μm. The amount of the zinc oxide particles 13 to be blended is, for example, 0.2 to 15 g / m in terms of weight per area of ​​the non-conductive coating 12. 2 is preferable, and 0.5 to 5 g / m 2 is more preferred.

[0030] Note that, even when zeolite particles are used instead of zinc oxide particles 13, peeling or loss of non-conductive coating 12 due to hydrogen sulfide can be prevented, just like zinc oxide particles. Unlike zinc oxide particles, which convert hydrogen sulfide into zinc sulfide, zeolite can prevent peeling or loss of non-conductive coating 12 by capturing hydrogen sulfide in its network structure.

[0031] The average particle size of the zeolite particles is not particularly limited, but is preferably 0.02 μm to 3 μm, more preferably 0.1 μm to 1 μm. The amount of the zeolite particles to be blended is, for example, 0.1 to 12 g / m2 in terms of weight per area of ​​the non-conductive coating 12. 2 is preferable, and 0.4 to 4 g / m 2 is more preferred.

[0032] In this embodiment, the connection structure of the conductive rubber hose 20 has been described as a conductive rubber member, but the present invention is not limited to this. Even if the conductive rubber member is a ring-shaped member such as an O-ring or packing that is connected to a pipe, it can prevent galvanic corrosion of the fastening member that fastens and connects the ring-shaped conductive rubber member to the pipe 30, just like the conductive rubber hose. [Explanation of symbols]

[0033] 1 fluid 2 water 10 Fastening member 11. Main body of component 12 Non-conductive coating 13 Zinc oxide particles 20 Conductive rubber hose 21 Outer surface 30 Pipe

Claims

1. A connection structure comprising a tubular or ring-shaped conductive rubber member containing free sulfur, a pipe inserted into the conductive rubber member, and a fastening member that fastens and connects the conductive rubber member to the pipe, wherein the fastening member comprises a metal member body, a non-conductive coating formed on the contact surface of the member body with the conductive rubber member, and zinc oxide particles or zeolite particles contained in the coating.

2. 2. The connection structure according to claim 1, wherein the conductive rubber member is a fuel hose whose main component is epichlorohydrin rubber (ECO), acrylonitrile butadiene rubber (NBR), fluororubber (FKM), or chlorosulfonated polyethylene rubber (CSM).

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