Gasket

Abstract

To provide a gasket which can inhibit entry of moisture into a joint part between a core body part and a seal part to maintain joint strength of the joint part for a long time.SOLUTION: A gasket 10 is a member attached between two members, a first member 1 and a second member 2, which are joined to each other. The gasket 10 includes an annular core body part 20 and a seal part 30 which is integrally molded with the inner periphery side 5 of the core body part 20 and made of an elastomer. A water repellent finish is added on a surface of the core body part 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gasket attached between two members, a first member and a second member, which are joined to each other.

Background Art

[0002] As this type of gasket, for example, like a metal gasket, those having an annular core portion and integrally provided with a seal portion made of an elastic material on the inner peripheral side thereof have been variously implemented (see, for example, Patent Document 1).

[0003] In order to ensure the sealing performance between the first member and the second member, such a gasket in which two members are joined requires not only the sealing performance of the seal portion itself, but also strengthening the joint portion between the core portion and the seal portion so that the joint strength of both portions does not weaken. For this purpose, for example, in Patent Document 1, at a plurality of locations in the circumferential direction, a part of the seal portion is made to bite into the core portion to physically strengthen the integration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, as a countermeasure for strengthening the joint portion between the core portion and the seal portion, not only the physical integration as described above is required, but it is also necessary to prevent deterioration of the joint portion by an adhesive between the core portion and the seal portion.

[0006] In particular, there is a risk that the adhesive hardened due to the influence of moisture such as salt water deteriorates and the joint strength decreases, and sufficient countermeasures are required. Conventionally, however, no gasket has been proposed that takes measures against moisture for the joint portion.

[0007] The present invention is a novel invention proposed by paying attention to the above points, and its object is to provide a gasket capable of suppressing the entry of moisture into the joint between the core part and the seal part, and maintaining the joint strength of the joint for a long period of time.

Means for Solving the Problems

[0008] In order to achieve the above object, the gasket of the present invention is a gasket attached between two members, a first member and a second member, which are joined to each other, and includes an annular core part and a seal part made of an elastic material integrally formed on the inner peripheral side of the core part, and the surface of the core part is subjected to a water-repellent treatment.

Effects of the Invention

[0009] Since the gasket of the present invention has the above configuration, it is possible to suppress the entry of moisture into the joint between the seal parts, and maintain the joint strength of the joint for a long period of time.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, the basic configuration of the gasket 10 according to the embodiment described below will be described.

[0012] The gasket 10 is a member attached between two members, namely the first member 1 and the second member 2, which are joined together. The gasket 10 includes an annular core portion 20 and a seal portion 30 made of an elastic material integrally formed on the inner peripheral side 5 of the core portion 20. The surface of the core portion 20 (at least the upper surface 21) is subjected to a water-repellent treatment.

[0013] Here, as a method of the water-repellent treatment, roughening treatment is desirable, but a water-repellent coating may also be used. In the following embodiments, roughening treatment is performed. In addition, examples of the roughening treatment of the surface of the core portion 20 include physical and chemical treatments such as shot blasting, laser, etching, dipping treatment, and pressing.

[0014] Further, the surface of the core portion 20 on which the water-repellent treatment is performed is not limited to only the upper surface 21, and may include the lower surface 22, end faces 23, and 24. It is desirable that the water-repellent treatment of the core portion 20 be performed before being integrated with the seal portion 30.

[0015] Next, the detailed configuration of the gasket 10 according to the embodiment will be described with reference to FIGS. 1 to 3. In this specification, in the state where the gasket 10 is attached between two members, the gasket 10 will be described with the first member 1 side as the upper side and the second member 2 side as the lower side.

[0016] FIG. 1 is a plan view of the gasket 10 which is an example of this embodiment. The gasket 10 includes an annular core portion 20 made of a metal material such as aluminum, and a seal portion 30 made of an elastic material integrally formed on the core portion 20. The core portion 20 is disposed on the outer peripheral side 6 in the annular shape, and the seal portion 30 is disposed on the inner peripheral side 5. The integration of the core portion 20 and the seal portion 30 may be achieved by molding or bonding of molded articles.

[0017] In addition, 40 in FIG. 1 is a joint portion between the core portion 20 and the seal portion 30. Also, 25 in FIG. 1 is a bolt attachment portion for attaching the gasket 10 to the first member 1 or the second member 2.

[0018] The core part 20 is formed by punching a metal material plate having rigidity such as a cold-rolled steel plate or a stainless steel plate, or by injection molding using a thermoplastic resin material. A seal part 30 is integrally formed and fixed to the end face 24 on the inner peripheral side 5 of the core part 20. Note that the core part 20 is not limited to a metal material and may be a hard synthetic resin such as a thermoplastic resin.

[0019] In the present embodiment, as shown in Fig. 2(a), the first member 1 is arranged to cover the second member 2 from above. Examples of the first member 1 and the second member 2 include a heat exchanger cover and an exchanger of an internal combustion engine, a cylinder block, an oil pan, etc. In addition, examples of the materials of the first member 1 and the second member 2 include a metal material and a synthetic resin material.

[0020] The gasket 10 of the present embodiment is a member that seals between the opposing surface 1a of the first member 1 and the opposing surface 2a of the second member 2 to suppress the entry of moisture and the like into the inner peripheral side 5. The planar shapes of the opposing surfaces 1a and 2a of the first member 1 and the second member 2 are made to match the shape in the plan view of the gasket 10 shown in Fig. 1.

[0021] As shown in Figs. 2(a) to (c), the cross-sectional shape corresponding to the X-X line of the core part 20 in Fig. 1 is substantially square, and a seal part 30 is fixed to the end face 24 on the inner peripheral side 5 of the core part 20. The joint part 40 between the core part 20 and the seal part 30 is, in a cross-sectional view, composed of the joint of end faces having substantially the same dimensions and substantially the same shape with the core part 20 and the seal part 30 not being displaced vertically with respect to each other. Note that the joint part 40 is not limited to being formed by butting flat surfaces as shown, and may be formed by meshing uneven surfaces, for example.

[0022] The core part 20 and the seal part 30 are adhered by an adhesive according to the material of the seal part 30. Examples of the elastic material of the seal part 30 include fluororubber (FKM), acrylic rubber (ACM), ethylene acrylate rubber (AEM), hydrogenated nitrile rubber (HNBR), nitrile butadiene rubber (NBR), etc.

[0023] The seal portion 30 includes, in a cross-sectional view, an inner portion 36 and an outer portion 35 located at a position protruding above and below the inner portion 36. Protrusions 37 are formed on the upper and lower surfaces of the inner portion 36. The protrusions 37 protrude to such an extent that they are within the vertical position range of the outer portion 35.

[0024] In other words, as shown in FIG. 2(a), etc., the seal portion 30 includes a substantially square base portion 31 in a cross-sectional view, a first convex portion 32 on the inner peripheral side 5 provided on the upper and lower surfaces of the base portion 31, and a second convex portion 33 (protrusion 37) on the outer peripheral side 6 relative to the first convex portion 32, having a smaller width dimension than the first convex portion 32 and a smaller protruding dimension than the first convex portion 32. Also, the first convex portion 32 and the second convex portion 33 are arranged along the inner peripheral side 5 to the outer peripheral side 6 with a concave groove portion 34 in between.

[0025] When the gasket 10 properly seals between the first member 1 and the second member 2, at least the first convex portion 32 elastically contacts the opposing surface 1a of the first member 1 and the opposing surface 2a of the second member 2, respectively. The concave groove portion 34 is a relief space for the elastic material when the first convex portion 32 and the second convex portion 33 are elastically deformed.

[0026] Also, since there is no vertical displacement between the joining portion 40 between the core portion 20 and the seal portion 30, that is, both the upper surface and the lower surface are flush between the core portion 20 and the seal portion 30, even when the first convex portion 32 and the second convex portion 33 are elastically deformed, the degree of elastic deformation of the seal portion 30 in the vertical direction as a whole is limited by the vertical positions of the upper surface 21 and the lower surface 22 of the core portion 20.

[0027] Note that the seal portion 30 is not limited to such a shape, and it may have protrusions protruding from the upper surface 21 and the lower surface 22 of the core portion 20, as long as they elastically contact the opposing surface 1a of the first member 1 and the opposing surface 2a of the second member 2.

[0028] FIG. 2(a) shows a state where the gasket 10 properly seals between the first member 1 and the second member 2. In the sealed state, a gap 41 is formed between the upper surface 21 of the core part 20 and the opposing surface 1a of the first member 1, and between the lower surface 22 of the core part 20 and the opposing surface 2a of the second member 2, respectively.

[0029] In the gasket 10 of this figure, at least the upper surface 21 of the core part 20 is subjected to a water-repellent treatment by roughening. Of course, as described above, the lower surface 22, end faces 23, 24 of the core part 20 may also be subjected to a water-repellent treatment. Any of the above-described roughening treatments may be used.

[0030] FIG. 2(b) is a diagram schematically showing a state where moisture such as salt water (water containing sodium chloride) has entered the gap 41. Since the upper surface 21 of the core part 20 is subjected to a water-repellent treatment, the moisture that has entered the gap 41 is repelled and becomes water droplets 45.

[0031] Thus, on the upper surface 21 of the core part 20, the contact area between the water droplet 45 and the upper surface 21 is small, and the spread of the water droplet 45 in the direction of the joint part 40 is also small. Therefore, the moisture that has entered the upper surface 21 of the core part 20 hardly reaches the joint part 40. As a result, the cured adhesive at the joint part 40 hardly deteriorates, the joint strength can be maintained for a long time, and adhesive peeling can be prevented.

[0032] Also, as the gaps 41 between the core part 20 and the first member 1 and the second member 2 when the gasket 10 is properly installed, various vertical dimensions are assumed depending on the type of product to which the gasket 10 is to be attached (having the first member 1 and the second member 2), etc.

[0033] For example, even when the gap 41 is a minute interval and water droplets 45 as shown in FIG. 2(b) cannot be formed, the flow of moisture to the joint part 40 can be suppressed by the water-repellent action of the upper surface 21. In the first place, if the gap 41 is minute, the entry of moisture from the outer peripheral side 6 into the gap 41 is suppressed by the action of the water-repellent surfaces of the end face 23, upper surface 21, and lower surface 22 of the outer peripheral side 6 of the core part 20 subjected to the water-repellent treatment.

[0034] Further, as shown in FIG. 2(c), in the gasket 10 where the upper surface 21 of the core body portion 20 slopes downward from the inner peripheral side 5 toward the outer peripheral side 6, water droplets 45 flow more easily toward the outer peripheral side 6, and it becomes difficult for the water droplets 45 to flow toward the inner peripheral side 5. Therefore, the effect of suppressing water entry into the joint portion 40 is further increased.

[0035] Note that FIG. 2(d) is a cross-sectional view of the gasket 100 in which the upper surface 21 of the core body portion 20 is not subjected to a water repellent treatment. As shown in this figure, the moisture that has entered the gap 41 easily spreads thinly, and the thinly spread moisture 46 easily reaches the joint portion 40.

[0036] Also, it is desirable that the lower surface 22 of the core body portion 20 and the end face 23 of the outer peripheral side 6 are also subjected to a water repellent treatment. Similar to the case of the upper surface 21, if the lower surface 22 is subjected to a water repellent treatment, it becomes difficult for moisture to reach the joint portion 40. In addition, the lower surface 22 may also be inclined downward toward the outer peripheral side 6 in order to flow the water droplets 45 adhering to the lower surface 22 toward the outer peripheral side 6.

[0037] Also, if the end face 23 of the outer peripheral side 6 is subjected to a water repellent treatment, it is possible to make it difficult for moisture trying to enter from the outer peripheral side 6 to enter the gap 41. Note that as the water repellent treatment for the end face 23, a roughening treatment for substantially the entire surface by immersion in a solution is desirable. This is because the gasket 10 has a smaller thickness dimension on the side surface (end face) compared to the plane, and physical methods such as shot blasting are difficult.

[0038] Also, when a water repellent treatment is applied to the surface by a roughening treatment, there is a possibility that the convex portions (not shown) of the uneven surface of the core body portion 20 subjected to the water repellent treatment come into contact with the opposing surface 1a of the first member 1 or the opposing surface 2a of the second member 2. When contacting in this way, the concave portions (not shown) of the uneven surface may not contact the opposing surface 1a of the first member 1 or the opposing surface 2a of the second member 2. That is, the possibility of the entire surfaces contacting each other is low.

[0039] In this way, by roughening the surface of the core part 20, the contact area with the first member 1 and the second member 2 becomes smaller. Therefore, the current flowing between the first member 1 and the second member 2 is smaller than that of a non-water-repellent processed one. Thus, the attachment of this gasket 10 can also be a measure against electric corrosion.

[0040] Further, by performing water-repellent processing on the surface of the core part 20 with a coating agent having no conductivity, electric corrosion prevention may be achieved by configuring so that no current flows between the first member 1 and the second member 2.

[0041] Next, the water-repellency test regarding the roughened core part 20 will be described with reference to FIG. 3. FIG. 3(a) is a list showing the test results for each test case, and FIG. 3(b) is an explanatory diagram of the contact angle θ. The purpose of this test is to determine the appropriate water-repellent performance of the core part 20.

[0042] In FIG. 3(a), the item "roughness Rz" is the ten-point average roughness Rz which is one of the indexes of the surface roughness, and the item "roughness Ra" is the arithmetic average roughness Ra which is one of the indexes of the surface roughness. Tests were conducted on 7 cases, and for each case, the roughness Rz and the roughness Ra were calculated, and the contact angle θ was measured from a photograph of the water droplet 45. In the list of FIG. 3(a), the numerical value of the contact angle θ and the cross-sectional view of the water droplet 45 based on the photograph are attached as items. The test conditions are as follows.

[0043] As test pieces, 50 aluminum test pieces with a diameter of 25 mm and a plate thickness of 1.6 mm were used. As the roughening treatment of the surface of the aluminum test piece 50, etching treatment was adopted. As the etching agent, for NO.1 to NO.6 in FIG. 3(a), a first liquid (alkaline solution) and a second liquid (acidic solution) were used. For NO.7, only the first liquid (alkaline solution) was used. For NO.1 to NO.6, they were classified into cases by varying conditions such as the concentration of the solution and the treatment time. Pure water was used as the water to be dripped onto the aluminum test piece 50.

[0044] The inventor determined that those with a contact angle θ of 120 degrees or more obtained by actually measuring the cross-sectional shape of the water droplets 45 in the list by photography were appropriate as the surface state of the core part 20 of the gasket 10. In the present embodiment, it was determined that the contact angle θ being 120 degrees or more would be judged by the numerical values of the roughness Rz and the roughness Ra.

[0045] As test cases where a result of the contact angle θ of 120 degrees or more was obtained, NO.3 to NO.7 are applicable. Among these, NO.7 in which both the roughness Rz and the roughness Ra are significantly lower than those of NO.3 to NO.6 was excluded.

[0046] For the test cases of NO.3 to NO.6, the minimum value of the roughness Rz is 6.4 μm and the maximum value is 7.22 μm. Since the roughness Rz of other cases is less than 5 μm, it was set as a pass criterion condition for an appropriate water-repellent surface that the roughness Rz is 5 μm or more. Although the upper limit value of the roughness Rz is not particularly defined, it may be 13 μm, for example.

[0047] Also, the pass criterion may be determined by the roughness Ra. However, from the list, in the case of NO.2, the contact angle θ is 117.6 degrees and it is almost a pass. However, between NO.2 with a contact angle θ of 117.6 degrees and NO.1 with a contact angle θ of 95.7 degrees, the magnitude relationship of the numerical values of the roughness Rz and the magnitude relationship of the numerical values of the roughness Ra are in reverse relationships. Therefore, it is difficult to adopt the roughness Ra as the pass criterion. That is, for example, if the lower limit value of the pass criterion for the roughness Ra is set to 0.8 μm, then NO.2 will be unqualified, and if the lower limit value of the pass criterion for the roughness Ra is set to 0.7 μm, then NO.1 with a contact angle of 95.7 degrees will be qualified, which is inconvenient.

[0048] Therefore, it was determined that it is more appropriate to use the roughness Rz rather than the roughness Ra as the threshold value for the pass criterion. In addition, in order to more precisely judge the range of the contact angle θ of NO.3 to NO.6, it may be set as a pass criterion that the roughness Ra is 1.0 μm or more and 1.1 or less.

[0049] As described above, in order to obtain an appropriate contact angle θ with the numerical value of the roughness Rz, it is sufficient to conduct tests by varying various conditions of the etching process. Also, for any other roughening process, appropriate upper and lower limit values of the roughness Rz can be obtained by varying the conditions. The same applies when adopting the roughness Ra.

[0050] In addition, if the roughening process of the surface of the core part 20 is carried out before integration with the seal part 30, the end face 24 on the inner peripheral side 5 will also be subjected to water repellent treatment. In that case, it is necessary to make the roughness such that the adhesiveness with the seal part 30 can be ensured. Therefore, it is desirable to adjust the upper and lower limit values of the roughness Rz and the roughness Ra according to the type of the elastic material and the adhesive of the seal part 30.

[0051] Also, when the optimal water repellency (optimal roughness) for the gasket 10 inhibits the adhesiveness between the end face 24 on the inner peripheral side 5 of the core part 20 and the seal part 30, the end face 24 on the inner peripheral side 5 may be masked and then subjected to water repellent treatment, or the water repellent treatment may be carried out after fixing the seal part 30 to the core part 20.

Explanation of Reference Numerals

[0052] 10 Gasket 20 Core part 21 Upper surface (surface) 22 Lower surface (surface) 23 End face (surface) on the outer peripheral side 24 End face (surface) on the inner peripheral side 30 Seal part 31 Base part 32 First convex part 33 Second convex part 34 Concave groove part 40 Joint part 1 First member 2 Second member 5 Inner peripheral side 6 Outer peripheral side

Claims

1. A gasket attached between two members, namely a first member and a second member that are joined together, comprising an annular core portion and a seal portion made of an elastic material integrally formed on the inner peripheral side of the core portion, wherein the surface of the core portion is subjected to a water-repellent treatment.

2. In claim 1, the surface of the core portion is subjected to a water-repellent treatment by roughening treatment, and the surface roughness of the core portion has a ten-point average roughness Rz of 5 μm or more.

3. In claim 1, the upper surface of the core portion is inclined downward from the inner peripheral side toward the outer peripheral side.

4. In claim 1, substantially the entire surface including the end face of the core portion is subjected to a water-repellent treatment by roughening treatment by immersion.

Images