Seal member and vehicle suspension

Abstract

To provide a configuration for a seal member formed of a rubber composition that allows further enhancement of tensile strength and elongation.SOLUTION: The seal member of the present invention has a rubber composition containing porous carbon ceramics in a range of 0.5 to 2.9 mass%. The porous carbon ceramics are RH ceramics obtained by firing rice husks, or RB ceramics obtained by firing rice bran.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a seal member made of a rubber composition and a vehicle suspension equipped with the seal member. [Background technology]

[0002] Seal members made of rubber compositions are widely used in practice, and among them, a seal member made of a rubber composition containing porous carbon ceramics is known (see, for example, Patent Document 1).

[0003] The sealing member disclosed in Patent Document 1 contains porous carbon ceramic particles having a particle size of 5 μm or more and 90 μm or less in a proportion of 3 mass % or more and 40 mass % or less (Patent Document 1, Claims 1 and 2).

[0004] The proportion of porous carbon ceramics is limited to a range of 3 mass % to 40 mass %, which makes it possible to further reduce friction (Patent Document 1, paragraph 0015).

[0005] However, if the proportion of porous carbon ceramics is in the range of 3 mass % to 40 mass %, the tensile product will be 200 to 800 MPa·% (Patent Document 1, Figure 4). The tensile product is the product of tensile strength and elongation.

[0006] However, there are a wide variety of requirements placed on sealing members, and for some requirements, the tensile strength and elongation achieved by the technology of Patent Document 1 are insufficient, and an increase in these is required. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6519789 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a sealing member made of a rubber composition that can achieve further increases in tensile strength and elongation. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a sealing member made of a rubber composition containing porous carbon ceramics in an amount ranging from 0.5 to 2.9% by mass. Preferably, the porous carbon ceramics is RH ceramics made by firing rice husks or RB ceramics made by firing rice bran. More preferably, the porous carbon ceramic has a particle size of 10 μm or less. [Effects of the Invention]

[0010] According to the present invention, further increases in the tensile strength and elongation of the sealing member can be achieved. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating the structure of a vehicle suspension provided with a sealing member according to the present invention; [Figure 2] 1 is a graph showing the particle size distribution of the porous carbon ceramics employed in the present invention. [Figure 3] Graph (a) shows the relationship between RHS content and relative elongation, and graph (b) is an enlarged view of a main part of graph (a). [Figure 4] 1 is a graph comparing relative tensile strength. [Figure 5] 1 is a graph comparing coefficients of dynamic friction. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described below with reference to the accompanying drawings. [Example]

[0013] As shown in Figure 1, the vehicle suspension 10 is, for example, a front suspension for a motorcycle. The vehicle suspension 10 is a shock absorber in which an inner tube 12 on the axle side is slidably inserted into an outer tube 11 on the vehicle body side, a spring 13 is provided inside the outer tube 11 and the inner tube 12, a damper 14 is housed inside the outer tube 11 and the inner tube 12, and oil and gas are sealed inside the outer tube 11 and the inner tube 12.

[0014] In this example, a dust seal 16 is attached to the lower end of the outer tube 11 , and an oil seal 17 is attached to the lower part of the outer tube 11 at a position above the dust seal 16 . The oil seal 17 slides against the inner tube 12 and seals out oil and gas.

[0015] The dust seal 16 slides against the inner tube 12 and prevents external dust, muddy water, and mud from entering the gap between the outer tube 11 and the inner tube 12 , thereby protecting the oil seal 17 .

[0016] The dust seal 16 and the oil seal 17 are collectively referred to as a seal member 18. However, the seal member 18 may include a sealing part such as an O-ring, and therefore the seal member 18 is not limited to the dust seal 16 or the oil seal 17.

[0017] During travel, the outer tube 11 moves axially relative to the inner tube 12. The relative movement includes all of the following: the outer tube 11 moves axially relative to the inner tube 12; the inner tube 12 moves axially relative to the outer tube 11; and both the outer tube 11 and the inner tube 12 move axially.

[0018] The vehicle body is supported by the wheels that come into contact with the road surface via a vehicle suspension 10. While the vehicle is traveling, it can move up and down, as well as forward and backward and left and right. These movements are closely related to ride comfort and maneuverability. It is known that the ride comfort and maneuverability improve as the friction coefficient of the seal member 18 decreases, so there is a demand for the seal member 18 to have low friction.

[0019] In addition, the greater the tensile strength of the seal member 18, the greater the durability, and a moderate elongation value will maintain good reciprocating movement. Therefore, the tensile strength and elongation of the seal member 18 are important. To this end, the present inventors have made various attempts, which are listed below.

[0020] ○Measurement principle of friction coefficient: A stage that moves back and forth over a specified stroke is prepared, along with a weight with a metal ball attached to the bottom and a load cell that measures the horizontal force applied to the weight. The sample is fixed to the stage, a weight is placed on the sample via a metal ball, and a few drops of lubricant are placed between the sample and the metal ball. In this state, the stage is moved back and forth, and the horizontal force is measured with a load cell. The coefficient of kinetic friction is calculated based on the mass of the weight and the horizontal force.

[0021] ○Measurement conditions for friction coefficient: The conditions for measuring the friction coefficient are as follows: Stage travel distance (travel stroke): 2.5mm to the left and 2.5mm to the right of the center for a total of 5.0mm. ·Moving speed: 1mm / sec Load (mass of weight): 19.6N Number of round trips: 100

[0022] Tensile strength measurement method: The tensile strength of the sample is determined according to JIS K 6251 (vulcanized rubber and thermoplastic rubber - Determination of tensile properties).

[0023] ○Measurement method for elongation: The elongation of the sample was determined according to JIS K 6251 (vulcanized rubber and thermoplastic rubber - Determination of tensile properties).

[0024] ○ Sample preparation for Comparative Example 1: A sample was produced by blending 36.5% by mass of NBR (manufactured by JSR Corporation, product name N240S), 47.5% by mass of silica (manufactured by Tosoh Silica Corporation, product name Nipsil® ER-R), 1.8% by mass of carbon black (manufactured by Tokai Carbon Co., Ltd., product name Seast SO), and 14.2% by mass of other additives. The abbreviation for this sample is NBR100%. Hereinafter, the manufacturer name and product name will be omitted as they are the same. NBR is an abbreviation for nitrile butadiene rubber.

[0025] Examples 1, 2 and 3: It is known that porous carbon ceramic materials such as RH ceramics (porous carbon materials made by firing rice hulls) have sliding properties derived from carbon and reinforcing properties due to their cell structure. Therefore, the inventors decided to prepare samples of Examples 1, 2, and 3 by adding RHSC (Rice Hull Silica Carbon) to NBR.

[0026] ○RHSC particle size: The particle size distribution of the RHSC used in Examples 1, 2, and 3 was investigated. The results are shown in Figure 2. Figure 2 is a semi-logarithmic graph with a logarithmic scale on the horizontal axis and a linear scale on the vertical axis. As shown in Figure 2, RHSC has a particle size of 10 μm or less. More specifically, the median of the distribution is 3.0 μm, and the particle size range is 0.3 to 10 μm.

[0027] ○ Sample preparation for Example 1: A sample was produced by blending 36.3 mass% NBR, 47.2 mass% silica, 1.8 mass% carbon black, and 14.2 mass% other additives with 0.5 mass% porous carbon ceramic material (manufactured by Sanwa Yushi Co., Ltd., product name RHSC) with a particle size of 10 μm or less. The abbreviated name for this sample is NBR-RHSC0.5%-10 μm. Since the manufacturer and product name of the porous carbon ceramic material are the same hereafter, these will be omitted.

[0028] ○ Sample preparation for Example 2: A sample was produced by blending 35.8% by mass of NBR, 46.5% by mass of silica, 1.8% by mass of carbon black, and 13.9% by mass of other additives with 2.0% by mass of RHSC with a particle size of 10 μm or less. The abbreviated name for this sample is NBR-RHSC2.0%-10 μm.

[0029] Sample preparation for Example 3: A sample was produced by blending 35.4% by mass of NBR, 46.1% by mass of silica, 1.8% by mass of carbon black, and 13.8% by mass of other additives with 2.9% by mass of RHSC with a particle size of 10 μm or less. The abbreviated name for this sample is NBR-RHSC2.9%-10 μm.

[0030] ○ Sample preparation for Comparative Example 2: For comparison with Examples 1 and 2, a sample of Comparative Example 2 is prepared. A sample was produced by blending 20.1% by mass of NBR, 26.1% by mass of silica, 1.0% by mass of carbon black, and 7.8% by mass of other additives with 45.0% by mass of RHSC with a particle size of 10 μm or less. The abbreviation for this sample is NBR-RHSC45%-10 μm.

[0031] Elongation of Examples 1, 2, and 3 and Comparative Examples 1 and 2: The elongations of Comparative Example 1, Example 1, Example 2, Example 3, and Comparative Example 2 were measured according to the above-mentioned elongation measurement method. Then, to facilitate comparison, the elongation of Example 1 was calculated as the relative elongation using the formula {(elongation of Example 1) / (elongation of Comparative Example 1)=relative elongation of Example 1}. The same applies to Examples 2 and 3, and Comparative Example 2. The results are shown in Table 1.

[0032] [Table 1]

[0033] Table 1 is shown in graph form in Figures 3(a) and (b). 3(a) is a semi-logarithmic graph in which the horizontal axis is a logarithmic scale and the vertical axis is a linear scale. For convenience, Comparative Example 1 is plotted at the 0.1 position on the horizontal axis. From Example 3 to Comparative Example 2, the relative elongation decreases.

[0034] Figure 3(b) is an enlarged view of the main part of Figure 3(a), where both the horizontal and vertical axes are scaled uniformly. From Example 1 to Comparative Example 1, the relative elongation decreases. From Example 2 to Example 3, the relative elongation is maintained.

[0035] From the above, it was confirmed that good elongation is maintained if the RHSC content is in the range of 0.5 to 2.9 mass %.

[0036] Tensile strength of Example 2 and Comparative Example 1: The tensile strength of Comparative Example 1 and the tensile strength of Example 2 were measured according to the above-mentioned tensile strength measurement method. Then, to facilitate comparison, the tensile strength of Example 2 was calculated as the relative tensile strength according to the formula {(tensile strength of Example 2) / (tensile strength of Comparative Example 1)=relative tensile strength of Example 3}.

[0037] Dynamic friction coefficients of Example 2 and Comparative Example 1: The dynamic friction coefficient of Comparative Example 1 and the dynamic friction coefficient of Example 2 were measured based on the above-mentioned method for measuring the friction coefficient. The relative tensile strengths and the measured dynamic friction coefficients are shown in Table 2.

[0038] [Table 2]

[0039] The relative tensile strengths shown in Table 2 are graphed in Figure 4. 4, the tensile strength of Example 2, which contained 2% RHSC of 10 μm or less, was about 9% lower than that of Comparative Example 1, which was made of 100% NBR. However, this level of decrease is within the allowable range.

[0040] The dynamic friction coefficients shown in Table 2 are graphed in Figure 5. A small coefficient of friction is preferred for sealing members. The dynamic friction coefficient of Comparative Example 1 is 0.121, and the friction coefficient of Example 2 is 0.113. By calculating (0.121-0.113) / 0.121=0.066, Example 2 showed a 6.6% improvement over Comparative Example 1. From the above, it can be seen that in Example 2, the tensile strength was maintained while the friction performance was improved.

[0041] [Porous carbon ceramic material] The inventors of the present invention tried RB ceramics made by firing rice bran instead of RHSC, and found that it had elongation, tensile strength and friction properties similar to those of RHSC. In addition, when wood ceramics was used instead of RHSC, the same elongation, tensile strength and friction performance as RHSC were obtained. Wood ceramics is a porous carbon ceramic material obtained by carbonizing wood or a composite material of wood material and phenolic resin.

[0042] [Rubber composition] The inventors have tried replacing NBR with hydrogenated NBR, EPDM (ethylene-propylene-diene rubber), ACM (acrylic rubber), FKM (fluororubber), and VMQ (silicon rubber), and have found that they achieved elongation, tensile strength, and friction performance similar to that of NBR. Therefore, the rubber composition is not limited to NBR.

[0043] To summarize the above, the following can be said: First, the sealing member according to the present invention has a rubber composition containing porous carbon ceramics in the range of 0.5 to 2.9 mass %. That is, as explained in FIGS. 3(a) and (b), good elongation can be maintained within the range of 0.5 to 2.9 mass %.

[0044] The porous carbon ceramics are preferably RH ceramics made by firing rice husks or RB ceramics made by firing rice bran. RH ceramics provide improved friction performance as illustrated in Figure 5. The same is true for RB ceramics. In addition, the present invention allows for effective utilization of rice husks and rice bran, which have conventionally been incinerated or discarded.

[0045] The porous carbon ceramic preferably has a particle size of 10 μm or less. Porous carbon ceramics of 10 μm or less as shown in FIG. 2 can provide the desirable elongation shown in FIGS. 3(a) and 3(b).

[0046] The filling rate of the porous carbon ceramics is preferably 0.5 to 2.0 mass %. The filling rate of Example 2 is 2.0 mass %. According to Example 2, a suitable tensile strength is maintained as shown in FIG. 4, and improved friction performance is obtained as shown in FIG.

[0047] The seal member 18 of the present invention is also suitable for a vehicle suspension 10 such as that shown in Fig. 1. The vehicle suspension 10 of the present invention has a seal material 18 with a low coefficient of friction, resulting in smoother operation. In addition, the seal member 18 of the present invention has appropriate elongation and tensile strength, which can extend the life of the seal member 18 in the vehicle suspension 10.

[0048] That is, the present invention can be applied to both the dust seal 16 and the oil seal 17 shown in Fig. 1. Alternatively, the present invention can be applied to either the dust seal 16 or the oil seal 17. A case where the present invention is applied to one of the dust seal 16 and the oil seal 17 will be further considered.

[0049] The seal member 18 according to the present invention has a good tensile strength despite containing porous carbon ceramics, since the grain size of the porous carbon ceramics is 10 μm or less. The dust seal 16 is located inside the outer tube 11, and the oil seal 17 is located outside the outer tube 11. When subjected to attack by sand or pebbles from the outside, the dust seal 16 is required to have greater mechanical strength than the oil seal 17. Therefore, when the present invention is applied to either the dust seal 16 or the oil seal 17, it is recommended to apply it to the dust seal 16.

[0050] In the embodiment, the vehicle suspension is a front suspension of a motorcycle, but it may also be a rear suspension of a motorcycle. Furthermore, the vehicle may be a three-wheeled vehicle or a four-wheeled vehicle in addition to a motorcycle. Therefore, the vehicle suspension is not limited to a front suspension of a motorcycle. [Industrial Applicability]

[0051] The seal member of the present invention is suitable for use in vehicle suspensions. [Explanation of symbols]

[0052] 10...vehicle suspension, 16...dust seal, 17...oil seal, 18...sealing member

Claims

1. A sealing member having a rubber composition containing porous carbon ceramics in the range of 0.5 to 2.9 mass %.

2. The seal member according to claim 1, The sealing member, wherein the porous carbon ceramic is RH ceramics obtained by firing rice husks or RB ceramics obtained by firing rice bran.

3. The seal member according to claim 2, The porous carbon ceramics have a particle size of 10 μm or less.

4. The seal member according to claim 2, A sealing member, wherein the filling rate of the porous carbon ceramic is 0.5 to 2.0 mass %.

5. The seal member according to claim 1, A sealing member used in vehicle suspensions.

6. A vehicle suspension comprising the seal member according to claim 5.

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