JP4176401B2 - Gasket material - Google Patents

Description

【００２９】
図５は、上記実施形態のジョイントシート１において、原料の基本組成を、アラミド繊維が２０重量％、ＮＢＲが２３重量％、硫酸バリウムが２０重量％、残部が他の無機充填材であるものとし、その硫酸バリウムの粒子径を種々異ならせて、上記と同じ条件で座屈疲労試験と限界シール圧力測定試験とを行って座屈疲労特性に対する硫酸バリウムの粒形の寄与度を調べるとともに限界シール圧力を測定した結果を示すものである。この図から明らかなように、配合する硫酸バリウムの粒子径が４μｍを超えるとジョイントシート１の座屈疲労面圧P1が特に低下する傾向があり、また硫酸バリウムの粒子径が大きくなるほど限界シール圧力P2も低下する傾向があるので、硫酸バリウムは３μｍ以下の微細な粉末であることが好ましい。なお、先に述べた図７，８に示す結果も、上記と同じ条件で座屈疲労試験と限界シール圧力測定試験とを行って得たものである。
【００３０】
図６は、上記実施形態のジョイントシート１において、原料の基本組成を、アラミド繊維が２０重量％、ＮＢＲが２３重量％、硫酸バリウムが７重量％、残部が他の無機充填材であるものとし、そのアラミド繊維の比表面積を種々異ならせて、上記と同じ条件で引張試験と座屈疲労試験とを行って、引張強度および座屈疲労特性に対するアラミド繊維のフィブリル度の寄与度を調べた結果を示すものである。この図から明らかなように、配合するアラミド繊維のフィブリル度の指標である比表面積が６ｍ² ／ｇ未満になるとジョイントシート１の引張強度の低下が起こり、これと同期して座屈疲労特性が低下する傾向があり、アラミド繊維の比表面積は６ｍ² ／ｇ以上であることが好ましい。
【００３１】
以上、図示例に基づき説明したが、この発明は上述の例に限定されるものでなく、例えばジョイントシートを、上記表層１ｂに対応するいわゆる皿材からなる裏層および表層と、上記主層１ａに対応するいわゆる中材からなる中間主層との三層からなる多層構造としても良く、また上記主層１ａに対応するいわゆる中材のみからなる単層構造としても良い。そしてこの発明のガスケット素材は、変速機のハウジングとカバーとの間に挿入されるガスケット以外のエンジン周辺部のガスケットにも用い得ることはもちろんである。
【図面の簡単な説明】
【図１】 この発明のガスケット素材の一実施形態を示す断面図である。
【図２】 上記実施形態のガスケット素材としてのジョイントシートと、既存流通材料のジョイントシートとの引張強度を対比して示す説明図である。
【図３】 上記実施形態のガスケット素材としてのジョイントシートと、既存流通材料のジョイントシートとの座屈疲労面圧を対比して示す説明図である。
【図４】 上記実施形態のガスケット素材としてのジョイントシートと、既存流通材料のジョイントシートとの限界シール圧力を対比して示す説明図である。
【図５】 上記実施形態のジョイントシートについての配合する硫酸バリウムの粒子径と座屈疲労面圧および限界シール圧力との関係を示す説明図である。
【図６】 上記実施形態のジョイントシートについての配合するアラミド繊維の比表面積と引張強度および座屈疲労面圧との関係を示す説明図である。
【図７】 従来のジョイントシートについての引張強度と座屈疲労面圧との関係を示す説明図である。
【図８】 従来のジョイントシートについての引張強度と限界シール圧力との関係を示す説明図である。
【符号の説明】
１ ジョイントシート
１ａ 主層
１ｂ 表層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a material for a gasket used in an engine, a transmission, or the like mounted on a vehicle or the like. It is related with the gasket raw material which consists of a joint sheet formed in this way.
[0002]
[Prior art]
In the past, asbestos joint sheets made of asbestos as reinforcement fibers made of nitrile rubber and phenol resin were laminated as a material for gaskets around the engine mounted on vehicles and the like. Due to asbestos regulations, the applicants of the present application, for example, described in the paper “Development of non-asbestos gaskets” published by the present applicants in a preprint of the academic lecture issued by the Japan Society for Automotive Engineers in May 1992. In addition, we are considering the practical application of joint sheets that use other reinforcing fibers without using asbestos.
[0003]
By the way, for example, a structure in which the temperature change becomes large due to repeated operation of the engine and stopping, such as a gasket insertion portion between a transmission housing combined with the engine and a cover fixed with bolts thereto. When a gasket is used, relative displacement (fretting) occurs repeatedly between the joint surfaces of the housing and the cover and the gasket due to repeated temperature changes. In addition, due to the recent demand for weight reduction, since the rigidity of structures such as housings and covers has been reduced, fretting also occurs due to external forces applied to the covers and the like.
[0004]
On the other hand, including the case where the reinforcing fiber is asbestos, the conventional joint sheet has a low tensile strength. For this reason, when a gasket made of a conventional joint sheet is used for a transmission around the engine, the gasket is displaced from its original position due to the fretting and leakage of the sealing medium occurs due to a decrease in surface pressure.
[0005]
[Problems to be solved by the invention]
Thus, various methods for increasing the strength of the joint sheet have been conventionally studied as described below, but none of these methods are sufficiently appropriate. That is, or attempt to be allowed to strength improvement increased composition amount of the reinforcing fibers, to increase the fiber length of the reinforcing fibers are or reduce sensitivity by increasing the molar Horoji effects, gaskets in these methods There is a problem that the raw material cost is increased and the sealing performance is deteriorated due to the deterioration of the smoothness of the gasket surface.
[0006]
Also, by increasing the roll pressure at the time of joint sheet lamination, the gasket density is increased to improve strength, and the hot roll temperature at the time of joint sheet lamination is increased to raise the vulcanization temperature of the compounded rubber. However, in these methods, as shown in FIG. 7, if the strength of the joint sheet is increased to a certain level, the hardness of the joint sheet becomes too high. The durability of the gasket against repeated compressive stress is reduced, and in the worst case, the gasket has a buckling fatigue, that is, a compression set accompanied by a transverse flow due to compressive failure, resulting in a decrease in sealing performance as shown in FIG. is there.
[0007]
Furthermore, the joint sheet can be hardened by reducing the amount of rubber compounded in the composition of the joint sheet to improve the strength, or the joint sheet can be made by increasing the acrylonitrile ratio of the NBR rubber to 40% or more in the compounded rubber of the joint sheet. However, these methods reduce the flexibility of the joint sheet, and when the stress in the thrust direction is applied due to fretting with the surface pressure applied, the gasket will sag greatly. That is, there is a problem that a compression set in the direction of decreasing the plate thickness is generated, resulting in a decrease in sealing performance.
[0008]
[Means for solving the problems and their functions and effects]
An object of the present invention is to provide a gasket material that advantageously solves the above problems. The gasket material of the present invention is a pressure laminate while kneading a raw material in which rubber, a reinforcing fiber, and a filler are mixed. In addition, in the gasket material comprising the joint sheet formed by vulcanization, the basic composition of the raw material is 20% by weight or more of aramid fibers as the reinforcing fiber, and 23% by weight or more and 30% by weight or less of the rubber. , And 7 wt% or more and 30 wt% or less of barium sulfate as the filler, and the remaining inorganic filler as the other filler.
[0009]
According to the gasket material of the present invention, 20% by weight or more of aramid fibers and 7% by weight or more and 30% by weight or less of barium sulfate increase the strength while maintaining high flexibility of the joint sheet. Even if fretting occurs in a structure such as a housing or a cover, it is possible to prevent leakage of the sealing medium due to a decrease in surface pressure due to the gasket being displaced from its original position.
[0010]
In addition, since the strength is not improved by increasing the amount of the reinforcing fiber composition or the fiber length of the reinforcing fiber, the raw material cost of the gasket can be kept low, and the gasket surface can be made smooth and sealable. The strength of the joint sheet is not improved by increasing the roll pressure and the temperature of the hot roll during the joint sheet lamination, so the joint sheet can be kept low in hardness and subjected to repeated compressive stress. It is possible to ensure the durability of the gasket and prevent deterioration of the sealing performance due to gasket buckling fatigue.
[0011]
Furthermore, the strength of the joint sheet is not improved by reducing the amount of rubber compounded in the composition of the joint sheet or by increasing the acrylonitrile ratio of the NBR rubber. With respect to the stress in the thrust direction due to fretting, it is possible to prevent deterioration of the sealing performance due to a large gasket sag.
[0012]
Furthermore, gasket material of this invention, the aramid fiber is characterized in that the specific surface area is of 13m ² / g or less at 6 m ² / g or more.
This is because if the specific surface area indicating the degree of fibrillation of the aramid fiber is 6 m ² / g or more and 13 m ² / g or less , the tensile strength and the buckling fatigue surface pressure of the joint sheet and the gasket formed therefrom can be sufficiently increased.
[0013]
Additionally, gasket material of this invention, the barium sulfate has an average particle size is characterized in that this is the 3μm or less 0.5μm or more.
This is because when a barium sulfate powder having a particle diameter of 0.5 μm or more and 3 μm or less is used, the buckling fatigue surface pressure of the joint sheet and thus the gasket formed therefrom is particularly high.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of the gasket material according to the present invention. In FIG. 1, reference numeral 1 denotes a two-layered structure including a main layer 1a made of a so-called medium material and a surface layer 1b made of a so-called dish material. The joint sheet | seat as a gasket raw material of the said embodiment made into the multilayer structure which consists of is shown.
[0015]
The joint sheet 1 of this embodiment includes, for example, rubber such as NBR, reinforced fibers made of fibrillated (fine fiber) aramid fibers, barium sulfate as a filler, and other inorganic filler such as clay. Are fed onto a hot roll of a calender roll having a pair of rolls of a hot roll and a cold roll, and laminated on the hot roll by pressing while kneading with those rolls, and It is formed by vulcanizing and curing with the heat of the hot roll and then peeling off from the hot roll. At that time, by changing the composition of the reinforcing fiber and the filler, as shown in FIG. 1, two layers of the main layer 1a and the surface layer 1b are formed (for example, the previous paper “Development of a non-asbestos gasket”). "reference).
[0016]
By the way, in the joint sheet 1 of this embodiment, the basic composition of the raw materials is 20% by weight or more of aramid fiber as a reinforcing fiber and 23% by weight or more and 30% by weight or less of NBR (nitrile butadiene) as rubber. Rubber), 7% by weight or more and 30% by weight or less of barium sulfate as a filler, and the remaining other inorganic filler.
[0017]
Here, as the aramid fiber, for example, an aromatic polyamide fiber (pulp type) having a specific surface area of 6 m ² / g or more, which is an index of the degree of fibrillation, is used. This is because when the specific surface area of the aramid fiber is 6 m ² / g or more, as will be described later, the tensile strength and the buckling fatigue surface pressure of the joint sheet and the gasket formed therefrom can be sufficiently increased.
[0018]
In addition, a powder having an average particle size of 3 μm or less is used for the barium sulfate. This is because when a barium sulfate powder having a particle diameter of 3 μm or less is used, the buckling fatigue surface pressure of the joint sheet and thus the gasket formed therefrom can be particularly increased as will be described later.
[0019]
According to the joint sheet 1 of this embodiment, 20% by weight or more of aramid fibers and 7% by weight or more and 30% by weight or less of barium sulfate increase strength while maintaining high flexibility of the joint sheet. Therefore, even if fretting occurs in a structure such as a housing or a cover, it is possible to prevent the gasket from being displaced from its original position and causing crack breakage.
[0020]
In addition, since the strength is not improved by increasing the amount of the reinforcing fiber composition or the fiber length of the reinforcing fiber, the raw material cost of the gasket can be kept low, and the gasket surface can be made smooth and sealable. The strength of the joint sheet is not improved by increasing the roll pressure and the temperature of the hot roll during the joint sheet lamination, so the joint sheet can be kept low in hardness and subjected to repeated compressive stress. It is possible to ensure the durability of the gasket and prevent deterioration of the sealing performance due to gasket buckling fatigue.
[0021]
Furthermore, the strength of the joint sheet is not improved by reducing the amount of rubber compounded in the composition of the joint sheet or by increasing the acrylonitrile ratio of the NBR rubber. With respect to the stress in the thrust direction due to fretting, it is possible to prevent deterioration of the sealing performance due to a large gasket sag.
[0022]
Therefore, according to the joint seat 1 of this embodiment, the rigidity of the structure such as the transmission is low, and a high bolt fastening force is applied to the gasket insertion portion between the housing and the cover of the structure, for example. In such a case, even when a force that causes deformation of the cover, for example, is applied to the structure, excellent sealing durability can be exhibited. That is, when the rigidity of the structure is low, the surface pressure generated in the gasket insertion portion is high immediately below and near the fastening bolt, but is low between the spans of the fastening bolt. For this reason, the gasket is required to have a high buckling resistance and a good flexibility, but according to the joint sheet 1 of this embodiment, they can be provided.
[0023]
The characteristics of the joint sheet 1 of this embodiment, on the contrary, are the degrees of freedom such as the pitch and size of the fastening bolts, the cover thickness, etc., when designing the structure to be sealed with the joint sheet 1 of this embodiment. Can be improved, and the weight of the structure can be reduced.
[0024]
FIG. 2 shows the result of a tensile test performed on the joint sheet 1 of the above embodiment and the three types of joint sheets of Comparative Examples 1 to 3 that are existing distribution materials under the conditions defined in JIS K 6251. The tensile strength is shown in comparison. As is clear from this figure, the tensile strength of the joint sheet 1 of the above embodiment (specifically, the approximate average value of Examples 1 to 7 described later) is greater than the tensile strength of the joint sheet of the existing distribution material. It is quite expensive.
[0025]
FIG. 3 shows a hydraulic press on a ring-shaped sample sandwiched between two plates of the joint sheet 1 of the above embodiment and the three types of joint sheets of Comparative Examples 1 to 3 which are existing distribution materials. In the state where a predetermined surface pressure is applied, one of the two plates is reciprocally slid by an actuator with a movement width of 300 μm and a frequency of 1 Hz, and it is examined whether or not fuzz due to reinforcing fibers occurs in the sample in 3000 cycles. The comparison shows the buckling fatigue surface pressure as a result of conducting a buckling fatigue test under the condition that the surface pressure at which fuzzing occurs is the buckling fatigue surface pressure. As is clear from this figure, the buckling fatigue surface pressure of the joint sheet 1 of the above embodiment (specifically, the approximate average value of Examples 1 to 7 described later) is the seat of the joint sheet of the existing distribution material. It is much higher than the bending fatigue surface pressure.
[0026]
Furthermore, FIG. 4 shows a surface pressure of 10 MPa on the sample in which the buckling fatigue occurred with respect to the joint sheet 1 of the above embodiment and the three types of joint sheets of Comparative Examples 1 to 3 which are existing distribution materials. In addition to supplying nitrogen gas to the inside of the sample and adding soap liquid to the outer periphery of the sample to check for leaks of nitrogen gas, the results of the limit seal pressure measurement test are measured using the gas pressure at which the leak occurs as the limit seal pressure. It is shown. As is clear from this figure, the limit seal pressure of the joint sheet 1 of the above embodiment (specifically, the approximate average value of Examples 1 to 7 described later) is the limit seal pressure of the joint sheet of the existing distribution material. It is roughly equivalent to the highest one of these.
[0027]
【Example】
Table 1 below shows a joint sheet 1 having a plate thickness of 0.5 mm in each of Examples 1 to 7 in which the composition was varied in the above embodiment, and aramid fibers and barium sulfate according to the above embodiment. In any of Comparative Examples 1 to 6 in which any compounding with rubber deviates from the above embodiment, a joint sheet having a plate thickness of 0.5 mm was manufactured, and each of these joint sheets was subjected to a tensile test under the above-described conditions. The results of the buckling fatigue test and the limit seal pressure measurement test are shown. From these results, in Comparative Examples 1 to 6, any of the tensile strength, the buckling fatigue surface pressure, and the limit seal pressure was low. but none of examples 1 to 7, to ensure 80MPa or more high buckling fatigue surface pressure and having a high tensile strength of at least 25 MPa, yet 2.0 kgf / cm ² or more critical sealing pressure Has, it is found that gasket material having good properties.
[0028]
[Table 1]

[0029]
FIG. 5 shows that in the joint sheet 1 of the above embodiment, the basic composition of the raw material is 20% by weight of aramid fiber, 23% by weight of NBR, 20% by weight of barium sulfate, and the balance is another inorganic filler. By varying the particle size of the barium sulfate, the buckling fatigue test and the limit seal pressure measurement test were conducted under the same conditions as described above to examine the contribution of the barium sulfate particle shape to the buckling fatigue characteristics and limit sealing. The result of measuring the pressure is shown. As is clear from this figure, when the particle diameter of the barium sulfate compounded exceeds 4 μm, the buckling fatigue surface pressure P1 of the joint sheet 1 tends to decrease particularly, and the limit seal pressure increases as the particle diameter of the barium sulfate increases. Since P2 also tends to decrease, barium sulfate is preferably a fine powder of 3 μm or less. The results shown in FIGS. 7 and 8 are also obtained by performing a buckling fatigue test and a limit seal pressure measurement test under the same conditions as described above.
[0030]
FIG. 6 shows that in the joint sheet 1 of the above embodiment, the basic composition of the raw material is 20% by weight of aramid fibers, 23% by weight of NBR, 7% by weight of barium sulfate, and the balance is another inorganic filler. The results of examining the contribution of the fibrillation degree of the aramid fiber to the tensile strength and the buckling fatigue property by performing the tensile test and the buckling fatigue test under the same conditions as described above, with different specific surface areas of the aramid fiber Is shown. As is clear from this figure, when the specific surface area, which is an index of the fibrillation degree of the aramid fiber to be blended, is less than 6 m ² / g, the tensile strength of the joint sheet 1 is lowered, and the buckling fatigue characteristics are synchronized with this. The specific surface area of the aramid fiber is preferably 6 m ² / g or more.
[0031]
Although the present invention has been described based on the illustrated example, the present invention is not limited to the above-described example. For example, the joint sheet includes a back layer and a surface layer made of a so-called dish material corresponding to the surface layer 1b, and the main layer 1a. It is also possible to have a multilayer structure consisting of three layers with an intermediate main layer made of so-called intermediate material corresponding to the above, or a single layer structure consisting of only so-called intermediate material corresponding to the main layer 1a. Of course, the gasket material of the present invention can also be used for a gasket around the engine other than the gasket inserted between the housing and the cover of the transmission.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a gasket material of the present invention.
FIG. 2 is an explanatory view showing a comparison of tensile strength between a joint sheet as a gasket material of the embodiment and a joint sheet of an existing distribution material.
FIG. 3 is an explanatory view showing a comparison of buckling fatigue surface pressure between a joint sheet as a gasket material of the embodiment and a joint sheet of an existing distribution material.
FIG. 4 is an explanatory view showing a comparison of limit seal pressures of a joint sheet as a gasket material of the embodiment and a joint sheet of an existing distribution material.
FIG. 5 is an explanatory diagram showing the relationship between the particle diameter of barium sulfate to be blended, the buckling fatigue surface pressure, and the limit seal pressure for the joint sheet of the embodiment.
FIG. 6 is an explanatory diagram showing the relationship between the specific surface area of aramid fibers to be blended and the tensile strength and buckling fatigue surface pressure of the joint sheet of the embodiment.
FIG. 7 is an explanatory diagram showing the relationship between tensile strength and buckling fatigue surface pressure for a conventional joint sheet.
FIG. 8 is an explanatory diagram showing the relationship between tensile strength and limit seal pressure for a conventional joint sheet.
[Explanation of symbols]
1 Joint sheet 1a Main layer 1b Surface layer

Claims (1)

In the gasket material consisting of the joint sheet formed by vulcanization and pressure lamination while kneading the raw material mixed with rubber, reinforcing fiber and filler,
The basic composition of the raw material is
20% by weight or more of aramid fiber as the reinforcing fiber;
23% by weight or more and 30% by weight or less of the rubber,
7 wt% or more and 30 wt% or less of barium sulfate as the filler,
The remaining inorganic filler as the other filler,
Tona is,
The aramid fiber has a specific surface area of 6 m ² / g or more and 13 m ² / g or less,
The gasket material, wherein the barium sulfate has an average particle size of 0.5 μm or more and 3 μm or less .

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