JP2004035788A - Gasket raw material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a leak of a sealing medium by the torque down of a bolt, etc., caused by a stress relaxation in the case of having a large surface pressure difference in a heated environment by reducing the compressed permanent distortion of a gasket using a joint sheet as a raw material on heating. <P>SOLUTION: This gasket raw material consisting of the joint sheet 1 formed by compression-laminating and vulcanizing a raw material obtained by mixing/kneading a rubber, reinforcing fiber and filler is characterized by having a single layer structure of the joint sheet as its composition, and a base composition consisting of ≥15 wt. % aramid fiber as the reinforcing fiber, ≥10 wt. % and ≤30 wt. % NBR as the rubber, ≥2 wt. % and ≤26 wt. % phenolic resin as the filler and the rest of an inorganic filler. <P>COPYRIGHT: (C)2004,JPO

Description

【００１８】
これら表１および図３から、フェノール樹脂の添加量が２重量％以上で２６重量％以下の場合に上記原料が適度な付着強度を持ち、２重量％未満では付着強度が大きすぎて、積層中は原料がコールドロールに取られ易く、また積層後はホットロールからの積層シートの剥ぎ取りが困難になり、２６重量％を超えると付着強度が小さすぎて、ホットロール上での原料の積層が困難になるということがわかる。
【００１９】
なお、上記実施例１〜６のジョイントシート１からなるガスケットについて、ＪＩＳ　Ｋ　６２５１に規定された条件で引っ張り試験を行うとともに、板状の二枚の治具で挟んだリング状試料に油圧プレスで所定面圧を加えた状態でその二枚の治具の一方をアクチュエータにより移動幅３００μｍ、周波数１Ｈｚで往復摺動させて３０００サイクルで試料に繊維による毛羽立ちが発生するか否かを調べ、試料に毛羽立ちが発生する面圧を座屈疲労面圧とするという条件で座屈疲労試験を行い、加えてその座屈疲労が生じた試料に１０ＭＰａの面圧を加えた状態で試料内部に上記治具から窒素ガスを供給するとともに試料外周に石鹸液をつけて窒素ガスの漏れを調べ、漏れが発生するガス圧を限界シール圧力として測定した結果、何れも、２５ＭＰａ以上の高い引張強度を有するとともに、８０ＭＰａ以上の座屈疲労面圧を確保し、しかも２．０ｋｇｆ／ｃｍ^２　以上の限界シール圧力を有していた。
【００２０】
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、例えばフェノール樹脂はレゾールタイプ以外のものでも良い。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としてのジョイントシートを示す断面図である。
【図２】上記実施形態のジョイントシートから形成したガスケットと既存のジョイントシートから形成したガスケットとについての冷熱サイクル数とボルト軸力保持率との関係を示す説明図である。
【図３】上記実施形態のジョイントシートから形成したガスケットについてのフェノール樹脂の添加量とホットロールへの原料の付着強度との関係を示す説明図である。
【図４】従来のジョイントシートを示す断面図である。
【符号の説明】
１　ジョイントシート
１ａ　表層
１ｂ　裏層
１ｃ　中間層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a material for a gasket used for an engine or a transmission mounted on a vehicle or the like, and in particular, a material obtained by kneading a rubber, a reinforcing fiber, and a filler is press-laminated and vulcanized by a calender roll. The present invention relates to a gasket material comprising a formed joint sheet.
[0002]
[Prior art]
Conventionally, as a material of a gasket for the periphery of an engine mounted on a vehicle or the like, a raw material obtained by kneading asbestos as a reinforcing fiber, a nitrile rubber, and a phenol resin, and a pair of rolls of a hot roll and a cold roll are used. A so-called asbestos joint sheet formed by laminating and curing on a hot roll of a calender roll provided therein has been used. As described in the paper "Development of non-asbestos gasket" published by the present applicant in the preprint of the academic lecture issued by the Society of Automotive Engineers of Japan, the practical use of joint sheets using other reinforcing fibers without using asbestos We are considering conversion.
[0003]
By the way, in general, a joint sheet is formed by rolling a raw material adhering on a hot roll of a calender roll while kneading the hot roll and a cold roll to form a laminated sheet on the hot roll, and then laminating the laminated sheet on the cooled hot roll. Is formed by stripping off. For this reason, it is necessary that the raw material of the joint sheet adheres to the hot roll but hardly adheres to the cold roll, and needs to be separated from the cold hot roll when peeling off the laminated sheet.
[0004]
Therefore, conventionally, as shown in FIG. 6, a joint layer 1 is formed by disposing a surface layer 1a made of a so-called dish material that adheres to a hot roll, a back layer 1b made of a so-called finishing material that is less likely to adhere to a cold roll, and It has a three-layer structure with an intermediate layer 1c made of a so-called middle material having sufficient strength, and natural rubber is usually used for the rubber of the dish material, unlike the middle material. It has the property that the compression set in the heat receiving environment is large.
[0005]
On the other hand, for example, a seal of a structure constituted by fastening with a fastener such as a bolt, such as a gasket insertion portion between a housing of a transmission combined with an engine and a cover fixed thereto with a plurality of bolts. When a gasket is used for the part, for example, the surface pressure applied to the gasket is high at the part immediately below the bolt, but the surface pressure applied to the gasket is low at the corner part offset between the straight lines connecting the bolts and at the part between the bolt spans It is well known that a surface pressure difference occurs, and such a surface pressure difference tends to increase with the recent reduction in rigidity for weight reduction of a structure. In addition, the reduction in rigidity of the structure also causes a change in the seal gap due to a temperature change or the like, which further increases the surface pressure difference.
[0006]
[Problems to be solved by the invention]
For this reason, when the gasket formed from the above-mentioned conventional joint sheet 1 is used for a sealing portion of a structure constituted by fastening with fasteners such as bolts, the tightening force of the bolts and the like is reduced on the premise of ensuring the sealing performance in the low surface pressure portion. Therefore, a high surface pressure is necessarily applied to the gasket immediately below the bolts and the like, and the compression set of the surface layer 1a using the natural rubber is promoted by the high surface pressure in a heat receiving environment such as an engine peripheral portion. As a result, stress relaxation is increased, and the torque of the bolt is reduced, which may cause leakage of a seal medium such as lubricating oil or hydraulic oil.
[0007]
[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, and a gasket material of the present invention is obtained by pressing a raw material obtained by kneading rubber, reinforcing fibers, and a filler with a calender roll. In a gasket material comprising a joint sheet formed by lamination and vulcanization, the joint sheet has a composition of a single-layer structure, and the basic composition of the raw material is aramid fiber of 15% by weight or more as the reinforcing fiber, It is characterized by comprising NBR of 10% by weight or more and 30% by weight or less as the rubber, phenol resin of 2% by weight or more and 26% by weight or less as the filler and the remaining inorganic filler. It is.
[0008]
According to such a gasket material of the present invention, the joint sheet constituting the gasket material is different from the middle material in composition, and has a single layer having no surface layer of a plate material using natural rubber which is a compression set element when hot. Due to the structure, even when there is a large surface pressure difference in a heat receiving environment such as an engine peripheral portion, it is possible to prevent leakage of a seal medium such as lubricating oil or hydraulic oil due to torque reduction of a bolt due to stress relaxation. . Moreover, the phenolic resin of 2% by weight or more and 26% by weight or less as a filler material has an appropriate adhesive force to a hot hot roll in operation and an appropriate separation from a cold cold roll or a cold hot roll. Therefore, the formation of the joint sheet with the calender roll can be performed favorably.
[0009]
In the gasket material according to the present invention, the phenol resin is preferably a resol type. This is because the dispersibility of the phenol resin in the raw material is good.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Here, FIG. 1 is a cross-sectional view showing one embodiment of the gasket material of the present invention, and reference numeral 1 in the drawing indicates a joint sheet as a gasket material of the above embodiment. The joint sheet 1 of this embodiment has a single-layer structure in composition.
[0011]
The joint sheet 1 of this embodiment is obtained by mixing a raw material obtained by mixing NBR (nitrile butadiene rubber) as a rubber, aramid fiber as a reinforcing fiber, and phenol resin as a filler with a high-temperature hot roll and a low-temperature hot roll. The roll is supplied onto a hot roll of a calender roll comprising a pair of cold rolls, and is kneaded with these rolls and pressed to be laminated on the hot roll, and further heated by the heat of the high-temperature hot roll. After vulcanizing and curing to form a laminated sheet, the laminated sheet is formed by peeling off the laminated sheet from a hot roll. For details, see, for example, the above-mentioned paper “Development of Non-Asbestos Gasket”.
[0012]
Here, in order to give the raw material an appropriate adhesive force to the hot roll, in this embodiment, the basic composition of the raw material is 15 wt% or more of aramid fiber and 30 wt% or less of NBR being 10 wt% or more. The phenol resin is 2% by weight or more and 26% by weight or less, and the balance is an inorganic filler. The phenol resin is a resol-type phenol resin (for example, PR-217, a product name of Sumitomo Bakelite Co., Ltd., solid content 100% by weight).
[0013]
According to the joint sheet 1 of this embodiment, the joint sheet 1 has a single-layer structure without a surface layer of a plate material using natural rubber, which is different from the middle material in composition, and is a compression set element at the time of hot working. Therefore, even when there is a large surface pressure difference in a heat receiving environment such as a peripheral portion of the engine, it is possible to prevent leakage of a seal medium such as lubricating oil or hydraulic oil due to torque reduction of a bolt due to stress relaxation. Moreover, the phenolic resin of 2% by weight or more and 26% by weight or less as a filler material has an appropriate adhesive force to a hot hot roll in operation and an appropriate separation from a cold cold roll or a cold hot roll. Therefore, the formation of the joint sheet with the calender roll can be performed favorably.
[0014]
In addition, according to the joint sheet 1 of this embodiment, since the phenol resin used as the raw material is of the resol type, the phenol resin in the raw material has a good dispersibility, so that the above-described effects can be exhibited evenly. Can be.
[0015]
FIG. 2 shows a gasket (shown by a curve G1 in the figure) formed from the joint sheet 1 of the above embodiment and a gasket (shown by a curve G2 in the figure) formed from the existing three-layer structure joint sheet 1, respectively. Tighten with one bolt while sandwiching between two metal flanges, and perform a thermal cycle deterioration test under the conditions that the metal flange has a fastening surface pressure of 150 MPa, and repeated heating and cooling between 150 ° C and 20 ° C. The results of testing the retention of the axial force are shown. From this figure, it can be seen that the gasket formed from the joint sheet 1 of the above embodiment has a high retention of the bolt axial force and a small stress relaxation due to the compression set. I understand.
[0016]
【Example】
Table 1 below shows the joint sheets of Examples 1 to 6 in which the aramid fiber, the phenolic resin, and the NBR as the rubber were variously mixed in the joint sheet 1 of the above embodiment, and the joint sheet of the above embodiment. Similar to Sheet 1, but with the joint sheets of Comparative Examples 1, 2, and 3 out of the range of the above-described embodiment in which the phenolic resin was blended at 0%, 35%, and 40% by weight, respectively, with a surface pressure of 100 MPa and a temperature. FIG. 3 shows the results of testing the adhesion of a raw material during the production of a joint sheet to a high-temperature hot roll under the conditions of 100 ° C. and time: 60 minutes. FIG. 3 shows the relationship between the adhesion strength and the amount of phenol resin added. Is shown.
[0017]
[Table 1]

[0018]
From Table 1 and FIG. 3, it can be seen that when the added amount of the phenolic resin is 2% by weight or more and 26% by weight or less, the raw material has an appropriate adhesive strength, and when the added amount is less than 2% by weight, the adhesive strength is too large. The raw material is easily taken off by a cold roll, and after lamination, it is difficult to peel off the laminated sheet from the hot roll. If it exceeds 26% by weight, the adhesive strength is too small, and the lamination of the raw material on the hot roll becomes difficult. It turns out that it becomes difficult.
[0019]
The gasket made of the joint sheet 1 of Examples 1 to 6 above was subjected to a tensile test under the conditions specified in JIS K6251 and a hydraulic press was applied to a ring-shaped sample sandwiched between two plate-shaped jigs. With a predetermined surface pressure applied, one of the two jigs is reciprocally slid with an actuator at a moving width of 300 μm and a frequency of 1 Hz, and it is examined whether or not fuzzing due to fibers occurs in the sample in 3000 cycles. A buckling fatigue test is performed under the condition that the surface pressure at which fluffing occurs is defined as the buckling fatigue surface pressure, and the jig is placed inside the sample in a state where a surface pressure of 10 MPa is applied to the buckling fatigue generated sample. A nitrogen gas was supplied from the reactor and a soap solution was applied to the outer periphery of the sample to check for a leak of the nitrogen gas. The gas pressure at which the leak occurred was measured as the limit seal pressure. a, a buckling fatigue surface pressure of 80 MPa or more, and a critical sealing pressure of 2.0 kgf / cm ² or more.
[0020]
As described above, the present invention has been described based on the illustrated examples. However, the present invention is not limited to the above-described examples. For example, the phenol resin may be other than the resol type. The gasket material of the present invention can of course 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 sectional view showing a joint sheet as one embodiment of a gasket material of the present invention.
FIG. 2 is an explanatory diagram showing the relationship between the number of cooling / heating cycles and the bolt axial force retention for a gasket formed from the joint sheet of the embodiment and a gasket formed from an existing joint sheet.
FIG. 3 is an explanatory diagram showing the relationship between the addition amount of a phenol resin and the strength of adhesion of a raw material to a hot roll in a gasket formed from the joint sheet of the embodiment.
FIG. 4 is a sectional view showing a conventional joint sheet.
[Explanation of symbols]
1 Joint sheet 1a Surface layer 1b Back layer 1c Intermediate layer

Claims (2)

In a gasket material consisting of a joint sheet formed by kneading a raw material obtained by kneading a rubber, a reinforcing fiber and a filler with a calender roll under pressure and vulcanizing,
The joint sheet has a single-layer structure in composition,
The basic composition of the raw material is
Aramid fiber of 15% by weight or more as the reinforcing fiber,
NBR of not less than 10% by weight and not more than 30% by weight as the rubber;
2% by weight or more and 26% by weight or less of the phenol resin and the remaining inorganic filler as the filler,
A gasket material characterized by comprising: The gasket material according to claim 1, wherein the phenol resin is a resol type.

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