JPH0544848A - Infiltration type sintered metal gasket and manufacture thereof - Google Patents

Abstract

PURPOSE:To uniformize the surface pressure on the peripheral edge portion of a cylinder bore in a seal surface by forming a gasket element in such a manner that the thickness of at least one side surface thereof is gradually increased from the peripheral edge portion thereto toward the central area of a designated thickness, and the thickness of the main bore peripheral edge portion is uniform. CONSTITUTION:An infiltration type sintered metal gasket comprises a thin plate like gasket element 2 made of sintered metal mainly composed of iron, and iron-base alloy or nickel-base alloy and a grommet 5 installed in a main bore 3 formed on the gasket element 2, wherein low-melting point metal is infiltrated through at least the peripheral edge portion of the main bore 3 of the gasket element 2. The gasket element 2 is formed in such a manner that the thickness is gradually increased from the peripheral edge portion toward the central area of a designated thickness and the thickness of the main bore peripheral edge portion is uniform. Thus, a surface which comes into contact with a member easy to deform has a three-dimensional structure corresponding to the deformation state of the member so as to improve sealing performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infiltration type sintered metal gasket, and more particularly to a sintered metal gasket useful as a cylinder head gasket or an exhaust gasket of an internal combustion engine.

[0002]

2. Description of the Related Art Generally, various gaskets are used on the joint surface between members through which high-pressure fluid such as high-pressure gas or high-pressure liquid flows. Metal gaskets are commonly used for sealing parts exposed to high temperature and high pressure. However, in the conventional metal gasket, the cylinder head and the cylinder block have been made of aluminum alloy with the recent weight reduction and higher output of the internal combustion engine, and when the metal head is fastened with the fastening bolt, the cylinder head is deformed or distorted. Therefore, there is a possibility that a space near the middle between the fastening bolts or the middle between the cylinder bores becomes large and a leak occurs. Also, in the case of a multi-cylinder engine, since both ends in the longitudinal direction are fastened with a large number of fastening bolts, the surface pressure at both ends of the gasket is much higher than that at the middle part, and the surface pressure of the entire sealing surface is uneven. This impairs the sealability of the gasket, and at the same time hinders the thinning of the gasket.

In order to solve these problems, in the past, in order to compensate for the irregularity of the deck surface space around the cylinder bore that occurs during fastening, a bead is provided at the portion surrounding the cylinder bore of the metal gasket, and the width or width of the bead is provided. It has been practiced to change the height and insert a compensating material into the area surrounding the cylinder bore. However, when the cylinder head is fastened to the cylinder block, the sealing surface is 3
Since it deforms dimensionally, it is practically almost impossible to machine the metal in accordance with it and to make the surface pressure of the peripheral edge of the cylinder bore uniform. It should be noted that it is possible to process one metal thin plate by pressing or other means so as to have a three-dimensional structure, but in this case, it is difficult to maintain the flatness of the entire gasket due to the distortion of the metal thin plate. And
At the time of fastening, there is a problem that stress is concentrated on a local portion of the gasket due to the strain, resulting in stress cracking.

Therefore, the inventor of the present invention, as a gasket replacing the metal gasket, in JP-A-62-192504, forms a gasket element body with a sintered metal and infiltrates the gasket element body with a low melting point metal. On the other hand, we proposed an infiltration type sintered metal gasket having a low melting point metal layer formed on its surface.

[0005]

This infiltration type sintered metal gasket is excellent in cushioning property, does not damage the mating member, and has good thermal conductivity like the metal gasket. It has the advantage of reducing the temperature difference between the block and
With a gasket of uniform wall thickness, it is difficult to obtain sufficient sealing performance because the surface pressure near the cylinder bore on the sealing surface cannot be made uniform due to the deformation of the cylinder head that occurs when the cylinder head is fastened to the cylinder block. Became clear.

Therefore, an object of the present invention is to solve the above problems and to provide a sealing surface which is three-dimensionally deformed when the cylinder head and the cylinder block are fastened without damaging the advantages of the sintered metal gasket. The object is to make the surface pressure of the peripheral portion of the cylinder bore uniform.

[0007]

Means for Solving the Problems The present invention, as a means for solving the above problems, comprises a thin plate-shaped gasket body made of a sintered metal containing iron, an iron-based alloy or a nickel-based alloy as a main component, and A gasket made of a grommet attached to a main bore formed in a gasket body, the infiltration type sintered metal gasket obtained by infiltrating a low melting point metal into at least the main bore peripheral portion of the gasket body, wherein the gasket body Is formed so that its thickness gradually increases from its peripheral portion toward a central region having a predetermined thickness, and the peripheral portion of the main bore has a uniform thickness.

That is, according to the present invention, when a powder for sintering is molded or fired at the same time as molding to obtain a low-density fired body, which is compressed by roll rolling or pressing,
The fired body shrinks only in the compression direction, that is, in the thickness direction, and does not cause widthwise deformation and lengthwise deformation like a bulk material as distortion due to the magnitude of compression, and melts the low melting point metal in the sintered body. Focusing on the fact that even if soaked, the low-melting metal only soaks into the pores and shrinkage or expansion of the sintered body hardly occurs,
A low-density sintered body or sheet-shaped low-density fired body that has been molded into a predetermined gasket shape in advance is compressed into a plate shape with a uniform thickness, which is then punched into a predetermined gasket shape as it is, and then coined. In this way, the surface of the gasket is preliminarily contacted with it at the time of fastening, for example, a three-dimensional structure that follows the deformation of the cylinder head, etc. Is.

[0009]

In the gasket according to the present invention, the wall thickness of the gasket body gradually increases from its peripheral portion toward the central region having a predetermined thickness, and the peripheral wall portion of the main bore is formed to have a uniform wall thickness. At least the surface of the sealing surface that contacts the easily deformable member such as the cylinder head has a three-dimensional structure that corresponds to the deformed state of the member when fastened with the fastening bolts, so that the main bore of the gasket is surrounded at the time of fastening. The surface pressure of the peripheral portion is equalized, and the sealability is remarkably improved.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0011]

FIG. 1 shows an embodiment in which the present invention is applied to a cylinder head gasket, wherein 1 is an infiltration type sintered metal gasket, which is a sintered metal containing iron, an iron-based alloy or a nickel-based alloy as a main component. The gasket body 2 is formed of a thin plate-shaped gasket body 2, and the gasket body 2 has a main bore 3 serving as a cylinder bore, and a plurality of fastening bolt bores 4 formed in the periphery of the gasket body 2 in the vicinity of the main bore 3. Has been done. A low-melting-point metal is infiltrated into a portion surrounding the main bore 3, that is, a peripheral portion of the main bore, and a grommet 5 made of steel or other material is attached to the main bore 3.

As shown in FIGS. 2 and 3, the gasket body 2 has a smooth surface on one side, but the upper surface has a wall thickness of a predetermined thickness from the peripheral portion of the gasket body 2 to a main bore. Is gradually increased toward the center region of the main bore 3 and the thickness of the peripheral portion of the main bore 3 is uniform. Therefore, the gasket body 2 has an entire sealing surface of 3
It has a three-dimensional structure and is formed so that the surface pressure of the peripheral portion of the main bore 3 becomes equal when the cylinder head is fastened to the cylinder block with fastening bolts. Further, a recess 7 surrounding the main bore 3 is formed in the peripheral portion of the main bore 3 by coining so that when the grommet 5 is caulked, the caulking portion surface 5a is flush with the surface of the gasket body 2. There is. As shown in FIGS. 1 and 3, a single or double bead or convex portion 6 is formed on the surface of the gasket body 2 so as to surround the recess in the peripheral portion of the main bore.

According to the present invention, the infiltration type sintered metal gasket can be manufactured as follows. That is, first, iron powder, iron alloy powder or nickel-based alloy powder,
For example, stainless steel (SUS304) powder with a depth of 1 mm
Fill a ceramic mold with square cavities,
This is fired in a high vacuum at 1150 to 1250 ° C for 0.5 to 1 hour to obtain a plate-shaped sintered body having a porosity of 50 to 70% and a thickness of 1 mm. This sintered body is compression-molded to 0.8 to 0.9 mm by roll rolling, pressing, etc. to densify its surface and make its thickness uniform, and then punched into a predetermined gasket shape. Coining is performed to obtain a gasket body having a three-dimensionally structured sealing surface.

The coining may be performed by using a die, and the upper die of the die has a cavity having irregularities opposite to the surface of the gasket to be manufactured, and this cavity has a cylinder head and a cylinder block. When signed to
The depth of the cavities gradually increases from its peripheral portion toward the center area so that the pressure acting on the gasket surface becomes uniform, and the depth of the cavities near the fastening bolt bores is between the adjacent fastening bolt bores. Is formed so as to have a three-dimensional structure so as to form a surface that gradually increases toward the middle part. Further, a projection having a diameter slightly larger than that of the main bore and having a height corresponding to the thickness of the grommet is formed, and a recess having a depth of 100 μm is formed surrounding the projection. On the other hand, in the cavity of the lower mold, a protrusion having a diameter slightly larger than that of the cavity and facing the protrusion of the upper mold and having a height corresponding to the thickness of the grommet is formed.

In such a cavity, for example, an upper plate of a predetermined thickness formed of the same material as the cylinder head is attached to the upper movable plate of the press machine with a bolt having the same diameter as the fastening bolts, and the upper and lower movable plates are actually mounted. When this plate is pressed against the lower plate attached to the lower movable plate by applying a predetermined load that is equal to or more than the fastening force of the cylinder head, it is attached according to the attachment position and number of the fastening bolts of the engine. A force is applied to the mounting portion via a bolt, and the contact surface of the upper plate with the lower plate changes in the same manner as the cylinder head in accordance with the fastening force.Therefore, a mold is formed based on the deformation amount of the contact surface,
It is possible to form. Further, although the convex portion 6 is not always necessary, when the convex portion is formed, the width and height corresponding to the convex portion 6 surrounding the cylinder bore of the gasket body 2 in the cavity of the upper die and / or the lower die. A recess may be provided. The convex portion 6 does not necessarily have to have the same width and height over the entire circumference and can be variously deformed, and the convex portion 6 has an arbitrary cross-sectional shape such as a semicircle, a chevron, or a trapezoid. Can be formed.

Therefore, when coining is performed using the mold, a convex portion 6 having a uniform height is formed on the upper surface of the gasket so as to surround the cylinder bore, and the wall thickness of the convex portion 6 is constant from the peripheral portion. Is formed so as to gradually increase toward a central region of the fastening bolt, and is formed so as to gradually increase from a peripheral portion of the fastening bolt bore 4 toward an intermediate portion of the fastening bolt bore 4.
The peripheral portion of the main bore is compressed so as to be thinned by the thickness of the grommet to form the recesses 7 on the upper and lower surfaces thereof, and the upper surface of the gasket is evenly surrounded by the peripheral portion of the cylinder bore. The convex portions 6 having various heights are formed.

By the way, according to the above method, 150-2
A commercially available stainless steel powder with a grain size of 00 mesh was used to obtain a sintered body having a thickness of 1 mm, which was rolled to a thickness of 0.8 mm. No deformation was observed in the width or rolling direction. After punching the body into the specified gasket shape and coining it, the wall thickness of the peripheral portion of the bolt bore was 0.4 mm and the average thickness of the central area of the gasket was 0.7 m.
A gasket body having m and a height of the convex portion of 5/100 mm and a depth of the recess 7 of 0.2 mm was obtained.

On this gasket body, low-melting metal rings, for example, copper rings are placed coaxially with the main bore 3 and the bolt bore 4, respectively, and heated at 1200 ° C. in a high vacuum to infiltrate copper, Infiltrated portions are formed on the peripheral portion of the main bore and the peripheral portion of the bolt bore. Then the main bore 3
After mounting the grommet 5 on, the metal mold having the same cavity structure as the coining mold is used for finishing press to make the surface of the gasket into a three-dimensional structure that follows the deformation of the members such as the cylinder head at the time of fastening. Finish to obtain an infiltration type sintered metal gasket. If necessary, after performing the finishing press, the non-infiltration part may be impregnated with silicon rubber, and then molybdenum disulfide may be applied to both surfaces as a solid lubricant.

In the above-mentioned embodiment, the gasket body is formed by the firing method in which molding and sintering are carried out at the same time, but it may be formed by a press molding method or a powder rolling method. In the case of the press molding method, for example, iron powder, iron alloy powder or nickel-based alloy powder is filled in a die and pressure-molded into a predetermined gasket shape, which is then demolded in a non-oxidizing atmosphere at 500 to 800 ° C. After brazing, it is fired at 1100 to 1300 ° C. in a non-oxidizing atmosphere to obtain a low density sintered body,
After the pressure molding of the sintered body again, coining is performed so that the wall thickness gradually increases from the peripheral portion toward the central region of a predetermined thickness and the peripheral wall portion of the main bore has a uniform wall thickness. good.

Further, in the case of the powder rolling method, iron powder, iron alloy powder or nickel-base alloy powder is rolled by a rolling roll and then presintered or further sintered in a sintering furnace as it is to continuously produce a low density powder. A thin plate-shaped pre-sintered body or a sintered body is obtained, which is punched into a predetermined gasket shape, and then its wall thickness gradually increases from its peripheral portion toward the central region of the predetermined thickness, and the peripheral portion of the main bore. The coining may be performed so that the thickness of the product is uniform. By the press molding method and the powder rolling method, it is possible to obtain a sintered body having a relative density of 55 to 95%, but if the density becomes high, it becomes difficult to process by coining, so that a sintered body having a relative density of 55 to 70% is used. Is preferably used.

In the above embodiment, since the raw material powder is stainless steel, the sintering is carried out in a high vacuum, but it may be carried out in hydrogen or decomposed ammonia gas, and the raw material powder is other than stainless steel. Material, eg Fe
In the case of other iron-based materials such as —C, Fe—Cu, and Fe—Ni, other than these, argon gas, nitrogen gas, or any other known non-oxidizing atmosphere may be used. The calcination temperature and the calcination temperature differ depending on the kind of the raw material of the sintered body, but in the case of iron, calcination is usually performed at a temperature of 400 ° C. or higher and sintering is performed at a temperature of 1000 to 1300 ° C.

Further, although the low melting point metal is locally infiltrated in the above embodiment, it may be entirely infiltrated. The low melting point metal used for this depends on the material of the cylinder head and the cylinder block, but usually has a melting point lower than that of the sintered metal forming the gasket body,
Lead, zinc, tin, aluminum and their alloys are preferred.

When the number of fastening bolts is small and the total fastening force is small, in order to provide the same sealing performance as when the number of fastening bolts is large, the cylinder bore 3 is used in the above embodiment.
Although a convex portion 6 surrounding the cylinder bore 3 is provided in the vicinity of, the convex portion is not always necessary. Further, when the cylinder head is fastened to the cylinder block with a bolt, the convex portion prevents leakage from a portion where the pressure is weakened, so the portion where the pressure is weakened, that is, the convex portion in the central portion between the fastening bolt bores. The height may be made higher than that of the convex portion 6 near the fastening bolt bore, or the width thereof may be made wider.

In the above-mentioned embodiment, the case where the present invention is applied to the head gasket has been described. However, it is needless to say that the present invention is not limited to this and can be applied to exhaust gaskets and gaskets for other uses.

A grommet is attached to the gasket body, but this grommet is not always necessary.
Further, instead of the grommet, a metal plate having the same shape as the gasket element body and having the end edge of the main bore bent upward at a substantially right angle is attached to the lower side of the gasket element body, and the edge portion is covered. It may be integrated with the gasket body.

Further, when the grommet is mounted, a ring-shaped recess for accommodating the bent part of the grommet is formed on the peripheral edge of the bore in the gasket body, and the low melting point is provided only in the portion surrounding the recess. The metal may be infiltrated, or the second metal having a melting point lower than that of the metal infiltrated in the infiltrated portion may be infiltrated in a portion other than the infiltrated portion. good. By doing so, it is possible to improve the thermal conductivity of the gasket main body and at the same time bring the thermal expansion coefficient thereof closer to the thermal expansion coefficient of the material of the cylinder head to reduce stress strain. In this case, it is preferable that the bottom of the recess or the bottom of the recess and the portion surrounding the recess be infiltrated with copper, and the other portions be infiltrated with lead, zinc, tin, aluminum and alloys thereof. is there.

A heat resistant seal member made of a heat resistant elastic material such as a soft grommet made of copper or a copper alloy, silicon rubber or the like may be fitted to the cooling water bore and the lubricating oil bore.

[0028]

As described above, according to the present invention, the wall thickness of at least one side of the gasket body of the infiltration type sintered metal gasket is gradually increased from the peripheral portion toward the central region of the predetermined thickness. In addition, since the wall thickness near the fastening bolt bores is gradually increased toward the middle portion between the adjacent fastening bolt bores, the surface pressure of the peripheral portion surrounding the main bore of the gasket is reduced during fastening. Can be equal,
Since the sintered body shrinks only in the compression direction, that is, in the thickness direction, and does not deform laterally regardless of the size of the compression like the bulk material, it is possible to reduce the thickness of the gasket which was impossible with the conventional metal gasket. It has an excellent effect that it can be achieved by re-compression molding and that a gasket having excellent cushioning property, sealing property, durability and heat resistance can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment in which the present invention is applied to a cylinder head gasket.

FIG. 2 is a sectional view taken along line AA of FIG.

3 is a cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

 1: Infiltration type sintered metal gasket 2: Gasket body 3: Cylinder bore (main bore) 4: Fastening bolt bore 5: Grommet 6: Convex part

Claims (6)

[Claims] 1. A thin plate-shaped gasket element body made of a sintered metal containing iron, an iron-based alloy or a nickel-based alloy as a main component, and a grommet mounted on a main bore formed in the gasket element body, In an infiltration type sintered metal gasket obtained by infiltrating a low melting point metal into at least the main bore peripheral portion of the gasket body, the gasket body is formed from the peripheral portion toward a central region of a predetermined thickness. An infiltration type sintered metal gasket, characterized in that the gasket is formed so as to be gradually increased and have a uniform thickness at the peripheral portion of the main bore. 2. The gasket according to claim 1, wherein a convex portion surrounding the main bore is formed on a peripheral portion of the main bore. 3. The low melting point metal is at least one metal selected from the group consisting of copper, lead, zinc, tin, aluminum and alloys thereof.
Gasket described in. 4. A mold is filled with iron powder, iron alloy powder or nickel-base alloy powder, which is fired in a non-oxidizing atmosphere to obtain a low-density plate-shaped sintered body, which is rolled and rolled. After uniformizing the thickness, punching into a specified gasket shape,
Next, coining is performed so that the wall thickness gradually increases from the peripheral portion toward a central region of a predetermined thickness, and the wall thickness of the peripheral portion of the main bore becomes uniform. Gasket manufacturing method. 5. Iron powder, iron alloy powder or nickel-based alloy powder is filled in a die and pressure-molded into a predetermined gasket shape, which is dewaxed and then fired in a non-oxidizing atmosphere. After obtaining a low-density sintered body and press-molding the sintered body again,
An infiltration type sintered metal gasket characterized in that coining is performed so that the wall thickness gradually increases from the peripheral portion toward a central region of a predetermined thickness, and the peripheral wall portion of the main bore has a uniform wall thickness. Manufacturing method. 6. Iron powder, iron alloy powder or nickel base alloy powder is rolled by a rolling roll and sintered as it is to obtain a low density thin plate-like sintered body, which is punched into a predetermined gasket shape. Infiltration-type firing characterized by being machined and then coined so that its wall thickness gradually increases from its peripheral portion toward a central region of a predetermined thickness, and the wall thickness of the peripheral portion of the main bore becomes uniform. A method for producing a bonded metal gasket.