JPH0650434A - Manufacture of metallic gasket - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of a metallic gasket where generation of cracks, etc., through the work hardening is prevented at a part to be folded and bent in the folding/bending operation to form a folded part of an elastic metallic sheet. CONSTITUTION:A plurality of bore holes having an inner diameter which is smaller than that of cylinder bore holes 2 are made in an elastic metallic sheet 3, the circumferential part of the bore holes of the elastic metallic sheet, i.e., a folded/bent part 7 is folded/bent, and a double-folded part 5 is formed where the double-folded edge part is made the cylinder bore holes 2. An annular groove part 6 is formed at the folded/bent part 7, providing a thin-walled part. Martensite precipitation and generation of the work hardening is prevented at the folded/bent part 7 by executing the folding/bending operation at the temperature below the recrystallization temperature of the material of the elastic metallic sheet 3 and within the temperature range where the work hardening is generated with difficulty.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal gasket used for sealing between opposing mounting surfaces of a cylinder head and a cylinder block in a multi-cylinder internal combustion engine.

[0002]

2. Description of the Related Art Heretofore, a metal gasket made of a metal material has been used to seal between opposing mounting surfaces between a cylinder head and a cylinder block in an internal combustion engine. Recent internal combustion engines are required to have high output and light weight, and as a part thereof, there is a tendency to manufacture a cylinder head, a cylinder block and the like from a conventional steel having a large specific gravity and an aluminum material having a small specific gravity instead of a casting. The aluminum alloy material is light in weight, but has low rigidity, which may cause inconvenience when tightening the metal gasket and operating the internal combustion engine. That is, since the tightening bolt positions of the metal gasket are dispersed in the outer peripheral portion or the relatively outer peripheral portion of the metal gasket and are not necessarily evenly distributed around the cylinder bore hole, these structures having reduced rigidity When tightening the opposing mounting surfaces between materials with a tightening bolt through a single plate metal gasket,
The opposing mounting surface is likely to be irregular. As a result, high-temperature and high-pressure combustion gas penetrates between the opposing mounting surfaces at locations with large strain, such as between the cylinder bore holes, and corrodes the bead portion of the metal gasket interposed between the opposing mounting surfaces. Stain and reduce the sealing effect.

Furthermore, since the rigidity of these structural materials decreases, the relative displacement of the cylinder head with respect to the cylinder block increases according to the combustion cycle during operation of the internal combustion engine, and the distance between the cylinder head and the cylinder block increases or decreases. Since the temperature change of the metal gasket greatly changes with repeated operation and stop and operation of the internal combustion engine, repeated stress, that is, mechanical stress and thermal stress also acts on the metal gasket. This load fluctuation stress occurs as a large value in the lowest rigidity part of the cylinder block or cylinder head, and as a result,
The bead formed on the elastic metal plate may be settled or cracked to deteriorate the sealing performance.

The applicant of the present invention has already applied for a single-plate metal gasket and a method for producing the same as Japanese Patent Application No. 2-306295. Regarding the metal gasket, a cylinder bore hole formed in an elastic metal plate, a bead formed along the cylinder bore hole radially outwardly from a peripheral edge of the cylinder bore hole, and a convex surface of the bead around the cylinder bore hole. Has a folded-back portion formed by folding back outward in the radial direction on the side, and the folded-back portion of the metal plate is formed to a preset thickness and heat-treated.
Therefore, when the metal gasket is tightened between the opposing mounting surfaces and brought into a pressed state, the bead forms an annular seal portion with respect to the opposing mounting surface, and at the same time, the folded-back portion having a plate thickness of about twice is formed in the cylinder bore hole. By forming another seal portion around the, the bead and the folded portion absorb the irregularities of the opposing mounting surface, suppress the amount of distortion of the cylinder head that occurs in repeated combustion cycles, reduce fluctuating load stress, Full compression of the beads can be prevented.

Further, in the method for manufacturing a metal gasket, the elastic metal plate is formed with a bore hole having an inner diameter smaller than that of the cylinder bore hole after completion of the forming, and the bore is spaced from the peripheral edge of the bore hole to the outer side in the radial direction. Form the bead along the
A fold portion having a fold edge portion as a cylinder bore hole is formed by bending outwardly in the radial direction on the convex side of the bead around the bore hole, and a compression force is applied to the fold portion to set a preset thickness. And heat-treating the metal plate on which the folded portion is formed. The manufacturing method of the metal gasket further discloses that a soft metal plate is sandwiched in the step of forming the folded portion.

When bending the elastic metal plate to form the folded-back portion, the following phenomenon occurs when the bending is cold-worked. When a cold-worked metal is heated, changes such as disappearance of excessive point defects and rearrangement of dislocations that occur in the crystal occur. During this recovery process, the density and electric resistance of the metal alloy also change and residual stress is removed, but the strength does not decrease significantly. Low temperature annealing of the metal is to control this recovery process. When the heating temperature is further increased, recrystallization occurs and the properties of the cold-worked material return to the original softened state. If re-crystallization is completed and further annealing is continued, the crystal grains gradually grow, and the mechanical properties of the polycrystalline material are sensitively affected by the crystal grain size.

[0007] Polycrystalline materials take a specific preferential orientation when subjected to strong cold working such as rolling or drawing. This is a deformed texture, and when such a processed material is annealed at a high temperature, it has a recrystallized texture. The texture differs depending on the type of metal, the purity, the method of processing, the degree of processing, or the annealing conditions. If the crystal grains having a specific crystal orientation are given priority, anisotropy will occur in mechanical or physical properties. Since recrystallization is a velocity process,
The longer the heating time, the lower the recrystallization temperature. Usually, the heating temperature at which recrystallization is completed is the recrystallization temperature. The recrystallization temperature T _R of the pure metal is proportional to the melting point T _M of the metal expressed as an absolute temperature, T _R ≈ (0. 3-0.
5) T _M , that is, T _R and (0.3 to 0.5) T _M have a substantially equal relationship.

Generally, regarding recrystallization of a metal, when a crystal which is plastically strained by cold working or the like is heated, a process in which internal stress is reduced is followed by an internal crystal grain from which the strain remains. A new crystal nucleus without strain is generated, and as the number increases, each nucleus gradually grows and replaces the original crystal grain. The temperature at which recrystallization occurs is called the recrystallization temperature. This temperature is significantly affected by the purity or composition of metals and alloys, the degree of plastic strain within the crystal, and the time of heating. Further, regarding the crystal grain coarsening, it means a phenomenon that the crystal grain becomes large by heating the polycrystalline material to a high temperature.

[0009]

However, the above-mentioned metallic gasket proposed by the present applicant also has the following technical unsolved problems. That is,
The metal gasket described above basically includes an elastic metal plate having a folded portion formed by forming a bore hole having an inner diameter smaller than that of the cylinder bore hole and folding the bore hole radially outward around the bore hole. Therefore, such an elastic metal plate has a structure in which the folded-back portion is completely folded back without a gap of 180 degrees at the folded-back edge portion which becomes the cylinder bore hole, and undergoes severe stress change during processing. Work hardening has occurred, causing damage such as cracks and cracks in the bent portion, or even though heat treatment is applied, it is exposed to repeated stress according to the combustion cycle for a long time after tightening between the opposing mounting surfaces, It is easy for cracks to occur at the folded edge that defines the portion, that is, the cylinder bore hole.

Also in the method of manufacturing a metal gasket, the metal gasket proposed in the above-mentioned prior application has limitations in the thickness, hardness and elongation characteristics of the elastic metal plate used. In other words, regarding the thickness of the elastic metal plate, the thickness of the folded portion is not adjusted in advance, so it is necessary to perform the folding process with the thickness of the adopted elastic metal plate, and the force required for processing is large. In the so-called pre-compression in which there is a risk of cracks, etc. that causes a sudden change in plate thickness at the folded edge, and the so-called pre-compression in which the plate thickness is adjusted by a press after folding, the adjustment amount becomes large and the plate thickness adjustment accuracy Since it is difficult to improve the flatness and the flatness, there are restrictions on the plate thickness that can be adopted.
Regarding the hardness of the elastic metal plate, it is difficult to fold it with a material having high hardness.
It is necessary to select and use the following elastic metal plates that are relatively soft and maintain a hardness that is easy to process, and this also limits the hardness of the elastic metal plate that can be adopted. Further, regarding the elongation characteristics of the elastic metal plate, if a material having poor elongation characteristics is used, cracks, cracks,
Strain or the like is likely to occur, and therefore, there is a restriction that an expensive elastic metal plate having good elongation characteristics must be adopted in order to prevent generation of cracks, fractures, strains and the like.

Further, when bending is performed in a room temperature atmosphere, that is, cold working for forming a folded portion on the elastic metal plate, a phenomenon using some SUS causes precipitation of processed martensite. When martensite precipitation occurs in the folded portion, work hardening occurs in that portion, folding becomes difficult, and cracks, cracks and the like occur, and in particular, the bent portion of the elastic metal plate is formed thin. The phenomenon of precipitation of martensite appears significantly in the material.

Regarding the mechanism of generation of worked martensite, S which is a metastable austenitic stainless steel.
The steel types of US301 and SUS304 undergo a phase transformation that precipitates martensite during processing, that is, during plastic working. These materials precipitate the martensite when subjected to processing at temperatures above the Ms point. The Md of 30 points serves as a guide. This is when it receives 30% strain,
It shows the temperature at which martensite precipitates 50%, and M
The Md30 point is on the higher temperature side than the s point. Therefore, martensite precipitates between the Md point 30 and the Ms point. The Md30 point is simply obtained from a mathematical formula by multiplying the chemical component by a coefficient, and when SUS301 and 304 are compared, SUS301 is more Md30 than SUS304.
It has a high point and is a type of steel in which martensite is likely to occur. In other words, it indicates that SUS301 is more easily work-hardened than SUS304. The martensitic transformation is caused by a kind of shear deformation, and it is considered that the transformation is promoted because a mechanical driving force works due to external shear stress.

Therefore, an object of the present invention is to solve the above-mentioned problems. Prior to forming the folded-back portion by bending the elastic metal plate, the plate thickness of the region of the elastic metal plate on the folded inner surface side is formed. The material is used for the temperature range in advance, and bending is performed at a temperature determined by the processing history of the material to prevent cracks, cracks, strains, etc. from occurring in the bent portion of the elastic metal plate. It is to prevent the occurrence of cracks, cracks, distortion, etc. at the folded portion by performing warm working on the thinned bent portion of the plate.
By thinning the elastic metal plate and performing the bending process at a warm temperature, the restrictions on the material of the elastic metal plate in terms of thickness, hardness, and elongation characteristics can be relaxed, and cracks, cracks, strain, etc. can be prevented from occurring at the folded portion. It is an object of the present invention to provide a method for manufacturing a metal gasket that can be prevented and can be obtained with good quality and at low cost.

[0014]

In order to achieve the above object, the present invention is configured as follows. That is, according to the present invention, a plurality of bore holes having an inner diameter smaller than that of a cylinder bore hole are formed in an elastic metal plate, and a portion around the bore hole of the elastic metal plate is bent to form a folded portion having a folded edge portion as a cylinder bore hole. In the method for manufacturing a metal gasket to be formed, the bending of the peripheral portion of the bore hole is performed at a temperature within a temperature range where work hardening is less likely to occur at a recrystallization temperature of the material of the elastic metal plate or less. The present invention relates to a method for manufacturing a gasket made of plastic. The term "warm" as used herein means an intermediate temperature between hot and cold and means a temperature not higher than the recrystallization temperature and not lower than room temperature.

Further, in this method for manufacturing a metal gasket, an annular groove portion for thinning the elastic metal plate is formed in a bent portion of the elastic metal plate, and the folded portion is formed by bending the annular groove portion, A bead is formed along the cylinder bore of the elastic metal plate so that the folded-back portion side is a convex portion.

Further, in this method for manufacturing a metal gasket, another elastic metal plate is laminated on the elastic metal plate, and a bead is formed along the cylinder bore hole on the another elastic metal plate, and a convex portion of the bead is formed. Is disposed on the side of the elastic metal plate that faces the folded portion.

Further, in this method of manufacturing a metal gasket, a bead having a convex portion on the side of the folded portion is formed along the cylinder bore hole on the elastic metal plate, and formed on another elastic metal plate along the cylinder bore hole. The convex portion of the bead is made to face the convex portion of the bead of the elastic metal plate, and the another elastic metal plate is laminated on the elastic metal plate, and the elastic metal plate and the other elastic metal plate are further laminated. Further, each convex portion of the bead formed on the other pair of elastic metal plates is arranged in contact with each concave portion of each bead of the elastic metal plate and the another elastic metal plate.

[0018]

The method of manufacturing a metal gasket according to the present invention is configured as described above and operates as follows. That is, the method for manufacturing the metal gasket is such that the bending process of the peripheral portion of the bore hole formed in the elastic metal plate is performed at a temperature range in which the work hardening is less likely to occur at the recrystallization temperature of the material of the elastic metal plate or less. Therefore, in the bending process of the bent portion of the elastic metal plate, to prevent the martensite precipitation in the bent portion, particularly in the annular groove portion thinning the bent portion, and to remove the influence of work hardening of the bent portion. Therefore, the bending process can be easily performed without causing cracks, cracks, strains, and the like.

However, in the cold working of the bent portion of the elastic metal plate at room temperature, when the thinned portion of the annular groove portion is bent, martensite precipitation occurs in the annular groove portion and the bead forming portion, The part is hardened, making bending difficult, and cracks, cracks, strains, etc. occur in the part.

Further, in the method for manufacturing a metal gasket according to the present invention, when the periphery of the bore hole formed in the elastic metal plate is folded back, the folding side of the elastic metal plate is located inside the folding edge of the folding portion in advance. Since the region to be bent is formed thin, the force required to fold it back is small, and the wrapping process is performed by gradually deforming the metal material instead of 180 degrees suddenly and completely, and therefore, When forming the folded edge portion, damage to the metal material is small, and residual concentrated stress is also relaxed.

[0021]

Embodiments of the method for manufacturing a metal gasket according to the present invention will be described below with reference to the drawings. FIG. 1 is a partial plan view showing an embodiment of a metal gasket manufactured by the method for manufacturing a metal gasket according to the present invention.

The metal gasket shown in FIG. 1 is used to seal the opposing mounting surfaces of the cylinder head and the cylinder block in a multi-cylinder engine.
The metal gasket is a single plate or a plurality of elastic metal plates 1,
3 and the thickness t is about 0.10 to 0.30 mm depending on the structure of the metal gasket. Further, in order to bend and bend the elastic metal plate 1 according to the present invention, it is preferable that the elastic metal plate 1 is made of a soft metal material having a hardness before quenching up to Hv200, that is, a soft metal. If the elastic metal plate 3 having the annular groove portion 6 is used, the elastic metal plate 3 has a hardness before quenching of Hv35.
It can be processed with a hardness of 0.

In the case of a metal material, generally, when the elastic metal plate is bent to form a metal gasket, if the elastic metal plate is thin-walled, work hardening easily occurs during the bending process. As a material for bending the elastic metal plates 1 and 3 constituting the metal gasket,
These include: The material to be subjected to the heat treatment for producing the elastic metal plates 1 and 3 is SUS630, which is a precipitation hardening material.
SUS631, nitriding material SUS304, SUS
301, SK material, SU as quenching / tempering material
As S420J, SUS440A and aging treatment material,
Maraging steel, titanium alloy, aluminum alloy, copper alloy, nickel alloy (Heron's alloy, Inconel, etc.)
Is. For materials that are not subjected to heat treatment for producing the elastic metal plates 1 and 3, SUS301, SUS304,
SUS310S, aluminum alloy, copper alloy, titanium alloy, nickel alloy and mild steel plate.

Elastic metal plate 1 in metal gasket 1,
3, the number of cylinders of the multi-cylinder engine, that is, the number of holes corresponding to the number of cylinder bores formed in the cylinder block, that is, the cylinder bore holes 2A, 2B, 2C .. There is. Further, in the elastic metal plates 1 and 3 of the metal gasket, oil holes and oil return holes 16 through which oil is passed, bolt holes 17 through which bolts for fastening the metal gasket between opposing mounting surfaces are inserted, and water holes through which cooling water is passed. 18, a plurality of knock holes, rivet holes and the like are formed.

Although not shown, for both the front and back surfaces of the metal gasket, heat-resistant and oil-resistant rubber such as fluororubber and a non-metal material such as resin, for example, having a thickness of 1
By applying a coating of about 0μ to 50μ,
A metal-to-metal contact state with the cylinder head and the cylinder block can be avoided, and corrosion resistance, durability and strength as a gasket can be secured. The application of the non-metallic material is preferably completed after forming the bore holes and adjusting the wall thickness of the elastic metal plates 1 and 3 and before starting the bending process.

An embodiment of the method of manufacturing a metal gasket according to the present invention will be described with reference to FIGS. 2, 3 and 4. 2 is a sectional view taken along the line AA in FIG. 1, and FIG.
FIG. 4 is an enlarged view of a folded portion that is a part of FIG. 4 and FIG. This method of manufacturing a metal gasket is particularly suitable for forming the folded portion 5 by bending the bent portion along the circumference of the cylinder bore hole 2 of the elastic metal plates 1 and 3 forming the metal gasket. It is characterized in that the bending process is performed at a warm temperature set to.

In this metal gasket manufacturing method, the warm working means working in a temperature range in which work hardening hardly occurs below the recrystallization temperature of the elastic metal plate 3. In this warm working, it is necessary that the elastic metal plate 3 to be bent reaches that temperature, and it does not make sense to reach that temperature after the bending work is completed. Therefore, in order to warm work the elastic metal plate 3, for example, when bending is performed with a mold, the elastic metal plate is sandwiched between the molds and the mold is heated to keep the temperature of the elastic metal plate warm. It is necessary to bend the elastic metal plate 3 after the temperature has risen to the temperature range between them.

In this method of manufacturing a metal gasket, mainly, a plurality of bore holes 13 having an inner diameter smaller than that of the cylinder bore hole 2 are formed in the elastic metal plate 3, and the peripheral portion of the elastic metal plate 3, that is, the bent portion is formed. The bent portion 5 is formed by bending and the folded edge portion 15 serves as the cylinder bore hole 2. The bending of the peripheral portion of the bore hole is less likely to cause work hardening at the recrystallization temperature of the material of the elastic metal plate 3 or less. It is characterized in that it is performed in the warm temperature range. That is,
In this method of manufacturing a metal gasket, the lower limit temperature of the warm working temperature range is about 50 ° C. higher than the high temperature point where the martensite precipitation of the material occurs as the warm temperature range when performing the bending process. Set to (M _d + 50 ° C),
The upper limit temperature is preferably set to a temperature range of about 50 ° C. lower than the upper limit temperature of the temperature range that does not affect the structure and strength of the material.

With respect to the method of manufacturing the metal gasket, the elastic metal plate 3 is bent at a temperature within an appropriate temperature range so that the thin portion of the elastic metal plate 3 is not work-hardened and the bending process is easy. You can do it
Even a relatively hard material can be bent, a crack, a crack, a crack, etc. do not occur, and a metal gasket having high durability can be manufactured.

When the following material is selected as the elastic metal plate 3 of the metal gasket, for example, as a material for precipitating and hardening martensite by cold working, among metastable austenitic materials. , SUS301 and SUS304.

The temperature range in the warm working is appropriately selected depending on the material to be bent. For example, SUS301, SUS with martensite precipitation
For 304 and SUS630 materials, the temperature range is 10
It is selected from 0 to 500 ° C. Also, SPCC, SPC
For D and SPCE materials, the temperature range is selected to be 50 to 150 ° C, and for aluminum alloys, the temperature range is 100 to 35 ° C.
The temperature range is 100-500 for copper alloys selected at 0 ° C.
The temperature range is 100 ~ 75 for titanium alloy.
Selected as 0 ℃, the temperature range is 10 for maraging steel.
It is selected at 0 to 480 ° C.

In the method of manufacturing the metal gasket, specifically, first, a desired cylinder bore hole 2 is formed in the elastic metal plate 3.
The bore hole 13 is formed in a radius smaller than the above by a predetermined length. The bore hole 13 is a hole that becomes a folded edge portion, that is, a folded tip 15 when bending is completed. Further, various holes such as the bolt holes 17 other than the cylinder bore hole 2 are formed by punching. Next, the folded width L ₄ is radially outward from the peripheral edge of the bore hole 13.
The annular region having a predetermined width L ₅ (0.6 mm in the illustrated example) centering on the portion of the distance of (6) and the portion where the folding tip 15 is located (a distance of twice the folding width L ₄ from the bore hole 13). An annular region having a predetermined width L ₆ (0.6 mm in the illustrated example) around the position) is formed thin to form annular groove portions 6 and 8, respectively. The thinning is performed from the surface of the elastic metal plate 3 on the folded side. A predetermined interval (0.5 in the illustrated example) is provided between the thin portion 7 of the annular region and the thin portion 9 of the annular region.
(mm), a region without thinning is formed. The thinning depth is 0.02 mm in the illustrated example.

In order to reduce the thickness of the annular groove portions 6 and 8 formed in the elastic metal plate 3, any processing method such as press molding, etching or cutting may be adopted. In the case of press molding, it is possible to perform press molding simultaneously with punching of the bore hole 13. Next, the bead 4 is formed in the elastic metal plate 3 along the cylinder bore hole 2, and the folding width L ₄ around the bore hole 13 to the center line of the annular groove portion 6 is formed.
The fold-back portion 1 having the fold-back portion 1 is subjected to a bending process outward in the radial direction on the surface side having a reduced thickness.
The surface 12 of 1 is brought into contact with the surface 10. Folded edge 15
Are brought into the central position of the annular groove 8 or the thinned annular region. When the bending process is completed, the folded-back portion 5 having the cylinder bore hole 2 on the inner circumference of the folded-back folded edge portion 15 is formed. Finally, the elastic metal plate 3 having the folded-back portion 5 formed thereon is heat-treated to cure the elastic metal plate 3 to manufacture a metal gasket having proper elasticity.

Further, after the bending process for forming the folded-back portion 5 and before heat-treating the metal gasket, a compressive force is applied to the folded-back portion 5 in the plate thickness direction to a preset thickness. It is possible to perform a step of micro-deformation. That is, the cylinder head has a lower rigidity than that of the cylinder block, and in a multi-cylinder engine, a portion between the adjacent cylinder bore holes 2 is likely to be most distorted due to load fluctuations in a combustion cycle of an internal combustion engine in an explosion stroke and an expansion stroke. By the way. Therefore, since the sealing function of the metal gasket is most likely to deteriorate in this portion, the sealing performance in the region between the cylinder bore holes 2 of the folded portion 5 is stronger than the sealing performance in the region other than between the cylinder bore holes 2. In order to achieve this, it is conceivable that the plate thickness of the folded-back portion 5 located in the region between the cylinder bore holes 2 is made thicker than the plate thickness of the folded-back portion 5 located in the region other than between the cylinder bore holes 2. Therefore, after the bending process of the folded-back portion 5, the folded-back portion 5 located in the region other than between the cylinder bores 2 is positioned between the cylinder bores 2.
A step of applying a compressive force for deforming a larger amount may be provided.

In FIG. 2, a line A connecting the boundary portions of the adjacent cylinder bore holes 2A, 2B, 2C ... Formed in the elastic metal plate 3 to the centers of the cylinder bore holes 2A, 2B.
The cross section of the metal gasket cut at -A, that is, the cross section between the cylinder bores 2 is shown, but it is needless to say that the boundary section between other adjacent cylinder bores 2 also has the same cross section structure. Is.

This metal gasket is composed of a single elastic metal plate 3. For the elastic metal plate 3, the thickness t is in the range of about 0.10 to 0.30 mm, for example, about 0.25 mm, and the portion near the periphery of the cylinder bore 2 is concentric with the cylinder bore 2. And beads 4A, 4B, 4 having a mountain-shaped cross section, that is, an uneven portion surrounding the ring
C ... Is formed (reference numeral 4 is a general term for beads). The beads 4 are associated with each other in a region between the adjacent cylinder bore holes, such as between the cylinder bore holes 2A and 2B, to form one bead 4.
Has become. Cylinder bore hole 2 at the meeting of beads 4
While the distance from to becomes gradually shorter, the width of the bead 4 becomes narrower as described above. However, when the distance between the cylinder bore holes 2 is sufficient, the adjacent beads 4 may be arranged with a slight gap therebetween without overlapping each other. In the illustrated example, the bead 4 starts at a distance L ₂ (for example, about 2.0 mm) from the inner peripheral edge of the cylinder bore hole 2, and a predetermined width L _{3 in} the radial direction is about the area between the cylinder bore holes. 2 mm, and about 2.5 mm in the area other than between the cylinder bore holes. The bead 4 in the region other than between the cylinder bores has a width of 5 mm and the top of the convex side is formed substantially flat to stabilize the contact between the bead 4 and the opposing mounting surface although the spring constant is slightly reduced. . The height H of the bead 4 is 0.25 mm, which is the thickness of the elastic metal plate 3.
It is a degree. The diameter of the cylinder bore is 87 mm,
The distance L ₁ between the adjacent cylinder bore holes 2 is, for example, about 6.0 mm.

The elastic metal plate 3 has folded portions 5A, 5B and 5C (hereinafter, the folded portions are collectively referred to as reference numeral 5) at the periphery of the cylinder bore hole 2. The folded-back portion 5 is formed so as not to overlap the bead 4 on the convex surface side of the bead 4 and on the radially inner side of the bead 4. The radial width of the folded portion 5 of the elastic metal plate 3, that is, the folded width L ₄ is, for example, about 1.5 mm.

As shown in the enlarged view of the folded portion 5 in FIG.
In the region of the folded edge portion 7 of the folded portion 11, a circumferential groove portion, that is, an annular groove portion 6 is formed and thinned, and an annular hollow portion, that is, a gap 14 is formed and folded back. In the region outside the gap 14 in the radial direction of the cylinder bore 2, the folded inner surface 12 of the folded portion 11 is in contact with the non-thinned surface 10 of the elastic metal plate body. Further, since the portion 9 of the elastic metal plate body to which the folded-back end of the bore hole 13 of the folded-back portion 5 faces is partially thinned from the folded-back surface side and formed in the circumferential groove portion, that is, the annular groove portion 8, The folded end does not contact the surface of the elastic metal plate 3.

The metal gasket is interposed between the cylinder head and the cylinder block and, for example, when the metal gasket is tightened by a bolt passing through the bolt hole 17 and brought into a pressed state, the bead 4 and the folded portion 5 of the elastic metal plate 3 are provided. And are in contact with the opposing mounting surface to form a double annular seal around the cylinder bore 2. These two-stage annular seal portions prevent the high-temperature and high-pressure combustion gas from the cylinder bore hole 2 from leaking to the opposing mounting surfaces. Further, when the cylinder head and the cylinder block are tightened, even if the opposing mounting surfaces of the cylinder head and the cylinder block become irregular, the folded-back portion 5 and the bead 4 are deformed correspondingly,
As described above, the uneven gap is absorbed together with the increase in the annular seal portion. The folded-back portion 5 supports the bead 4 by sharing the tightening force, and prevents the bead 4 from being compressed by the plate thickness of the folded-back portion 5, so that the bead 4 is prevented from settling. Further, due to the increase in the annular seal portion and the absorption of the irregularity of the facing mounting surface, the amount of distortion of the cylinder head that is repeatedly generated during the combustion cycle of the explosion and expansion stroke of the internal combustion engine is suppressed, and the occurrence of cracks in the seal portion Can be prevented. The function of such a metal gasket is no different from the conventional one.

When such a metal gasket is sandwiched between the opposing mounting surfaces of the internal combustion engine and tightened, the surface 1 that comes into contact with the elastic metal plate 3 or the elastic metal plate body at the folded-back portion 5.
Since the tightening force is shared and supported in the annular region of 0, the region of the folded edge 7 and the folded end (bore hole 13) having the gap 14 is not pressed against the elastic metal plate 3 main body, and Even if they make contact, the pressing force is sufficiently small. Therefore, in the thin portion 7 of the folded edge portion 15, the gap 14 is not absorbed by tightening the metal gasket, and the gap 14 is secured even after the tightening is completed, so that the thin portion 7 of the folded edge portion 15 is crushed. No stress concentration occurs, and therefore, the folded edge 15 of the thin portion 7 is not cracked or distorted when the metal gasket is tightened. Further, although the load fluctuation due to the operation of the internal combustion engine also acts on the folded edge portion 15, the stress variation acting on the folded edge portion 7 is alleviated, and the folded edge portion 1 is used even during long-term use.
No cracks, distortions, cracks, etc. occur in No. 5. Further, since the folded-back end portion 13 does not contact the elastic metal plate main body due to the circumferential groove portion 8 which is a recessed portion, the folded-back tip end 13 is not in contact with the elastic metal plate body when the metal gasket is tightened and the internal combustion engine is operating. The edges do not cause indentations, scratches or cracks on the surface of the elastic metal plate body.

The folded-back portion 5 forms a step with respect to the elastic metal plate body, but the surface of the elastic metal plate 3 on which the folded-back tip 13 is located is thinned to form an annular groove portion 8. When the metal gasket is tightened between the opposing mounting surfaces, the elastic metal plate 3 is deformed so as to eliminate such a step.
Since the elastic metal plate 3 can be bent from the starting position of the thin portion 9 in the annular region located radially inward of the folded edge 15, bending stress generated in the elastic metal plate body at the step portion is reduced.

FIG. 5 is a sectional view in the region between the cylinder bores showing another embodiment of the metal gasket. The metal gasket of this embodiment is exactly the same as the metal gasket shown in FIG. 2 except that the annular groove portions 6 and 8 are not formed. The overlapping description will be omitted. That is, the elastic metal plate 1 of this embodiment is a straight flat plate in which the annular groove is not formed. Similarly to the above, this elastic metal plate 1 also forms the folded-back portion 5 by warm working the bent portion.

FIG. 6 is a sectional view in the region between the cylinder bore holes showing another embodiment of the metal gasket. The metal gasket of this embodiment is composed of two elastic metal plates. The metal gasket is composed of an elastic metal plate 3 having a folded portion 5 and an elastic metal plate 21 having a bead 24 having a thickness larger than that of the elastic metal plate 3. That is, another elastic metal plate 21 is laminated on the elastic metal plate 3, and a bead 24 is formed along the cylinder bore hole 22 in the elastic metal plate 21, and the convex portion of the bead 24 and the elastic metal plate 3 are formed. It is located on the side facing the folded-back portion 5. The elastic metal plate 3 has a thickness of about 0.12 mm. The position of the cylinder bore hole 22 of the elastic metal plate 21 is completely aligned with the cylinder bore hole 2 of the elastic metal plate 3. In the folding unit 5, the same constituent elements as those in the first embodiment are designated by the same reference numerals, and there is no functional change, so duplicate description will be omitted. The fold-back portion 5 of the elastic metal plate 3 is fold-backed on the bead 24 side of the elastic metal plate 21, and when the metal gasket 20 is fastened, the fold-back portion 5 shares and supports the fastening force together with the bead 24, and the bead 24 is also supported. Prevents full compression of 24 and prevents settling of beads 24.

FIG. 7 is a sectional view in the region between the cylinder bore holes showing another embodiment of the metal gasket. This metal gasket is composed of three elastic metal plates. In the metal gasket, the tops of the beads 4 and 39 are symmetrically contacted between two bead substrates composed of elastic metal plates 31 and 35 having beads 34 and 37 formed along the parallel cylinder bore holes 32 and 42. It is a laminated metal gasket in which an intermediate plate composed of two elastic metal plates 3 and 38 is laminated. A step 41, which is less than the thickness of the elastic metal plate 3 which is the second intermediate plate, is formed along the cylinder bore hole 40 of the elastic metal plate 38 which is the first intermediate plate, and the stepped portion 41 forms an elastic surface on the convex surface. The metal plates 3 are laminated. The folded-back portion 5 of the elastic metal plate 3 is folded back toward the step 41 formed on the first intermediate plate, and the two intermediate plates at the portions where the tops of the beads 4 and 39 contact the periphery of the cylinder bore holes 2 and 40. The compensating portion is formed to be thicker than the total plate thickness. This compensator improves the surface pressure balance when tightening between opposing mounting surfaces, reduces stress fluctuations on the bead board and bending stress on the compensator, and prevents damage to the bead and compensator and a reduction in sealing effect. Then, it exerts a stable sealing effect even under severe conditions for metal gaskets such as diesel engines.

[0045]

The method of manufacturing a metal gasket according to the present invention has the following effects because it is configured as described above. That is, in the method for manufacturing the metal gasket, the bending process of the peripheral portion of the bore hole along the periphery of the bore hole formed in the elastic metal plate causes work hardening at the recrystallization temperature of the material of the elastic metal plate or less. Since it is performed in a difficult temperature range, it is possible to remove the effect of work hardening in the bending process of the bending part of the elastic metal plate, particularly the bending part, particularly the annular groove part that thins the bending part,
Bending can be easily performed with a small bending force without generating cracks, cracks, strains, and the like.

Regarding the hardness of the elastic metal plate material to be used, since bending is performed by warm working,
The hardness constraint is greatly relaxed. For example, even if the material has a high hardness of Hv300 or less before the folding process, the bending process can be performed even with a material having a high hardness. In this respect also, there is a restriction on the hardness of the elastic metal plate that can be adopted. It relaxes and expands the choice of metal materials that can be used. Further, in the bending process of the elastic metal plate, the width of the folded portion can be increased and the surface pressure at the portion of the cylinder bore can be appropriately dispersed.

Particularly, it is effective for a material such as SUS301, SUS304, etc. which precipitates martensite in cold working, and when the material is warm worked, precipitation of martensite can be prevented. The occurrence of work hardening can be avoided. Further, when forming an annular groove portion for thinning the elastic metal plate in the bent portion of the elastic metal plate and forming an annular hollow portion in the annular groove portion for bending, the thin portion is warm processed. As a result, the precipitation of martensite can be prevented and the occurrence of work hardening can be avoided, and the spring back during bending can be reduced, and the bent portion, that is, the folded portion can be formed with high accuracy. That is, by bending the elastic metal plate warmly, 180 ° bending can be easily performed.
Springback can be reduced.

Further, the original characteristics of the material can be utilized against the load fluctuation caused by the operation of the internal combustion engine acting on the folded edge portion, and the stress concentration due to work hardening can be avoided. Moreover, the metal gasket manufactured by this method for manufacturing a metal gasket does not cause cracks or cracks in the folded-back portion after long-term use, and can provide a highly durable metal gasket.

When the metal gasket is sandwiched between the opposing mounting surfaces of the internal combustion engine and tightened, the folded inner edges are not pressed by the folded edge portions having the gap of the folded portions, and the folded inner surface is elastic. It is not pressed against the metal plate body. Therefore, it is the annular region between the folded edge portion and the folded tip that the folded inner surface contacts at the folded portion, and the tightening force is shared and supported in this region. At the folded edge, the gap is not absorbed by tightening the metal gasket, and the gap is secured even after the tightening is completed. Therefore, the folded edge portion is not crushed and stress concentration does not occur, and the folded edge portion is not cracked or wrinkled when the metal gasket is tightened. Further, the load fluctuation accompanying the operation of the internal combustion engine also acts on the folded edge, but the stress fluctuation is absorbed and relaxed in the contacting annular region, and the folded edge does not cause cracks or wrinkles even during long-term use. .

Furthermore, when the periphery of the bore hole formed in the elastic metal plate is folded back, the region to be folded for the folding portion is formed thin in advance on the folding side of the elastic metal plate, and therefore the folding is performed. A small force is required for the folding, and the folding is a process in which the metallic material is gradually deformed rather than being folded completely 180 degrees.
Since the bending angle at the folded edge is relatively slow and does not cause sudden material deformation, there is no risk of cracks, etc., and in the case of so-called precompression in which the plate thickness is adjusted later by pressing etc., adjustment is required. Since it is easy to ensure the plate thickness adjustment accuracy and flatness even when the amount is large, the restrictions on the plate thickness that can be adopted are alleviated.

[Brief description of drawings]

FIG. 1 is a partial plan view showing an embodiment of a metal gasket manufactured by a method for manufacturing a metal gasket according to the present invention.

FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 showing an embodiment of the metal gasket manufactured according to the present invention.

FIG. 3 is an enlarged cross-sectional view showing a folded portion that is a part of FIG.

FIG. 4 is a partial development view of an elastic metal plate forming a folded portion shown in FIG.

FIG. 5 is a partial cross-sectional view showing between the cylinder bore holes of another embodiment of the metal gasket manufactured according to the present invention.

FIG. 6 is a partial cross-sectional view showing a gap between cylinder bores of another embodiment of the metal gasket manufactured according to the present invention.

FIG. 7 is a partial cross-sectional view showing between the cylinder bore holes of another embodiment of the metal gasket manufactured according to the present invention.

[Explanation of symbols]

 1,3,21,31,35 elastic metal plate 2,22,32,42 cylinder bore hole 4,24,34,37,39 bead 5 folded part 6,8 annular groove part 7,9 thin part 10 surface of elastic metal plate 11 Folded portion 13 Bore hole 15 Folded edge

Front page continued (72) Inventor Kunitoshi Inoue 248 Kano, Higashi-Osaka City, Osaka Prefecture Nippon Gasket Co., Ltd. (72) Inventor Kazuya Nakata 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (4)

[Claims] 1. A fold-back portion having a plurality of bore holes having an inner diameter smaller than that of a cylinder bore hole is formed in an elastic metal plate, and a portion around the bore hole of the elastic metal plate is bent to form a fold edge portion as a cylinder bore hole. In the method for manufacturing a metal gasket to be formed, the bending of the peripheral portion of the bore hole is performed at a temperature within a temperature range where work hardening is less likely to occur at a recrystallization temperature of the material of the elastic metal plate or less. Method for manufacturing a gasket made of steel. 2. A bent portion of the elastic metal plate is formed with an annular groove portion for thinning the elastic metal plate, the bent portion is bent by the annular groove portion, and the folded portion is formed, and along the cylinder bore hole of the elastic metal plate. The method for manufacturing a metal gasket according to claim 1, wherein a bead having a convex portion on the folded-back side is formed. 3. Another elastic metal plate is laminated on the elastic metal plate, a bead is formed on the other elastic metal plate along a cylinder bore hole, and a convex portion of the bead is formed by the folded portion of the elastic metal plate. 2. It is arranged on the side facing to.
The method for producing a metal gasket according to [4]. 4. A bead having a convex portion on the side of the folded portion is formed along the cylinder bore hole on the elastic metal plate, and a convex portion of the bead formed along the cylinder bore hole is formed on another elastic metal plate. The another elastic metal plate is laminated on the elastic metal plate so as to face the convex portion of the bead of the plate, and the elastic metal plate and the other elastic metal plate are further paired with another elastic metal plate. 2. The metal gasket according to claim 1, wherein each of the convex portions of the bead formed in the above is arranged in contact with each of the concave portions of each of the beads of the elastic metal plate and the another elastic metal plate. Production method.