JPH05340477A - Manufacture of gasket made of metal - Google Patents

Abstract

PURPOSE:To provide a manufacturing method for a gasket made of a metal which prevents the occurrence of crevices, cracks, and strains by processing and hardening a bent part by bending processing through which beads are formed in a resilient metallic sheet. CONSTITUTION:When bending processing is applied on a resilient metallic sheet 8 along a cylinder bore 9A to form beads 10, bending processing of the beads 10 is effected at temperature within a temperature range in which processing hardening is hard to occur at the re-crystal temperature or less of the material of the resilient metallic sheet 8. This prevents the occurrence of processing hardening to a bent part. Thus, the generation of a residual stress, i.e., a residual strain, is reduced at the bent part of the bead 10, a spring back amount is reduced to a minimum, and crevices are prevented from occurring to improve durability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cylinder internal combustion engine for sealing between opposing mounting surfaces of a cylinder head and a cylinder block, or a side surface of a cylinder head having an exhaust manifold end of a mounting flange and an exhaust outlet. The present invention relates to a method for manufacturing a metal gasket used for sealing between opposing mounting surfaces of and.

[0002]

2. Description of the Related Art Conventionally, a metal gasket made of a metal material has been used to seal between opposing mounting surfaces of a structural member of an internal combustion engine such as a cylinder head and a cylinder block. By the way, recent internal combustion engines are required to have a high output and a 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 alloy material having a small specific gravity instead of a casting. is there. Although the aluminum material is lightweight, it has low rigidity, which may cause inconvenience when tightening the metal gasket and operating the internal combustion engine. That is, 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, so that the structure in which the rigidity is reduced When the opposing mounting surfaces between the materials are tightened with the tightening bolts through the single-plate metal gasket, the opposing mounting surfaces are likely to become 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.

Further, 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 repeatedly increases and decreases. Also, since the temperature change of the metal gasket greatly changes depending on the operation and stop 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 is settled or cracked to deteriorate the sealing performance. There is something to do.

Further, Japanese Patent Application No. 3-
The metal gasket disclosed in No. 214129 is a bead formed along the cylinder bore hole and radially outwardly spaced from the peripheral edge of the cylinder bore hole, and the circumference of the cylinder bore hole is on the convex side of the bead and inside the bead. A first elastic metal plate having a folded portion located at
And a second elastic metal plate having a bead that contacts the bead of the elastic metal plate.

[0005] Further, Japanese Patent Application No. 3-
The metal gasket disclosed in No. 232449 has a pair of elastic metal plates having a bead formed of convex portions facing each other along the outside of a plurality of cylinder bore holes aligned with each other, and between the pair of first elastic metal plates. There is provided an intermediate elastic metal plate which is laminated on one of the elastic metal plates and has a folded-back portion which is formed by bending a peripheral portion of the cylinder bore hole aligned with the cylinder bore hole outward in the radial direction of the cylinder bore hole and then heat-treating the bent portion.

Further, in Japanese Patent Laid-Open No. 4-95668,
A metal gasket for a manifold is disclosed. The metal gasket for manifold is sandwiched between an end face of a mounting flange of an exhaust manifold and a side face of a cylinder head having an exhaust outlet, and at least two bead plates each having a flat plate or a bead portion are laminated in a non-fixed state. The bead portion is made of a thin metal plate, and the ratio R / t of the bending radius R of the bead portion to the plate thickness t of the bead plate is set to 7 to 15. The bead portion is based on the case where the bending radius R is 0.5 mm. When the stress and the surface pressure generated in the are analyzed, the stress can be made lower than the reference value, and the increase of the surface pressure from the reference value can be suppressed within a predetermined range.

By the way, if the elastic metal plate is cold-worked, the following phenomenon occurs. 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. In this recovery process, the density and electric resistance of the metal alloy also change and residual stress is removed, but the decrease in strength is small. Low temperature annealing of metals 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. When the annealing is further continued after the completion of the recrystallization, the crystal grains gradually increase in size, and the mechanical properties of the polycrystalline material are sensitively influenced by the crystal grain size.

[0008] Polycrystalline materials take a specific preferential orientation when strongly subjected to 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. When crystal grains having a specific crystal orientation are given priority, anisotropy is brought about in mechanical or physical properties. Since recrystallization is a rate 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 in absolute temperature, and T _R ≈ (0. Three
In to 0.5) T _M, represented by the approximately equal That Niari equal relationship between T _R and (0.3~0.5) T _M.

Generally, regarding recrystallization of metal, when a crystal that has been plastically strained by cold working or the like is heated, the internal stress is reduced from the original crystal grains following the process of reducing the internal stress. A new crystal nucleus without strain is generated, and as the number increases, each nucleus gradually grows and replaces the original crystal grain. The recrystallization temperature is the temperature at which recrystallization occurs. 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 in which the crystal grain becomes large by heating the polycrystalline material to a high temperature.

[0010]

However, in the conventional metal gasket, in order to reduce the spring back of the elastic metal plate, the bead is formed and the load is applied to the upper and lower sides of the mold by using the mold. , The elastic metal plate is pressed and held for processing. Therefore, the processing time of the bead forming process for the elastic metal plate becomes long,
This is a factor of reduced productivity or increased cost.
In addition, the amount of springback generated in the elastic metal plate changes due to variations in the hardness of the material, so the shapes of the beads formed on the elastic metal plate also vary. The variation in the shape of the beads formed on the elastic metal plate reduces the sealing performance. Therefore, it is necessary to manufacture a mold in consideration of springback generated in the elastic metal plate, which causes a cost increase.

Further, when a bead is formed on an elastic metal plate made of a hard material, residual strain or residual stress is generated in a portion having a high degree of bead formation. The residual stress generated in the elastic metal plate causes fatigue, cracks, and the like when the metal gasket is used for a long time, which adversely affects the durability of the metal gasket.

Further, the above-mentioned metal gasket is basically an elastic metal plate having a bead that becomes a convex portion along the completed cylinder bore hole or the gas flow hole. Such an elastic metal plate is used for processing the bead. Since it undergoes severe stress changes at times, work hardening etc. occurs in the bead forming part and damage such as cracks and cracks occurs in the bead forming part, or even though heat treatment is applied, after tightening between the opposing mounting surfaces Since it is exposed to repeated stress corresponding to the combustion cycle for a long time, damage such as cracks and cracks is likely to occur in the bead forming portion formed along the cylinder bore hole or the gas flow hole.

Regarding the mechanism of generation of processed martensite, S which is a metastable austenitic stainless steel.
The steel types of US301 and SUS304 cause 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 guideline for this is Md of 30 points. This indicates the temperature at which 50% of martensite precipitates when subjected to a strain of 30%.
The Md30 point is on the higher temperature side than the 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 a chemical component by a coefficient, and when SUS301 and 304 are compared,
SUS301 has a higher Md30 point than SUS304 and is a steel type that is more prone to martensite. In other words, it indicates that SUS301 is easier to work and harden 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, and when a bead is formed by bending an elastic metal plate, the temperature range determined by the material of the elastic metal plate and the processing history of the material. While warming, by performing a bead bending process on the elastic metal plate, to prevent cracks, cracks, strain, etc. from occurring in the bead forming portion of the elastic metal plate, and the plate thickness, hardness and hardness of the elastic metal plate. Relaxing restrictions on materials on elongation characteristics, preventing the occurrence of cracks, cracks, strains, etc. at the bead forming part, ensuring stable sealing properties, high quality and low cost, improved strength and high reliability A method of manufacturing a metal gasket is provided.

[0015]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention provides a method of manufacturing a metal gasket, which comprises manufacturing an elastic metal plate having a plurality of cylinder bore holes and a bead formed of a convex portion and a concave portion along the circumference of the cylinder bore holes, wherein the cylinder bore hole of the elastic metal plate is The method for producing a metal gasket is characterized in that the bending process for forming the bead in the peripheral portion is performed at a temperature within a temperature range in which work hardening is less likely to occur at a recrystallization temperature of the material of the elastic metal plate or less. 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 of manufacturing a metal gasket, a cylinder bore hole which is aligned with the cylinder bore hole of the elastic metal plate, a bent portion formed by bending a bent portion along the cylinder bore hole, and an outer side of the bent portion. And another elastic metal plate having a bead protruding toward the folded-back portion is laminated on the elastic metal plate so that the convex portions of the beads are in contact with each other.

Further, in this method for manufacturing a metal gasket, an intermediate plate is interposed between the elastic metal plate and the another elastic metal plate.

Further, in this method for manufacturing a metal gasket, the intermediate plate is a first intermediate plate having a folded portion formed by bending a bent portion along a cylinder bore hole, and the folded back portion in a direction away from the folded portion. The second intermediate plate is formed with a step having a thickness equal to or less than the thickness of the first intermediate plate of the section.

Further, in this method for manufacturing a metal gasket, another elastic metal plate having a cylinder bore hole aligned with the elastic metal plate and a bead formed along the cylinder bore hole may be used. The convex portion of the bead of the other elastic metal plate is arranged in contact with the concave portion of the above.

Alternatively, according to the present invention, at least two elastic metal plates sandwiched between an exhaust manifold having a gas inlet opening and a cylinder head having a gas outlet opening to form a gas passage opening and a bead are provided. In the method for manufacturing a laminated metal gasket, a temperature at which work hardening is less likely to occur at a bending process for forming the bead in the peripheral portion of the gas flow hole of the elastic metal plate at a recrystallization temperature of the material of the elastic metal plate or less. The present invention relates to a method for producing a metal gasket, which is performed at a temperature within the range.

[0021]

The method of manufacturing a metal gasket according to the present invention is constructed as described above and operates as follows. That is, in the method for manufacturing the metal gasket, the bead bending formed along the cylinder bore hole or the gas flow port 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 warm temperature range that is difficult to perform, beading can be easily performed without causing cracks, cracks, strains, and the like. Therefore, since the elastic metal plate itself is pressed while maintaining a warm state, it is possible to reduce the springback and residual stress that have been conventionally generated after the processing as much as possible, and also adversely affect the strength of the material. Never.

Further, since the elastic metal plate is beaded in a warm state, the beading can be performed with a small pressing force, and the amount of deformation after pressing is small, so that the bead shape is formed with high accuracy. be able to. Furthermore, since the residual strain is reduced by beading the elastic metal plate, the amount of settling is small even after long-term use, and high sealing performance can be maintained.

In the metal gasket manufactured by this manufacturing method, the beads are well formed along the periphery of the opening of the cylinder bore hole or the gas flow port. Therefore, when the metal gasket is tightened and pressed, the bead Depending on the function, an annular seal portion can be formed in the pressed state of the metal gasket to improve the sealing property.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing a metal gasket according to the present invention will be described below with reference to the drawings. 1 is a plan view showing an embodiment of a metal gasket manufactured by the method for manufacturing a metal gasket according to the present invention, and FIG.
3 is an enlarged view of the metal gasket in the region between the cylinder bore holes of FIG. 3, FIG. 3 is a cross-sectional view illustrating an embodiment of the elastic metal plate manufactured by the manufacturing method according to the present invention, and FIG. 4 is an elastic metal manufactured by the manufacturing method according to the present invention. Sectional drawing explaining another Example which abutted the convex part of the bead of a metal plate, FIG. 5 is sectional drawing in the line AA of FIG. 1, and FIG. 6 is sectional drawing in the line BB of FIG. Is.

The method of manufacturing a metal gasket according to the present invention is characterized in that the bead 10 is formed on the elastic metal plate 8 as shown in FIGS. 3 and 4, and a plurality of cylinder bore holes 9A are formed. , 9B (hereinafter referred to as reference numeral 9), a bead 10 formed of a convex portion and a concave portion along the circumference of the cylinder bore hole 9 is beaded or bent to produce the elastic metallic plate 8. Is something
Particularly, the bending process for forming the bead 10 on the peripheral portion of the cylinder bore hole 9 on the elastic metal plate 8 is performed at a temperature within a temperature range in which work hardening is less likely to occur below the recrystallization temperature of the material of the elastic metal plate 8. It is a feature.

In this method of manufacturing a metal gasket, warm working means working in a temperature range in which work hardening is less likely to occur below the recrystallization temperature of the elastic metal plate 8. In this warm working, bending is performed. It is necessary that the elastic metal plate 8 to be processed reaches that temperature, and it does not make sense to reach that temperature after the bending process is completed. Therefore, in order to warm work the elastic metal plate 8, for example, when bending is performed with a mold, the elastic metal plate 8 is sandwiched between the molds, and the mold and the elastic metal plate are heated to heat the elastic metal plate. After the temperature of the plate 8 rises to a warm temperature range, the elastic metal plate 8
It is necessary to bend the beads 10.

In the method of manufacturing the metal gasket, the elastic metal plate 8 is bent at a warm temperature within an appropriate temperature range so that the elastic metal plate 8 is not work-hardened and can be easily bent. In addition, even a relatively hard material can be bent, and a metal gasket having excellent durability can be produced without causing cracks, breaks, cracks, distortions, and the like.

As the material of the elastic metal plate 8 in the metal gasket, when bending is performed, a material having a relatively high hardness and a material having a hardness of Hv300 or more are effective. For example, martensite is precipitated. As a material that is hardened by hardening, among cold-rolled stainless steel sheets, SUS301, SUS304 and the like among austenitic materials. Further, it can be applied to Inconel 718, Inconel 625, Herons alloy 214, etc., but these materials do not precipitate martensite.

In this method for manufacturing a metal gasket, the lower limit temperature of the warm working temperature range is set to 50 ° C. from the high temperature point where the martensite precipitation of the material occurs, as the base of the warm temperature range during bending. High temperature range (M _d +5
It is preferable that the temperature is set to 0 ° C.) and the upper limit temperature is set to a temperature range that is about 10% lower than the upper limit temperature of the temperature range that does not affect the structure and strength of the material.

For example, SUS301 has a hardness of Hv30.
0-500 materials, processing temperature range 100-200 ℃
Is. SUS304 has a hardness of Hv300 to 450 and a processing temperature range of 100 to 200 ° C. Further, SUS631 has a hardness of Hv300 to 500 and a processing temperature range of 100 to 260 ° C. The hardness of Inconel 718 and Inconel 625 is Hv3.
00-450 material, processing temperature range is 100-600
℃. Furthermore, Herons Alloy 214 has a hardness of Hv.
300-450 materials, processing temperature range is 100-70
It is 0 ° C.

The metal gaskets shown in FIGS. 1 and 5 are
The first elastic metal plate and the second elastic metal plate are single plates, and are used, for example, to seal opposing mounting surfaces of a cylinder head and a cylinder block in a six-cylinder engine. For example, the first elastic metal plate located on the cylinder block side will be described as the lower bead plate 1, and the second elastic metal plate located on the cylinder head side will be described as the upper bead plate 8. However, each elastic metal plate is limited to this arrangement. However, the reverse arrangement is also possible.

The elastic metal plate 1 and the elastic metal plate 8 in this metal gasket are provided with cylinder bore holes 2A, 2B, 2C ... and 9A, 9B, corresponding to the cylinder bores formed in the multi-cylinder, that is, the cylinder block. 9C are formed (the cylinder bore holes are collectively referred to by reference numerals 2 and 9).
The cylinder bore holes 2 and 9 are formed at the same position and with the same size. Further, the elastic metal plate 1 and the elastic metal plate 8 are respectively provided with a plurality of water holes 3 for passing cooling water, oil holes for passing oil, oil return holes, knock holes, rivet holes and the like.

In the illustrated example, the diameter of the cylinder bore is 8
It is 5 mm, and the minimum distance between the cylinder bore holes is about 6 mm. The thickness t of the elastic metal plate 1 and the elastic metal plate 8 is 0.12 mm, but it is preferable that the thickness t is a value within the range of 0.1 mm to 0.20 mm. Also, although not shown,
Rubber (for example, fluororubber), resin, etc. having heat resistance and oil resistance to both front and back surfaces of the metal gasket, that is, all surfaces of the elastic metal plate 1 excluding the inside of the folded portion and the entire surface of the elastic metal plate 8. Non-metallic material with a thickness of, for example, 10μ
By applying a coating of approximately 50 μm (preferably 25 μm), it is possible to avoid the metal-to-metal contact state with the cylinder head and the cylinder block, and to secure the corrosion resistance, durability and strength as a gasket. .. Further, even if the machined surface of the metal gasket has irregularities, the non-metallic material can cover the irregularities and perform a sufficient sealing function.

FIG. 5 is a cross section of a metal gasket obtained by cutting the boundary between adjacent cylinder bore holes 2A, 2B and 9A, 9B by a line connecting the centers of the cylinder bore holes 2A, 2B and 9A, 9B. , A cross section between the cylinder bore holes 2 and 9 is shown, but it goes without saying that a similar cross-sectional structure is also provided at the boundary portion between the other adjacent cylinder bore holes 2 and 9. In addition, in FIG.
The cross section of the metal gasket cut along the line connecting the cylinder bore holes 2A and 9A and the end or edge of the metal gasket is shown, but the cylinder bore hole 2 at the opposite position is shown.
B and 9B also have the same cross-sectional structure with the edge portion, and are not limited to these and also have the similar cross-sectional structure around the cylinder bore holes 2 and 9 other than between the cylinder bore holes 2 and 9. Of course.

As can be seen from these drawings, a bead 4 having a chevron cross section is formed so as to surround a peripheral portion of the elastic metal plate 1 of the metal gasket in the vicinity of the cylinder bore hole 2 concentrically with the cylinder bore hole 2 and in an annular shape. (Numeral 4 is a general term for beads). In the illustrated example, the adjacent cylinder bore holes 2
The distance L ₁ therebetween is, for example, about 6.00 mm. The bead 4 around the cylinder bore hole 2A and the bead 4 around the adjacent cylinder bore hole 2B are the cylinder bore hole 2
They overlap at the approaching points of A and 2B. That is, the beads 4 meet in the area between the cylinder bores to form one bead. However, the beads 4 adjacent to each other may be arranged with a slight gap therebetween without overlapping each other. The width L ₂ of the bead 4 when viewed in the radial direction is about 2.5 m.
In a region having a width of 1.0 mm and having a width of 1.0 mm, which is the center region, the tops of the convex portions are formed substantially flat. The height of the bead 4 is 0.27 mm. In addition, folded portions 5A and 5B are formed on the peripheral edge of the cylinder bore hole 2 formed in the elastic metal plate 1 so as not to overlap the bead 4 on the convex side of the bead 4 and on the radially inner side of the bead 4. (Reference numeral 5 is a general term for the folded portion). The width L ₄ of the folded-back portion 5 is, for example, about 1.2 mm.

In order to adjust the thickness of the folded-back portion 5 formed on the elastic metal plate 1, a predetermined compressive force is applied to the folded-back portion 5 to form the preset thickness 2t ₁ (= 2t-α). To do. Then, around the cylinder bore holes except between the cylinder bore holes 2, the plate thickness is reduced by β, which is a value larger than α, 2t ₂ (= 2t−β). That is, the cylinder head has a lower rigidity than the cylinder block, and in a multi-cylinder engine, a portion between adjacent cylinder bores 2 is likely to be most distorted due to load fluctuations in the combustion cycle of the internal combustion engine during the explosion stroke and expansion stroke. By the way. Therefore, since the sealing function of the metal gasket is most likely to deteriorate in this portion, the folded portion 5
5, the thickness 2t _{1 of the} portion located between the cylinder bore holes 2 as shown in FIG. 5 is the thickness 2t ₂ of the portion other than between the cylinder bore holes 2 as shown in FIG. 6 (where α <β) The structure is such that the shape is thicker than that.

In this metal gasket, the elastic metal plate 1 includes a cylinder bore hole 2 aligned with the cylinder bore hole 9 of the elastic metal plate 8, a bent portion 5 formed by bending a bent portion along the cylinder bore hole 2, and the bent portion. It has a bead 4 which projects along the outside of 5 toward the folded-back portion 5. The elastic metal plate 1 and the elastic metal plate 8 shown in FIG. 5 are laminated so that the convex portions of the beads 4 and 10 are in contact with each other.

Another metal gasket manufactured by the method for manufacturing a metal gasket according to the present invention is shown in FIG. With regard to the parts in this embodiment, the same parts as those of the embodiment shown in FIG. 6 are designated by the same reference numerals, and the duplicated description will be omitted. In this metal gasket, intermediate plates 6 and 16 are interposed between an elastic metal plate 1 and another elastic metal plate 8, and the intermediate plates 6 and 16 are the cylinder bore holes 2
A first intermediate plate 16 having a folded-back portion 5 formed by bending the bent portion along the direction and a step 7 having a thickness equal to or less than the plate thickness of the first intermediate plate 16 of the folded-back portion 5A are formed in a direction away from the folded-back portion 5A. It is composed of the second intermediate plate 6. In this metal gasket, the first adjustment plate
Since the intermediate plate 16 does not have a bead portion, the folded-back portion 5A is laminated on the second intermediate plate 6 without any gap. Therefore,
A gap S is formed between the elastic metal plate 8 and the folded portion 5A of the first intermediate plate 16.

Another metal gasket manufactured by the method for manufacturing a metal gasket according to the present invention is shown in FIG. With regard to the parts in this embodiment, the same parts as those of the embodiment shown in FIG. 6 are designated by the same reference numerals, and the duplicated description will be omitted. This metal gasket includes a cylinder bore hole 14 aligned with the elastic metal plate 1 and the cylinder bore hole 1
Elastic metal plate 11 with beads 12 formed along
The elastic metal plate 11 in the concave portion of the bead 2A of the elastic metal plate 1.
The beads 12 are stacked with no gap in contact with each other. The elastic metal plate 1 is formed in a state in which the elastic metal plate 10 has a bead shape. Elastic metal plate 1
The folded portion 5A can be expected to have a reinforcing effect on the elastic metal plate 10, and the bead complete compression prevention on the folded portion 5A and the irregular absorption effect of the opposing mounting surface at the time of tightening are the same as those in the above-mentioned respective embodiments.

Next, still another embodiment of the method for manufacturing a metal gasket according to the present invention will be described with reference to FIGS. 9 and 10. 9 is a plan view showing an embodiment of a metal gasket for manifold manufactured by the method for manufacturing a metal gasket according to the present invention, and FIG. 10 is a line CC in FIG.
FIG. This metal gasket manufacturing method has exactly the same configuration and function except that the object to be used is different from that of the metal gasket manufacturing method shown in FIG. Only the points will be described below.

In the embodiment of the method for manufacturing the metal gasket according to the present invention, the metal gasket is sandwiched between the exhaust manifold having the gas inlet opening and the cylinder head having the gas outlet opening to form the gas circulation port 20 and the bead 25. A metal gasket for a manifold (hereinafter, referred to as a metal gasket) in which at least two elastic metal plates 21 are laminated is manufactured, and a bead 25 is formed in a peripheral portion of the gas flow hole 20 of the elastic metal plate 21. Bending process for elastic metal plate 2
It is characterized in that it is carried out at a temperature within the temperature range in which work hardening is less likely to occur at the recrystallization temperature of the material No. 1 or less.

The metal gasket is sandwiched between the end face of the mounting flange of the exhaust manifold and the side face of the cylinder head where the exhaust discharge port is opened, and is tightened with a tightening bolt or the like. Various types of metal gaskets for manifolds are used, and a mounting flange for an exhaust manifold having a side surface of a cylinder head of a multi-cylinder engine having an exhaust discharge opening and branch pipes having the same number as the exhaust discharge openings. It is clamped and fixed between the end surface and the end surface, and as shown in the figure, the airtightness of the contact surface between the side surface of the cylinder head and the end surface of the exhaust manifold is maintained around the three exhaust discharge ports. The exhaust gas is sealed so as not to leak.

This metal gasket is sandwiched between the mounting flange end face of the exhaust manifold and the cylinder head side face where the exhaust discharge port is opened, and the elastic metal plate 21 having the flat plate 23 and at least two or more beads 25 is not stopped. It is laminated in a worn state. Further, this metal gasket is composed of elastic metal plates 21 on both outer sides and an inner metal thin plate, that is, an intermediate plate 23 sandwiched between them. The elastic metal plates 21 and the intermediate plate 23 on both outer sides have the same number of gas circulation holes 20 and 27 as the exhaust gas discharge ports formed in the cylinder head of the multi-cylinder engine. The elastic metal plates 21 on both outer sides are
In the free state before tightening, as shown in FIG. 8, around the gas flow hole 20, a part thereof is gradually separated from the intermediate plate 23 toward the gas flow hole, and a taper portion 24. Following the part 24, there is a bead 25 parallel to the intermediate plate 23. The part that moves away from the intermediate plate 23, that is, the part that transitions from the main flat part of the elastic metal plate 21 to the tapered part 24 and the part that transitions from the tapered part 24 to the bead 25 parallel to the intermediate plate 23 is bent by the radius R. It is formed by processing. The elastic metal plate 21 is formed in a state having a spring function, that is, elastically deformable in order to absorb deformation such as large thermal deformation in the mounting flange of the exhaust manifold.

This metal gasket is sandwiched between the cylinder head and the exhaust manifold, and when the cylinder head and the exhaust manifold are tightened by screwing a tightening tool such as a bolt into the mounting hole 22, the metal gasket is sandwiched between the two. The beads 25 on both sides of the elastic metal plate 21 contact the contact surfaces of the cylinder head and the exhaust manifold to form a seal portion to prevent leakage of combustion gas at the periphery of the gas flow holes 20, 27. can do.

[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 work for forming a bead in the peripheral portion of the cylinder bore hole or the gas flow hole of the elastic metal plate is less likely to cause work hardening at the recrystallization temperature of the material of the elastic metal plate or less. Since it is carried out in a warm temperature range, it is possible to remove the influence of work hardening of the bending portion by bending the bending portion of the elastic metal plate, without causing cracks, cracks, strains, etc., and easily. Bead bending can be performed with a small bending force.

Regarding the hardness of the material of the elastic metal plate to be used, since the bending process is performed by warm working, the constraint of hardness is relaxed, and even a material having high hardness can be bent. Also in this respect, the restriction on the hardness of the elastic metal plate that can be adopted is relaxed, and the range of choices of usable metal materials is expanded. Further, when the hardness is Hv450 to Hv500, a crack or the like is likely to occur.

Particularly, it is effective for a material such as SUS301 and SUS304 which precipitates martensite in cold working. When the material is warm worked, precipitation of martensite can be prevented. Occurrence of work hardening can be avoided. Further, when the bead bending portion of the elastic metal plate is bent, the springback amount at the time of bending can be reduced, and the shape of the bending portion, that is, the bead can be formed with high accuracy.

Further, since the elastic metal plate is beaded in a warm state, the beading can be performed with a small pressing force, and the amount of deformation after pressing is small, so that the bead shape is formed with high accuracy. be able to. Furthermore, the beading of the elastic metal plate reduces residual strain, which makes it possible to provide a highly durable metal gasket with a small amount of fatigue for long-term use, and to maintain high sealing performance for a long period of time. You can The metal gasket produced by this production method forms a good bead without residual stress, that is, residual strain, along the circumference of the cylinder bore hole or the opening of the gas flow port, so when this metal gasket is tightened and pressed, By the function of the bead, a good annular seal portion can be formed in the pressed state of the metal gasket, and the sealability can be greatly improved.

[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.

2 is an enlarged plan view of the space between the cylinder bore holes in FIG. 1. FIG.

FIG. 3 is a cross-sectional view illustrating an example of an elastic metal plate manufactured by the method for manufacturing a metal gasket according to the present invention.

FIG. 4 is a cross-sectional view illustrating another embodiment of the elastic metal plate manufactured by the method for manufacturing a metal gasket according to the present invention.

5 is a cross-sectional view showing an example of the metal gasket taken along the line AA in FIG.

6 is a cross-sectional view showing an example of the metal gasket taken along the line BB in FIG.

7 is a cross-sectional view showing another embodiment of the metal gasket of a portion corresponding to the line BB of FIG.

8 is a cross-sectional view showing another embodiment of the metal gasket of a portion corresponding to the line BB in FIG.

FIG. 9 is a plan view showing an example of a manifold metal gasket manufactured by the method for manufacturing a metal gasket according to the present invention.

10 is a cross-sectional view taken along the line C-C in FIG.

[Explanation of reference numerals] 1, 6, 8, 11, 16 Elastic metal plate 2, 9, 14, 15 Cylinder bore hole 4, 10, 12 Bead 5 Folded portion 7 Step 13 Folded edge portion 20, 27 Gas flow port 21 Elastic metal Board 25 beads

Claims (6)

[Claims] 1. A method of manufacturing a metal gasket, comprising: a plurality of cylinder bore holes; and an elastic metal plate having a bead formed of a convex portion and a concave portion along the circumference of the cylinder bore hole. A method of manufacturing a metal gasket, wherein the bending process for forming the bead in the peripheral portion is performed at a temperature within a temperature range in which work hardening is less likely to occur at a recrystallization temperature of the material of the elastic metal plate or less. 2. A cylinder bore hole which is aligned with the cylinder bore hole of the elastic metal plate, a fold portion formed by bending a fold portion along the cylinder bore hole, and a bead protruding toward the fold portion side along the outside of the fold portion. 2. The method for manufacturing a metal gasket according to claim 1, wherein another elastic metal plate having the above is laminated in a state in which the convex portions of the beads are in contact with each other on the elastic metal plate. 3. The method of manufacturing a metal gasket according to claim 2, wherein an intermediate plate is interposed between the elastic metal plate and the another elastic metal plate. 4. The intermediate plate is a first intermediate plate having a folded-back portion formed by bending a bent portion along a cylinder bore hole, and a plate thickness of the first intermediate plate of the folded-back portion in a direction away from the folded-back portion. The method for manufacturing a metal gasket according to claim 3, wherein the second intermediate plate has the following steps. 5. Another elastic metal plate having a cylinder bore hole aligned with the elastic metal plate and a bead formed along the cylinder bore hole is provided in the recess of the bead of the elastic metal plate. The method for producing a metal gasket according to claim 1, wherein the plate is arranged in a state where the convex portions of the beads are in contact with each other. 6. A metal body in which at least two elastic metal plates sandwiched between an exhaust manifold having a gas inlet opening and a cylinder head having a gas outlet opening are laminated to form a gas passage opening and a bead. In the method for manufacturing a gasket, a bending process for forming the bead in the peripheral portion of the gas flow hole of the elastic metal plate is performed in a temperature range in which work hardening is less likely to occur at a recrystallization temperature of the material of the elastic metal plate or less. A method for producing a metal gasket, which is characterized in that