JPH06147326A - Cylinder head gasket - Google Patents

Abstract

PURPOSE:To improve sealing performance and to lengthen the life of a cylinder head gasket formed by laminating a base plate wherein step-like beads are provided around cylinder bores on a base plate wherein projecting beads are provided around the cylinder bores. CONSTITUTION:A base plate 6 provided with step-like beads 8, 9, 10 respectively provided around cylinder bores 2, cooling water passage holes 3 and oil passage holes 4 and a base plate 7 wherein angled beads 12 are provided only around the cylinder bores are laminated to each other so that the step-like bead and the angled bead around the cylinder bore may be overlapped. A graphite covering layer wherein graphite sheets whose thicknesses are 50 to 200mum are stucked to each other by adhesive are provided on the outer front surface of the base plate 6 and both surfaces of the base plate 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine cylinder head gasket.

[0002]

BACKGROUND OF THE INVENTION In a cylinder head gasket of an engine, as shown in the sectional view of FIG.
Of the elastic metal plates 6 and 6'provided with stepped beads 8 and 9 around the water hole 3 and around the water hole 3 and a convex shape having a large spring constant around the cylinder bore 2 which is also made of the elastic metal plate. According to the applicant of the present application, Japanese Patent Application No. 2-312378 (Actual Development No. 4-) discloses that the cylinder head gasket is formed by laminating the substrate 7 provided with the chevron beads 12 so that the beads around the cylinder bore overlap each other. It is a proposal.

In this cylinder head gasket, the chevron bead 12 having a large spring constant exerts sufficient resistance against the pressing force of the cylinder head, and a large surface sufficient to seal the high pressure gas in the combustion chamber around the cylinder bore. In addition to generating pressure, the convex bead between the deck surface of the cylinder head and the cylinder block and the stepped bead inserted in the series have a large elastic restoration amount, so that the cylinder head due to the internal pressure of the explosion in the combustion chamber Follows up well. Further, since the convex bead around the cylinder bore functions as a stopper, the amplitude of deformation due to the alternating load applied to the bead based on the internal pressure of the explosion in the combustion chamber is suppressed and the fatigue of the bead is reduced.

Also in the above cylinder head gasket, a sealing material coating layer having a so-called micro-sealing function of absorbing and compensating for surface roughness and irregularities such as tool marks and scratches is laminated on both front and back surfaces of the cylinder head gasket. It is desirable to provide them on the facing surfaces of the metal plates. However, the conventional sealing material coating layer made of rubber or plastic has the following drawbacks.

In the above cylinder head gasket, the stepped bead of the substrate 6 and the chevron bead of the substrate 7 are overlapped with each other and are compressed and restored, so that the top of the chevron bead 12 and the stepped bead 8 in contact therewith are flat. The contact point with the part moves as the bead contracts. Therefore, unless the friction between the top of the convex bead and the flat portion of the stepped bead is sufficiently small, the chevron bead 1 is formed by the frictional force applied to the top of the convex bead in a direction parallel to the plane of the flat portion.
Although there is a risk that the bead is damaged due to the deformation of No. 2 in a distorted shape, it is difficult to obtain a sufficiently reduced friction coefficient with a conventional rubber or plastic sealing material coating layer.

Even if heat-resistant rubber or plastic is used, the heat resistance is limited because it is an organic material, and the sealing material coating layer is thermally deteriorated by the high temperature gas in the combustion chamber during long-term use, and the microseal Not only is there a risk that the above function will not be fulfilled, but also the above-mentioned friction will increase due to heat deterioration of the seal coating material, and smooth reduction and deformation of the bead may be impeded.

The thickness of the conventional sealing material coating layer made of rubber or plastic is relatively thin and is about 5 to 30 μm.
It is desirable to make the thickness of the seal coating layer thicker in order to fully exert the function of the microseal for a long period of time, but it is difficult to form a thick coating layer having a uniform thickness by one coating. There is also the drawback that multiple repeat coatings are required, which is costly.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a substrate having a stepped bead around the cylinder bore and a substrate having a convex bead around the cylinder bore are laminated. It is an object of the present invention to improve the sealing material coating layer provided on the cylinder head gasket formed as described above so as to have sufficiently low friction and to improve its heat resistance and microseal performance.

[0009]

A cylinder head gasket of the present invention which achieves the above object comprises a substrate made of an elastic metal and having stepped beads around the cylinder bore, and a spring made of an elastic metal plate around the cylinder bore. It is formed by laminating a substrate provided with a convex bead having a large constant, and has a thickness of 50 to 2 on at least one of the front and back surfaces of the entire laminated metal plate gasket and the facing surface of the laminated metal plates.
It is characterized in that a coating layer of a graphite sheet of 00 μm is provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings of the embodiments. 1 is a plan view of an embodiment of a cylinder head gasket of the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG. 3 is a sectional view of another embodiment of the present invention, which is a sectional view corresponding to the sectional view taken along the line AA of FIG.
FIG. 4 is a sectional view showing the periphery of a cylinder bore according to still another embodiment of the present invention. In the drawings, the same reference numerals indicate the same parts.

1 and 2, reference numeral 1 denotes a cylinder head gasket, which is provided with a cylinder bore 2, a cooling water passage hole 3, an oil passage hole 4 and a bolt insertion hole 5.
As shown in the cross-sectional view of FIG. 2, the cylinder head gasket 1 is formed by laminating a substrate 6 made of an elastic metal plate and a substrate 7 made of an elastic metal plate.

The substrate 6 has a stepped bead 8 around its cylinder bore 2, a stepped bead 9 around its cooling water passage hole 3, and a stepped bead 10 around its oil passage hole 4.
It has each. The step-like bead is a bead formed by an inclined surface a and flat surfaces b and c parallel to each other on both sides thereof, as shown in the cross-sectional explanatory view of FIG. Further, the substrate 6 is provided with a graphite coating layer 11 formed by adhering a graphite sheet with an adhesive as a sealing material coating layer on the outer surface in contact with the deck surface of the cylinder head which is the surface to be sealed.

The substrate 7 is provided with a convex bead having a large spring constant only around the cylinder bore 2, that is, a chevron bead 12 having a chevron cross section in the figure, and a graphite sheet as a sealing material coating layer is provided on both surfaces of the substrate 7. Graphite coating layers 13 and 13 ', which are bonded to each other with an adhesive, are provided.

The graphite sheet forming the above graphite coating layer is a sheet of graphite having a layered structure of a hexagonal net plane of carbon atoms, and is obtained, for example, by treating graphite with an oxidizing agent in the presence of sulfuric acid. By rapidly heating the oxidation-treated graphite at high temperature to decompose the inserts in the graphite layers and gasify it to expand graphite layers into expanded graphite, which is continuously pressed to form a sheet. Is what you get. In addition to the excellent heat resistance, chemical stability and low frictional properties inherent in graphite, it is also excellent in compressibility, resilience, stress relaxation and flexibility. Further, a uniform sheet having a thickness range of 50 to 200 μm can be easily obtained.

The substrate 6 and the substrate 7 described above are arranged such that the step-like beads 8 and the chevron-shaped beads 12 around the cylinder bore overlap each other, that is, the top of the chevron-shaped beads 12 is a flat surface on the upper side of the inclined surface of the step-beads 8. The cylinder head gasket 1 is formed so as to be in contact with or opposite to the lower surface side (flat surface b in FIG. 5). If the gasket 1 is mounted between the deck surfaces of the cylinder head and the cylinder block, the mountain-shaped beads 12 and the step-shaped beads 8 are inserted in series between the deck surfaces around the cylinder bore. When the tightening beads 8 and 12 are pressed, the sealing surface pressure generated by both beads is seriously affected, and a large sealing surface pressure sufficient to seal the gas in the combustion chamber around the cylinder bore is generated.

During operation of the engine, the mountain-shaped bead 12 and the step-shaped bead 8 are repeatedly compressed and restored due to the internal pressure of explosion in the combustion chamber. When the bead is contracted, the mountain-shaped bead 12 is compressed.
The contact point between the top of the bead 8 and the flat surface of the stepped bead 8 moves on the flat surface, but the friction between the top of the chevron bead 12 and the flat surface in contact therewith is sufficient due to the graphite coating layer covering the chevron bead. Since the frictional force acting in the direction along the flat surface hinders the reduction and deformation of the chevron bead or is deformed into a distorted shape, there is a risk that the chevron bead will be damaged during long-term use. There is no.

Further, in this case, when the substrate 6 is mounted so as to be on the cylinder head side, the stepped bead has a large elastic restoration amount, and therefore, even when the cylinder head is lifted by the explosion internal pressure of the combustion chamber. Follows well and improves the sealing performance of gas in the combustion chamber. Furthermore, since the mountain-shaped beads of the base plate 7 have a large spring constant, they act as a stopper against the compression and restoration of the beads during engine operation, and have the effect of suppressing the amplitude of the alternating load applied to the stepped beads.

The graphite coating layer 11 provided on the outer surface of the substrate 6 and the graphite coating layer 13 provided on the outer surface of the substrate 7 are rough such as tool marks and scratches on the sealed surface, that is, the deck surface of the cylinder head and the cylinder block. It plays the function of a microseal that absorbs and compensates for sheath irregularities,
Ensure good sealing between deck surfaces. Graphite coating layer 13 'provided on the surface of the substrate 7 in contact with the substrate 6
Similarly, the graphite coating layer 13 ′ has the function of a microseal that absorbs and compensates for the roughness and irregularity of the opposite side surface, and the graphite coating layer 13 ′ is a flat surface on the upper side of the top of the chevron bead 12 and the inclined surface of the stepped bead 8 as described above. Reduce friction with. Since the graphite coating layer made of a graphite sheet has excellent heat resistance, thermal degradation does not occur even if it is exposed to the high temperature of the engine for a long time.

Graphite coating layer 1 having the above functions
The thickness of the graphite sheets forming 1, 13 and 13 'is selected in the range of 50 to 200 μm. If the thickness of the graphite sheet is less than 50 μm, the function of the microseal cannot be sufficiently fulfilled for a long period of time, and if the thickness of the graphite sheet exceeds 200 μm, the wall thickness becomes too thick and easily causes fatigue, and the oil resistance decreases. This is because there is a tendency to The thickness of the substrates 6 and 7 is 0.1 to 0.3.
It is desirable to select in the range of mm.

The embodiment shown in FIG. 3 has a three-layer laminated structure in which a substrate 6 ′ similar to the substrate 6 is added to the cylinder head gasket of FIG. 2 described above, and the substrate 6 and the substrate 6 ′ are formed. The substrates 7 are sandwiched in the middle, and they are laminated back to back. In this embodiment, three beads including a stepped bead, a chevron bead, and a stepped bead are inserted in series around the cylinder bore between the surfaces to be sealed. The configuration and operation other than this point are the same as those described above with reference to FIG.

The embodiment shown in FIG. 4 is a gasket having a four-layer structure in which a substrate 7 ′ similar to the substrate 7 is added to the cylinder head gasket of FIG. The substrate 7 and the substrate 7 ′ are back to back, and the substrate 6 and the substrate 6 ′ are stacked back to back with the substrate 7 and the substrate 7 ′ sandwiched therebetween. In this embodiment, a stepped bead-a chevron bead-is provided around the cylinder bore between the surfaces to be sealed.
Yamagata beads-Stepped beads and 4 beads are inserted in the series.

[0022]

The cylinder head gasket of the present invention has the structure and operation as described above and has a thickness of 50 to 200.
Even if the graphite coating layer formed by the graphite sheet of μm is exposed to the high temperature gas in the combustion chamber of the engine, the graphite coating layer does not undergo thermal deterioration and maintains a sufficient microseal function for a long period of time. Further, the graphite coating is provided around the cylinder bores of the laminated substrates in the present invention, and sufficiently reduces the friction between the mountain-shaped beads and the step-shaped beads that are overlapped with each other to facilitate compression and restoration of the beads. .
Therefore, the present invention greatly contributes to extending the life of the cylinder head gasket.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of a cylinder head gasket of the present invention.

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

FIG. 3 is a sectional view of another embodiment of the present invention.

FIG. 4 is a sectional view around a cylinder bore according to still another embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a stepped bead.

FIG. 6 is a cross-sectional view of a conventional cylinder head gasket.

[Explanation of symbols]

 2 Cylinder bores 6, 6 ', 7 and 7' Substrates 8, 9 and 10 Stepped beads 12 Angled beads 11, 13 and 13 'Graphite coating layer

Claims (1)

[Claims] 1. A substrate, which is made of an elastic metal plate and is provided with a stepped bead around a cylinder bore, and a substrate, which is also made of an elastic metal plate, is provided with a convex bead having a large spring constant around the cylinder bore. A cylinder head gasket, wherein a coating layer of a graphite sheet having a thickness of 50 to 200 μm is provided on both front and back surfaces of the entire laminated metal plate gasket and at least one of opposing surfaces of the laminated metal plates.