JP2569381B2 - Metal gasket for cylinder head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a metal gasket for an engine cylinder head gasket.

(Prior Art) A metal gasket in which a bead surrounding a seal portion such as a cylinder bore, an oil hole and a water hole is formed in an elastic metal plate as a cylinder head gasket to be mounted on a joint surface between an engine cylinder head and a cylinder block. Used. In this metal gasket, as shown in cross-sectional views in FIGS. 6 (a) and 6 (b), a thin shim is provided inside the bead 22 surrounding the cylinder bore 21 of the metal gasket 20, that is, on the bore 21 side (FIG. 6 (a)). )) In some cases, a stopper consisting of 23 or a folded sheet 24 (FIG. 6 (b)) may be provided. Since the thickness of the gasket in the part where the stopper is provided is locally thickened, the surface pressure in this part is increased, the irregularity of the joint surface such as the cylinder head is compensated, and the sealing of the high-pressure gas in the cylinder bore is ensured. Has the effect of
Further, the effect of suppressing the amplitude of the deformation due to the repeated load applied to the bead 22 based on the internal pressure of the explosion in the combustion chamber of the engine and reducing the fatigue of the bead is expected.

(Problems to be Solved by the Invention) However, the rigid stopper composed of the shim or the folded portion described above has a small amount of elastic compression and restoration, and the curve (a) in the load-strain characteristic diagram of FIG. ), The load, i.e., the surface pressure, changes greatly with respect to the change in the amount of strain, i.e., the amount of compression. Therefore, when the cylinder head is lifted by the internal pressure of the explosion in the combustion chamber of the engine, the amount of lifting a is as small as several microns. Even if the amount is large, the load change amount b is large and the surface pressure is drastically reduced, or a gap may be formed between the joint surface of the cylinder head and the upper surface of the stopper, and the surface pressure may disappear. That is, it is difficult for the conventional rigid stopper to elastically follow the movement of the cylinder head due to the internal pressure of the engine.

Even if the surface pressure drops or disappears at the stopper, gas does not necessarily leak immediately because the bead surrounds the outside of the stopper.However, when a gasket is installed between the joint surfaces and bolted, Abrupt decrease or disappearance of the surface pressure at the stopper, which is the site where the sealing force is high, which causes the highest surface pressure, impairs the reliability and durability of the seal around the cylinder bore, and the joining of the cylinder head etc. When the surface has irregularities such as roughness and distortion, the defect becomes remarkable.

In view of the above, the present invention includes a stopper capable of following up a cylinder head lift due to an internal pressure of an explosion in a combustion chamber of an engine, and has a relatively small spring constant of a bead of an outer substrate, It is an object of the present invention to provide a metal gasket for a cylinder head which has a low risk of damaging a joint surface such as a head.

(Means for Solving the Problems) In order to achieve the above object, a metal gasket for a cylinder head of the present invention is made of an elastic metal plate and surrounds and seals a sealed portion such as a cylinder bore, a water hole, an oil hole, and the like. An outer substrate provided with a bead, and an intermediate substrate formed of an elastic metal plate and provided with an uneven bead that surrounds and seals the cylinder bore only around the cylinder bore at a position closer to the cylinder bore than the bead around the cylinder bore of the outer substrate. Wherein the spring constant of the concavo-convex bead of the intermediate substrate is larger than the spring constant of the bead around the cylinder bore of the outer substrate.

(Example) Hereinafter, an example of the present invention is described based on a drawing.

FIG. 1 shows a part of a plan view of an embodiment of the present invention, and FIG.
FIG. 3 and FIG. 3 are sectional views taken along line AA of FIG.
FIG. The gasket 1 of the present invention is formed by laminating outer substrates 2 and 2 'made of an elastic metal plate such as an iron plate and a stainless steel plate and an intermediate substrate 3 made of an elastic metal plate such as a stainless steel plate. 2 ′, the intermediate substrate 3 has the same shape as the joint surface of the cylinder head and the cylinder block of the engine, respectively.
The cylinder bore 4, oil hole 5, water hole 6, and bolt hole 7 are provided.
Cylinder bore 4, oil hole 5, water hole 6
Beads 8, 9 and 10 that surround and seal the parts to be sealed such as
Are formed. In the figure, the bead 8 surrounding the cylinder bore 4, the bead 9 surrounding the oil hole 5, and the bead 10 surrounding the water hole 6 are all formed as step beads having inclined surfaces. The shape may be an uneven bead having various cross-sectional shapes, for example, an uneven bead having an arc-shaped cross section as shown in FIG. However,
When the outer substrates 2 and 2 'are in direct contact with the joint surface such as a cylinder head, it is desirable that the bead provided on the outer substrate be a bead having a relatively small spring constant so as not to damage the joint surface. The step bead shown in FIG. Further, in the figure, the bead 8 surrounding the cylinder bore 4, the bead 9 surrounding the oil hole 5, and the bead 10 surrounding the water hole 9 show step beads having substantially the same shape. It goes without saying that the shape, height and width of each bead are appropriately selected so as to secure a suitable surface pressure.

On the other hand, the intermediate substrate 3 is provided with a bead 11 having concave and convex stripes as a stopper only around the cylinder bore 4 at a position closer to the cylinder bore than the bead around the cylinder bore of the outer substrate. This bead is formed such that its spring constant is larger than that of a bead 8 formed around the cylinder bore of the outer substrates 2 and 2 '. The magnitude of the spring constant of the bead 9 surrounding the oil hole 5 of the outer substrates 2 and 2 'and the bead 10 surrounding the water hole 6 usually does not exceed the magnitude of the spring constant of the bead 8 around the cylinder bore. Therefore, it can be said that the spring constant of the concave / convex bead of the stopper provided on the intermediate substrate 3 is larger than that of any of the beads of the outer substrates 2 and 2 '. As means for increasing the spring constant of the bead 11 of the intermediate substrate, the hardness or plate thickness of the intermediate substrate 3 is made larger than the hardness or plate thickness of the outer substrates 2 and 2 ′, or the width of the cross-sectional shape of the bead 11 is Means such as reducing the height or increasing the height can be appropriately selected.

For example, the outer substrates 2 and 2 'are laminated with a combination of a 0.2 mm thick stainless steel plate (SUS301-CSP) and the intermediate substrate 3 is a 0.3 to 0.5 mm thick stainless steel plate (SUS301-CSP). ', The height h of the stepped bead 8 (see FIG. 7) surrounding the cylinder bore 4 of FIG.
The height h of the bead 11 (see FIG. 8) of the arcuate cross section of the intermediate substrate 3 is 0.2 mm and the width W is 1.0 mm. As another example, the outer substrate and the intermediate substrate are made of the same material and thickness as the above example, and the bead 8 surrounding the cylinder bore of the outer plate is formed into an arc-shaped bead having a height of 0.3 mm and a width of 2.0 mm.
On the other hand, the bead 11 of the intermediate substrate is selected to have a height of 0.2 mm and a width of 1.0 mm.

The uneven strip bead 11 of the intermediate substrate may be a bead which has been crushed once and then reduced in height to increase or decrease the hardness. In the above description, a three-layer laminated metal plate gasket composed of two outer substrates and one intermediate substrate has been described. However, as shown in the sectional view of FIG. 3 'is the uneven bead 11
Are overlapped so that they are back to back with each other.
And 2 ', and a sub-plate (not shown) may be further provided outside the outer substrates 2 and 2'.

(Operation and Effect of the Invention) In the metal gasket for a cylinder head according to the present invention, a bead for surrounding and sealing a seal portion such as a cylinder bore, a water hole, an oil hole and the like is provided on the outer substrate, and the above-mentioned is provided only around the cylinder bore on the intermediate substrate. A stopper, which is an uneven bead surrounding the cylinder bore, is formed at a position closer to the cylinder bore than the bead around the cylinder bore of the outer substrate, and since the outer substrate and the intermediate substrate are laminated, the gasket is connected to the joint surface of the cylinder head. When mounted between the cylinder block and the joint surface of the cylinder block and tightened with bolts, the uneven bead or stopper provided only around the cylinder bore of the intermediate board exerts sufficient resistance against the pressing force of the cylinder head, and the cylinder bore Generates large surface pressure around. Moreover, the uneven bead has a load-strain characteristic as shown by a curve (b) in the load-strain characteristic diagram of FIG. 9, and the load change amount b, that is, the surface pressure change amount with respect to the strain change of the cylinder head lifting amount a is small. Since it is small, the decrease in surface pressure is small even when the cylinder head is lifted by the explosion internal pressure in the cylinder bore. That is, the stopper well follows the lifting of the cylinder head due to the internal pressure of the explosion in the combustion chamber of the engine, and can secure a sufficient surface pressure to seal the high-pressure gas in the bore.

In addition, around the cylinder bore of the gasket of the present invention, since the bead of the uneven strip having a large spring constant of the intermediate substrate is arranged in parallel with the bead around the cylinder bore of the outer substrate, and is located closer to the cylinder bore than the bead of the outer substrate, Even if the spring constant of the bead around the cylinder bore of the outer substrate is relatively small, good sealing performance can be obtained. The bead around the oil hole and the water hole of the outer group has a low internal pressure in these holes, so that a bead having a relatively small spring constant can provide a sufficient surface pressure to seal the oil hole and the water hole. After all, all the beads provided on the outer substrate may be beads having a relatively small spring constant, and therefore, there is little danger of damaging the joint surface such as the cylinder head. In addition, the seal surface pressure corresponding to the internal pressure around the cylinder bore, the water hole, and the oil hole can be generated in a well-balanced manner. Further, as shown in the above embodiment, the beads of the outer substrate can be all formed of step beads having inclined surfaces. In this case, since the step bead formed of the inclined surface has a larger elastic restoration amount than the uneven bead, the followability to the lifting of the cylinder head is improved.

Further, the uneven bead on the intermediate substrate, that is, the stopper, has an effect of suppressing the amplitude of deformation due to the repetitive load applied to the bead around the cylinder bore of the outer substrate based on the internal pressure of the explosion in the combustion chamber of the engine and reducing the bead fatigue.

[Brief description of the drawings]

FIG. 1 is a part of a plan view of an embodiment of a gasket for a cylinder head of the present invention, and FIGS. 2 and 3 are cross-sectional views taken along line AA and BB of FIG. It is. FIG. 4 is a sectional view showing another bead shape, and FIG. 5 is a sectional view showing another embodiment. 6 (a) and 6 (b) are cross-sectional views showing the surroundings of a cylinder bore of a conventional gasket, FIGS. 7 and 8 are cross-sectional views of a bead for explaining the height and width of the bead, and FIG. 9 is a shim or Load between stopper formed by folding and stopper formed by uneven bead-
FIG. 4 is a characteristic diagram illustrating distortion characteristics. (Signs) 2 and 2 ': outer substrate, 3: intermediate substrate, 4: cylinder bore, 5: oil hole, 6: water hole, 8, 9, and 10: bead, 11: uneven bead

Claims (2)

(57) [Claims] A cylinder bore, a water hole, an elastic metal plate,
An outer substrate provided with a bead surrounding and sealing around a portion to be sealed such as an oil hole, and an elastic metal plate surrounding the cylinder bore only around the cylinder bore at a position closer to the cylinder bore than the bead around the cylinder bore of the outer substrate. A cylinder characterized in that a spring constant of the uneven bead of the intermediate substrate is larger than a spring constant of a bead around a cylinder bore of the outer substrate. Metal gasket for head. 2. The metal gasket for a cylinder head according to claim 1, wherein the bead provided on the outer substrate is a step bead having an inclined surface.