GB2121123A

GB2121123A - Improvements in or relating to metallic gaskets

Info

Publication number: GB2121123A
Application number: GB08300186A
Authority: GB
Inventors: Nobuo Yoshino
Original assignee: Japan Metal Gasket Co Ltd
Current assignee: Japan Metal Gasket Co Ltd
Priority date: 1982-05-17
Filing date: 1983-01-05
Publication date: 1983-12-14
Also published as: JPS58200860A; IT8319589A0; GB8300186D0; JPS6354944B2; IT8319589A1; KR840003337A; DE3306759A1; FR2526912A1; IT1161901B

Abstract

A metallic gasket comprises a resilient metallic base plate (4) formed with a sealing bead (16) and a respective sub-plate (6) laminated to each major surface of the base plate (4), the sub-plates being formed of metallic plate less hard than the base plate. Preferably, a sealing material (8) is attached to at least one surface of each of the sub-plates (6) to prevent damage of the joint area and effectively to compensate for irregular conditions in the joint area. In one embodiment, sealing beads of different curvature or inclination are formed on the base plate (4) so that different urging forces are exerted thereon to prevent leakage. Further intermediate plates may be provided between the base plate and the sub- plates. Also each sub-plate may be plated with a layer to prevent rust and flow of the sealing material. <IMAGE>

Description

SPECIFICATION Improvements in or relating to metallic gaskets This invention relates to improvements in or relating to metallic gaskets.

There has previously been proposed a metallic gasket comprising a resilient metallic base plate having a convex or stepped bead formed thereon in order effectively to seal a joint area between, for example, a cylinder head and a cylinder block. A sub-plate is laminated to each major surface of the base plate and, in use, a seal line is formed with respect to a deck surface or joint area between a cylinder head and a cylinder block as a result of the tightening of the cylinder head bolts to provide a close contact between the laminate and the mating surfaces thereby attaining a superior sealing effect. However, such a metallic gasket cannot compensate for irregular conditions in the joint area, such as heat distortion, tool marks and flaws.Nor does it permit easy sliding of the sealing bead when compressed by the tightening of the bolts so that the bead cannot form an ideal seal line and thus leaks may occur. Furthermore, the pressure applied to the joint area by the seal line portion formed by the bead differs greatly between portions of the joint area and is nonuniform, thus causing gaps to be formed, so that it is not possible to attain an effective seal over the whole bead.

It is an object of the present invention to provide a metallic gasket which overcomes or at least mitigates the disadvantages of the above previously proposed metallic gasket.

According to the present invention, there is provided a gasket comprising a resilient metallic base plate formed with a sealing bead, a respective sub-plate formed of metallic plate less hard than the base plate being laminated to each of the major surfaces of the base plate.

In order that the present invention may be readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: FIGURE 1 is a partially cut-away plan view of a first metallic gasket embodying the invention; FIGURE 2 is an enlarged sectional view taken along line Il-Il in Figure 1; FIGURE 3 is a further enlarged sectional view of the region indicated by the arrow III in Figure 2; FIGURE 4 is a sectional view of part of the metallic gasket of Figure 1 with the gasket interposed between a cylinder head and a cylinder block; FIGURE 5 is a part-sectional view of part of a second metallic gasket embodying the invention; FIGURE 6 is a sectional view of part of a third metal gasket embodying the invention; and FIGURE 7 is a sectional view of part of a fourth metal gasket embodying the invention.

Referring now to the drawings, Figures 1 to 4, illustrate a first metallic gasket 2 embodying the invention. The metallic gasket 2 comprises a base plate 4 in the form of a hard resilient metallic plate, and two sub-plates 6 each in the form of a metallic plate that is softer than the base plate.

The base plate 4 is sandwiched between the two sub-plates 6 to form a composite laminated plate.

As shown in Figure 4, the metallic gasket 2 is used for providing a sealing effect in a joint area 14 between a cylinder head 10 and a cylinder block 12.

The base plate 4 comprises a thin metallic plate which has resistance to heat and to corrosion and is also resilient: for example, the plate may be formed of stainless steel, carbon steel, tool steel or the like. A respective convex (or stepped) bead 1 6 is formed on the base plate 4 to provide a seal against each cylinder bore 18 or oil path 20. The base plate 4 is formed so as to have a shape matching the shape of the joint area 14.

Preferably, the hardness of the base plate 4 is in the range of HV300 to 450 so that an ideal bead 1 6 may be formed in the joint area 14.

The sub-plates 6 to be laminated to either surface of the base plate 4 are formed so as to have the same shape as the base plate and to have a thickness in the range of 0.1 5 to 0.3 mm to provide a thin metallic gasket. The sub-plates 6 are made of a material which does not soften at temperatures of 400 C or lower and which has a hardness in the range of HV70 to 150, sufficiently lower than that of the base plate 4; for example, an iron plate is suitable. Thus, the sub-plates 6 should be capable of completely compensating for irregular conditions in the joint area 14 and of keeping the joint area 1 4 undamaged.

A respective sealing material 8 is attached to each surface of each of the sub-plates 6. A material having heat resistance and flexibility such as a coating material is used as the sealing material. Preferably the sealing material 8 provides a seal thickness not larger than 50 ,um.

The provision of the sealing material 8 allows for compensation for irregularities in the joint area 1 4 such as tool marks and flaws and provides a micro-seal. Also, the sliding of the metallic gasket 2 with respect to the joint area 14 becomes smooth enough to avoid occurrence of a distortion in the lateral direction, that is the direction parallel to the joint area 14, of the bead 16, thus making it possible to exhibit an ideal sealing effect. The numeral 22 designates a bolt hole.

The metallic gasket 2 operates as follows. As shown in Figure 4, the metallic gasket 2 is inserted in the joint area 14 between the cylinder head 10 and the cylinder block 12 and is then compressed as bolts inserted through the bolt holes 22 are tightened, with the result that a top 24 of the bead 1 6 becomes a gently curved surface and the bolt tightening force causes the top of the bead to exert a pressure on the face of the cylinder head 10 to provide a seal between the face of the cylinder head and the gasket. The bolt tightening force also causes end portions 20-1 and 20-2 of the bead 1 6 to exert a pressure on the face of the cylinder block 1 2 via the sub-plate 6, providing a seal between the face of the cylinder block and the gasket.Thus, the metallic gasket 2 is brought into close contact with the mating surfaces of the joint area 14, thereby preventing leaks.

As described above, a sub-plate 6 made of a material softer than the base plate 4 is attached to each face of the base plate 4, so that, when the top 24 of the bead 1 6 urges the sub-plate 6 against the face of the cylinder head 1 0, the subplate 6 permits a uniform pressure to be exerted along the seal line in the joint area 14, while attaining an ideal distribution of pressure on the face to produce good sealing effect.

The sealing material 8 may be attached to only one side of each sub-plate 6, namely the side which, in use, is adjacent the face of the cylinder head 10 or the cylinder block 12. This simpler construction also enables effective compensation for irregular conditions such as heat distortion, tool marks and flaws in the surface of the cylinder head 10 and a good seal. Again, the sealing material 8 also functions to permit sliding and improve fitting with respect to the joint area 14.

The same can also be said with regard to the face or deck surface of the cylinder block 12.

Referring now to Figure 5, in a second metallic gasket embodying the invention, an intermediate plate 28 is interposed between the base plate 4 and each of the sub-plates 6. The provision of the intermediate plate 28 is desirable if the gasket is to be used in a diesel engine. Because diesel engines are operated at high compression ratios, it is necessary to provide a strong seal and therefore to provide a bead which will produce a strong urging force. In this connection, if only two subplates are used, the sealing line pressure of the bead becomes too strong, thus, making it difficult to exert a smooth and continuous pressure on the faces in the joint area based on an ideal, smooth seal line; that is, it is impossible to obtain a good sealing effect. To avoid this inconvenience, the intermediate plate 28 is interposed between the base plate 4 and each of the sub-plates 6.The intermediate plate 28 also functions to adjust the spacing between the cylinder head 10 and the cylinder block 12, and the compression ratio is adjustable by changing the thickness of the intermediate plate 28. The intermediate plate 28 may be made of the same material as the subplates 6. Where the intermediate plate 28 is intended to serve only to adjust the compression ratio, it may be made of any material.

With the gasket shown in Figure 5, there is no likelihood of leakage even in engines with high compression ratios, and adjustment of the compression ratio of such engines can be made without difficulty.

Although, the sealing material 8 may be provided on both surfaces of each sub-plate 6, a constructional simplification is attained in the gasket shown in Figure 5 by providing the sealing material 8 only on the surface of each of the subplates 6 which, in use mates with the face of the cylinder head 10 or the cylinder block 12.

As shown in Figure 6, each sub-plate 6 may be plated with layer 30 to prevent rust and the flow of the sealing material, to permit sliding and to provide a good fit with respect to the base plate 4 or intermediate plate 28 and consequently a good seal.

In order to prevent a possible leak of a high pressure gas via the bead formed around the cylinder bore 18, the bead 1 6 may be formed in a two-step manner, one step being strong and the other weak, as shown in Figure 7. More specifically, an inner peripheral bead 1 6-1 extends toward the sub-plate 6 which in use is adjacent the cylinder bore side and is shaped so as to provide a high resilient force, while an outer peripheral bead 1 6-2 is formed outside the inner peripheral bead 16-1 and is shaped so as to give a lower resilient force than the bead 1 6-1. The inner and outer beads preferably have different degrees of curvature.For example, the inner peripheral bead 1 6-1 may be formed so as to have a smaller radius of curvature than of the outer peripheral bead 16-2. With such an arrangement, the force produced by the tightening of bolts in the bolt holes 22 causes the inner peripheral bead 1 6-1 to exert a high pressure via the associated sub-plate 6, while the outer peripheral bead 1 6-2 exerts a relatively small facial pressure via the associated sub-plate so that the pressure exerted by the tightening force is optimally distributed.This construction is further advantageous in that the leakage of gas from the cylinder bore 1 8 can be prevented almost completely by the inner peripheral bead 1 6-1, and any leakage of thus de-energized gas via the bead 1 6-1 will be prevented by the outer peripheral bead 16-2.

A metallic gasket embodying the invention is thus capable of compensating for irregularity in a joint area and allowing an optimal planar movement of the bead, when compressed, with an optimal distribution of facial pressure on the seal line so as to attain an effective seal.

Moreover, a metallic gasket embodying the invention is capable of forming a continuous seal line with respect to a joint area under an averaged non-intermittent pressure by means of the subplates made of a material softer than the base plate which directly contact the mating surfaces, thereby efficiently compensating for irregular conditions of the joint area such as heat distortion, tool marks and flaws. A sliding motion of a bead formed on the base plate is allowed by this construction so as to assure a good seal, preventing leakage such as blow by and thereby exhibiting a superior sealing performance.

Further, a metallic gasket embodying the invention does not damage a joint area and consequently the sealing effect thereof does not undergo deterioration over a long period of use, thereby assuring a superior engine performance.

Claims

1. A gasket comprising a resilient metallic base plate formed with a sealing bead, a respective sub-plate formed of metallic plate less hard than the base plate being laminated to each of the major surfaces of the base plate.

2. A gasket according to claim 1 , wherein the sealing bead of the base plate is of convex shape.

3. A gasket according to claim 1 or 2, wherein the base is formed with two sealing beads of different curvature.

4. A gasket according to claim 1, 2 or 3, wherein a respective intermediate plate interposed between the base plate and each subplate.

5. A gasket according to claim 1, 2, 3 or 4 wherein one major surface of each sub-plate is plated.

6. A gasket according to claim 1, 2, 3 or 4, wherein both major surfaces of each sub-plate are plated.

7. A gasket according to any preceding claim wherein a sealing material is attached to one major surface of each sub-plate.

8. A gasket according to claim 7, wherein the major surface of each sub-plate remote from the base plate has a sealing material attached thereto.

9. A gasket according to any one of claims 1 to 6, wherein a sealing material is attached to both major surfaces of each sub-plate.

10. A metallic gasket substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 to 4, or Figure 5, or Figure 6 or Figure 7 of the accompanying drawings.

11. Any novel feature or combination of features described herein.