GB2182731A

GB2182731A - Cylinder head gasket

Info

Publication number: GB2182731A
Application number: GB08527825A
Authority: GB
Inventors: Terence Peter Nicholson
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-11-12
Filing date: 1985-11-12
Publication date: 1987-05-20
Also published as: GB8527825D0

Abstract

A cylinder head gasket comprised of at least one layer of sheet metal characterised in that around oil and water flow apertures (B, C, D and E) therein the thickness of each face of the gasket is reduced so as to form recesses which are occupied by rings (R) made of high temperature resisting non-metallic flexible material which initially stand proud of the adjacent face parts of the gasket. Additionally, around cylinder bore openings in the gasket one or both of the outward faces of the gasket may be formed with circular ridges concentric with the cylinder bore openings. The cylinder head gaskets are particularly but not exclusively intended for use with diesel engines whereof the cylinder blocks are provided with cylinder linears. <IMAGE>

Description

SPECIFICATION Improvements relating to cylinder head gaskets This invention relates to cylinder head gaskets for internal combustion engines and particularly, but not exclusively, diesel engines.

In the past when diesel engines were naturally aspirated the designed structures of the cylinder heads and cylinder blocks were in the main quite adequate.

The advent of turbo-charging and now charge cooling has greatly increased power output resulting in substantially higher gas pressures and temperatures from the same engine overall dimensions. As a consequence the original designs of blocks and heads have in many instances proved to be quite inadequate most especially when endeavouring to obtain a perfect gas, water and oil seal between the head and the block.

To find a solution to this problem larger bolts with greatly increased torque loadings have been concentrated around the cylinders, very often at the expense of sealing satisfactorily the cooling water and oil systems.

The present invention has been devised with the general object of providing a cylinder head gasket which will perfectly seal around all of the cylinder bore, oil and water flow openings of a cylinder block and cylinder head in a high efficiency internal combustion engine.

According to the invention, a cylinder head gasket comprised of at least one layer of sheet metal is characterised in that around the oil and water flow apertures therein the thickness of each face of the gasket is reduced so as to form recesses which are occupied by rings made of high temperature resisting nonmetallic flexible material which initially stand proud of the adjacent face parts of the gasket. A suitable material for these rings is that, which is known under the Registered Trade Mark "Velbestos" 250.

The recesses may be machined in both faces of a single relatively thick metal plate.

Alternatively and more economically the gasket may comprise three thinner metal sheets superposed on one another and secured together, the recesses for receiving the non-metallic flexible material being created by cutting, in the two outer sheets, apertures which are larger than the corresponding oil and water flow apertures in the central sheet.

The two outer metal sheets are preferably of greater thickness than the centre sheet.

In each instance the cylinder bore openings of the gasket will preferably be concentrically surrounded by ridges formed on one or both faces of the gasket. Alternatively both faces of the gasket in the region of the cylinder bore openings may be plane with the joint in these regions supplemented by the use of separate metal sealing rings of C-shaped radial profile.

The invention is hereinafter described in detail by reference to the accompanying drawings which illustrate some preferred embodiments, and in which: Fig. 1 is a plan view of a cylinder head gasket for a two cylinder diesel engine cylinder block; Figs. 2A and 2B are cross-sections of alternative embodiments on line X-X of Fig. 1; Figs 3A, 3B and 3C are cross-sections on line Y-Y of Fig. 1 showing alternative embodiments as fitted over a cylinder block; and Fig. 4 is a horizontal cross-section to show the shape of a cylinder block outer wall on one side.

Referring now to Fig. 1, the gasket there shown has a pair of cylinder bore apertures A, four rocker box seepage apertures B, eight water transfer apertures C, one high pressure oil aperture D, two oil drainage apertures B, eight securing stud apertures F and two locating dowel apertures G.

Surrounding each of the apertures B to E inclusive is a flat relatively thick ring R made of a high temperature resistant resilient material such as that which contains asbestos and a nitrile and is known under the Registered Trade Mark "Velbestos" 250.

This material has the following characteristics: Maximum working temperature = 260"C Compression 20% Recovery 40% minimum (Specification SAE J9OB) F124100-M16 The gasket may comprise, as shown in Fig.

2A, a single stainless steel or other metal plate 1 having a thickness of the order of 2mm except around the apertures B to E inclusive where its opposite faces are machined down to a residual thickness of about 3mm to provide recesses for receiving the flat "Velbestos" sealing rings R which initially stand proud of the plate 1 and are adhesively secured to the residual part 1 a. Alternatively, as indicated in Fig. 2B, the recesses for the sealing rings R may be defined by the projecting parts of 0.3mm thickness central sheet 3 which is bonded by brazing or welding to two identical outer metal sheets 2 and 4 each of about 0.9 mm thickness. The rings R are adhesively secured to these respective sheets.

It has been found that the rings R ensure particularly effective sealing of the apertures B, C and D where, otherwise due to the necessary high loading on the gasket in order to seal the cylinder bores effectively and the cellular nature of the cylinder head and cylinder block, it would be virtually impossible to achieve an efficient seal.

A difficult problem arises with the sealing of the oil drainage apertures E because of the lack of clamping bolts between the dowei holes G which allows the cylinder head to lift very slightly under full load, this being further exaggerated because of the corrugated formation of the outer wall 5 of the cylinder block as indicated in Fig. 4 which makes ittimpossi- ble to achieve a seal along the wall unless a very flexible material is used even though it is only unpressurised oil which is draining back to the sump.

For achieving a satisfactory seal between the cylinder head, the cylinder block and the margin of an associated cylinder liner a different technique is required because: 1. Substantially higher gas pressures arise due to Turbocharging and Intercooling; 2. Much higher temperatures are developed for the same reasons.

3. Due to the structural limitations of the liner it is most difficult to obtain the high seating loads required to establish a perfect seal.

In the gaskets constructed as so far described three cylinder bore sealing expedients are feasible and are illustrated in Figs. 3A, 3B and 3C which each show the relationship between the gasket shown in section, and adjacent parts of a cylinder block 6 and a cylinder liner 7 both indicated in chain dashed lines.

Thus Fig. 3A shows a three layer gasket whereof each of the two thicker outer sheets, 2, 4 (c.f. Fig. 2b) has its outer surface formed with several ridges which concentrically surround the cylinder bore openings and respectively engage flat surfaces of the cylinder head (not shown) and of the cylinder block 6 and cylinder liner 7. The resulting corrugations form a labyrinth seal with only about one third of the seating stress required of a flat ring or plate.

Fig. 3B shows a variation in which only the cylinder-head engaging sheet 2 is corrugated and the plane outer face of the other sheet 4 engages an inverted V-shaped profile circular rib 7A on the cylinder liner 7 which bites into the gasket when clamping pressure is applied.

Only the corrugations on the sheet 2 then function to seal the joint between the cylinder head and the gasket.

The expedients illustrated in Figs. 3A and 3B function equally well irrespective of whether the gasket is comprised of a single relatively thick metal plate or of three superposed sheets fixed together.

However some manufacturers of very large power output engines are extremely concerned regarding the excessive loads to which cylinder liners are being subjected.

This problem has been resolved by using the general concept of this gasket with the omission of the sealing area around the cylinder bores as shown in Fig. 3C. In this latter arrangement each cylinder bore aperture of the gasket has been increased in diameter to that of the counter bored recess of the cylinder block 6. Further, the outside diameter of the rim of the liner has been machined away so that a recess is created for a low load, hollow somewhat C-shaped radial suction sealing ring 8, for instance that disclosed in British Patent 1360951 to be fitted.

Claims

1. A cylinder head gasket comprised of at least one layer of sheet metal characterised in that around oil and water flow openings therein the thickness of each face of the gasket is reduced so as to form recesses which are occupied by rings made of high temperature resisting non-metallic flexible material which initially stand proud of the adjacent face parts of the gasket.

2. A cylinder head gasket in accordance with Claim 1 wherein the recesses are machined in both faces of a single relatively thick metal plate.

3. A cylinder head gasket in accordance with Claim 1 comprised of three metal sheets superposed on one another and secured together, the recesses for receiving the nonmetallic flexible material being created by forming in the two outer sheets apertures which are larger than the corresponding oil and water flow apertures in the central sheet.

4. A cylinder head gasket in accordance with Claim 3 wherein the two outer metal sheets are of greater thickness than the centre sheet.

5. A cylinder head gasket in accordance with any of Claims 1 to 4 wherein the rings are made of an asbestos-nitrile material known under the registered trade mark "Velbestos".

6. A cylinder head gasket in accordance with any of Claims 1 to 5 in which around cylinder bore openings in the gasket at least one of the outward faces of the gasket is formed with circular ridges which concentrically surround those openings.

7. A cylinder head gasket in accordance with Claim 6 in which both faces of the gasket are formed with said ridges.

8. A cylinder head gasket in accordance with Claim 6 in which only that face of the gasket which is intended to engage the cylinder head is formed with said ridges.

9. A cylinder head gasket in accordance with any of Claims 1 to 5 when used in combination with one or more metal sealing rings of C-shaped radial cross-section surrounding the cylinder bore apertures.

10. A cylinder head gasket substantially as hereinbefore described with reference to Fig. 1 and any of Figs. 2A, 2B, 3A, 3B, 3C and 4 of the accompanying drawings.