GB1576998A

GB1576998A - Cylinder head gasket for an internal-combustion engine

Info

Publication number: GB1576998A
Application number: GB8313/78A
Authority: GB
Original assignee: Elring Dichtungswerke GmbH
Current assignee: Elring Dichtungswerke GmbH
Priority date: 1977-04-02
Filing date: 1978-03-02
Publication date: 1980-10-15
Also published as: ES468472A1; FR2385905A1; IT7820893A0; DE2714776C2; IT1093209B; FR2385905B1; DE2714776A1

Description

(54) CYLINDER HEAD GASKET FOR AN INTERNAL-COMBUSTION ENGINE (71) We, ELRING DICHTUNG SWERKE GESELLSCHAFT MIT BES CRANKTER HAFTUNG (formerly INDUVA INDUSTIEVERWALTUGS GESELLSCHAFT MIT BESCHRANK TER HAFTUNG personally liable Partner of ELRING DICHTUNGSWERKE K.G.,)a Germany Company of Höhenstrasse 24, D-7012 Fellbach, Germany, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to cylinder head gaskets for internal-combustion engines.

The sealing of reciprocating-piston engines with cylinder liners braced freely against the cylinder head and with cooling medium chambers between the outside diameter of the cylinder liners and the surrounding cylinder block is rendered difficult by a clamping of the cylinder head gasket over less than its total surface. Unavoidable relative movements between the sealing surfaces of cylinder block or cylinder liners and the cylinder head, and radial changes of position of the cylinder liners have the effect of imposing a load upon the cylinder head gasket at the surfaces under pressure. Customary gasket constructions with combined metallic and soft material elements are frequently unequal to this loading, which is characteristic of reciprocating-piston engines with freely placed cylinder liners (so-called "wet cylinder liners").In these cases the gasket becomes increasingly deformed with the running time so that bulges occur at surfaces not subject to pressure in the direction towards the chambers filled e.g., with cooling medium. This disadvantageous phenomenon, which is known to the expert, stands in direct relationship to elastic and permanent deformations at pressurised surface regions of the gasket, in which the most important influence originates from the surroundings of the combustion chambers. Engines frequently begin to leak because these changes in the gasket have assumed unacceptable dimensions. In the extreme case, the described disadvantageous relative movements between cylinder liner, externall wall and cylinder head lead to destruction of the gasket, which is expressed as cracks and deformations.Serious faults in the cooling water circuit and in the sealing of liquids and gases are the consequences of this.

Attempts have already been made to deal with the problems described by a two-part gasket in which a ring on the cylinder tube or cylinder liner is responsible for the gas sealing and an outer frame is supposed to effect the liquid sealing. The disadvantage of this known construction of a cylinder head gasket is the absence of a gasket sheet in the region exposed to water, so that it is impossible to control the cooling water circuit with this known cylinder head gasket. Another disadvantage of this known cylinder head gasket is that its composite nature is unfavourable for the assembly of engines, and more particularly results in waste of time. Due to the co-ordination in height between the radially inner and the radially outer sealing parts of the cylinder head gasket, a relatively high price of the overall gasket is inevitable.

Another attempt at solving the problems described above was made by constructing the cylinder head gasket throughout totally of metal. But such known gaskets frequently find a limit to their application due to their deficient adaptibility, poor elastic behaviour and considerable difficulties in liquid sealing.

Attempts have likewise been made with known combined metal and soft material gaskets, to adapt them to the particular mode of stress described. In this case continuous relatively thick sheet metal supports (substantially of the shape of the gasket) were provided at the combustion chambers with metal framings (optionally with additional metal inlays) and covered on both sides with layers of soft material which extended as far as the outside diameter of the metal framings of the combustion chamber holes. These known gaskets were characterised by a construction which consisted of, principally, metallic layers at the combution chamber and of a metallic core and adapatable soft material in the so-called "hinterland". In particular cases, facing layers metallic on one or on both sides were also provided.Limits to the stiffening of the metallic core layer are naturally imposed by the admissible gasket thickness. The unavoidable relative movements in any case stress the gasket structure in the boundary surface region, while here again damage may occur as a function of running time. The metallic construction at the combustion chamber and the combined metal/soft material construction in the "hinterland" raises additional problems of coordination in the distribution of thicknesses and pressures.

The present invention seeks to provide a cylinder head gasket which does not suffer from disadvantageous deformations and premature destruction under loads such as those described above, but which has an optimum sealing capacity of the gasket with regard to the cooling water and to the combustion gases.

According to the present invention there is provided a cylinder head gasket for an internal-combustion engine made of a soft gasket material or a soft gasket material with metallic reinforcements having at least one cooling medium passage, at least one fixing passage and at least one combustion chamber passage arranged to be located in the region of a combustion chamber of the engine, a metallic edge framing surrounding at least the or each combustion chamber passage, the or each framing being of U-shaped cross-section and engaging the gasket material, the gasket material located between flanks of the or each framing having an internal annular portion the material bond of which to the surrounding gasket material is interrupted at least over the major part of its outer circumference, the internal annular portion and the surrounding gasket material being made of the same material or same combustion of materials.

By the said interruptions of material according to the invention between the part of the cylinder head gasket lying directly in the region of the combustion chamber and the so-called "hinterland" of the cylinder head gasket, the unavoidable relative movements between the cylinder liner and the surrounding cylinder block may be prevented from exerting a detrimental influence upon the entire cylinder head gasket. In fact, due to the separation of the cylinder head gasket material according to the invention, any introduction of forces from the region of the cylinder liner into the gasket material is prevented.In order nevertheless to ensure the desired one-piece construction of the overall cylinder head gasket, according to the present invention, the or each framing may be prolonged so that it projects beyond the parting space into the surrounding gasket material and thus connects the internal annular portion to the surrounding gasket material. In this contect therefore, preferably, the inside diameter of the or each combustion chamber passage is greater than an inside diameter of a liner and the outside diameter of the inernal annular portion is dimensioned so that it is not subject to pressure outside the region of the liner and that the outside diameter of the or each framing is greater than the inside diameter of the surrounding gasket material.

In one embodiment, the internal annular portion of the gasket material has an uninterrupted annular parting space between itself and the surrounding gasket material. However it may also be advantageous from production considerations if the internal annular portion of the gasket material has an annular parting space between itself and the surrounding gasket material which is inter rutted at spaced apart points. Connecting webs of material between the internal annular portion and the surrounding gasket material which are initially present, are then severed in the course of the service life of the engine by the conditions of force and movement initially described, so that here again ultimately the finally desired uninterrupted annular parting space between the internal annular portion and the surrounding region of the gasket results.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1, shows, in partial vertical section, an engine block with a cylinder liner, a cylinder head and a cylinder head gasket according to the present invention; Figure 2 illustrates one embodiment of a cylinder head gasket according to the present invention in section the section being taken along the line II-II in Figure 3; Figure 3 is a section of the cylinder head gasket of Figure 2 taken along the line III III; Figures 4 and 5 show, in section, further embodiments of cylinder head gaskets according to the present invention; and Figure 6 is a section taken along the line VI-VI in Figure 5.

In order to demonstrate the nub of the invention, Figure 1 shows schematically a type of reciprocating-piston engine in which the problems initially described arise very acutely. An engine block 10 of the internal combustion engine has a cylinder liner 12 anchored at 11. An annular cavity 13, through which a flow of a liquid cooling medium passes, extends radially between the cylinder liner 12 and the wall of the engine block 10. The cylinder liner 12 is thus a socalled "wet" cylinder liner. The cylinder head of the internal-combustion engine is indicated by the reference numeral 15. A cylinder head gasket 16 is arranged between the engine block 10 and the cylinder liner 12 on the one hand and the cylinder head 15 on the other hand.Since the cylinder head 15 is secured to the engine block 10 in customarv manner by screw connections (not shown) the cylinder head gasket 16 is subject to a comparitively high compressive stress.

The cylinder head gasket 16 has, in the region of a combustion chamber, a passage 17, the edge of which is surrounded by a combustion chamber edge framing 18 of U-shaped cross-section. In its remaining regions the cylinder head gasket 16 has -as known- an optionally metallically reinforced soft material 19. Besides the passage 17 in the region of the combustion chamber, the cylinder head gasket 16 also has further passages, one of which is shown in Figure 1, and designated by the reference numeral 20. The passage 20 is a cooling medium passage through which a stream of cooling liquid passes from the cavity 13 into a space 21 in the cylinder head 15.Obviously the cylinder head gasket 16 may also have further cooling medium passages besides the passage 20 shown, in which case they should be coordinated to the particular conditions (volume of heat to be dissipated, and cooling medium throughput rate as a function thereof etc.). Further passages (not shown) in the cylinder head gasket 16 serve in known manner for passing fixing screws to secure the head 15 to the engine block 10.

It is self-evident that the features described hereinbefore and illustrated in Figure 1 are not valid solely for a reciprocating piston engine with a single cylinder, but are also appropriate to reciprocating-piston engines with a plurality of cylinders, e.g. -as customary in motor vehicle engines 4 or 6 cylinders.

Figure 1 shows clearly that the cylinder liner 12 is firmly anchored only at 11 in the engine block 10, but otherwise receives no radial bracing over its total height: it is merely pressurised ultimately at its top end by the cylinder head 15 through the intermediary of the cylinder head gasket 16. Now when the engine is in service, due to the above-described design conditions, relative movements occur in the top region of the cylinder liner 12 between the latter and the surrounding engine block 10, which are indi cated in simplified form by a double arrow 22. This dictates, in addition to the customary mechanical and thermic loads, a strong radial stressing of the cylinder head gasket 16, which in normal cylinder head gaskets leads to the deformations and cracks thoroughly described initially.The cylinder head gasket 16 illustrated schematically in Figure 1 is not a conventional cylinder head gasket but, on the contrary, is a cylinder head gasket according to the present invention which exhibits features which may be seen in detail and in Figures 2 to 8. Of the engine components shown in Figure 1, apart from the cylinder head gasket only the top end of the cylinder liner 12 is shown in each of Figures 2 to 8 for reasons of simplicity. The cylinder head lining itself is also illustrated in the region surrounding the passage 17.

The cylinder head gasket according to the present invention illustrated in Figures 2 and 3 and designated by the reference numeral 1 6a consists substantially of a soft material 19 which may be additionally reinforced, in a manner which is not shown, by metallic inlays. In the region of the passage 17, the cylinder head gasket 1 6a has a combustion chamber edge framing 1 8a of U-shaped cross-section which encloses, between its two flanks 23a, 24a, an internal annular gasket portion 25 which likewise consists of soft material. As shown particularly clearly in Figure 3, an annular parting space 26 extends between the portion 25 and the surrounding soft material 19 of the cylinder head gasket.

Relative movements in the radial direction between the portion 25, the framing 18a and the soft material 19 of the cylinder head gasket are rendered possible within narrow limits by the space 26 which constitutes an interruption of the material bond between the portion 25 and the soft material 19.

The space 26 may - as indicated by solid lines in Figure 3 - be constructed continuously along the total circumference of the portion 25. In this case the material bond between the portion 25 and the soft material 19 of the cylinder head gasket is completely interrupted. However it is also possible and may be more favourable, e.g. from production considerations, still to leave initially a material bond at specific points between the portion 25 and the soft material 19 which then become severed by the described conditions of force and movement during the service of the engine. These localised material bonds, which are conveniently arranged at uniform intervals in the peripheral direction of the space 26, are indicated by broken lines 27 in Figure 3.

Even if the space 26 is made continuous, the entire cylinder head gasket 1 6a nevertheless constitutes a closed coherent component in its external appearance. This is in fact ensured by the flanks 23a, 24a of the framing 18a, which - as Figure 2 shows - overlap the soft material 19 surrounding the portion 25.

A cylinder head gasket 1 6h according to the present invention and illustrated in Figure 4 differs from that illustrated in Figures 2 and 3 solely in that a combustion chamber edge framing 1 8c is not of integral construction but is composed of two parts 37, 38. The portion 25, as in the embodiment according to Figures 2 and 3, is of soft material.

A cylinder head gasket 16j according to the present invention and illustrated in Figures 5 and 6 resembles the cylinder head gasket of Figures 2 and 3. Here again the portion 25 consists of soft material and is surrounded by one-piece combustion chamber edge framing 18f. A top flank 23f of the framing 18f overlaps the surrounding soft material 19, however, the bottom flank 24f of the framing 18f overlaps the surrounding soft material 19 only with individual prolongations 40 which are in a stellate arrangement. This can be seen particularly clearly in Figure 6. This arrangement reduces the effects of relative movements in the radial direction between the portion 25 of the surrounding soft material 19, whilst disadvantageous deformations and damage of the cylinder head gasket are eliminated.

WHAT WE CLAIM IS: 1. A cylinder head gasket for an internal-combustion engine made of a soft gasket material or a soft gasket material with metallic reinforcements having at least one cooling medium passage, and at least one fixing passage and at least one combustion chamber passage arranged to be located in the region of a combustion chamber of the engine, a metallic edge framing surrounding at least the or each combustion chamber passage, the or each framing being of U-shaped cross-section and engaging the gasket material, the gasket material located between flanks of the or each framing having an internal annular portion the material bond of which to the surrounding gasket material is interrupted at least over the major part of its outer circumference, the internal annular portion and the surrounding gasket material being made of the same material or combination of materials.

2. A cylinder head gasket as claimed in claim 1 in which the internal annular portion of the gasket material has an uninterrupted annular parting space between itself and the surrounding gasket material.

3. A cylinder head gasket as claimed in claim 1 in which the internal annular portion of the gasket material has an annular parting space between itself and the surrounding gasket material which is interrupted at spaced apart points.

4. A cylinder head gasket as claimed in claim 3, in which the annular parting space is interrupted at equidistantly spaced apart points around its circumference.

5. A cylinder head gasket as claimed in any preceding claim in which at least one of the two flanks of the or each framing overlaps the gasket material surrounding the internal annular portion.

6. A cylinder head gasket as claimed in any preceding claim in which the or each framing is constructed in a plurality of parts.

7. A cylinder head gasket as claimed in any of claims 1,2,5 or 6 in which the internal annular portion of the gasket material is constructed in a plurality of parts.

8. A cylinder head gasket as claimed in any preceding claim in which one flank of the or each framing overlaps the internal annular portion of the gasket material onto the surrounding gasket material by means of radially arranged extensions.

9. A cylinder head gasket as claimed in claim 8 in which one flank of the or each framing overlaps from the internal annular portion of the gasket material onto the surrounding gasket material by means of a closed circumferential surface, and the other flank of the framing overlaps from the internal annular portion of the gasket material onto the surrounding gasket material by means of said extensions.

10. A cylinder head gasket substantially as herein described with reference to and as shown in the accompanying drawings.

11. An internal-combustion engine having a cylinder head gasket as claimed in any preceding claim.

12. An internal-combustion engine as claimed in claim 11 in which the inside diameter of the or each combustion chamber passage is greater than an inside diameter of a liner and the outside diameter of the internal annular portion is dimensioned so that is is not subject to pressure outside the region of the liner and that the outside diameter of the or each framing is greater than the inside diameter of the surrounding gasket material.

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**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. A cylinder head gasket 1 6h according to the present invention and illustrated in Figure 4 differs from that illustrated in Figures 2 and 3 solely in that a combustion chamber edge framing 1 8c is not of integral construction but is composed of two parts 37, 38. The portion 25, as in the embodiment according to Figures 2 and 3, is of soft material. A cylinder head gasket 16j according to the present invention and illustrated in Figures 5 and 6 resembles the cylinder head gasket of Figures 2 and 3. Here again the portion 25 consists of soft material and is surrounded by one-piece combustion chamber edge framing 18f. A top flank 23f of the framing 18f overlaps the surrounding soft material 19, however, the bottom flank 24f of the framing 18f overlaps the surrounding soft material 19 only with individual prolongations 40 which are in a stellate arrangement. This can be seen particularly clearly in Figure 6. This arrangement reduces the effects of relative movements in the radial direction between the portion 25 of the surrounding soft material 19, whilst disadvantageous deformations and damage of the cylinder head gasket are eliminated. WHAT WE CLAIM IS:

1. A cylinder head gasket for an internal-combustion engine made of a soft gasket material or a soft gasket material with metallic reinforcements having at least one cooling medium passage, and at least one fixing passage and at least one combustion chamber passage arranged to be located in the region of a combustion chamber of the engine, a metallic edge framing surrounding at least the or each combustion chamber passage, the or each framing being of U-shaped cross-section and engaging the gasket material, the gasket material located between flanks of the or each framing having an internal annular portion the material bond of which to the surrounding gasket material is interrupted at least over the major part of its outer circumference, the internal annular portion and the surrounding gasket material being made of the same material or combination of materials.

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