CA2815731C

CA2815731C - Multi-layer gasket and its use

Info

Publication number: CA2815731C
Application number: CA2815731A
Authority: CA
Inventors: Kurt Hoehe; Georg Egloff; Hans Waldvogel; Wilhelm Krautmann
Original assignee: Reinz Dichtungs GmbH
Current assignee: Reinz Dichtungs GmbH
Priority date: 2010-10-28
Filing date: 2011-10-26
Publication date: 2016-08-09
Anticipated expiration: 2031-10-26
Also published as: DE102010049958B4; DE102010049958A1; WO2012055550A1; CA2815731A1

Abstract

The present invention relates to a multi-layer gasket (1), in particular to a multi-layer gasket with two or more metallic layers (2, 3). Such gaskets are especially used as flat gaskets, for example in an internal combustion engine, in the exhaust line of an internal combustion engine or also in a fuel cell. Such gaskets can for instance be cylinder head gaskets or exhaust manifold gaskets.

Description

Multi-layer gasket and its use The present invention relates to a multi-layer gas-ket, in particular to a multi-layer gasket with two or more metallic layers. Such gaskets are especially used as flat gaskets, for example in an internal com-bustion engine, in the exhaust line of an internal combustion engine or also in a fuel cell. Such gas-kets can for instance be cylinder head gaskets or ex-haust manifold gaskets.
According to the state of the art, such multi-layer gaskets often comprise sealing beads, which seal the openings to be sealed, such as combustion chamber openings, water holes, oil holes or bolt holes. These beads are usually accompanied by a deformation lim-iter, also referred to as stopper, which possesses a higher stiffness than the bead itself. As a conse-quence, when compressed between the parts to be sealed, the deformation limiter prevents the bead

2 from complete compression. Therefore, the bead re-mains in its elastic range and can therefore follow the movements of the sealing gaps because of its re-silient properties.
However, one should not underestimate the demand in space required for such a combination of bead and de-formation limiter. Especially in the sealing area of the combustion openings, the space available is very limited, which leads to the use of bead-stopper com-binations with complicated constructions.
This is due to the fact that besides the sealing properties of such sealing constructions, it is not only the demand in space that is of high importance, but also that the sealing construction provides a long-term durability. Further, such sealing construc-tions shall be flexibly applicable under the most varied conditions.
Therefore, it is the object of the present invention, to provide a gasket and its use, which gasket re-quires only limited space, is flexibly applicable, cost-efficient in its production, and reproducibly provides for a long-term durability as well as for an excellent sealing.

2a In accordance with an embodiment of the present invention there is provided a multi-layer gasket comprising: a first metallic layer, a second metallic layer adjacent to the first layer, which layers both extend essentially over the area of the complete gasket, and a further metallic layer, and optionally further layers, wherein the first layer, the second layer and the further metallic layer each have at least a first passage opening, which first passage openings are arranged on and immediately opposite to each other. A sealing bead is arranged in each of the first layer and in the further metallic layer around the at least one first passage opening at least in sections or completely surrounding the passage opening.
The sealing bead in the further layer is configured symmetrically relative to the sealing bead in the first metallic layer. A
profiling in the second layer is arranged on and immediately opposite to the beads and surrounds the first passage opening at least in sections. A plane of the second layer extends transversely to the circumferential direction of the profiling and relative to the thickness of the second layer in its areas adjoining laterally to the profiling and pointing towards the outer edge of the gasket layer, in the center of the second layer. The profiling is transverse to the circumferential direction showing a wave-shaped or trapezoidal cross section consisting of crests and troughs and having at least one period. Only part of the crests and troughs 2b extend on one side out of the plane of the second layer. For at least one, several or all of the wave crests and/or the wave troughs, a first tangent to the profiling touching essentially in the middle of a wave crest or wave trough and a second tangent touching the profiling essentially centrally between the wave crest and its neighbouring wave trough or between the wave trough and its neighbouring wave crest define an angle a between 0 and 900. Along at least one cross section through the second layer, the crests and troughs protrude beyond alternating sides of the plane of the layer.
The gasket according to one embodiment the invention comprises at least two metallic layers, which both extend essentially or completely over the complete area of the gasket. If necessary, further layers may be present

3 and can be designed in various ways.
The at least two metallic layers each comprise at least one first passage opening, which in the adja-cent layers are adjacent to each other. Examples for such passage openings comprise combustion chamber openings in cylinder head gaskets, water or oil holes, bolt holes in cylinder head gaskets or in other gaskets or exhaust gas passage openings in gas-kets of the exhaust line of a combustion engine.
This first passage opening in the first one of the at least two metallic layers is encircled by a sealing bead. Encircling does not necessarily mean that the sealing bead individually encloses this particular passage opening. Rather, it may enclose several pas-sage openings simultaneously without passing along the complete edge of each passage opening.
In the adjacent second layer, a profiling is arranged adjoining to this sealing bead in the first layer.
This profiling increases the thickness in the area of the sealing bead and therefore increases the compres-sion of the sealing bead.
In contrast to the ordinary state of the art, this profiling is not arranged alongside the sealing bead within the plane of the layer, but opposite to the sealing bead in the adjacent layer. This means that the profiling at least partially comes to lie on or within the bead. Doing so, the profiling does not need to be arranged symmetrically to the bead; in-stead their radial extension may be different. It is further possible that the profiling extends into the neighbourhood or until the circumferential edge of the first passage opening.

4 This profiling also encircles the first passage open-ing at least in sections and in a direction trans-verse to this circumferential direction may show dif-ferent cross-sections. These cross-sections may also change along the circumferential direction.
The second layer defines a plane of a layer, which is determined by those areas of the second layer, which extend transversely to the circumferential direction, i.e. parallel to a plane which is spaned by the usu-ally plane circumference of the passage opening, and each of which is situated immediately adjacent to the profiling in the second layer on both sides of the profiling or which continue the layer radially out-side the profiling adjacent to the profiling. Thus, the plane of the layer extends transversely to the circumferential direction of the profiling and at half the height of the second layer in the area men-tioned. The profiling can extend from this plane in one or both directions.
The profiling according to the invention in a direc-tion transverse to the circumferential direction around the first passage opening shows a cross-section which at least in sections is wave-shaped or trapezoidal with at least one period of a wave, pref-erable more than a period of a wave. Here, a period is defined analogously to a sine wave as 360 . A pe-riod thus consists in a sequence of a wave crest and a wave trough until the beginning of the next wave crest. This way, the cross-section comprises at least one wave crest and one wave trough. It is however preferred that it shows at least two wave crests and two wave troughs. In this context, trapezoidal cross-sections are to be understood in such a way that each wave crest and each wave trough shows an essentially trapezoidal cross-section.
The trapezoidal or wave-shaped profiling here is how-

5 ever no rectangular stopper. Considering on the one hand a tangent to the wave crest - or to a wave trough - which touches either a tangent in the plane of the layer or the plane of the layer itself and on the other hand a tangent to the layer touching in the flank between a wave crest and a neighbouring wave trough - or between a wave trough and its neighbour-ing wave crest - either in the middle of the flank or at the position with maximum slope of the flank, these tangents do not define an orthogonal angle - as would be the case for a rectangular stopper - but an angle a with 0 < a < 900 .
This means that the profiling according to the inven-tion extends in a flattened manner and is no rectan-gular stopper. This provides for an improved elastic behaviour of the stopper.
With a sine-shaped cross-section of the profiling, the angle a is preferably 45 a 72 õ especially preferably 48 a 68 . With a trapezoidal cross-section of the profiling, the angle a is preferably 60 5 a 80 õ
especially preferably 65 5 a 5 750 .
With a trapezoidal cross-section, the tangent to the layer in the flank corresponds to a prolongation of the flank itself. These preferred ranges of angles provide for an essentially easy closing and opening of the halves of the tool during embossment, which reduces wear and guarantees for an outstanding dura-bility of the tools. In addition, a high stiffness of the profiling is achieved with a small demand in space.

6 According to the invention, the crests and troughs are arranged in such a manner that only part of them is situated on one side outside the plane of the layer. The profiling is thus formed in such a way that it is not completely situated on a single side outside the plane of the second layer. It needs to be stressed that the most extreme points of the respec-tive crests and troughs need to be considered, not the neutral fibre. The relevant point defining whether a crest or trough fulfils this condition is the maximum point on the surface pointing away from the centre of the structure.
A full bead usually comprises only one crest or one trough and therefore already in this is different from the profiling which comprises at least one pe-riod, thus one crest and one trough. Further the two elements are different in that the length of a period for the profiling is less than the four-fold of the material thickness of the profiled layer, while the bead from foot to foot is broader than the four-fold of the material thickness of the beaded layer. This also influences the resilient properties of the two elements. Considering the two layers separately, the displacement of a profiled layer of a new, not yet installed gasket under a load with 500 N/mm is less than 40 pm, whereas the bead in a separately consid-ered layer under the same conditions makes a dis-placement of at least 80 pm, with the values speci-fied relating to the load section of the correspond-ing load deflection curves.
According to the invention, the sealing bead and the opposite, pressure-increasing profiling are situated in two different metallic layers of the gasket, which

7 essentially extend over the area of the complete gas-ket. The area of the complete gasket is of course to be understood as the extension in the plane while leaving out openings and passages. The sealing bead and the profiling thus are formed in ordinary gasket layers. It is thus not necessary to provide for a particular, length-reduced beaded layer or profiled layer, which facilitates the production of the gas-ket. It shall be stressed that at least all fastening holes pass through both the beaded layer and the pro-filed layer. This makes it possible to produce the sealing construction proposed in a simple and cost-efficient manner.
The sealing construction according to the invention can also be realized in such gaskets which comprise elastomeric or rubber-based sealing elements, which are often applied as lip-shaped profiles, e.g. by on-top or edge moulding. It is preferred that these lip-shaped profiles are applied in a symmetric manner, which means that an application at the central gasket layer is preferred. This central gasket layer may of course also be a beaded or profiled layer.
With the lip-shaped profiles, it is preferred to pro-vide for a recess in one or both layers adjoining to the layer with the applied sealing profile. The re-cess is provided in the area adjoining to the profile and preferably also in the areas immediately border-ing to these areas, for instance over an area corre-sponding to the five-fold width of the applied pro-filing. As an alternative, in case the applied pro-filing extends along the outer edge of the gasket, the adjoining layer(s) terminate immediately before the beginning of the applied profile, at the most at a distance which corresponds to the double width of

8 the profile. Thus, the adjoining layers have a re-duced extension.
As the sealing bead and the profiling are arranged immediately one lying on the other, it is extremely efficient with respect to its demand of space. The sealing construction according to the invention in a cylinder head gasket for example only requires a width of 1.5 to 2.5 mm when a sealing bead thickened according to the invention with the profiling is ar-ranged between different combustion chambers. Never-theless, with an abundance in space, broader con-structions are possible as well.
This makes it possible that the sealing construction according to the invention is only slightly sensitive against a shift of the central line of the profiling relative to the central line of the bead. In general, it is admissible with the sealing construction ac-cording to the invention, that the central line of the profiling is shifted relative to the central line of the bead by more than 0.3 mm. In some cases even more than 0.5 mm are acceptable. In the same way, it is not necessary that the central lines run in paral-, lel or in case of a shift as outlined above, concen-tric to each other. The shift may also change along the course of the bead or the profiling, respec-tively. It is most recommended that at least three linear contacts extend between the two feet of the bead.
While with the bead-stopper sealing constructions of the state of the art both the bead and the stopper are distanced to the passage opening, the sealing construction according to the invention makes it pos-sible that the profiling extends until the edge of

9 the passage opening. It is thus prolonged. This is especially advantageous, as the profiling provides the respective metal sheet with a higher stiffness compared to a smooth metal sheet and the section af-fected therefore has much less tendency to flutter.
This embodiment is often combined with a concentric, but shifted arrangement of the central lines of the bead and the profiling.
A shift of the central lines of bead and profiling can also result from a prolongation of the profiling relative to the outer edge of the bead. The increased number of transversely extending structures improves the sealing behaviour towards coolants and/or lubri-cants.
The sealing construction according to the invention shows an extraordinary durability and allows to be flexibly adapted to the most varied of sealing geome-tries and types of gaskets.
As a coating is possible but not mandatory, the pro-duction process is dominated by the embossment of the sealing beads and the profiling, which allows for a cost-efficient production. Nevertheless, an excellent sealing function and a high reproducibility of the production are guaranteed.
According to the invention, the crests and troughs do not all extend on one side of the plane of the second layer. In contrast, it is advantageous if the two wave troughs following on a wave crest protruding on one side of the plane (and vice versa) return at least into the plane of the layer or exceed beyond that towards the side of the plane of the layer oppo-site to the wave crest. In this context, it is advan-tageous if all wave crests protrude towards one side of the layer of the plane in the same degree. In the same way it is advantageous if all wave troughs on one side of the layer protrude to the same degree 5 relative to the plane of the layer or relative to the wave crests. The degree of protrusion of the wave crests on the one hand and of the wave troughs on the other hand relative to the plane of the layer does however not need to be identical.
A symmetric arrangement with the wave crests and wave troughs protruding to different sides of the plane of the layer is especially advantageous; with this em-bodiment it is also possible that the respective pro-trusions have the same dimensions towards both sides.
Further, it is advantageous if in a profiling which comprises several periods of a wave, a plurality, thus at least two, consecutive periods protrude with the same dimension or at least with essentially the same dimension from the plane of the layer.
In, other embodiments, it can be advantageous if the wave crests and troughs following one on the other along the cross section of the wave, have different constitution, e.g. if the amplitude along the cross section first increases and then decreases.
The cross section of the profiling according to the invention may comprise trapezoidal and/or wave-shaped areas. This means that it may both comprises purely or essentially trapezoidal or purely or essentially sinus-shaped sections. Further, it may comprise sec-tions with a shape being an intermediate form between trapezoidal and sinusoidal. These respective cross-sectional geometries may extend continuously and along the whole course of the profiling. In case of a profiling encircling a passage opening, the wave crests and troughs preferably extend continuously in a concentric manner with essentially uniform dis-tances. The wave-shaped or trapezoidal cross sections may however also only be given in sections. It is even possible that along the course of the profiling, the cross sections of various sections are offset relative to each other. In the last case, a cup- or dimple-shaped structure may arise as the profiling according to the invention.
Such a dimple-shaped profiling is for instance known from EP 1298365 A2. Thus, dimple-shaped profilings in the sense of the present invention shall also com-prise the dimple-shaped structures in the sense of EP
1298365 A2, the disclosure of which is taken over into this description by reference to EP 1298365 A2.
A wave-shaped or trapezoidal profiling is for in-stance known from WO 01/96768 Al and WO 2008/012363 Al. Thus, wave-shaped or trapezoidal profilings in the sense of the present invention shall also com-prise the wave-shaped or trapezoidal structures in the sense of WO 01/96768 Al and WO 2008/012363 Al, the disclosure of which is taken over into this de-scription by reference to WO 01/96768 Al and WO 2008/012363 Al.
In a further essentially advantageous embodiment of the invention, the transition sections between wave crests and wave troughs are tapered with respect to the thickness of the adjoining wave crests and wave troughs. The thickness of the transition regions, also referred to as flanks, is advantageously reduced by 5 to 50 %, more advantageously by 10 to 40 %, and most advantageously by 10 to 30 % relative to the thickness of the profiling in the area of the wave crests and wave troughs.
In other advantageous embodiments, the profiling pos-sesses such a width that it extends within the area of the bead, thus between the foot points of the sealing bead. The cross section of the profiling is thus less broad or at least equally broad than the width of the sealing bead, which is defined by the distance between the two foot points of the sealing bead. In advantageous embodiments, the width of the profiling, measured between the foot points of the profiling in the cross section is 30 %, more advan-tageously 50 %, but advantageously also 100 % of the width of the sealing bead, thus broader than the width of the sealing bead measured in the cross sec-tion between the foot points of the sealing bead. In other embodiments, the width of the profiling may be restricted to 200 % of the width of the sealing bead. The foot points of the profiling and the seal-ing bead for the measurement of the width of the re-spective elements can be measured in the uninstalled state, thus before the gasket is installed for the first time, or in the de-installed state after in-stallation and compression.
Stainless steels as well as non-hardened and hardened carbon steels have shown to be advantageous materials for the first and/or second layer. Hardening here can take place before or after forming of the profiling.
For a large amount of applications, spring steel pro-vides particular advantages. The layers further can be coated one-sided or double-sided, in areas or over a whole surface, in order to improve the sealing properties of the sealing construction. In this con-text it is especially advantageous if at least the area of the beads and/or of the profilings are coated. The coating does usually extend over the feet of the respective structure, at least by half a width of the bead or profiling, respectively. Coating mate-rials which are particularly advantageous comprise a thermoset binder or several thermoset binders, as they improve the micro sealing.
In the following some examples of gaskets according to the invention are further described. The same or similar reference numbers are used for identical or similar elements, which means that their description is not always repeated.
All characteristics shown in the following examples are advantageous for the present invention and can be combined with each other, even if they have to be taken out of the context of the respective examples.
It is shown in Figures 1 and 3 a gasket according to the invention;
Figures 2, 4 and 5 a further gasket according to the inven-tion;
Figures 6 to 13 further gaskets according to the inven-tion in cross section which allows to demonstrate the sealing construction ac-cording to the invention.
Figure 1 shows a gasket 1 from its bottom side, the gasket 1 comprises two combustion chamber passage openings 5a and 5b. The gasket further comprises bolt holes 30.
Sealing constructions are arranged around the respec-tive combustion chamber openings 5a and 5b, which in figure 3 are represented in cross section. The com-bustion chamber openings 5a and 5b here are sur-rounded by profilings 7a, 7b and sealing beads 6 resting on them, with the sealing beads not being visible in figure 1. They provide for a reliable sealing of the combustion chambers 5a and 5b.
Figure 2 shows a cylinder head gasket 1; here the lower layer 3 is visible. This second layer 3 here shows combustion gas or combustion chamber openings 5a, 5b and 5c, which are encircled by sealing beads -not shown in Figure 2 - and profilings 7a, 7b and 7c, respectively. The design of the sealing structures in the narrow bridge areas immediately between the com-bustion chamber openings is often crucial. Here, for demonstration purposes, the bridge are between com-bustion chamber openings 5a and 5b (left side) is de-signed differently than the bridge area between open-ings 5b and 5c (right side). The same is true for the transition areas of the sealing structures linking the bridge areas with the sealing areas of the indi-vidual combustion chamber openings. These different designs are marked with circles in Figure 2. In the example shown on the left side, the profiling 7a shows a smoothed angle of about 20 to 30 and with this angle passes into the profiling 7b, whereas a straight section of the profiling passes through the bridge section. In contrast, in the example depicted on the right side, only half of the profiling 7b - to be more precise half its width - continues into half of the profiling 7c with a steep angle. These halves do not pass through the bridge region. The respective other halves, thus the halves closer to the combus-tion chamber passage openings 5b and 5c, respec-tively, when entering the bridge section approach 5 each other steadily until they have passed half the bridge length and then again move away from each other.
Figure 3 shows a cross section of the two-layered

10 gasket of figure 1 along cross section A-A with a first layer 2 and a second layer 3. The combustion chamber opening is situated on the left side of the section shown and is marked with reference number 5a.
15 Figure 3 further shows a tangent 20a to the wave crest 11 at about a central position of the wave crest as well as a tangent 20 parallel to the latter, which is a tangent to the layer plane 9 or represents the layer plane 9 itself. It further shows a tangent 21 to the flank between the wave crest 11 and the wave trough 10. These tangents 20 and 21 define an angle a. All figures 1 and 13 are only schematic drawings, which do not represent the angles at scale.
The angle a in all embodiments of the profilings de-picted is between 45 and 72 , in both cases includ-ing the limits.
The first layer 2 comprises a plane of the layer 8 and a sealing bead 6, which encircles the combustion chamber opening 5a. The sealing bead 6 comprises a foot point 13a and a foot point 13b. The second layer 3 of the gasket comprises a wave-shaped profiling 7 with wave crests 10 and wave troughs 11. This profil-ing at its foot points 14a and 14b continues into the flat areas of the second layer 3. The plane of the layer 9 of the second layer is defined by the foot points 14a and 14b and the adjacent areas of the layer 3, which point away from the profiling 7. In those cases, where the profiling 7 extends until the edge of the passage opening 5a, the plane 9 of the layer 3 is defined by the area adjoining to the outer foot point 14b of the profiling circumferentially on the outer side.
In figure 3, wave crests 10 and wave troughs 11 pro-trude from the plane 9 of layer 3 into different di-rections and with essentially identical height. The width of the profiling 7 is larger than the width of the bead 6 which is defined by the distance of the foot points 13a and 13b. The profiling 7 extends im-mediately adjacent to the bead 6 and in radial direc-tion slightly protrudes to both sides of the foot points 13a and 13b of the bead 6.
Figure 4 shows a cross section of the gasket in fig-ure 2 along line B-B, with the first layer 1 being arranged as the lower layer and the second layer 3 with the trapezoidal profilings 7a and 7b as the up-per layer.
The profilings 7a and 7b again are arranged immedi-ately opposite to the beads 6a and 6b in the first layer. In this case, the width of the profilings 7a and 7b is essentially the same as the width of the beads 6a and 6b. The concave sides of the wave troughs 11 are situated in the plane 9 of the layer, whereas the convex sides of the wave crests 10 in an asymmetrical matter protrude further beyond the plane 9 of the layer. In total, a one-sided profiling re-sults, in which the peaks of the wave crests - on the convex sides - are situated at the height of the sur-face of layer 3.

Figure 5 shows a further sealing construction. In contrast to the foregoing example, where combustion passage openings have been shown, the section given here is adjacent to a coolant passage 50 in the back-land of the gasket, close to the outer edge of the gasket. In general, the backland especially comprises the area, which when observed from the combustion gas passage openings, is situated behind the bolt holes.
The section shown in figure 5 essentially corresponds to section C-C in figure 2. While the bead 15 at the coolant passage 50 has no thickening, the bead 6, which runs in parallel to the outer edge of the gas-ket is arranged opposite to a profiling 7 in the sec-ond layer 3. The profiling 7 is configured in the same way as the profilings 7a and 7b in figure 4.
Here, the profiling especially aims on support and thickening.
Figure 6 represents a sealing construction, which corresponds to the one from figure 3. However, here, the first layer 2 as well as the second layer 3 is coated on both surfaces with coatings 16a, 16b, 16c and 16d.
Figure 7 again shows a sealing construction similar to figure 3, which apart from the first layer - here referred to as 2b and the second layer already known shows a third layer, referred to as 2a. In the seal-ing construction, this third layer 2a is arranged symmetrically to layer 2b. Layers 2a and 2b on their surface facing towards the second layer 3, have no coating, but only on their surface which faces away from layer 3, which means that in all cases, one coating layer is given on the outer surfaces as well as at all interfaces between layers. These coatings are referred to with reference numbers 16a, 16b, 16d and 16d.
Figure 8 shows a further sealing construction compa-rable to the one in figure 3, which again shows the layers 2a and 3 already known from figure 7. Here, layer 3 is coated with a coating 16b on only one of its surfaces. The second layer 3 borders to a further layer 17a with coatings 16c, 16d which layer 17a ad-joins to a further layer 17b with a coating 16e. This fourth layer 17b comprises a bead 15, which shows a symmetric configuration relative to the bead in the first layer 2a. To summarize, the embodiments of fig-ures 7 and 8 are different from each other in that they have a different distribution of the coatings on the surfaces of the layers as well as by the addi-tional unstructured metal sheet layer 17. This means that the embodiment depicted in figure 8 is suited for larger sealing gaps than the one in figure 7.
Figure 9 in a large section again shows a sealing construction similar to figure 3, here however with a bead 6 being broader than the profiling 7.
Figure 10 depicts a sealing construction comparable to figure 3. However, here the profiling 7 is consid-erably broader than the bead 6.
In figure 11 a sealing construction is shown with a bead 6 in the first layer 2. The elements to be sealed against each other are arranged on the top surface of layer 3 and below the bottom surface of layer 2 (not shown). The layer 2 on one of its sur-faces is provided with a coating 16c. On the other side of the layer 2, the second layer 3 is arranged, which shows a profiling 7. This profiling is designed as described beforehand and shows the same width as the bead 6. The wave crests and wave troughs on both surfaces of the profiling 7 are completely filled with coatings 16a and 16b. In this extremely sche-matic representation, an improved sealing between the elements to be sealed against each other is achieved both with the coating 16b as well as with the coat-ings 16a and 16c on the outer surfaces.
In figure 11, the tangents 20 and 21 as well as the angle a are shown on the example of a profiling with a trapezoidal cross section. In this case, the angle a according to the invention ranges between 600 and 80 , including the limits of this range.
Figure 12 shows an especially preferred embodiment of the profiling 7 in layer 3. This profiling shows a wave-shaped cross section. This cross section com-prises four wave crests 10a, 10b, 10c and 10d as well as three wave troughs lla, llb and 11c situated be-tween the wave crests. The profiling depicted in fig-ure 12 thus shows more than three periods, to be more precise almost four periods. The transition regions between the wave crests and the wave troughs, here referred to with reference numbers 12a, 12b, 12c, 12d, 12e, 12f and 12g are considerably tapered rela-tive to the wave crests and wave troughs, namely by about 30 %. This means that the local thickness of the material measured orthogonally to the surfaces of layer 3 in the area of the flanks is considerably less than the corresponding thickness of the material at the wave crests and wave troughs. This tapering of the flanks causes an increase of the stiffness of the profiling and in addition makes it possible to form a larger number of waves - a larger number of periods -with a given length between the foot points 14a and 14b. The interaction of the above mentioned factors causes an increased stiffening of the profiling, which means that it can be designed with a considera-bly larger stiffness than the adjoining bead to be 5 thickened. This means that the sealing construction according to the invention in situations with little space can provide for excellent sealing solutions at low cost. The sealing construction can generally be used in flat gaskets, for instance flat gaskets for 10 engine aggregates, exhaust lines, but especially for cylinder head gaskets - in particular with little abundance of space, in the case of cylinder head gas-kets little space between the combustion chamber openings.
Figure 12 further shows tangents 20a and 20b with 20a being a tangent to a wave trough 11c and tangent 20b being a tangent to a wave crest 10d, which both run =
in parallel to the plane 9 of the layer. Together with the tangents 21a and 21b to the flank 12f at about the centre of the flank 12f, the tangents 20a and 20b define an angle a, which according to the in-vention is between 45 and 72 .
Figure 13 shows a further sealing construction compa-rable to the one in figure 3. In this case, the wave-shaped profiling 7 extends until the edge of the com-bustion chamber passage opening 5. Figure 13 further shows central lines 22 and 23 of the sealing bead 6 and the profiling 7, respectively. It is obvious that these centre lines are set off relative to each other. Nevertheless, the profiling 7 is arranged im-mediately opposite to the bead 6. In this figure, too, some of the tangents to the maxima of the wave crests and to the minima of the wave troughs as well as some of the tangents to the flanks between wave troughs and wave crests are given in order to indi-cate angle a.
In general, almost all metallic gaskets can be de-signed according to the invention. It is especially recommended to design cylinder head gaskets with a high demand of regular introduction of load according to the invention. According to the invention, all numbers of layers starting from at least two are pos-sible. In the sealing construction according to the invention, the beads are always in the main force load. The use of the sealing construction according to the invention both at the combustion gas passage opening and in the backland of the gasket allows for a variable adaptation of the thicknesses, which means that a topographic distribution of the thicknesses adapted to the respective engine is possible over the range of the complete gasket.
All coating materials known as coatings for metallic gaskets in the state of the art can be applied as the coating for the structured layers, which comprise the sealing bead ort he profiling.
The improvement of the micro sealing and/or of the slide-friction coefficient can be achieved by these coatings. In most cases the actual coating is applied to an adhesive primer layer which in turn is situated immediately on the surface of the metal sheet. Only by way of example, coatings based on fluoropolymers, such as for instance FPM (vinylidenefluoride-hexa-fluoropropylene copolymere), silicone rubber or NBR
rubber (acryle-butadiene rubber), PUR (polyurethane), NR (natural rubber), FFKM (perfluororubber), SBR
(styrole-butadiene rubber), BR (butyl rubber), FVSQ
(fluorosilicone), CSM (chlorosulfonated polyethylene) as well as silicone and epoxy rubbers shall be men-tioned. For the application of these coating materi-als, screen printing, curtain coating and spraying are suited methods.
Apart from this, coatings based on polyester resins, PEEK (polyetherketone), PFA and MFA (both being fluoro polymers) as well as silica and epoxi resins can be used. With these coating materials, powder coating methods can be applied.
The invention with the profiling being arranged on top or below the bead enables an excellent adhesion of the coating and prevents from accidental flowing of the coating out of the area of the bead. To achieve this, the coatings are applied one-sided, double-sided, on the complete area or only partially.
If necessary, it is possible to apply rubber-based sealing elements in the gaskets according to the in-vention.

Claims

The embodiments of the present invention for which an exclusive property or privilege is claimed are defined as follows:

1. A multi-layer gasket comprising:
a first metallic layer, a second metallic layer adjacent to the first layer, said first and second layers extend essentially over an area of the gasket, and at least one further metallic layer, wherein the first layer, the second layer and the at least one further metallic layer each have at least a first passage opening, which first passage openings are arranged on and immediately opposite to each other, wherein a sealing bead is arranged in each of the first layer and in the at least one further layer at least partially around the at least one first passage opening, wherein the sealing bead in the at least one further layer is configured symmetrically relative to the sealing bead in the first metallic layer, wherein a profiling is arranged in the second layer, on and immediately opposite to the sealing beads and at least partially surrounds tl-e at least one first passage opening, and wherein a plane of the second layer, extends transverse to a circumferential direction of the profiling and relative to a thickness of the second layer in areas adjoining laterally to the profiling and pointing towards an outer edge of the gasket, in a center of the second layer, wherein the profiling is transverse to the circumferential direction and has a wave-shaped or trapezoidal cross section consisting of crests and troughs and has at least one period, wherein only part of the crests and troughs extend on one side out of the plane of the second layer, wherein for at least one of the crests or at least one of the troughs, a first tangent to the profiling touches essentially in a middle of the at least one crest or the at least one trough and a second tangent touches the profiling essentially centrally between the at least one crest and a neighbouring trough or between the at least one trough and a neighbouring crest at an angle a between 0° and 90°, wherein along at least one cross section through the second layer, the crests and troughs protrude beyond alternating sides of the plane of the second layer.

2. The multi-layer according to claim 1, wherein the at least one further layer comprises a plurality of layers.

3. The multi-layer gasket according to claim 1 or 2, wherein the profiling in the second layer is arranged on top of the bead.

4. The multi-layer gasket according to any one of claims 1 to 3, wherein the bead in the first layer is a full bead.

5. The multi-layer gasket according to any one of claims 1 to 4, wherein the at least one further metallic layer is arranged adjacent to the second layer.

6. The multi-layer gasket according to any one of claims 1 to 4, wherein along at least one cross section through the second layer, the crests and troughs protrude beyond alternating sides of the plane of the layer, with the protrusions having the same dimensions.

7. The multi-layer gasket according to any one of claims 1 to 4, wherein the profiling transverse to the circumferential direction comprises at least one wave-shaped cross section and in that the angle .alpha. is 45°<=.alpha.<=
72°.

8. The multi-layer gasket according to claim 7, wherein the angle .alpha. is 45°<=.alpha.<= 68°.

9. The multi-layer gasket according to any one of claims 1 to 4, wherein the profiling transverse to the circumferential direction at least in sections shows a trapezoidal cross section and in that the angle .alpha. is 60°<=.alpha.<=80°

10. The multi-layer gasket according to claim 9, wherein the angle .alpha. is 65°<=.alpha.<=75°.

11. The multi-layer gasket according to any one of claims 1 to 4, wherein in the profiling, along the wave-shaped or trapezoidal cross section, the neighbouring crests following on each trough protruding towards one side of the plane of the second layer extend at least into the plane of the second layer or protrude beyond the plane of the second layer towards the opposite side of the plane of the second layer.

12. The multi-layer gasket according to any one of claims 1 to 4, wherein in the profiling, along the wave-shaped or trapezoidal cross section, the neighbouring troughs following on each crest protruding towards one side of the plane of the second layer extend at least into the plane of the second layer or protrude beyond the plane of the second layer towards the opposite side of the plane of the second layer.

13. The multi-layer gasket according to any one of claims 1 to 4, wherein the profiling has at least one of a wave-shaped structure, a trapezoidal structure and a dimpled structure.

14. The multi-layer gasket according to any one of claims 1 to 4, wherein the profiling in transition regions between crests and troughs has a reduced thickness compared to a thickness of neighbouring crests and troughs, the reduced thickness being reduced by 5 to 50% of the thickness of the crests and troughs.

15. The multi-layer gasket according to claim 14, wherein the transition regions between crests and troughs have a thickness reduced by 10 to 40% compared to the thickness of the neighbouring crests and troughs.

16. The multi-layer gasket according to claim 14, wherein the transition regions between crests and troughs have a thickness reduced by 10 to 30% compared to the thickness of the neighbouring crests and troughs.

17. The multi-layer gasket according to any one of claims 1 to 4, wherein the profiling is situated opposite to the central area.

18. The multi-layer gasket according to claim 17, wherein the profiling is situated opposite to a centrally located 30% of a total width of the sealing bead.

19. The multi-layer gasket according to claim 1, wherein the profiling in the cross section is broader, has the same width or is less broad than the width of the sealing bead of the first layer, defined by a distance between two foot points of the sealing bead.

20. The multi-layer gasket according to claim 14, wherein a width of the profiling is >= 30 % of a width of the sealing bead.

21. The multi-layer gasket according to claim 20, wherein the width of the profiling is >= 50% of the width of the sealing bead.

22. The multi-layer gasket according to claim 21, wherein the width of the profiling is >= 100% of the width of the sealing bead.

23. The multi-layer gasket according to claim 22, wherein the width of the profiling is <= 200 % of the width of the sealing bead.

24. The multi-layer gasket according to any one of claims 1 to 4, wherein the first passage opening is a combustion chamber opening of a cylinder head gasket, a gas passage opening, an oil passage opening, a water passage opening or a bolt opening of the gasket.

25. The multi-layer gasket according to claim 24, wherein the gasket is in an engine aggregate or in an exhaust line.

26. The multi-layer gasket according to any one of claims 1 to 4, wherein at least one of the first layer and the second layer comprises or consists of spring steel, spring-hard or non-spring hard stainless steel or a hardened or non-hardened carbon steel.

27. The multi-layer gasket according to any one of claims 1 to 4, wherein at least one of the first layer, the second layer and the at least one further layer are coated on one surface or on both surfaces, in areas or on the complete surface.

28. The multi-layer gasket according to any one of claims 1 to 4, wherein at least one of the first layer, the second layer, and the at least one further layer are coated in at least one of (i) an area of the sealing beads; (ii) an area of the profilings; (iii) an area opposite to the sealing beads; and (iv) an area opposite to the profilings.

29. Use of the multi-layer gasket according to any one of claims 1 to 18 as a gasket produced from flat metal sheet or as metallic flat gasket, in at least one of an internal combustion engine, an exhaust line and a fuel cell.

30. The use of claim 29 wherein the multi-layer gasket is a cylinder head gasket or exhaust gasket.