WO2006079452A1

WO2006079452A1 - Metallic flat seal

Info

Publication number: WO2006079452A1
Application number: PCT/EP2006/000226
Authority: WO
Inventors: Georg Egloff; Kurt Hoehe; Bernd Ruess; Armin Guetermann; Robert Blersch
Original assignee: Reinz-Dichtungs-Gmbh
Priority date: 2005-01-26
Filing date: 2006-01-12
Publication date: 2006-08-03
Also published as: DE102005003674A1; DE102005003674B4

Abstract

The invention relates to a metallic flat seal (1) comprising at least one metallic sealing layer (2) which is provided with at least one spacer (4) that is molded out of the material of the sealing layer on at least one of the outward-facing surfaces of said sealing layer. The spacer (4) is disposed in an area of the sealing layer which is essentially not impinged upon by pressure applied to the sealing surfaces in the assembled state of the seal. The spacer is selected among a bracket (6) which is separated from the sealing layer while leaving a connecting section (61), said bracket (6) being folded back onto itself or onto the sealing layer, or in which an elevation (7) is embodied. The spacer can also be embodied as a pot-type or pot segment-type protrusion (5). The sides (51) of the elevation (7) or the pot (segment)-type protrusion rise from the sealing layer in such a steep manner that the same cannot be accommodated altogether by a corresponding elevation (7') or a corresponding pot (segment)-type protrusion (5') of an additional, identically produced sealing layer (2') that is congruently placed on the first sealing layer.

Description

METALLIC FLAT DENSITY

The invention relates to a metallic gasket with at least one metallic gasket layer having at least one out of the material of the gasket layer formed spacers on at least one of its outwardly facing surfaces. The spacer is arranged in a region of the sealing layer, which is essentially not acted upon in the installed state of the seal with sealing surface pressure. The spacer is intended to prevent the metallic gaskets from sticking together when stacked one on top of the other. In such a case, there is a risk that, in particular automatic installation of the gaskets by means of a robot, more than just a flat gasket is gripped from the stack to be processed and installed between the mating surfaces to be sealed. This risk is particularly great for single-layer flat gaskets, since there are generally no rivets, clamps or other fastening means with which the individual gasket layers are fastened together in multilayer flat gaskets. These attachment points generally protrude beyond the outer surfaces of the multi-layer seals, thereby facilitating separation of the individual seals during installation. The likelihood that the gaskets adhere to each other during installation, increases in addition, if, for example, on the outer surfaces of the gasket, a coating is present or oil residues adhere.

In order to avoid the adherence of the seals, release paper is often placed between the individual seals. In addition, it is customary to put successive seals in a stack by 180 ° to each other twisted each other. However, both options increase the amount of work and thus the cost of both the packaging of the seals as well as their unpacking and installation considerably.

In DE 10142000 B4 has been proposed to provide at the top and / or bottom of an article to be stacked, for example, a cylinder head gasket, spacer elements. These Distance elements are embossed or punched. In this case, the embossing or stand tool is offset or rotated from seal to seal, so that the individual seals differ in position or orientation of the spacer elements from each other. Due to the offset spacer elements, the individual seals, before they are installed, no longer be stacked against each other twisted, but can be placed in the same orientation to each other. But their production is extremely complicated because it must be worked with at least two different tool sets for the production of embossing or punching. In addition, this solution provides no absolute assurance that the seals are actually stacked easily separable for automatic installation. If rejects are produced during the production of the seal and if an odd number of rejects are rejected out of the production, two identical seals come to lie on one another when using two different spacer elements, which can then no longer be reliably separated from one another.

There was therefore still a need for a metallic flat gasket, which, even if it is a single-layer and provided with a coating seal, congruent stacked with similar seals stacked and automatically or manually from the stack can be installed, without causing separation problems between the individual seals. The necessary measures should be integrated as well as possible into the production processes in the production of the metallic flat gasket and do not use any additional material other than that required for the production of the gasket. In accordance with the invention, it is appropriate to specify such a metallic flat gasket.

The solution of this problem is achieved with the metallic gasket according to claim 1. Preferred developments of the gasket are described in the subclaims.

The invention accordingly relates to a metallic flat gasket having at least one metallic gasket layer which has at least one spacer molded out of the material of the gasket layer on at least one of its outwardly facing surfaces. The spacer is arranged in a region of the sealing layer, which is essentially not acted upon in the installed state of the seal with sealing surface pressure. The spacer is selected from a cup-like projection or a napfsegmentartigen projection whose edge rises at least partially so steeply out of the gasket that the projection of a corresponding cup-like or napfsegmentartigen projection of another, identically manufactured gasket layer can not be fully absorbed if this gasket congruent to the first gasket layer is placed. Further, the spacer may be selected from a tab which is separated from the gasket layer leaving a connection portion. This tab is folded back either on itself or on the gasket layer or it is formed in a survey whose flanks rise at least partially so steeply from the gasket that they from a corresponding elevation of another, identically manufactured gasket layer, which congruent to the first Gasket layer is placed, can not be fully absorbed.

The metallic flat gasket according to the invention thus provides on at least one of its outwardly facing surfaces a spacer which is formed out of the material of the gasket layer. Therefore, no additional material is needed. In addition, the flat gasket according to the invention can correspond virtually completely to a seal of the prior art and must be modified compared to this only by providing the spacers. The spacers according to the invention are also selected so that they can be produced in the course of production steps, which are used anyway in the production of the metallic flat gasket. The preparation of the spacers can therefore be integrated in a time-saving and cost-effective manner in the manufacturing steps of the metallic flat gasket. Suitable process steps are punching, embossing, pressing, deep drawing, flanging or folding and leveling.

The invention is basically suitable for any type of metallic gasket, for example, for cylinder head gaskets or manifold gaskets or other flange gaskets. The gasket layers in such gaskets are often at least partially provided with a feed on one or both surfaces. Regardless of the spacers can be formed on uncoated, partially coated or fully coated gasket layers. In particular, in the case of partially coated gasket layers, it is preferred to provide the spacers in uncoated areas.

The invention can be applied both for single-layer gaskets as well as for multi-layer gaskets. In the case of single-layer flat gaskets spacers may be provided on both surfaces of the single gasket layer or even on one of the surfaces. In the case of a multilayer flat gasket, the at least one spacer is located on at least one of the outwardly facing surfaces, that is to say one of the surfaces of the gasket, which are oriented toward one of the mating surfaces to be sealed. On the other hand, no spacers are required on the surfaces of the inner gasket layers and on the surfaces of the outer gasket layers which point towards the interior of the gasket. To simplify the production, it is preferred if spacers are present on only one of the two outer surfaces of the flat gasket. in principle It is also possible that a spacer is formed in an inner layer and protrudes through an opening in the overlying outermost gasket layer over the sealing surface and thus performs its function.

The spacers are located in areas of the gasket layers, which are applied in the installed state of the seal substantially not squeezing with sealing surfaces. In other words, the spacers are located in areas of the gasket layer in which no sealing elements essential for the sealing function are present and where they can not affect the sealing effect of the metallic flat gasket. Suitable areas in which spacers may be located, for example, outer edge regions of the seal, which are still in the installed state of the seal between the sealed Cegenflächen, or even cantilevered areas that protrude laterally beyond the mating surfaces to be sealed. However, suitable positions for spacers may also be located in the inner region of the seal, namely, for example, in intermediate opening regions beyond the respective sealing elements. Particularly advantageous for integration of the spacers in the inner region of the seal is to integrate the spacers according to the invention into fluid holes. The spacer has an opening whose cross-section is suitably adapted to the passage volume of the liquid opening.

The number of spacers on an outer surface depends basically on the type and size of the metallic flat gasket. In general, it is preferable to provide a plurality of spacers per outer surface and to distribute them expediently along the outer contour of the sealing surface and optionally also in its interior. The height of the spacers is determined essentially by the height of the gasket layer protruding sealing elements such as beads, elastomeric applications or the like, as well as the type of installation tool used during installation of the seal. The height of the spacer should be so large that a reliable separation of the stacked flat gaskets is ensured by the installation tool, but on the other hand by an excessive height of the spacer, the function of the sealing elements within the metallic gasket is not compromised.

If there are a plurality of spacers on an outer surface of the metallic flat gasket, they may be of the same or different design. From a manufacturing point of view, it is preferred if all spacers which project beyond the same outer surface are of similar construction.

In a variant of the invention, the spacer can be shaped out as a cup-shaped or napfsegmentartiger projection of the gasket layer. While the cup-like projection ring-shaped in is formed closed, the cup-segment-like projection has a floor plan in the form of a ring segment with a circumferential angle of less than 360 °. While the cup-like projection can be located anywhere in the non-pressed region of the gasket layer, the cup-segment-like projection is expediently arranged on the edge of the metallic gasket layer or on the edge of a through-opening. The part missing the cup-segment-like projection to form a self-contained cup-like projection is virtually cut off from the edge of the sealing layer so that only one segment with a circumferential angle of less than 360 ° remains on the sealing layer. Preferably, this remaining on the gasket layer segment has a circumferential angle of at least 150 °. The plan of the cup-like projection can basically have any self-contained shape. Preferred are circular or oval floor plans, but also polygonal floor plans are conceivable. The layout of the napfsegmentartigen projection is corresponding to a section of said self-contained forms.

According to the napf (segment) like projection is formed out of the material of the gasket layer that its flank rises at least partially so steeply from the gasket that the projection of a corresponding napf (segment) like projection of another, identically manufactured gasket layer (Or in the case of single-layer seals a further flat gasket in total) can not be fully absorbed if it is congruent to the first gasket layer (flat gasket) is placed. Due to the very steep hiring of the flank of the napf (segment)-like protrusion is thus prevented that similar gasket layers or gaskets when stacking without a sufficient distance to keep each other slip into each other. In the case of the cup-like or napfsegmentartigen spacers of the invention, therefore, at most an upper portion of the cup is received in the bowl inside an adjacent seal. As a result, the outer surfaces of adjacent seals at least in the area around the cup-like spacers at a distance from one another. A sticking together of the seals or gaskets in this area is thereby effectively prevented. This embodiment offers, as a side effect, improved stacking safety.

In order to prevent a nap (segment) like projection is completely absorbed in another napf (segment) like projection, it is basically sufficient if only at least a portion of the napf (segment) like projection has a sufficiently large edge steepness , For example, in the circumferential direction of a cup-like projection steep alternate with less steep edge portions, the transition between these areas is preferably continuous and not abruptly. However, projections with constant edge steepness are preferred. Suitable slopes are generally achieved when the angle between see outer edge and sealing layer is at least 90 °, preferably between 90 and 100 ° and in particular between 90 and 95 °. The angle is expediently smaller than 100 °, even with changing steepnesses, at least in sections of great steepness.

The cup-like or napfsegmentartige projection can be made for example by punching, pressing or deep drawing of the material of the gasket layer. Also suitable is a method that is actually used to connect multiple metallic layers and referred to as "toxins". The generation of tox points is described for example in DE 29614430 U1. The cylindrical die of the Tox-joining tool described therein can be used analogously instead of joining several layers for deep drawing the cup-like or napfsegmentartigen projection in only a single gasket layer.

[001 7] The cup-like or nap-shaped projection may have a closed bottom, or else the bottom is provided with an opening. The latter variant is preferred because the perforated cup or the perforated cup segment can be produced more easily. In the case of closed soils, there is a risk that cracks in the material may be created during the production of the very steep flanks and the bowl may be torn. Accordingly, the size of the opening is expediently chosen so that there is no cracking in the cup-like projection or in the napfsegmentartigen projection during manufacture. Suitably, the diameter of the opening between 25 and 70%, more preferably between 40 and 60%, of the outer diameter of the cup base. The shape of the opening is basically arbitrary. From a manufacturing point of view, however, circular openings are preferred. The opening is expediently arranged centrally in the cup bottom. Such spacers according to the invention are preferred for integration in fluid holes.

As already mentioned, the size of the spacers in the flat gasket according to the invention depends mainly on the dimensions of the surface over which protrude the spacers, and the number of spacers on this surface. From these aspects and from a production point of view, outer diameters of the cup-shaped projection of 3 to 10 mm and in particular of 4 to 8 mm are preferred. These sizes are particularly suitable for metallic cylinder head gaskets, which are particularly suitable as gaskets of the invention. The material for the gasket layer, from which the spacers are formed, is useful for the production of cylinder head gaskets or the other aforementioned flat gaskets usually related metal, such as spring steel.

In order to prevent that the opening edge in the bottom of the cup-like projection digs into the counter surface to be sealed or when stacking and stacking an adjacent flat gasket Scratched, the edge area is vaulted around the opening in the bottom of the napf (segment) -like projection expedient toward the interior. This can be done for example by impressing a slope in this area. This operation is expediently carried out during a grading process, which is often carried out anyway in the production of a metallic flat gasket.

In a second variant of the invention, the spacer is formed on the basis of a tab which has been separated from the gasket layer leaving a connecting portion. On the one hand, the spacer can be produced from this tab so that the tab is folded back on itself or on the gasket layer. The folding process can be carried out so that the folded-over flap section rests essentially over the entire surface of the substrate. The height of the spacer then corresponds to the thickness of the gasket layer. A greater height of the spacer can be achieved in that the folded-back flap portion has a distance from the substrate. In this case, either a U-shaped fold can be formed which has substantially parallel legs over its entire length, or the distance to the base is greater in the region of the bending edge than towards the end of the folded leg. In this way, a so-called α-fold would be formed. Depending on the selected distance, the height of the spacer can be adjusted.

Another way of adjusting the height of the spacer results from the fact that an elevation is formed in the tab. This survey can be generated in principle as the cup-like projection, so for example by embossing, deep drawing or pressing. The form of the survey is basically arbitrary. However, it is preferred to form a survey in the form of a bead, which expedient extends across the entire width of the tab.

In order to prevent the survey is completely absorbed by a corresponding elevation of another, identically manufactured gasket layer or gasket when it is placed congruently on the first gasket layer / flat gasket, the flanks of the survey are again at least partially formed as steep, that superimposed, similar gasket layers / flat gaskets can not come to rest on the entire surface. With regard to the formation of the flanks here is basically the same thing that has already been carried out to the cup-like projections.

The dimensions of the tab in all the variants described above are suitably chosen so that the tab does not break when crimping or generating the survey and sufficient material for producing a sufficiently large spacer is available. The production of the tab-like spacer can also be simplified in that the tab is not only separated from the gasket layer, but at the same time along its outer edge Recess is introduced into the gasket layer. The connecting portion over which the tab hangs on the gasket layer, of course, is retained. Suitably, the recess is formed substantially U-shaped. Accordingly, the flap itself U- or tongue shape. This has the advantage that the tab end has no sharp corners, but is rounded. In order to further reduce the risk of damage to the sealed Cegenflächen or adjacent flat gaskets by sharp edges of the spacer, it is also preferred to einbölben the edge region of the tab at least in sections. Appropriately, at least the tab sections are arched, which can come into contact with the sealed Cegenfläche or adjacent stacked flat gaskets. The concavity is expediently such that the edge of the arched tab portion is displaced from the outer surface of the gasket layer toward the interior. The Einwölbungsvorgang is expediently made again in a planing step in the production of the metallic flat gasket.

The invention will be explained in more detail with reference to drawings. The drawings merely show a few exemplary embodiments of the invention, but without the invention being restricted to these examples. Modifications that come within the scope of the appended claims are readily possible. The drawings also have a purely schematic character. In the drawings show:

Figure 1 is a plan view of a metallic flat gasket according to the invention on the example of a cylinder head gasket; Figure 2 shows an embodiment of a flat gasket according to the invention in an enlarged view of the section A of Figure 1;

Figure 3 is a cross-section taken along the line B-B of Figure 2;

Figure 4 shows another embodiment of a flat gasket according to the invention in an enlarged view of the section A in Figure 1;

Figure 5 is a cross-section along the line C-C of Figure 4;

Figure 6 shows two superimposed flat gaskets according to Figure 5 in a partial cross section; FIG. 7 shows a further exemplary embodiment of a metallic flat gasket in an enlarged view of the region A in FIG. 1;

Figure 8 is a cross-section along the line D-D of Figure 7;

Figure 9 shows two superimposed flat gaskets according to Figure 8 in partial cross section; 10 shows a further embodiment of a flat gasket according to the invention in partial view of

Area A in Figure 1; Figure 11 is a cross-section along the line EE of Figure 10; FIG. 12 shows a further exemplary embodiment of a metallic flat gasket in an enlarged view of the region A in FIG. 1;

Figure 13 is a cross-section taken along line F-F of Figure 12; 14 shows a cross section along the line C - G of FIG. 12 and FIG. 15 shows a further exemplary embodiment of a metallic flat gasket in an enlarged view of the region A in FIG. 1.

Fig. 1 shows a plan view of a cylinder head gasket 1 as an example of a metallic flat gasket. The cylinder head gasket 1 consists of a single metallic gasket layer 2, here made of spring steel. Apart from the above the surface 3 of the gasket layer 2 projecting spacer 4 corresponds to the cylinder head gasket 1 in all other respects a conventional cylinder head gasket. In addition to four combustion chamber openings arranged in series, it has 9 screw openings 10, as well as oil and water openings 11 and a chain box opening 12. The sealing elements, of which the openings 9, 1 1 and 12 are sealed, are not shown here, but completely correspond to the conventional in the prior art. In addition, the surface 3 is provided in areas around the openings 9 to 12 and the sealing edge in a known manner partially with a plastic coating, which is not reproduced here.

The cylinder head gasket 1 is to be automatically inserted by means of a robot between an engine block and a cylinder head. The automatic installation requires that only a single seal is removed and installed from a stack of cylinder head gaskets 1 arranged one above the other. This, in turn, requires that the individual cylinder head gaskets 1, which are congruently stacked one above the other, not adhere to one another but can easily be lifted apart from one another by the robot. In order to make this possible, a plurality of spacers 4 are arranged along the outer edge of the gasket layer 2. These spacers 4 prevent overlapping cylinder head gaskets 1 from coming to lie over one another over the entire surface and sticking to one another. In the case shown, four spacers 4 are distributed along the outer edge of the gasket layer 2, namely two spacers at the two ends of the upper longitudinal edge of the gasket layer 2 in FIG. 1 and the two remaining spacers 4 in the region of the lower longitudinal edge, slightly further inwardly offset.

Fig. 2 shows the designated A region in Fig. 1 in an enlarged view. In the description of these and all subsequent figures, like parts with the same reference numerals as in Fig. 1 are designated. The spacer 4 shown in Fig. 2 is formed in the form of a tab 6. The tab 6 is formed out of the gasket layer 2 and connected to it in the region of the connection. section 61 still connected. So that the tab 6 can be bent out of the gasket layer, a U-shaped recess 8 is first stamped into the gasket layer 2. The punching process can be carried out simultaneously with the punching of the remaining passage openings in the gasket layer 2. As can be seen from FIG. 3, the tab 6 is bent back onto the gasket layer 2 such that the folded leg 62 maintains a distance d from the gasket layer 2. This has the advantage that the bending edge 63 is not bent too much and thereby possibly tearing. In addition, the height of the spacer 4 can be varied according to the setting of the distance d.

Fig. 4 shows another example of a spacer 4 based on a release of the gasket layer 2 tab 6. The tab 6 is again surrounded by a U-shaped recess 8. Running across the entire width of the tab 6 is a bead 7 embossed. As can be seen from FIG. 5, the two bead flanks 71 and 72 rise substantially vertically from the gasket layer 2 into the air. The angle α between the outer bead flank and the gasket layer is therefore about 90 °. If one stacked two identically shaped cylinder head gaskets 1 one above the other, the steepness of the bead flanks 71 and 72 results in that the bead 7 can not be completely absorbed by the bead 7 'of the adjacent cylinder head gasket 1'. This is shown in FIG. 6. Only the uppermost crest area of the bead 7 disappears inside the bead 7 'of the overlying cylinder head gasket 1'. However, this is sufficient for a position fixation of the two seals 1 and T one on top of the other. According to the relatively large height h of the bead 7, the two gasket layers 2 and 2 'of the two cylinder head gaskets 1 and 1' are not directly adjacent to each other, but in the area around the beads 7 and 7 'at a distance a to each other. Both seals are therefore not the whole area against each other and are therefore easy to separate in an automatic installation.

Fig. 7 shows again the section A of Fig. 1 with a further example of a spacer 4. This spacer 4 is a cup-like projection 5, which has in its bottom 52 has a circular opening 53 which is centered in the Region of the bottom 52 is arranged. The cup-shaped projection 5 itself also has a circular crack in the crumb. As in the case of the seal according to FIGS. 4 to 6, the flank 51 of the cup-shaped projection 5 is also formed very steeply here and extends at an angle α of approximately 90 ° to the gasket layer 2 (see FIG. 8). In the case of LJ stacking of similar seals 1, this results in that a cup-shaped projection 5 can not be completely received by a cup-shaped projection 5 ^{1 of} a seal arranged adjacent thereto. As a result, the adjacent gasket layers 2 and 2 'are spaced apart from each other (see FIG. 9). Figures 10 and 11 show a further embodiment of a flat gasket according to the invention, which is similar to the variant according to figures 7 to 9. Here, the cup-like projection 5 is pushed so far to the edge of the gasket layer 2 that only one segment of the cup is located within the gasket layer 2. The formed on the gasket layer 2 spacer 4 therefore has the shape of a cup segment with a ring-segment-shaped plan, with the ends 55 and 56 of the ring segment are located at the edge of the gasket layer 2. Otherwise, the napfsegmentartige projection 5 corresponds to the cup-like projection of the seal according to Figures 7 to 9. The flank of the cup-segment-like projection rises again at an angle of 90 ° from the gasket layer 2 up. When stacking several seals to each other, therefore, results in the same result as in the self-contained cup-like projections, even if the spacer stands up here only in the manner of a local half-bead to the sealing edge.

Figures 12 to 14 illustrate an embodiment of a flat gasket according to the invention, which is similar to that of Figures 7 to 9. Here, however, the cup-like projection 5 is not in the edge region of the gasket layer 2, but more in the interior of the gasket, adjacent to a combustion chamber opening 9. The opening in the bottom of the cup-like projection 5 serves here simultaneously as a fluid passage 11 for oil or cooling water. Accordingly, the opening cross-section is chosen so that the required fluid flow can be ensured. In contrast to the embodiment of Figures 7 to 9, the edge 51 of the cup-like projection 5 in the circumferential direction here has a changing slope. FIG. 13 shows a region of reduced steepness as a cross section along the line F-F, and FIG. 14 shows a region of greater steepness as a cross section along the line G-G. Correspondingly, the angle (X in Figure 13 is greater than that in Figure 14. Only one half of the cup-shaped projection is shown in each case The area of the cup-like projection on the other side of the opening 53 in the bottom 52 (which in turn corresponds to the opening 11 here The transition between the two regions of different slope is continuous and jump-free.

The napfsegmentartige projection 5 opens here but not to the edge of the gasket layer, but to the edge of the fluid opening 11. The ends 55 and 56 of the napfsegmentartigen projection therefore come to lie on the edge of the fluid opening 11. Otherwise, the spacer 4 corresponds to that described in connection with FIGS. 10 and 11.

Claims

1 . Metallic flat gasket (1) having at least one metallic gasket layer (2) which has at least one spacer (4) formed out of the material of the gasket layer (2) on at least one of its outwardly facing surfaces (3). 2) is arranged, which in the installed state of the seal (1) is substantially not acted upon by sealing surface pressure, characterized in that the spacer (4) is selected from: a) a cup-like or napfsegmentartigen projection (5) whose flank (51) rising at least in sections so steeply from the gasket layer (2) that it is placed on a corresponding cup (segment) like projection (5 ¹ ) another, identically manufactured gasket layer (2 ¹ ), which is congruent to the first gasket layer (2), can not be fully absorbed, or b) one of the gasket layer (2) leaving a connection portion (61) free Tab (6), the b1) is folded back on itself or on the gasket layer (2) or in which b2) is formed a survey (7) whose flanks (71, 72) at least partially so steep from the gasket layer (2) rise, that they of a corresponding elevation (7 ¹ ) of another, identically manufactured gasket layer (2 ¹ ), which is placed congruently on the first gasket layer (2) can not be fully absorbed.

2. Flat metal gasket according to claim 1, characterized in that the cup (segment) like projection (5) in its bottom (52) has an opening (53).

3. A flat metal gasket according to claim 2, characterized in that the edge region (54) around the opening (53) to the interior of the napf (segment) like projection (5) is arched out.

4. Flat metal gasket according to claim 2 or 3, characterized in that the diameter of the opening (53) between 25 and 70%, in particular between 40 and 60%, of the outer diameter of the bottom (52) of the napf (segment) like projection (5 ) is.

5. Flat metal gasket according to one of claims 2 to 4, characterized in that the opening (53) is a fluid opening (11).

6. Flat metal gasket according to one of the preceding claims, characterized in that the cup (segment) like projection (5) has an outer diameter of 3 to 10 mm, in particular 4 to 8 mm.

7. Metallic flat gasket according to one of the preceding claims, characterized in that the cup-segment-like projection (5) has a ring-segment-shaped plan and extends in particular over a circumferential angle of greater than 150 °.

8. A metallic flat gasket according to claim 7, characterized in that the cup-segment-like projection (5) in the outer edge region of the gasket layer (2) o- in the outer edge region of a fluid opening (11) extends such that the two ends (55, 56) of the ring segment come to rest on the edge of the gasket layer (2) or on the edge around the fluid opening (11).

9. Flat metal gasket according to claim 1, characterized in that the tab (6) in b1) is folded back so that the folded-over area (62) rests essentially over the whole area on the gasket layer (2).

10. Metallic flat gasket according to claim 1, characterized in that the tab (6) in b1) is folded back so that the folded portion (62) at least in the region of the bending edge (63) has a distance (d) to the gasket layer (2) ,

11. Flat metallic gasket according to claim 1, characterized in that the elevation in b2) is a bead (7).

12. A metallic flat gasket according to claim 10, characterized in that the bead (7) extends transversely over the entire width of the tab (6).

13. Metallic flat gasket according to one of claims 9 to 11, characterized in that the edge region of the tab (6) is at least partially curved so that the edge of the tab portion facing away from the mating surface.

14. Metallic flat gasket according to one of claims 9 to 12, characterized in that the tab (6) to produce this, apart from the connecting portion (61), surrounding recess (8) is free.

15. A metallic flat gasket according to claim 13, characterized in that the recess (8) is formed substantially U-shaped.

16. Flat metal gasket according to one of claims 1 to 8, characterized in that the flanks (51, 71, 72) of the spacer (4) has a height (h) between 0.2 and 3 mm, in particular between 0.5 and 2 mm, own.

17. Metal flat gasket according to one of claims 1 to 8 or 16, characterized in that the flanks (51, 71, 72) of the spacer (4) have sections of different slope, wherein the transition between sections of great steepness and less steepness preferably takes place continuously ,

18. Flat metal gasket according to one of claims 1 to 8 or 16, characterized in that the flanks (51, 71, 72) of the spacer (4) over their entire length have a constant slope.

19. A metallic flat gasket according to one of claims 1 to 8 or 16 to 18, characterized in that the angle (<x) between the outer flank (51, 71, 72) and the gasket layer (2) at least in sections of great steepness not greater than 100 ° is and in particular between 90 and 95 °.

20. Flat metal gasket according to one of the preceding claims, characterized in that a plurality of spacers (4) on the gasket layer (2) and in particular in the outer edge region are present.

21. Flat metal gasket according to one of the preceding claims, characterized in that the at least one gasket layer (2) in the area acted upon by the sealing surface pressure is at least partially provided with a coating, in particular with a plastic coating.

22. Flat metal gasket according to one of the preceding claims, characterized in that the at least one spacer (4) in a region of the gasket layer (2) is present, which is not provided with a coating.

23. Flat metal gasket according to one of the preceding claims, namely a single-layer gasket.

24. Flat metal gasket according to one of the preceding claims, namely a cylinder head gasket.