Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02670191 2015-12-03
- 1-
CYLINDER HEAD GASKET
BACKGROUND OF THE INVENTION
The invention relates to a cylinder head gasket with a gasket plate having a
plurality of combustion chamber openings and comprising a single sheet metal
layer extending at least substantially over the entire gasket plate, a
respective
opening edge area, enclosing the respective combustion chamber opening, of
the sheet metal layer being folded over and back onto the sheet metal layer in
order to fomi a combustion chamber sealing element for the respective
combustion chamber opening, so that each combustion chamber sealing
element has a foldover flange facing a foldover base area of the sheet metal
layer, edge areas of the sheet metal layer being folded over and back onto the
sheet metal layer in order to form cylinder head supporting elements at a
spacing from an area of the gasket plate containing the combustion chamber
openings, and at least one elastomeric sealing bead for sealing around at
least
one fluid opening of the gasket plate being attached to the sheet metal layer.
In particular, the invention relates to a cylinder head gasket in which a shim
element which encloses the combustion chamber opening is arranged between
the foldover flange and the foldover base area of a combustion chamber
sealing element.
Such cylinder head gaskets are disclosed in EP-0 557 918-A of ELRING
DICHTUNGSWERKE GMBH, and also in EP-0 713 988-A.
A 0
CA 02670191 2009-06-25
1
- 2 -
The designer of a cylinder head gasket who has been given the task of
designing the cylinder head gasket for a specific engine has to deal with a
number of problems:
In modern engines which are of weight-saving construction, the engine block,
and, above all, the cylinder head, are, in areas thereof, not particularly
resistant to deformation. Since the compressive forces with which the cylinder
head gasket is clamped between the engine block and the cylinder head are
applied at points, namely by the cylinder head bolts, these compressive forces
are highest in the areas of the cylinder head bolts and can drop significantly
in
the areas between the cylinder head bolts (referred to hereinbelow as
intermediate bolt areas). This applies, above all, to intermediate bolt areas
in
which or in the vicinity of which the engine block and/or the cylinder head is
or
are not particularly resistant to deformation owing to cavities such as
combustion chambers and cavities for coolant or engine oil. Above all, in the
areas of the compression chamber sealing elements for sealing off against the
highest pressures, namely the gas pressure of the combustion gases, an
excessive drop in the compressive forces acting on the cylinder head gasket
can cause the engine to become untight.
A further problem has to be taken into account in so-called liner engines, in
which the area of the combustion chambers lying in the engine block is formed
by cylinder liners inserted into the engine block. The following constructions
are known from the prior art for fixing a cylinder liner in its axial
direction in an
engine block: In a first type of cylinder liner, the latter has, at its one
axial end
area facing the cylinder head, adjacent to its axial end face, a ring collar
with
which the liner is placed on a ring-shaped shoulder of the engine block - in
the
area of this ring-shaped shoulder, the diameter of the engine block cavity
accommodating the liner widens abruptly, i.e., this cavity has a larger
diameter in its end area facing the cylinder head than beyond this shoulder.
CA 02670191 2009-06-25
- 3 -
In technical terminology, such liners are called top stop liners.
Two further known types of cylinder liner are referred to as mid stop liner
and
bottom stop liner. In the first case, the liner is supported in a central area
of
its axial length on the engine block, in the second case in its bottom, axial
end
area facing away from the cylinder head.
When in the course of assembly of a liner engine, the cylinder head is mounted
and the cylinder head bolts are tightened, the liners are biased in axial
direction owing to the high compressive forces acting in the area of the
combustion chamber sealing elements on the cylinder head gasket, which are
introduced into the liners. Since the liners cannot be regarded as absolutely
rigid components, the biasing forces in mid stop and bottom stop liners act on
relatively long axial sections of the liners, and so these can spring back
over
their entire circumference or only in circumferential areas when, during
operation of the engine, upon ignition of a cylinder, in the area thereof, the
cylinder head moves away from the engine block to some extent or in the
intermediate bolt areas, circumferential areas of the liners are pressed less
strongly in axial direction than in the areas adjacent to the cylinder head
bolts.
Therefore, mid stop liners and bottom stop liners can make a certain
contribution towards evening out the compressive forces acting on the cylinder
head gasket around the combustion chamber openings, not only when the
engine is out of operation, but also when the engine is in operation.
In the past, the complex problems surrounding cylinder head gaskets were
usually solved by cylinder head gaskets whose gasket plate is formed by
several sheet metal layers arranged one on the other, at least one of which
consists of sheet spring steel and has sealing beads which are spring-
elastically deformable in their height around combustion chamber openings.
CA 02670191 2009-06-25
- 4 -
For cost reasons, an attempt was made to replace these multilayer cylinder
head gaskets by single layer gaskets of the kind defined at the outset, as
also
described in EP-0 557 918-A and EP-0 713 988-A.
However, the inventors of the present invention have ascertained that these
known cylinder head gaskets are not without complications with respect to
their manufacture, and depending on the construction of the engine to be
sealed off, they are unable to reliably guarantee the necessary sealing-off,
above all, around the combustion chambers, in particular, when the engine is
in operation.
The object underlying the invention was to create cylinder head gaskets of the
kind defined at the outset, which are uncomplicated to manufacture and, are
basically designed so as to also be readily adaptable to different engine
constructions, in particular, to so-called liner engines of the various types
described hereinabove. In particular, this object is to be accomplished for
larger engines, as are used in commercial vehicles.
SUMMARY OF THE INVENTION
For cylinder head gaskets of the kind defined at the outset with a shim
element, enclosing the respective combustion chamber opening, between
foldover flange and foldover base area of the respective combustion chamber
sealing element, it is proposed, in accordance with the invention, that the
shim
element be configured as a shim sheet of spring steel having a bead which is
resiliently elastic in its height and encloses the respective combustion
chamber
opening, and the sheet metal layer substantially forming the gasket plate be
made from a metal sheet without spring steel properties. The following
advantages are thereby gained:
CA 02670191 2009-06-25
- 5 -
If the sheet metal layer substantially forming the gasket plate does not
consist
of sheet spring steel, but of a more ductile and, consequently, more easily
shapeable sheet steel, the foldovers around the combustion chamber openings
and the foldovers serving to form supporting elements are much easier to
manufacture than when a sheet of spring steel is used, which has to be heated
in the area of the bending radius of the foldover to be produced, in order to
be
able to fold over the sheet metal. In addition, if a sheet of spring steel is
used,
a relatively broad foldover flange of a combustion chamber sealing element
can only be produced without crack formation at the free edge of the foldover
flange if the sheet metal is also previously heated in that area which later
forms the free edge of the foldover flange, in order that it will lose its
spring
steel properties. In addition, sheets of spring steel are considerably more
expensive than sheets of steel without spring-elastic properties. For engines
without cylinder liners or with liners cast into the engine block (often also
called crankcase) or with top stop liners, in which it is not possible to
exploit
the axial elasticity of a biased liner in the mounted state of the cylinder
head
gasket, in this solution in accordance with the invention, the height
elasticity of
the bead of the shim sheet of spring steel is used to even out the pressing of
the combustion chamber sealing element around the combustion chamber
opening and to also ensure the sealing effect of the combustion chamber
sealing element during operation'of the engine when during the highest gas
pressure prevailing in a combustion chamber (the so-called ignition pressure)
the area of the sealing surface of the cylinder head lying above the
combustion
chamber sealing element is at a greater distance from the area of the sealing
surface of the engine block lying under the combustion chamber sealing
element than in areas in the vicinity of cylinder head bolts.
Particularly advantageous embodiments of such a cylinder head gasket in
accordance with the invention are characterized by one or both of the
following
features: The height of the bead of the shim sheet of spring steel is from
_
- ---
CA 02670191 2009-06-25
- 6 -
approximately 50 Wo to approximately 100 % of the thickness of the material
of the shim sheet, and the thickness of the material of the shim sheet lies in
the order of magnitude of from one tenth to two tenths of the thickness of the
material of the sheet metal layer substantially forming the gasket plate. A
bead with a height in the area indicated above can, on the one hand, be
produced without any difficulty in a sheet of spring steel, and ensures, on
the
other hand, a height elasticity of the combustion chamber sealing element,
which is sufficient for fulfilling its sealing function, and with a shim sheet
with a
relatively small material thickness, too large a thickness of the combustion
chamber sealing element (in the pressed state) is avoided, which would
otherwise lead to problems in other areas of the cylinder head gasket serving
sealing purposes or to an inadequate supporting of the cylinder head by the
cylinder head supporting elements in the so-called hinterland of the gasket
plate - hinterland areas of the gasket plate are to be understood as areas
which are at a considerable distance from a combustion chamber sealing
element or from the combustion chamber sealing elements, and, in particular,
are peripheral areas of the gasket plate.
A second type of cylinder head gasket in accordance with the invention differs
from the above-described type of cylinder head gasket in accordance with the
invention in that the shim element is a shim sheet which has a bead, but may
also be beadless, and like the sheet metal layer substantially forming the
gasket plate consists of a metal sheet without any spring steel properties.
Such a type of gasket is suitable for engines which are sufficiently resistant
to
deformation in the intermediate bolt areas of engine block and/or cylinder
head and either have no cylinder liners or liners which do not show or are
unable to show the spring-back effect described above, but whose end face
facing the cylinder head gasket does not sink either during engine operation.
In this type of gasket the shim sheet serves to increase the compressive
CA 02670191 2009-06-25
- 7 -
forces acting on the combustion chamber sealing element when the cylinder
head gasket is mounted; however, since neither the shim sheet nor the sheet
metal layer accommodating it consists of sheet spring steel, the combustion
chamber sealing element has a so-called height adaptation capability, which
means that when mounting the cylinder head gasket and/or while the engine
is in operation, the thickness of the combustion chamber sealing element,
owing to the area-wise differently sized compressive forces acting on the
combustion chamber sealing element, is changed area-wise by a plastic
deformation of the combustion chamber sealing element and thus adapts to
the area-wise different width or height of the so-called sealing gap - the
sealing gap is to be understood as the gap between the sealing surfaces of the
cylinder head and the engine block or the cylinder liners, which is to be
sealed
by the cylinder head gasket.
For this type of gasket, too, it is advantageous for the thickness of the
material of the shim sheet to lie in the order of magnitude of one tenth or
two
tenths of the thickness of the material of the sheet metal layer.
The above-described second type of cylinder head gasket in accordance with
the invention may also be modified in accordance with the invention by the
combustion chamber sealing elements not containing any shim sheet. Such a
modified cylinder head gasket is suitable for liner engines in which the
cylinder
liners project relatively far over the sealing surface of the engine block
that
faces the cylinder head gasket, i.e., exhibit a large so-called liner
projection,
and, in particular, for engines with mid stop liners or bottom stop liners
with a
sufficiently large liner projection, as the liner projection then assumes the
function of the shim sheet, namely that of elastically increasing the
compressive forces acting on the combustion chamber sealing element.
_ ..
CA 02670191 2009-06-25
- 8 -
A third type of cylinder head gasket in accordance with the invention does not
have a shim sheet in the combustion chamber sealing elements either, but its
sheet metal layer made from sheet metal without spring steel properties is
provided in the foldover base area with a bead which encloses the respective
combustion chamber opening, projects in the direction towards the foldover
flange and, owing to the absence of a shim sheet, is immediately adjacent to
this foldover flange. A combustion chamber sealing element of such design has
an even better height adaptation capability as the bead can be flattened
plastically, and, nevertheless, such a cylinder head gasket in accordance with
the invention can be manufactured in an extremely cost-effective manner as it
requires neither a shim sheet nor use of expensive spring steel.
As is apparent from the above, the cylinder head gaskets in accordance with
the invention are particularly well suited for liner engines, and the gaskets
are
then advantageously so designed that when the cylinder head gasket is
mounted, its combustion chamber sealing elements rest on the upper end
faces, i.e., the sealing surfaces, of the cylinder liners.
It should also be noted that an engine with a mid stop liner is to be
understood
as an engine in which the axial spacing of the liner sealing surface of a
liner
from that point at which the liner is supported on the engine block
corresponds
to at least one third of the axial length of the liner.
Further features, advantages and details of the invention will become apparent
from the appended claims and/or from the following description of preferred
embodiments of the cylinder head gasket in accordance with the invention
shown in the accompanying drawings and the engine constructions that are
particularly well suited for these.
CA 02670191 2009-06-25
- 9 -
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a plan view of part of a first embodiment of a cylinder
head gasket in accordance with the invention;
Figure 2 shows a section taken along line 2-2 in Figure 1;
Figure 3 shows the detail "A" from Figure 2 on a larger scale;
Figure 4 shows a section taken along line 4-4 in Figure 1, but through an
embodiment of the cylinder head gasket in accordance with the
invention, which has been modified in relation to the first
embodiment;
Figures 5-7 show representations of a third, fourth and fifth embodiment of
the cylinder head gasket in accordance with the invention, which
correspond to Figure 3; and
Figures 8-10 show parts of an engine block, a cylinder liner and a cylinder
head gasket in a section taken along a diameter plane of a
combustion chamber; Figure 8 shows a top stop liner, Figure 9 a
mid stop liner and Figure 10 a bottom stop liner; a sixth
embodiment of the cylinder head gasket in accordance with the
invention is shown in all three Figures.
DETAILED DESCRIPTION OF THE INVENTION
The cylinder head gasket shown in Figure 1 comprises a gasket plate 10 with
combustion chamber openings 12, bolt holes 14 for the passage of cylinder
head bolts, and fluid passage openings 16 of different configuration and
CA 02670191 2009-06-25
- 10 -
arrangement for the passage of coolant or lubricating oil. For the sake of
completeness, mention is made of the fact that the cylinder head gasket may
have further openings, for example, for the passage of locating pins or
screws,
and also further fluid passage openings, for example, a passage opening for
coolant between adjacent combustion chamber openings. It is also pointed out
that cylinder head gaskets in accordance with the invention are provided, in
particular, for larger commercial vehicle engines, as is the case with the
cylinder head gasket shown in Figure 1, which has eight bolt holes 14 around
the left-hand combustion chamber opening 12 in accordance with Figure 1 - in
smaller engines, in particular, for passenger cars, a cylinder head gasket
usually has only four bolt holes around a combustion chamber opening.
As will be apparent from the following, the gasket plate 10 of the cylinder
head
gasket in accordance with the invention has only a single sheet metal layer 20
extending over the entire gasket plate. In the embodiment shown in Figure 1,
the sheet metal layer 20 has been folded over and back onto itself around
each combustion chamber opening 12 for formation of a combustion chamber
sealing element 22, whereby a so-called foldover is formed, whose cross
section corresponds approximately to a lying U - in this connection reference
is made to the following explanations.
In the embodiment of the cylinder head gasket in accordance with the
invention shown in Figure 1, the gasket plate 10 is provided at its periphery
with a further foldover extending around the circumference of the gasket
plate, in order to thereby form a cylinder head supporting element 24.
Depending on the engine construction, several short supporting elements may,
however, be sufficient, which, in particular, are arranged at the longitudinal
ends, i.e., the narrow sides, but possibly also at one of the two longitudinal
sides or at both longitudinal sides of the gasket plate 10. Alternatively or
additionally, a cylinder head gasket in accordance with the invention may,
CA 02670191 2009-06-25
- 11 -
however, also be provided with cylinder head supporting elements which lie in
the interior of the gasket plate 10, i.e., within its circumferential edge.
For
example, such supporting elements may be provided at some or all bolt holes
14 by an edge area of the gasket plate 10 that encloses a bolt hole or
segments of such an edge area being folded over and back onto the sheet
metal layer forming the gasket plate 10. Alternatively or additionally, such
supporting elements may be provided at any location on the gasket plate 10
by a, for example, U-shaped, punched cut - in a plan view of the cylinder head
gasket - being made in the sheet metal layer and a thus obtained metal
tongue being folded over onto the sheet metal layer.
Around fluid passage openings 16 or groups of such passage openings, a
cylinder head gasket of the kind shown in Figure 1 has sealing elements
formed by elastomeric sealing beads 26 which have been applied to one or
both sides of the sheet metal layer forming the gasket plate 10 and then
solidified (for example, vulcanized).
The section (taken along line 2-2 in Figure 1) shown in Figure 2 through the
cylinder head gasket in accordance with Figure 1 shows a sheet metal layer
100 which substantially forms the gasket plate 10 and extends over the entire
gasket plate (which the exception of its openings). Figure 2 shows that
sealing
around the fluid passage opening 16 is effected by elastomeric sealing beads
26 which have been applied to both sides of the sheet metal layer 100 and
solidified there. Figure 2 also shows details of the combustion chamber
sealing
element 22 and the cylinder head supporting element 24.
In order to form the combustion chamber sealing element 22, an, in particular,
circular ring-shaped area of the sheet metal layer 100 was folded over through
1800 and back onto the sheet metal layer around the combustion chamber
opening 12 so as to produce a so-called foldover 30 which has a foldover
=
CA 02670191 2009-06-25
- 12 -
flange 30b above a foldover base area 30a. In order that the combustion
chamber sealing element 22 will project equally far over the two sides of the
adjacent flat area of the sheet metal layer 100, the sheet metal layer 100 was
provided with an offset 32 between this flat area and the combustion chamber
sealing element 22.
In the preferred embodiment of a combustion chamber sealing element in
accordance with the invention, an, in particular, also circular ring-shaped
shim
sheet 34, which is more clearly apparent from Figure 3, is inserted between
the foldover base area 30a and the foldover flange 30b. In accordance with
the invention, this shim sheet 34 consists of sheet spring steel, whereas a
sheet steel without spring steel properties was used for the manufacture of
the
sheet metal layer 100. The bead 36, therefore, forms a spring element which,
when the combustion chamber sealing element 22 is strongly pressed in the
vertical direction in accordance with Figure 3, can be compressed somewhat,
but, when the combustion chamber sealing element is pressed slightly, springs
up again and can then press the foldover flange 30b upwards in accordance
with Figure 3 to some extent - the bead 36 thus imparts to the combustion
chamber sealing element 22 certain spring-elastic properties in the vertical
direction in accordance with Figure 3. In addition, the thickness of the
combustion chamber sealing element 22 in the strongly pressed state is
increased somewhat by the shim sheet 34 (in comparison with embodiments
without a shim sheet), whereby the compressive forces acting on the
combustion chamber sealing element when the cylinder head gasket is
mounted are increased. As a result, this cylinder head gasket in accordance
with the invention has its greatest thickness around the combustion chamber
openings 12 - if the thickness of the gasket in the area of the sealing beads
26
is disregarded.
.õ,
CA 02670191 2009-06-25
- 13 -
Also for formation of the cylinder head supporting element 24, the sheet metal
layer 100 was provided with a foldover 40, but the supporting element 24, in
contrast to the combustion chamber sealing element 22, does not contain any
inlay or shim sheet. Between the supporting element 24 and the adjacent flat
area of the sheet metal layer 100, the latter was, however, also provided with
an offset 42.
In this embodiment of the cylinder head gasket in accordance with the
invention, its thickness in the area of the combustion chamber sealing
elements 22 is greater than in the area of the supporting element 24 (or other
similar cylinder head supporting elements), but less than in the areas of the
elastomeric sealing beads 26, which can already be deformed by relatively low
compressive forces and only have to be protected against excessive
deformations - this task is assumed by the combustion chamber sealing
elements 22 and the supporting element (or the supporting elements) 24.
In the modification, shown in Figure 4, of the cylinder head gasket in
accordance with Figures 1 to 3, a cylinder head supporting element is missing
in the area, shown in Figure 4, of the periphery of the gasket plate 10.
Instead, in this modification the sheet metal layer 100 is provided around the
bolt hole 14 shown in Figure 4 with a cylinder head supporting element 46
which encloses the bolt hole 14. For formation of the supporting element 46,
the sheet metal layer 100 was provided with a foldover corresponding to the
foldover 40 of the supporting element 24. Several foldover segments which
are spaced from one another along the circumference of the bolt hole 14 and
are formed by folded-over sheet flaps of the sheet metal layer 100 could also
be substituted for a circular ring-shaped foldover 46.
_ _
CA 02670191 2009-06-25
- 14 -
The modifications, shown in Figures 5 to 7, of the combustion chamber sealing
element 22 in accordance with Figures 2 and 3 will be described hereinbelow
only insofar as these modifications differ from the combustion chamber sealing
element 22 in accordance with Figures 2 and 3.
Figure 5 shows a sheet metal layer 100', which is provided with a combustion
chamber sealing element 22' and is to consist of a sheet steel without spring-
elastic properties. Inserted in the foldover 30' serving to form the
combustion
chamber sealing element 22' is a shim sheet 34', which is overall flat and may
also consist of a sheet steel without spring-elastic properties. In this
embodiment, the combustion chamber sealing element 22' has no elastic
properties in the direction of its height, however, when mounting the cylinder
head gasket and/or when the engine is in operation, the combustion chamber
sealing element 22' as well as the area of the sheet metal layer 100' forming
the foldover 30' can be deformed plastically to some extent in the vertical
direction in accordance with Figure 5 and thereby enable a so-called height
adaptation.
The embodiment in accordance with Figure 6 differs from that in accordance
with Figure 5 only in that the combustion chamber sealing element 22" of the
sheet metal layer 100" does not contain any inlay within the foldover 30",
i.e.,
it is without a shim sheet. The two embodiments in accordance with Figures 5
and 6 thus differ only in that the embodiment in accordance with Figure 6 has
a combustion chamber sealing element 22" of lesser thickness.
Finally, the embodiment in accordance with Figure 7 differs from that in
accordance with Figure 6 only in that a foldover base area 30a" of the
combustion chamber sealing element 22' has a bead 36" enclosing the
combustion chamber opening 12. In accordance with the invention, the bead
36" like the bead 36 (see Figure 3) projects in the direction towards the
CA 02670191 2009-06-25
- 15 -
foldover flange 30b" of the combustion chamber sealing element 22', but,
since the sheet metal layer 100" is not to consist of sheet spring steel, it
does
not have any elastic properties in the direction of its height, but can be
flattened plastically at least to some extent when the cylinder head gasket is
being mounted and/or the engine is in operation.
Figures 8 to 10 show parts of an engine block 300, 300' and 300",
respectively, a cylinder liner 302, 302' and 320", respectively, and a
cylinder
head gasket 304, 304' and 304", respectively, in accordance with the
invention, which is shown only in a very simplified manner. An axis of the
combustion chamber surrounded by the liner was indicated by 12a in each of
Figures 8 to 10. Moreover, in all three embodiments, a combustion chamber
sealing element 322, in accordance with the invention, of the cylinder head
gasket rests on the respective liner, and elastomeric sealing beads 326 of the
cylinder head gasket lie over the engine block.
The cylinder liner 302 of the embodiment in accordance with Figure 8 is a so-
called top stop liner; it has an upper so-called liner collar 302a, which
adjoins
an upper end face 302b, forming a sealing surface, of the liner 302, and with
which the liner is supported on a shoulder 300a of the engine block 300, which
is lower in relation to a sealing surface 300b of the engine block, more
specifically, to such an extent as to produce a so-called liner projection B
through which the end face 302b of the liner 302 projects over the sealing
surface 300b of the engine block 300.
The embodiment in accordance with Figure 9 differs from that in accordance
with Figure 8 only in that the liner 302' is supported on the engine block
300'
at a considerable spacing from its upper end face 302b', more specifically, by
a
shoulder 302a' which rests on a shoulder 300a' of the engine block. In such a
CA 02670191 2009-06-25
- 16 -
so-called mid stop liner, the spacing between the shoulder 302a' and the end
face 302b' is, for example, from approximately one third to approximately half
of the total axial length (not shown) of the liner 302'.
Finally, the embodiment in accordance with Figure 10 differs from that in
accordance with Figure 9 only in that the shoulders 300a" and 302a" are
arranged in the proximity of the bottom end of the liner 302", which is why
such a liner is referred to as bottom stop liner.
When an engine has been completely assembled in accordance with the
embodiments shown in Figures 9 and 10, that longitudinal area of the liner
302' and 302", respectively, which is located above the shoulder 302a' and
302a", respectively, is biased in axial direction, i.e., in the direction of
the
combustion chamber axis 12a, and, for example, when the engine is in
operation, can expand elastically to some extent in a vertical upward
direction
when ignition pressure in the combustion chamber associated with the liner
causes the area of the cylinder head located above the combustion chamber to
be pressed upwards to some extent, and without this elastic longitudinal
expansion of the liner, the combustion chamber sealing element 322 would
otherwise be relieved to too great an extent. In the case of a mid stop liner
or
a bottom stop liner, it may, therefore, be possible to dispense with designing
the combustion chamber sealing element in such a way that it has elastic
properties in the direction of its thickness or height.
As mentioned above, cylinder head gaskets in accordance with the invention
are provided, in particular, for engines of commercial vehicles. Particularly
well
suited are cylinder head gaskets in accordance with the invention, in which
the
foldover flange of a combustion chamber sealing element has a width (with
respect to the combustion chamber opening in radial direction) which is at
CA 02670191 2009-06-25
- 17 -
least 6 mm and preferably lies in the range of between 6 and 8 mm. As
explained above, it is not possible or only possible with a relatively great
amount of expenditure to produce such wide foldovers on sheet spring steel.
When mention is made hereinabove of the fact that the sheet metal layer
substantially forming the gasket plate and possibly a shim sheet are formed by
metal sheets, it is not to be excluded that these metal sheets have on one or
either side, allover or only in areas thereof a coating which, in particular,
consists of an elastomeric material (such thin elastomeric coatings are known
in metallic cylinder head gaskets and usually serve the purpose of so-called
microsealing in the event that an opposite metallic sealing surface is not
completely flat but has a certain surface roughness and/or pores).
Above all, steel sheets having an elongation at break of at least 20 %, in
particular, at least 30 AD (elongation at break in accordance with A80,
defined
in European standard EN 10088-2, which is also a DIN standard) are suitable
for the sheet metals without spring steel properties that are to be used in
accordance with the invention.
