Patent Application
20140333036
The invention relates to a flat gasket comprising an at least substantially metallic gasket plate, which has at least two gasket layers arranged on each other and in which at least one through-opening to be sealed is formed, the gasket plate comprising at least one supporting device which increases the total material thickness of the gasket plate in areas thereof and is formed by several folded-over gasket layer sections.
The gasket plate or its layers do not have to be purely metallic, i.e., consist of sheet metal layers, but rather one or both sides of at least one or even all of the gasket layers could be provided entirely or partially with a coating which serves for so-called microsealing, reduction of sliding friction and/or protection against corrosion.
The invention relates, in particular, to a flat gasket adapted to a flange connection of an exhaust pipe of an internal combustion engine, in particular, a flat gasket which is fitted in a flange connection of an exhaust gas recirculation line, on an exhaust gas turbocharger or between an exhaust manifold and a cylinder head.
A flat gasket of the kind mentioned at the outset is disclosed in DE 102 13 900 A. This gasket is configured as a cylinder head gasket in which at least one gasket layer consists of a spring-steel sheet and has a height-elastic sealing bead which encloses a combustion chamber through-opening, but may also run along the outer edge of the gasket plate. In this known cylinder head gasket, the supporting device is configured as a so-called stopper, which is associated with and immediately adjacent to the sealing bead in order to protect the sealing bead during installation and operation of the cylinder head gasket against undesired excessive flattenings which are detrimental to a permanent sealing function of the bead. The gasket layer sections forming a stopper, which are of tongue-shaped configuration and were folded over around their respective tongue root or are of strip-shaped configuration and were folded over along a longitudinal edge of the respective gasket layer section, are all components of one and the same gasket layer, which may be the so-called functional layer provided with the sealing bead or a so-called stopper layer of the gasket plate of this cylinder head gasket.
With a flat gasket of the kind in question sealing is effected between two sealing surfaces, facing each other, of two adjacent components, in particular, between two flanges of a flange connection, which form between them a so-called sealing gap accommodating the flat gasket and are clamped against each other usually by means of assembly screws, so that the flat gasket is pressed between the component sealing surfaces. The two components or flanges can, however, also be connected to each other by means of other known connecting and clamping means and pressed against the flat gasket. The aforementioned components may, for example, be a cylinder head and an exhaust manifold adjacent thereto (in this case, the flat gasket forms an exhaust manifold gasket) but they may also be the parts of a flange connection between two sections of an exhaust gas pipe or other components which are to be tightly connected to one another and in the connecting area of which the issuing of fluid has to be prevented by the flat gasket, which is critical, above all, in the exhaust gas area of an internal combustion engine owing to the high temperatures prevailing there. Since the pressing forces acting on the installed flat gasket are usually applied only more or less at points (above all, when assembly screws are used) and the components accommodating the flat gasket between them cannot be regarded as absolutely rigid parts in any application, there are usually considerable local fluctuations in the pressing forces acting on the installed flat gasket: Without special measures, these pressing forces are greatest at and in the immediate vicinity of the assembly screws or other connecting means and decrease as the spacing from the connecting means increases, i.e., in the case of assembly screws, they are smallest halfway between two adjacent assembly screws. However, locally different component stiffnesses and locally different thermal expansions occurring during operation in the components accommodating the flat gasket between them also influence the pressing forces acting on the installed flat gasket—all this results, without special measures, in the width of the sealing gap accommodating the installed flat gasket being locally different in size, as a rule, between the components. It is, therefore, known to form the stoppers associated with height-elastic sealing beads with a height which is variable along the stopper and to counteract deformations in the component sealing surfaces accommodating a flat gasket between them by supporting elements provided on the flat gasket, which form supporting devices for the component sealing surfaces accommodating the flat gasket between them and do not have the function of a deformation limiter/stopper for a height-elastic bead.
The following problem may, however, also arise during operation with flange connections in a longer pipeline or between a heavier module such as, for example, an oil filter or a turbocharger, and a unit carrying this module, such as an internal combustion engine: Owing to shocks, vibrations or the like, but also to thermal expansions which differ with respect to location and/or time, without special measures, the topography of the sealing gap which is formed by the flange sealing surfaces facing each other and accommodates the flat gasket, undergoes change with respect to location and time, and, under certain circumstances, the flat gasket is unable to adapt to these changes in the sealing gap topography and is, therefore, unable to compensate for the changes in the sealing gap topography. This applies, above all, when, as is the case in the exhaust gas area of an internal combustion engine, the flat gasket is subjected to high operating temperatures and then no longer has any appreciable spring-elastic properties even when classic spring-steel sheets were used for one or more layers of the flat gasket, as is the case, for example, in metallic cylinder head gaskets, for the spring-steel properties in classic spring steels are already drastically reduced at approximately 400° C. Without special measures, the flange connections can then become untight under the described operating conditions.
The object underlying the invention was to propose flat gaskets of the kind defined at the outset, with which supporting devices of locally different effective height can be simply and cost-effectively achieved. In this case, a supporting device can be a stopper associated with a sealing bead, i.e., a deformation limiter for the sealing bead, a device for delimiting or minimizing deformations of the sealing surfaces of components such as flanges between which the flat gasket is clamped, but also a supporting device by means of which the topography of the sealing gap accommodating the flat gasket is at least substantially stabilized.
To accomplish this object, it is proposed, in accordance with the invention, to so configure a flat gasket of the kind defined at the outset that the gasket plate has at least one first gasket layer with at least one first layer area in which the first gasket layer has a first layer thickness and in which at least one first folded-over gasket layer section of a supporting device is formed, and that the gasket plate has at least one second gasket layer with at least one second layer area in which the second gasket layer has a second layer thickness and in which at least one second folded-over gasket layer section of this supporting device is formed, the first and second layer thicknesses being different from each other and this supporting device, therefore, having different total material thicknesses and, consequently, different effective heights in areas thereof.
It is easiest to use flat materials of different thickness for the first and second gasket layers (i.e., uncoated sheet metals, sheet metals coated on one side or sheet metals coated on both sides in any combination), as gasket layer sections of different thickness and, consequently, different effective height then result automatically because the gasket layer sections formed by the one gasket layer have a different layer thickness than the gasket layer sections formed by the other gasket layer, but embodiments are preferred in which the first and second gasket layers comprise sheet metal layers of sheet metals of different sheet thickness.
In accordance with the invention, the flat gasket can, however, also be so configured that one or both of the gasket layers is or are provided with coatings of different thickness in areas thereof or the gasket layer sections or some of the gasket layer sections were subjected to a stamping operation for changing the sheet metal thickness in areas thereof, which, in view of the relatively small surface area of such a gasket layer section, is possible with considerably lower stamping forces than the stamping of a height profile in a stopper which is not interrupted in its longitudinal direction.
DE 102 13 900 A does mention that a stopper associated with a sealing bead can have a height profile along the bead, which is to be achieved by the stopper being formed by folded-over gasket layer sections having different heights, so that the stopper height varies in the longitudinal direction of the bead. However, how these different heights are to be achieved is not described, and since in this known cylinder head gasket all of the folded-over gasket layer sections forming a stopper are produced from one and the same gasket layer and, therefore, initially must all have the same original layer thickness, it is assumed that the different heights are created by stamping the folded-over gasket layer sections or gasket layer sections to be folded over.
If the gasket plate has a gasket layer with a, possibly height-elastic, bead, a supporting device in accordance with the invention can be associated with and adjacent to this bead (in a plan view of the gasket plate) in order to protect the bead from an undesired high degree of flattening during installation and operation of the flat gasket. The bead can be a common sealing bead, which runs around a fluid through-opening (e.g. a combustion chamber opening, an exhaust gas through-opening or a through-opening for coolant or engine oil) but, for example, also a bead enclosing a screw hole for the passage of an assembly screw. In the case of a sealing bead enclosing a fluid through-opening, a supporting device in accordance with the invention can be advantageously arranged radially outside of the sealing bead, either to form a stopper immediately adjacent to the sealing bead or to form a so-called hinterland support—in this case, the supporting device is arranged at a distinct spacing from the sealing bead, more specifically, in such a way and in such a configuration that it stabilizes the sealing gap topography during operation and/or counteracts the deformation of the sealing surfaces of components accommodating the flat gasket between them, for example, the deformation of the flanges of a flange connection lying in the exhaust gas area of an internal combustion engine. A hinterland support is typically arranged at the periphery of the gasket plate, where several supporting devices in accordance with the invention may be provided, for example, in the area of the two longitudinal ends of an elongate flat gasket. However, depending on the kind of use and configuration of the flat gasket, the supporting device can, in this case, also act as stopper for the sealing bead.
The folded-over gasket layer sections of one of the gasket layers could all be folded over onto the latter and lie against this gasket layer, and the latter could be arranged inside a multilayered gasket plate, as shown in the drawings of DE 102 13 900 A. However, the folded-over gasket layer sections of one of the gasket layers could also lie on another gasket layer and/or be located on an outer side of the gasket plate. It is, in particular, possible to provide the gasket layer sections, which are to be folded over, of one of the gasket layers at the periphery of the gasket plate and to then fold them over in such a way that they engage over the outer edge of an adjacent gasket layer and rest on the latter. Alternatively, at least one of the gasket layer sections, which are to be folded over, of a gasket layer can be arranged at a spacing from the periphery of the gasket plate and pass through a cutout in an adjacent gasket layer and be folded over onto the latter.
If the gasket layer sections of a supporting device in accordance with the invention lie on a first outer side of the gasket plate and are formed by a gasket layer which forms the second outer side of the gasket plate and the folded-over gasket layer sections of which engage over the first outer side of the gasket plate, the folded-over gasket layer sections can also ensure that the multilayered gasket plate is held together and additional measures for connecting the gasket layers to one another can, therefore, be dispensed with.
As in the cylinder head gasket disclosed in DE 102 13 900 A, in a flat gasket in accordance with the invention it is also possible for at least some of the gasket layer sections to be of strip-shaped configuration and folded over at a longitudinal edge of the respective gasket layer section. However, for formation of a supporting device having a height profile, embodiments are preferred in which at least some of the gasket layer sections are of tongue-shaped configuration and folded over around the respective tongue root—the gasket layer sections can then be of relatively narrow configuration in the longitudinal direction of the supporting device so that with them a height profile is achieved, the height of which changes at relatively short intervals in the longitudinal direction of the supporting device.
If a supporting device in accordance with the invention is desired, the height profile of which has not only two different effective heights, this can be brought about by some of the folded-over gasket layer sections being made to undergo a possibly only partial stamping operation before or after the folding-over, but in the case of a gasket plate having more than two gasket layers, it is simpler to produce more than two gasket layers from layers of different thickness and to form the supporting device from folded-over gasket layer sections of more than two gasket layers. Further alternatives will be described hereinbelow.
In preferred embodiments of the flat gasket in accordance with the invention, at least one supporting device—in a plan view of the gasket plate—is of elongate configuration (i.e. it has a general shape with a larger length than width) and is formed by at least two folded-over gasket layer sections lying one behind the other in the longitudinal direction of the supporting device (which is not necessarily to be equated with immediately following each other), the total material thicknesses of the gasket plate in the areas of at least two gasket layer sections being different from each other. Accordingly, such a supporting device has a height profile extending in the longitudinal direction thereof, which owing to its formation by folded-over gasket layer sections need not be a height profile with a continuous course and a constant change in the profile height. As is clear from the above, the easiest way to achieve such a height profile is for the layer thicknesses of at least two gasket layer sections to be different from each other.
In preferred embodiments of the flat gasket in accordance with the invention, a supporting device is formed by at least two first folded-over gasket layer sections provided in the longitudinal end areas of the supporting device and at least one second folded-over gasket layer section provided in a central area of the supporting device, the total material thicknesses of the gasket plate in the areas of the first gasket layer sections and in the area of the second gasket layer section being different from one another. Such a supporting device may, for example, in its longitudinal end areas have a larger or a smaller effective height than in its central area.
As mentioned above, with the use of connecting means provided only locally such as, for example, assembly screws, pressing forces applied only more or less at points result, without special measures, in a sealing gap accommodating the flat gasket, the width of which is smallest in the area of the connecting means and largest in central areas lying between the connecting means. Therefore, especially such embodiments of the flat gasket in accordance with the invention are recommended, in which an elongate supporting device extends between the positions of two connecting means, in particular, between two screw holes for the passage of assembly screws, and the total material thickness of the supporting device in areas near the connecting means is less than in a central area of the supporting device lying between these areas.
The basic principle of the invention can also be advantageously achieved by the gasket plate comprising at least one thicker and one thinner gasket layer, and the supporting device comprising at least two gasket layer sections of the thicker gasket layer, a first gasket layer section of which is folded over onto the thicker gasket layer and a second gasket layer section of which is folded over onto the thinner gasket layer. In this case, the effective height of the supporting device in the area of the first folded-over gasket layer section is equal to the thickness of the thicker gasket layer less the thickness of the thinner gasket layer, and in the area of the second folded-over gasket layer section equal to the thickness of the thicker gasket layer. In such an embodiment, the thinner gasket layer can extend only as far as the free edge of the first folded-over gasket layer section or as far as the free edges of the folded-over first gasket layer sections, but embodiments are preferred, in which the thinner gasket layer has a recess which—in a plan view of the gasket plate—accommodates the folded-over first gasket layer section at least substantially, and so the total material thickness formed by the thicker and thinner gasket layers in the area of the folded-over second gasket layer section is larger by the layer thickness of the thinner gasket layer than in the area of the folded-over first gasket layer section. If, in such a case, in a multilayered gasket plate, only the thicker gasket layer has folded-over gasket layer sections, a supporting device with two different effective heights can nevertheless be achieved. If, on the other hand, two gasket layers of different thickness have folded-over gasket layer sections, even a supporting device with three different effective heights can be achieved.
Furthermore, an increase in the effective heights of a supporting device in accordance with the invention can be achieved by at least one gasket layer in the area of at least one gasket layer section being folded over not only once, i.e., through approximately 180°, but by the gasket layer section itself being folded over in areas thereof once more or several times, so that the gasket layer section has in cross section the shape of a flat lying U or, for example, the shape of a flat S, which, above all, can be readily achieved on a relatively thin gasket layer.
In particularly preferred embodiments of flat gaskets in accordance with the invention, the gasket layers extend with folded-over gasket layer sections at least substantially over the entire gasket plate.
Further features, advantages and details of the invention are given in the appended drawings and/or the following description of several particularly advantageous embodiments of the flat gasket in accordance with the invention.
The flat gasket in accordance with the invention, shown in
In accordance with the invention, the two gasket layers 16, 18 are, in the present case, substantially congruent, and each gasket layer has a sealing bead 16a and 18a, respectively, stamped in the sheet metal, which, in a plan view of the gasket plate 10, lie one on top of the other and enclose the exhaust gas through-opening 12 in the shape of a circular ring. In the embodiment shown, the two sealing beads 16a, 18a are so-called full beads of approximately circular arc-shaped or trapezoidal cross section, however, the sealing beads could also have any other cross-sectional shape known to one skilled in the art from the prior art, for example, these could be so-called half-beads. Also preferred is a configuration of the gasket such that each gasket layer 16, 18 has a flat section between its sealing bead 16a, 18a and the edge of the exhaust gas through-opening 12, with these flat sections also lying against each other like those areas of the two gasket layers 16, 18 lying radially outside of the sealing beads 16a, 18a when the gasket is installed and pressed. Differently from shown in
The gasket plate 10 is provided with two supporting devices 20 and 22 in accordance with the invention, each of which has an elongate basic shape, in the preferred embodiment shown, is arranged at the periphery of the gasket plate 10, extends, in each case, over the major part of an essentially elongate gasket plate area lying radially outside of the sealing beads 16a, 18a and, in the illustrated case, lies between the two screw holes 14, and each of which consists of several segments, in the illustrated case, of four segments, which are formed by folded-over gasket layer sections of the two gasket layers 16, 18. Only the supporting device 22 is explained in detail hereinbelow, but the same applies to the other supporting device 20.
The segments, shown in
The two gasket layers 16 and 18 of the gasket plate 10 are held together by the folded-over gasket layer sections 181 and so no further connecting means are required.
Each of the two supporting devices 20 and 22 has two end areas, each of which, in the illustrated case, is adjacent to one of the screw holes 14 and is formed by a thinner, folded-over gasket layer section 181, and a central area which is formed by two thicker gasket layer sections 161, and so each supporting device has a height profile which in the two end areas of the supporting device has a lower height than in its central area.
In accordance with the invention, the two supporting devices 20, 22 can fulfill two functions:
Primarily, the two flanges 30 and 40 of the flange connection (see
In accordance with the invention, the total material thickness of the gasket plate 10 in the areas of the folded-over gasket layer sections 161, 181 is larger than outside of the areas of the folded-over gasket layer sections or the supporting devices 20 and 22 by the material thickness of the gasket layer 16 or by the material thickness of the gasket layer 18, respectively. The effective heights of the supporting device are, therefore, equal to the material thickness of the gasket layer 16 or the gasket layer 18, respectively, and less than the sum of the heights of the undeformed sealing beads 16a and 18a.
The section shown in
Some alternative configurations of flat gaskets in accordance with the invention will now be explained with reference to
This supporting device in accordance with the invention, only individual segments of which are shown in
Of the two gasket layers 70 and 72 of the gasket plate shown partially in
In
In the area of this embodiment shown in
In accordance with the invention, the following further modifications are possible and under certain circumstances advantageous: In the embodiment shown, the thicker gasket layer 90 has a screw hole 90′ for each assembly screw 102, while the thinner gasket layer 92 terminates before the shaft of each assembly screw 102 (seen from the gasket layer 92 to the outer edge of the flange connection). It is, however, also possible to also allow the thicker gasket layer 90 to terminate before the shaft of each assembly screw 102. Such modifications of the gasket plate of the flat gasket in accordance with the invention may result in slight deformations of the shafts of the assembly screws, but, on the other hand, the advantage is achieved that the effective heights of supporting devices in accordance with the invention are further graduated—in comparison with embodiments in which the height profiles of supporting devices in accordance with the invention are only determined by folded-over gasket layer sections. These modifications also allow the distribution of the pressing forces applied by the assembly screws 102 to be additionally influenced by the sealing gap accommodating the flat gasket. Merely for the sake of completeness, it is also pointed out that the illustration of the deformations of the flanges and the topography of the sealing gap is also exaggerated in
As is clear from the above description, the appended drawings and the attached claims, a basic concept of the invention is to be seen in that a flat gasket in accordance with the invention comprises at least two gasket layers having material thicknesses which differ from each other, and folded-over gasket layer sections are provided on at least one of these layers, more specifically, preferably on the gasket layer having the greater material thickness. Alternatively, the folded-over gasket layer sections could, however, also be provided on the gasket layer having the lesser material thickness, and at least one of these gasket layer sections is then folded over several times.
In preferred embodiments of the flat gasket in accordance with the invention, comprising at least two gasket layers, one of which has a larger layer thickness than the other, the layer thickness of the thicker gasket layer is from 1.2 to 1.6 times the layer thickness of the thinner gasket layer, in particular, from 1.25 to 1.5 times the layer thickness of the thinner gasket layer.
The difference between the layer thicknesses is preferably from approximately 0.05 to 0.1 mm.
Particularly recommendable is an inventive configuration in the case of multilayered flat gaskets having at least two gasket layers of different layer thickness, in which the layer thickness of the thinner gasket layer is from approximately 0.18 to 0.22 mm and, in particular, approximately 0.2 mm, and the layer thickness of the thicker gasket layer is from approximately 0.22 to 0.32 mm and, in particular, from 0.25 to 0.30 mm.
When mention is made hereinabove of two gasket layers arranged on each other or on top of each other, this is not to be understood as meaning that the two gasket layers must be immediately adjacent to each other, although such embodiments are preferred. It is possible for another gasket element such as a further gasket layer to also be arranged between the two gasket layers in question.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102012100919.8 | Feb 2012 | DE | national |
The present application is a continuation of international application number PCT/EP2013/051938, filed on Jan. 31, 2013, which claims priority to German application number 10 2012 100 919,8, filed on Feb. 3, 2012, the entire specification of both being incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2013/051938 | Jan 2013 | US |
| Child | 14446472 | US |
