Flat metal gasket

Abstract

A metal gasket is proposed, especially a cylinder head gasket for a combustion engine, which comprises a sealing plate having a combustion chamber through-hole, a deformation-limiting device lying adjacent to the combustion chamber through-hole and respectively one top and one bottom layer. The deformation-limiting device is configured as a symmetrical bead in relation to the top and bottom layers. A protrusion preferably provided with a radius is orientated towards one of the top and bottom layers and opposite thereto a depression facing the other of the top and bottom layers is provided which is surrounded by two raised portions projecting opposite the surface of the sealing plate. A filling is accommodated in the depression.

Description

[0001] The invention relates to a metal gasket, in particular a cylinder head gasket for a combustion engine with a sealing plate having a combustion chamber through-hole, and with a deformation-limiting device lying adjacent to the combustion chamber through-hole and a top and bottom layer.

[0002] In DE 42 19 709 A1 are described metal gaskets in various embodiments. One of the disclosed gaskets contains a deformation-limiting device which is formed as the crimping-over of an annular portion of the sealing plate at the combustion chamber through-hole. During the crimping process, a part of the annular portion which has a reduced material thickness by comparison with the sealing plate, is laid round over itself so that the deformation-limiting device is formed by a doubling of the reduced material thickness.

[0003] If a sealing plate provided in this way with a deformation-limiting device or stopper is used as the middle layer between two cover plates with beads, and the three-layer seal thus formed is pressed together, the pressing forces are transferred in an uneven manner, such that the load alleviation of the cover plates is uneven.

[0004] Asymmetrical beads filled with a resin or the like are also generally known (see U.S. Pat. No. 5,582,415).

[0005] In EP 0 747 614 A1 is disclosed a metal cylinder head gasket which has two outer cover plates with beads and a support plate disposed between same, which are provided with one or more combustion chamber through-holes. Adjacent to the beads of the cover plates is provided a deformation-limiting device around the combustion chamber through-hole at the supporting plate, which device is provided with rounded portions on the surfaces facing the cover plates.

[0006] The object underlying the invention is to create a metal gasket of this type, which with a simple set-up applies uniform pressure and has improved, adaptable deformation behaviour.

[0007] This object is achieved according to the invention by the characterising features of the main claim in conjunction with the features of the preamble.

[0008] Because the deformation-limiting device is configured as a bead which is symmetrical in respect of the top and bottom layers, in such a way that a protrusion is oriented towards one of the layers and lying opposite a depression facing the other of the two layers is provided, which is surrounded by two raised portions protruding opposite the surface of the sealing plate, a filling being accommodated in the depression, the stopper which is usually provided in prior art can be dispensed with or the stopper layer is replaced by the symmetrical bead. Furthermore, uniform compression is possible and the bottom and top layers are uniformly relieved of pressure. Through the special shape of the bead in conjunction with the filling, it adapts to the engine topography during fitting, being adjustable in compression to a preset degree.

[0009] Through the measures quoted in the subordinate claims, advantageous developments and improvements are possible.

[0010] It is particularly advantageous that the protrusion of the bead is provided with a radius or a convexity, by which means the surface pressure can be increased. By pre-determining the amount of the filling in the depression or respectively the width and height of the filling and/or through the size of the radius, which can change after pressing into a straight line, deliberate pressure control can be undertaken and the adaptation to the engine can be set, by which means its dynamics and the sealing gap oscillations can be reduced.

[0011] Altogether the symmetry of the bead produces a uniform distribution of the force from the beads of the bottom and top plates.

[0012] One embodiment of the invention is represented in the FIGURE and is described in greater detail in the following description. The sole FIGURE shows a section through a gasket according to the invention.

[0013] The metal gasket 1, partially represented in the FIGURE and which in this embodiment is a cylinder head gasket of a combustion engine, has a sealing plate 2 with a top layer or a cover plate 3 and a bottom layer or a bottom plate 4. The cover and bottom plates 3, 4, which are generally produced from a spring steel, are each provided with a bead 5, 6. A bead 7 acting as a deformation-limiting device in the sealing plate 2 is disposed adjacent to a combustion chamber through-hole 8, which surrounds the combustion chamber 8.

[0014] The bead has a protrusion 9 facing the bottom plate 4 with a radius or a bead convexity, the height of which, extending from the surface of the sealing plate 2 to the apex of the protrusion 9, is referred to as a. The embodiment represented shows the gasket in the uncompressed state. In relation to the surface of the sealing plate 2, the protrusion 9 is surrounded by two recessed counterbored holes 10, 11 or respectively delimited by same, which preferably have a depth of a in respect of the surface of the sealing plate 2.

[0015] Opposite the protrusion 9, a depression 12 is formed in the surface of the sealing plate 2, the depression 12 being enclosed by two raised portions 13, 14 which project opposite the surface of the sealing plate 2 and the height of which has the dimension a in respect of the surface of the sealing plate. The depression 12, which preferably has a depth of 2a, is completely or partially filled with a projecting filling 15 which is designated as a “hard coating” and which consists of a thermosetting plastic and/or thermoplastic material, interspersed with filling material. This filling 11 largely prevents compression of the depression 12 during deformation into a seal and provides an additional attenuation of the deformation behaviour of the bead 7. In another embodiment, the filling can also be configured as a metal film or the like.

[0016] Bead 7 is produced by compression moulding in a mould, displacement of the material of the sealing plate taking place as a result of the protrusions and depressions of the bead 7. The filling 15, the height and width of which is adjustable, can be produced in a screen printing process or be applied with a dispenser.

[0017] A filling configured as a metal film can e.g. be hot-pressed in.

[0018] The adaptation of the gasket 1 to the engine topography during fitting can be deliberately set by the radius of the protrusion 9 and by the level of filling, i.e. by the height and width of the filling 15, the radius being able to change into a straight line during fitting.

[0019] The bead 7 is designated as symmetrical since the height of the raised portions 13, 14 is substantially equal to the height of the protrusion 9. Through the symmetry of the bead 7, during fitting there is even distribution of the force of the beads 5 and 6 of the cover and bottom plates 3, 4. Naturally the cover plate 3 can be replaced by a bottom plate 4 and the other way round, or a plurality of top and bottom layers can be provided.

Claims

1. Metal gasket, in particular a cylinder head gasket for a combustion engine, with a sealing plate having at least one combustion chamber through-hole, a deformation-limiting device lying adjacent to the combustion chamber through-hole and at least one each of a top layer and a bottom layer, characterised in that the deformation-limiting device is configured as a bead (7) which is symmetrical in respect of the top and bottom layers (3, 4), in such a way that a protrusion (9) is oriented towards one of the top and bottom layers (3, 4) and lying opposite this is provided a depression (12), facing the other of the top and bottom layers (3, 4) and which is surrounded by two raised portions (13, 14) projecting opposite the surface of the sealing plate (2), a filling being accommodated in the depression (12).

2. Gasket according to claim 1, characterised in that the protrusion (9) is provided with a radius or a convexity.

3. Gasket according to claim 1 or claim 2, characterised in that the height of the protrusion (9) provided with a radius or a convexity in respect of the surface of the sealing plate corresponds substantially to that of the raised portions (13, 14) delimiting the depression (12).

4. Gasket according to one of claims 1 to 3, characterised in that the protrusion (9) provided with a radius or a convexity is delimited by two counterbored holes (10, 11) recessed opposite the surface of the cover plate (2).

5. Gasket according to one of claims 1 to 3, characterised in that the amount of filling (15) in the depression (12) is selected in dependence on the desired deformation behaviour.

6. Gasket according to one of claims 1 to 4, characterised in that the deformation behaviour can be adjusted via the size of the radius or the convexity of the protrusion (9).

7. Gasket according to one of claims 1 to 5, characterised in that the filling (15) has a filler and a thermosetting plastic and/or a thermoplastic material or is configured as a metal foil.