Patent Application
20200191272
The invention relates to a cylinder-head gasket with a metal sealing layer in which there are provided at least one combustion-chamber opening (associated with a cylinder of a reciprocating internal combustion engine) and screw holes around said opening for the passage of cylinder-head screws, and a combustion-chamber sealing bead stamped into the sealing layer; the combustion-chamber sealing bead has, on its convex side, a crest portion which extends in the bead longitudinal direction and is arranged, along the combustion-chamber sealing bead, in a plan view of the sealing layer between two bead legs, or, in a cross-section through the bead, above or below two bead legs, by means of which bead legs the crest portion is connected to regions of the sealing layer bordering the combustion-chamber sealing bead, into which regions the bead legs transition in each case by a bead foot; in a plan view of the sealing layer the screw holes are arranged at a spacing from the combustion-chamber opening and at spacings from one another in the peripheral direction of the combustion-chamber opening and the combustion-chamber sealing bead runs between the combustion-chamber opening and the screw holes; the combustion-chamber sealing bead has screw portions, each of which lies closest to a screw hole, and intermediate portions between these screw portions.
In particular, the invention relates to a cylinder-head gasket of this kind having a single sealing layer.
A person skilled in the art is familiar with cylinder-head gaskets of this kind from the prior art.
As is also the case with known metal cylinder-head gaskets, the sealing layer of a cylinder-head gasket pertaining to the present invention may also be provided on one or both sides fully or partially with a coating of a non-metal or metal material, and therefore the sealing layer of the above-defined cylinder-head gasket does not have to be made purely of metal.
In particular, the invention relates to a cylinder-head gasket of the kind defined at the outset, which is a cylinder-head gasket for a multi-cylinder engine, more specifically for a multi-cylinder commercial vehicle engine. Lastly, it should also be noted that the invention relates above all to cylinder-head gaskets for diesel engines.
A cylinder-head gasket is always clamped between an engine block (also referred to as a crankcase) and a cylinder head of a reciprocating internal combustion engine, more specifically with the aid of cylinder-head screws, which pass through bores in the cylinder head and screw holes in the cylinder-head gasket and extend into bores in the engine block which are provided with threads. Since the clamping forces acting on the cylinder-head gasket consequently are introduced by the cylinder-head screws more or less at specific points into the sealing assembly comprising the cylinder head, the cylinder-head gasket and the engine block, and since the engine components constituted by the cylinder head and engine block do not form absolutely rigid components, the latter and the cylinder-head gasket are pressed en bloc in the regions of the cylinder-head screws, such that the sealing gap to be sealed there by the cylinder-head gasket and accommodating the cylinder-head gasket has its shortest height or smallest width between mutually opposed sealing faces of the two aforementioned engine components, however, since the height or width of the sealing gap becomes larger with increasing spacing (as seen in a plan view of the engine) from the cylinder-head screws on account of the fact that the engine components are not absolutely rigid and due to the reaction forces of the clamped cylinder-head seal, the pressing forces acting on the cylinder-head gasket decrease with increasing spacing from the cylinder screws; consequently, the sealing forces which are generated by a combustion-chamber sealing bead of constant geometry over its periphery, and which are effective between the combustion-chamber sealing bead and those regions of the sealing faces of the two aforementioned engine components between which the combustion-chamber sealing bead is clamped also decrease.
Under consideration of this fact, specifically that without special amounts in a cylinder-head gasket of the kind described at the outset the pressing forces acting on the combustion-chamber sealing bead of the installed cylinder-head gasket decrease in the intermediate portions of the combustion-chamber sealing bead with increasing spacing from the cylinder-head screws or screw holes, it is already known from the prior art, in order to equalize the sealing pressure generated by the combustion-chamber sealing bead of the installed cylinder-head seal, to provide the combustion-chamber sealing bead, at least in its aforementioned intermediate portions along the combustion-chamber sealing bead, with a height and/or width profile, more specifically in such a way that the rigidity, that is to say the deformation resistance of the combustion-chamber sealing bead to pressing forces oriented perpendicularly to the cylinder-head seal, varies in these intermediate portions. In this regard it should be noted that with a constant material thickness along the bead and over the bead cross-section and with constant material properties, the rigidity of a bead produced in a metal sealing layer of a cylinder-head gasket increases with increasing bead height with constant bead width (measured in a plan view of the sealing layer) along the bead, and decreases with increasing bead width with constant bead height along the bead.
With regard to the prior art, reference is made to DE 41 42 600 A1 in the name of Elring Dichtungswerke GmbH, which discloses a cylinder-head gasket with a metal sealing plate, in which an annular metal combustion-chamber sealing element with screw portions and intermediate portions arranged successively in alternation along the sealing element is inserted around a combustion-chamber opening; the sealing pressure generated by the installed cylinder-head gasket is equalized in that the intermediate portions of the combustion chamber sealing element, at least over part of their length, have a greater radial width and/or a greater height or thickness and/or a greater hardness than the screw portions. With regard to the hardness, DE 41 42 600 A1 merely discloses that the (entire) combustion-chamber sealing element has such a hardness profile along its periphery that, when the cylinder-head gasket is installed, an approximately constant sealing pressure is provided along the periphery of the combustion-chamber sealing element, more specifically on account of material properties, such as microstructural conditions, of the metal combustion-chamber sealing element that differ accordingly in different regions, for example as a result of the heat treatment of longitudinal portions of the combustion-chamber sealing element (nothing else can be inferred from the last paragraph of column 4 of DE 41 42 600 A1). In one embodiment of this known cylinder-head gasket the annular combustion-chamber sealing element is provided with a bead extending in its peripheral direction, with regard to which it is noted that the combustion-chamber sealing element is more deformable in the region of this bead than in a bead-free region (see column 7, lines 7 to 19).
In many engine constructions with a cylinder-head gasket of the kind mentioned at the outset, the installation space available for accommodating the combustion-chamber sealing bead is limited at least in some regions along this bead, more specifically above all with regard to the width of the combustion-chamber sealing bead. As is usual, also in the case of a cylinder-head gasket pertaining to the present invention, the combustion-chamber sealing bead is formed as what is known as a full bead with a bead crest (crest portion) and two bead legs, such that the cross-section of the combustion-chamber sealing bead is approximately rectangular or corresponds approximately to a trapezoid or approximately a U, wherein with all of these cross-sectional forms the transitions of the bead crest into the bead legs and the transitions, formed by the bead legs, of the bead feet into the regions of the sealing layer bordering the bead feet are preferably rounded. Thereby, when the cylinder-head gasket is installed, the combustion-chamber sealing bead can produce a sufficient sealing of the combustion-chamber gases all over along the bead, it is necessary for the bead crest and the bead feet to be acted on all over by pressing forces sufficient for a sufficient gas seal; this presupposes that, if the cylinder-head seal, at relatively short radial spacings from a combustion-chamber opening, has other openings such as a further combustion-chamber opening or one or more openings for the passage of cooling water or engine oil, at least there the width of the bead crest and/or the width of the sealing bead measured at the bead feet (in each case measured in a plan view of the cylinder-head seal) must be much smaller than the radial spacing of the edge of the combustion-chamber opening from each of these other openings. A limitation of the installation space available for accommodating the combustion-chamber sealing bead and a corresponding limitation of the bead width, however, is also provided if at least one of the engine components constituted by the cylinder head and engine block has a sealing face region in its component sealing face in the vicinity of an engine cylinder, in which sealing face region the component rigidity of this component is much lower in respect of pressing forces directed perpendicularly to its component sealing face than in sealing face regions of this component adjacent to this sealing face region, in particular on account of a cavity provided in this engine component, for example for cooling water or engine oil.
The object of the invention was now to develop a cylinder-head gasket of the kind described at the outset, which can be mass produced reliably and relatively easily and the combustion-chamber sealing bead of which is able to generate all over, with its bead crest and its bead feet, pressing forces that are sufficiently high for sealing off the combustion-chamber gases, more specifically also at those points of the sealing assembly comprising an engine block, a cylinder head and the cylinder-head gasket where there is not the installation space necessary to be able to use a combustion-chamber sealing bead having a width profile (that is to say a combustion-chamber sealing bead of which the width as measured at the bead crest and/or at the bead feet varies along the combustion-chamber sealing bead) of which the width changes are sufficiently great to be able to compensate for larger local changes to the component rigidity of the engine block and/or of the cylinder head.
In a cylinder-head gasket of the kind defined at the outset, this problem can be solved in accordance with the invention with a combustion-chamber sealing bead in which the deformation resistance of the bead legs of the combustion-chamber sealing bead with respect to pressing forces oriented perpendicularly to the sealing layer and acting on the combustion-chamber sealing bead is greater at least in longitudinal regions of the intermediate portions of the combustion-chamber sealing bead than in screw portions of the combustion-chamber sealing bead.
At points of the above-mentioned sealing assembly at which, with use of a combustion-chamber sealing bead with uniform geometry and/or bead rigidity (uniform deformation resistance) along the bead, the combustion-chamber sealing bead is not acted on by pressing forces sufficient for sufficient gas sealing, in a cylinder-head gasket according to the invention the deformation resistance of the bead legs of the combustion-chamber sealing bead is such that, when the cylinder-head gasket is in the installed state, the combustion-chamber sealing bead of the cylinder-head seal, above all also the intermediate portions thereof, is acted on by pressing forces which, along the periphery of the sealing bead, are sufficient all over for reliable gas sealing.
Since, as has already been mentioned above, the clamping forces acting on the installed cylinder-head gasket are introduced through the cylinder-head screws more or less at specific points into the sealing assembly comprising the cylinder head, the cylinder-head gasket and the engine block, and the cylinder head as well as the engine block do not form absolutely rigid components, it is ensured by the cylinder-head screws that the cylinder-head seal, in the regions of the cylinder-head screws, is pressed against the mutually opposed sealing faces of the engine block and of the cylinder head with forces sufficient to attain the desired sealing effect; since, however, on account of the fact that the engine block and cylinder head are not absolutely rigid and due to the reaction forces of the clamped cylinder-head seal, the height or width of the sealing gap to be sealed by the cylinder-head seal, between the mutually opposed sealing faces of the engine block and cylinder head, in regions of the aforementioned sealing assembly which, in a plan view of these sealing faces and the cylinder-head seal, lie between mutually adjacent cylinder-head screws (or between mutually adjacent screw holes in the cylinder-head seal), is greater, at least in some regions, than at the cylinder-head screws (or screw holes), in preferred embodiments of the cylinder-head gasket according to the invention the combustion-chamber sealing bead and at least one of its intermediate portions, at least in a longitudinal region of such an intermediate portion, has a height profile, more specifically in such a way that the size of the protrusion of the convex side of the combustion chamber sealing bead beyond the regions of the directly adjacent sealing layer varies along this intermediate portion of the combustion-chamber sealing bead. Such a height profile is recommended for the case that the at least predominantly resilient flexibility of the cylinder head and/or of the engine block between the cylinder-head screws cannot be compensated for solely by the fact that the deformation resistance of the bead legs of the combustion-chamber sealing bead is greater, at least in longitudinal regions of the intermediate portions of the combustion-chamber sealing bead, than in the screw portions thereof; the aforementioned flexibility of the components constituted by the cylinder head and engine block, which fundamentally are not absolutely rigid, may be even greater locally if the cylinder head and/or the engine block also has other openings in its sealing face facing the cylinder-head gasket at relatively short radial spacings from a cylinder chamber, and/or the cylinder head or the engine block has a cavity, for example for cooling water, close to a cylinder chamber.
The invention relates above all to cylinder-head gaskets of which the combustion chamber sealing bead is formed as what is known as a rectangular bead or trapezoidal bead—the cross-sections through the combustion-chamber sealing bead (sections in planes running perpendicularly to the longitudinal direction or peripheral direction of the combustion-chamber sealing bead) have the cross-sectional form of a sealing layer region provided with a groove formed therein and an oppositely arranged protrusion, wherein, on the concave side of the combustion-chamber sealing bead, the groove base runs substantially parallel to the plane of the actual sealing layer, and the groove side walls in the case of a rectangular bead run substantially perpendicularly and in the case of a trapezoidal bead run substantially obliquely to this sealing layer plane, however, the transitions of the groove side walls into the actual sealing layer and into the groove base are not strictly rectangular in cross-section, but instead are rounded.
The invention relates primarily to cylinder-head gaskets having a sealing layer, preferably a single sealing layer, with a metal sheet made of a cold-formable steel being used for their production. Such a steel is more deformable than a spring steel (see in particular the comments provided below with regard to spring steels), and the hardness or compressive strength of a cold-formable steel of this kind can be increased locally by stamping or impact extrusion—in the event of such a forming procedure, the metal of the sealing layer is made to flow in some regions, whereby cold-forming involves a strain hardening of the metal of the formed sealing layer regions.
In the case of a cylinder-head gasket according to the invention, the deformation resistance or the rigidity of the combustion-chamber sealing bead, at least in longitudinal regions of its intermediate portions, is increased at least primarily or predominantly in that the deformation resistance or the rigidity of the bead legs is increased in these longitudinal regions. The deformation resistance of the bead legs in respect of pressing forces oriented perpendicularly to the sealing layer and acting on the crest portion of the combustion-chamber sealing bead is in particular at least more than 50% greater, preferably more than 60% greater, and in particular more than 70% greater, at least in longitudinal regions of the intermediate portions of the combustion chamber sealing bead than in screw portions of the combustion-chamber sealing bead.
The deformation resistance of the combustion-chamber sealing bead in intermediate portions thereof may also be increased, at least in longitudinal regions of the intermediate portions, in that the crest portion of the combustion-chamber sealing bead is changed appropriately there (compared with other longitudinal regions of the combustion-chamber sealing bead); as already mentioned, however, the increase, in some regions, of the deformation resistance of the combustion-chamber sealing bead is achieved in accordance with the invention at least primarily or predominantly by an increase, in some regions, of the deformation resistance of the bead legs.
The solution according to the invention is based on the consideration that, in the case of a combustion-chamber sealing bead with varying bead rigidity or varying deformation resistance along the bead, changes to the bead rigidity may be brought about above all by a locally differing rigidity or a locally differing deformation resistance of the bead legs of the combustion-chamber sealing bead. With a combustion-chamber sealing bead in which the bead legs have a varying deformation resistance along the bead, the rigidity or the deformation resistance of the combustion-chamber sealing bead can also be adapted, along the latter, in some regions or locally, to the locally different component rigidities of the engine components constituted by the cylinder head and engine block, without the width of the combustion-chamber sealing bead (in a plan view of the latter) having to be varied; this is also true for the case in which the width of the combustion-chamber sealing bead on the side of its bead feet, that is to say on its concave side, is larger than on its convex side, that is to say in the region of its bead crest or crest portion (in each case in a plan view of the cylinder-head seal).
Preferred embodiments of the cylinder-head gasket according to the invention are characterized by at least one of the following features:
Advantageous embodiments of the cylinder-head gasket according to the invention are characterized in that, in intermediate portions along the combustion-chamber sealing bead, at least in longitudinal regions of the intermediate portions,
varies such that, in these longitudinal regions of the intermediate portions, the deformation resistance of the combustion-chamber sealing bead measured in the direction of the screw hole axes differs locally along the combustion-chamber sealing bead, that is to say varies along the combustion-chamber sealing bead (not necessarily all over).
In the case of a cylinder-head gasket according to the invention it is preferred if, along the combustion-chamber sealing bead in zones of the bead legs delimited by planes running parallel to the plane of the sealing layer, at least in longitudinal regions of the intermediate portions, the material thickness and/or the structure of the metal of the bead legs varies along the aforementioned longitudinal regions such that, along the combustion-chamber sealing bead in these longitudinal regions of the intermediate portions, the deformation resistance of the combustion-chamber sealing bead measured in the direction of the screw hole axes is different locally along the combustion-chamber sealing bead.
Advantageous embodiments of the cylinder-head gasket according to the invention are also those which are configured such that, along the combustion-chamber sealing bead, the cross-section of said bead and/or the structure of the metal of the sealing layer varies, in particular primarily or predominantly in the bead legs, in such a way that when the cylinder-head gasket is installed and pressed between the engine components constituted by the cylinder head and engine block, the crest portion of the combustion-chamber sealing bead is acted on all over, in the intermediate portions of said bead, by pressing forces sufficient to provide an adequate sealing of combustion-chamber gases. Here, the combustion-chamber sealing bead may be configured such that a variation in its cross-section also results in a variation of its cross-sectional area. A variation of the cross-section and/or of the metal structure shall be understood here to mean that the cross-sectional form and/or the structure changes along the combustion-chamber sealing bead, wherein cross-sectional changes shall be understood to mean changes which result in a change to the deformation resistance of the combustion-chamber sealing bead, in particular primarily or predominantly or even exclusively of the bead legs.
In a cylinder-head gasket according to the invention, particularly preferred embodiments are those in which, along the combustion-chamber sealing bead, the cross-sectional form of said bead and/or the structure of the metal of the sealing layer varies at least substantially or predominantly in the two bead legs, which does not rule out variations of the cross-sectional form and/or of the structure of the crest portion of the combustion-chamber sealing bead, provided these variations have a lesser influence on the deformation resistance of the combustion-chamber sealing bead than the variations of the cross-section and/or of the structure of the bead legs.
It may also be advantageous, in order to equalize the pressing forces acting on the installed and pressed cylinder-head seal, along the combustion-chamber sealing bead at least in regions of the intermediate portions of the combustion-chamber sealing bead, to additionally provide the crest portion of the combustion-chamber sealing bead with at least one stamped protrusion extending in the longitudinal direction of the combustion-chamber sealing bead, preferably in order to provide the crest portion additionally with a height profile extending in its longitudinal direction. If such a protrusion is intended to lead not only to a local reinforcement, but also to a local camber of the crest portion of the combustion-chamber sealing bead, the combustion-chamber sealing bead is formed such that the protrusion projects in the direction pointing away from the bead feet of the combustion-chamber sealing bead.
In order to attain the most favorable production costs possible, it is recommended to form the combustion-chamber sealing bead such that the latter, on its concave side, forms a groove extending in the bead longitudinal direction and preferably also into the crest portion, the depth and/or cross-section of said groove varying at least in longitudinal regions of the intermediate portions along the sealing bead, wherein, in cross-sections through the combustion-chamber sealing bead, the groove thereof and in particular also the crest portion thereof are formed preferably and at least substantially mirror-symmetrically with respect to a line running perpendicularly to the sealing layer plane; stamping tools which can be produced economically may then be used for the stamping of the combustion-chamber sealing bead.
In the case of a combustion-chamber sealing bead of which the cross-section is substantially rectangular or corresponds substantially to a trapezoid or a U, when the cylinder-head gasket is installed and pressed, the crest portion of the combustion-chamber sealing bead is acted on by greater pressing forces than each of the bead feet (pressing forces per length unit of the combustion-chamber sealing bead). In the case of engines in which the installation space available for accommodating the combustion-chamber sealing bead is limited in the radial direction in relation to the combustion-chamber opening, more specifically at least in some regions along the combustion-chamber sealing bead and/or only on one side of the cylinder-head seal, it is advantageous that in a cylinder-head gasket according to the invention it is not necessary to provide the combustion-chamber sealing bead, in particular the crest portion thereof, with a width profile along the bead; preferred embodiments of the cylinder-head gasket according to the invention are therefore characterized in that the width of the combustion-chamber sealing bead, as measured on the convex side of the combustion-chamber sealing bead in a plan view of the sealing layer, and/or the crest portion of the combustion-chamber sealing bead is at least substantially constant along the combustion-chamber sealing bead. When measuring the width of the crest portion, it is then possible to take into consideration the limited installation space available on the convex side of the combustion-chamber sealing bead for accommodating same, which is important above all for the following reasons: as already mentioned, at the time of installation and during operation of the cylinder-head seal, the crest portion of the combustion-chamber sealing bead is acted on by greater pressing forces than each of the bead feet, and therefore the crest portion brings about an improved gasket with respect to combustion-chamber gases than each of the individual bead feet; furthermore, it cannot be ruled out that the width of the combustion-chamber sealing bead, measured in a plan view of the sealing layer, on the concave side of said bead, that is to say on the side of its bead feet, increases at least in longitudinal regions of the bead when the bead legs are stamped and/or at the time of installation and during operation of the cylinder-head seal, but the width of the combustion-chamber sealing bead on its convex side, that is to say on the side of its crest portion, does not.
In this regard, the following should be noted: particularly in preferred embodiments of the cylinder-head gasket according to the invention, in particular if these embodiments comprise just a single sealing layer, the thickness of the sheet steel used for the sealing layer configured in accordance with the invention is much greater than 0.3 mm and is preferably at least twice or even at least three times the aforesaid value. Due to the above-described forming during the stamping of the combustion-chamber sealing bead into the sheet steel of the sealing layer, the steel is locally heavily deformed to differing extents in the region of the combustion-chamber sealing bead, and in so doing is strengthened, wherein the combustion-chamber sealing bead also attains such a strength in the region of its crest portion that the width of the crest portion does not change, or at least does not significantly change, at the time of installation and during operation of the cylinder-head seal, also because the pressing forces acting at this time on the crest portion run perpendicularly to the pressed side thereof, whereas the pressing forces acting on the combustion-chamber sealing bead could primarily cause the inclination of the bead legs (in cross-sections through the combustion-chamber sealing bead) to change; in preferred embodiments of the cylinder-head gasket according to the invention, however, the bead legs, on account of their cross-sectional form, their cross-sectional area and their structure brought about by the forming process, are configured in the intermediate portions such that the spacing between the two bead feet does not change, at least not significantly, also at the time of installation and during operation of the cylinder-head seal.
When realizing preferred embodiments of the invention, a combustion-chamber sealing bead is sought, along which the cross-section is at least approximately rectangular or trapezoidal, wherein in some longitudinal portions of the combustion-chamber sealing bead the cross-section may be at least approximately rectangular and in other longitudinal regions may be at least approximately trapezoidal. Here, such embodiments are characterized in particular by at least one of the following features:
The invention also relates to a method for producing a cylinder-head gasket with at least one, and preferably only one, metal sealing layer, in which there are provided at least one combustion chamber opening and, around said opening, screw holes for the passage of cylinder-head screws, and a combustion-chamber sealing bead stamped in the sealing layer, wherein the combustion-chamber sealing bead, on its convex side, has a crest portion which extends along the combustion-chamber sealing bead, in a plan view of the sealing layer between two bead legs, or, in a cross-section through the bead, above or below two bead legs, by means of which bead legs the crest portion is connected to regions of the sealing layer bordering the combustion-chamber sealing bead and into which regions the bead legs transition in each case by a bead foot, and wherein, in a plan view of the sealing layer, the screw holes are arranged at a spacing from the combustion-chamber opening and at spacings from one another in the peripheral direction of the combustion-chamber opening, and the combustion-chamber sealing bead runs between the combustion-chamber opening and the screw holes, and also has screw portions, each of which lies closest to a screw hole, and intermediate portions between the screw portions.
In order to attain local and in particular also different increases in the deformation resistance or the rigidity of intermediate portions of the combustion-chamber sealing bead with respect to pressing forces oriented perpendicularly to the sealing layer and acting on the crest portion of said bead, bead legs are produced during the stamping of intermediate portions of the combustion-chamber sealing bead, at least in longitudinal regions of the intermediate portions, and the cross-sectional form and/or area and/or structure of said bead legs varies
such that the deformation resistance of each of the bead legs of the combustion-chamber sealing bead with respect to pressing forces oriented perpendicularly to the sealing layer and acting on the crest portion of said bead is locally different along the combustion-chamber sealing bead, at least in these longitudinal regions of the intermediate portions.
The aforesaid cross-sections are regions of cross-sections through the various intermediate portions arranged in succession along the intermediate portions and in each case constitute a section through the entire profile of the particular intermediate portion.
The above-stated feature (b) shall be understood in conjunction with the arrangement of the production method according to the invention in particular such that, at least in longitudinal regions or portions of the intermediate portions at least in some, preferably in most, and in particular in all cross-sections through these longitudinal regions of the intermediate portions, the cross-sectional form and/or area or the material thickness and/or the structure of the bead legs varies or changes along the bead legs, that is to say viewed in an aforementioned cross-section along each of the bead legs.
Particularly advantageous embodiments of the method according to the invention are characterized in that, as the combustion-chamber sealing bead is stamped into the sealing layer, a basic bead with an at least substantially constant cross-section along the basic bead and with screw portions, each of which lies closest to a screw hole, and intermediate portions situated between said screw portions is firstly stamped in the sealing layer, and in that at least longitudinal regions of these intermediate portions of the basic bead are then formed by stamping, at least such that the bead legs of the combustion-chamber sealing bead that vary in their cross-section or their material thickness and/or their structure are then produced; the second stamping process is advantageously arranged such that, at least in the intermediate portions of the basic bead, the crest region thereof is also formed such that the final form of the crest portion of the combustion-chamber sealing bead is thus achieved, but in particular so too is a strengthening of the metal in the region of the final crest portion brought about by the forming process.
In principle, however, it is also possible, with the aid of stamping tool parts tailored to the combustion-chamber sealing bead to be produced, to manage with just a single stamping process when carrying out the production method according to the invention.
It is particularly advantageous if the production method according to the invention is arranged such that, when stamping the intermediate portions of the combustion-chamber sealing bead at least in longitudinal regions of the intermediate portions, the metal of the sealing layer, in particular predominantly the metal of the bead legs, is strain-hardened locally by impact extrusion or flow stamping.
If the crest portion of the combustion-chamber sealing bead of a cylinder-head gasket according to the invention (as mentioned above) is to be provided with at least one stamped protrusion extending in the longitudinal direction of the combustion-chamber sealing bead, this protrusion can be produced readily by any of the two above-described embodiments of the production method according to the invention; here, in view of the locally different strengths of regions of the combustion-chamber sealing bead that are to be achieved, it is advantageous to arrange the production method such that, during the stamping of an intermediate portion longitudinal region provided with the protrusion by impact extrusion or flow stamping, metal of the sealing layer is displaced into the bead legs and, in order to form the protrusion, into the crest portion.
The present invention also relates to a cylinder-head gasket produced by the method according to the invention.
Lastly, the present invention also relates to a multi-cylinder reciprocating internal combustion engine with an engine block, a cylinder head, and a cylinder-head seal, which is clamped and pressed by means of cylinder-head screws between component sealing faces of the engine block and of the cylinder head, and which has at least one, but in particular just a single, metal sealing layer, in which there are provided a combustion-chamber opening for each cylinder of the engine and, around said opening, screw holes for the passage of cylinder-head screws, and a combustion-chamber sealing bead stamped into the sealing layer, wherein the combustion-chamber sealing bead, on its convex side, has a crest portion extending in the bead longitudinal direction, which crest portion is arranged along the combustion-chamber sealing bead, in a plan view of the sealing layer between two bead legs, or, in a cross-section through the bead, above or below two bead legs, by means of which bead legs the crest portion is connected to regions of the sealing layer bordering the combustion-chamber sealing bead, into which regions the bead legs transition in each case by means of a bead foot, and wherein, in a plan view of the sealing layer, the screw holes are spaced from the combustion-chamber opening and are arranged at spacings from one another in the peripheral direction of the combustion-chamber opening, and the combustion-chamber sealing bead runs between the combustion-chamber opening and the screw holes and has screw portions, each of which lies closest to a screw hole, and between the screw portions has intermediate portions, and wherein at least one of the components constituted by the engine block and cylinder head has, in its component sealing face, at least one sealing face region, in which the component rigidity of this component with respect to pressing forces directed perpendicularly to its component sealing face is lower than in sealing face regions of this component adjacent to this sealing face region.
In accordance with the invention, in such an engine, the deformation resistance of the bead legs of the combustion-chamber sealing bead of the cylinder-head gasket with respect to pressing forces oriented perpendicularly to the sealing layer of the cylinder-head gasket and acting on the crest portion of the combustion-chamber sealing bead is greater, at least in longitudinal regions of the intermediate portions of the combustion-chamber sealing bead, than in screw portions of the combustion-chamber sealing bead, wherein, along at least one intermediate portion of the combustion-chamber sealing bead of the clamped and pressed cylinder-head seal, the deformation resistance of the bead legs is adapted at least to the locally different component rigidity of the at least one component constituted by the engine block or cylinder head in the region of its component sealing face pressed against the intermediate portion of the combustion-chamber sealing bead, in such a way that sealing face regions of lower component rigidity are associated with bead leg regions of greater deformation resistance.
Here as well, the deformation resistance of the bead legs shall be understood to mean their deformation resistance with respect to pressing forces acting on the combustion-chamber sealing bead perpendicularly to the sealing layer.
The rigidity of the combustion-chamber sealing bead may thus be adapted to locally different component rigidities in such a way that locally reduced component rigidities also as a result of cavities can be taken into account.
In what is known as a liner engine, the engine block for each cylinder has a cylinder liner with a liner sealing face facing the cylinder-head gasket and cooperating therewith, with a liner sealing face region surrounding the axis of the cylinder liner. In particular, the combustion-chamber sealing bead of the installed cylinder-head gasket is pressed against this liner sealing face region, which is usually circular ring-shaped in a plan view of the cylinder liner, so as to gasket the cylinder as closely as possible to its cavity with respect to an escape of the combustion gases forming in the cylinder at high pressures. Since, in many liner engines, the aforementioned annular liner sealing face has a relatively small radial width (in relation to the liner axis) and therefore defines the installation space available on the side of the engine block for accommodating the combustion-chamber sealing bead, the use of a cylinder-head gasket according to the invention in a liner engine entails significant advantages; as is clear from the above descriptions of preferred embodiments of the cylinder-head gasket according to the invention, preferred embodiments of the internal combustion engine according to the invention configured as liner engines are characterized in that the combustion-chamber sealing bead according to the invention abuts with its crest portion against the above-described liner sealing face region, in order to thus particularly effectively and easily solve the problem, caused by the aforementioned liner sealing face, of a limited installation space on the side of the engine block for accommodating the combustion-chamber sealing bead.
Features, advantages and details of the invention will also become clear from the accompanying claims and/or from the accompanying graphical representations of preferred embodiments of the invention and/or from the following description.
The accompanying drawings show:
For each of the combustion-chamber openings of the sealing layer 10, a combustion-chamber sealing bead 16 is stamped into said sealing layer, wherein
The part of an engine block 18 associated with the part of the cylinder-head gasket shown in
In the schematically shown embodiment, cavities (not visible in
Lastly,
As can be seen in
The method according to the invention for producing a cylinder-head gasket according to the invention can also be explained with reference to
There are preferred, however, embodiments of the production method according to the invention which manage with a single stamping process and in which stamping tool parts tailored to the screw regions and the intermediate screw regions of the combustion-chamber sealing bead to be produced are used; such a stamping tool can be constructed readily by any fabricator experienced in the field of stamping tools for the production of flat metal gaskets.
As can be seen in
It will also be explained hereinafter, with reference to
It is now stressed once again, however, that in the case of a combustion-chamber sealing bead according to the invention the bead legs each transition by a bead foot into the regions of the sealing layer bordering the combustion-chamber sealing bead; in
In the screw portion 16a, the combustion-chamber sealing bead 16 on its convex side (on the underside of the crest portion 30a according to
In
In preferred embodiments of the cylinder-head gasket according to the invention the combustion-chamber sealing bead 16, in a screw portion 16a along said bead, has at least substantially all over the same cross-section and the same cross-sectional dimensions (before installation, that is to say before the cylinder-head gasket is pressed). This is the case in particular if the length of a screw portion 16a measured along the combustion-chamber sealing bead 16 is defined such that, in a plan view of the sealing layer 10, a screw portion 16a is delimited by two radii, which start from the axis of the combustion-chamber opening associated with the combustion-chamber sealing bead and are tangential to the screw hole lying closest to this screw portion 16a (reference may be made in this regard to
In the above-described embodiment of the production method according to the invention with two stamping processes, in which, in order to produce the combustion-chamber sealing bead, a basic bead is firstly stamped by a first stamping process into the sheet steel used for the production of the sealing layer 10, the combustion-chamber sealing bead 16 in its screw portions 16a preferably has the form, that is to say the cross-sectional shape and the cross-sectional dimensions, of this basic bead—in the embodiment shown in
As can be seen from the line of section 4-4 from
In
At least in longitudinal regions of an intermediate portion 16b, there is a channel, denoted in
As can be seen in
The following references have been used in
As the groove 34a″ is stamped, a maximum groove width D″ and/or a maximum groove depth T′ are formed and, respectively, may be slightly larger, but also slightly smaller than the width D and the depth of the groove 34a of the combustion-chamber sealing bead 16 in a screw portion 16a.
In preferred embodiments, in a cross-section through an intermediate portion 16b of the combustion-chamber sealing bead 16, in particular in a cross-section through a longitudinal region of the intermediate portion configured in accordance with the invention, the transitions of the recess 36″ into the groove 34a″ as well as the transitions of this groove into the adjacent side of the sealing layer 10 are rounded.
The following feature of preferred embodiments of the invention is also comprehensible from
In the regions bordering the two sides of the combustion-chamber sealing bead 16, the sealing layer 10 has a material thickness E; this material thickness is in particular the sheet thickness of the sheet steel used for the production of the sealing layer 10. In an intermediate portion 16b, in particular in a longitudinal region of the intermediate portion configured in accordance with the invention, the material thickness E′ of the sealing layer 10 at the deepest point of the recess 36″ is smaller than the material thickness of the sealing layer 10 between the base of the groove 34a and the face of the crest portion 30a (lower face of the crest portion according to
Since the invention relates to a combustion-chamber sealing bead which is provided in a sealing layer of a cylinder-head gasket and which has a crest portion extending in the thickness longitudinal direction, which crest portion is connected by means of two bead legs of the combustion-chamber sealing bead to regions of the sealing layer bordering said bead, the bead legs transitioning into said regions in each case by a bead foot of the relevant bead leg, in
When producing the intermediate portions 16b, in particular a longitudinal region configured in accordance with the invention of an intermediate portion of this kind, material of the sealing layer is displaced, during the stamping of the channel 36′, more specifically primarily its recess 36″, in directions which point towards the bead legs 32a′ formed as a result of the stamping. The stamping tool or a tool part thereof may also be configured readily such that, as the channel 36′, primarily the recess 36″, is stamped, material of the sealing layer is also displaced in the direction of the crest portion of the intermediate portion 16b to be produced, and therefore the crest portion 30a′ is provided at least in longitudinal regions of the intermediate portions 16b with at least one protrusion 40, which extends preferably in the longitudinal direction of the combustion-chamber sealing bead 16.
In preferred embodiments of the cylinder-head gasket according to the invention, as the intermediate portions 16b are stamped, more specifically in particular as the recess 36″ is stamped, the metal of the sealing layer 10 is strain-hardened on account of the cold forming at least also in regions of the crest portion 30a′, more specifically also if an intermediate portion 16b is not provided with a protrusion 40.
As can be seen from a comparison of
In preferred embodiments of the cylinder-head gasket according to the invention, however, the cross-sectional shapes and cross-sectional dimensions of the bead legs 32a′ vary along an intermediate portion 16b, in particular at least along a longitudinal region or a plurality of longitudinal regions of the intermediate portion 16b, so as to achieve an equalization of the pressing forces, which are exerted by the intermediate portions 16b onto the component sealing faces of the engine components constituted by the engine block and cylinder head, along the combustion-chamber sealing bead at the time of installation and during operation of the cylinder-head seal. In the case of a cylinder-head gasket according to the invention, this equalization of the pressing forces is based at least primarily on the fact that the cross-sectional shape and/or dimensions and/or area and/or the material thickness of the bead legs and/or the structure of the metal of the bead legs varies or vary along these longitudinal regions of the intermediate portions and/or varies or vary in at least some cross-sections through these longitudinal regions along the bead legs (in the relevant cross-section)—in
In this regard it is noted that, in order to stamp the combustion-chamber sealing bead 16, a stamping tool can be readily used of which the cross-section changes along the combustion-chamber sealing bead or intermediate portions to be stamped and/or along the bead legs (in each case in a cross-section through the combustion-chamber sealing bead) in accordance with the desired result of the stamping process.
If the intermediate portions 16b are to be provided at least in longitudinal regions thereof with a protrusion, such as the protrusion 40 shown in
For the sake of completeness, the following is also noted:
As is clear from the above, in preferred embodiments of the cylinder-head gasket according to the invention, the combustion-chamber sealing bead, along its intermediate portions (the intermediate portions 16b in the embodiment shown in the drawings), has different cross-sections, and in particularly preferred embodiments the cross-sectional changes along the combustion-chamber sealing bead occur continuously, that is to say not abruptly. This is true in particular also for the transitions of the screw portions into the intermediate portions (in the embodiment shown in
In
As the intermediate portions 16b are stamped, the metal used for the sealing layer 10, in particular a steel and preferably a steel that can be formed relatively well, that is to say a relatively ductile steel, is formed relatively strongly at least in longitudinal portions of the intermediate portions 16b extending along the combustion-chamber sealing bead 16, more specifically preferably by stamping or impact extrusion, such that, at least in longitudinal portions of the intermediate portions 16b extending along the combustion-chamber sealing bead 16, at least in some and preferably in all zones 204 of the bead legs 32a′, the material thickness and/or the structure of the metal of the bead legs varies along the combustion-chamber sealing bead 16, more specifically such that, along the combustion-chamber sealing bead 16, at least in these longitudinal portions, the deformation resistance of the combustion-chamber sealing bead, as measured in the direction of the screw hole axes 12a, is locally different along the combustion-chamber sealing bead; the material thicknesses of the bead legs 32a′ differing along the combustion-chamber sealing bead 16 are measured here in each case in cross-sections through the combustion-chamber sealing bead 16, more specifically preferably in said zones (204) in a direction parallel to the plane of the sealing layer (10). This means in particular that, at least in longitudinal regions of the intermediate portions (16b), at least in some and preferably in all of the aforesaid zones (204), the material thickness of the bead legs (32a′) measured in the above-described way varies along the combustion-chamber sealing bead (16), and therefore the deformation resistance of the combustion-chamber sealing bead (16), more specifically primarily of the bead legs (32a′), is locally different along the combustion-chamber sealing bead.
In preferred embodiments of the invention, along the entire combustion-chamber sealing bead, the height of the combustion-chamber sealing bead measured perpendicularly to the plane of the sealing layer is at least substantially constant, wherein, if, at least in longitudinal regions of the intermediate portions of the combustion-chamber sealing bead, the crest portion thereof is provided with a protrusion (such as the protrusion 40 shown in
For the present invention, the height of the combustion-chamber sealing bead or of a bead leg shall be understood in particular to mean the following:
Subject to the above requirements, the amount G1 shown in
If the combustion-chamber sealing bead does not have a height profile in its intermediate portions, the amount G1 in the screw and intermediate portions 16a and 16b respectively of the combustion-chamber sealing bead is at least the same; if the intermediate portions (16b), however, have a height profile, the amount G1 at least in longitudinal regions of the intermediate portions is greater than in the screw portions.
The material thickness of the crest portions 30a and 30a′ (there without the protrusion 40) is in particular substantially the same as the amount G1.
A sealing gap 58 accommodating the cylinder-head gasket 56 is formed by the engine block 50/cylinder liner 52 module and the cylinder head 54. In the region of the cylinder liner 52, a cylinder chamber of the engine has been denoted by 60. In its upper region in accordance with
With its upper end face in accordance with
In
For the region of the course of the bead rigidity shown above the engine block 18 by a curve, it has been assumed that the component rigidity of the engine block is reduced in the region of the combustion-chamber sealing bead 16 by a cavity for cooling water associated with a discharge opening 22, and that not only the fact that the engine components constituted by the engine block and cylinder head are not to be understood as absolutely rigid components has to be taken into consideration.
As is made clear by the curve denoted by 100 in
As is evident from the above description of the invention, these may also be defined, in particular for preferred embodiments, such that, in the case of a cylinder-head gasket of the kind described at the outset (see also the preamble of the accompanying claim 1), the profile of the combustion-chamber sealing bead (shape and/or area of the cross-section of the combustion-chamber sealing bead) and thus the deformation resistance of the combustion-chamber sealing bead changes along said bead at least in longitudinal regions (in other words in longitudinal portions) of the intermediate portions, such that, when the cylinder-head gasket is in the installed and pressed state, the pressing forces acting on the intermediate portions of the combustion-chamber sealing bead, along the intermediate portions, are sufficient all over for an adequate sealing of combustion-chamber gases and preferably are at least substantially of equal magnitude.
The above-mentioned change to the profile of the combustion-chamber sealing bead means that, during the production of the combustion-chamber sealing bead stamped into the sealing layer, in the intermediate portions along said bead, the metal of the sheet of the sealing layer is deformed to differing degrees, more specifically in particular and predominantly in the bead legs; in the case of a combustion-chamber sealing bead with a longitudinal groove or channel stamped into the sealing layer on its concave side and a crest portion extending along the combustion-chamber sealing bead on its convex side, this means, in other words, that in the intermediate portions of the combustion-chamber sealing bead along the intermediate portions, the cross-section of the groove or channel, in particular the depth and/or the cross-sectional shape of the groove or channel, is not constant, with the result that, along the intermediate portions, the deformability and the rigidity or the deformation resistance of the combustion-chamber sealing bead, in particular and predominantly the bead legs, is locally different—along the intermediate portions, these properties of the combustion-chamber sealing bead or of the bead legs in longitudinal regions of the latter are thus greater or smaller than at other points, wherein such a point shall be understood in each case to mean a cross-section through the combustion-chamber sealing bead. In embodiments in which the crest portion of the combustion-chamber sealing bead is provided, at least in longitudinal regions of the intermediate portions, with a protrusion of the aforementioned kind, the combustion-chamber sealing bead of preferred embodiments, in the region of such a protrusion, also has an increased bead height and therefore a greater rigidity or a greater deformation resistance compared with longitudinal regions of the intermediate portions without such a protrusion, but with identical bead width as compared to a longitudinal region provided with such a protrusion (the bead width shall be understood here to mean the width of the combustion-chamber sealing bead in a plan view of the concave side thereof).
Above, it has been described what shall be understood, for the present invention, by the height of the bead legs of the combustion-chamber sealing bead according to the invention. What will now be described hereinafter is what shall be understood, for the invention, by the width of the bead legs of a combustion-chamber sealing bead according to the invention, more specifically on the one hand in screw portions and on the other hand in intermediate portions of a combustion-chamber sealing bead according to the invention. This description is provided on the basis of a combustion-chamber sealing bead according to the invention, which is configured as a rectangular bead, at least in its screw portions, whereas in the intermediate portions, at least in the longitudinal regions thereof configured in accordance with the invention, the cross-section of the combustion-chamber sealing bead, on account of the forming processes performed in these longitudinal regions, differs somewhat from a rectangular bead, more specifically in respect of the cross-sectional shape of the channel arranged on the concave side of the combustion-chamber sealing bead.
In a cross-section through the combustion-chamber sealing bead, this has a center line (c), which extends perpendicularly to the plane defined by the sealing layer. In this cross-section, each of the two bead legs is delimited on its side facing the center line by a virtual line (inner line), which runs parallel to the center line, and on its other side facing away from the center line the bead leg is delimited likewise by a virtual line (outer line), which runs parallel to the center line. In this cross-section through the combustion-chamber sealing bead, the outer line runs through an outer lateral delimitation of the protrusion by which the convex side of the combustion-chamber sealing bead protrudes beyond the regions of the sealing layer directly adjacent to said combustion-chamber sealing bead.
The inner line lies between the center line and the outer line.
The above is true both for screw portions and for intermediate portions.
In a cross-section through a screw portion of the combustion-chamber sealing bead, the inner line runs through a lateral delimitation of the channel or groove stamped into the sealing layer on the concave side of the combustion-chamber sealing bead.
In a cross-section through an intermediate portion, in particular through a longitudinal region of the intermediate portion configured in accordance with the invention, the channel stamped into the sealing layer on the concave side of the combustion-chamber sealing bead has a first region, which borders the side of the sealing layer facing away from the convex side of the combustion-chamber sealing bead and has its greatest width on this sealing layer side. In this cross-section, the channel additionally has a second region, which adjoins the first region, more specifically in the direction of the convex side of the combustion-chamber sealing bead, and (again in this cross-section) has its greatest width at its transition into the first region. In an intermediate portion, this second region thus leads to an additional recess of the aforementioned channel; however, it should not be ruled out that, in a cross-section through an intermediate portion, in particular through a longitudinal region of the intermediate portion configured in accordance with the invention, at least one third region of the aforementioned channel also adjoins in the direction of the convex side of the combustion-chamber sealing bead, as a result of which the channel is made even deeper.
In such a cross-section through an intermediate portion, in particular through a longitudinal region of the intermediate portion configured in accordance with the invention, the above-mentioned inner line runs through an outer lateral delimitation of the aforementioned second region, specifically through a point at which (again in this cross-section) this second region transitions into the aforementioned first region of the channel.
In
In
In a cross-section through a screw portion or an intermediate portion, in particular through a longitudinal region of such a portion configured in accordance with the invention, the width of each of the two bead legs is equal to the spacing of an aforementioned outer line from the aforementioned inner line adjacent thereto.
In the embodiment of the combustion-chamber sealing bead according to the invention shown in
The same is true for a combustion-chamber sealing bead according to the invention configured as a trapezoidal bead, wherein, however, it must be taken into consideration that, in the case of a trapezoidal bead, the two bead legs do not run perpendicularly, but at an incline to the plane of the sealing layer, more specifically both in a cross-section through a screw portion and in a cross-section through an intermediate portion of the combustion-chamber sealing bead—the aforementioned outer and inner lines then run likewise parallel to one another, but also at an incline to the plane of the sealing layer.
Since the increase in some regions of the deformation resistance of the bead legs is preferably achieved in that, as the combustion-chamber sealing bead is stamped, the sheet steel used for the production of the sealing layer is deformed to differing extents in some regions, more specifically primarily or predominantly in order to form the bead legs, a steel which can be formed more easily, that is to say with lower forces, than spring steels is preferably used for the production of the sealing layer; apart from any coatings, preferred embodiments of the sealing layer are thus characterized in that the sealing layer is one produced from a soft steel for cold forming, that is to say the steel is a cold-formable and thus strain-hardenable steel. Beyond formed regions of the sealing layer, the sheet steel thereof thus consists of a steel which is cold-formable to the same extent as the steel of the sheet steel used for the production of the sealing layer.
For the production of preferred embodiments of the sealing layer, recommended are steels for which the properties determining the cold forming are at least approximately the same as the cold-forming-determining properties of the steel having material number 1.0338 (in particular according to standard DIN EN 10130:1991), wherein the steel with the material number 1.0338 is particularly preferred.
When stamping preferred embodiments of the combustion-chamber sealing bead according to the invention, the sheet steel used for the production of the sealing layer is deformed to such an extent that the degree of deformation of the steel in the region of an intermediate portion, in particular a longitudinal region of the intermediate portion configured in accordance with the invention, of the combustion-chamber sealing bead, specifically in particular in the region of the bead legs, is at least 5% (in forming technology the degree of deformation is usually denoted by 1). The maximum of the degree of deformation is particularly preferably much more than 5%. In the embodiment shown in
In preferred embodiments of the combustion-chamber sealing bead according to the invention, as an intermediate portion of the combustion-chamber sealing bead is stamped, in particular a longitudinal region of the intermediate portion configured in accordance with the invention, the channel stamped into the concave side of the combustion-chamber sealing bead is made additionally deeper (in comparison to the channel of a screw portion), wherein, in a cross-section through the longitudinal region of the intermediate portion configured in accordance with the invention, the additional recess has a smaller width than the channel width on the side of the sealing layer facing away from the convex side of the combustion-chamber sealing bead. In the region of the additional recess, the material thickness of the crest portion of the combustion-chamber sealing bead is reduced in some regions (in comparison with the thickness of the crest portion in a screw region of the combustion-chamber sealing bead).
In preferred embodiments of the combustion-chamber sealing bead according to the invention, the channel stamped in the concave side of said bead is constructed, in a cross-section through the combustion-chamber sealing bead, at least substantially symmetrically with respect to a line which runs perpendicularly to the sealing layer plane and which is the aforementioned center line.
In the case of the combustion-chamber sealing bead according to the invention, this forms a land on its convex side, which land protrudes (or projects) beyond the regions of the sealing layer directly adjacent to the combustion-chamber sealing bead. In preferred embodiments of the sealing layer the width of the land, as measured in a plan view of the sealing layer or land thereof, along the combustion-chamber sealing bead, is at least substantially constant—in the embodiment shown in
In addition, it should also be noted in respect of
In a plan view of an intermediate portion configured in accordance with the invention or a longitudinal region of an intermediate portion configured in accordance with the invention, more specifically in a plan view of the concave side of the combustion-chamber sealing bead, the width of the stamped channel, where it transitions into the side of the sealing layer 10 facing away from the convex side of the combustion-chamber sealing bead, is at least substantially the same as the width of the channel or groove stamped into the sealing layer in a screw portion of the combustion-chamber sealing bead on the concave side thereof, and therefore, in the embodiment shown in
During the production of an intermediate portion, in particular a longitudinal region of the intermediate portion configured in accordance with the invention, of a combustion-chamber sealing bead according to the invention, as the channel provided on the concave side of the combustion-chamber sealing bead is being stamped (said channel being denoted by 36′ in the embodiment shown in
In preferred embodiments of the combustion-chamber sealing bead according to the invention, neither the width nor the height of the land formed by the convex side of the combustion-chamber sealing bead is thus changed (in comparison to this land in a screw portion of the combustion-chamber sealing bead). In the embodiment shown in
The local increase in the deformation resistance or the rigidity of the combustion-chamber sealing bead according to the invention therefore is not based, or at least is not significantly based, on a local change to the ratio of bead width to bead height, but primarily or predominantly on a local change to the cross-sectional shape and/or the structure of the bead legs.
It should again also be noted that in preferred embodiments of the cylinder-head gasket according to the invention the combustion-chamber sealing bead has, in its intermediate portions, a constant width, that is to say no width profile (in a plan view of the convex side of the combustion-chamber sealing bead).
Since a cylinder-head gasket according to the invention, in the installed state, that is to say when it is clamped between the engine components constituted by the engine block and cylinder head, is intended to generate, by means of its bead crest and its bead feet, sufficiently high pressing forces all over in order to gasket off the combustion-chamber gases, it should be ensured that each cylinder-head gasket is constructed for a quite specific engine, which is stipulated to the gasket fabricator by the engine manufacturer, who provides the gasket fabricator with the engine data necessary for construction of a seal. On the basis of this engine data, the gasket manufacturer may perform FEM (finite element method) calculations for production of a cylinder-head gasket according to the invention, with the aid of which calculations the combustion-chamber sealing bead can be readily configured such that it generates, by means of its bead crest and its bead feet, sufficiently high pressing forces all over for a sealing of the combustion-chamber gases when the cylinder-head gasket is in the installed state, more specifically also at points of the sealing assembly comprising the engine block, the cylinder head, and the cylinder-head gasket at which the installation space available for accommodating the combustion-chamber sealing bead is limited, whether the sealing face of the engine block and/or of the cylinder head facing the cylinder-head gasket has an opening in the direct vicinity of the combustion-chamber sealing bead, or whether at least one of these engine components has a local component weakness.
As can be understood on the basis of the above description and/or the accompanying drawings, the present invention may also be defined as follows, wherein the cylinder-head gasket defined hereinafter preferably also has features of the accompanying claims 1 to 31.
The invention relates to a cylinder-head gasket with a metal sealing layer in which there are provided at least one combustion-chamber opening, screw holes each defining a screw hole axis around said opening for the passage of cylinder-head screws, and a combustion-chamber sealing bead stamped into the sealing layer, wherein, in a plan view of the sealing layer, the screw holes are arranged at a spacing from the combustion-chamber opening and at spacings from one another in the peripheral direction of the combustion-chamber opening, and the combustion-chamber sealing bead runs between the combustion-chamber opening and the screw holes and has screw portions, each of which lies closest to a screw hole, and intermediate portions between the screw portions, and wherein the combustion-chamber sealing bead, on its concave side, forms a channel stamped into the sealing layer, extending in the bead longitudinal direction, and having a channel base.
In order to improve the sealing capability of a cylinder-head gasket of this kind, said gasket is configured in accordance with the invention such that, in cross-sections through the combustion-chamber sealing bead, at the channel base the material thickness of the sealing layer in intermediate portions of the combustion-chamber sealing bead, specifically at least in longitudinal regions of the intermediate portions, is smaller than in screw portions of the combustion-chamber sealing bead.
In the case of such a cylinder-head seal, as the combustion-chamber sealing bead is stamped into the sealing layer, at least in longitudinal regions of the intermediate portions, the metal of the sealing layer is cold-formed to a greater extent and is thus strain-hardened to a greater extent than in screw portions of the combustion-chamber sealing bead, which results in an increase of the deformation resistance of the combustion-chamber sealing bead with respect to these pressing forces acting in the direction of the screw hole axes in intermediate portions of the combustion-chamber sealing bead, specifically at least in longitudinal regions of the intermediate portions (in comparison to the deformation resistance of the combustion-chamber sealing bead in screw portions thereof).
Here, preferred embodiments are ones in which, in cross-sections through the combustion-chamber sealing bead, the depth of the channel in intermediate portions of the combustion-chamber sealing bead, specifically at least in longitudinal regions of the intermediate portions, is greater than in screw portions of the combustion-chamber sealing bead, and in which, in intermediate portions of the combustion-chamber sealing bead, specifically at least in longitudinal regions of the intermediate portions, the cross-sectional form of the channel differs from the cross-sectional form of the channel in screw portions. Here, the cross-sectional form of the channel is understood to mean the geometrical shape of the cross-sectional form, and for example not the size of the dimensions of the cross-sectional form.
Among these preferred embodiments, particularly advantageous are those in which, in cross-sections through the combustion-chamber sealing bead, the cross-sectional area of the channel in the intermediate portions of the combustion-chamber sealing bead, specifically at least in longitudinal regions of the intermediate portions, is greater than in screw portions of the combustion-chamber sealing bead, and it is even more advantageous if, in cross-sections through the combustion-chamber sealing bead, the width of the channel decreases in the direction of the channel base, more specifically at least in intermediate portions of the combustion-chamber sealing bead, which means that, in cross-sections through the combustion-chamber sealing bead, the width of the channel in the direction of the channel base in screw portions of the combustion-chamber sealing bead may also be constant.
It is most advantageous if the percentage decrease of the width of the channel in the direction of the channel base in intermediate portions of the combustion-chamber sealing bead, specifically at least in longitudinal regions of the intermediate portions, is greater than in screw portions, this being important in the case of combustion-chamber sealing beads in the form of a trapezoidal bead.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 119 307.3 | Aug 2017 | DE | national |
This application is continuation of International Application No. PCT/EP2018/072644, filed on Aug. 22, 2018, which claims priority to German Application No. 10 2017 119 307.3, filed on Aug. 23, 2017, which applications are hereby incorporated in their entirety by reference in this application.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2018/072644 | Aug 2018 | US |
| Child | 16796165 | US |
