Patent Publication Number: US-2009224486-A1

Title: Cylinder head gasket

Description:
This application is a divisional of application Ser. No. 11/033,247 filed Jan. 11, 2005, which is claims priority of German application No. 10 2004 044 851.5 filed Sep. 10, 2004. 
    
    
     The present disclosure relates to the subject matter disclosed in German application No. 10 2004 044 851.5 of Sep. 10, 2004, which is incorporated herein by reference in its entirety and for all purposes. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a cylinder head gasket with a single-layered or multilayered, at least substantially metallic gasket plate comprising for a sealing bead which is elastically deformable in height and surrounds a combustion chamber through-opening of the gasket a so-called double stopper for delimiting the bead deformation with a deformation delimiting device arranged radially inside the sealing bead and radially outside the sealing bead. 
     Such a cylinder head gasket is disclosed in EP-1 298 364-A of ElringKlinger AG (see lines 1-3 of page 6). In a gasket with a multilayered gasket plate, the deformation delimiting devices (stoppers) can all be provided on the sheet metal layer (so-called functional layer) provided with the sealing bead or on one or several of the other layers. It is, however, also possible to provide one stopper on the functional layer and another stopper on another layer. In a first embodiment of the cylinder head gasket according to EP-1 298 364-A, a single stopper is arranged between the combustion chamber through-opening and the associated sealing bead. The stopper is formed by a honeycomb pattern, surrounding the combustion chamber through-opening as a ring closed within itself, of knob-like elevations stamped out of the functional layer. In two further embodiments, the knob pattern is replaced either by a bead stamped into the functional layer, which, in a plan view of the gasket plate or the functional layer, forms a meander extending in circumferential direction of the combustion chamber through-opening, or by a crown, surrounding the combustion chamber through-opening, of short beads stamped into the functional layer and extending radially in relation to the combustion chamber through-opening. 
     EP-1 298 365-A of ElringKlinger AG discloses a multilayered metallic cylinder head gasket having two functional layers each with an elastic sealing bead surrounding a combustion chamber through-opening and with a further metal layer arranged between the functional layers, which is provided with a stopper lying between the sealing beads and the combustion chamber through-opening, which is formed by a two-dimensional pattern, produced by flow pressing, of discrete, cup-like depressions and elevations formed by material displaced during the stamping of the depressions and associated with the depressions. The stopper has elevations and depressions on both sides of this metal layer and, consequently, can delimit the deformation of both sealing beads. 
     The object underlying the invention was to create a cylinder head gasket of the kind mentioned at the outset, which with respect to the sealing around a combustion chamber through-opening and the stopper function has better characteristics in the long term than the above-described known gaskets. 
     SUMMARY OF THE INVENTION 
     To achieve this object, one departs from a cylinder head gasket such as disclosed in EP-1 298 364-A, namely from a cylinder head gasket with an at least substantially metallic gasket plate comprising at least one sheet metal layer, at least one combustion chamber through-opening, a sealing bead elastically deformable in height, formed in a metal layer and surrounding the combustion chamber through-opening in a manner closed within itself, and—in relation to the sealing bead—both radially inside and radially outside the sealing bead a deformation delimiting device delimiting the bead deformation and at least partially surrounding the combustion chamber through-opening, the deformation delimiting device—in a plan view of the gasket plate—being formed close to the sealing bead and in a metal layer by such a deformation of the metal layer that the metal layer has at least one elevation in at least one of its main surfaces in the area of the deformation delimiting device, and the total thickness of the metal layer in the area of the deformation delimiting device is greater than the original thickness of the metal layer. To accomplish the set object, it is proposed, in accordance with the invention, that such a cylinder head gasket be designed such that the one deformation delimiting device comprises a bead which, in a plan view of the gasket plate, forms over at least part of its length an at least almost complete meander extending in circumferential direction of the combustion chamber through-opening, and that in a plan view of the gasket plate and in circumferential direction of the combustion chamber through-opening, the other deformation delimiting device comprises a plurality of discrete elevations. 
     When hereinabove mention is made of the fact that a deformation delimiting device—for reasons of simplicity referred to as stopper hereinbelow—is provided both radially inside and radially outside the sealing bead, the word “a” is not to be interpreted as “a single”. Accordingly, both stoppers can be provided on the metal layer provided with the sealing bead, but one stopper or both stoppers can also be formed on another metal layer or on two other metal layers. The stopper comprising the meander-shaped bead could also comprise a further stopper element or further stopper elements. Finally, one stopper can be provided on a functional layer provided with a sealing bead, and another stopper on another functional layer similarly provided with a sealing bead. 
     The basic concept underlying the present invention is thus to combine two stoppers of fundamentally different design with each other, namely one stopper having a bead with an at least partially meander-shaped form, with a stopper made of, in particular, stamped (in a type of deep-drawing or flow-pressing process) discrete, i. e., individual, elevations. Such a combination results in quite a number of advantages: 
     With a meandering bead closed in the shape of a ring within itself as stopper there can be created around the combustion chamber through-opening, in addition to the sealing zone formed by the sealing bead to be protected, a second sealing zone (at least when the stopper is bearing, i. e. is pressed). On the other hand, a stopper formed by discrete elevations can be subjected to higher load without the stopper height being reduced, as the number of meander loops per length unit in a meandering bead—measured in circumferential direction of the combustion chamber through-opening—is limited for deformation reasons (space is required for the arc-shaped “reversal areas” of a meandering bead), whereas the “packing density” of stamped, discrete, i. e., individual, elevations can be increased almost optionally, which involves an increase in the deformation strength of the stopper. A so-called double stopper is generally used in cylinder head gaskets intended for engines with cylinder liners. In such engines, a certain lowering of a cylinder liner inserted into an engine block is to be anticipated during engine operation, which reduces the effect of the stopper lying radially inside the sealing bead and over the liner. For this reason, a further stopper lying radially outside the sealing bead and radially outside the liner over the actual engine block is used to reliably protect the sealing bead in the long term against excessive deformation. Since the cylinder liner, the engine block and the cylinder head (between which the cylinder head gasket is clamped) usually consist of different materials, with stoppers of different design one can take the different material characteristics into consideration. Finally, a tool for stamping discrete elevations is simpler and less expensive than a tool for stamping a meandering bead. 
     In an inventive cylinder head gasket, the meandering bead is preferably arranged radially inside the actual sealing bead to be protected by the stopper, i. e. between the sealing bead and the combustion chamber through-opening for sealing-off against combustion gases in front of the sealing bead by means of the above-mentioned second sealing zone and for shielding the actual sealing bead to be protected by the stopper from the hot combustion gases, whereby the risk of impairing the spring-elastic behavior of the sealing bead is reduced or totally eliminated. The other deformation delimiting device of different design then lies—seen from the combustion chamber through-opening—behind the sealing bead to be protected by the double stopper. 
     When the stopper lying radially inside the sealing bead to be protected is to be configured as a meandering bead, combustion chambers lying very close together can result in the web areas of the cylinder head gasket lying between neighboring through-openings becoming very small, so that in the web area the ring zone remaining between a sealing bead close to the combustion chamber and the rim of a neighboring combustion chamber through-opening no longer offers enough space to also construct the radially inner stopper as a meandering bead there. In this case, in the web area or over part of the web area the bead forming the radially inner stopper can be formed differently from the meander shape, for example, in the shape of a circular arc, and if one wishes to or can dispense with the radially inner stopper forming a second sealing zone, the reverse arcs of the bead joining meander loops could also be punched away when after the reshaping of the pertinent metal layer, the combustion chamber through-opening is punched out of it. Reference is made to these embodiments because in the definition of the basic concept underlying the present invention mention is made of the fact that the one deformation delimiting device comprises a bead which over at least part of its length forms an at least almost complete meander. 
     In a preferred embodiment of the inventive cylinder head gasket, in a plan view of the gasket plate, the other deformation delimiting device comprises a two-dimensional pattern of discrete, knob-like elevations, which are preferably arranged in the manner of a honeycomb pattern, so as to achieve as high a packing density as possible. In an alternative embodiment, the elevations of the other deformation delimiting device (in a plan view of the gasket plate) are formed by short beads extending approximately in radial direction or at an incline thereto in relation to the combustion chamber through-opening, which preferably form a crown of such short beads enclosing the combustion chamber through-opening entirely or partially. The elevations can also be arranged in groups, between which (seen in circumferential direction of the combustion chamber through-opening) stopper-less areas lie, so as to accommodate, for example, other through-openings of the gasket plate, such as screw holes, there, or because there is insufficient space for a continuous stopper between neighboring through-openings of the gasket plate. For reasons of completion, mention is made of the fact that a stopper can also be a mixed form of the two above-described other deformation delimiting devices and comprise a mixture of groups of knob-like elevations and groups of short beads. 
     In addition, a stopper or each stopper of an inventive cylinder head gasket can have a height profile and/or a width profile (in a plan view of the pertinent metal layer) around a combustion chamber through-opening, as disclosed, for example, in EP-1 298 364-A, EP-1 298 365-A or U.S. Pat. No. 6,036,195. 
     As mentioned hereinabove, in a multilayered cylinder head gasket the radial inner and the radial outer stoppers can each be provided on one of the metal layers. It is then advisable to provide the meandering bead on a layer facing the engine block or a cylinder liner, and the stopper formed by discrete elevations on a layer facing the cylinder head. 
     Further features, advantages and details of the invention will be apparent from the appended claims and/or the following description and the appended drawings of two particularly advantageous embodiments of the inventive cylinder head gasket. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  shows a perspective and sectional representation of part of the first embodiment and part of an engine block provided with a cylinder liner; and 
         FIG. 2  shows a representation corresponding to  FIG. 1  with the second embodiment of the inventive cylinder head gasket. 
         FIG. 3  shows a perspective and sectional view representation of part of an another embodiment and a part of an engine block provided with a cylinder liner. 
         FIG. 4  shows a perspective and sectional view representation of part of a further embodiment and a part of an engine block provided with a cylinder liner. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  shows part of a crankcase or engine block  10  in which there is inserted a cylinder liner  12  whose bore forms part of a combustion chamber  14  of the engine. The liner  12  has at the top a liner collar  12   a,  whose upper end face forms a sealing surface  12   b,  which is intended to be flush with, i. e., at the same level as, a sealing surface  10   b  formed by an upper end face of the engine block  10 . 
     There is clamped between the sealing surfaces  10   b ,  12   b  and a sealing surface, facing these, of a cylinder head, not illustrated, a cylinder head gasket which in the illustrated embodiment has a gasket plate comprised of an upper functional layer  16  and a lower functional layer  18  made of sheet spring steel. These could be the only metal layers of the gasket plate of the inventive cylinder head gasket, but the latter could also comprise further metal layers, for example, a smooth, i. e., flat layer lying between the two functional layers  16 ,  18  and/or an upper and/or a lower cover layer over the functional layer  16  or under the functional layer  18 . Congruent openings lying one above the other are stamped out of all layers of the cylinder head gasket. Openings lying one above the other form a combustion chamber through-opening  20  and  22 , respectively, which is associated with the combustion chamber  14  or a further combustion chamber, not shown in  FIG. 1 , of the engine. Also indicated in  FIG. 1  is a screw through-opening  24  produced in like manner for a cylinder head screw. Between neighboring combustion chamber through-openings, the gasket plate of the cylinder head gasket comprises a web  26 , only an end area of which is shown in  FIG. 1 . The web  26  passes into a gusset-shaped area of the gasket plate between the two combustion chamber through-openings  20  and  22 , in which the screw through-opening  24  lies. 
     Around each combustion chamber through-opening, each of the functional layers  16  and  18  is provided with a spring-elastic sealing bead  30  and  32 , respectively, deformable in height, which surrounds the associated combustion chamber through-opening in the form of a circular ring closed within itself. The two sealing beads  30 ,  32  face each other with their convex sides and lie sealingly against each other when the gasket is installed. Radially inside the sealing bead  32 , the lower functional layer  18  is provided with an inner stopper in the form of a meandering bead  34 , i. e. a meander-shaped bead in plan view, which, in particular, forms a ring closed within itself and enclosing the combustion chamber through-opening  20 . The meandering bead  34  was produced in the lower functional layer  18  by stamping the lower functional layer  18  in such a way that the meandering bead  34  in accordance with  FIG. 1  projects upwards above the functional layer  18 , i. e., in the same direction as the sealing bead  32 . However, the height of the projection formed by the meandering bead  34  is less than the height of the projection formed by the sealing bead  32 , so that when the cylinder head gasket is pressed, the sealing bead  32  is first flattened somewhat in a spring-elastic manner before the meandering bead  34  has an effect (namely at the flat ring area of the upper functional layer  16  radially inside its sealing bead  30 ). 
     Seen radially outwardly from the respective combustion chamber through-opening  20  and  22  there is located in the upper functional layer  16  behind the sealing bead  30  a radially outer or rear stopper  50 , formed by discrete, knob-shaped elevations  52   a,  which were produced by cup-like depressions  52   b  being stamped into the upper functional layer  16 . The elevations  52   a  rise above the functional layer  16  in the same direction as the sealing bead  30 , however, the height of the elevations is less than that of the sealing bead  30 , so that they allow—like the meandering bead  34 —a certain spring-elastic flattening of the sealing bead  30  when the cylinder head gasket is pressed. 
     In the illustrated embodiment, the elevations  52   a  or the depressions  52   b  are arranged in the manner of a honeycomb pattern, in order to achieve as large a “packing density” of the elevations as possible. The pattern formed by the elevations  52   a  preferably forms a ring which is concentric with the associated combustion chamber through-opening  20  and  22 , respectively, but which has interruptions where screw through-openings  24  and webs  26  are located. Alternatively, the width of the pattern formed by the elevations  52   a  could vary such that elevations  52   a  are also present around the screw through-openings  24  and/or in the area of the webs  26 . 
     In the illustrated embodiment, when the cylinder head gasket is pressed, the elevations  52   a  are supported on a flat area of the lower functional layer  18 , but they could, in the same way as the meandering bead  34 , be supported on a metal layer arranged between the functional layers  16  and  18 . 
     As shown in  FIG. 1 , the rear stoppers  50  lie above the sealing surface  10   b  of the engine block  10 , whereas the sealing beads  30  and  32  and the meandering bead  34  forming the front or radially inner stopper lie above the sealing surface  12   b  of the cylinder liner  12 . The sealing beads  30 ,  32  could, however, also lie radially outside the liner  12 . 
     In the embodiment shown in  FIG. 1 , the elevations  52   a  or the depressions  52   b  have approximately the shape of spherical segments and all have the same shape. They could, however, also have other shapes and/or different shapes, for example, the shapes of the depressions  52   b  could correspond to segments of ellipsoids or the frustum of a pyramid. 
     The embodiment shown in  FIG. 2  differs from the embodiment according to  FIG. 1  only in the configuration of the radially outer or rear stoppers, so that only these stoppers will be described hereinbelow and for all the remaining elements in  FIG. 2  the same reference numerals are used as in  FIG. 1 . 
     In the embodiment according to  FIG. 2 , the rear stoppers  50 ′ are each formed by a crown of short stamped beads  52   a ′, which extend in radial direction in relation to the associated combustion chamber through-opening  20  and  22 , respectively. These beads could, however, also include a preferably small acute angle with the radial direction. In comparison with a meandering bead, the beads  52   a ′—measured in circumferential direction of the associated combustion chamber through-opening—can be arranged very close to one another, as, differently from a meandering bead, no space is required for U-shaped connecting arcs. 
     The embodiment shown in  FIG. 3  provides both the radially inner and radially outer stoppers  34  and  50 , respectively, as well as the sealing bead  30  disposed on the same sheet metal layer, for example, as described on specification page 3, penultimate sentence, wherein for all the remaining elements in  FIG. 3 , the same reference numerals are used as in  FIG. 1 . 
     The embodiment shown in  FIG. 4  provides both the radially inner and radially outer stoppers  34  and  50 , respectively, on the same sheet metal layer and the sealing bead  30  on a different sheet metal layer, for example, as described on specification page 3, penultimate sentence, wherein for all the remaining elements in  FIG. 4 , the same reference numerals are used as in  FIG. 1 . 
     What was said hereinabove regarding interruptions or a width profile of the stoppers  50  applies accordingly to the stoppers  50 ′ (in the case of a width profile of a stopper  50 ′, the beads  52   a ′ then have different lengths).