The present invention is to be described in greater detail in the following on the basis of the drawing. The drawing merely describes some special embodiments of the present invention for exemplary purposes, without the present invention being restricted thereto, however. In the drawing:
FIG. 1 schematically shows a partial top view of a metallic flat gasket according to the present invention in the example of a cylinder head gasket;
FIG. 2 schematically shows the cylinder head gasket shown in FIG. 1, now provided with a coating;
FIGS. 3
a-3d schematically show details of surface structures according to the present invention in an idealized top view;
FIGS. 4
a and 4b schematically show flowcharts of the method sequence during the coating of metallic flat gaskets according to the methods in the related art and according to the present invention;
FIG. 5
a schematically shows a cross-section through a further embodiment of a metallic flat gasket according to the present invention along the line A-A in FIG. 2;
FIG. 5
b schematically shows an enlarged illustration of the circled region of FIG. 5a;
FIG. 6
a schematically shows a cross-section through another embodiment of a metallic flat gasket according to the present invention along the line B-B in FIG. 2;
FIG. 6
b schematically shows an enlarged illustration of the circled region of FIG. 6a;
FIG. 7
a schematically shows a cross-section through a further embodiment of a metallic flat gasket according to the present invention along the line B-B in FIG. 2;
FIG. 7
b schematically shows an enlarged illustration of the circled region of FIG. 7a;
FIG. 8
a schematically shows a top view of a pre-stage of a separate metal plate to be inserted into an opening in a metallic carrier layer; and
FIG. 8
b schematically shows the completed separate metal plate of FIG. 8a inserted into the opening of the metallic carrier layer.
FIG. 1 shows a metallic flat gasket 1 according to the present invention in the example of a cylinder head gasket in a partial view. The top view of an outer metallic gasket layer 2 is shown. However, this does not exclude the gasket having further gasket layers which are not shown here. The gasket 1 has multiple through openings 3, of which the largest, centrally positioned openings are combustion chamber openings. Only one combustion chamber opening is shown in its entirety here and one is shown partially, while the complete gasket layer 2 has four combustion chamber openings positioned in a row, for example. Further through openings 3 are provided around the combustion chamber openings toward the edge 8 of the gasket layer 2, which are openings for coolant liquid and oil. In addition, screw openings are provided, which are not shown in greater detail here. The through openings 3 are enclosed by sealing elements 4. These sealing elements 4 are beads which are molded into the gasket layer 2. The beads project out of the image plane in the direction toward the observer. Each individual one of the combustion chamber openings is enclosed by a per se closed bead 4. The lines indicated by 4 illustrate the course of the apex lines of the particular beads here, which run together in the region between neighboring combustion chamber openings into a single bead.
Surface structures 6 are provided in the region of the beads 4 enclosing the combustion chamber openings 3, which follow the course of the beads 4. The surface structures 6 cover the surface of the beads 4 completely, i.e., extend over the bead foot, the bead flanks, and the apex region of the beads. The surface structures 6 comprise multiple depressions 7, which are produced in the gasket layer by irradiating the surface 5 of the gasket layer 2 using laser radiation.
The depressions are positioned in multiple essentially parallel rows 9 to one another, which is schematically shown in FIGS. 3a through 3d. The figures each show partial regions of the surface structure 6. The continuing pattern sections result in the surface structure strips illustrated in FIG. 1. All idealized point rasters shown in FIGS. 3a through 3d were produced by guiding a laser beam linearly over the surface 5 of the gasket layer 2. The linear guiding is identified by the arrow at the upper left edge of the particular pattern. The laser beam is thus guided in the direction of the arrow over the surface 5 of the gasket layer 2 and melts the individual depressions 7 into the surface 5 one after another. Depending on the power and focusing of the laser beam, larger or smaller depressions result in this case, which may also be implemented having different depths depending on the power input. The individual depressions 7 are preferably implemented approximately equally large and deep within a particular pattern. However, it is also conceivable to vary the size and depth of the depressions 7 within a pattern. In all of the cases shown, the laser light is irradiated essentially perpendicularly from above, so that round depressions result.
After producing the first row of depressions 7, the neighboring rows 9 of depressions 7 are produced one after another. For this purpose, the laser beam may be guided in the same direction as in the preceding row. For example, a through opening 3 may be traveled around multiple times in a spiral, in order to provide multiple neighboring rows of depressions 7. Alternatively, it is also possible to reverse the running direction of the laser beam at the end of a particular row and return it in the opposite direction. In both cases, an offset in relation to the neighboring rows 9 may result if the beginning of the further rows does not lie at the same height as that of the neighboring rows. This is shown in FIGS. 3c and 3d. With the aid of targeted laser beam guiding, the distortions of the gasket layer produced through the laser process may be minimized.
As shown in FIG. 1, strip-shaped surface structures are present not only around the combustion chamber openings 3, but rather also around the through openings for oil and coolant water located in the edge region. Frequently, multiple through openings are enclosed by a strip of depressions 7, which is closed per se, here. The beads, which also enclose these through openings as sealing elements, are not shown for the sake of simplicity. However, they lie below the surface structure strips, the apexes of the beads running approximately in the middle of each strip. In addition, a bead (also not shown) is provided around the circumference of the bead edge, on whose surface a surface structure 6 in the form of a strip of neighboring depressions 7 is also located.
FIG. 2 shows the gasket shown in FIG. 1, after a coating 10 was applied to regions of the gasket layer 2 provided with the surface structure 6. This coating 10 is, for example, a synthetic rubber made of FPM, NBR, or silicone, which improves the micro-sealing and the sliding friction properties of the gasket. The coating 10 was applied in a screen printing method. It is obvious that the strips of the coating 10 are somewhat narrower than the strips of the surface structure 6, which projects laterally below the coating 10. The reason for this is that it is to be ensured that the coating 10 is only located on those regions of the surface 5 of the gasket layer 2 in which a surface structure 6 is actually present. In this way, the coating 10 adheres excellently to the metallic gasket layer 2 and is thus more abrasion-resistant and better protected against flowing away than a typical coating applied according to the method steps shown in FIG. 4a.
FIG. 4
b again schematically illustrates the advantages of the method according to the present invention in relation to the typical method shown in FIG. 4a. In contrast to the method of the related art, in the method according to the present invention, all chemical pretreatment steps are dispensed with, and only a pretreatment using laser radiation is necessary in order to provide an outstanding adhesion base for all typically used coatings and/or elastomeric profiled sealing elements. In contrast to the related art, powder coatings may also be used.
FIGS. 5
a through 7b show examples of metallic flat gaskets according to the present invention in the example of cylinder head gaskets in cross-sectional illustrations around through openings which may be screw, oil, or coolant water openings. These openings are typically located in the edge region of the gasket. While the combustion chamber openings may be sealed using beads 13 as sealing elements 4, for example, as in the preceding examples, the oil and water openings and possibly also the screw openings are now sealed by sealing elements 4 which comprise an elastomeric material 11.
In the example of FIGS. 5a and 5b, the elastomeric material 11 is applied on both sides of the gasket layer 2. The application may be performed through injection molding, for example, in order to produce elastomeric beads which completely enclose an oil or coolant water opening 3. In the case shown, two fluid openings 3 are sealed jointly by an elastomeric sealing element 4, which runs at a distance to the openings. A strip-shaped surface structure 6, which is formed by multiple neighboring depressions 7, is located on both sides of the gasket layer 2 in the region of the contact surface of the elastomeric material 11. The surface structure improves the adhesion of the elastomeric material on the gasket layer significantly in relation to an untreated substrate or a substrate pretreated in a typical way.
FIGS. 6
a and 6b show another possibility for sealing fluid opening 3 using elastomeric profiled sealing elements. The sealing element 4 made of elastomeric material 11 is located here in the region of the inner edge of the fluid opening 3. The sealing element shown in FIG. 2, which runs at a distance to the opening 3, is no longer necessary in this case for sealing the opening. The elastomeric sealing element 4 is injected onto the inner edge 12 of the sealing plate 2. It has a greater thickness than the sealing plate 2 and projects past it on both sides. To improve the adhesion of the elastomeric material 11 on the inner edge 12, its surface is provided with a surface structure made of depressions 7.
FIGS. 7
a and 7b show an alteration of the gasket shown in FIGS. 6a and 6b. In this case, the elastomeric material 11 of the sealing element 4 is drawn from the inner edge 12 of the gasket layer 2 onto both sides of the gasket layer. In order to obtain an essentially flush terminus with the gasket layer 2, annular grooves 14 are provided in the gasket layer 2 on both sides, originating from the inner edge 12, which are filled up with the elastomeric material 11. The surfaces of the grooves 14 are provided with a surface structure made of depressions 7. The front faces of the inner edge 12 and edges of the grooves 14 do not have depressions 7. This would be possible to further improve the adhesion of the elastic material 11 on the gasket layer 2, but makes the manufacturing procedure of the surface structure more difficult, since the radiation of the laser light must be performed from a different direction than in the irradiation of the horizontal surfaces in the illustration.
FIGS. 8
a and 8b show another embodiment of the invention in which the sealing element 4 is provided on a separate metal plate 21. As in the previous embodiments, the through opening 3 to be sealed is surrounded by a surface structure 6 which is formed by multiple neighboring depressions 7 and which is located on both sides of the metal plate 21. FIG. 8a shows the separate metal plate 21 without elastomeric material, while in FIG. 8b elastomeric material 11 is applied onto the metal plate 21 in the region of the surface structure 6. As can be seen from FIG. 8b, the ring of elastomeric material 11 is somewhat narrower than the ring of the surface structure 6, which projects laterally below the elastomer 11. The elastomeric material 11 was applied onto both sides of the metal plate 21 before the plate was inserted into opening 22 of the carrier layer 20. Separate metal plates, also called inserts, are preferably used in case of large gasket layers. The inserts are much smaller than the whole gasket layer and can thus be handled more easily, particularly as regards coating steps or application of elastomeric material. The insert with the elastomer applied is then inserted into opening 22 of the carrier layer 20 which, together with the inserted metal plate 21, forms the metallic gasket layer 2. Inserted metal plate 21 and carrier layer 20 are essentially in the same plane, and the insert is held in the opening 22 by spot welding at the protrusions 23 of the carrier layer 20 which overlap with the insert 21. As can by taken from FIG. 8b, only part of the through openings 3 is provided on an insert. The large opening 3 on the left side of the figure and its sealing element are formed in the carrier layer 20. In this case, the opening is a cylinder opening which is surrounded by multiple concentric beads 13.
Patent Application
20080093808
