Abstract:
The present invention concerns a metallic flat gasket with at least one sealing layer with at least one port, with a sensor layer corresponding to the ports being deposited on at least one surface of the sealing layer. This sensor layer consists of a compression protection layer and at least one break, in which a sensor element is at least partially installed.

Description:
FIELD OF INVENTION 
   The invention concerns a metallic flat gasket with at least one sealing layer with at least one port for sealing off two components from each other. Here, a sensor element is integrated in the system, such that it is protected from compression. 
   BACKGROUND OF THE INVENTION 
   Metallic sealing systems are used in the automotive industry primarily as cylinder head gaskets. Here, cylinder head gaskets are used to seal off various chambers, such as combustion chambers, coolant and lubricant openings, threaded bolts, as wells as ports for valve control parts, from each other. The requirements on these sealing systems continue to become increasingly rigorous and the recording of measurement data for characteristic parameters of the gasket appears to be desirable. Here, the measurement in the direct vicinity of the corresponding openings enables data recording that is as precise as possible. Due to these requirements on the dimensioning, sensor measurements are coming more and more to the forefront. 
   The teaching of DE 199 13 092 concerns a cylinder head gasket, on which a sensor device for detecting measurement values is arranged. 
   However, the disadvantage of the prior art is that the danger of compression of the sensor element is so great that only very robust sensors can be used. 
   Thus, the problem of the present invention is to devise a metallic sealing system that contains a sensor element that is protected from compression. 
   SUMMARY OF THE INVENTION 
   This problem is solved by the generic metallic flat gasket with the features of claim  1  and by the generic production method with the features of claim  20 . The additional subordinate claims present advantageous refinements. In the claims  27  and  28 , the use of the sealing system is described. 
   According to the invention, a metallic flat gasket with at least one sealing layer with at least one port is created, with a corresponding sensor layer relative to the ports deposited on at least one surface of the sealing layer, which consists of a compression protection layer with at least one break. Here, the compression protection layer is used to protect the sensor element from mechanical damage and consists of an incompressible material, e.g., high-hardness steel. Here, the sensor element is at least partially installed in the break of the compression protection layer. 
   In a preferred configuration, the sensor layer is deposited on a separate carrier layer. Thus, the deposition of the sensor layer can be performed independently of the production process of the cylinder head gasket. Simultaneously, the carrier layer can be selected in regard to an optimum adhesive bond between the sensor layer and sealing layer. 
   Here, the sensor layer can be arranged on one side of the cylinder head gasket facing either the cylinder head or the engine block. Likewise, it is possible for one sensor layer to be deposited on both sides. This allows the arrangement of several sensor elements on both sides of the metallic sealing system. Likewise, the carrier layer can be arranged on one side of the metallic sealing system facing either the cylinder head or the engine block. 
   In an advantageous refinement, the sensor element is at least partially installed in the carrier layer. Here, e.g., there can also be a break, in which the sensor element can be inserted. Likewise, the carrier layer can also have additional corresponding structures for connection elements to a measurement value detector unit, in addition to the structures for the sensor element. These structures can include lines or contacts. In a similar way, the compression protection layer can also have structures for the connection elements. The advantage of such structures is that, in addition to the sensor element itself, the connection elements can also be protected from compression. 
   In a preferred configuration, a thermally conductive layer is deposited on the end side of the sensor element facing away from the carrier layer. The thermal conductivity of this layer should be sufficiently high that a nearly error-free temperature measurement can be performed across this thermally conductive layer at the corresponding component. For example, a thermally conductive paste can be used as the thermally conductive layer. It is also preferable if the carrier layer, which faces the engine block and/or the cylinder head, has a high thermal conductivity value. 
   In a preferred configuration, a layer that protects against mechanical damage is deposited on the side of the sensor element facing away from the carrier layer. This protection layer provides improved protection against compression, and even more protection against wear and tear due to friction. 
   In an advantageous refinement, the carrier layer is produced from steel, aluminum, and/or other aluminum-containing materials, such as ceramics or enamels. Here, the carrier layer preferably has a layer thickness of less than 300 μm, with a layer thickness of approximately 150 μm being especially preferred. 
   The compression protection layer, which preferably consists of high-hardness steel, aluminum, and/or other aluminum-containing materials, such as ceramics or enamels, preferably has a layer thickness of less than 300 μm, with a layer thickness of approximately 200 μm being especially preferred. It is also preferred if the compression protection layer is electrically insulated at the end sides of the recess. 
   In a preferred refinement, the compression protection layer can also have a bead and/or stopper. Here, it is especially preferred if the sensor element is arranged in the direct vicinity of the bead in order to provide additional protection against compression. Likewise, it is possible for the sensor element itself to be stamped as a bead and/or stopper. 
   Preferably, the sensor element is selected from the group of piezoelectric, piezoresistive, capacitive, magnetic, electromagnetic, DMS [wire strain gauge], eddy current, optical fiber, and micromechanical sensors. The sensor element is preferably designed as a temperature sensor. The use of a resistor sensor as the sensor element in the flat gasket is likewise preferred. Especially preferred is the use of a PTC temperature probe as the sensor element. 
   According to the invention, a method for producing a single-layer or multi-layer metal gasket with a sensor element is proposed, for which initially a compression protection layer is deposited on the metal gasket with the compression protection layer having at least one break, in whose region the sensor element is attached by means of a frictional connection. 
   Here, thick-film techniques, such as those known from screen printing, are used as the preferred deposition technique. These techniques can produce a layer thickness of the sensor element in the range around 30 μm. 
   The sensor element can likewise preferably be deposited using a thin-film technique, which allows a layer thickness of the sensor element of around 1 μM to be realized. The PVD technique is used as the preferred deposition technique. 
   However, additional options for the frictional connection of the sensor element in the break of the compression protection layer also include conventional frictional connections, such as adhesive bonds, soldering, or locking devices. 
   A hardened steel, aluminum, and/or other aluminum-containing materials, such as ceramics or enamels, are preferably used for the compression protection layer and the carrier layer. 
   The flat gasket according to the invention can be used primarily for temperature measurements at combustion chamber openings. However, it can also be used for force, path, expansion, acceleration, and/or pressure measurements at combustion chamber openings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     With reference to the following figures, the flat gasket according to the invention will be explained with reference to individual examples, without limiting the object according to the invention to these examples. 
       FIG. 1  shows a flat gasket according to the invention in cross section. 
       FIGS. 2–10  show various deposition variants of the sensor layer. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a flat gasket in the form of a cylinder head gasket with a stopper  6  and two beads  7 ,  7 ′. Connected here on both sides is a sensor layer  1 ,  1 ′ consisting of the compression protection layers  2 ,  2 ′ and the sensor elements  4 ,  4 ′, which are located in a break of the compression protection layer. In this example, the sensor layer has a thickness of 270 μm. On the sides facing away from the gasket layers  8 ,  8 ′, there is a carrier layer  5 ,  5 ′, which is in direct contact with the cylinder head  9  or the engine block  10  [sic;  9 ′] on the sides facing away from the sensor layers. As this drawing shows, it is possible for the sensor and carrier layers to be arranged on the sides facing both the cylinder head and also the engine block. Similarly, it is also possible for a sensor layer to be deposited on only one side of the cylinder head gasket. 
     FIG. 2  shows the compression protection layer  11  with a break, in which the sensor element  12  is inserted. Simultaneously, this sensor layer  13  is deposited on a carrier layer  14 . 
   In comparison with  FIG. 2 ,  FIG. 3  shows the application of a sensor layer  13  on a carrier layer  14  with the sensor element  12  only partially filling the recess because a thermally conductive layer and/or a layer  15  protecting against mechanical damage is also deposited on the side facing away from the carrier layer  14 . 
   In  FIG. 4 , the sensor element  12  is designed so that it completely fills the recess of the compression protection layer  11 , and, at the same time, extends into the carrier layer  14 . Here, the carrier layer  14  has a structure, in which the sensor element  12  is inserted. A frictional connection between the carrier layer  14  and the sensor element  12  is not absolutely necessary. 
   In  FIG. 5 , the sensor element  12  likewise extends into the carrier layer  14  with a layer  15 , which is thermally conductive or which protects against mechanical damage, also deposited on the side of the sensor element facing away from the carrier layer  14 . This layer  15  can be applied, e.g., in the form of a paste. 
   Analogous to  FIG. 2 ,  FIG. 6  shows a sensor layer  13  consisting of a compression protection layer  11  with a break, in which a sensor element  12  is inserted. In this case, however, no carrier layer is deposited, so that the sensor  13  is deposited directly on the sealing layer of the cylinder head gasket. 
     FIG. 7  shows a sensor layer  13  consisting of a compression protection layer  11  with a break, in which a sensor element  12  is attached, which is covered on one side with a layer  15  that is thermally conductive or that protects against mechanical damage. 
     FIG. 8  shows a sensor layer  13  consisting of a compression protection layer  11 , with the sensor element  12  here being attached in such a way in the recess of the compression protection layer  10  [sic;  11 ], such that the sensor element  3  [sic;  12 ] is locked by means of the sensor socket  16 . 
     FIG. 9  illustrates a portion of a gasket  20  that includes a sealing layer  22 , a carrier layer  24 , and a compression protection layer  26  interposed between the sealing layer  22  and the carrier layer  24 . Compression protection layer  26  is defined by a break and a sensor layer  30  (not sectioned for clarity) is positioned within the break. Preferably, both compression protection layer  26  and sensor layer  30  are deposited on either sealing layer  22  or carrier layer  24 . gasket  20  also includes a bead portion  36  and a stopper portion  40 . 
     FIG. 10  illustrates a portion of a gasket  120  that includes a sealing layer  122 , a carrier layer  124 , and a compression protection layer  126  interposed between the sealing layer  122  and the carrier layer  124 . Compression protection layer  126  is defined by a break and a sensor layer  130  (not sectioned for clarity) is positioned within the break. Preferably, both compression protection layer  126  and sensor layer  130  are deposited on either sealing layer  122  or carrier layer  124 . The gasket  120  also includes a bead portion  136  where the sensor layer  130  is stamped as a bead.