Abstract:
A metal gasket includes at least three metal plates including first, second and third metal plates laminated in this order from a top to form the metal gasket. Identification marks are provided on at least second and third metal plates in a position not to overlap with one another, and penetration windows are formed in at least the first and second metal plates. The penetration windows are arranged to see the identification mark therethrough located lower than the metal plate where the penetration window is formed.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to a metal gasket which can prevent mis-assembly or wrong assembly of a metal gasket formed by laminating three or more sheets of metal plates, held between two members for sealing; and a mis-assembly detection method of a metal gasket which only requires a simple device and can be easily automatically made. 
     For an automobile engine, metal gaskets such as a gasket sealing a simple sealing-target hole at an intake manifold or exhaust manifold and so on, or a cylinder head gasket sealing between a cylinder head and a cylinder block, are used. The above-mentioned metal gaskets are manufactured by laminating multiple metal plates with different materials, thicknesses, or processes, and in order to obtain a desired sealing capability, these multiple metal plates are required to be laminated in a correct direction on a correct side in a correct order. 
     However, in many cases, the shapes of the metal plates have roughly the same configuration, so that it is difficult to determine the direction, front or back sides, or the assembly sequence of the lamination of the metal plates. In such a case, when the metal plates are laminated, the direction, front and back sides, and assembly sequence of the lamination may be easily mistaken. 
     In order to solve the above-mentioned problem, proposals were made for mis-assembly discriminatory structure of a metal laminate gasket wherein at least a part of one surface of each structural plate is placed in order in a staircase pattern and exposed to the outside, or wherein at least a part of one surface of each structural plate is exposed to the outside so as not to overlap with one another during assembly (for example, refer to Japanese Utility Model Publication (JIKKAI) No. S62-114270 and Japanese Patent Publication (TOKKAI) No. S62-159866), so that the assembly sequence, that is, the number of the assembly order of each single structural plate of the laminated metal gasket can be clearly recognized. 
     Also, a cylinder head laminate gasket was proposed wherein at least one sheet of matching plate overlaps a sheet material; a mark showing the thickness of the sheet material is provided in a position displaced to one side from the center of a bore of the sheet material; and a notch is provided in a position corresponding to the mark in the matching plate. Also, a laminate metal gasket was proposed, wherein each metal plate forming the gasket includes a notch, engraved mark, marking and the like for recognizing the number of the assembly sequence of each metal plate. (For example, refer to Japanese Utility Model Publications (JIKKAI.) No. H1-165857 and No. H6-85963) 
     However, even with the structure which is visually recognizable as mentioned above, the gasket is assembled by determining a projection or groove of the laminated gasket, so that an irregularity of a minute part of the laminate plate with a similar color has to be recognized. Accordingly, human error cannot be completely prevented when the projection or groove is determined. Moreover, a device for preventing mis-assembly is required. 
     The invention is made in order to solve the problems described above, and an object of the present invention is to provide a metal gasket which is formed by laminating multiple metal plates, and can be easily recognized by an assembler or observer when the assembly sequence of the lamination of the metal plates is incorrect. 
     A further object of the present invention is to provide a mis-assembly detection method of the metal gasket which requires only a simple device and can be easily automated. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     In order to achieve the object described above, a metal gasket which is formed by laminating three or more metal plates and held between two members for sealing a sealing-target hole, is provided. An identification mark in each metal plate is provided so that each identification mark does not overlap with one another. A penetration window is provided in each metal plate except for the bottom layer of the metal plates. The penetration window can see through the identification mark of all the metal plates on the lower side during assembly, but cannot see through the identification mark of all the metal plates on the upper side. 
     The upper side, top layer, lower side, and bottom layer tentatively indicate a lamination direction, and do not necessarily mean a vertical direction in the installation state. Also, with respect to the lamination direction, when the vertical direction is reversed, this invention includes a case with the above-mentioned structure. 
     In the metal gasket, if the identification mark is not provided on the top layer of the metal plates, and only the penetration window is provided, the number of identification marks is reduced. Therefore, the manufacturing time can be reduced and the discrimination becomes easier. On the other hand, if the identification mark is provided on the top layer of the metal plates, the manufacturing time increases. However, the number of laminated plates and the number of identification marks correspond with each other, so that the assembly becomes easier to understand. 
     The identification mark can be formed by an engraved mark, coating, or pasting such as sealing. However, if the identification mark is punctured, it can be simultaneously manufactured with the penetration window, so that the manufacturing process can be reduced. If the identification mark is provided only on the side wherein the penetration window is placed during the assembly, the front and back sides of the metal plate can also be recognized. 
     In order to achieve the object described above, a mis-assembly detection method of the metal gasket is structured as a method determining the existence or nonexistence of the mis-assembly by measuring the variation of the distance between the identification mark of the metal gasket and a predetermined position; or a method determining the existence or nonexistence of the mis-assembly by illuminating a light ray on the identification mark of the metal gasket, and measuring the reflected light. 
     According to the mis-assembly detection method of the metal gasket, a simple distance meter device such as a relatively simple optical device, optical distance meter or ultrasonic distance meter, is only required. Also, the existence or nonexistence of the mis-assembly of the metal gasket can be determined by a very simple algorithm which compares the variation of the reflectance or the variation of the distance with a predetermined variation, so that the mis-assembly detection method can be easily automated. 
     According to the metal gasket of the invention, during normal assembly, all the identification marks can be seen through the penetration window, and if the assembly sequence of the lamination is incorrect, some of the identification marks cannot be seen. As a result, an assembler or observer can easily recognize an error of the assembly sequence of the lamination, so that mis-assembly can be prevented. 
     Also, according to the mis-assembly detection method of the metal gasket of the invention, by using a relatively simple device and the simple algorithm, the existence or nonexistence of the mis-assembly of the metal gasket can be determined, so that the mis-assembly detection method can be easily automated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view showing a metal gasket of the first embodiment of the present invention; 
         FIG. 2  is an enlarged sectional view taken along line  2 - 2  in  FIG. 1 ; 
         FIG. 3  is a fragmentary plan view showing the structure of a first discrimination area of a first metal plate; 
         FIG. 4  is a fragmentary plan view showing the structure of a second discrimination area of a second metal plate; 
         FIG. 5  is a fragmentary plan view showing the structure of a third discrimination area of a third metal plate; 
         FIG. 6  is a fragmentary plan view showing the structure of a fourth discrimination area of a fourth metal plate; 
         FIG. 7  is a plan view showing the metal gasket of the second embodiment of the invention; 
         FIG. 8  is an enlarged sectional view taken along line  8 - 8  in  FIG. 7 ; 
         FIG. 9  is an explanatory view of a mis-assembly detection method of the metal gasket of the first embodiment of the invention; and 
         FIG. 10  is an explanatory view of the mis-assembly detection method of the metal gasket of the second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereunder, an embodiment of a metal gasket and a mis-assembly detection method of the metal gasket according to the present invention will be described with reference to the attached drawings as an example of the metal gasket held between an exhaust manifold for an engine and a flange for an exhaust pipe. However, this invention is not limited to the embodiment and can be applied to, for example, other metal gaskets such as a gasket for an intake manifold, cylinder head gasket and so on. Incidentally,  FIGS. 1-10  are schematic explanatory views in which thicknesses of plates, and sizes of sealing-target holes, beads, positioning holes, positioning projections and so on are different from actual ones and enlarged for the sake of explanation. 
     First, the metal gasket of the first embodiment of the invention will be explained. As shown in  FIGS. 1 and 2 , the metal gasket  1  includes four sheets of metal structural plates  10 ,  20 ,  30 ,  40  manufactured according to the shape of the flange of the exhaust pipe. The first to fourth metal structural plates  10 ,  20 ,  30 ,  40  are formed by a mild steel plate, stainless annealed material (anneal material), stainless thermal refining material (spring steel plate) and so on according to demand to each metal plate. 
     In the first to fourth metal structural plates  10 ,  20 ,  30 ,  40 , sealing-target holes  2  are punctured, widely known sealing means such as a full bead  3  and so on are provided around the sealing-target holes  2 , and bolt holes  4  for tightening bolts are formed in four directions. 
     In the invention, as shown in  FIGS. 3-6 , the first to fourth metal plates  10 ,  20 ,  30 ,  40  are respectively provided with first to fourth discrimination areas  11 ,  21 ,  31 ,  41  which overlap during assembly. Additionally, first to fourth identification marks  12 ,  22 ,  32 ,  42  are respectively provided in the first to fourth discrimination areas  11 ,  21 ,  31 ,  41  so as not to overlap with one another during the assembly. In the first embodiment, the identification marks are punctured with the same size and same shape. Incidentally, the identification marks are not required to have the same size and shape, and each metal plate  10 ,  20 ,  30 ,  40  may have a particular size and shape as long as they are easily visible. 
     Basically, as shown in  FIG. 3 , the first discrimination area  11  of the first metal plate  10  is provided with a first identification mark  12  and a first penetration window  13  which can see through the second to fourth identification marks  22 ,  32 ,  42  of the first second to fourth metal plates  20 ,  30 ,  40  which are lower layers of the metal plates in the assembly. 
     Also, as shown in  FIG. 4 , the second discrimination area  21  of the second metal plate  20  is provided with the second identification mark  22 , and a second penetration window  23 . The second penetration window  23  can see the third and fourth identification marks  32 ,  42  of the third and fourth metal plates  30 ,  40  which are the lower layers of the metal plates in the assembly. However, the second penetration window  23  cannot see the first identification mark  12  of the first metal plate  10  which is the upper layer of the metal plates in the assembly. 
     Also, as shown in  FIG. 5 , the third discrimination area  31  of the third metal plate  30  is provided with the third identification mark  32 , and a third penetration window  33 . The third penetration window  33  can see through the fourth identification mark  42  of the fourth metal plate  40  which is the metal plate on the lower layer of the metal plates in the assembly. However, the third penetration window  33  cannot see the first and second identification marks  12 ,  22  of the first and second metal plates  10 ,  20  which are the upper layers of the metal plates in the assembly. 
     Moreover, as shown in  FIG. 6 , the fourth discrimination area  41  of the fourth metal plate  40  is provided with the fourth identification mark  42 , and made so as not to be able to see through the first to third identification marks  12 ,  22 ,  32  of the first to third metal plates  10 ,  20 ,  30  which are the upper layers of the metal plates in the assembly. 
     According to the structure, the identification marks  12 ,  22 ,  32 ,  42  are provided in the respective metal plates  10 ,  20 ,  30 ,  40  in a position wherein each mark does not overlap with one another, and the penetration windows  13 ,  23 ,  33  are provided in the respective metal plates  10 ,  20 ,  30  except for the metal plate  40  which is the bottom layer. The penetration windows  13 ,  23 ,  33  can see the identification marks of the metal plates on the lower side in the assembly, but cannot see the identification marks of all the metal plates on the upper side. 
     Next, the metal gasket of the second embodiment of the invention will be explained. As shown in  FIGS. 7 and 8 , in a metal gasket  1 A, only the following respect differs from the metal gasket  1  of the first embodiment, and the other structures are the same. In the first metal plate  10 A on the top layer, the first identification mark is not provided and identification marks  22 A,  32 A,  42 A are not punctured and formed with an engraved mark. According to the structure, one identification mark is reduced, so that the manufacturing time can be reduced and also discrimination becomes easier. 
     According to the metal gaskets  1 ,  1 A with the above-mentioned structure, during normal assembly, all of the identification marks  22 ,  32 ,  42 ,  22 A,  32 A,  42 A can be seen through the penetration windows  13 ,  23 ,  33 . However, if the assembly sequence of the lamination is incorrect, some of the identification marks cannot be seen. As a result, an assembler or observer can easily recognize an error, so that the mis-assembly can be prevented. 
     Moreover, when the identification marks are provided only on the surface of the upper side of each metal plate, the mis-assembly wherein the front and back sides are incorrect can be easily recognized. Alternatively, in order to show the direction of each metal plate during the assembly, identification marks such as a triangle shape or arrow for a sense of direction can be formed, so that the error of an assembly direction can be recognized. Also, if the identification marks are formed by numbers, a portion which is assembled incorrectly can be recognized, so that it is useful. Incidentally, when the mis-assembly is recognized, the front and back sides and assembly sequence of the lamination of the respective metal plates are accurately prepared, and the metal plates are assembled again, or once they are removed from the manufacturing line, and once again, the correct assembly sequence of the lamination is prepared and returned to the manufacturing line. 
     Next, the mis-assembly detection method of the metal gasket of the first embodiment according to the invention will be explained. As shown in  FIG. 9 , the mis-assembly detection method of the metal gasket is a method detecting the mis-assembly by variations of distances L to the identification marks  12 ,  22 ,  32 ,  42  of the metal gasket  1 , and a distance meter  51  and a discrimination device  52  are used for a detection device  50 . The distance meter  51  may be a contact type. However, a noncontact type such as an ultrasonic distance meter or a laser meter is preferred because it is easy to use. 
     In this method, the distances L between the positions of the identification marks  12 ,  22 ,  32 ,  42  of the metal gasket  1  and a predetermined standard position (for example, the position of the distance meter and the like) are measured sequentially by transferring the distance meter  51  or the metal gasket  1 , and then the existence or nonexistence of the mis-assembly is determined. 
     In the algorithm wherein the existence or nonexistence of the mis-assembly is determined by a measured value, when the variation of the distances L has the same pattern as the variation of the distances L set in advance, the algorithm determines that there is no mis-assembly, and when the variation of the distances L has a different pattern, the algorithm determines that there is a mis-assembly. 
     Next, the mis-assembly detection method of the metal gasket of the second embodiment according to the invention will be explained. As shown in  FIG. 10 , in the mis-assembly detection method of the metal gasket, the reflectance of the identification marks  22 A,  32 A,  42 A of the metal gasket  1 A is changed from the reflectance of the peripheral parts, and the detection device  50 A is provided with a light source  51 Aa illuminating a light ray; a light detection device  51 Ab measures a reflected light; and a determination device  52 A determines the existence or nonexistence of the mis-assembly by the measured value of the reflected light. The reflected light is measured at the light detection device  51 Ab by transferring the light source  51 Aa and the light detection device  51 Ab to the identification marks  22 A,  32 A,  42 A of the metal gasket  1 A, or illuminating the light ray sequentially by transferring the metal gasket  1 A. The measured value is sent to the determination device  52 A, so that the existence or nonexistence of the mis-assembly is determined. 
     In the algorithm determining the existence or nonexistence of the mis-assembly by the measured value, when the number of the reflectance of the illuminated lights is the number of the reflectance of the identification marks  22 A,  32 A,  42 A, the algorithm determines that there is no mis-assembly, and when the numbers are smaller, the algorithm determines that there is a mis-assembly. 
     According to the mis-assembly detection method of the metal gasket, due to the usage of the distance meter device such as an optical distance meter or an ultrasonic distance meter; or a relatively simple optical device, the existence or nonexistence of the mis-assembly of the metal gasket can be determined by the very simple algorithm, so that the mis-assembly detection method can be easily automated. 
     The disclosure of Japanese Patent Application No. 2007-000575, filed on Jan. 5, 2007, is incorporated in the application. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.