Abstract:
A cylinder head gasket is installed in an open-deck engine. The cylinder head gasket includes a first metal plate, a second metal plate having an inner portion disposed on a folded portion of the first metal plate and an outer portion outside the folded portion, an annular bead plate, and an intermediate plate provided between the outer portion of the second metal plate and a base portion of the first metal plate and having a half bead extending from an inner periphery of the inner end portion toward the base portion of the first metal plate. A cylindrical portion of the open-deck engine has a thickness partly changing between inner and outer peripheries thereof. The inner periphery of the intermediate plate is located on the cylinder portion along the outer periphery, a distance of the outer periphery from the inner periphery changing according to the thickness of the cylindrical portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation application of Ser. No. 12/071,545 filed on Feb. 22, 2008. 
     
    
     BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
       [0002]    The present invention relates to a cylinder head gasket sandwiched between a cylinder head and a cylinder block of an open-deck type engine and sealing therebetween. 
         [0003]    The cylinder head gasket is sandwiched between engine members such as the cylinder head and the cylinder block (cylinder body) and the like of an automobile engine and tightened by head bolts, thereby sealing fluid such as combustion gas, oil, coolant water and the like. 
         [0004]    On the other hand, if the engines are distinguished based on a type of the cylinder block, there are a closed-type engine which does not have a coolant water channel on a contact surface between the cylinder block and the cylinder head, and an open-deck type engine wherein the contact surface between the cylinder block and the cylinder head is open to be used as a coolant liquid channel. As shown in  FIG. 12 , the open-deck type engine includes a coolant liquid channel (water jacket)  54  near the cylinder head of an engine block  52 , so that it has an advantage in terms of a cooling performance and reduction in weight. Furthermore, since there is an opening, it can be easily manufactured. 
         [0005]    Regarding the cylinder head gasket for the open-deck type engine, a metal gasket has been proposed (for example, refer to Japanese Patent Publication (TOKKAI) No. H10-281290). The metal gasket provides a grommet along the inner periphery of a cylinder hole in a plate which covers both a cylindrical portion of the cylinder block and an outer wall portion forming the outside of the coolant water channel; seals the combustion gas of a cylinder bore at the thickest portion of the grommet formed in the inner side of a cylinder sleeve; and also seals the coolant water by a step bead formed on both sides of the coolant water channel. 
         [0006]    In this cylinder head, the step bead is provided for sealing the coolant water between the coolant water channel and the cylinder bore. However, a position of an angular portion of the step bead is located on the inner peripheral side of a wall surface (the outer wall surface of the cylindrical portion) of the coolant water channel, and the coolant water contacts the upper surface of a cylinder liner (cylindrical portion). Therefore, an electric etching occurs at the contact surface of the cylinder block due to contact with liquid coolant water containing anti-freezing liquid (LLC) to aluminum alloy, so that the sealing performance of the portion tends to be deteriorated. 
         [0007]    If the sealing performance between the cylinder bore and the coolant water channel is deteriorated, the combustion gas enters the coolant water channel, and a circulation of the coolant water is hindered. This causes a major engine trouble. Therefore, sealing a cylinder bore side becomes more important than the sealing of a bolt hole side or an external portion side. In order to prevent the electric etching, it is important to prevent a coolant liquid in the coolant liquid channel from directly contacting the upper surface of the cylinder liner. Conventional technology was not good enough to prevent the electric etching caused by the contact of the coolant water with anti-freezing liquid, and did not focus on the relationship with the coolant water channel, even though a seal line is provided. As a result, the contact of the coolant liquid to the upper surface of the cylinder liner could not be fully prevented. 
         [0008]    The present invention has been made in order to solve the problems described above. An object of the present invention is to provide a cylinder head gasket for the open-deck type engine, and prevent the electric etching, which occurs due to the contact of the coolant water with anti-freezing liquid on the upper surface of the cylindrical portion forming the cylinder bore, and improve the sealing performance. 
         [0009]    Further objects and advantages of the invention will be apparent from the following description of the invention. 
       SUMMARY OF THE INVENTION 
       [0010]    In order to achieve the object described above, in a cylinder head gasket according to the invention, which is sandwiched between an open-deck type cylinder block and a cylinder head, and performs a sealing function, a first metal plate forms a folded portion at the peripheral border portion of a cylinder bore. A second metal plate is placed inside the folded portion by inserting an inner-periphery side flat portion of the second metal plate. In the second metal plate, a first half bead is formed on the outer periphery side of the inner-periphery side flat portion so that the flat portion on the outer peripheral side of the first half bead is placed on the folded portion side. In addition, inside the folded portion, a circular or annular bead plate, including a first full bead projecting to a first metal plate side, is laminated between the inner peripheral side flat portion of the second metal plate and the first metal plate. 
         [0011]    Also, an intermediate plate with a second half bead is placed between the outer-periphery side flat portion and the first metal plate. The second half bead slopes from a second metal plate side to the first metal plate side as the second half bead goes to the outer peripheral side from the inner peripheral side. The inner peripheral side of a sloping portion of the second half bead is disposed to correspond to a vicinity of the outer peripheral side of an inner cylindrical portion forming the cylinder bore of the cylinder block, or along the inner peripheral of the inner cylindrical portion. 
         [0012]    Also, in the cylinder head gasket, a second full bead may be provided between the first full bead and the second half bead on the first metal plate to project to the folded portion side. 
         [0013]    Alternatively, in the cylinder head gasket, a third metal plate is laminated on the first metal plate. The third metal plate includes a third full bead in a position facing the first full bead of the bead plate, and a third half bead in a position facing the second half bead of the intermediate plate. 
         [0014]    Alternatively, in order to achieve the object described above, in the cylinder head gasket according to the invention, which is sandwiched between the open-deck type cylinder block and the cylinder head, and performs the sealing function, the first metal plate forms the folded portion at the peripheral border portion of the cylinder bore. The second metal plate is inserted into the folded portion. In the folded portion, the circular or annular bead plate, including the first full bead projecting to the first metal plate side, is laminated between the first and second metal plates. Also, the intermediate plate with the second half bead is laminated on the outer peripheral side of the bead plate, and the second half bead slopes from the first metal plate side to the second metal plate side as the second half bead goes to the outer peripheral side from the inner peripheral side. 
         [0015]    Moreover, in the cylinder head gasket, a fourth metal plate is laminated on the folded portion side of the first metal plate. The fourth metal plate includes a fourth full bead which projects to the bead plate side in a position facing the first full bead of the bead plate, and a fourth half bead formed in the position facing the second half bead of the intermediate plate and slopes from the folded portion side of the first metal plate side to the second metal plate side as the fourth half bead goes to the outer peripheral side from the inner peripheral side. The inner peripheral side of the sloping portion of the fourth half bead is disposed to correspond to the outer peripheral side of the inner cylindrical portion forming the cylinder bore of the cylinder block, or along the inner peripheral of the inner cylindrical portion. 
         [0016]    Also, in the cylinder head gasket, a fifth metal plate is laminated on the first metal plate, and the fifth metal plate has a fifth full bead projecting to the bead plate side in a position facing the first full bead of the bead plate. 
         [0017]    According to the cylinder head gasket of the invention, the inner peripheral side of the sloping portion of the second or fourth half bead is disposed to correspond to the outer peripheral side of the inner cylindrical portion forming the cylinder bore of the cylinder block, or along the inner peripheral of the inner cylindrical portion. Accordingly, while the sealing performance between a coolant water channel and the cylinder bore is maintained, a contact portion with the anti-freezing liquid on the upper surface of the cylindrical portion forming the cylinder bore can be decreased and the contact of the anti-freezing liquid can be prevented. As a result, the electric etching, which occurs due to the anti-freezing liquid on the above-mentioned portion, can be prevented, and the sealing performance can be improved. Also, since a pressing force from the second or fourth half bead is generated along the outer peripheral of the inner cylindrical portion, stress generated in the inner cylindrical portion can be optimized. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a partial top plan view of a cylinder block of an open-deck type engine for explaining a structure of a cylinder head gasket of the first embodiment of the present invention; 
           [0019]      FIG. 2  is a cross sectional view taken along line  2 - 2  in  FIG. 1  showing the cylinder head gasket of the first embodiment of the present invention; 
           [0020]      FIG. 3  is a cross sectional view taken along line  3 - 3  in  FIG. 1  showing the cylinder head gasket of the first embodiment of the present invention; 
           [0021]      FIG. 4  is a partial top plan view of the cylinder block of the open-deck type engine for explaining the structure of the cylinder head gasket of the second embodiment of the present invention; 
           [0022]      FIG. 5  is a cross sectional view taken along line  5 - 5  in  FIG. 4  showing the cylinder head gasket of the second embodiment of the present invention; 
           [0023]      FIG. 6  is a cross sectional view taken along line  6 - 6  in  FIG. 4  showing the cylinder head gasket of the second embodiment of the present invention; 
           [0024]      FIG. 7  is a drawing corresponding to the cross sectional view taken along line  2 - 2  in  FIG. 1  showing the cylinder head gasket of a third embodiment of the present invention; 
           [0025]      FIG. 8  is a drawing corresponding to the cross sectional view taken along line  3 - 3  in  FIG. 1  showing the cylinder head gasket of the third embodiment of the present invention; 
           [0026]      FIG. 9  is a drawing corresponding to the cross sectional view taken along line  2 - 2  in  FIG. 1  showing the cylinder head gasket of a fourth embodiment of the present invention; 
           [0027]      FIG. 10  is a drawing corresponding to the cross sectional view taken along line  3 - 3  in  FIG. 1  showing the cylinder head gasket of the fourth embodiment of the present invention; 
           [0028]      FIG. 11  is a partial top view of the cylinder block of the open-deck type engine for explaining the structure of the cylinder head gasket as a reference; 
           [0029]      FIG. 12  is a cross sectional view taken along line  12 - 12  in  FIG. 11  showing the cylinder head gasket as a reference; 
           [0030]      FIG. 13  is a cross sectional view taken along line  13 - 13  in  FIG. 11  showing the cylinder head gasket as a reference; and 
           [0031]      FIG. 14  is a top plan view showing an example of the cylinder block of the open-deck type engine. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    Hereunder, embodiments of a cylinder head gasket according to the present invention will be described with reference to the attached drawings. Incidentally,  FIGS. 1 to 14  are schematic explanatory views in which sizes of sealing bores, cylinder liners, water holes and beads, shapes and so on are different from actual ones and enlarged for convenience. 
         [0033]    As shown in  FIGS. 2 ,  3 ,  5 ,  6 , cylinder head gaskets  1 ,  1 A of the embodiment of the invention are a metal gasket which is held between engine members, i.e. a cylinder head and a cylinder block (cylinder body), for an open-deck type engine for a multi-cylinder engine, and seals high-temperature and high-pressure combustion gas in a cylinder bore, and a fluid such as coolant water or oil and the like in a coolant water channel or a coolant oil channel and the like. 
         [0034]    In the open-deck type engine wherein the cylinder head gaskets  1 ,  1 A are used, as shown in  FIGS. 1 ,  4 ,  7 ,  14 , a cylinder block  50  is formed of a cylindrical portion (block liner)  52  wherein cylinder bores  51  are provided; and an outer wall portion  53 . Also, a coolant water channel (water jacket)  54  is formed between the cylindrical portion  52  and the outer wall portion  53 . The outer wall portion  53  has water holes  55 , oil holes  56  and bolt holes  57  for fastening bolts, and the cylindrical portion  52  also has the water holes  55 . 
         [0035]    In the cylinder block  50  of the open-deck type engine, the coolant water channel  54  is open on the contact surface to the cylinder head, so that it is difficult to maintain rigidity and the bore can be easily deformed. However, it has the advantage in cooling performance and also can be easily casted. Also, in the cylindrical portion  52 , cylinder sleeves (cylinder liners)  52   a  are fitted to a cylinder bores  51  side. The cylinder sleeves  52   a  are made of special cast iron which is excellent in terms of abrasion quality, seize resistance, heat resistance and strength. The cylindrical portion  52  and the outer wall portion are formed of aluminum alloy which has an excellent lightweight property. 
         [0036]    As shown in  FIGS. 2 ,  3 , the cylinder head gasket  1  of the first embodiment includes a first metal plate (metal plate: metal structural plate)  10 , a second metal plate  20 , a bead plate  30  and an intermediate plate  40 . The first and second metal plates  10 ,  20 , the bead plate  30  and the intermediate plate  40  are made of soft steel, annealed stainless (annealed material), or thermal refining stainless material (spring steel). Especially, the first metal plate  10  is made of annealed material which has an excellent heat resistance or corrosion resistance. The bead plate  30  is made of spring material which has an excellent elasticity. 
         [0037]    Also, these metal plates  10 ,  20 ,  40  are manufactured in accordance with a shape of the engine members such as the cylinder block and the like, and form cylinder bores (combustion chamber holes)  2 , water holes for circulating coolant water (not shown), oil holes for circulating lubricant oil (not shown), head bolt holes for fastening head bolts (not shown) and the like. 
         [0038]    As shown in  FIGS. 2 ,  3 , the first metal plate  10  is folded back at the peripheral border portion of the cylinder bore  2 , and forms a curved portion  11  and a folded portion (a flange portion)  12 . The second metal plate  20  is formed by inserting an inner-periphery side flat portion  21  of the second metal plate  20  into the folded portion  12 . In the second metal plate  20 , a first half bead  22  is provided on the outer periphery side of the inner-periphery side flat portion  21  and slopes toward a folded portion  12  side as the first half bead  22  goes to the outer periphery side. An outer-periphery side flat portion  23  of the first half bead  22  is placed at the same level as the folded portion  12  in a surface thickness direction. 
         [0039]    Also, inside the folded portion  12 , the circular or annular bead plate  30  is laminated between the inner-periphery side flat portion  21  of the second metal plate  20  and a base portion  10   a  the first metal plate  10 . The bead plate  30  includes a first full bead  31  which projects to the base portion  10   a  of the first metal plate  10 . Also, the intermediate plate  40  is laminated between the outer-periphery side flat portion  23  and the base portion  10   a  of the first metal plate  10 . The intermediate plate  40  is provided with a second half bead  42  which slopes from a second metal plate  20  side to the first metal plate  10  side as the second half bead  42  goes from the inner peripheral side to the outer peripheral side. An inner-peripheral side flat portion  41  which is formed on the inner peripheral side of the second half bead  42  is placed on the outer peripheral side of the first half bead  22 . Also, between the first full bead  31  and the second half bead  42 , a second full bead  13  which projects to the folded portion  12  is provided in base portion  10   a  of the first metal plate  10 . 
         [0040]    According to the structure, the folded portion  12  can prevent the combustion gas from exposing to the second metal plate  20  and the bead plate  30 , so that the first metal plate  10  can be made of material which has an excellent heat resistance or corrosion resistance. The second metal plate  20  or the bead plate can be made of material which has an excellent elasticity. Accordingly, the gasket  1  can be made by a combination wherein characteristics of each material are applied. Therefore, a gasket with various kinds of excellent features such as a sealing performance, heat resistance, corrosion resistance, durability and the like, can be made. 
         [0041]    Also, since the first half bead  22  is provided, the inner-periphery side flat portion  21  of the first half bead  22  can be easily housed inside the folded portion  12 , so that a portion  21  of the second metal plate  20  can be easily inserted into the folded portion  12 , even when a width of a guard portion of the cylindrical portion  52  is narrow. As a result, the elasticity of the folded portion  12  can be improved, and cracking can be prevented due to a stopping function of the insertion portion  21 . 
         [0042]    Due to the structure with the second full bead  13 , when a pressing force toward the cylinder head gasket  1  increases and the first full bead  31  is pressed, the second full bead  13  can distribute the pressing force and prevent a creep relaxation of the first full bead  31 . 
         [0043]    In the invention, as shown in  FIGS. 1 to 3 , a position  42   a  on the inner peripheral side of a sloping portion of the second half bead  42  is placed to match a position  52   b  on the outer peripheral side (outer wall surface) of the inner cylindrical portion  12 . Due to this structure, the position  42   a  of an angular portion of the second half bead  42  corresponds to the outer wall surface  52   b  of the cylindrical portion  52 , so that coolant water barely enters into the upper surface of the cylindrical portion  52 . Therefore, electric etching, which occurs due to low-freezing liquid coolant water on the upper surface of the cylindrical portion  52  forming the cylinder bores  51 , can be prevented, and the sealing performance can be improved. Incidentally, in the cylinder head gasket  1  with the structure shown in  FIGS. 1 to 3 , an experimental result shows that an amount of distortion decreases approximately 12% in the average at four portions compared to a standard product made by a conventional technology. 
         [0044]    Next, a second embodiment will be explained. As shown in  FIGS. 4 to 6 , the cylinder head gasket  1 A of the second embodiment has the position  42   a  on the inner peripheral side of the sloping portion of the second half bead  42  provided in an intermediate plate  40 A along the position  52   b  on the outer peripheral side of the inner cylindrical portion  12 . More specifically, for example, with a predetermined distance D, the position (shown by dotted lines in  FIG. 4 )  42   a  on the inner peripheral side of the sloping portion of the second half bead  42  is situated at further inner peripheral side of the position  52   b  on the outer peripheral side of the inner cylindrical portion  12 . The distance D is less than the width of the bead  42 . Other structures are the same as those of the cylinder head gasket  1  of the first embodiment. 
         [0045]    Due to this structure, the position  42   a  of the angular portion of the second half bead  42  is designed to be in the inner peripheral side with the predetermined distance D along the outer wall surface  52   b  of the cylindrical portion  52 . Accordingly, a portion on the upper surface of the cylindrical portion  52 , where the coolant water enters in, is limited to a very narrow area. Therefore, the electric etching, which occurs due to the anti-freezing liquid on the upper surface of the cylindrical portion  52  forming the cylinder bores  51 , can be substantially prevented, and the sealing performance can be improved. Incidentally, the predetermined distance does not have to be necessarily fixed distance D, but may be changed. 
         [0046]    Next, a third embodiment will be explained. As shown in  FIGS. 7 ,  8 , a cylinder head gasket  1 B of the third embodiment omits the second full bead  13  in the first metal plate  10  of the cylinder head gasket  1 B of the first embodiment in  FIGS. 1 to 3 , and a new third metal plate  60  is laminated on the base portion of the first metal plate  10 . The third metal plate  60  includes a third full bead  61  in a position facing the first full bead  31  of the bead plate  30 . Moreover, a third half bead  62  is formed in a position approximately facing the second half bead  42  of the intermediate plate  40 . The third full bead  61  is formed in such a way as to project to a bead plate  30  side. Also, the third half bead  62  is formed in such a way as to come close to the first metal plate  10  side as the third half bead  62  goes to the outer peripheral side from the inner peripheral side. More specifically, the third metal plate  60  abuts against base portion of the first metal plate  10  side on the outer peripheral side of the third half bead  62 . Other than the above-mentioned structure, the structure of the third embodiment is the same as that of the cylinder head gasket  1  of the first embodiment. 
         [0047]    Due to this structure, in addition to the above-mentioned operational effect of the cylinder head gasket  1  of the first embodiment, the spring performance can be improved in portions of the first full bead  31  and the second half bead  42 . Incidentally, since there is no second full bead  13 , the number of seal lines decreases. 
         [0048]    Also, in the cylinder head gasket  1 A of the second embodiment, a cylinder head gasket may be composed by omitting the second full bead  13  and laminating the new third metal plate  60  on the first metal plate  10 , as in the third embodiment. 
         [0049]    Next, the fourth embodiment will be explained. As shown in  FIGS. 9 ,  10 , a cylinder head gasket  1 C of the fourth embodiment is held between the open-deck type cylinder block  50  and the cylinder head and performs a sealing function. The first metal plate  10  is folded back at the peripheral border portion of the cylinder bore  2  and forms the folded portion  12 . Also, the second metal plate  20  is inserted into the folded portion  12 . Inside the folded portion  12 , the circular bead plate  30  is laminated between the second metal plate  20  and the first metal plate  10 , and includes the first full bead  31  which projects to the first metal plate  10 . 
         [0050]    Also, the intermediate plate  40  is laminated and provided with the second half bead  42 . The second half bead  42  slopes from the first metal plate  10  side to the second metal plate  20  side as the second half bead  42  goes from the inner peripheral side to the outer peripheral side on the outer peripheral side of the bead plate  30 . Moreover, a fourth metal plate  70  is laminated on the folded portion  12  side of the first metal plate  10 . 
         [0051]    The fourth metal plate  70  has a fourth full bead  71  in a position facing the first full bead  31  of the bead plate  30 . The fourth full bead  71  projects to the bead plate  30  side. Also, a fourth half bead  72  is provided in a position facing the second half bead  42  of the intermediate plate  40 . The fourth half bead  72  slopes from the folded portion  12  side of the first metal plate  10  side to the second metal plate  20  side. Also, a fifth metal plate  80  has a fifth full bead  81  which projects to the bead plate  30  side in a position facing the first full bead  31  of the bead plate  30 . By providing the fifth full bead  81 , the spring performance can be improved in the portion of the first full bead  31 . 
         [0052]    A position  72   a  on the inner peripheral side of a sloping portion of the fourth half bead  72  is placed to match the position  52   b  on the outer peripheral side of the inner cylindrical portion  52  which forms the cylinder bores  51  of the cylinder block  50 . Due to this structure, the position  72   a  of an angular portion of the fourth half bead  72  corresponds to the outer wall surface  52   b  of the cylindrical portion  52 , so that the coolant water hardly enters into the upper surface of the cylindrical portion  52 . Therefore, electric etching, which occurs due to the anti-freezing liquid on the upper surface of the cylindrical portion  52  forming the cylinder bores  51 , can be prevented, and the sealing performance can be improved. 
         [0053]    Although it is not shown in the figures, the position  72   a  on the inner peripheral side of the sloping portion of the fourth half bead  72  is placed along the inner peripheral side of the position  52   b  on the outer peripheral side of the cylindrical portion  52  which forms the cylinder bores  51  of the cylinder block  50 , for example, with the predetermined distance D. Due to this structure, the portion  72   a  of the angular portion of the fourth half bead  72  is placed on the inner peripheral side with the predetermined distance D along the outer wall surface  52   b  of the cylindrical portion  52 . Accordingly, the portion of the upper surface of the cylindrical portion  52  wherein the coolant water contacts is limited to a very narrow area. Therefore, electric etching, which occurs due to the anti-freezing liquid on the upper surface of the cylindrical portion  52  forming the cylinder bores  51 , can be prevented, and the sealing performance can be improved. Incidentally, the predetermined distance does not have to be necessarily fixed, but it may be changed. 
         [0054]    In addition, for reference,  FIGS. 11 to 13  show a cylinder head gasket  1 X, wherein the position  42   a  of the angular portion of the second half bead  42  is placed with a predetermined distance Wx from the cylinder bore  2  without extending along the outer wall surface  52   b  of the cylindrical portion  52 . In this structure, as shown in  FIG. 11 , a distance Wx+Wy between the coolant water channel  54  and the cylinder bores  51  in the cylinder block  50  changes, so that the distance Wy between the position  42   a  on the inner peripheral side of the sloping portion of the second half bead  42  and the position  52   b  on the outer peripheral side of the inner cylindrical portion  12  changes. As shown in  FIGS. 11 ,  12 , the distance Wy is small at a vicinity of the bolt holes  57 . However, as shown in  FIGS. 11 ,  13 , the distance Wy becomes larger in a central part between the respective bolt holes  57 , so that the coolant water enters into the upper surface of the cylindrical portion  52 . Therefore, electric etching, which occurs due to the low-freezing liquid coolant water, cannot be prevented on the upper surface of the cylindrical portion  52  forming the cylinder bores  51 . 
         [0055]    The disclosure of Japanese Patent Application No. 2007-042213, filed on Feb. 22, 2007, is incorporated in the application. 
         [0056]    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.