Abstract:
A cylinder head gasket for an open deck engine includes a first metal plate having a folded portion extending from a curved portion and located under the base portion, and a second metal plate having an inner portion disposed on the folded portion, an outer portion outside the inner portion and a first half bead provided between the inner and outer portions. An annular bead plate having a full bead is provided on the inner portion of the second metal plate, and an intermediate plate is provided on the outer portion of the second metal plate, wherein an inner end portion of the intermediate plate is disposed under an outer edge of the annular bead plate. A total thickness of the metal plates at the flange is equal to a total thickness of the metal plates outside the flange including the inner end portion.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
       [0001]    The present invention relates to a cylinder head gasket sandwiched between a cylinder head and a cylinder block of an open deck type engine for sealing. 
         [0002]    A cylinder head gasket is tightened by head bolts and sandwiched between engine members such as a cylinder head, a cylinder block (cylinder body) or the like, of an automobile engine for sealing fluids such as combustion gas, oil, coolant or the like. 
         [0003]    On the other hand, an engine can be distinguished based on a form of a cylinder block into a closed type engine having no coolant passage at a contact surface of a cylinder head at a cylinder block, and an open deck type engine having a contact surface which is open as a coolant passage of a cylinder head at a cylinder block. As shown in  FIG. 10 , the open deck type engine includes a coolant passage (water jacket)  62  at a portion close to a cylinder head of an engine block  60 , and is advantageous in terms of a cooling ability and a reduction in weight thereof. In addition, it is easy to produce the open deck type engine because of an opening portion therein. 
         [0004]    Regarding a cylinder head gasket for the open deck type engine, a metal gasket has been provided with a grommet along an inner periphery of a cylinder hole in a base plate to be inserted to bridge a cylinder portion of a cylinder block and an outer wall portion forming an outer side of a coolant passage. The thickest portion of the grommet formed at the inner side of a cylinder sleeve seals combustion gas of a cylinder bore. Also, step beads formed on both sides of the coolant passage seal the coolant (For example, refer to Japanese Patent Document 1: Japanese Patent Publication No. H10-281290). 
         [0005]    In the cylinder head gasket, the step beads are provided for sealing the coolant between the coolant passage and the cylinder bore. The step beads have a portion thicker at an inner periphery side and a portion thinner at an outer periphery side on an upper surface of an inner cylindrical portion of the cylinder block. Therefore, when a large pressing force is applied to the step beads, a large surface pressure is applied to the inner periphery side, thereby making the pressing force difficult to be optimized. In addition, a moment, inclining toward inner side, acts on the upper portion of the inner cylindrical portion, thereby deforming the cylinder bore. 
         [0006]    The present invention has been made to solve the above-mentioned problems and provides a cylinder head gasket to be used for an open deck type engine. The cylinder head gasket adjusts a surface pressure on an upper surface of a cylinder portion forming a cylinder bore of a cylinder block, thereby reducing deformation of the cylinder bore and preventing the cylinder bore from buckling. 
         [0007]    Further objects and advantages of the invention will be apparent from the following description of the invention. 
       SUMMARY OF THE INVENTION 
       [0008]    In order to achieve the objects, a cylinder head gasket according to the present invention is sandwiched between a cylinder block and a cylinder head of an open deck type engine for exerting its sealing ability. The cylinder head gasket comprises a first metal base plate including a folded portion formed at a peripheral portion of a cylinder bore thereof; and a second metal base plate formed by inserting an inner peripheral flat portion of the second metal base plate into the folded portion. The second metal base plate is provided with a first half bead at the outer peripheral side of the inner peripheral flat portion and an outer peripheral side flat portion of the first half bead formed on a side of the folded portion. Furthermore, a circular or annular bead plate having a first full bead projecting toward the first metal base plate is laminated between the inner peripheral flat portion in the second metal base plate and the first metal base plate inside the folded portion. 
         [0009]    In the cylinder head gasket, an outer peripheral side end portion of a slope portion of the first half bead is disposed at the inner peripheral side of the outer peripheral position of an inner cylindrical portion forming the cylinder bore of the cylinder block. An outer peripheral side end portion of the bead plate extends to the outer peripheral position of the inner cylindrical portion or a position close to the outer peripheral and forms the bead plate. Furthermore, a flat portion in an intermediate plate is disposed at the outer peripheral side of the first half bead, wherein a total thickness of each metal plate at the position of the first full bead and a total thickness of each metal plate at the position of the outer peripheral side end portion of the bead plate are designed to be equal. With this structure, when a large pressing force is applied to the cylinder head gasket, the total thicknesses at the inner peripheral side and the outer peripheral side of the inner cylindrical portion become equal. Thus, it is possible to equalize the pressing force at the inner peripheral side and the outer peripheral side of the inner cylindrical portion, thereby optimizing a stress generated on the inner cylindrical portion. 
         [0010]    In the cylinder head gasket, a second half bead is provided at the outer peripheral side of the inner cylindrical portion of the cylinder block, a third half bead is provided at the outer peripheral side of the outer wall surface of a coolant passage formed around the inner cylindrical portion, and the intermediate plate is formed to space between the second half bead and the third half bead at a side of the first metal base plate. Thus, it is possible to improve the ability for sealing the coolant passage. 
         [0011]    In addition, in the cylinder head gasket described above, a third metal base plate is laminated at a side opposite to the folded portion in the first metal base plate, wherein a second full bead is provided with a projection facing a projection of the first full bead. A fourth half bead and a fifth half bead are provided to face the second half bead and the third half bead, respectively, in such a way that a space between the fourth half bead and the fifth half bead faces a side of the second metal base plate. Therefore, sealing abilities for the cylinder bore and the coolant passage can be further improved because of the third metal base plate. 
         [0012]    According to the cylinder head gasket of the present invention, the outer peripheral side of the bead plate inside the folded portion is extended to the outer peripheral position of the inner cylindrical portion (block liner) of the cylinder block of an open deck type engine for equalizing the pressing forces at the inner peripheral side and the outer peripheral side of the inner cylindrical portion, thereby optimizing a sealing surface pressure applied to the inner cylindrical portion and a stress generated on the inner cylindrical portion. As a result, deformation of the inner cylindrical portion can be reduced, and buckling can be prevented. Also, a moment inclining toward inside the upper surface and applied to the inner cylindrical portion is reduced, thereby reducing the deformation of the cylinder bore. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a partial top plan view of a cylinder block of an open deck type engine for explanation of a structure of a cylinder head gasket according to a first embodiment of the present invention; 
           [0014]      FIG. 2  is a sectional view taken along line  2 - 2  in  FIG. 1  showing the cylinder head gasket according to the first embodiment of the present invention; 
           [0015]      FIG. 3  is a sectional view taken along line  3 - 3  in  FIG. 1  showing the cylinder head gasket according to the first embodiment of the present invention; 
           [0016]      FIG. 4  is a partial sectional view showing another cylinder head gasket according to the first embodiment of the present invention corresponding to the sectional view taken along line  2 - 2  in  FIG. 1 ; 
           [0017]      FIG. 5  is a partial sectional view showing another cylinder head gasket according to the first embodiment of the present invention corresponding to the sectional view taken along line  3 - 3  in  FIG. 1 ; 
           [0018]      FIG. 6  is a partial sectional view showing a cylinder head gasket according to a second embodiment of the present invention corresponding to the sectional view taken along line  2 - 2  in  FIG. 1 ; 
           [0019]      FIG. 7  is a partial sectional view showing the cylinder head gasket according to the second embodiment of the present invention corresponding to the sectional view taken along line  3 - 3  in  FIG. 1 ; 
           [0020]      FIG. 8  is a partial sectional view showing another cylinder head gasket according to the second embodiment of the present invention corresponding to the sectional view taken along line  2 - 2  in  FIG. 1 ; 
           [0021]      FIG. 9  is a partial sectional view showing another cylinder head gasket according to the second embodiment of the present invention corresponding to the sectional view taken along line  3 - 3  in  FIG. 1 ; and 
           [0022]      FIG. 10  is a top plan view showing an example of a conventional type cylinder block of an open deck type engine. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0023]    Next, embodiments of a cylinder head gasket according to the present invention will be explained with reference to the drawings.  FIGS. 1 to 10  are schematic illustrations showing cylinder bores, cylinder liners, water holes, and beads. The sizes of the cylinder bores and the sizes and shapes of the cylinder lines, water holes, and beads, are made different from the actual ones for convenience in explaining the configuration thereof. 
         [0024]    As shown in  FIGS. 2 to 9 , cylinder head gaskets  1  and  1 A according to the embodiments of the present invention are metal gaskets to be sandwiched between engine members such as a cylinder head and a cylinder block (cylinder body) of an open deck type engine for a multi-cylinder engine, and seal fluids such as combustion gas with a high temperature and a high pressure of the cylinder bores, coolant in a coolant passage and oil in a cooling oil passage, and the like. 
         [0025]    In the open deck type engine with such cylinder head gaskets  1  and  1 A, as shown in  FIGS. 1 and 10 , a cylinder block  60  is formed of a cylinder portion (block liner)  62  provided with a cylinder bore  61  and an outer wall portion  63 . A coolant passage (water jacket)  64  is formed by the inner cylindrical portion  62  and the outer wall portion  63 . Also, water holes  65 , oil holes  66 , and bolt holes  67  for tightening bolts are provided in the outer wall portion  63 . The water holes  65  are also provided in the cylinder portion  62 . 
         [0026]    The cylinder portion  62  is engaged with a cylinder sleeve (cylinder liner)  62   a  at a side of the cylinder bores  61 . The cylinder sleeve  62   a  is formed of a special cast iron with an abrasion resistance, a sear resistance, a heat resistance, and strength. The cylinder portion  62  and the outer wall portion  63  are formed of an aluminum alloy with light weight properties. 
         [0027]    In the cylinder block  60  of the open deck type engine, the coolant passage  64  is opened on a contact surface of the cylinder block  60  with the cylinder head. Thus, it is difficult to maintain the rigidity thereof, thereby easily deforming the bores. However, an advantage in a cooling ability can be obtained and it is easy to cast. 
         [0028]    As shown in  FIGS. 2 to 5 , the cylinder head gasket  1  according to the first embodiment of the present invention comprises a first metal base plate (a first surface plate)  10 , a second metal base plate (a second surface plate)  20 , a bead plate  30 , and an intermediate plate  40 . The first and second metal base plates  10 ,  20 , the bead plate  30 , and the intermediate plate  40  are formed of a mild steel plate, a stainless annealed material (anneal material), stainless thermal refining steel material (spring steel plate), and the like. Especially, an anneal material with heat resistance and corrosion resistance is used for the first metal base plate  10 . A spring material with elasticity can be used for the bead plate  30 . 
         [0029]    In addition, these metal base plates  10 ,  20 , and  40  are produced so that they correspond to the shapes of the engine members such as a cylinder block and the like, and provided with cylinder bores (combustion chamber holes)  2 , water holes for circulation of the coolant (not shown), oil holes for circulation of lubricant oil (not shown), head bolt holes for tightening head bolt (not shown) therein. 
         [0030]    As shown in  FIGS. 2 to 5 , a curved portion  11  and a folded portion (flange portion)  12  are formed by folding the first surface plate  10  at a periphery portion of the cylinder bore  2 . The second surface plate  20  is formed by inserting an inner peripheral flat portion  21  into the folded portion  12 . The second surface plate  20  is provided with a first half bead  22  gradually inclining toward the folded portion  12  at the outer periphery side of the inner peripheral flat portion  21 . An outer peripheral side flat portion  23  of the first half bead  22  is provided at a side of the folded portion  12  in a direction of the thickness. 
         [0031]    The bead plate  30  in a circular or annular shape is laminated on the inner peripheral flat portion  21  between the inner peripheral flat portion  21  in the second metal base plate  20  and a base portion  10   a  of the first metal base plate  10  inside the folded portion  12 . The bead plate  30  is provided with a first full bead  31  projecting toward the base portion  10   a  of the first surface plate  10  therein. 
         [0032]    Moreover, the intermediate plate  40  is disposed between the outer peripheral side flat portion  23  and the base portion  10   a  of the first metal base plate  10 . The intermediate plate  40  is provided with a second half bead  42  gradually sloping from the inner peripheral side to the outer peripheral side toward the base portion  10   a  of the first base metal plate  10  from the second metal base plate  20 . Also, the intermediate plate  40  is provided with a third half bead  44  gradually sloping down from the inner peripheral side to the outer peripheral side toward the second metal base plate  20  from the base portion  10   a  of the first metal base plate  10  at the outer peripheral side of the coolant passage  64 , i.e. above the outer wall portion  63 . An inner peripheral flat portion  41  formed at the inner peripheral side of the second half bead  42  is disposed at the outer peripheral side of the first half bead  22 . 
         [0033]    According to the structure, the folded portion  12  prevents the combustion gas from contacting the second metal base plate  20  and the bead plate  30 . Therefore, a material with heat and corrosion resistances can be used for the first metal base plate  10 , and a material with elasticity can be used for the second metal base plate  20  and the bead plate  30 . Accordingly, it is possible to form the gasket  1  of a combination of materials having properties different from each other. As a result, it is possible to produce the gasket with excellent properties in sealing ability, heat resistance, corrosion resistance, durability, and the like. 
         [0034]    The first half bead  22  is provided, so that the inner peripheral flat portion  21  thereof can be easily stored inside the folded portion  12 . Even if a width of a guard portion of the inner cylindrical portion  52  is narrow, it is still possible to insert the inner peripheral flat portion  21  as a part of the second metal base plate  20  into the folded portion  12 . Therefore, elasticity of the folded portion  12  can be improved, and cracking due to a stopping function of the inner peripheral flat portion  21  can be prevented. 
         [0035]    In the present invention, as shown in  FIGS. 1 to 5 , the outer peripheral side end portion of the slope portion of the first half bead  22  is disposed closer to the inner peripheral side than the outer peripheral position  62   b  of the inner cylindrical portion  62  forming the cylinder bore of the cylinder block  60 . An outer peripheral side end portion  30   a  of the bead plate  30  extends to an outer peripheral position  62   a  ( FIGS. 1 to 3 ) of the inner cylinder portion  62  or a position ( FIGS. 4 and 5 ) close to the outer peripheral position  62   a  for forming the bead plate  30 . Additionally, the flat portion  41  in the intermediate plate  40  is disposed at the outer peripheral side of the first half bead  22 , and a total thickness of the metal plates  10 ,  30 ,  20 , and  40  at the position of the first full bead  31  and a total thickness of the metal plates  10 ,  30 ,  40 , and  20  at the outer peripheral position  62   b  of the inner cylindrical portion  62  are equalized. 
         [0036]    With this structure, when a large pressing force is applied to the cylinder head gasket  1 , the total thicknesses at the inner peripheral side and at the outer peripheral side of the inner cylindrical portion  62  become equal. Accordingly, the pressing forces at the inner peripheral side and at outer peripheral side of the inner cylindrical portion  62  can be equalized, thereby optimizing the stress generated on the inner cylindrical portion  62 . According to the experimental results in which the cylinder head gasket  1  with the structures in  FIGS. 1 to 3  has been used, an average of amount of distortion at four portions is reduced by 9%. 
         [0037]    Incidentally, as an example of the plate thicknesses described above, the first metal base plate  10  and the intermediate plate  30  are formed of a plate thickness t 1 , respectively, the second metal base plate  20  is formed of a plate thickness t 2  (t 2 =1.2×t 1 ), and the bead plate  30  is formed of a plate thickness t 3  (t 3 =0.6×t 1 ). 
         [0038]    Next, a second embodiment of the present invention will be explained. As shown in  FIGS. 6 to 9 , the cylinder head gasket  1 A according to the second embodiment of the present invention comprises a third metal base plate  50  laminated at a side opposite to the folded portion  12  in the first metal base plate  10  in addition to the structure of the cylinder head gasket  1  according to the first embodiment. The third metal base plate  50  is provided with a second full bead  51  projecting toward the first full bead  31 , said both first and second beads facing each other. Furthermore, a fourth half bead  53  and a fifth half bead  55  are provided to face the second half bead  42  and the third half bead  44 , respectively, in such a way that a flat portion  54  between the fourth half bead  53  and the fifth half bead  55  is provided at a side of the second metal base plate  20 . 
         [0039]    According to the structure with the third metal base plate, the second full bead  51  is overlapped with the first full bead  31 , the fourth half bead  53  and the fifth half bead  55  are overlapped with the second half bead  42  and the third half bead  44 , respectively. Therefore, it is possible to generate large sealing surface pressures at those portions, thereby further improving sealing abilities for the cylinder bore  61  and the coolant passage  64 . 
         [0040]    As an example of the plate thicknesses described above, the first metal base plate  10  and the intermediate plate  30  are formed of a plate of thickness t 1 , respectively. The second metal base plate  20  is formed of a plate of thickness t 2  (t 2 =1.2×t 1 ). The bead plate  30  is formed of a plate of thickness t 3  (t 3 =0.6×t 1 ). In addition, the third metal base plate  50  is formed of a plate of thickness t 4  (t 4 =0.8×t 1 ). 
         [0041]    The disclosure of Japanese Patent Application No. 2007-042299, filed on Feb. 22, 2007, is incorporated in the application. 
         [0042]    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.