Patent Publication Number: US-8113162-B2

Title: Cylinder head cover

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a cylinder head cover attached to an upper portion of a cylinder head of an engine and, more particularly, to a cylinder head cover incorporating an oil control valve for controlling hydraulic oil. 
     Conventionally, as one such type of cylinder head cover, a configuration disclosed in, for example, Japanese Laid-Open Patent Publication No. 2006-17085 has been proposed.  FIG. 8  shows the conventional configuration. As illustrated in  FIG. 8 , a tubular valve casing  32  is molded integrally with an outer shell portion  31   a  of a cylinder head cover  31 . The outer shell portion  31   a  is formed of synthetic resin and the valve casing  32  is formed of metal. A valve body  33  of an oil control valve is inserted into the valve casing  32  through an opening  32   a , which is formed at one end of the valve casing  32 , and is incorporated in the valve casing  32 . A seal ring  34  is attached to a portion of the outer circumference of the valve body  33  located in the vicinity of the opening  32   a  of the valve casing  32 . The seal ring  34  is arranged between the inner circumferential surface of the valve casing  32  and the outer circumferential surface of the valve body  33 . 
     The outer shell portion  31   a  formed of synthetic resin and the valve casing  32  formed of metal have different heat expansion coefficients. Accordingly, if, for example, the temperature in the engine compartment rises, a gap may form in a boundary portion  35  between the outer shell portion  31   a  and the valve casing  32 , leading to leakage of oil. 
     To solve the problem, the following configurations, for example, have been proposed conventionally. 
     (1) With adhesive applied to the outer circumferential surface of the valve casing  32 , the outer shell portion  31   a  of the cylinder head cover  31  is molded onto the outer circumference of the valve casing  32 . This bonds and fixes the outer shell portion  31   a  and the valve casing  32  to each other at the boundary portion  35 . 
     (2) With reference to  FIG. 9 , an annular groove  36  is provided in the outer circumferential surface of the valve casing  32 . The groove  36  is filled with synthetic resin at the same time as the outer shell portion  31   a  is molded. The resin in the groove  36  is integrated with the resin forming the outer shell portion  31   a.    
     (3) Also referring to  FIG. 9 , a seal ring  37  formed of elastic foaming material is attached to the outer circumferential surface of the valve casing  32  and then, in this state, the outer shell portion  31   a  of the cylinder head cover  31  is molded. In this manner, the boundary portion  35  between the outer shell portion  31   a  and the valve casing  32  is sealed by the seal ring  37  held in a compressed state. 
     (4) As illustrated in  FIG. 10 , an annular groove  36  is formed in the outer circumferential surface of the valve casing  32  and a gel-like sealing material  40  is caused to fill the groove  36  and caused to foam. When the outer shell portion  31   a  is molded, the synthetic resin in the groove  36  and the synthetic resin forming the outer shell portion  31   a  are integrated, and the boundary portion  35  is sealed by the seal ring  37  in the compressed state. 
     However, in the method using the adhesive as described in the item (1), when the synthetic resin is caused to fill a mold with the valve casing  32  set in the mold to form the outer shell portion  31   a , the pressure of the synthetic resin, which is to be molded, is likely to urge the adhesive to flow out of the outer circumferential surface of the valve casing  32 . This may make it impossible to effectively bond the outer shell portion  31   a  and the valve casing  32  together with the adhesive. Further, if the flowed out adhesive remains on the outer end surface of the valve casing  32 , the appearance is degraded. Also, if the adhesive remains in the outer shell portion  31   a  as impurity, the oil may leak from the corresponding portion of the outer shell portion  31   a.    
     If the method using the groove  36  as described in the above item (2) is employed, the outer shell portion  31   a  and the valve casing  32  can be fixed by the anchor effect so that the outer shell portion  31   a  and the valve casing  32  are not displaced with respect to each other. However, the formation of a gap between the valve casing  32  and the outer shell portion  31   a  cannot be prevented. Thus, the oil is likely to leak from the boundary portion  35 . 
     In the method employing the seal ring  37  as described in the above items (3) and (4), when the synthetic resin is caused to fill the mold in which the valve casing  32  is set in order to form the outer shell portion  31   a , the filling pressure of the synthetic resin must be set to an appropriate value. Otherwise, the seal ring  37  may not be allowed to seal the boundary portion  35 . Specifically, if the filling pressure is insufficient, the seal ring  37  cannot be compressed to an appropriate extent and repulsive force necessary for sealing cannot be ensured. In contrast, if the filling pressure is excessively high, a great amount of synthetic resin may go over a parting line of the mold and causes a burr in a product. This complicates the post-molding process since the burr must be removed. 
     SUMMARY OF THE INVENTION 
     The present invention was made for solving the above problems in the prior art. It is an objective of the invention to provide a cylinder head cover that prevents oil from leaking to the exterior from a boundary portion between an outer shell portion formed of synthetic resin and a valve casing formed of metal. 
     To achieve the foregoing objective and in accordance with one aspect of the present invention, a cylinder head cover including an outer shell portion, a tubular valve casing, a valve body, an annular projection, and a seal ring is provided. The outer shell portion is formed of a synthetic resin. The tubular valve casing is formed of a metal and molded with the outer shell portion. The valve body is inserted into the valve casing through an opening formed at an end of the valve casing and incorporated in the valve casing. The annular projection is formed in the outer shell portion and projects toward the opening of the valve casing in such a manner as to cover a boundary portion between the outer shell portion and the valve casing. The seal ring is arranged between the projection and the valve body. 
     Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1  is a schematic diagram showing an engine with a cylinder head cover according to one embodiment of the present invention; 
         FIG. 2  is a cross-sectional view showing a portion of a cylinder head cover according to a first embodiment; 
         FIG. 3  is an exploded cross-sectional view showing a portion of the cylinder head cover illustrated in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view showing a portion of a cylinder head cover according to a second embodiment of the invention; 
         FIG. 5  is a cross-sectional view showing a portion of a cylinder head cover according to a third embodiment of the invention; 
         FIG. 6  is a cross-sectional view showing a portion of a cylinder head cover according to a fourth embodiment of the invention; 
         FIG. 7  is a cross-sectional view showing a portion of a cylinder head cover according to a fifth embodiment of the invention; 
         FIG. 8  is a cross-sectional view showing a portion of a conventional cylinder head cover; 
         FIG. 9  is a cross-sectional view showing a portion of another conventional cylinder head cover; and 
         FIG. 10  is a cross-sectional view showing a portion of another conventional cylinder head cover. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A first embodiment of the present invention will now be described with reference to  FIGS. 1 to 3 . As shown in  FIG. 1 , a cylinder head cover  11  is fixed to an upper portion of a cylinder block (which includes a cylinder head) of an engine  10 . With reference to  FIG. 2 , an outer shell portion  11   a  of the cylinder head cover  11  is molded as an integral body using heat-resistant synthetic resin. A cylindrical valve casing  12  formed of metal is molded with the outer shell portion  11   a . A groove  13  is formed in the outer circumference of the valve casing  12 . The groove  13  is filled with synthetic resin when the outer shell portion  11   a  is molded. This fixes the outer shell portion  11   a  and the valve casing  12  so that the outer shell portion  11   a  and the valve casing  12  are not displaced with respect to each other. 
     An opening  12   a  is formed in an outer end (the left end as viewed in  FIG. 2 ) of the valve casing  12 . An annular recess  14  is provided in the inner circumference of the opening  12   a . An annular projection  15 , which projects toward the opening  12   a , is formed in the outer shell portion  11   a  of the cylinder head cover  11 . A cylindrical entering portion  15   a  projects from the inner edge of the projection  15 . The entering portion  15   a  is inserted into the recess  14  along the axial direction of the recess  14 . The outer end of the valve casing  12  is thus clamped by the entering portion  15   a  and the outer shell portion  11   a  from inside and outside. 
     A valve body  16  of an oil control valve is inserted from the opening  12   a  of the valve casing  12  and incorporated in the valve casing  12 . A seal ring  17  is attached to a portion of the outer circumference of the valve body  16  corresponding to the opening  12   a  of the valve casing  12 . The seal ring  17  is located between the inner circumferential surface of the entering portion  15   a  of the projection  15  and the outer circumferential surface of the valve body  16 . A plurality of oil grooves  18  having oil holes  18   a  are formed in the outer circumferential surface of the valve body  16 . The inner end (the right end as viewed in  FIG. 2 ) of the entering portion  15   a  is arranged in such a manner that, when the valve body  16  is incorporated in the valve casing  12 , this end is located outward from the outermost one of the oil grooves  18 . 
     In the cylinder head cover  11  constructed as described above, the sealing performance between the valve casing  12  and the valve body  16  is maintained through the engagement between the entering portion  15   a  and the seal ring  17 . As a result, even if a gap forms between the valve casing  12  and the outer shell portion  11   a , the gap is prevented from communicating with the exterior. 
     The first embodiment has the following advantages. 
     (1) The annular projection  15 , which is provided in the outer shell portion  11   a , covers the boundary portion  19  between the inner circumferential surface of the outer shell portion  11   a  and the outer circumferential surface of the valve casing  12 . Further, the seal ring  17 , which is attached to the outer circumference of the valve body  16 , seals the boundary portion between the inner circumferential surface of the projection  15  and the outer circumferential surface of the valve body  16 . This configuration prevents oil from leaking to the exterior from the boundary portion  19  between the outer shell portion  11   a  formed of synthetic resin and the valve casing  12  formed of metal. 
     (2) The entering portion  15   a  extending from the inner edge of the projection  15  is inserted into the recess  14 , which is formed in the inner surface of the end of the valve casing  12 . The end of the valve casing  12  in the vicinity of the opening  12   a  is clamped by the entering portion  15   a  and the outer shell portion  11   a . This suppresses deformation of the projection  15  in a manner separating from the end surface of the opening  12   a  of the valve casing  12  due to the difference between the thermal expansion rate of the outer shell portion  11   a  formed of synthetic resin and the thermal expansion rate of the valve casing  12  formed of metal. This, in turn, suppresses movement of the outer shell portion  11   a  caused by such deformation. Formation of a gap between the outer shell portion  11   a  and the valve casing  12  is thus prevented and, as a result, leakage of the oil to the exterior is effectively prevented. 
     (3) As has been described, since leakage of the oil to the exterior is prevented, it is unnecessary to apply adhesive between the outer shell portion  11   a  and the valve casing  12 . As a result, degradation of the appearance caused by the adhesive that has been urged to flow out is prevented. 
     Second Embodiment 
     A second embodiment of the present invention will hereafter be explained mainly about the differences from the first embodiment. 
     As illustrated in  FIG. 4 , the recess  14  formed in the valve casing  12  and the entering portion  15   a  formed in the projection  15  of the first embodiment are omitted in the second embodiment. The radius of the inner circumferential surface of the projection  15  and the radius of the inner circumferential surface of the opening  12   a  of the valve casing  12  are substantially equal. These inner circumferential surfaces are coaxial. The seal ring  17  is arranged between the inner circumferential surface of the projection  15  and the outer circumferential surface of the valve body  16 . 
     Accordingly, in the second embodiment, the advantages substantially equivalent to those of the first embodiment are obtained. Since the second embodiment is configured without the entering portion  15   a , a gap may form easily between the outer shell portion  11   a  and the valve casing  12 , compared to the first embodiment. However, even without the entering portion  15   a , the engagement between the seal ring  17  and the projection  15  of the outer shell portion  11   a  prevents leakage of oil to the exterior. 
     Third Embodiment 
     A third embodiment of the present invention will now be described mainly about the differences from the first embodiment. 
     As illustrated in  FIG. 5 , the third embodiment is configured to included the annular projection  15  formed in the outer shell portion  11   a  and the cylindrical entering portion  15   a  extending from the inner edge of the projection  15 , as in the first embodiment. An inner circumferential surface  24  of the entering portion  15   a  is provided at a position outward from an inner circumferential surface  22  of the valve casing  12  by a distance H in the radial direction of the inner circumferential surfaces  24 ,  22 . In other words, a step  50 , by which the inner circumferential surface  24  of the entering portion  15   a  retreats radially outward, is formed at a boundary portion between the inner circumferential surface  24  of the entering portion  15   a  and the inner circumferential surface  22  of the valve casing  12 . The step  50  provides a non-molded surface  51 , which is not covered by the outer shell portion  11   a , at an end of the valve casing  12  and at the boundary between the inner circumferential surface  22  of the valve casing  12  and the inner circumferential surface  24  of the entering portion  15   a . The aforementioned distance H is set in such a range that the distance H is smaller than the deformation amount of the seal ring  17  and does not influence the sealing performance of the seal ring  17 . 
     An arcuate surface  21  is formed on the inner edge of the opening  12   a  of the valve casing  12 , specifically, in a portion adjacent to the entering portion  15   a  at the inner edge of the opening  12   a . An arcuate surface  23  is formed on the inner edge of the outer opening (the left side as viewed in  FIG. 5 ) of the entering portion  15   a.    
     Accordingly, the third embodiment has the following advantages in addition to the advantages substantially equivalent to those of the first embodiment. 
     (4) The step  50 , by which the inner circumferential surface  24  of the entering portion  15   a  retreats radially outward, is formed in the boundary portion between the entering portion  15   a  and the valve casing  12 . Accordingly, if burr is formed in a portion of the outer shell portion  11   a  adjacent to the valve casing  12  when the outer shell portion  11   a  is molded, the step  50  prevents the burr from projecting toward the inner circumferential surface  22  of the valve casing  12 . As a result, when the valve body  16  is inserted into and incorporated in the valve casing  12 , the burr is prevented from being caught between the valve body  16  and the valve casing  12  or being cut off and falling in the cylinder head cover  11 . 
     (5) The arcuate surface  23  and the arcuate surface  21  are formed in the entering portion  15   a  and the valve casing  12 , respectively. As a result, when the valve body  16  is inserted into and incorporated in the valve casing  12 , damage to the seal ring  17  is suppressed while such incorporation is smoothly accomplished. 
     Fourth Embodiment 
     A fourth embodiment of the present invention will hereafter be explained mainly about the differences from the third embodiment. 
     In the fourth embodiment, as illustrated in  FIG. 6 , the inner circumferential surface  24  of the entering portion  15   a  is inclined in such a manner that the radius of the cross section of the inner circumferential surface  24  becomes greater toward the inner side (the right side as viewed in  FIG. 6 ) in the valve casing  12 . 
     The fourth embodiment has the following advantage in addition to the advantages substantially equivalent to those of the third embodiment. 
     (6) When the seal ring  17  arranged on the valve body  16  and the inner circumferential surface  24  are engaged with each other, force is generated on the inner circumferential surface  24  and presses the seal ring  17  toward the inner side of the entering portion  15   a . This prevents the seal ring  17  from deforming outward (to the left side as viewed in  FIG. 6 ) with respect to the inner circumferential surface  24 . The valve body  16  is thus maintained stably in a mounted state. 
     Fifth Embodiment 
     A fifth embodiment of the present invention will now be described mainly about the differences from the first embodiment. 
     With reference to  FIG. 7 , in the fifth embodiment, a lip seal having a plurality of lip portions  17   a  is employed as the seal ring  17  arranged on the valve body  16 . The lip portions  17   a  are held in contact with the inner circumferential surface of the projection  15 . 
     The fifth embodiment has the following advantages in addition to the advantages substantially equivalent to those of the first embodiment. 
     (7) The seal ring  17  having the multiple lip portions  17   a  enhances the sealing performance between the projection  15  and the valve body  16  without increasing the surface pressure of the seal ring  17  acting on the projection  15 . 
     (8) Even if the surface pressure of the seal ring  17 , or the force acting on the projection  15  of the outer shell portion  11   a  in a radially outward direction, is small, the sealing performance of the seal ring  17  is ensured. This suppresses deformation of the outer shell portion  11   a  in a direction separating from the valve casing  12 . Formation of a gap between the outer shell portion  11   a  and the valve casing  12  is thus prevented. 
     MODIFIED EXAMPLES 
     The illustrated embodiments may be modified as follows. 
     In the configuration with the entering portion  15   a  formed at the inner edge of the projection  15  as in the first embodiment, the lip seal  17  having the multiple lip portions  17   a  may be employed as in the fifth embodiment. 
     In the configuration without the entering portion  15   a  as in the second embodiment, a step may be formed between the inner circumferential surface of the projection  15  and the inner circumferential surface of the valve casing  12  as in the third embodiment. Further, as in the fourth embodiment, arcuate portions may be formed at the inner edge of the valve casing  12  or the inner edge of the projection  15 . 
     The inner circumferential surface  24  of the entering portion  15   a  may be inclined in the direction opposite to that of the third embodiment. In other words, the inner circumferential surface  24  may be inclined in such a manner that the inner circumferential surface  24  retreats further along a direction toward the outer side of the valve casing  12 . 
     An annular groove may be formed in the inner circumferential surface of the projection  15  or the entering portion  15   a , and a seal ring engaged with the outer circumferential surface of the valve body  16  may be fitted in the annular groove. 
     Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.