Patent Publication Number: US-6701884-B2

Title: Cam end cover and gasket assembly

Description:
FIELD OF THE INVENTION 
     The invention relates to motorcycles, and more particularly to motorcycles having overhead cam engines. 
     BACKGROUND OF THE INVENTION 
     The use of overhead cam engines, and more particularly dual overhead cam engines, is well known in the motorcycle industry. Tolerance limits on the casting process used to form the cylinder head of an overhead cam engine make it necessary to ream the cam shaft bearing seats, which are integrally cast into the cylinder head. The reaming ensures the proper alignment and rotation of the camshafts inside the cam case. In order to ream the bearing seats in the relatively confined cylinder head casting, it is necessary to first cast or machine a semi-circular recess in the side wall of the cylinder head and in alignment with the bearing seats. The reaming bit then has an unobstructed path to perform its operation. Aside from facilitating the reaming operation, the semi-circular recess in the cylinder head serves no purpose and must be closed off when the cam cover is placed on the cylinder head. 
     Prior art dual overhead cam engines typically include a resilient sealing gasket at the split line between the cylinder head and the cam cover. The sealing gasket includes integral semi-circular or “half-moon” cam end cover portions that fit in the semi-circular recesses so that the cylinder head and the sealing gasket together form a substantially flat and continuous upper peripheral edge. The cam cover, which has a flat lower peripheral edge corresponding in shape to the upper peripheral edge of the sealing gasket, is then mounted on the cylinder head to enclose the cam shafts and define the upper portion of the cam case. The sealing gasket substantially seals the joint between the cylinder head and the cam cover. 
     SUMMARY OF THE INVENTION 
     Prior art cam case sealing gaskets suffer from various problems. The half-moon cam cover portions are typically molded from the same resilient, elastomeric material as the remainder of the sealing gasket. Because of their resilience, the cam end cover portions often provide a less than adequate seal between the cylinder head and the cam cover. Typically, silicone or other sealing materials must be used on the cam end cover portions, the cam cover, or both prior to mounting the cam cover on the cylinder head to ensure that the semi-circular recesses remain properly sealed. The sealing material may also need to be re-applied each time the cam cover is removed and then re-assembled. The elastomeric half-moon cam cover portions also tend to lack aesthetic appeal. 
     The present invention provides a motorcycle including a frame, an engine crankcase and cylinder assembly coupled to the frame, a cylinder head coupled to the crankcase and cylinder assembly, a cam cover coupled to the cylinder head, and a substantially rigid insert. The cylinder head includes a camshaft support surface and a cylinder head wall. The camshaft support surface defines a camshaft axis and the cylinder head wall partially defines an aperture that is substantially axially aligned with the camshaft axis. The cam cover cooperates with the cylinder head wall to further define the aperture, and the insert is positioned in the aperture. 
     The aperture includes a first boundary that is defined by the cylinder head, and a second boundary that is defined by the cam cover, and the insert includes a first profile corresponding to the first boundary, and a second profile corresponding to the second boundary. In some embodiments, the first and second profiles cooperate to define a semi-circular inner portion of the insert. In other embodiments, the first and second profiles cooperate to define a circular inner portion of the insert. 
     The motorcycle may also include a sealing jacket that surrounds the insert and engages the cylinder head and the cam cover. The sealing jacket may be integrally formed with a resilient sealing member that is positioned between the cylinder head and the cam cover. The insert may also include a substantially circular outer portion that overlies portions of the cylinder head wall and the cam cover. 
     The present invention also provides a method for sealing an interface between a cylinder head and a cam cover. The cylinder head includes a camshaft support surface that defines a camshaft axis, and a cylinder head wall that defines an aperture. The aperture is adjacent the interface and is substantially aligned with the camshaft axis. A substantially rigid insert is provided and a resilient sealing member including a resilient sealing jacket is positioned around the insert. The resilient sealing member is located between the cylinder head and the cam cover such that the resilient sealing jacket and the insert occupy the aperture. 
     The present invention also provides a method of making a sealing gasket and insert assembly for an overhead cam motorcycle engine. The method includes providing a rigid insert and a continuous sealing gasket that includes a sealing jacket defining an opening. The sealing gasket is positioned around the insert such that the insert is positioned in the opening and the sealing jacket substantially surrounds and retains the insert. The gasket may be molded around the insert or alternatively the insert may be pressed into the opening. 
     The present invention also provides a method for replacing a substantially rigid old insert having an inner portion received by an opening in a sealing gasket. The sealing gasket is positioned in an interface between a cylinder head and a cam cover of an overhead cam motorcycle engine, and the old insert has an outer portion overlying portions of the cylinder head and the cam cover. The method includes providing a substantially rigid replacement insert including an inner portion that is positionable within the opening. The old insert is removed from the opening; and the replacement insert is inserted into the opening. A replacement sealing gasket including an opening may also be provided and the replacement sealing gasket may be positioned in the interface in place of the original gasket. 
     The present invention also provides a method for replacing a sealing gasket positioned in an interface between a cylinder head and a cam cover of an overhead cam motorcycle engine. The sealing gasket includes an opening that receives an inner portion of a substantially rigid insert, and the insert has an outer portion overlying portions of the cylinder head and the cam cover. The method includes decoupling the cam cover from the cylinder head and removing the sealing gasket from the interface. The insert is removed from the sealing gasket opening and a replacement sealing gasket including an opening configured to receive the inner portion of the insert is provided. The inner portion of the insert is inserted into the opening of the replacement gasket, the replacement gasket is positioned in the interface, and the cam cover is recoupled to the cylinder head. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of a motorcycle embodying the present invention. 
     FIG. 2 is a side view of an internal combustion engine with a portion cut away. 
     FIG. 3 is an exploded view of a cylinder head and cam cover of the internal combustion engine. 
     FIG. 4 is section view of the cylinder head and cam cover taken along line IV—IV of FIG.  2 . 
     FIG. 5 is a perspective view of a cam end cover of the internal combustion engine. 
     FIG. 6 is a partial perspective view of a cam end seal of the internal combustion engine. 
     FIG. 7 is a top view of a cam cover seal and cam end cover of the internal combustion engine. 
     FIG. 8 is a section view taken along line VIII—VIII of FIG.  7 . 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a motorcycle  10  including a frame  12 , an overhead cam internal combustion engine assembly  14  mounted to the frame  12 , front and rear wheels  16 ,  18  supporting the frame  12 , a steering assembly  20  including handlebars  22  and a fork  24  mounted to the front wheel  16  and pivotal with respect to the frame  12 , and a swing arm  26  (partially hidden) interconnecting the rear wheel  18  to the frame  12 . 
     Referring to FIGS. 2 and 3, the illustrated engine assembly  14  is configured as a V-twin engine and includes an upper crankcase portion  28  having integrally-formed engine cylinders  30 ,  32  that receive engine pistons (not shown). Cylinder heads  34 ,  36  are secured to the engine cylinders  30 ,  32  respectively and house various valve drive components for the internal-combustion engine  14 . In the illustrated embodiment, intake and exhaust camshafts as well as spring-loaded intake and exhaust valves (not shown) are positioned in each cylinder head  34 ,  36  (only the cylinder head  34  being shown in FIG.  3 ). The intake and exhaust camshafts engage cam followers to actuate the valves in a known manner. 
     The cylinder heads  34 ,  36  cooperate with respective cam covers  38 ,  40  to define a cam case or chamber, the cylinder heads  34 ,  36  forming the lower portion of the cam case, and the cam covers  38 ,  40  forming the upper portion of the cam case. The illustrated cam covers  38 ,  40  are constructed of two parts and include base covers  38   a ,  40   a , and cam gear covers  38   b ,  40   b . The base covers  38   a ,  40   a  include a lower peripheral edge  42  that is configured to mate with an upper peripheral edge  44  of a respective cylinder head  34 ,  36  to define a cam case interface. The cam covers  38 ,  40  are fastened to the cylinder heads  34 ,  36  with suitable bolts  46 . In addition, an opening  48  configured to receive a spark plug  50  is also formed in each base cover  38   a ,  40   a . The cam gear covers  38   b ,  40   b  are secured to the base covers  38   a ,  40   a  by the bolts  46 , which also secure the entire cam covers  38 ,  40  to the cylinder heads  34 ,  36 , as well as by additional bolts  51 , which generally extend only into the base covers  38   a ,  40   a . The cam gear covers  38   b ,  40   b  include arcuate chamber portions  52  that receive driving gears for the camshafts. A resilient seal  53  is positioned between the base covers  38   a ,  40   a  and the cam gear covers  38   b ,  40   b . Some embodiments of the invention include cam covers  38 ,  40  that are integrally formed as one piece and include the structural features of both the base covers  38   a ,  40   a  and the cam gear covers  38   b ,  40   b.    
     With respect to the features described further below, the construction and arrangement of the cylinder heads  34 ,  36  and the cam covers  38 ,  40  are substantially the same. As such, the following description will be presented only with respect to one cylinder head  34  and one cam cover  38 . A resilient sealing gasket  54  is positioned between the upper peripheral edge  44  of the cylinder head  34  and the lower peripheral edge  42  of the cam cover  38  to seal the interface. Formed in the cylinder head  34  are two sets of camshaft support surfaces  56 ,  58  that are configured to rotatably support the camshafts. The support surfaces  56 ,  58  are generally semi-circular and define camshaft axes  60 ,  62 . The camshaft support surfaces  56 ,  58  must be precisely formed and are therefore machined into the cylinder head  34  using suitable boring or milling tools. In order to machine the bearing support surfaces  56 ,  58 , apertures  64  are provided in a cylinder head wall  66 . The apertures  64  are each aligned with a respective camshaft axis  60 ,  62  such that the machine tools may be extended through the apertures  64  to machine the camshaft support surfaces  56 ,  58 . As illustrated, the apertures  64  are substantially semi-circular and generally define recesses in, and have arcuate boundaries defined by, the upper peripheral edge  44  of the cylinder head  34 . In addition, the lower peripheral edge  42  of the cam cover  38  defines additional substantially linear boundaries of the apertures  64  when the cam cover  38  is coupled to the cylinder head  34 . 
     Referring to FIGS. 4-6, effective sealing of the cam case is achieved by providing substantially rigid inserts  68  (FIG. 5) positioned within the apertures  64 . The inserts  68  are preferably made of a metal such as aluminum, which has a modulus of elasticity of about 69 GPa (10×10 6  psi), however other metals having different moduli of elasticity are possible. In addition to metals, other substantially rigid fabrication materials (e.g. plastics) having flexural moduli of at least about 1 GPa (150 ksi) are possible as well. In a first embodiment, the inserts  68  include a substantially semi-circular inner portion  70  that is received by the apertures  64 . The inner portion  70  has a first arcuate profile that corresponds to the arcuate aperture boundary provided by the cylinder head  34 , and a second substantially linear profile that corresponds to the linear aperture boundary provided by the cam cover  36 . The inserts  68  also include a substantially circular outer portion  72  that overlies portions of the cylinder head wall  66  and the cam cover  38 . 
     To provide effective sealing around the inserts  68 , the sealing gasket  54  includes sealing jackets  74  (FIG. 6) that are adapted to receive and surround the inner portion  70  of the inserts  68 . The sealing jacket  74  includes a semi-circular opening  76  that receives the inner portion  70  and a resilient sealing strip  78  that is substantially continuous with the remainder of the sealing gasket  54 . A resilient sealing lug  80  extends around the sealing jacket  74  and is substantially continuous with the sealing strip  78 . In some embodiments, the lower peripheral edge  42  of the cam cover  38  includes a groove  82  that is adapted to receive the sealing strip  78 . The sealing jacket  74  also includes a resilient sealing flange or flap  84  that is positioned between the cam cover  38  and the outer portion  72  of the inserts  68  to further seal the interface and reduce and/or damp vibrations of the outer portion  72  during motorcycle operation. 
     To seal the apertures  64 , the inner portions  70  of each insert  68  are pressed into the openings  76  of the sealing jackets  74  and positioned, along with the sealing gasket  54 , between the base cover  38   a  and the cylinder head  34  such that the sealing jackets  74  and the inserts  68  occupy the apertures  64  as illustrated in FIG.  4 . Once the sealing gasket  54  and the inserts  68  are properly positioned on the cylinder head  34 , the cam cover  38  is secured to the cylinder head  34  using the bolts  46 . Thus, the inserts  68  occupy a majority of the apertures  64 , and the sealing lugs  80  seal the apertures  64  along the cylinder head  34  and the sealing strips  78 , and the sealing flaps  84  seal the apertures  64  along the cam cover  38 . For aesthetic purposes, the circular outer portion  72  of the insert  68  includes a raised circumferential collar  86 . However, as discussed below, the outer portion  72  may include other aesthetic features as well. 
     FIGS. 7 and 8 illustrate a second embodiment of the invention wherein the inserts  68 ′ are substantially uniformly circular. The second embodiment is particularly well suited for a motorcycle having the cam cover  38  fabricated as a unitary piece as mentioned above. In this event, the cam cover  38  is provided with semi-circular apertures that are substantially mirror images of the apertures  64  in the cylinder head  34  and define recesses in the lower peripheral edge  42  of the cam cover  38 . The apertures in the cam cover  38  substantially oppose the semi-circular apertures  64  in the cylinder head  34  when the cam cover  38  is mounted to the cylinder head  34 . The opposed apertures in the cam cover  38  and the cylinder head  34  thus cooperate to define a single, substantially circular aperture communicating with the cam case. 
     As illustrated in FIGS. 7 and 8, the sealing gasket  54 ′ may be molded directly around the inserts  68 ′, thereby forming the sealing jacket  74 ′. It should be appreciated that the previously-described sealing gasket  54  may also be molded directly around the inserts  68 . To seal the cam case, the sealing gasket  54 ′ and the inserts  68 ′ are positioned on the upper peripheral edge  44  of the cylinder head  34 , and the one piece cam cover  38  is secured to the cylinder head  34  such that circular inner portions  70 ′ of the inserts  68 ′ occupy the circular apertures, much the same way as the semi-circular inner portions  70  occupy the semi-circular apertures  64 . Similar to the first embodiment, the sealing jacket  74 ′ includes a sealing strip  78 ′ that seals the aperture along the cam cover  38 , and the insert  68 ′ includes a circular outer portion  72 ′ including a raised circumferential collar  86 ′ for aesthetic appeal. 
     With the construction and arrangement of the embodiments described above, the sealing gasket  54  and the inserts  68  provide for the replacement of the inserts  68  and the gasket  54  either alone or in combination. For example, if an insert  68  becomes damaged, or if it is desired to replace the insert  68  with a new insert  68  or an alternate insert having a different aesthetic appearance, the cam cover  38  is removed from the cylinder head  34  and the gasket  54  and the inserts  68  are removed from the interface. The inserts  68  may then be removed from the openings  76  in the sealing jackets  74  and the new/alternate inserts are then inserted into the openings  76 . The gasket  54 , including the new/alternate inserts, is then repositioned in the interface and the cam cover  38  is recoupled to the cylinder head  34 . Alternatively, if the gasket  54  is worn or damaged but the inserts  68  are otherwise intact, a new gasket, similar to the old gasket  54  may be provided. The new gasket, having the same inserts  68  inserted therein, may then be installed in place of the old gasket  54 . Also, inserts  68  having differently shaped or contoured outer portions  72 , or outer portions  72  that display various icons or indicia thereon may be provided and installed to customize or otherwise alter the aesthetic appearance of the motorcycle  10 . With respect to the examples given above, the gasket  54  and insert  68  assembly potentially reduces the cost of replacing a worn, damaged, or otherwise unwanted gasket  54  or insert  68  because the components may be replaced independently of each other. 
     While the forgoing description has been presented with respect to an overhead cam V-twin engine, it should be appreciated that the teachings of the present invention are applicable to substantially any engine type requiring the sealing of apertures that may be positioned along various engine interfaces. 
     Various features of the invention are set forth in the following claims.