Abstract:
An internal combustion engine with an overhead valve configuration includes multiple integral bosses, an exhaust valve rocker stud including an upper portion and a lower portion, an intake valve rocker stud including an upper portion and a lower portion, a head plate supported by the integral bosses such that an air cooling passage is formed between the head plate and the cylinder head, where the head plate is fastened to the cylinder head by the lower portions of the exhaust valve rocker stud and the intake valve rocker stud, and a cover secured to the head plate such that the cover and the head plate enclose the upper portions of the exhaust valve rocker stud and the intake valve rocker stud.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This is a continuation of application Ser. No. 12/508,387, filed Jul. 23, 2009, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The present invention relates generally to the field of small combustion engines with overhead valve or overhead cam configurations. More specifically the present invention relates to a system for covering rocker arms, valve stems, overhead cams, or other engine components extending from a cylinder head. 
         [0003]    Overhead valve (OHV) engines include various components to open and close the intake and exhaust valves. Typically, a camshaft includes cams that push tappets at timed intervals. The tappets are coupled to pushrods, and the pushrods engage rocker arms. The rocker arms pivot upon spherical surfaces of a rocker balls, which are positioned on rocker studs and transfer the upward force of the pushrods into downward force on valve stems, and visa versa. Other rocker arms may pivot upon cylindrical pivots, such as pins, that are secured to a cylinder head without rocker studs. As the rocker arms push down or lift up upon the valve stems, the corresponding intake and exhaust valves open and close in the combustion chamber. Often valve springs are positioned around the valve stems to provide a lifting force to return the rocker arms and valves to the closed position when the cam is no longer engaged with the tappet. 
         [0004]    The rocker arms and rocker studs are typically fastened to the top of a cylinder head, with the pushrods and valve stems extending through apertures in the cylinder head. The components of the OHV configuration extending from the top of the cylinder head are typically enclosed by a housing. A head plate forms a bottom portion of the housing. The head plate may be integrally formed with the cylinder head, or may be separately attached to bosses extending from the cylinder head. A rocker cover forms a top portion of the housing, attaching to the head plate and limiting access to the rocker arms and other components of the OHV configuration attached to the top of the cylinder head. 
       SUMMARY 
       [0005]    One embodiment of the invention relates to an internal combustion engine with an overhead valve configuration. The internal combustion engine includes a cylinder head including multiple integral bosses, an exhaust valve rocker stud including an upper portion and a lower portion, an intake valve rocker stud including an upper portion and a lower portion, a head plate including an exhaust rocker stud aperture and an intake rocker stud aperture where the head plate is supported by the integral bosses such that multiple air cooling passages are formed between the head plate and the cylinder head and where the lower portion of the exhaust valve rocker stud extends through the exhaust rocker stud aperture and the lower portion of intake valve rocker stud extends through the intake rocker stud aperture to fasten the head plate to the cylinder head, and a cover secured to the head plate such that the cover and the head plate enclose the upper portions of the exhaust valve rocker stud and the intake valve rocker stud. 
         [0006]    Another embodiment of the invention relates to an internal combustion engine with an overhead valve configuration. The internal combustion engine includes a cylinder head including multiple integral bosses, an exhaust valve rocker stud including an upper portion and a lower portion, an intake valve rocker stud including an upper portion and a lower portion, a head plate supported by the integral bosses such that an air cooling passage is formed between the head plate and the cylinder head, where the head plate is fastened to the cylinder head by the lower portions of the exhaust valve rocker stud and the intake valve rocker stud, and a cover secured to the head plate such that the cover and the head plate enclose the upper portions of the exhaust valve rocker stud and the intake valve rocker stud. 
         [0007]    Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0008]    The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements, in which: 
           [0009]      FIG. 1  is a perspective view of an internal combustion engine according to an exemplary embodiment. 
           [0010]      FIG. 2  is side view of a cylinder head and a crankcase according to an exemplary embodiment. 
           [0011]      FIG. 3  is a perspective view of a cylinder head according to an exemplary embodiment. 
           [0012]      FIG. 4  is a perspective view of the cylinder head with rocker arms according to an exemplary embodiment. 
           [0013]      FIG. 5A  is a side view of a cylinder head and rocker cover according to an exemplary embodiment. 
           [0014]      FIG. 5B  is a sectional view taken generally along line  5 B- 5 B of  FIG. 2 . 
           [0015]      FIG. 6A  is a sectional view of a fastener according to an exemplary embodiment. 
           [0016]      FIG. 6B  is a sectional view of a fastener according to another exemplary embodiment. 
           [0017]      FIG. 6C  is a sectional view of a fastener according to yet another exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting. 
         [0019]    Referring to  FIG. 1 , an internal combustion engine  110  includes a blower housing  112  covering a top of the engine  110 , with an air intake  114  and a fuel tank  116  mounted to a side of the engine  110 . A recoil starter  118  is attached to the top of the blower housing  112 , and a muffler  120  is attached to one side of the engine  110 . The engine  110  may include an automatic starter. The engine  110  may be used to drive power equipment, such as a rotary lawn mower blade, a pressure washer pump, a home generator, or other equipment. 
         [0020]    The engine  110  further includes a crankcase  122  and a corresponding sump  124  fastened to the underside of the crankcase  122 . The crankcase  122  supports internal components of the engine  110 , such as a piston, a connecting rod, a camshaft, and other components. The sump  124  forms a base of the crankcase  122 , and holds a pool of oil lubricant within the crankcase  122 . A vertical crankshaft  126  extends from the crankcase  122 , through the sump  124 . The crankcase  122  and sump  124  may be integrally cast. 
         [0021]      FIG. 2  shows a side view of the engine  110 , with various engine components not shown to better display the engine structure. For example, the blower housing  112  is omitted to better show components on the top of the engine  110 , including a top portion  128  of the crankshaft  126 . The top portion  128  powers a flywheel and blower fan, and may be engaged by the recoil starter  118 . A cylinder head  130  is attached to a cylinder block  250  (see  FIG. 5A ) and a rocker cover  132  is coupled to the cylinder head  130 . The cylinder head  130  includes fins  134  for heat dissipation. Also shown in  FIG. 2 , the cylinder head  130  includes an aperture  136  through which a spark plug may be inserted to ignite fuel in the combustion chamber. The cylinder head  130  is fastened to the cylinder block  250  via bolts  140 , or other fasteners. The rocker cover  132  is fastened to a head plate  138 , as shown in  FIG. 3 . 
         [0022]      FIG. 3  shows a perspective view of the cylinder head  130 , including the fins  134 , the spark plug aperture  136 , and bolt holes  142  through which extend the bolts  140  that fasten the cylinder head  130  to the cylinder block  250 . The head plate  138  is mounted to the top of the cylinder head  130 . Also shown are the rocker studs  160 ,  162  and valve stems  164 ,  166  corresponding to rocker arms  168 ,  170  (see  FIG. 4 ). 
         [0023]    Referring to  FIG. 3 , the head plate  138  is coupled to the top of the cylinder head  130 . The rocker studs  160 ,  162  include threaded ends  172  (see  FIG. 5B ) that are inserted through apertures  148 ,  150  in the head plate  138 . Adjacent to the threaded ends and an intermediate body section, the rocker studs  160 ,  162  include a flange that doubles as a bolt head  174 . The rocker studs  160 ,  162  are inserted through the apertures  148 ,  150  in the head plate  138 , and into bosses  176  (see also  FIG. 5B ) extending from the cylinder head  130 . According to an exemplary embodiment, the rocker studs  160 ,  162  are the only threaded fasteners used to couple the head plate  138  to the cylinder head  130 . Valve stems  164 ,  166  are inserted through valve guides that pass through the head plate  138  and into the cylinder head  130 , and thus provide support to the head plate  138  in directions transverse to the longitudinal axes of the valve stems  164 ,  166 . Further support may be provided by a gasket  228  positioned between the head plate  138  and the cylinder head  130 . For example, in some embodiments a liquid gasket (that solidifies or cures after application) is used, which also functions as an adhesive. In other embodiments, the head plate is integrally cast with the cylinder head. In still other embodiments, the head plate is welded to the cylinder head. 
         [0024]    Referring to  FIG. 3 , the head plate  138  includes apertures  144 ,  146  for pushrods  156 ,  158  (see  FIG. 4 ); apertures  148 ,  150  for rocker studs  160 ,  162 ; and apertures  152 ,  154  for exhaust and intake valve stems  164 ,  166 , respectively. The apertures  144 ,  148 ,  152  are aligned, and the apertures  146 ,  150 ,  154  are aligned. Alignment allows the apertures  144 ,  148 ,  152  and  146 ,  150 ,  154  to support straight rocker arms  168 ,  170  (see  FIG. 4 ). The apertures  144 ,  148 ,  152  are spaced further apart than the apertures  146 ,  150 ,  154 , allowing the apertures  144 ,  148 ,  152  to support a longer rocker arm  168  than the apertures  146 ,  150 ,  154 . For example, in some embodiments, the rocker arm  168  corresponding to the exhaust valve stem  164  is longer than the rocker arm  170  corresponding to the intake valve stem  166 . In other embodiments, a head plate may include additional apertures configured to support other numbers of valves stems, rocker studs, and pushrods. 
         [0025]    Still referring to  FIG. 3 , the bottom surface  204  of the head plate  138  includes a number of protrusions  180 . The protrusions form wells  182  to support valve springs  184  (see  FIG. 4 ). Additionally, the protrusions  180  strengthen portions of the head plate  138 , preventing warping and deflection resulting from heat transferred from the cylinder head  130 . 
         [0026]      FIG. 4  shows the cylinder head  130 , with rocker arms  168 ,  170  attached. Also shown in  FIG. 4  are mounting bosses  190  for attaching a muffler to the cylinder head  130 . The muffler may be attached over an exhaust port  192 , through which exhaust gases from the combustion chamber exit the cylinder head  130 . 
         [0027]    The rocker arms  168 ,  170  move at different times to transfer force from the pushrods  156 ,  158 , opening and closing an exhaust valve  186  and an intake valve  188 , respectively. The head plate  138  has an asymmetrical shape corresponding to the arrangement of the rocker arms  168 ,  170 . However, in other embodiments the head plate  138  may be formed in other shapes and configurations. 
         [0028]      FIG. 5A  shows the rocker cover  132  mounted over the head plate  138 , which is attached to the cylinder head  130 . The rocker cover  132  includes a dome-shaped top surface  194  with sides  196  extending from the top surface. In other embodiments, the top surface is flat or otherwise shaped. The sides  196  are rounded into the top surface  194 , reducing sharp edges with corresponding stress and heat concentrations. Proximate to the end of the sides  196 , the rocker cover includes a flange  198  with an overhang  200  extending below the flange  198 . In some embodiments, the rocker cover  132  is formed from steel sheet. However, in other embodiments the rocker cover  132  is formed from other materials, such as aluminum, molded plastic with composite fiber, or other materials. Sides  202  of the head plate  138  extend from the bottom surface  204  of the head plate  138 . 
         [0029]    Referring to  FIG. 5B , the mounting configuration of the rocker cover  132  and the head plate  138  is shown. The sides  202  of the head plate  138  terminate in a curl, shown as a rounded curl  206 . The flange  198  of the rocker cover  132  rests on the top of the curl  206 , and the overhang  200  extends over the side of the curl  206 , and the overhang  200  attaches to the curl  206 . In one embodiment, a solid or liquid gasket  230  is inserted between the curl  206  and the flange  198 . One exemplary gasket material includes a room temperature vulcanizing silicone rubber. In other embodiments gaskets are formed from other commercially available gasket materials. 
         [0030]      FIGS. 6A-6C  show various arrangements in which the overhang  200  may fasten to the curl  206 . In  FIG. 6A , the overhang  200 A includes a protrusion  208  (see also  FIG. 5A ) that forms a catch. The protrusion  208  extends inside the side  196  and forms a ledge  210  or hook, which catches the end  212  of the curl  206 . The combination of the protrusion  208  and the curl  206  allows the rocker cover  132  to “snap” onto the head plate  138 . In  FIG. 6B , a curl  214  extends both inside and outside of the sides  202 B of the head plate  138 . A fastener  216  integral with the overhang  200 B extends over the curl  214 , such that hooks  218  fasten to the underside  220  of the curl  214 . The hooks  218  also form a catch. In  FIG. 6C , a curl  222  engages a ledge  224  of the overhang  200 C. The curl  222  has a triangular cross section. The ledge  224  further includes a hook  226  that extends through an aperture  232  in the sides  202 C of the head plate  138 . The ledge  224  and hook  226  form yet another catch. The fasteners of  FIGS. 6A-6C  can be detached by lifting the catch away from the end of the head plate  138 , and lifting the rocker cover  132  away. 
         [0031]    In some embodiments, multiple fasteners are used to couple the rocker cover  132  to the head plate  138 . For example, in at least one embodiment overhang  200  of the rocker cover  132  includes at least two fasteners, each having a catch. The fasteners are positioned on opposing sides of the overhang  200 . In another embodiment, the overhang  200  includes at least two fasteners. In some embodiments, the hook or catch is integral with the head plate  138  and is received by the overhang  200 . The fasteners, as shown in  FIGS. 6A-6C , allow for the coupling of the rocker cover  132  and the head plate  138  without the use of additional threaded fasteners (e.g., screws, bolts, etc.). While  FIGS. 6A-6C  disclose various forms of fasteners having a catch, other fasteners integral with the rocker cover and the head plate are used with other embodiments. For example, some embodiments include latches, pins, crimping, adhesives, spot welding, and other fasteners. 
         [0032]    A method for assembling a rocker cover system includes several steps. A step includes providing the rocker cover  132 , the head plate  138 , the cylinder head  130 , and the gasket  230 . Another step includes fastening the head plate  138  to the cylinder head  130 . A set includes coupling the gasket  230 , such as a liquid gasket, to the curl  206  or to the flange  198 . Yet another step includes aligning the rocker cover  132  over the head plate  138 , such that the flange  198  and the overhang  200  are positioned over the curl  206 . Another step includes pressing the rocker cover  132  toward the head plate  138  to “snap” the catch of the protrusion  208  into place at an end of the curl  206 . No tools (e.g., screwdriver, pliers, wrench, etc.) are required. 
         [0033]    The construction and arrangements of the system for covering rocker arms, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. For example the engine is shown with a vertical crankshaft, but it may be configured with a horizontal crankshaft. Also, the engine may include multiple cylinders. In some embodiments, the cover system is used to cover an overhead cam. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. In some embodiments, the system can be used to cover other engine components, such as a filter of an air intake. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.