Abstract:
A removable timing chain cover is mounted to a fixed frame. The removable cover may contain a harmonic balancer seal retainer for quickly replacing the harmonic balancer seal and a removable cam timing cover for adjusting the cam timing. A timing marker may be positioned for different harmonic balancer sizes as well as being circumferentially adjustable for precise positioning. Further, a timing chain tensioner may be mounted to the frame.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims benefit of U.S. Provisional Application No. 60/322,353 filed Sep. 14, 2001 entitled “Timing Chain Cover” and is hereby specifically incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     The present invention pertains to timing chain covers for V-8 engines and specifically to timing chain covers for high performance applications. 
     b. Description of the Background 
     The conventional timing chain cover Chevrolet small block and big block engines is a stamped sheet metal cover. In high performance applications, such as various forms of racing, there is a need to remove the timing chain cover to perform periodic maintenance or to adjust timing components, such as the cam timing. 
     In some racing applications such as drag racing, the harmonic balancer seal must be replaced after each race. In order to perform this service procedure, the entire conventional timing chain cover must be removed. 
     Racers may wish to adjust the various timing characteristics of the engine. For example, the timing marker is typically fixedly mounted to the timing chain cover. The sheet metal timing cover may not have locating features, such as locating pins, to accurately locate the cover to the block. Thus, when the cover is removed and replaced, the timing marker may not be in the exact location. Some racers may wish to more accurately and repeatably position the timing marker. 
     In another example, the cam timing may be adjusted by adjusting the cam gear at the top of the timing chain. The adjustable cam gear typically requires that the timing chain cover be removed so that the mechanic may have access to the gear. Removal of the timing chain cover, again, typically requires that the harmonic balancer be removed. 
     Further, the standard timing chain covers may not fit when double roller timing chains are used on the engine. Since the double roller timing chain is wider than the standard timing chain, the factory timing chain cover may need to have a spacer in order to accommodate the wider chain. 
     Standard timing chains for Chevrolet V-8 engines may not have an adjustment or slack remover that may be typical of other engines. 
     In some racing applications, an adjustable thrust bearing system may be placed between the timing chain cover and the cam gear to prevent the cam from riding forward during operation. 
     It would therefore be advantageous to provide a timing chain cover that provides repeatable location for the timing marker and allows for the slight adjustment of the timing marker. It would be further advantageous to provide a cover that allows for quick changeover of the harmonic balancer seal and access to the cam gear for adjusting the cam timing. It would be further advantageous to provide a timing chain cover that allows adjustment of the cam timing without removing the harmonic balancer. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages and limitations of the prior art by providing a timing chain cover that comprises a frame that is permanently mounted to the engine block, and a removable cover that is accurately located to the frame. The removable cover may have a harmonic bearing seal retainer that can be accessed without removing the timing chain cover. Further, the timing marker may be precisely adjusted and even relocated for different sized harmonic balancers. The removable cover may contain a second cover that may provide access to the cam gear for adjusting the cam timing. Further, the removable cover may contain provisions for an adjustable thrust bearing to act against the cam gear. 
     The present invention may therefore comprise a removable timing chain cover for an internal combustion engine comprising: a frame fastened to the block of the engine; a removable cover fastened to the frame, the cover having a locating feature adapted to position the removable cover onto the frame, the cover having an o-ring seal about the periphery of the cover between the cover and the frame; a harmonic balancer seal retainer fastened to the removable cover adapted to retain a seal for the crankshaft of the engine, the harmonic balancer seal having an o-ring seal about the periphery of the seal retainer between the seal retainer and the removable cover; and a timing marker mounted on the removable cover and adapted to be mounted in at least two positions, the timing marker further adapted to be adjusted in position substantially about the axis defined by the crankshaft of the engine. 
     The present invention may further comprise a removable timing chain cover comprising: a frame fastened to the block of the engine; a oil pan seal holder fastened to the frame and adapted to hold a gasket between the oil pan seal holder and the oil pan of the engine; a removable cover fastened to the frame, the cover having an o-ring seal about the periphery of the cover between the cover and the frame; a harmonic balancer seal retainer fastened to the removable cover adapted to retain a seal for the crankshaft of the engine, the harmonic balancer seal having an o-ring seal about the periphery of the seal retainer between the seal retainer and the removable cover; a timing marker mounted on the removable cover and adapted to be mounted in at least two positions, the timing marker further adapted to be adjusted in position substantially about the axis defined by the crankshaft of the engine; a cam timing cover fastened to the removable cover and adapted to be removed while the harmonic balancer is mounted on the crankshaft of the engine, the cam timing cover having an o-ring seal substantially about the periphery of the cam timing cover between the cam timing cover and the removable cover; and a tensioning system mounted to the frame comprising a spring loaded tensioner and a fixed tensioner. 
     The advantages of the present invention are that access to various adjustable or replaceable components underneath or attached to a timing chain cover may be serviced or replaced quickly. Further, the o-ring seals between the components that are disassembled can be removed and replaced repeatedly without damage. The harmonic balancer seal may be replaced without having to remove the timing chain cover. In some cases, the cam timing can be adjusted without having to remove the harmonic balancer and complete timing chain cover. The timing marker may be adjusted both for different sized harmonic balancers as well as circumferentially to precisely adjust the timing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, 
     FIG. 1 is an illustration of an exploded view of an embodiment of a removable timing cover system. 
     FIG. 2 is an illustration of an exploded view of an embodiment of a removable timing chain cover from the internal perspective. 
     FIG. 3 is an illustration of an embodiment of a removable timing chain cover. 
     FIG. 4 is an illustration of an embodiment of a removable timing chain cover showing access to the cam gear. 
     FIG. 5 is an illustration of an embodiment of a removable timing chain cover showing an embodiment of a chain tensioning apparatus. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates an embodiment  100  of a removable timing cover system. A frame  102  is mounted to the engine block of an engine. A removable cover  104  mounts to the frame  102  with fasteners and seals to the frame  102  with an o-ring seal. The harmonic balancer seal retainer  106  bolts to the removable cover  104  with an o-ring seal. The timing marker  108  fastens to the removable cover  104 . The cam timing cover  110  is fastened to the removable cover  104  and provides access to the cam gear of the engine. An optional fixed timing chain tensioner  112  and movable timing chain tensioner  114  mounts to the frame  102 . An oil pan seal retainer  116  holds a gasket to seal to the oil pan of the engine. 
     The embodiment  100  is designed so that the frame  102  and optional oil pan seal  116  may be mounted to an engine block. The removable cover  104  may be removed without having to remove or loosen the oil pan of the engine, as would have been the case with a stock sheet metal timing chain cover. The removable cover  104  has an o-ring seal between the cover  104  and the frame  102  to prevent any oil leakage. Such a seal is much more maintainable than a conventional paper gasket, as the o-ring seal can be easily disassembled and reassembled many times without any wear or replacement. 
     The frame  102  and removable cover  104  may engage with interlocking features. Such features may be machined features such as grooves or lips about the periphery or may comprise locating dowel pins or fasteners such as flathead screws or shoulder screws. 
     The harmonic balancer seal retainer  106  is likewise removably mounted with an o-ring seal between the seal retainer  106  and the removable cover  104 . The harmonic balancer seal retainer  106  further has a plurality of notches  118  for quickly removing the seal. 
     The timing marker  108  may be mounted on mounting pads  122 ,  124 , or  126 , depending on the size of the particular harmonic balancer. Each mounting pad contains a flat portion  128  and two screw holes  130  for locating and fastening the timing marker  108 . The timing marker is attached with optional slotted holes  131 . The holes  131  allow the timing marker to be adjusted when the engine is built, providing a more accurate location for the timing marks than the prior art of a fixed locator. 
     The cam timing cover  110  is removably mounted to the removable cover  104  and is sealed with an o-ring. The cam timing cover  110  gives access to the cam timing gear of the engine for adjustment purposes without having to remove the harmonic balancer. 
     The fixed chain tensioner  112  and movable chain tensioner  114  provide a mechanism for keeping the timing chain under constant tension during operation. The fixed timing chain tensioner may be manufactured from a wear resistant material such as ultra high molecular weight polyethylene, acetal, or other plastics. In other embodiments, a roller may be used to ride against the timing chain for both the fixed chain tensioner and the movable chain tensioner. 
     The movable chain tensioner  114  operates by having a spring mounted to push the movable chain tensioner  114  inward, as it rotates about the axis formed by the fastener hole  132 . Embodiments may include a compression spring mounted between the frame  102  and the movable tensioner  114 . Other embodiments may use leaf springs, torsion springs, built in springs, or other spring designs. In some cases, the spring may be removable to allow the timing chain to be assembled to the engine prior to applying the spring force to the movable tensioner  114 . 
     The oil pan seal  116  may be used in some applications to effect a seal between the oil pan and the frame  102 . This allows the engine oil pan to remain stationary when the removable cover  104  is removed for servicing and adjustment to the various components of the timing chain. 
     FIG. 2 illustrates the removable timing chain cover  200  from the internal perspective. The frame  202  mounts to the engine block. The removable cover  204  mounts to the frame  202  with an o-ring seal. The harmonic balancer seal retainer  206  mounts to the removable cover  204  as does the timing marker  208  and cam timing cover  210 . The fixed mounted chain tensioner  212  and movable chain tensioner  214  as well as the oil pan seal  216  mount to the frame  202 . 
     The cam timing cover  210  may be optional. In some cases, access to the cam gear is not required to the extent that a removable cover is necessary. 
     FIG. 3 illustrates a removable timing chain cover  300 . The frame  302  is mounted to the engine block  303 . The removable cover  304  is mounted to the frame  302 . The harmonic balancer seal retainer  306 , timing marker  308 , and cam timing cover  310  are mounted to the removable cover  304 . 
     The cam timing cover  310  has a hole  312  for mounting a cam thrust bearing (not shown). The cam thrust bearing is used to prevent the cam of the engine from moving toward the front of the engine during high speeds. The cam thrust bearing may be mounted on an adjustable support so that a specific preload may be applied to the camshaft. 
     FIG. 4 illustrates an embodiment  400  of the removable timing chain cover. The frame  402  is mounted to the engine block  403 . The removable cover  404  is mounted to the frame. The cam timing cover is removed to reveal the timing chain  406  and the cam gear  408 . The cam gear  408  is a variety wherein adjustment screws  410  may be loosened and the position of the gear teeth with respect to the cam position may be adjusted with a special cam wrench. The cam gear  408  may be adjusted from the opening provided by removing the cam timing cover and without having to remove the harmonic balancer (not shown) or the removable cover  404 . 
     The crankshaft  412  is shown. The harmonic balancer for the engine mounts on the end of the crankshaft  412  and is not shown for clarity. 
     FIG. 5 illustrates an embodiment  500  of the removable timing chain cover. The frame  502  is mounted on the engine block  503 . The crankshaft  504  is connected to the cam gear  506  with the timing chain  508 . The fixed chain tensioner  510  and the movable chain tensioner  512  apply force to the timing chain  508  to remove any slack from the chain  508 . 
     The movable timing chain tensioner  512  has a compression spring mounted between the movable timing chain tensioner  512  and the frame  502 . The tensioner  512  is permitted to rotate about the fastener  514  to apply tension to the chain  508 . Other embodiments of a timing chain tensioner may be envisioned by those skilled in the art while maintaining within the scope and intent of the present invention. 
     Those skilled in the art will appreciate that the timing chain cover is applicable to any timing mechanism. For example, embodiments may be fabricated for timing drive mechanisms comprising a belt drive, gear drive, or any other timing drive mechanism. For the purposes of the above discussion, the term timing chain was used for convenience. However, the cover system is applicable to all forms of timing drive mechanisms. 
     The embodiments shown are applicable to Chevrolet V-8 engines, including small block and big block engines. Other applications of the present invention may include other V-8 engines, as well as for any other engine wherein a removable timing chain cover may be used to provide access to the timing chain components in a quick fashion. 
     The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.