Abstract:
An adjustable camshaft sprocket assembly for attachment to a camshaft. A camshaft sprocket is removably securable to a camshaft sprocket hub and moveable, independent of the camshaft sprocket hub when the camshaft sprocket assembly is mounted on the camshaft. An adjustment tool is used to adjust the camshaft sprocket comprising at least two extensions. The first extension is of a size to fit within one a corresponding opening in the camshaft hub. The second extension is of a size to pass though a different corresponding opening in the camshaft hub and fit within a corresponding opening in the camshaft sprocket. A handle extension is used for turning the adjustment tool about the second extension, which serves as a pivot.

Description:
This application is a continuation of U.S. patent application Ser. No. 09/476,731, filed Dec. 30, 1999 now abandoned. 
    
    
     FIELD OF INVENTION 
     The present invention relates to internal combustion engine valve timing. More particularly, the present invention relates to adjustable cam sprockets for adjusting engine valve timing of an automotive internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     Most vehicle engines are internal combustion engines that use intake valves to control the entry of combustible gases (i.e. air/gas mixture) into a combustion chamber for ignition by a spark. Following combustion, exhaust valves control the escape of exhaust gases resulting from the combustion. Both the intake valves and the exhaust valves are controlled by cams lobes located on a camshaft. Pistons located in the combustion chamber are driven by the combustion of the combustible gases to cause the rotation of a crankshaft. The crankshaft is used to change the up-and-down motion of the piston into a turning or rotating force. This force is then used to drive the wheels of the vehicle. 
     The timing of the opening and closing of the intake and exhaust valves relative to the position of the pistons is very important for the operation and performance characteristics of the engine. Optimum performance is achieved when the intake and exhaust valves are operated at a precise position relative to the position of the pistons. A sprocket and chain system is generally used to control the timing of the camshaft rotation (intake and exhaust valve opening) to the crankshaft rotation (piston position). A combination of camshaft sprocket, timing chain and crankshaft sprocket is commonly referred to as a timing set and controls this timing. Adjustment of the rotation of the camshaft relative to the crankshaft of even 1° or 2° can effect engine performance. For this reason, the timing for an engine is usually a design characteristic of the engine that is determined and fixed by the engine manufacturer. The timing is usually fixed by a positioning “key” and keyways on both the crank shaft/crank sprocket and the camshaft/cam sprocket or the camshaft/cam sprocket by means of a dowel pin and mating dowel holes. 
     Determining optimum performance, however, depends upon the particular task for which the engine is being used. The preset engine timing from the manufacturer may be sufficient for a wide range of engine use, but may not be optimum for a particular purpose, such as high performance (long or short racing), off-roading or towing. Advancing the camshaft (by adjusting the camshaft position relative to the crankshaft) increases the lower RPM power. Retarding the camshaft improves the higher RPM power. 
     Replacement timing sets have been available to replace the original equipment timing set of a vehicle to allow adjustment of the engine timing from the preset manufacturers timing specification. Some of these “after market” timing sets have a crankshaft sprocket with multiple keyways in its bore. A problem with such a system is that the use is limited to the number of keyways and the fixed timing specification of each keyway. In addition, such timing adjustment systems require that the timing set (either partially or completely) be removed to make the adjustment, adding time and labor to the task. Other adjustment systems provide for adjustment of the camsprocket relative to the camshaft. In many such systems, however, it is also necessary to remove the timing set (either partially or completely) to make the adjustment. 
     SUMMARY OF THE INVENTION 
     The present invention provides for an adjustable camshaft sprocket assembly for attachment to a camshaft. A camshaft sprocket is removably securable to a camshaft sprocket hub and moveable, independent of the camshaft sprocket hub when the camshaft sprocket assembly is mounted on the camshaft. 
     An adjustment tool is used to adjust the camshaft sprocket. The camshaft tool is comprised of at least two extensions; the first extension is of a size to fit within one a corresponding opening in the camshaft sprocket hub. The second extension is of a size to pass though a different corresponding opening in the camshaft hub and fit within a corresponding opening in the camshaft sprocket. A handle extension is used for turning the adjustment tool about the first extension, which serves as a pivot. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention, as well as other features and advantages thereof, will now be described by way of non-limiting example with reference to the following figures in which: 
     FIG. 1 is an exploded view of an exemplary embodiment of the present invention; 
     FIG. 2 is a side view of a camshaft sprocket timing adjustment tool in accordance with the present invention; 
     FIG. 3 is front view of the camshaft sprocket timing adjustment tool shown in FIG. 2; 
     FIG. 4 is a top view of the camshaft sprocket timing adjustment tool shown in FIG. 2; 
     FIG. 5 is a bottom view of the camshaft sprocket timing adjustment tool shown in FIG. 2; 
     FIG. 6 is a top view of the camshaft sprocket hub shown in FIG. 1; 
     FIG. 7 is a side view of the camshaft sprocket hub shown in FIG. 1; 
     FIG. 8 is a top view of the camshaft sprocket shown in FIG. 1; 
     FIG. 9 is a side view of the camshaft sprocket shown in FIG. 1; 
     FIG. 10 is a top view of the camshaft sprocket hub fitted with the camshaft sprocket shown in FIG. 1; 
     FIG. 11 is a side view of the camshaft sprocket hub fitted with the camshaft sprocket shown in FIG. 1; 
     FIG. 12 is a top view of a preferred embodiment of the camshaft sprocket shown in FIG. 1; and 
     FIG. 13 is a top view of a preferred embodiment of the camshaft sprocket hub shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     There is shown in FIG. 1 an exploded view of an exemplary embodiment of an adjustable camshaft sprocket assembly  10  in accordance with the present invention. A camshaft sprocket hub  14  nests with camshaft sprocket  12 . Securing bolts  18  secure camshaft sprocket hub  14  to camshaft sprocket  12 . Securing bolts (fasteners)  18  are inserted into washers  16  before securing camshaft sprocket hub  14  to camshaft sprocket  12 . Timing adjustment tool  20 , while not a part of camshaft sprocket assembly  10 , is used to make timing adjustments to camshaft sprocket assembly  10 . 
     Timing adjustment tool  20  is further illustrated in FIGS. 2-5. A short protrusion or dowel  24  extends from bottom surface  25  of body portion  22  of timing adjustment tool  20 . A long protrusion or dowel  26  also extends from bottom surface  25  of body  22 . Long dowel  26  extends further from bottom surface  25  than does short dowel  24 . Short dowel  24  and long dowel  26  are shown in longitudinal alignment along bottom surface  25  of body  22 . In an exemplary embodiment, both short dowel  24  and long dowel  26  are made from a hardened steel and extend into body  22 , as shown in phantom in FIG.  1 . Other suitable metals and attachment means will be understood by those skilled in the art. A handle extension  29  extends from top surface  27  of body  22 . An exemplary embodiment of handle extension  29  is shown in a substantially square configuration for use with a socket wrench, box end wrench, or similar tool. In this embodiment, handle extension  29  is 0.375″ square. This allows timing adjustment tool  20  to be used as a socket (socket head) when adjusting camshaft sprocket assembly  10 . A socket or similar tool allows leverage and torque to be applied when adjusting the advance or retard of camshaft sprocket assembly  10 . A hex or other configuration may be used as well, depending upon the tool used. Instead of extension  29 , a slot may be formed in body  22 , for rotation with a levered screwdriver. In an alternative embodiment, not shown, timing adjustment tool  20  is attached to lever arm, in a similar orientation to that when attached to a socket wrench for the configuration shown. In such an embodiment, a separate socket wrench would not be necessary. In such an embodiment, the lever arm need not be ratcheting in its attachment to timing adjustment tool  20 . In an additional embodiment body  22 , short dowel  24 , long dowel  26  and handle extension  29  are made from a single piece of hardened steel. 
     A top view of camshaft sprocket hub  14  is shown in FIG. 6 with a corresponding side view shown in FIG.  7 . Camshaft sprocket hub  14  is separate from and nests with camshaft sprocket  12 . A plurality of elongated, oval shaped openings  28  are evenly positioned toward the outer perimeter of camshaft sprocket hub  14 . In an exemplary embodiment, each securing bolt opening  28  is spaced approximately 60° on center from each of its adjacent securing bolt opening  28 . Each opening  28  is of a sufficient diameter to receive and allow the shaft portion of a securing bolt  18  to pass through camshaft sprocket hub  14 . A pair of long dowel openings  30  are positioned 180° apart from each other and approximately 30° apart from the adjacent securing bolt receiving openings  28 . Each long dowel opening  30  is of a sufficient diameter to receive and allow long dowel  26  of camshaft timing adjustment tool  20  to pass through camshaft sprocket hub  14 . Positioned interior to each long dowel opening  30  is a short dowel recess  32 . At least one long dowel opening  30  and short dowel recess  32  pair is needed for the present invention. More than one pair of long dowel opening  30  and short dowel recess  32  allows timing adjustments to be made from alternate locations using timing adjustment tool  20 . Multiple adjustment locations for a user to select from, makes timing adjustments easier and more convenient for the user. Short dowel recess  32  is of a sufficient size to receive short dowel  24  of camshaft adjustment tool  20 . Short dowel recess  32  is of a sufficient depth and diameter to securely receive short dowel  24  when inserted, but has a bottom surface (not shown), so as not to allow short dowel  24  to pass through camshaft sprocket hub  14 . 
     Each long dowel opening  30  and camshaft securing bolt opening  36  has a lower edge  40  and an upper edge  41 . Lower edge  40  and upper edge  41  are curved to approximate the curve of the camshaft hub  14 . Each edge is an arcuate curved surface. 
     A rim  33  is positioned interior to short dowel recesses  32 . Rim  33  provides alignment when nesting camshaft sprocket hub  14  with camshaft sprocket  12 . Interior to rim  33  is dowel hole  34 . Dowel hole  34  is of a sufficient depth and diameter to receive a dowel (not shown) attached to a camshaft (not shown). Three camshaft sprocket securing bolt openings  36  are positioned approximately equidistant from each other. Dowel hole  34  is positioned approximately 60° from each of the adjacent camshaft sprocket securing bolt openings  36 . The number, position and orientation of dowel hole  34  and camshaft sprocket securing bolt openings  36  is determined by the corresponding structure of the camshaft to which camshaft sprocket assembly  10  is being attached. 
     Four optional weight reduction openings  38  are used in an exemplary embodiment. 
     In an exemplary embodiment, camshaft sprocket assembly  10  is used for a Chevrolet® small block engine. For such an embodiment, camshaft sprocket  12  and camshaft sprocket hub  14  are each machined from a blank of SAE 1144 billet steel; camshaft sprocket securing bolt openings  36  have an approximately 0.344″ diameter; dowel hole  34  has an approximately 0.2505″ diameter; weight reduction openings  38  have an approximately 0.625″ diameter; long dowel openings  30  and camshaft sprocket assembly securing bolt openings  28  have a length that allows a total of 12° (6° advance from center and 6° retard from center) range of motion; short dowel  24  extends 0.125″ from bottom surface  25  with a diameter of 0.1875″; long dowel  26  extends 0.375″ from bottom surface  25  with a diameter of 0.1875″; and the following are approximate measurements for some of the dimensions shown in FIGS. 6 and 7. 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 A = 2.623-2.625″ 
                 α = 30° 
               
               
                   
                 B = 1.868″ 
                 β = 30° 
               
               
                   
                 C = .035″ 
                 χ = 45° 
               
               
                   
                 D = .355″ 
                 δ = 45° 
               
               
                   
                 E = .230″ 
               
               
                   
                 F = .119″ 
               
               
                   
                 G = 4.373-4.375″ 
               
               
                   
                   
               
             
          
         
       
     
     A top view and side view of an exemplary camshaft sprocket  12  are shown in FIGS. 8 and 9, respectively. Camshaft sprocket  12  has plurality of teeth  42  spaced around its perimeter. The number, size and dimensions of teeth  42  are dependent upon the particular engine for which camshaft sprocket assembly  10  is being used. A center recess (or hole)  52  is for receiving and nesting with rim  33  of camshaft sprocket hub  14 . 
     A pair of long dowel recesses (or holes)  44  are positioned 180° apart from each other and approximately 30° apart from the adjacent threaded securing bolt openings  46 . Each long dowel recess  44  is of a sufficient diameter to receive long dowel  26  of camshaft timing adjustment tool  20  when inserted. In an exemplary embodiment, each threaded securing bolt opening  46  is spaced approximately 60° on center from each of its adjacent threaded securing bolt opening  46 . Each threaded securing bolt opening  46  is of a sufficient depth and diameter to receive and secure a securing bolt  18  when inserted and tightened to the appropriate torque. 
     Four optional weight reduction openings  48  are used in an exemplary embodiment. 
     A plurality of index markings  50  are shown interior to each long dowel recess  44 . Index markings  50  are optional. When present, index markings  50  can show the user the degree of advance or retard of camshaft sprocket assembly. For example, index markings  50  can take the form of index lines, with each index line corresponding to a specified degree of increment. In further example, each index line could represent a 2° increment of advance (towards the left for the view shown in FIG. 8) or retard (towards right for the view shown in FIG.  8 ). In still a further embodiment, (not shown) each index line can have a numeric or other symbol marking to clearly advise the user of what degree of advance or retard is set or being set by the timing adjustment. Index markings  50  and any numeric or other symbol can be stamped or etched into camshaft sprocket  12 . 
     In an exemplary preferred embodiment, shown in FIGS. 11 and 12, index markings  50  are stamped or etched onto camshaft hub  14 , in place of one of the long dowel openings  30 . Index markings  50  are numbered in degree increments 6,4,2,0,2,4,6, with 0 marking the center line. An index marking indicator or arrow  51  is stamped or etched onto camshaft sprocket  12 . Index marking arrow  51  is located such that it can be seen when camshaft sprocket hub  14  is mated with camshaft sprocket  12 . In use, index marking arrow  51  will align with one of the index markings  51  to show the degree of advance or retard that has been adjusted by the user. Such an arrangement may make it easier for the user to see the adjustment being made. In an exemplary embodiment, camshaft sprocket assembly  10  is used for a Chevrolet® small block engine. For such an embodiment, camshaft sprocket gear  12  is machined from a blank of SAE 1144 billet steel; with 44 teeth  42  having a pitch of 0.375; six threaded securing bolt openings  46  are present, each being a ¼ ( 28 ) tap hole; and the following are approximate measurements for some of the dimensions shown in FIGS. 8 and 9. 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 H = 5.350″ 
                 ε = 30° 
               
               
                   
                 I = 4.38″ 
                 φ = 30° 
               
               
                   
                 J = .030″ 
                 γ = 45° 
               
               
                   
                 K = .605″ 
                 η = 45° 
               
               
                   
                 L = .205″ 
                 ι = 15° 
               
               
                   
                 M = .035″ 
                 φ = 86° 
               
               
                   
                 N = 2.626-2.628″ 
               
               
                   
                 O = 4.376-4.378″ 
               
               
                   
                 P = 4.440″ 
               
               
                   
                   
               
             
          
         
       
     
     FIGS. 10 and 11 show top and side views, respectively, of camshaft sprocket assembly  10  with camshaft sprocket hub  14  nested with camshaft sprocket  12  and secured by securing bolts  18 . Washers  16  are positioned between the heads of camshaft securing bolts  18  and the surface of camshaft hub  14 . Camshaft securing bolts  18  are shown with a hex recess (allen bolt) head. Other head configurations for the securing means will be understood by those skilled in the art. 
     In operation, a camshaft sprocket assembly  10  is already mounted on a camshaft with a timing chain fitted around teeth  42  and crankshaft sprocket (not shown) and thus, installed in a vehicle. To adjust the timing to a desired position, a user first loosens securing bolts  18  to allow movement of camshaft sprocket  12  independent of camshaft sprocket hub  14 . In an exemplary embodiment, six securing bolts  18  are provided. A user then inserts short dowel  24  and long dowel  26  of timing adjustment tool  20  into the respective openings in camshaft hub  14 . Short dowel  24  does not penetrate through camshaft hub  14 , while long dowel  26  does. Long dowel  26  is inserted through long dowel recess  44  in camshaft sprocket  12 . Handle extension  29  of timing adjustment tool  20  is inserted into the receiving end of a socket wrench (not shown) or similar tool to provide leverage for the timing adjustment. The socket wrench or similar tool is set to allow motion in the desired direction—advance or retard. Long dowel  26  acts as a pivot point, around which short dowel  24  can “scribe an arc” within the window of adjustment range that camshaft sprocket assembly  10  has been machined to provide. In an exemplary embodiment, the window of adjustment range is 12° (6° advance and 6° retard). A user can check the advance or retard setting by using index markings  50 , if provided. When the desired timing setting is reached, the user tightens securing bolts  18  to lock camshaft sprocket  12  to camshaft hub  14 . 
     While particular embodiments of the present invention are disclosed herein, it is not intended to limit the invention to such disclosure, and changes and modifications may be incorporated and embodied within the scope of the following claims.