Cam contacting devices

Abstract

The invention relates to improved cam contacting devices for use in internal combustion engines and preferably for use in internal combustion engines having variable valve timing. In particular, the use of ceramics including silicon nitride and silicon carbide have been demonstrated as providing effective cam contacting surfaces allowing an axially displaceable cam shaft having a variable profile cam to be run with resulting improvements in idle speed and volumetric efficiency.

1 . A cam contacting device having improved thermal properties for use in an internal combustion engine.  
     
     
         2 . A cam contacting device as in  claim 1  having a density less than 6 g/cc.  
     
     
         3 . A cam contacting device as in  claim 2  having a density of about 3.1-3.2 g/cc.  
     
     
         4 . A cam contacting device as in  claim 1  having a Young's modulus greater than 310 Gpa.  
     
     
         5 . A cam contacting device as in  claim 4  having aYoung's modulus of about 310-450 Gpa.  
     
     
         6 . A cam contacting device as in  claim 1  having a Vickers hardness greater than 1150 (Hv).  
     
     
         7 . A cam contacting device as in  claim 6  having a Vickers hardness of about 1650-2850 (Hv).  
     
     
         8 . A cam contacting device as in  claim 1  having a coefficient of thermal expansion less than 10.5×10 −6 /degree Celsius.  
     
     
         9 . A cam contacting device as in clam  8  having a coefficient of thermal expansion of about 3.1-5.5×10 −6 /degree Celsius.  
     
     
         10 . A cam contacting device as in  claim 1  having a thermal conductivity less than 50 W/m K.  
     
     
         11 . A cam contacting device as in  claim 10  having a thermal conductivity of about 22-26 W/m K.  
     
     
         12 . A cam contacting device as in  claim 1  having a Weibull modulus greater than 12.  
     
     
         13 . A cam contacting device as in  claim 12  having a Weibull modulus of about 12-18.  
     
     
         14 . A cam contacting device as in  claim 1  having an abrasive wear resistance greater than 900.  
     
     
         15 . A cam contacting device as in  claim 14  having an abrasive wear resistance of about 947-1263.  
     
     
         16 . A cam contacting device as in  claim 1  wherein the cam contacting device is a ball bearing having any one of or a combination of the properties in claims  1 - 15 .  
     
     
         17 . A cam contacting device as in  claim 1  wherein the cam contacting device is a ball bearing within a bearing race and support and wherein the coefficient of thermal expansion of the ball bearing is less than the coefficient of thermal expansion of the bearing race and support.  
     
     
         18 . A cam contacting device as in  claim 1  wherein the cam contacting device is a ceramic ball bearing within a steel bearing race and support.  
     
     
         19 . A cam contacting device as in  claim 18  wherein the ball bearing is any one of silicon nitride or silicon carbide.  
     
     
         20 . A cam contacting device as in  claim 1  wherein the cam contacting material is selected from any one of CERALLOY 147-31E, 147-31N, 147-1E, or 147-1.  
     
     
         21 . A cam contacting device as in  claim 1  wherein the cam contacting device is any one of a radiused wheel, a ball bearing or a semi-spherical surface.  
     
     
         22 . A cam contacting device as in  claim 21  wherein the cam contacting material is selected from any one of CERALLOY 147-31E, 147-31N, 147-1E, or 147-1.  
     
     
         23 . A cam contacting device as in any one of claims  1 - 22  wherein the cam contacting device includes a lubrication system for providing lubrication to the cam contacting device/cam interface.  
     
     
         24 . The use of a cam contacting device as described in any one of claims  1 - 23  in an internal combustion engine having variable profile cams.  
     
     
         25 . In an internal combustion engine having cylinders, a rotating camshaft, valves and valve lifters in operative communication between the valves and rotating camshaft, the improvement comprising a variable profile camshaft and valve lifters linearly displaceable with respect to one another wherein the valve lifters include a silicon nitride bearing for operative contact with the rotating camshaft.  
     
     
         26 . An internal combustion engine as in  claim 25  further comprising a valve seat having fuel injection ports within the valve seat for injecting fuel into the cylinders.