Internal combustion engine for a snowmobile

Abstract

A snowmobile includes an improved internal combustion engine. The engine comprises a crankcase, a crankshaft rotatably journaled within the crankcase, a cylinder block assembly extending from the crankcase, and a cylinder head assembly connected to an end of the cylinder block opposite the crankcase. A cam drive mechanism including at least one camshaft is rotatably journaled within the cylinder head assembly. A transmission is coupled to the crankshaft to transmit power from the engine to the drive assembly. The cam drive mechanism is connected to the crankshaft at a first end portion of the crankshaft. The transmission is connected to the crankshaft at a second end portion of the crankshaft opposite the first end portion.

1. A snowmobile comprising a frame assembly, a drive assembly coupled to the frame assembly and including a drive belt adapted to contact a ground surface to propel the snowmobile over the ground surface, an internal combustion engine supported by the frame assembly, the engine comprising a crankcase, a crankshaft rotatably journaled within the crankcase, a cylinder block assembly extending from the crankcase, a cylinder head assembly connected to an end of the cylinder block opposite the crankcase, and a cam drive mechanism including at lest one camshaft rotatably journaled within the cylinder head assembly, and a transmission coupled to the crankshaft to transmit power from the engine to the drive assembly, wherein the cam drive mechanism is connected to the crankshaft, at a first end portion of the crankshaft, and the transmission is connected to the crankshaft at a second end portion of the crankshaft opposite the first end portion. 
     
     
       2. The snowmobile of claim  1    4 , wherein the crankshaft includes a drive sprocket at the second end portion thereof, the camshaft includes a driven sprocket, and a flexible transmitter extends around the drive sprocket and the driven sprocket to drive the camshaft from the crankshaft. 
     
     
       3. The snowmobile of  claim 2 , wherein a diameter of the driven sprocket is twice a diameter of the drive sprocket. 
     
     
       4. The snowmobile of  claim 1 ,  A snowmobile comprising a frame assembly, a drive assembly coupled to the frame assembly and including a drive belt adapted to contact a ground surface to propel the snowmobile over the ground surface, an internal combustion engine supported by the frame assembly, the engine comprising a crankcase, a crankshaft rotatably journaled within the crankcase, a cylinder block assembly extending from the crankcase, a cylinder head assembly connected to an end of the cylinder block opposite the crankcase, and a cam drive mechanism including at least one camshaft rotatably journaled within the cylinder head assembly, and a transmission coupled to the crankshaft to transmit power from the engine to the drive assembly, wherein the transmission is connected to the crankshaft at a first end portion of the crankshaft, and the cam drive mechanism is connected to the crankshaft at a second end portion of the crankshaft opposite the first end portion, wherein a diameter of the crankshaft at the second end portion is less than a diameter of the crankshaft at the first end portion. 
     
     
       5. The snowmobile of  claim 1 ,  A snowmobile comprising a frame assembly, a drive assembly coupled to the frame assembly and including a drive belt adapted to contact a ground surface to propel the snowmobile over the ground surface, an internal combustion engine supported by the frame assembly, the engine comprising a crankcase, a crankshaft rotatably journaled within the crankcase, a cylinder block assembly extending from the crankcase, a cylinder head assembly connected to an end of the cylinder block opposite the crankcase, and a cam drive mechanism including at least one camshaft rotatably journaled within the cylinder head assembly, and a transmission coupled to the crankshaft to transmit power from the engine to the drive assembly, wherein the transmission is connected to the crankshaft at a first end portion of the crankshaft, and the cam drive mechanism is connected to the crankshaft at a second end portion of the crankshaft opposite the first end portion, further comprising a flywheel magneto assembly coupled to the crankshaft at the second end portion thereof. 
     
     
       6. The snowmobile of  claim 5 , wherein the flywheel magneto assembly comprises a rotor having a shaft, and an end of the shaft is coupled to the crankshaft at the second end portion thereof. 
     
     
       7. The snowmobile comprising a frame assembly, a drive assembly coupled to the frame assembly and including a drive belt adapted to contact a ground surface to propel the snowmobile over the ground surface, an internal combustion engine supported by the frame assembly, the engine comprising a crankcase, a crankshaft rotatably journaled within the crankcase, a cylinder block assembly extending from the crankcase and defining at least one cylinder bore, a piston positioned for reciprocating movement in the cylinder bore, a connecting rod coupled to the piston and to the crankshaft to transmit motion therebetween, a cylinder head assembly connected to an end of the cylinder block opposite the crankcase, and a cam drive mechanism including at least one camshaft rotatably journaled within the cylinder head assembly, and a transmission coupled to the crankshaft to transmit power form the engine to the drive assembly, wherein the transmission and the cam drive mechanism are coupled to the crankshaft on opposite sides of the connecting rod. 
     
     
       8. The snowmobile of claim  7    10 , wherein the crankshaft includes a drive sprocket at an end portion thereof, the camshaft includes a driven sprocket, and a flexible transmitter extends around the drive sprocket and the driven sprocket to drive the camshaft from the crankshaft. 
     
     
       9. The snowmobile of  claim 8 , wherein a diameter of the driven sprocket is twice a diameter of the drive sprocket. 
     
     
       10. The snowmobile of  claim 7   A snowmobile comprising a frame assembly, a drive assembly coupled to the frame assembly and including a drive belt adapted to contact a ground surface to propel the snowmobile over the ground surface, an internal combustion engine supported by the frame assembly, the engine comprising a crankcase, a crankshaft rotatably journaled within the crankcase, a cylinder block assembly extending from the crankcase and defining at least one cylinder bore, a piston positioned for reciprocating movement in the cylinder bore, a connecting rod coupled to the piston and to the crankshaft to transmit motion therebetween, a cylinder head assembly connected to an end of the cylinder block opposite the crankcase, and a cam drive mechanism including at least one camshaft rotatably journaled within the cylinder head assembly, and a transmission coupled to the crankshaft to transmit power from the engine to the drive assembly, wherein the transmission and the cam drive mechanism are coupled to the crankshaft on opposite sides of the connecting rod, wherein a diameter of the crankshaft at the drive sprocket is less than a diameter of crankshaft at the transmission. 
     
     
       11. The snowmobile of  claim 7   A snowmobile comprising a frame assembly, a drive assembly coupled to the frame assembly and including a drive belt adapted to contact a ground surface to propel the snowmobile over the ground surface, an internal combustion engine supported by the frame assembly, the engine comprising a crankcase, a crankshaft rotatably journaled within the crankcase, a cylinder block assembly extending from the crankcase and defining at least one cylinder bore, a piston positioned for reciprocating movement in the cylinder bore, a connecting rod coupled to the piston and to the crankshaft to transmit motion therebetween, a cylinder head assembly connected to an end of the cylinder block opposite the crankcase, and a cam drive mechanism including at least one camshaft rotatably journaled within the cylinder head assembly, and a transmission coupled to the crankshaft to transmit power from the engine to the drive assembly, wherein the transmission and the cam drive mechanism are coupled to the crankshaft on opposite sides of the connecting rod, further comprising a flywheel magneto assembly coupled to the end portion of the crankshaft the  adjacent the drive sprocket. 
     
     
       12. The snowmobile of  claim 11 , wherein the crankshaft includes a drive sprocket at an end portion thereof, the camshaft includes a driven sprocket, and a flexible transmitter extends around the drive sprocket and the driven sprocket to drive the camshaft from the crankshaft.  
     
     
       13. The snowmobile of  claim 12 , wherein a diameter of the drive sprocket is twice a diameter of the drive sprocket.  
     
     
       14. The snowmobile of  claim 5 , wherein the crankshaft includes a drive sprocket at the second end portion thereof, the camshaft includes a driven sprocket, and a flexible transmitter extends around the drive sprocket and the driven sprocket to drive the camshaft from the crankshaft.  
     
     
       15. The snowmobile of  claim 14 , wherein a diameter of the driven sprocket is twice a diameter of the drive sprocket.  
     
     
       16. A snowmobile comprising an engine driving a drive assembly, the drive assembly mounted to a frame assembly, the drive assembly including a drive belt adapted to contact a ground surface to propel the snowmobile over the ground surface, an internal combustion engine supported by the frame assembly, the engine comprising a center of gravity, a crankcase, a crankshaft rotatably journaled within the crankcase, a cylinder block assembly extending from the crankcase and defining at least one cylinder bore, a first valve regulating communication between a combustion gas passage and a cylinder bore and a second valve regulating communication between a combustion gas passage and a cylinder bore, a piston positioned for reciprocating movement in the cylinder bore, a connecting rod coupled to the piston and to the crankshaft to transmit motion therebetween, and a cam drive mechanism including a first cam lobe for actuating said first valve, a second cam lobe for actuating said second valve, at least one camshaft rotatably journaled within the engine and configured to actuate at least one of said first and second cam lobes, and a transmission coupled to the crankshaft to transmit power from the engine to the drive assembly, the transmission and the cam drive mechanism being coupled to the crankshaft on opposite sides of the connecting rod and arranged such that the center of gravity is located on the plane located between said first cam lobe and second cam lobe.  
     
     
       17. The snowmobile of  claim 16 , wherein the crankshaft includes a drive sprocket at an end portion thereof, the camshaft includes a driven sprocket, and a flexible transmitter extends around the drive sprocket and the driven sprocket to drive the camshaft from the crankshaft.  
     
     
       18. The snowmobile of  claim 17 , wherein a diameter of the driven sprocket is twice a diameter of the drive sprocket.  
     
     
       19. The snowmobile of  claim 16 , wherein a diameter of the crankshaft at the drive sprocket is less than a diameter of crankshaft at the transmission.  
     
     
       20. The snowmobile of  claim 16 , further comprising a flywheel magneto assembly coupled to the end portion of the crankshaft the adjacent the drive sprocket.  
     
     
       21. The snowmobile of  claim 16 , wherein the piston comprises a first piston and the connecting rod comprises a first connecting rod and further comprising a second piston and a second connecting rod, the second connecting rod coupled with the second piston and with the crankshaft to transmit motion therebetween, whereby the center of gravity of the engine is located between the first cylinder bore and the second cylinder bore.