Valve drive system of internal combustion engine

Abstract

A valve drive system of internal combustion engine which operates at a high compression ratio cycle, which is provided with an intake cam 52 a and intake cam 52 b for operating intake valves 7 a , 7 b and a variable valve timing device 70 which can offset the operating timings of the intake valves 7 a , 7 b by the intake cam 52 a and the operating timings of the intake valves 7 a , 7 b by the intake cam 52 b from each other. The intake cam 52 a and intake cam 52 b include circular parts and cam noses. At least one of the cam nose of the intake cam 52 a and cam nose of the intake cam 52 b has a concentric circular part which is formed in a circular shape concentric with the circular part.

1 .- 4 . (canceled) 
     
     
         5 . A valve drive system of an internal combustion engine which can increase an expansion ratio when fuel burns and a piston is pushed compared with an actual compression ratio when an air-fuel mixture which contains fuel is compressed by a piston, the valve drive system of the internal combustion engine provided with
 a first intake cam and a second intake cam which operate intake valves and   a variable valve timing device which changes at least one operating timing of an operating timing of intake valves by the first intake cam and an operating timing of intake valves by the second intake cam, wherein   the intake valve is formed to be operated by being driven by the first intake cam and the second intake cam,   the variable valve timing device is formed so as to be able to offset the operating timing of the intake valves by the first intake cam and the operating timing of the intake valves by the second intake cam,   the first intake cam and the second intake cam include circular parts of substantially circular cross-sectional shapes and bulging parts which project from the circular parts and which drive the intake valves,   at least one of the bulging part of the first intake cam and the bulging part of the second intake cam has a concentric circular part which is formed in a concentric circular shape with the circular part, and   the concentric circular part holds an amount of movement of the intake valve substantially constant in a period during which the intake valve is open.   
     
     
         6 . A valve drive system of internal combustion engine as set forth in  claim 5 , wherein
 the bulging part of the first intake cam and the bulging part of the second intake cam have concentric circular parts,   the first intake cam and the second intake cam are formed so that the amount of movement of the intake valve which is driven by the concentric circular part of the first intake cam and the amount of movement of the intake valve which is driven by the concentric circular part of the second intake cam become substantially the same,   when the operating timing of the intake valves by the first intake cam and the operating timing of the intake valves by the second intake cam are different from each other, a time period where the concentric circular part of the first intake cam opens the intake valve and a time period where the concentric circular part of the second intake cam opens the intake valve overlap each other.   
     
     
         7 . A valve drive system of internal combustion engine as set forth in  claim 5 , further provided with an operating state detection device which detects an operating state of the internal combustion engine, wherein
 the system detects the operating state of the internal combustion engine and determines an amount of offset between the operating timing of the intake valves by the first intake cam and the operating timing of the intake valves by the second intake cam in accordance with the operating state of the internal combustion engine.   
     
     
         8 . A valve drive system of internal combustion engine as set forth in  claim 7  in which a first intake valve and second intake valve are arranged for each cylinder, the valve drive system of internal combustion engine further provided with
 a first transmission member which is interposed between the first intake cam and the first intake valve and transmits drive force of the first intake cam to the first intake valve, 
 a second transmission member which is interposed between the second intake cam and the second intake valve and transmits drive force of the second intake cam to the second intake valve, and 
 a coupling device for coupling and separating the first transmission member and the second transmission member, wherein 
 the system couples or separates the first transmission member and the second transmission member in accordance with the operating state of the internal combustion engine. 
 
     
     
         9 . A valve drive system of internal combustion engine as set forth in  claim 6 , further provided with an operating state detection device which detects an operating state of the internal combustion engine, wherein
 the system detects the operating state of the internal combustion engine and determines an amount of offset between the operating timing of the intake valves by the first intake cam and the operating timing of the intake valves by the second intake cam in accordance with the operating state of the internal combustion engine.   
     
     
         10 . A valve drive system of internal combustion engine as set forth in  claim 9  in which a first intake valve and second intake valve are arranged for each cylinder, the valve drive system of internal combustion engine further provided with
 a first transmission member which is interposed between the first intake cam and the first intake valve and transmits drive force of the first intake cam to the first intake valve, 
 a second transmission member which is interposed between the second intake cam and the second intake valve and transmits drive force of the second intake cam to the second intake valve, and 
 a coupling device for coupling and separating the first transmission member and the second transmission member, wherein 
 the system couples or separates the first transmission member and the second transmission member in accordance with the operating state of the internal combustion engine.