Four-stroke cycle internal combusion engine

Abstract

According to some embodiments, there is provided a four-stroke cycle internal combustion engine in which an amount of valve lift is switchable in more multiple steps according to an operating range. In a four-stroke cycle internal combustion engine 1 including an intake valve 7 , an exhaust valve 6 , and a valve driving device 8 open/close-driving the intake valve 7 and the exhaust valve 6 , at least one of the intake valve 7 and the exhaust valve 6 is provided in plurality, and the valve driving device 8 includes a first and a second variable valve system 26, 26′ performing multi-step switching control of at least one of an opening/closing timing and an amount of lift of the valve provided in plurality, independently on a per valve basis.

1 . A four-stroke cycle internal combustion engine, comprising:
 at least one intake valve;   at least one exhaust valve; and   a valve driving device to open/close said at least one intake valve and said at least one exhaust valve,   wherein at least one of said at least one intake valve and said at least one exhaust valve includes a plurality of valves, and   wherein said valve driving device includes a variable valve system configured to perform control switching in multiple steps of at least one of an open/close-timing and an amount-of-lift of said plurality of valves independently on a per valve basis.   
     
     
         2 . The four-stroke cycle internal combustion engine according to  claim 1 ,
 wherein said variable valve system includes:   a cam nose which is provided in plurality per one valve; and   a transmission switching mechanism transmitting only a driving force of one of the cam noses to the valve.   
     
     
         3 . The four-stroke cycle internal combustion engine according to  claim 2 ,
 wherein the transmission switching mechanism is of a hydraulic type and includes a hydraulic cylinder mechanism, a hydraulic pressure supply path through which a hydraulic pressure is supplied to the hydraulic cylinder mechanism, and a hydraulic pressure control valve controlling the supply and discharge of the hydraulic pressure through the hydraulic pressure supply path.   
     
     
         4 . The four-stroke cycle internal combustion engine according to  claim 2 ,
 wherein a first intake valve and a second intake valve are provided; and   wherein said variable valve system comprises:   a first cam nose and a second cam nose provided for the first intake valve;   a third cam nose and a fourth cam nose provided for the second intake valve;   a first transmission switching mechanism of a hydraulic cylinder type transmitting a driving force of one of the first cam nose and the second cam nose to the first intake valve; and   a second transmission switching mechanism of a hydraulic cylinder type transmitting a driving force of one of the third cam nose and the fourth cam nose to the second intake valve.   
     
     
         5 . The four-stroke cycle internal combustion engine according to  claim 4 ,
 wherein the first transmission switching mechanism comprise:   a first and a second rocker arm rockably driven by the first and second cam noses;   a first cylinder portion formed in a cam carrier pivotally supporting a portion, of an intake camshaft, between the second cam noses and the third cam noses;   a first piston slidably disposed in the first cylinder portion; and   a first lock pin reciprocatably driven by the first piston to be engaged with or disengaged from the first or second rocker arm, and   wherein the second transmission switching mechanism comprise:   a third and a fourth rocker arm rockably driven by the third and fourth cam noses;   a second cylinder portion formed in a cam carrier pivotally supporting a portion, of an intake camshaft, between the second cam noses and the third cam noses;   a second piston slidably disposed in the second cylinder portions; and   a second lock pin reciprocatably driven by the pistons to be engaged with or disengaged from the third or fourth rocker arm.   
     
     
         6 . The four-stroke cycle internal combustion engine according to  claim 4 ,
 wherein a cam profile of the first cam nose is set so that the first intake valve has a valve operating angle of 250° or more and is closed at a timing of 90° or larger after a bottom dead center, and a cam profile of the third cam nose is set so that an amount of lift of the second intake valve becomes 2 mm or less; and   wherein, in a low speed/low load operating range, the variable valve system open/close-drives the first intake valve by the first cam nose and open/close-drives the second intake valve by the third cam nose.   
     
     
         7 . The four-stroke cycle internal combustion engine according to  claim 1 ,
 wherein the intake valve is provided in plurality, and   wherein at least one of the plural intake valves has a valve operating angle of 250° or more and is closed at a timing of 90° or larger after a bottom dead center, and an amount of lift of at least one of the remaining intake valves is 2 mm or less.   
     
     
         8 . A four-stroke cycle internal combustion engine, comprising:
 at least one intake valve;   at least one exhaust valve; and   means for opening and closing said at least one intake valve and said at least one exhaust valve,   wherein at least one of said at least one intake valve and said at least one exhaust valve includes a plurality of valves, and   wherein said means for opening and closing further includes means for controlling switching in multiple steps of at least one of an open/close-timing and an amount-of-lift of said plurality of valves independently on a per valve basis.   
     
     
         9 . The four-stroke cycle internal combustion engine according to  claim 8 , wherein said means for opening and closing includes a variable valve system, and said means for controlling switching includes at least one driving element and a transmission per one valve and a transmission switching mechanism that transmits a drive force via the at least one driving element. 
     
     
         10 . The four-stroke cycle internal combustion engine according to  claim 9 ,
 wherein said at least one driving element is at least one cam nose, and wherein the transmission switching mechanism is a hydraulic mechanism.   
     
     
         11 . A method for providing multi-step switching of valves in a four-stroke cycle internal combustion engine, comprising the steps of:
 providing at least one intake valve and at least one exhaust valve, wherein at least one of said at least one intake valve and said at least one exhaust valve includes a plurality of valves; and   controlling switching in multiple steps of at least one of an open/close-timing and an amount-of-lift of said plurality of valves independently on a per valve basis.   
     
     
         12 . The method of  claim 11 , further including controlling switching in multiple steps using a variable valve system having at least one driving element and a transmission switching mechanism that transmits a drive force via the at least one driving element. 
     
     
         13 . The method of  claim 11 , including controlling switching in multiple steps of an open/close-timing of said plurality of valves independently on a per valve basis. 
     
     
         14 . The method of  claim 11 , including controlling switching in multiple steps of an amount of lift of said plurality of valves independently on a per valve basis.