Discrete variable valve lift engine systems and methods

Abstract

A method of providing a rocker arm set for a valvetrain includes providing a first rocker arm configured as a switching rocker arm for a first intake valve, and providing a second rocker arm configured as a fixed rocker arm for a second intake valve, the second rocker arm operating in a normal Otto cycle mode. The first rocker arm operates in a late intake valve closing (LIVC) mode where the first rocker arm is configured to close the first intake valve later than the second intake valve.

1 - 49 . (canceled) 
     
     
         50 . A valvetrain configuration comprising:
 a first rocker arm configured to be engaged by a cam and configured as a switching rocker arm for a first intake valve, the first rocker arm configured to selectively switch between a normal mode and a late intake valve closing (LIVC) mode; and   a second rocker arm configured as a fixed rocker arm for a second intake valve, the second rocker arm operating in a normal Otto cycle mode;   wherein in the LIVC mode the first rocker arm is configured to close the first intake valve later than the second intake valve; and   wherein the first rocker arm is switched from the normal mode to the LIVC mode on a downward slope of the cam such that a LIVC mode valve lift closing is extended relative to a normal mode valve lift closing.   
     
     
         51 . The valvetrain of  claim 50 , wherein a lost motion between the LIVC mode valve lift closing and the normal mode valve lift closing is between approximately 2 mm and approximately 4 mm. 
     
     
         52 . The valvetrain of  claim 51 , wherein the lost motion is approximately 3 mm. 
     
     
         53 . The valvetrain of  claim 50 , wherein a lost motion between the LIVC mode valve lift closing and the normal mode valve lift closing is between 2 mm and 4 mm. 
     
     
         54 . The valvetrain of  claim 53 , wherein the lost motion is 3 mm. 
     
     
         55 . The valvetrain of  claim 50 , wherein the cam is a single lobe cam. 
     
     
         56 . The valvetrain of  claim 55 , wherein load is generated only on the decelerating portion of the cam. 
     
     
         57 . A method of assembling a valvetrain for an internal combustion engine, the method comprising:
 providing a first rocker arm configured to be engaged by a cam and configured as a switching rocker arm for a first intake valve, the first rocker arm configured to selectively switch between a normal mode and a late intake valve closing (LIVC) mode; and   providing a second rocker arm configured as a fixed rocker arm for a second intake valve, the second rocker arm operating in a normal Otto cycle mode;   wherein in the LIVC mode the first rocker arm is configured to close the first intake valve later than the second intake valve; and   wherein the first rocker arm is switched from the normal mode to the LIVC mode on a downward slope of the cam such that a LIVC mode valve lift closing is extended relative to a normal mode valve lift closing.   
     
     
         58 . The method of  claim 57 , further comprising providing the first and second rocker arms such that a lost motion between the LIVC mode valve lift closing and the normal mode valve lift closing is between approximately 2 mm and approximately 4 mm. 
     
     
         59 . The method of  claim 58 , wherein the lost motion is approximately 3 mm. 
     
     
         60 . The method of  claim 57 , further comprising providing the first and second rocker arms such that a lost motion between the LIVC mode valve lift closing and the normal mode valve lift closing is between 2 mm and 4 mm. 
     
     
         61 . The method of  claim 60 , wherein the lost motion is 3 mm. 
     
     
         62 . The method of  claim 57 , further comprising providing the first rocker arm for a single lobe cam. 
     
     
         63 . The method of  claim 62 , further comprising providing the first rocker arm such that a load is generated only on the decelerating portion of the cam. 
     
     
         64 . A valvetrain configuration comprising:
 a first switching rocker arm for a first intake valve, the first switching rocker arm configured to be engaged by a cam and to selectively switch between a normal mode and an early intake valve closing (EIVC) mode; and   a second switching rocker arm for a second intake valve, the second switching rocker arm configured to selectively switch between a normal mode and an early intake valve closing;   wherein in the EIVC mode the first switching rocker arm is configured to close the first intake valve later than when the first or second intake valve is closed in the normal mode; and   wherein the first switching rocker arm is switched from the normal mode to the EIVC mode on a downward slope of the cam such that a EIVC mode valve lift closing is extended relative to a normal mode valve lift closing.   
     
     
         65 . The valvetrain of  claim 64 , wherein a lost motion between the EIVC mode valve lift closing and the normal mode valve lift closing is between approximately 6 mm and approximately 8 mm. 
     
     
         66 . The valvetrain of  claim 65 , wherein the lost motion is approximately 7 mm. 
     
     
         67 . The valvetrain of  claim 64 , wherein a lost motion between the EIVC mode valve lift closing and the normal mode valve lift closing is between 6 mm and 8 mm. 
     
     
         68 . (canceled) 
     
     
         69 . The valvetrain of  claim 64 , wherein the cam is a single lobe cam. 
     
     
         70 . The valvetrain of  claim 64 , wherein a maximum lift of the first switching rocker arm in the EIVC mode corresponds to a choke point of the first intake valve. 
     
     
         71 - 129 . (canceled)