Skip fire valve control

Abstract

In various aspects, internal combustion engines, engine controllers and methods of controlling engines are described. The engine includes a camshaft and a two cylinder sets. Cylinders in the first are deactivatable and cylinders in the second set may be fired at high or low output levels. The air charge for each fired working cycle is set based on whether a high or low torque output is selected. In some implementations, the camshaft is axially shiftable between first and second positions. First cam lobes are configured to cause their associated cylinders to intake a large air charge during intake strokes that occur when the camshaft is in the first position. Second cam lobes for cylinders in the second set cause their associated cylinders to intake a smaller air charge when the camshaft is in the second position. Second cam lobes for cylinders in the first set deactivate their associated cylinders.

What is claimed is: 
     
         1 . A method of controlling operation of an internal combustion engine having a plurality of working chambers, wherein each working chamber is defined by a cylinder having at least one intake valve and at least one exhaust valve, the method comprising:
 operating the engine to deliver a desired engine output;   detecting a condition that the engine is coasting or decelerating;   in response to said condition, preventing fuel to be delivered to all of the working chambers; and   during said condition, operating the intake valves of the working chambers to control a specified air charge of air passing through the cylinders of the non-fueled working chambers;   operating the engine to deliver a desired engine output;   detecting a condition that that no torque is being requested from the engine;   in response to said condition, preventing fuel to be delivered to all of the working chambers; and   during said condition, operating the intake valves of the working chambers to control a specified air charge of air passing through the cylinders of the non-fueled working chambers.   
     
     
         2 . The method as recited in  claim 1 , wherein the condition is detected as a result of no torque being requested from the engine. 
     
     
         3 . The method as recited in  claim 2 , wherein the air charge is controlled by controlling the timing of one or more of the opening and closing of the intake valve. 
     
     
         4 . The method as recited in  claim 2 , wherein the air charge is controlled by controlling a valve lift profile of the intake valve. 
     
     
         5 . The method as recited in  claim 2 , wherein the intake valve is operated to reduce air induction compared to a normal lift profile. 
     
     
         6 . The method as recited in  claim 5 , wherein timing of the intake valve is actuated to implement an early intake valve closing (EIVC) or late intake valve closing (LIVC) profile to reduce said air induction. 
     
     
         7 . The method as recited in  claim 1 , wherein fuel delivery is prevented to the working chambers according to a decel cutoff state. 
     
     
         8 . The method as recited in  claim 7 , wherein the decel cutoff state comprises deceleration fuel cutoff (DFCO). 
     
     
         9 . A method of controlling operation of an internal combustion engine having a plurality of working chambers, wherein each working chamber is defined by a cylinder having at least one intake valve and at least one exhaust valve, the method comprising:
 operating the engine to deliver a desired engine output;   detecting a condition that that no torque is being requested from the engine;   in response to said condition, preventing fuel to be delivered to all of the working chambers; and   during said condition, operating the intake valves of the working chambers to control a specified air charge of air passing through the cylinders of the non-fueled working chambers.   
     
     
         10 . The method as recited in  claim 9 , wherein the air charge is controlled by controlling the timing of one or more of the opening and closing of the intake valve, or by controlling a valve lift profile of the intake valve 
     
     
         11 . The method as recited in  claim 9 , wherein the intake valve is operated to reduce air induction compared to a normal lift profile. 
     
     
         12 . The method as recited in  claim 11 , wherein timing of the intake valve is actuated to implement an early intake valve closing (EIVC) or late intake valve closing (LIVC) profile to reduce said air induction. 
     
     
         13 . The method as recited in  claim 9 , wherein fuel delivery is prevented to the working chambers according to a decel cutoff state. 
     
     
         14 . An internal combustion engine, comprising:
 a plurality of working chambers, wherein each working chamber is defined by a cylinder having at least one intake valve and at least one exhaust valve;   a controller operatively coupled to direct operation of engine including the at least one intake valve and at least one exhaust valve;   the controller further configured for:
 directing operation of the engine to deliver a desired engine output; 
 detecting a condition that the engine is coasting or decelerating; 
 in response to said condition, preventing fuel to be delivered to all of the working chambers; and 
 during said condition, directing operation of the intake valves of the working chambers to control a specified air charge of air passing through the cylinders of the non-fueled working chambers; 
   
       wherein the condition is detected as a result of no torque being requested from the engine. 
     
     
         15 . The engine as recited in  claim 14 , wherein the air charge is controlled by controlling the timing of one or more of the opening and closing of the intake valve. 
     
     
         16 . The engine as recited in  claim 14 , wherein the air charge is controlled by controlling a valve lift profile of the intake valve. 
     
     
         17 . The engine as recited in  claim 14 , wherein the intake valve is operated to reduce air induction compared to a normal lift profile. 
     
     
         18 . The engine as recited in  claim 17 , wherein timing of the intake valve is actuated to implement an early intake valve closing (EIVC) or late intake valve closing (LIVC) profile to reduce said air induction. 
     
     
         19 . The engine as recited in  claim 14 , wherein fuel delivery is prevented to the working chambers according to a decel cutoff state. 
     
     
         20 . The engine as recited in  claim 19 , wherein the decel cutoff state comprises deceleration fuel cutoff (DFCO).