Method and apparatus for operating an internal combustion engine
An internal combustion engine includes intake and exhaust camshafts including high-lift lobes and low-lift lobes separated by a lobe separation angle. The engine transitions between operating in a controlled auto-ignition combustion mode with positive valve overlap and a controlled auto-ignition combustion mode with negative valve overlap solely by selecting the corresponding one of the high-lift lobes and the low-lift lobes.
1. A method for controlling a spark-ignition direct injection internal combustion engine including intake and exhaust camshafts and intake and exhaust valves, the method comprising:
providing a low-lift intake lobe and a high-lift intake lobe on the intake camshaft, said low-lift intake lobe and said high-lift intake lobe separated by a predetermined intake lobe separation angle;
providing a low-lift exhaust lobe and a high-lift exhaust lobe on the exhaust camshaft, said low-lift exhaust lobe and said high-lift exhaust lobe separated by a predetermined exhaust lobe separation angle;
operating the engine in a controlled auto-ignition combustion mode with a positive valve overlap using the high-lift intake and exhaust lobes;
operating the engine in the controlled auto-ignition combustion mode with a negative valve overlap using the low-lift intake and exhaust lobes; and
transitioning between operating the engine in the controlled auto-ignition combustion mode with positive valve overlap and the controlled auto-ignition combustion mode with negative valve overlap solely by switching between using the high-lift intake and exhaust lobes and the low-lift intake and exhaust lobes.
2. The method of claim 1 , wherein switching between using the high-lift intake and the low-lift intake lobes and switching between using the high-lift exhaust and the low-lift exhaust lobes are effected simultaneously.
3. The method of claim 2 , further comprising transitioning from operating the engine in the controlled auto-ignition combustion mode with a negative valve overlap using the low-lift intake and exhaust lobes to operating the engine in a spark-ignition combustion mode using the high-lift intake and exhaust lobes by intermediately operating the engine in the controlled auto-ignition combustion mode with a positive valve overlap using the high-lift intake and exhaust lobes.
4. The method of claim 2 , further comprising transitioning from operating the engine in a spark-ignition combustion mode using the high-lift intake and exhaust lobes to operating the engine in the controlled auto-ignition combustion mode with a negative valve overlap using the low-lift intake and exhaust lobes by intermediately operating the engine in the controlled auto-ignition combustion mode with a positive valve overlap using the high-lift intake and exhaust lobes.
5. The method of claim 1 wherein transitions between operating the engine in the controlled auto-ignition combustion mode and the controlled auto-ignition combustion mode are effected at predetermined intake and exhaust camshaft phasings.
6. An internal combustion engine including variable volume combustion chambers defined by moveable pistons connected to a crankshaft rotationally connected to intake and exhaust camshafts operative to actuate intake and exhaust engine valves, comprising:
the intake and exhaust camshafts each including high-lift lobes and corresponding low-lift lobes, the high-lift lobes each including a peak position rotationally offset from a peak position of the corresponding low-lift lobe by a predetermined angle, wherein the peak position of the high-lift lobe is retarded relative to the peak position of the low-lift lobe for the exhaust camshaft and the peak position of the high-lift lobe is advanced relative to the peak position of the low-lift lobe for the intake camshaft;
intake and exhaust variable valve lift control devices configured for selective engagement of one of the high-lift lobes and the corresponding low-lift lobes of the intake and exhaust camshafts to control magnitudes of valve lift of the intake and exhaust valves to one of high-lift valve open positions and low-lift valve open positions;
the engine configured to achieve a first thermodynamic state with a positive valve overlap when the intake and exhaust variable valve lift control devices control the intake and exhaust valves to the high-lift valve open positions and configured to achieve the first thermodynamic state with a negative valve overlap when the intake and exhaust variable valve lift control devices control the intake and exhaust valves to the low-lift valve open positions, the high-lift and low-lift valve open positions having identical predetermined intake and exhaust cam phasing angles where the first thermodynamic state is achieved.
7. The internal combustion engine of claim 6 , wherein the peak position of the high-lift lobe for the intake camshaft is advanced by at least forty degrees of crank angle rotation.
8. The internal combustion engine of claim 6 , wherein the peak position of the high-lift lobe for the exhaust camshaft is retarded by at least forty degrees of crank angle rotation.
9. The internal combustion engine of claim 6 , further comprising variable cam phasing systems configured to control phasings of the intake and exhaust valves.
10. The internal combustion engine of claim 6 , further comprising the engine configured to achieve the first thermodynamic state comprising a first cylinder charge dilution and a combustion charge ignition temperature with a positive valve overlap when the intake and exhaust variable valve lift control devices control the intake and exhaust valves to the high-lift valve open positions and with a negative valve overlap when the intake and exhaust variable valve lift control devices control the intake and exhaust valves to the low-lift valve open positions, the high-lift and low-lift valve open positions having identical predetermined intake and exhaust cam phasing angles where the first thermodynamic state is achieved.
11. The internal combustion engine of claim 9 , further comprising the engine configured to achieve the first thermodynamic state when the intake and exhaust valves are controlled to the high-lift valve open positions and the phasings of the intake and exhaust valves are controlled to the predetermined intake and exhaust cam phasing angles and configured to achieve the first thermodynamic state when the intake and exhaust valves are controlled to low-lift valve open positions and the phasings of the intake and exhaust valves are controlled to the predetermined intake and exhaust cam phasing angles.
12. An internal combustion engine, comprising:
a combustion chamber;
an intake valve and an exhaust valve associated with the combustion chamber;
an intake camshaft having a high-lift intake lobe including a peak position and a low-lift intake lobe including a peak position, the peak positions rotationally separated by an intake lobe separation angle, wherein the peak position of the high-lift intake lobe is advanced relative to the peak position of the low-lift intake lobe;
an exhaust camshaft having a high-lift exhaust lobe including a peak position and a low-lift exhaust lobe including a peak position, the peak positions rotationally separated by an exhaust lobe separation angle, wherein the peak position of the high-lift exhaust lobe is retarded relative to the peak position of the low-lift exhaust lobe;
an intake valve lift control device for coupling one of the high-lift intake lobe and the low-lift intake lobe to the intake valve;
an exhaust valve lift control device for coupling one of the high-lift exhaust lobe and the low-lift exhaust lobe to the exhaust valve;
an intake camshaft phasing device configured to control intake camshaft phasing;
an exhaust camshaft phasing devices configured to control exhaust camshaft phasing; and
said intake lobe separation angle and said exhaust lobe separation angle configured such that
when the intake valve lift control device couples the high-lift intake lobe to the intake valve and the exhaust valve lift control device couples the high-lift exhaust lobe to the exhaust valve, the engine is operated in a high valve lift positive valve overlap state,
when the intake valve lift control device couples the low-lift intake lobe to the intake valve and the exhaust valve lift control device couples the low-lift exhaust lobe to the exhaust valve, the engine is operated in a low valve lift negative valve overlap state, and
when the intake and exhaust camshafts are at identical predetermined intake and exhaust camshaft phasing angles, a thermodynamic state established within the combustion chamber corresponding to the high valve lift positive valve overlap state and a thermodynamic state established within the combustion chamber corresponding to the low valve lift negative valve overlap state are substantially equivalent.
13. The internal combustion engine of claim 12 , further comprising:
a control module configured to transition operating the engine between the high valve lift positive valve overlap state and the low valve lift negative valve overlap state when the intake and exhaust camshafts are at the identical predetermined intake and exhaust camshaft angles.