Knock mitigation and cylinder balancing in an internal combustion engine
An engine control system comprises a balancing arrangement together with a knock mitigation controller configured to implement a knock mitigation procedure wherein an offset input value (V I ) is applied to the balancing algorithm. The offset input value (V I ) may cause the balancing algorithm to adjust the control output (O 1 ) for the respective one of the combustion chambers to progressively vary the fuel supply or ignition timing for the affected cylinder to mitigate the knock condition. Alternatively, the controller may generate an offset output value (V O ) to more rapidly vary the fuel supply or ignition timing, with the offset input value (V I ) being selected for example to compensate for the resulting change in the control input (I 1 ) from the cylinder to the balancing algorithm, or to provide additional, more gradual adjustment to further mitigate the knock condition.
1. An engine control system for controlling the operation of an internal combustion engine, the engine comprising a plurality of combustion chambers,
each combustion chamber comprising a respective one of a plurality of moving elements, the moving elements being operatively connected to an output shaft and moveable to drive the output shaft in rotation;
the control system including:
a fuel supply and ignition system,
a controller, and
a sensing arrangement;
the fuel supply and ignition system being arranged to supply a variable charge of fuel and air to each combustion chamber, and to control ignition of the fuel in each combustion chamber at a timing relative to the movement of the respective moving element;
the sensing arrangement being arranged to sense for each combustion chamber at least one operational parameter, the at least one operational parameter including at least an internal pressure of the combustion chamber, and to generate for each combustion chamber a control input (I 1 ) representing the sensed at least one operational parameter;
the controller being configured to receive the control input for each combustion chamber and to generate a control output (O, O 1 , O 2 ) for each combustion chamber;
the fuel supply and ignition system being controllable by the control output (O 1 , O 2 ) from the controller for each combustion chamber to vary at least one of the charge and the timing for the respective combustion chamber;
the controller including a balancing arrangement, the balancing arrangement configured to iteratively adjust each of the control outputs (O 1 ) responsive to the control inputs (I 1 ) according to a balancing algorithm to obtain a balanced condition, the balanced condition being a predefined relationship between the control inputs (I 1 ) for all of the combustion chambers;
the controller being further configured:
to identify, based on the control inputs (I 1 ), a knock condition in a respective one of the combustion chambers, and,
responsive at least to identifying the knock condition, to implement a knock mitigation procedure wherein:
an offset input value (VI) is applied to the balancing algorithm, and the control output (O 1 , O 2 ) for the respective one of the combustion chambers is adjusted to mitigate the knock condition,
the adjustment to the control output (O 1 , O 2 ) for the respective combustion chamber comprises a first, relatively rapid adjustment and a second, relatively more gradual adjustment; and
the first adjustment is not performed by the balancing algorithm; and
the second adjustment is performed by the balancing algorithm responsive to the offset input value (VI).
2. An engine control system according to claim 1 , wherein the adjustment to the control output (O 1 , O 2 ) for the respective combustion chamber is performed by the balancing algorithm responsive to the offset input value (VI).
3. An engine control system according to claim 1 , wherein the control inputs (I 1 ) are supplied to the balancing algorithm, and the offset input value (VI) is applied to the respective control input (I 1 ) for the respective combustion chamber.
4. An engine control system according to claim 1 , wherein the controller is further configured, after applying the offset input value (VI) to the balancing algorithm, to reduce progressively the offset input value (VI) to the balancing algorithm.
5. An engine control system according to claim 1 wherein the controller is configured to adjust the control output (O 1 , O 2 ) to vary both the charge and the timing for the respective combustion chamber to mitigate the knock condition.
6. An engine control system according to claim 5 , wherein the controller is configured:
to adjust the control output (O 1 , O 2 ) to change the timing for the respective combustion chamber rapidly from a first value to a second value, and then more slowly to return the timing from the second value towards the first value; and
to adjust the control output ( 01 , 02 ) to reduce a quantity of the fuel in the charge for the respective combustion chamber rapidly from a first fuel quantity to a second fuel quantity, and then more slowly to increase the quantity of the fuel progressively from the second fuel quantity towards the first fuel quantity.
7. A method for controlling an internal combustion engine, the engine comprising:
a plurality of combustion chambers,
a fuel supply and ignition system,
a controller, and
a sensing arrangement;
each combustion chamber comprising a respective one of a plurality of moving elements, the moving elements being operatively connected to an output shaft and moveable to drive the output shaft in rotation;
the fuel supply and ignition system being arranged to supply a variable charge of fuel and air to each combustion chamber, and to control ignition of the fuel in each combustion chamber at a timing relative to the movement of the respective moving element;
the sensing arrangement being arranged to sense for each combustion chamber at least one operational parameter, the at least one operational parameter including at least an internal pressure of the combustion chamber, and to generate for each combustion chamber a control input (I 1 ) representing the sensed at least one operational parameter;
the controller being configured to receive the control input (I 1 ) for each combustion chamber and to generate a control output (O, O 1 , O 2 ) for each combustion chamber;
the fuel supply and ignition system being controllable by the control output (O 1 , O 2 ) from the controller for each combustion chamber to vary at least one of the charge and the timing for the respective combustion chamber;
the controller including a balancing arrangement, the balancing arrangement configured to iteratively adjust each of the control outputs (O 1 ) responsive to the control inputs (I 1 ) according to a balancing algorithm to obtain a balanced condition, the balanced condition being a predefined relationship between the control inputs for all of the combustion chambers;
the method comprising:
identifying, by the controller, based on the control inputs (I 1 ), a knock condition in a respective one of the combustion chambers, and
responsive to identifying the knock condition, implementing, by the controller, a knock mitigation procedure wherein:
an offset input value (VI) is applied to the balancing algorithm, and the control output (O 1 , O 2 ) for the respective one of the combustion chambers is adjusted to mitigate the knock condition,
the adjustment to the control output (O 1 , O 2 ) for the respective combustion chamber comprises a first, relatively rapid adjustment and a second, relatively more gradual adjustment; and
the first adjustment is not performed by the balancing algorithm; and
the second adjustment is performed by the balancing algorithm responsive to the offset input value (VI).