Method and code for controlling reactivation of deactivatable cylinder using torque error integration
In an internal combustion engine adapted to operate in a cylinder-deactivation mode, a method for controlling the reactivation of a deactivated cylinder includes determining a difference between a torque request from a vehicle operator, and an estimate of a maximum engine torque achievable in cylinder-deactivation mode based at least in part on a current engine speed. The difference is integrated over time to obtain a torque request “error.” A reactivation of the deactivated cylinder is triggered when the torque request error exceeds a first threshold value, which can be a calibrated value, a calibrated value adapted, for example, for driving style, or a value determined from a vehicle operating parameter such as vehicle speed. The use of the torque request error advantageously avoids reactivation of the deactivated cylinders in response to brief transients in the torque request signal that otherwise temporarily exceed the maximum achievable engine output torque.
1. A method for controlling a reactivation of a given deactivated cylinder of a multi-displacement internal combustion engine, the method comprising:
determining, while operating the engine in a partial-displacement mode characterized by deactivation of the given cylinder, a torque request based at least in part on a driver demand signal;
estimating a maximum potential output torque for the engine when operating in a partial-displacement mode based at least in part on a first engine operating parameter;
calculating a difference by which the torque request exceeds the maximum potential output torque;
integrating the calculated differences over time to obtain a torque request error measure; and
initiating a switch from the partial-displacement mode to a full-displacement mode characterized by activation of the deactivatable cylinder when the torque request error measure is not less than a first threshold value.
2. The method of claim 1 , wherein the first engine operating parameter is a current engine speed, and wherein estimating the maximum potential output torque includes retrieving a first value from a first lookup table containing a first plurality of maximum engine output torque values based on the current engine speed.
3. The method of claim 2 , wherein estimating the maximum potential output torque includes:
retrieving a second value from a second lookup table containing a second plurality of torque offset values based at least in part on the current engine speed, the torque offset values being representative of an NVH threshold for transitioning with no more than a negligible torque disturbance; and
summing the first value and the second value to obtain the maximum potential output torque.
4. The method of claim 3 , including retrieving the second value from the second lookup table based on a current vehicle speed.
5. The method of claim 1 , wherein the first threshold value is a calibratable value adapted based on an indication of a vehicle operator driving style.
6. The method of claim 1 , wherein the first threshold is determined based on a vehicle operating parameter.
7. The method of claim 6 , wherein the vehicle operating parameter is an indication of vehicle operator driving style.
8. The method of claim 6 , wherein the vehicle operating parameter is an operator-selectable indication of a desired vehicle fuel economy.
9. A computer-readable storage medium including computer executable code for controlling a reactivation of a given deactivated cylinder of a multi-displacement internal combustion engine, the storage medium including:
code for determining, while the engine is operating in a partial-displacement mode, a torque request based at least in part on a driver demand signal;
code for estimating a maximum potential output torque for the engine in the cylinder-deactivation mode based at least in part on a first engine operating parameter;
code for calculating a difference by which the torque request exceeds the maximum potential output torque;
code for integrating the calculated differences over time to obtain a torque request error measure; and
code for initiating a switch from the partial-displacement mode to a full-displacement mode characterized by activation of the deactivatable cylinder when the torque request error measure is not less than a first threshold value.
10. The method of claim 9 , wherein the code for estimating the maximum potential output torque includes code for retrieving a first value from a first lookup table containing a first plurality of maximum engine output torque values based on a current engine speed.
11. The storage medium of claim 10 , wherein the code for estimating the maximum potential output torque further includes:
code for retrieving a second value from a second lookup table containing a second plurality of torque offset values based at least in part on the current engine speed, the torque offset values being representative of an NVH threshold for transitioning with no more than a negligible torque disturbance; and
code for summing the first value and the second value to obtain the maximum potential output torque.
12. The storage medium of claim 11 , including retrieving the second value from the second lookup table based on a current vehicle speed.
13. The storage medium of claim 9 , including code for adapting the first threshold value based on an indication of a vehicle operator driving style.
14. The storage medium of claim 9 , including code for determining the first threshold based on one of a determined indication of vehicle operator driving style and an operator-selectable indication of a desired vehicle fuel economy.