Internal combustion engine control for improved fuel efficiency
A variety of methods and arrangements for improving the fuel efficiency of internal combustion engines are described. In some aspects, methods and arrangements are described for operating an engine in a throttled skip fire mode. In other aspects, methods and arrangements are described for controlling the operational state of a variable displacement engine.
1. An engine controller arranged to control working chamber firings in an engine, the engine controller comprising:
a working chamber output calculator arranged to determine a relative proportion of output delivered by each working chamber firing relative to a reference output;
a firing fraction calculator arranged to receiving a signal indicative of a desired output and to output a signal indicative of a desired firing fraction, wherein the desired firing fraction signal is based at least in part on results of the working chamber output calculator; and
a drive pulse generator arranged to receive the signal indicative of the desired firing fraction and output a drive pulse signal having a sequence of drive pulses that define a skip fire firing pattern that indicates when working chamber firings are appropriate to deliver the desired firing fraction.
2. An engine controller as recited in claim 1 wherein the reference output is indicative of one selected from the group consisting of:
a value that varies as a function of at least one current operating condition of the engine; and
a fixed output.
3. An engine controller as recited in claim 1 wherein the reference output is indicative of an output that would be provided by an optimized working chamber firing in the current operating conditions.
4. An engine controller as recited in claim 1 wherein:
the drive pulse generator uses feedback of the firings in the determination of the firing pattern; and
the feedback of the firings is derived from one of a requested firing, an instructed firing event, a calculated firing event, a detected firing event or a directed firing event.
5. An engine controller as recited in claim 1 wherein the drive pulse generator uses predictive adaptive control in the determination of the drive pulse signal.
6. An engine controller as recited in claim 1 wherein the firing fraction calculator updates the desired firing fraction at least once for every firing opportunity of the engine.
7. An engine controller as recited in claim 1 further comprising an engine settings controller arranged to set a throttle position based at least in part on the desired output.
8. An engine controller as recited in claim 7 wherein the engine settings controller is arranged to utilize a limited set of throttle positions when operating in a skip fire operational mode.
9. An engine controller as recited in claim 1 further comprising an engine settings controller arranged to set a throttle position, wherein the available throttle positions include partial throttle positions and whereby when a change in throttle position is made, the working chamber output calculator determines that a change has been made in the relative proportion of output delivered by each working chamber firing relative to a reference output and the firing fraction calculator is adjusted accordingly such that the desired output is delivered by firings directed by the drive pulse generator.
10. An engine controller as recited in claim 1 wherein the engine controller is not constrained to a limited set of throttle positions when operating in a skip fire operational mode.
11. A method of controlling the operation of an internal combustion engine having a plurality of working chambers, each working chamber being generally arranged to operate in a succession of working cycles, the method comprising:
receiving a signal indicative of a desired output;
determining an actual working chamber output fraction indicative of a relative proportion of output delivered by each working chamber firing relative to a reference output;
determining a desired firing fraction suitable for delivering the desired output operating based at least in part upon the actual working chamber output fraction; and
firing the working chambers in a skip fire firing pattern that is dynamically determined during operation of the engine that skips the firing of selected skipped working cycles and fires selected active working cycles, wherein the firing pattern is arranged to deliver the desired firing fraction.
12. A method as recited in claim 11 wherein the firing pattern is determined at least in part using predictive adaptive control that includes feedback indicative of working cycle firings.
13. A method as recited in claim 12 wherein the feedback of the firings is derived from one of a requested firing, an instructed firing event, a calculated firing event, a detected firing event or a directed firing event.
14. A method as recited in claim 11 wherein the desired firing fraction determining step is repeated substantially continuously and the firings are selected to provide the desired output.
15. A method as recited in claim 11 further comprising setting a throttle position based at least in part on the desired output.
16. A method as recited in claim 11 wherein the reference output is indicative of one selected from the group consisting of:
an amount of output that would be provided by an optimized working chamber firing in the current operating conditions; and
a set output.
17. A method as recited in claim 11 wherein the reference output varies as a function of at least one current operating condition.
18. A method as recited in claim 11 wherein the desired output signal is scaled based on the actual working chamber output fraction to thereby generate a desired firing fraction signal that is based at least in part on the scaled desired output signal.
19. A method as recited in claim 11 wherein a limited set of partial throttle settings are available, whereby when a change in throttle position is made, the working chamber output calculation determines that a change has been made in the relative proportion of output delivered by each working chamber firing relative to the reference output and the firing fraction is adjusted accordingly such that the desired output is delivered by the directed firings directed.
20. A method of controlling the operation of an internal combustion engine having a plurality of working chambers, each working chamber being generally arranged to operate in a succession of working cycles, the method comprising:
receiving a signal indicative of a desired output;
setting a throttle position based at least in part on the desired output;
determining a desired firing fraction suitable for delivering the desired output operating based on current engine operating conditions; and
firing the working chambers in a skip fire firing pattern that is dynamically determined during operation of the engine that skips the firing of selected skipped working cycles and fires selected active working cycles, wherein the firing pattern is arranged to deliver the desired firing fraction.
21. A method as recited in claim 20 wherein the firing pattern is determined at least in part using predictive adaptive control that includes feedback indicative of working cycle firings.
22. A method as recited in claim 21 wherein the feedback of the firings is derived from one of a requested firing, an instructed firing, a calculated firing, a detected firing event or a directed firing.
23. A method as recited in claim 20 wherein the firing fraction determining step is repeated substantially continuously and the firings are selected to provide the desired output.
24. A method as recited in claim 20 further comprising determining an actual working chamber output fraction indicative of a relative proportion of output delivered by each working chamber firing relative to a reference output.
25. A method as recited in claim 24 wherein the desired output signal is scaled based on the actual working chamber output fraction and the desired firing fraction is based at least in part on the scaled desired output signal.
26. A method as recited in claim 24 wherein a limited set of partial throttle settings are available, whereby when a change in throttle position is made, the working chamber output calculation determines that a change has been made in the relative proportion of output delivered by each working chamber firing relative to the reference output and the firing fraction is adjusted accordingly such that the desired output is delivered by the directed firings directed.
27. A method as recited in claim 20 wherein the reference output is indicative of one selected from the group consisting of:
a value that varies as a function of at least one current operating condition of the engine; and
a fixed output.
28. A method as recited in claim 20 wherein the reference output is indicative of an output that would be provided by an optimized working chamber firing in the current operating conditions.