FIRING FRACTION MANAGEMENT IN SKIP FIRE ENGINE CONTROL
First Claim
1. A engine controller suitable for directing operation of an engine in a skip fire manner, the engine controller comprising:
- a firing fraction determining unit arranged to determine an operational firing fraction and associated engine settings for delivering a desired engine output, wherein the firing fraction determining unit is arranged to select the firing fraction from a set of available firing fractions; and
a firing controller arranged to direct firings in a skip fire manner that delivers the selected operational firing fraction, wherein the firing controller includes an accumulator that helps smooth transitions between different firing fractions; and
wherein all of the firing fractions in the set of available firing fractions other than a firing fraction of one, are simple fractions having an integer denominator of no more than 15.
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Accused Products
Abstract
In various described embodiments skip fire control is used to deliver a desired engine output. A controller determines a skip fire firing fraction and (as appropriate) associated engine settings that are suitable for delivering a requested output. In one aspect, the skip fire controller is arranged to select a base firing fraction that has a repeating firing cycle length that will repeat at least a designated number of times per second at the current engine speed. Such an arrangement can be helpful in reducing the occurrence of undesirable vibrations.
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Citations
32 Claims
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1. A engine controller suitable for directing operation of an engine in a skip fire manner, the engine controller comprising:
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a firing fraction determining unit arranged to determine an operational firing fraction and associated engine settings for delivering a desired engine output, wherein the firing fraction determining unit is arranged to select the firing fraction from a set of available firing fractions; and a firing controller arranged to direct firings in a skip fire manner that delivers the selected operational firing fraction, wherein the firing controller includes an accumulator that helps smooth transitions between different firing fractions; and wherein all of the firing fractions in the set of available firing fractions other than a firing fraction of one, are simple fractions having an integer denominator of no more than 15. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A engine controller suitable for directing operation of an engine in a skip fire manner, the engine controller comprising:
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a firing fraction determining unit arranged to determine a desired operational firing fraction, wherein the firing fraction determining unit is arranged to select the desired operational firing fraction from a set of available firing fractions; a firing controller arranged to receive a commanded firing fraction and to direct firings in a skip fire manner that delivers the commanded firing fraction; and a transition unit that receives the desired operational firing fraction from the firing fraction determining unit and outputs the commanded firing fraction to the firing controller, wherein the transition unit is arranged to spread changes in the desired operational firing fraction over multiple firing opportunities, whereby during transition, the input to the firing fraction controller may have a value that is different than any of the predetermined set of firing fractions. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A engine controller suitable for directing operation of an engine having a plurality of working chambers in a skip fire manner, the engine controller comprising:
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a firing fraction determining unit arranged to determine an operational firing fraction and associated engine settings for delivering a desired engine output, wherein the firing fraction determining unit is arranged to select the firing fraction from a set of available firing fractions, and wherein at least one of the available firing fractions is a variable displacement firing fraction equivalent to simple fraction having a denominator equal to the number of working chambers in the engine and at least another one of the available firing fractions does not have any equivalent simple fraction having a denominator equal to the number of working chambers; and a firing controller arranged to (i) sometimes direct firings in variable displacement mode in which a first fixed subset of the available working chambers are always fired each engine cycle and all other of the available working chambers are always skipped each engine cycle while operating in the variable displacement mode, and (ii) sometimes direct firings in a skip fire mode in which selected cylinders are sometimes skipped and sometimes fired while operating in the skip fire mode; and wherein the firing controller includes an accumulator that helps smooth transitions between different firing fractions.
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20. A engine controller suitable for directing operation of an engine in a skip fire manner, the engine controller comprising:
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a firing fraction determining unit arranged to determine an operational firing fraction and associated engine settings for delivering a desired engine output, wherein the firing fraction determining unit is arranged to select the firing fraction from a set of available firing fractions; a firing controller arranged to direct firings in a skip fire manner that delivers the selected operational firing fraction; and wherein the firing fraction determining unit is arranged to update the operational firing fraction on a working cycle by working cycle basis and the firing controller is arranged to make firing decisions on a working cycle by working cycle basis. - View Dependent Claims (21)
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22. A method of managing transitions between firing fractions during skip fire operation of an engine using a firing controller arranged to direct firings in a skip fire manner that delivers the operational firing fraction selected from a set of available firing fractions, t commanded firing fractions, the method comprising:
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while the engine is operating in a skip fire manner at a first firing fraction selected from the available set of firing fractions, determining a desired second operational firing fraction from the set of available firing fractions that is different than the first firing fraction; tracking a portion of a firing that has been requested but not yet directed by the firing controller, directing the firing controller to change from the first firing fraction to the second firing fraction, wherein a value stored in the accumulator affects a phase at which the second firing fraction is entered. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 32)
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31. A method of managing transitions between firing fractions during skip fire operation of an engine using a firing controller arranged to direct firings in a skip fire manner that delivers the operational firing fraction, the firing controller being arranged to track a portion of a firing that has been requested but not yet directed by the firing controller to thereby help manage transitions between different commanded firing fractions, the method comprising:
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while the engine is operating in a skip fire manner at a first firing fraction, determining a desired second operational firing fraction that is different than the first firing fraction; directing the firing controller to change from the first firing fraction to the second firing fraction, wherein the command to change from the first firing fraction to the second firing fraction is spread over multiple firing opportunities; and wherein all of the firing fractions in the set of available firing fractions other than a firing fraction of one are simple fractions and none of the firing fractions in the set of available firing fractions has a denominator greater than 15.
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Specification