Skip fire transition control
First Claim
1. A method of controlling the transition of an engine between different firing fractions, the method comprising:
- while the engine is operating at a first firing fraction, determining a second target firing fraction that is different than the first firing fraction; and
transitioning from the first firing fraction to the target firing fraction by gradually altering a commanded firing fraction from the first firing fraction to the second firing fraction, wherein the commanded firing fraction is altered each firing opportunity.
1 Assignment
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Accused Products
Abstract
Methods and arrangements are described for controlling transitions between firing fractions during skip fire operation of an engine in order to help smooth the transitions. Generally, firing fractions transitions are implemented gradually, preferably in a manner that relatively closely tracks manifold filling dynamics. In some embodiments, the commanded firing fraction is altered each firing opportunity. Another approach contemplates altering the commanded firing fraction by substantially the same amount each firing opportunity for at least a portion of the transition. These approaches work particularly well when the commanded firing fraction is provided to a skip fire controller that includes an accumulator functionality that tracks the portion of a firing that has been requested, but not delivered, or vice versa. In various embodiments, commanded firing fraction changes are delayed relative to initiation of the change in throttle position to help compensate for inherent delays associated with changing the manifold air pressure.
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Citations
24 Claims
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1. A method of controlling the transition of an engine between different firing fractions, the method comprising:
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while the engine is operating at a first firing fraction, determining a second target firing fraction that is different than the first firing fraction; and transitioning from the first firing fraction to the target firing fraction by gradually altering a commanded firing fraction from the first firing fraction to the second firing fraction, wherein the commanded firing fraction is altered each firing opportunity. - View Dependent Claims (3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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2. A method of controlling the transition of an engine between different firing fractions, the method comprising:
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while the engine is operating at a first firing fraction, determining a second target firing fraction that is different than the first firing fraction; and transitioning from the first firing fraction to the target firing fraction by gradually altering a commanded firing fraction from the first firing fraction to the second firing fraction, wherein the commanded firing fraction is altered by substantially the same amount each firing opportunity. - View Dependent Claims (7)
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18. A method of controlling the transition of an engine from an initial firing fraction to a target firing fraction, there being an initial manifold pressure and a target manifold pressure, the target manifold pressure being lower than the initial manifold pressure and the target firing fraction being higher than the initial firing fraction, the method comprising:
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operating the engine in a skip fire manner during the transition; and pumping air through the engine from an intake manifold to an exhaust during selected skipped working cycles that occur during the transition to more quickly reduce intake manifold pressure to the target manifold pressure; and wherein air is generally not pumped through the engine during skipped working cycles that occur outside the firing fraction transition.
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19. A method of controlling the transition of an engine between different firing fractions, the engine including a multiplicity of working chambers, an intake manifold and an exhaust, the intake manifold having a manifold air pressure and being arranged to supply air to at least a plurality of the working chambers, the method comprising:
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while the engine is operating at a first operational firing fraction, receiving a request to transition to a target second operational firing fraction that is different than the first operational firing fraction; transitioning from the first operational firing fraction towards the target second operational firing fraction by gradually altering a commanded firing fraction from the first operational firing fraction towards the target second operational firing fraction; and changing a commanded throttle position in conjunction with the transition between the different firing fractions to facilitate operation at the target second operational firing fraction, wherein initiation of the altering of the commanded firing fraction is delayed relative to initiation of the change in throttle position by a plurality of firing opportunity, thereby helping compensate for inherent delays associated with changing the manifold air pressure. - View Dependent Claims (20, 21, 22, 23, 24)
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Specification