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Firing fraction management in skip fire engine control

  • US 9,528,446 B2
  • Filed: 10/17/2012
  • Issued: 12/27/2016
  • Est. Priority Date: 10/17/2011
  • Status: Active Grant
First Claim
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1. A skip fire engine controller for determining which working cycles to skip and which working cycles to fire during skip fire operation of an internal combustion engine having a plurality of working chambers, the skip fire engine controller comprising:

  • a firing fraction determining unit arranged to determine a firing fraction suitable for delivering a desired engine output, wherein the firing fraction determining unit is arranged and constrained to determine an operational firing fraction that has an associated repeating firing cycle length that is assured to repeat at least a designated number of times per second at the current engine speed; and

    a firing controller arranged to direct firings in a skip fire manner that delivers the operational firing fraction, the firing controller being arranged to make firing decisions on a firing opportunity by firing opportunity basis; and

    wherein the firing controller includes an accumulator that tracks a relative portion of a firing that has been requested but not yet directed by the firing controller, whereby the accumulator helps smooth transitions between different firing fractions.

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