Skip fire transition control

• US 10,107,211 B2
• Filed: 07/11/2017
• Issued: 10/23/2018
• Est. Priority Date: 10/17/2011
• Status: Active Grant

• Current Assignee: Tula Technology, Incorporated
• Original Assignee: Tula Technology, Incorporated
• Inventors: Pirjaberi, Mohammad R., Serrano, Louis J., Yuan, Xin, Carlson, Steven E., Hashemi, Siamak, Kuhlenbeck, Ryan A.
• Primary Examiner(s): Moulis, Thomas
• Application Number:
  US15/646,476
• Publication Number:
  US 20170306864A1
• Time in Patent Office: 469 Days
• CPC Class Codes: F02D 17/02 Cutting-out cutting-out engines in multiple engine arrangements F02D25/04
• CPC Class Codes: F02D 2041/286 comprising means for signal processing
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/101 Engine speed
• CPC Class Codes: F02D 37/02 one of the functions being ignition
• CPC Class Codes: F02D 41/0002 Controlling intake air
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02P 5/1504 with particular means during a transient phase, e.g. acceleration, deceleration, gear change during starting F02P5/1506
• CPC Class Codes: Y02T 10/40 Engine management systems

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.

Claims

1. An engine controller comprising:

a firing fraction determining unit arranged to determine a desired operational firing fraction during operation of the engine; and

a transition adjustment unit arranged to manage transitions from a first firing fraction requested by the firing fraction determining unit to a target firing fraction requested by the firing fraction determining unit that is different from the first firing fraction, the transition adjustment unit being configured to gradually alter a commanded firing fraction from the first firing fraction to the target firing fraction, wherein the commanded firing fraction is altered each firing opportunity.

3. An engine controller as recited in claim 1 wherein:

the commanded firing faction has an associated skip fraction which is a complementary fraction of the commanded firing fraction; and

the transition adjustment unit is configured such that for a selected transition, the commanded firing fraction is altered in a manner such that a product of the skipping fraction and an intake manifold pressure remains substantially constant throughout the selected transition.

4. An engine controller as recited in claim 1 wherein the transition adjustment unit is configured such that for a selected transition, the firing fraction is changed at substantially the same rate throughout the transition.

5. An engine controller as recited in claim 1 further comprising a firing determining unit that includes an accumulator functionality that tracks a portion of a firing that has been requested, but not delivered, or that has been delivered, but not requested, and wherein the commanded firing fraction is provided to the firing determining unit.

6. An engine controller as recited in claim 1 wherein the transition adjustment unit is configured to change the commanded firing fraction each firing opportunity using a linear slew rate such that the amount that the commanded firing fraction is changed each firing opportunity is the same throughout the transition.

8. An engine controller as recited in claim 6 wherein the linear slew rate is in the range of 1-5% such that the commanded firing fraction increases in the range of 1 to 5 percent each firing opportunity.

9. An engine controller as recited in claim 6 wherein the magnitude of the linear slew rate is selected at least in part based on the magnitude of the change in firing fraction and at least one engine operating parameter.

10. An engine controller as recited in claim 1, wherein the transition period is in the range of 150 to 300 milliseconds.

11. An engine controller as recited in claim 1, wherein the engine includes a multiplicity of working chambers and an intake manifold that supplies air to at least a plurality of the working chambers, the intake manifold having a manifold air pressure, the engine controller being further configured to change a commanded throttle position in conjunction with the transition between different firing fractions to facilitate operation at the target 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.

12. An engine controller as recited in claim 1, wherein the engine includes a multiplicity of working chambers and an intake manifold that supplies air to at least a plurality of the working chambers, the engine controller being further configured to:

determine a target manifold pressure associated with the target firing fraction, the target manifold pressure being different than an initial manifold pressure that exists when a decision to change firing fractions is made; and

utilize feed forward throttle control in conjunction with the transition to accelerate the transition of the manifold pressure to the target manifold pressure.

13. An engine controller as recited in claim 1, wherein the engine includes a plurality of cylinders, a plurality of intake valves, each intake valve being associated with an associated one of the cylinders, a camshaft arranged to open and close the intake valves;

and an intake manifold that supplies air to the cylinders through the intake valves, the engine controller being further configured to;

determine a target air charge associated with the target firing fraction, the target air charge being different than an initial air charge that exists when a decision to change firing fractions is made; and

utilize feed forward camshaft control in conjunction with the transition to accelerate the transition of the air charge to the target air charge.

14. An engine controller as recited in claim 1, wherein the engine includes a multiplicity of working chambers, each working chamber having an associated spark source, the engine controller being further configured to:

determine a target spark timing associated with the target firing fraction, the target spark timing potentially being different than an initial spark timing that exists when a decision to change firing fractions is made; and

retard the spark relative to both the initial spark timing and the target spark timing for selected fired working chambers during the transition to mitigate or prevent a torque surge that would otherwise occur during the transition.

15. An engine controller as recited in claim 14 wherein at least one of the initial and target spark timings is a spark timing that causes the engine to generate the maximum brake torque at the associated engine settings.

16. An engine controller as recited in claim 1 wherein the engine includes an intake manifold, an exhaust and a multiplicity of working chambers, each working chamber being arranged to operate in a succession of working cycles, the engine controller being further configured to:

cause air to be pumped through the engine from the intake manifold to the exhaust during selected skipped working cycles that occur during the firing fraction transition to more quickly reduce manifold pressure during the transition; and

to generally not cause air to be pumped through the engine during skipped working cycles that occur outside the firing fraction transition.

17. An engine controller as recited in claim 1 further the engine controller being further configured to change at least one commanded engine operating parameter that affects a working chamber air charge in conjunction with the transition between different firing fractions to facilitate operation at the target firing fraction, wherein initiation of the altering of the commanded firing fraction is delayed relative to initiation of the change in the commanded engine operating parameter by a plurality of firing opportunity, thereby helping compensate for inherent delays associated with increasing or decreasing the amount of air in an intake manifold that provides air to the working chamber.

2. An engine controller comprising:

a firing fraction determining unit arranged to determine a desired operational firing fraction during operation of the engine; and

a transition adjustment unit arranged to manage transitions from a first firing fraction requested by the firing fraction determining unit to a target firing fraction requested by the firing fraction determining unit that is different from the first firing fraction, the transition adjustment unit being configured to alter a commanded firing fraction from the first firing fraction to the target firing fraction over a multiplicity of firing opportunities by altering the commanded firing fraction substantially the same amount each firing opportunity.

7. An engine controller as recited in claim 2 wherein the transition adjustment unit is configured to change the commanded firing fraction each firing opportunity using a linear slew rate such that the amount that the commanded firing fraction is changed each firing opportunity is the same throughout the transition.

18. An engine controller configured to control 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 engine controller being configured to:

direct operation of the engine in a skip fire manner during the transition; and

cause air to be pumped 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

to generally not cause air to be pumped through the engine during skipped working cycles that occur outside the firing fraction transition.

19. An engine controller configured to control 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 engine controller being configured to:

while directing operation of the engine at a first operational firing fraction, determine when it is desirable to transition to a target second operational firing fraction that is different than the first operational firing fraction;

direct a transition 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

direct a change in 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.

20. An engine controller as recited in claim 19 further configured to determine when a transition to a third operational firing fraction is desired before the transition to the target second operational firing fraction is completed, and in response to such determination:

change the commanded throttle position to a throttle position that facilitates operation at the third operational firing fraction;

continue to direct the transition towards the target second operational firing fraction during a designated delay period; and

after the designated delay period has expired, direct a transition from the then current firing fraction to the third operational firing fraction by gradually altering the commanded firing fraction from the then current operation firing fraction towards the third operation firing fraction.

21. An engine controller as recited in claim 20 wherein the designated delay period is a defined time period.

22. An engine controller as recited in claim 20 wherein the designated delay period is a defined number of firings or firing opportunities.

23. An engine controller as recited in claim 19 wherein the engine controller is configured to alter the commanded firing fraction each firing opportunity.

24. An engine controller as recited in claim 19 wherein the engine controller is configured to alter the commanded firing fraction by substantially the same amount each firing opportunity.