MANAGING SKIP FIRE PHASE TRANSITIONS

• US 20180112609A1
• Filed: 10/20/2016
• Published: 04/26/2018
• Est. Priority Date: 10/20/2016
• Status: Active Grant

• Current Assignee: Tula Technology, Incorporated (BorgWarner Incorporated)
• Original Assignee: Tula Technology, Incorporated (BorgWarner Incorporated)
• Inventors: SERRANO, Louis J.
• Granted Patent: US 10,161,328 B2
• Time in Patent Office: Days
• CPC Class Codes: F02D 17/00 Controlling engines by cutting out individual cylinders; Rendering engines inoperative or idling controlling or rendering inoperative by varying inlet or exhaust valve operating characteristics F02D13/00
• CPC Class Codes: F02D 17/02 Cutting-out cutting-out engines in multiple engine arrangements F02D25/04
• CPC Class Codes: F02D 2200/1002 Output torque
• CPC Class Codes: F02D 2250/18 Control of the engine output torque
• CPC Class Codes: F02D 2250/21 during a transition between engine operation modes or states
• CPC Class Codes: F02D 41/0085 Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/3058 the engine working with a variable number of cycles

Abstract

Methods and controllers for dynamically altering the phase of a firing sequence during operation of an engine are described. The described methods and controllers are particularly useful in conjunction with dynamic skip fire operation of the engine.

Claims

1. A method of altering the phase of a firing sequence during operation of an engine having a plurality of working chambers at a first firing fraction that is less than one, the method comprising:

(a) determining whether a selected working chamber firing decision is consistent with a firing decision that would be made when the firing sequence is in a desired phase; and

(b) when it is determined that the selected working chamber firing decision is not consistent with the firing decision that would be made when the firing sequence is in the desired phase, at least sometimes, adjusting the phase of the firing sequence; and

(c) repeating steps (a) and (b) as necessary at least until the desired phase is attained; and

whereby the phase of the firing sequence is altered from a first phase to the desired phase.

2. A method as recited in claim 1 wherein the working chamber skip/fire determinations are made using a first order sigma delta converter during operation of the engine at the first firing fraction.

3. A method as recited in claim 2 wherein the firing sequence phase adjustment is accomplished by adding an offset value to an accumulator in the sigma delta converter.

4. A method as recited in claim 3 wherein an absolute value of the offset value is a fraction equal to the reciprocal of the denominator of the first firing fraction.

5. A method as recited in claim 3 wherein an absolute value of the offset value is a fraction less than the reciprocal of the denominator of the first firing fraction.

6. A method as recited in claim 3 wherein an absolute value of the offset value is a reciprocal of a number of working chambers that the engine has.

7. A method as recited in claim 1 wherein the working chambers have a set firing opportunity order and firing sequence phase adjustments are not made during any working cycle that immediately follows a fired working cycle in the preceding working chamber in the working chamber firing opportunity order.

8. A method as recited in claim 1 wherein firing sequence phase adjustments are not made during any working cycle that immediately follows a working cycle in which a firing sequence phase adjustment was made.

9. A method as recited in claim 2 the firing sequence phase adjustment is accomplished by running one or more phantom cycles of the sigma delta converter.

10. A method as recited in claim 3 wherein the offset value is a negative value.

11. A skip fire engine controller configured to perform the method of claim 1.

12. A method of operating an engine having a plurality of working chambers, the method comprising:

operating an engine in a skip fire mode at a first firing fraction, wherein skip/fire determinations are made using a first order sigma delta converter during operation of the engine in the skip fire mode at the first firing fraction;

transitioning to operating the engine at a second firing fraction that has a corresponding second firing sequence that repeats each engine cycle, wherein the second firing fraction is entered at a first phase that corresponds to firing a first set of the working chambers and not firing the remaining working chambers each engine cycle; and

altering the phase of the second firing sequence to a desired second phase to thereby cause a second set of the working chambers to fire each engine cycle during operation at the second firing fraction, the second set of cylinders being different than the first set of working chambers.

13. A method as recited in claim 12 wherein the first firing fraction has an ergodic skip fire firing sequence.

14. A method as recited in claim 12 wherein the second firing fraction is a simple fraction having a denominator that is a factor of the number of working chambers that the engine has.

15. A method as recited in claim 12 wherein:

the first order sigma delta converter includes an accumulator that tracks the portion of a firing that has been requested but not delivered, or delivered but not requested; and

the phase of the second firing sequence is altered by adding an offset value to the accumulator.

16. A method as recited in claim 12 wherein the phase of the second firing sequence is altered by running at least one phantom cycle of the sigma delta converter to thereby cause the generation of a firing decision output that does not influence the firing decision associated with any working chamber working cycle.

17. A method as recited in claim 16 comprising running a plurality of the phantom cycles of the sigma delta converter, wherein the plurality of phantom cycles of the sigma delta conversion immediately follow one another until a desired phase for the second firing sequence is attained.

18. A method as recited in claim 15 wherein an absolute value of the offset value is a fraction that is the reciprocal the denominator of the second firing fraction.

19. A method as recited in claim 15 wherein an absolute value of the offset value is less than the fraction that is the reciprocal the denominator of the second firing fraction.

20. A method as recited in claim 15 further comprising, after operation at the second firing fraction at the altered phase, transitioning to a third firing fraction that is different that the second firing fraction;

and wherein no offset values are added to or subtracted from the accumulator in conjunction with the transition to the third firing fraction.

21. A skip fire engine controller configured to perform the method of claim 12.