COORDINATION OF VEHICLE ACTUATORS DURING FIRING FRACTION TRANSITIONS

• US 20180179970A1
• Filed: 02/22/2018
• Published: 06/28/2018
• Est. Priority Date: 06/23/2016
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company), Tula Technology, Incorporated
• Original Assignee: GM Global Technology Operations LLC (General Motors Company), Tula Technology, Incorporated
• Inventors: SERRANO, Louis J., CARLSON, Steven E., HAASE, Steven J., DIBBLE, Donavan L., RAYL, Allen B.
• Granted Patent: US 10,094,313 B2
• Time in Patent Office: Days
• CPC Class Codes: B60W 10/023 Fluid clutches
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 2710/025 Clutch slip, i.e. difference between input and output speeds
• CPC Class Codes: B60W 30/1886 Controlling power supply to auxiliary devices
• CPC Class Codes: F02D 17/026 delivering compressed fluid, e.g. air, reformed gas, to the active cylinders other than during starting
• CPC Class Codes: F02D 2041/001 for engines with variable valve actuation
• CPC Class Codes: F02D 2250/21 during a transition between engine operation modes or states
• CPC Class Codes: F02D 37/02 one of the functions being ignition
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/0215 in relation with elements of the transmission
• CPC Class Codes: F02P 5/045 combined with electronic control of other engine functions, e.g. fuel injection in general F02D37/02
• 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

A variety of methods and arrangements are described for controlling transitions between firing fractions during skip fire or other dynamic firing level modulation operation of an engine. In general, actuator first transition strategies are described in which an actuator position (e.g., cam phase, TCC slip, etc.) is changed to, or close to a target position before a corresponding firing fraction change is implemented. When the actuator change associated with a desired firing fraction change is relatively large, the firing fraction change is divided into a series of two or more firing fraction change steps. A number of intermediate target selection schemes are described as well.

Claims

1. A method of controlling an engine to deliver a requested engine output, the method comprising:

(a) while the engine is operating at a first effective firing fraction and an associated first cam phase, determining a requested effective firing fraction that is different than the first effective firing fraction, the requested effective firing fraction being a second effective firing fraction having an associated second cam phase, the second cam phase being different than the first cam phase;

(b) selecting an intermediate effective firing fraction that is between the first and second effective firing fractions, the intermediate effective firing fraction having an associated intermediate cam phase;

(c) identifying the selected intermediate effective firing fraction as a target effective firing fraction and the intermediate cam phase as a target cam phase;

(d) initiating a transition from the first cam phase to one of the second cam phase or the target cam phase;

(e) after an actual cam phase is at or within a predetermined range of the target cam phase transitioning to the target effective firing fraction;

(f) when the target effective firing fraction is not the second effective firing fraction, selecting a next effective firing fraction having an associated next cam phase and setting the target effective firing fraction to be the next effective firing fraction and setting the target cam phase to be the next cam phase and causing the cam phase to transition towards the next cam phase or to transition towards or to continue transitioning towards the second cam phase; and

(g) iteratively repeating (e) and (f) until the requested effective firing fraction is reached; and

(h) directing operation of the engine during the transitions to deliver the requested engine output, whereby an actual commanded effective firing fraction changes over the course of the transition, and

wherein operating the engine at at least one of the first, second and intermediate effective firing fractions involves operating the engine in a multi-level skip fire or multi-charge level operating mode.

2. A method as recited in claim 1 wherein when the first effective firing fraction is greater than one half and the target effective firing fraction is less than one half, the intermediate effective firing fraction is one half.

3. A method as recited in claim 1 wherein:

an engine controller that directs the effective firing fraction transitions has a defined set of potential operational effective firing fractions;

at various particular operating conditions, only an associated subset of the potential operational effective firing fractions are designated as candidates for use;

the effective firing fraction candidates for use do not always include all potential operational effective firing fractions that are capable of delivering the requested engine output; and

each target effective firing fraction is selected from the effective firing fraction candidates for use at current operating conditions.

4. A method as recited in claim 3 wherein the intermediate effective firing fraction is determined by selecting the lowest effective firing fraction candidate that has an associated cam phase within a predefined range of the first cam phase at the current operating conditions.

5. A method as recited in claim 3 wherein the next effective firing fraction is determined by selecting the lowest effective firing fraction candidate that has an associated cam phase within a predefined range of the previous target cam phase.

6. A method as recited in claim 5 wherein the predefined range of the target cam phase is no more than about ±

3 degrees of crank shaft angle at the current operating conditions.

7. A method as recited in claim 3 wherein each selected next effective firing fraction is the lowest effective firing fraction candidate that has an associated cam phase within the predefined range of the immediately preceding target effective firing fraction, or the next lower effective firing fraction candidate when no lower effective firing fraction candidate has an associated cam phase within the predefined range.

8. A method as recited in claim 3 wherein each selected next effective firing fraction is the next lower effective firing fraction candidate.

9. A method as recited in claim 3 wherein:

when at least one of the effective firing fraction candidates that is lower than the first effective firing fraction has an associated cam phase within a predefined range of the first cam phase at the current operating conditions, the intermediate effective firing fraction is the lowest effective firing fraction candidate that has an associated cam phase within the predefined range; and

when no lower effective firing fraction candidate has an associated cam phase within the predefined range, the intermediate effective firing fraction is either a predefined effective firing fraction or the next lower effective firing fraction candidate.

10. A method as recited in claim 1 wherein during each effective firing fraction transition, a commanded effective firing fraction and a commanded intake manifold pressure are changed during the transition in a manner that helps provide the desired engine output throughout the transition.

11. A method as recited in claim 1 wherein when the requested effective firing fraction changes during a transition to a new requested effective firing fraction that is higher than a then current effective firing fraction, a effective firing fraction immediately begins transitioning to the new requested effective firing fraction.

12. A method as recited in claim 1 wherein when the requested effective firing fraction changes during a transition to a new requested effective firing fraction that is lower than a then current effective firing fraction, the transition continues according to the method of claim 1 to the new requested effective firing fraction and a new second cam phase associated with the new requested effective firing fraction.

13. A method as recited in claim 1 wherein:

an engine controller that directs the effective firing fraction transitions has a defined set of effective firing fraction candidates;

each target effective firing fraction is selected from the effective firing fraction candidates for use at current operating conditions.

14. A method as recited in claim 1 wherein the target effective firing fraction is a lower fraction than the first effective firing fraction.

15. A method as recited in claim 1 wherein the set of available effective firing fractions only includes one and fractions having a denominator that is not greater than nine.

16. A method of controlling an engine to deliver a requested engine output, the method comprising:

while the engine is operating at a first effective firing fraction having an associated first cam phase, determining a desired second effective firing fraction and an associated second cam phase, the second cam phase being different than the first cam phase;

initiating a transition from the first cam phase to the second cam phase;

after an actual cam phase is at or within a predetermined range of the second cam phase transitioning to the second effective firing fraction, wherein transition to the second effective firing fraction is initiated only after the actual cam phase is at or within the predetermined range of the second cam phase; and

directing operation of the engine during the transitions to deliver the requested engine output, whereby an actual commanded effective firing fraction gradually changes over the course of the transition from the first effective firing fraction to the second effective firing fraction, and

wherein operating the engine at at least one of the first and second effective firing fractions involves operating the engine in a multi-level skip fire or multi-charge level operating mode.

17. An engine controller arranged to direct dynamic firing level modulation operation of an engine, the engine controller being configured to:

(a) direct operation of the engine at a first effective firing fraction and a first cam phase;

(b) while the engine is operating at the first effective firing fraction and the first cam phase, determine a requested effective firing fraction that is different than the first effective firing fraction, the requested effective firing fraction being a second effective firing fraction having an associated second cam phase, the second cam phase being different than the first cam phase;

(c) select an intermediate effective firing fraction that is between the first and second effective firing fractions, the intermediate effective firing fraction having an associated intermediate cam phase;

(d) identify the selected intermediate effective firing fraction as a target effective firing fraction and the intermediate cam phase as a target cam phase;

(e) initiate a transition from the first cam phase to one of the second cam phase or the target cam phase;

(f) after an actual cam phase is at or within a predetermined range of the target cam phase transition to the target effective firing fraction;

(g) when the target effective firing fraction is not the second effective firing fraction, select a next effective firing fraction having an associated next cam phase and set the target effective firing fraction to be the next effective firing fraction and set the target cam phase to be the next cam phase and cause the cam phase to transition towards the next cam phase or to transition towards or continue transitioning towards the second cam phase; and

(h) iteratively repeat (f) and (g) until the second cam phase and second effective firing fraction are reached; and

(i) direct operation of the engine during the transitions to deliver the requested engine output, whereby an actual commanded effective firing fraction changes over the course of the transition, and

wherein operating the engine at at least one of the first, second and intermediate effective firing fractions involves operating the engine in a multi-level skip fire or multi-charge level operating mode.

18. An engine controller as recited in claim 17, wherein the engine controller has a defined set of potential operational effective firing fractions;

at various particular operating conditions, only an associated subset of the potential operational effective firing fractions are designated as candidates for use;

the effective firing fraction candidates for use do not always include all potential operational effective firing fractions that are capable of delivering the requested engine output; and

each target effective firing fraction is selected from the effective firing fraction candidates for use at current operating conditions.

19. An engine controller as recited in claim 18 wherein the intermediate effective firing fraction is determined by selecting the lowest effective firing fraction candidate that has an associated cam phase within a predefined range of the first cam phase at the current operating conditions.

20. An engine controller as recited in claim 18 wherein the next effective firing fraction is determined by selecting the lowest effective firing fraction candidate that has an associated cam phase within a predefined range of the previous target cam phase.

21. An engine controller as recited in claim 20 wherein the predefined range of the target cam phase is no more than about ±

3 degrees of crank shaft angle at the current operating conditions.

22. An engine controller as recited in claim 18 wherein each selected next effective firing fraction is the lowest effective firing fraction candidate that has an associated cam phase within the predefined range of the immediately preceding target effective firing fraction, or the next lower effective firing fraction candidate when no lower effective firing fraction candidate has an associated cam phase within the predefined range.

23. An engine controller as recited in claim 18 wherein each selected next effective firing fraction is the next lower effective firing fraction candidate.

24. An engine controller as recited in claim 18 wherein:

when at least one of the effective firing fraction candidates that is lower than the first effective firing fraction has an associated cam phase within a predefined range of the first cam phase at the current operating conditions, the intermediate effective firing fraction is the lowest effective firing fraction candidate that has an associated cam phase within the predefined range; and

when no lower effective firing fraction candidate has an associated cam phase within the predefined range, the intermediate effective firing fraction is either a predefined effective firing fraction or the next lower effective firing fraction candidate.

25. An engine controller as recited in claim 17 wherein when the first effective firing fraction is greater than one half and the target effective firing fraction is less than one half, the intermediate effective firing fraction is one half.

26. An engine controller as recited in claim 17 further configured to handle changes in the requested effective firing fraction that occur during a transition by:

when the requested effective firing fraction changes during a transition to a new requested effective firing fraction that is higher than a then current effective firing fraction, immediately begin transitioning to the new requested effective firing fraction; and

when the requested effective firing fraction changes during a transition to a new requested effective firing fraction that is lower than the then current effective firing fraction, the transition continues to the new requested effective firing fraction and a new second cam phase associated with the new requested effective firing fraction.

27. An engine controller as recited in claim 17 wherein during each effective firing fraction transition, a commanded effective firing fraction and a commanded intake manifold pressure are changed during the transition in a manner that helps provide the desired engine output throughout the transition.

28. An engine controller as recited in claim 17 wherein:

the engine controller has a defined set of effective firing fraction candidates;

each target effective firing fraction is selected from the effective firing fraction candidates for use at current operating conditions.

29. An engine controller as recited in claim 17 wherein the set of available effective firing fractions only includes one and fractions having a denominator that is not greater than nine.

30. An engine controller arranged to direct dynamic firing level modulation operation of an engine, the engine controller being configured to:

direct operation of the engine at a first effective firing fraction and a first cam phase;

while the engine is operating at the first effective firing fraction and the first cam phase, determine a desired second effective firing fraction and an associated second cam phase, the second cam phase being different than the first cam phase;

initiate a transition from the first cam phase to the second cam phase;

after an actual cam phase is at or within a predetermined range of the second cam phase direct a transition to the second effective firing fraction, wherein the transition to the second effective firing fraction is initiated only after the actual cam phase is at or within the predetermined range of the second cam phase; and

direct operation of the engine during the cam phase and effective firing fraction transitions to deliver the requested engine output, whereby an actual commanded effective firing fraction changes over the course of the transition from the first effective firing fraction to the second effective firing fraction, and

wherein operating the engine at at least one of the first and second effective firing fractions involves operating the engine in a multi-level skip fire or multi-charge level operating mode.