Coordination of vehicle actuators during firing fraction transitions

Patent metadata

Field	Value
Publication number	US-10094313-B2
Application number	US-201815902685-A
Country	US
Kind code	B2
Filing date	Feb 22, 2018
Priority date	Jun 23, 2016
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

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.

First claim

The invention claimed is:

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 a course of the transitions, 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. The 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. The 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. The 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. The 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. The 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. The 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. The method as recited in claim 3 wherein each selected next effective firing fraction is the next lower effective firing fraction candidate.

9. The 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. The 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. The 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, an effective firing fraction immediately begins transitioning to the new requested effective firing fraction.

12. The 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. The 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. The method as recited in claim 1 wherein the target effective firing fraction is a lesser fraction than the first effective firing fraction.

15. The 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 a

Assignees

• Tula Technology Inc
• Gm Global Tech Operations Llc

Inventors

• Serrano Louis J
• Carlson Steven E
• Haase Steven J
• Dibble Donavan L
• Rayl Allen B

Classifications

• B60W10/06

  including control of combustion engines · CPC title

• F02D37/02

  one of the functions being ignition · CPC title

• F02D41/0215

  in relation with elements of the transmission · CPC title

• B60W10/023

  Fluid clutches · CPC title

• F02D41/0087 Primary

  Selective cylinder activation, i.e. partial cylinder operation (deceleration cut-off F02D41/123) · CPC title