Engine diagnostics with skip fire control

Patent metadata

Field	Value
Publication number	US-9581098-B2
Application number	US-201514939498-A
Country	US
Kind code	B2
Filing date	Nov 12, 2015
Priority date	Mar 15, 2013
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

Methods and devices are described for performing engine diagnostics during skip fire operation of an engine while a vehicle is being driven. Knowledge of the firing sequence is used to determine appropriate times to conduct selected diagnostics and/or to help better interpret sensor inputs or diagnostic results. In one aspect, selected diagnostics are executed when a single cylinder is fired a plurality of times in isolation relative to a sensor used in the diagnosis. In another aspect, selected diagnostics are conducted while the engine is operated using a firing sequence that insures that no cylinders in a first cylinder bank are fired for a plurality of engine cycles while cylinders in a second bank are at least sometimes fired. The described tests can be conducted opportunistically, when conditions are appropriate, or specific firing sequences can be commanded to achieve the desired isolation or skipping of one or more selected cylinders.

First claim

What is claimed is:

1. A method of operating an internal combustion engine having a plurality of cylinder banks, each bank including a plurality of cylinders, the method comprising:
operating the engine in a skip fire operational mode that utilizes most evenly spaced firings;
while operating in the skip fire operational mode, identifying a period in which a single one of the cylinders in a first cylinder bank is isolated as the only firing cylinder in the first cylinder bank; and
conducting a diagnosis of the isolated cylinder during the identified period, wherein the diagnosis conducted on the isolated cylinder is not conducted on the isolated cylinder when such cylinder is not isolated.

2. A method as recited in claim 1 wherein the period extends over a plurality of engine cycles and the isolated cylinder is fired a plurality of times in isolation relative to a sensor used in the diagnosis.

3. A method as recited in claim 2 wherein the engine diagnosis is a fuel trim diagnosis related to the isolated cylinder.

4. A method as recited in claim 2 wherein the engine diagnosis is a misfire diagnosis related to the isolated cylinder.

5. A method as recited in claim 1 wherein the selected engine diagnosis is conducted opportunistically when it is determined that a firing sequence or firing fraction used during normal skip fire operation of the engine opportunistically provides the conditions appropriate for conducting the diagnosis.

6. A method as recited in claim 1 further comprising checking to determine whether the diagnosis completes while the isolated cylinder is isolated, wherein the test is only considered valid when the diagnosis completes while the isolated cylinder remains isolated.

7. A method as recited in claim 1 further comprising directing the engine to utilize a designated firing sequence during skip fire operation to facilitate execution of the selected engine diagnosis at a time when the designated firing sequence would not otherwise be used to thereby provide conditions appropriate for conducting the diagnosis.

8. A method of managing fuel injector trim while a vehicle is being driven, the vehicle having an internal combustion engine having a multiplicity of cylinders, each cylinder having an associated fuel injector, the method comprising:
operating the engine in a skip fire operational mode during normal driving operation of the vehicle;
for each cylinder, conducting an individual cylinder fuel trim diagnosis for the injector associated with such cylinder during the skip fire operation of the engine; and
adjusting a fuel trim of at least one of the fuel injectors based of the individual cylinder fuel trim diagnoses.

9. A method as recited in claim 8 wherein the engine further comprises an oxygen sensor located in an exhaust path associated with a plurality of the cylinders.

10. A method as recited in claim 9 further comprising:
while operating in the skip fire operational mode, identifying a period in which a single one of the cylinders is isolated as the only firing cylinder associated with in the exhaust path; and
wherein the individual cylinder fuel trim diagnosis is performed on the isolated cylinder during the identified period.

11. A method as recited in claim 9 wherein the oxygen sensor is a lambda sensor.

12. A method as recited in claim 9 further comprising:
(a) during normal driving operation of the vehicle, directing operation of the engine at a firing fraction or firing sequence that causes a first one of the cylinders associated with the oxygen sensor to be isolated as the only cylinder associated with the oxygen sensor that is fired over the course of a plurality of engine cycles;
(b) wherein the individual cylinder fuel trim diagnosis for the fuel injector associated with the isolated cylinder is conducted during the isolation using the oxygen sensor;
repeating steps (a) and (b) for each of the cylinders associated with the oxygen sensor.

13. A method as recited in claim 12 wherein the firing fraction remains constant through a series of individual cylinder fuel trim diagnoses that test each of the cylinders associated with the oxygen sensor.

14. A method as recited in claim 13 wherein the different cylinders associated with the oxygen sensor are isolated by altering the phase of the firing sequence.

15. A method as recited in claim 9 wherein the individual cylinder fuel trim diagnosis is conducted when at least the following cylinder associated with the exhaust path is skipped.

16. A method of operating a vehicle having an internal combustion engine having a plurality of cylinder banks, each bank including a plurality of cylinders, the method comprising:
while the vehicle is being driven, operating the engine using a skip fire firing sequence that insures that no cylinders in a first cylinder bank are fired over a period of time that includes a plurality of engine cycles while cylinders in a second bank are at least sometimes fired; and
conducting a diagnosis of a component in an exhaust path associated with the first bank of cylinders, wherein at least a significant portion of the diagnosis is conducted while the cylinders in the first bank are not being fired.

17. A method as recited in claim 16 wherein the selected diagnosis evaluates a catalyst in an exhaust path associated with the first bank of cylinders.

18. A method as recited in claim 16 wherein the selected diagnosis evaluates a sensor in an exhaust path associated with the skipped bank of cylinders.

19. A method as recited in claim 16 wherein the selected engine diagnosis is conducted opportunistically when it is determined that a firing sequence or firing fraction used during normal skip fire operation of the engine opportunistically provides the conditions appropriate for conducting the diagnosis.

20. A method as recited in claim 16 further comprising directing the engine to utilize a designated firing sequence during skip fire operation to facilitate execution of the selected engine diagnosis at a time when the designated firing sequence would not otherwise be used to thereby provide conditions appropriate for conducting the diagnosis.

21. A method as recited in claim 16 wherein the diagnosis includes the step of pumping air through the first bank of cylinders for a portion of the time period sufficiently long to saturate with oxygen a catalyst located in an exhaust path associated with the first bank of cylinders.

22. A method as recited in claim 16 wherein the diagnosis includes the step of passing excess or unburnt fuel through the first bank of cylinders sufficiently long to deplete a catalyst located in an exhaust path associated with the first bank of cylinders.

23. An engine controller configured to control operation of an internal combustion engine having a multiplicity of cylinders, each cylinder having an associated fuel injector, the engine further comprising an oxygen sensor located in an exhaust path associated with a plurality of the cylinders, wherein the engine controller is arranged to perform individual fuel injector trim tests while a vehicle that include the internal combustion engine is being driven, the engine controller configured to:
(a) during normal driving conditions, direct operation of the engine at a firing fraction or firing sequence that causes a first one of the cylinders associated with the oxygen sensor to be isolated as the only cylinder associated with the oxygen sensor that is fired over the course of

Assignees

• Tula Technology Inc
• Tula Technology Inc

Inventors

• Chen Shikui Kevin
• Yuan Xin
• Switkes Joshua P
• Carlson Steven E
• Shost Mark A

Classifications

• F02D2250/18

  Control of the engine output torque · CPC title

• F02D17/02 Primary

  Cutting-out (cutting-out engines in multiple engine arrangements F02D25/04) · CPC title

• F02D2041/2027

  Control of the current by pulse width modulation or duty cycle control · CPC title

• F02D17/00

  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 title

• F02D37/02

  one of the functions being ignition · CPC title