Spark plug fouling detection for ignition system

Patent metadata

Field	Value
Publication number	US-9777697-B2
Application number	US-201414535174-A
Country	US
Kind code	B2
Filing date	Nov 6, 2014
Priority date	Dec 19, 2013
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

Methods and systems are provided for determining a type of spark plug fouling. In one example, a method may include differentiating spark plug fouling due to soot accumulation from spark plug fouling due to fuel additive accumulation based on a current on a control wire of the spark plug following application of a dwell command. Further, exhaust oxygen sensor degradation and/or exhaust catalyst degradation may be determined based on switching frequencies of one or more exhaust oxygen sensors and the type of spark plug fouling.

First claim

The invention claimed is:

1. A method for an engine, comprising:
for each engine cylinder, differentiating spark plug fouling due to soot accumulation from spark plug fouling due to fuel additive accumulation based on a fraction of combustion cycles, over one or more given vehicle drive cycles, having an ignition current switching time that is higher than a threshold duration.

2. The method of claim 1 , wherein the ignition current switching time is an ignition current switching time of a spark plug including a spark plug ignition coil, the spark plug ignition coil including a control wire, wherein a current on the control wire is measured via a current sensor, and wherein differentiating based on the ignition current switching time includes differentiating based on a switching time taken for the current to drop below a predetermined value after application of a dwell command on the control wire.

3. The method of claim 1 , wherein the differentiating includes,
indicating spark plug fouling due to soot accumulation in response to a change in the fraction over the one or more given vehicle drive cycles fluctuating between the one or more given vehicle drive cycles and indicating spark plug fouling due to fuel additive accumulation in response to the change in the fraction remaining constant or increasing between the one or more given vehicle drive cycles.

4. The method of claim 1 , wherein the differentiating includes,
indicating spark plug fouling due to soot accumulation in response to the fraction being smaller than a threshold percentage and indicating spark plug fouling due to fuel additive accumulation in response to the fraction being larger than the threshold percentage.

5. The method of claim 4 , wherein the differentiating is further based on an average cylinder ignition event switching time for combustion cycles over the given vehicle drive cycle, and wherein the differentiating includes indicating spark plug fouling due to fuel additive accumulation in response to the average cylinder ignition event switching time being longer than a threshold time, and indicating spark plug fouling due to soot accumulation in response to the average cylinder ignition event switching time being shorter than the threshold time.

6. The method of claim 5 , further comprising indicating a degree of spark plug fouling based on the switching time.

7. The method of claim 4 , further comprising, in response to the indication of spark plug fouling due to soot accumulation, but not due to fuel additive accumulation, temporarily raising a spark plug tip temperature above a threshold temperature for a threshold number of engine cycles by one or more of advancing spark timing from MBT and increasing an engine speed or load.

8. The method of claim 4 , wherein indicating spark plug fouling due to fuel additive accumulation includes indicating no spark plug fouling due to soot accumulation and further comprising, in response to the indication of spark plug fouling due to fuel additive accumulation, one or more of limiting an engine load, setting a diagnostic code to recommend spark plug replacement, and temporarily enriching a second cylinder, wherein the fouled spark plug is coupled to a first cylinder, the second cylinder configured to receive exhaust residuals from the first cylinder.

9. The method of claim 4 , further comprising,
monitoring a switching frequency of each of a first exhaust oxygen sensor coupled upstream of an exhaust catalyst and a second exhaust oxygen sensor coupled downstream of the exhaust catalyst over a number of engine cycles; and
in response to a ratio of the switching frequency of the first and second exhaust oxygen sensor being within a threshold of each other over the number of engine cycles while spark plug fouling due to fuel additive accumulation is indicated, indicating exhaust catalyst degradation due to fuel additive accumulation.

10. The method of claim 1 , further comprising, in response to operator input indicative of spark plug replacement, resetting a counter configured to count the fraction of combustion cycles, over the given vehicle drive cycle, having an ignition current switching time that is higher than the threshold duration.

11. A method for an engine, comprising:
indicating spark plug fouling due to soot accumulation in response to a fraction of combustion cycles over a vehicle drive cycle having an ignition current switching time that is longer than a threshold duration being less than a threshold percentage; and
indicating spark plug fouling due to fuel additive accumulation in response to the fraction being more than the threshold percentage.

12. The method of claim 11 , wherein the threshold percentage is based on an average percentage in an engine not exposed to fuel additives, wherein the threshold duration is based on a dwell command applied to an ignition system of the engine during a cylinder ignition event, and further based on an operational status of a current sink of the ignition system, wherein indicating spark plug fouling due to soot accumulation includes indicating no spark plug fouling due to fuel additive accumulation, and wherein indicating spark plug fouling due to fuel additive accumulation includes indicating no spark plug fouling due to soot accumulation.

13. The method of claim 11 , further comprising, indicating spark plug fouling due to soot accumulation based on a decrease in the fraction following engine operation at or above a threshold engine speed or load that raises a spark plug tip temperature above a threshold temperature.

14. The method of claim 11 , further comprising, in response to the indication of spark plug fouling due to fuel additive accumulation, limiting an engine load, and based on an identity of the cylinder coupled to the fouled spark plug, enriching an adjacent cylinder configured to receive exhaust residuals from the cylinder coupled to the fouled spark plug.

15. The method of claim 11 , further comprising, in response to the indication of spark plug fouling due to soot accumulation, setting a first diagnostic code to recommend spark plug cleaning, and in response to the indication of spark plug fouling due to fuel additive accumulation, setting a second, different diagnostic code to recommend spark plug replacement.

16. The method of claim 11 , further comprising,
after indicating spark plug fouling due to fuel additive accumulation,
monitoring a response time of each of a first exhaust oxygen sensor coupled upstream of an exhaust catalyst and a second exhaust oxygen sensor coupled downstream of the exhaust catalyst over a number of engine cycles; and
in response to a ratio of the response times of the first and second exhaust oxygen sensor being within a threshold of one another over the number of engine cycles, indicating exhaust catalyst degradation due to fuel additive accumulation.

17. The method of claim 16 , wherein the first exhaust oxygen sensor is a UEGO sensor and wherein the second exhaust oxygen sensor is a HEGO sensor.

18. An engine system, comprising:
an engine including a cylinder;
an ignition system including an ignition coil and a control wire coupled to a spark plug of the cylinder, the ignition system further including a current sensor for sensing a current of the control wire;
a direct fuel injector for delivering fuel to the cylinder;
a throttle coupled to an engine intake manifold for adjusting an airflow to the cylinder; and
a controller with computer readable instructions on non-transitory memory for:
outputting a dwell command on the control wire

Assignees

• Ford Global Tech Llc

Inventors

• Glugla Chris Paul
• Huberts Garlan J
• Morrow Nelson William
• Qu Qiuping

Classifications

• F02P2017/121

  by measuring spark voltage · CPC title

• F02B2075/125

  Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber · CPC title

• F02D41/1495

  Detection of abnormalities in the air/fuel ratio feedback system · CPC title

• F02P17/10

  Measuring dwell or antidwell time · CPC title

• F01N11/00 Primary

  Monitoring or diagnostic devices for exhaust-gas treatment apparatus · CPC title