Spark plug fouling detection for ignition system

Patent metadata

Field	Value
Publication number	US-9534984-B2
Application number	US-201414535157-A
Country	US
Kind code	B2
Filing date	Nov 6, 2014
Priority date	Dec 19, 2013
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

Methods and systems are provided for inferring spark plug fouling due to accumulation of fuel additives thereon. In one example, an engine controller may infer spark plug fouling due to accumulation of fuel additive based on a combination of engine operating parameters correlated with spark plug health. For example, the engine operating parameters may include a change in an adaptive knock term, an engine pre-ignition rate, and engine exhaust oxygen sensor switching frequency over a vehicle drive cycle, and an engine misfire rate.

First claim

The invention claimed is:

1. A method for an engine, comprising:
inferring spark plug fouling due to accumulation of fuel additive based on a combination of two or more of a change in an adaptive knock term, an engine pre-ignition rate, an engine misfire rate, an exhaust oxygen sensor degradation rate, and exhaust catalyst degradation rate over a vehicle drive cycle
in response to the inferring, indicating spark plug fouling due to accumulation of fuel additive
wherein the spark plug is coupled to a cylinder, in response to the indication of spark plug fouling due to accumulation of fuel additive, decreasing an engine load, and disabling fuel while maintaining spark ignition timing for the cylinder for a threshold duration, the threshold duration including a threshold number of combustion cycles.

2. The method of claim 1 , wherein the adaptive knock term includes an amount of spark retard applied at a given engine speed-load condition during the drive cycle, the method further comprising indicating the fouling due to accumulation by setting a diagnostic code, and wherein inferring based on the change in adaptive knock term includes inferring spark plug fouling based on the change in adaptive knock term over a number of engine cycles, where the number of engine cycles is included within one of a given vehicle drive cycle or different vehicle drive cycles, the different vehicle drive cycles separated by a vehicle event including a fuel filling event.

3. The method of claim 1 , wherein the engine pre-ignition rate includes a number of pre-ignition events over one of a threshold duration of a vehicle drive cycle or a threshold distance traveled during the vehicle drive cycle, the threshold duration including one of a threshold amount of time a threshold number of combustion events, or an amount of fuel consumed at the engine.

4. The method of claim 3 , wherein inferring based on the pre-ignition rate includes inferring spark plug fouling based on the pre-ignition rate being higher than a threshold rate, the threshold rate based on a pre-ignition occurrence rate established during vehicle operation with a fuel not including fuel additives.

5. The method of claim 3 , wherein inferring based on the pre-ignition rate includes inferring spark fouling based on the pre-ignition rate increasing by a threshold amount over the threshold duration.

6. The method of claim 1 , wherein inferring based on the exhaust catalyst degradation rate includes inferring spark plug fouling based on the exhaust catalyst degradation rate increasing above a threshold, the exhaust catalyst degradation rate based on an exhaust oxygen sensor switching frequency, the exhaust oxygen sensor switching frequency including one or more of a switching frequency of a first exhaust oxygen sensor coupled upstream of an engine exhaust catalyst, a switching frequency of a second exhaust oxygen sensor coupled downstream of the exhaust catalyst, and a ratio of the switching frequency of the first exhaust oxygen sensor relative to the switching frequency of the second exhaust oxygen sensor.

7. The method of claim 6 , wherein the exhaust catalyst degradation rate is further based on the switching frequency of the first exhaust oxygen sensor being within a threshold difference from the switching frequency of the second exhaust gas oxygen sensor, or the ratio of the switching frequency of the first exhaust oxygen sensor relative to the switching frequency of the second exhaust oxygen sensor being a threshold amount from one.

8. The method of claim 1 , wherein the inferring based on the engine misfire rate over the vehicle drive cycle includes inferring spark plug fouling based on the engine misfire rate being higher than a threshold rate, the threshold rate based on a misfire rate established during vehicle operation with a fuel not including fuel additives.

9. The method of claim 1 , further comprising, indicating spark plug fouling due to accumulation of fuel additive by setting a diagnostic code, the diagnostic code requesting spark plug replacement and wherein indicating spark plug fouling due to accumulation of fuel additive includes indicating spark plug fouling is not due to accumulation of soot.

10. The method of claim 9 , further comprising, receiving operator input regarding replacement of the spark plug, and in response to the operator input, resetting a monitor configured to count each of the change in adaptive knock term, the engine pre-ignition rate, engine misfire rate, and the engine exhaust catalyst switching frequency over a given vehicle drive cycle.

11. The method of claim 10 , wherein the resetting is based on an age of the spark plug relative to an age of one or more other engine components including an exhaust oxygen sensor.

12. A method for an engine, comprising:
over a vehicle drive cycle, monitoring each of a plurality of parameters including a change in an adaptive knock term, an engine pre-ignition rate, an engine misfire rate, an exhaust catalyst degradation rate, and an exhaust oxygen sensor degradation rate; and
in response to two or more of the monitored parameters being higher than corresponding thresholds, indicating spark plug fouling due to fuel additive accumulation
in response to the indication of spark plug fouling due to accumulation of fuel additive, decreasing an engine load, and disabling fuel while maintaining spark ignition timing for the cylinder for a threshold duration, the threshold duration including a threshold number of combustion cycles.

13. The method of claim 12 , wherein the exhaust catalyst degradation rate is based on one or more of a ratio of response times of exhaust oxygen sensors located upstream and downstream of an exhaust catalyst and a response time of one of the exhaust oxygen sensors located upstream of the exhaust catalyst.

14. The method of claim 12 , further comprising, in response to only one of the monitored parameters being higher than the corresponding threshold, not indicating spark plug fouling due to fuel additive accumulation.

15. The method of claim 12 , further comprising, in response to the indicating, decreasing an engine load, and disabling fuel to a cylinder coupled to the fouled spark plug for a number of combustion events.

16. The method of claim 15 , wherein the cylinder is a first cylinder, the method further comprising, in response to the indicating, disabling fuel to a second cylinder not coupled to the fouled spark plug, the second cylinder configured to receive exhaust residuals from the first cylinder.

17. The method of claim 15 , wherein the cylinder is a first cylinder, the method further comprising, in response to indicating, temporarily enriching a second cylinder not coupled to the fouled spark plug, the second cylinder configured to receive exhaust residuals from the first cylinder.

18. The method of claim 12 , further comprising monitoring a control current of an ignition coil coupled to a spark plug and indicating spark plug fouling due to fuel additive accumulation in response to a switching time of the control current being above a threshold and further comprising indicating a severity of spark plug fouling due to fuel additives based on a number of the monitored parameters being higher than corresponding thresholds, the severity increasing with increasing number of monitored parameters higher than corresponding thresholds.

19. 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; and
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Assignees

• Ford Global Tech Llc

Inventors

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

Classifications

• F02P17/12

  Testing characteristics of the spark, ignition voltage or current (testing of sparking plugs H01T13/60) · CPC title

• F02P11/06 Primary

  Indicating unsafe conditions · CPC title

• G01M15/042 Primary

  by monitoring a single specific parameter not covered by groups G01M15/06 - G01M15/12 · CPC title

• F02D41/30

  Controlling fuel injection {(F02D41/182, F02D41/24 take precedence)} · CPC title

• F02D41/1495

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