Methods and systems for determining a fuel concentration in engine oil using an intake oxygen sensor

Patent metadata

Field	Value
Publication number	US-9234476-B2
Application number	US-201414252679-A
Country	US
Kind code	B2
Filing date	Apr 14, 2014
Priority date	Apr 14, 2014
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

Methods and systems are provided for estimating a fuel concentration in engine oil in an engine crankcase. In one example, an engine controller may adjust engine operation such as EGR flow and engine fueling based on the estimated fuel concentration in engine oil. The fuel concentration may be based on an output of an intake oxygen sensor when purge and EGR flow are disabled, engine oil temperature, and fuel composition.

First claim

The invention claimed is:

1. A method for an engine, comprising:
adjusting engine operation based on a fuel concentration in engine oil, the fuel concentration based on an output of an intake oxygen sensor when purge and EGR flow are disabled, engine oil temperature, and fuel composition.

2. The method of claim 1 , further comprising estimating a fuel evaporation rate from engine oil based on a concentration gradient between the fuel concentration in engine oil and the output of the intake oxygen sensor, the output of the intake oxygen sensor indicative of a fuel concentration in intake air.

3. The method of claim 2 , wherein adjusting engine operation includes adjusting fuel injection to the engine based on the estimated fuel evaporation rate, an amount of fuel injected decreasing with increasing estimated fuel evaporation rate.

4. The method of claim 2 , wherein adjusting engine operation includes disabling EGR flow for a duration when an actual output of the intake oxygen sensor differs from an expected output of the intake oxygen sensor by a threshold amount, the expected output based on the estimated fuel evaporation rate.

5. The method of claim 1 , wherein adjusting engine operation includes adjusting a position of an EGR valve based on the output of the intake oxygen sensor relative to the fuel concentration in engine oil.

6. The method of claim 1 , wherein the fuel concentration is further based on crankcase pressure and boost conditions.

7. The method of claim 1 , wherein the intake oxygen sensor is positioned in an intake passage downstream of an inlet of a low-pressure EGR passage into the intake passage, the low-pressure EGR passage positioned between an exhaust passage downstream of a turbine and an intake passage upstream of a compressor.

8. A method for an engine, comprising:
during boosted engine operation, flowing PCV gases to an engine intake upstream of an intake oxygen sensor;
estimating a vapor pressure based on an engine oil temperature and a composition of fuel;
estimating a fuel concentration in engine oil based on the estimated vapor pressure and an output of the intake oxygen sensor when purge flow and EGR are disabled; and
adjusting an EGR valve based on the estimated fuel concentration in engine oil and the output of the intake oxygen sensor.

9. The method of claim 8 , further comprising estimating a fuel evaporation rate from engine oil based on a concentration gradient between the output of the intake oxygen sensor and the estimated fuel concentration in engine oil.

10. The method of claim 9 , further comprising adjusting engine fueling based on the estimated fuel evaporation rate and wherein adjusting engine fueling includes adjusting an amount of fuel injected to the engine or a fuel pressure.

11. The method of claim 9 , further comprising setting a diagnostic flag to disable EGR and indicating degradation of the estimated fuel concentration in engine oil due to an expected output of the intake oxygen sensor differing from an actual output of the intake oxygen sensor by a threshold amount, the expected output of the intake oxygen sensor based on the estimated fuel evaporation rate.

12. The method of claim 11 , further comprising removing the diagnostic flag to re-enable EGR when the expected output of the intake oxygen sensor based on the estimated fuel evaporation rate is within the threshold amount of the actual output of the intake oxygen sensor.

13. The method of claim 11 , further comprising disabling purge at a first frequency in order to determine if degradation of the estimated fuel concentration in engine oil is indicated, the first frequency based on engine oil temperature when EGR is not disabled due to an impact of hydrocarbons on the output of the intake oxygen sensor.

14. The method of claim 13 , further comprising disabling purge at a second frequency, higher than the first frequency, in order to determine if degradation of the estimated fuel concentration in engine oil is indicated, the second frequency based on a set time duration when EGR has been disabled due to the impact of hydrocarbons on the output of the intake oxygen sensor.

15. The method of claim 9 , further comprising storing the estimated fuel evaporation rate and the estimated fuel concentration in engine oil as a function of engine oil temperature in a memory of a controller of the engine.

16. The method of claim 15 , further comprising obtaining an output of the intake oxygen sensor at a set interval when purge and EGR are disabled and then updating the stored fuel evaporation rate and fuel concentration in engine oil, the set interval based on engine oil temperature.

17. The method of claim 8 , further comprising during non-boosted engine operation, flowing PCV gases to the engine intake downstream of the intake oxygen sensor and adjusting the EGR valve based on the output of the intake oxygen sensor on not based on the estimated fuel concentration in engine oil.

18. A system for an engine, comprising:
an intake manifold;
a crankcase coupled to the intake manifold via a PCV valve;
a turbocharger with an intake compressor, an exhaust turbine, and a charge air cooler;
an intake throttle coupled to the intake manifold downstream of the charge air cooler;
a canister configured to receive fuel vapors from a fuel tank, the canister coupled to the intake manifold via a purge valve;
a low-pressure exhaust gas recirculation (EGR) passage coupled between an exhaust passage downstream of the exhaust turbine and an intake passage upstream of the intake compressor, the low-pressure EGR passage including a low-pressure EGR valve and low-pressure DPOV sensor for measuring low-pressure EGR flow;
an intake oxygen sensor coupled to the intake manifold downstream of the charge air cooler and upstream of the intake throttle; and
a controller with computer readable instructions for adjusting the low-pressure EGR valve based on an estimated fuel concentration in engine oil and an output of the intake oxygen sensor, the estimated fuel concentration in engine oil based on the output of the intake oxygen sensor when purge and EGR flow are disabled, engine oil temperature, and fuel composition.

19. The system of claim 18 , wherein the computer readable instructions further include instructions for adjusting fuel injection to the engine based on an evaporation rate of fuel from the crankcase, the evaporation rate based on a concentration gradient between the estimated fuel concentration in engine oil and the output of the intake oxygen sensor.

20. The system of claim 18 , wherein the computer readable instructions further include closing the low-pressure EGR valve in order to disable EGR flow responsive to a difference between a predicted output of the intake oxygen sensor and an actual output of the intake oxygen sensor being greater than a threshold amount, the predicted output of the intake oxygen sensor based on the evaporation rate.

Assignees

• Ford Global Tech Llc

Inventors

• Hakeem Mohannad
• Surnilla Gopichandra
• Anderson James Eric

Classifications

• F02D41/1454

  the characteristics being an oxygen content or concentration or the air-fuel ratio · CPC title

• F02D2250/08

  Engine blow-by from crankcase chamber · CPC title

• F02D41/144 Primary

  Sensor in intake manifold · CPC title

• F02D41/1459

  the characteristics being a hydrocarbon content or concentration · CPC title

• F02M26/46

  for determining the characteristics of gases, e.g. composition · CPC title