Methods and system for fuel ethanol content estimation and engine control

Patent metadata

Field	Value
Publication number	US-9528448-B2
Application number	US-201514626623-A
Country	US
Kind code	B2
Filing date	Feb 19, 2015
Priority date	Feb 19, 2015
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

Methods and systems are provided for determining an amount of alcohol in fuel injected into an engine based on outputs from an exhaust gas sensor. In one example, a method includes estimating a first fuel alcohol content based on an air-fuel ratio estimated with the exhaust oxygen sensor and estimating a second fuel alcohol content based on a change in sensor output during modulating a reference voltage of the exhaust oxygen sensor between a first and second voltage. The method further includes adjusting engine operation based on a difference between the first and second fuel alcohol contents.

First claim

The invention claimed is:

1. A method, comprising:
estimating a first fuel alcohol content based on an air-fuel ratio estimated with an exhaust oxygen sensor;
after an engine temperature increases above a threshold, estimating a second fuel alcohol content based on a change in sensor output during modulating a reference voltage of the exhaust oxygen sensor between a first and second voltage; and
adjusting engine operation based on a difference between the first and second fuel alcohol contents.

2. The method of claim 1 , further comprising in response to the difference between the first and second fuel alcohol contents being greater than a threshold level, modulating the reference voltage of the exhaust oxygen sensor between the first and second voltage and repeating the estimating the second fuel alcohol content to determine a new second fuel alcohol content.

3. The method of claim 2 , further comprising in response to a difference between the first fuel alcohol content and the new second fuel alcohol content being greater than the threshold level, adjusting engine operation based on the second fuel alcohol content and not the first fuel alcohol content.

4. The method of claim 2 , further comprising in response to the difference between the first and second fuel alcohol contents being less than the threshold level or the difference between the first fuel alcohol content and the new second fuel alcohol content being less than the threshold level, adjusting engine operation based on the first fuel alcohol content and not the second fuel alcohol content.

5. The method of claim 1 , wherein the modulating includes alternating between applying the first voltage and the second voltage to the exhaust oxygen sensor and wherein estimating the second fuel alcohol content includes averaging a change in pumping current output by the exhaust oxygen sensor during the modulating.

6. The method of claim 1 , wherein the estimating the first fuel alcohol content is performed following a re-fueling event and includes operating the exhaust oxygen sensor at the first voltage, determining the air-fuel ratio based on a pumping current output by the exhaust oxygen sensor while operating at the first voltage, determining the first fuel alcohol content based on the determined air-fuel ratio, and updating a previous first fuel alcohol content determined prior to the re-fueling event with the first fuel alcohol content determined following the re-fueling event.

7. The method of claim 1 , wherein estimating the second fuel alcohol content is performed after the engine temperature increases above the threshold and during engine fueling conditions and includes operating the exhaust oxygen sensor in a variable voltage mode by alternating between applying the first voltage and the second voltage to the exhaust oxygen sensor.

8. The method of claim 7 , further comprising correcting sensor outputs at the first voltage and second voltage based on one or more of an air-fuel ratio correction factor and a total pressure correction factor, wherein the air-fuel ratio correction factor is based on a difference between an expected air-fuel ratio open-loop calculated based on fuel injection and air flow amounts and an actual air-fuel ratio measured based on an output of the exhaust oxygen sensor upon applying the first voltage during engine fueling conditions.

9. The method of claim 8 , further comprising:
during engine non-fueling conditions applying each of the first voltage and the second voltage to the exhaust oxygen sensor, the first voltage being a voltage where water molecules are not dissociated and the second voltage being a voltage where water molecules are fully dissociated, and learning a first pressure correction factor for the exhaust oxygen sensor based on a ratio of first and second outputs generated upon applying the first and second voltages, respectively;
learning a second pressure correction factor based on a current barometric pressure and a pressure dependence factor based on a water vapor environment of the exhaust oxygen sensor; and
determining the total pressure correction factor by multiplying the first pressure correction factor by the second pressure correction factor.

10. The method of claim 7 , further comprising correcting the change in sensor output during the modulating based on ambient humidity.

11. The method of claim 10 , further comprising during unfueled engine operation when a transmission shift is not predicted, opening an intake throttle and sequentially applying each of the first and second voltage to the exhaust oxygen sensor and estimating an ambient humidity based on a change in pumping current output by the exhaust oxygen sensor between applying each of the first and second voltage.

12. The method of claim 10 , further comprising during unfueled engine operation when a transmission shift is not predicted, opening an intake throttle and applying the first voltage to the exhaust oxygen sensor and estimating ambient humidity based on a pumping current output by the exhaust oxygen sensor upon applying the first voltage and based on a dry air pumping current.

13. The method of claim 10 , further comprising when a transmission shift is predicted, estimating ambient humidity based on one of an output of an ambient humidity sensor or based on an ambient air temperature.

14. The method of claim 1 where the first voltage is a lower, base voltage where water molecules are not dissociated at the exhaust oxygen sensor and the second voltage is a higher, target voltage where water molecules are dissociated at the exhaust oxygen sensor and wherein the first and second fuel alcohol contents are first and second amounts of alcohol in fuel injected into engine cylinders.

15. A method for an engine, comprising:
during a first condition following a re-fueling event, estimating an air-fuel ratio based on an output of an exhaust oxygen sensor operating at a lower first voltage and determining a first fuel ethanol content estimate based on the air-fuel ratio;
after an engine temperature increases above a threshold while the engine is fueling, determining a second fuel ethanol content estimate based on a change in sensor output when modulating a reference voltage of the exhaust oxygen sensor between the first voltage and a higher second voltage; and
adjusting an engine operating parameter based on an error between the first and second fuel ethanol content estimates.

16. The method of claim 15 , wherein the first condition includes a cold start and wherein the error includes a difference between the first and second fuel ethanol content estimates.

17. The method of claim 15 , further comprising:
during a first condition when the error is less than a threshold, adjusting the engine operating parameter based on the first fuel ethanol content estimate; and
during a second condition when the error is greater than the threshold, repeating the determining the second fuel ethanol content estimate to determine an updated second fuel ethanol content estimate and:
if the error between the first fuel ethanol content estimate and the updated second fuel ethanol content estimate remains above the threshold, adjusting the engine operating parameter based on one of the second fuel ethanol content estimate or the updated second fuel ethanol content estimate; and
if the error between the first fuel ethanol content estimate and the updated second fuel ethanol content estimate is not greater than the threshold, adjusting the engine operating parameter based on the first fuel ethanol content estimate.

Assignees

• Ford Global Tech Llc

Inventors

• Makled Daniel A
• Surnilla Gopichandra
• Soltis Richard E
• Skoures Evangelos P
• Visser Jacobus Hendrik
• Clark Timothy Joseph
• Scholl David James

Classifications

• F02D41/0025

  Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures · CPC title

• F02D19/084

  Blends of gasoline and alcohols, e.g. E85 · CPC title

• F02D41/1454

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

• F02D41/1458

  with determination means using an estimation · CPC title

• G01M15/104

  using oxygen or lambda-sensors (testing catalytic converters F01N3/18, F01N11/007) · CPC title