Methods and systems for estimating ambient pressure using an oxygen sensor

Patent metadata

Field	Value
Publication number	US-9926872-B2
Application number	US-201614997309-A
Country	US
Kind code	B2
Filing date	Jan 15, 2016
Priority date	Jan 15, 2016
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

Methods and systems are provided for leveraging the pressure dependency of an oxygen sensor for estimating an engine ambient pressure. An intake or exhaust oxygen sensor is used for ambient pressure estimation by applying a reference voltage to the sensor while the engine is being pulled-down in a hybrid vehicle, and correcting an output of the sensor for dilution effects due to ambient humidity. The estimated ambient pressure is used to correct or confirm pressure estimated by other sources, such as other pressure sensors or a pressure model, as well as to tune the performance of the engine.

First claim

The invention claimed is:

1. A method for a hybrid vehicle, comprising:
when propelling the vehicle using engine torque, estimating combustion air-fuel ratio via an oxygen sensor; and
when propelling the vehicle using motor torque, estimating an ambient pressure of intake air based on an estimate of humidity via the oxygen sensor.

2. The method of claim 1 , wherein the oxygen sensor is an exhaust gas sensor coupled in an exhaust passage of an engine of the hybrid vehicle, upstream of an exhaust catalyst.

3. The method of claim 1 , wherein the oxygen sensor is an intake oxygen sensor coupled to an intake passage of an engine of the hybrid vehicle, downstream of an intake throttle.

4. The method of claim 1 , wherein engine speed is less than a threshold speed when propelling the vehicle using motor torque.

5. The method of claim 1 , wherein the estimating of ambient pressure includes applying a reference voltage to the sensor, correcting a pumping current output by the oxygen sensor based on the estimate of humidity, and estimating the ambient pressure based on the corrected pumping current and a conversion factor, where the conversion factor converts the corrected pumping current into an equivalent ambient pressure.

6. The method of claim 5 , wherein the conversion factor is based on a learned ambient pressure dependency of the oxygen sensor.

7. The method of claim 5 , wherein the estimate of humidity is based on the oxygen sensor during engine non-fueling conditions, and wherein the reference voltage is a first, lower reference voltage.

8. The method of claim 7 , wherein the estimate of humidity includes sequentially applying each of the first, lower reference voltage and a second, higher reference voltage to the oxygen sensor, and where the estimate of humidity is based on a first pumping current output by the sensor upon application of the first voltage relative to a second pumping current output by the sensor upon application of the second voltage.

9. The method of claim 8 , wherein the first voltage is a voltage at which water molecules are not dissociated at the oxygen sensor and the second voltage is a voltage at which water molecules are dissociated.

10. The method of claim 1 , further comprising, adjusting engine operation while propelling the vehicle using engine torque based on the ambient pressure of intake air estimated while propelling the vehicle using motor torque, the adjusting engine operation including one or more of adjusting engine fueling, engine air charge, and engine boosting.

11. A method, comprising:
during an engine-off condition, estimating an ambient pressure of intake air based on an ambient humidity estimate and an output of an oxygen sensor disposed in an exhaust passage at a reference voltage; and
during a subsequent engine-on condition, adjusting engine operation based on the ambient humidity estimate.

12. The method of claim 11 , wherein the engine-off condition includes the engine decelerating unfueled from a threshold speed.

13. The method of claim 11 , further comprising, during the engine-off condition, estimating an ambient humidity of intake air based on a difference in output of the oxygen sensor upon modulation of the reference voltage between an upper and a lower voltage.

14. The method of claim 13 , wherein the reference voltage is the lower voltage, and wherein estimating the ambient pressure includes correcting the output at the reference voltage based on the estimated ambient humidity and further based on a conversion factor that converts the corrected output into an equivalent ambient pressure.

15. The method of claim 14 , wherein the output of the oxygen sensor are pumping currents output while the oxygen sensor is operating at the reference voltage.

16. The method of claim 11 , further comprising confirming one or more of an ambient pressure estimated by a pressure sensor coupled to an intake passage of the engine, and a modeled ambient pressure using the ambient pressure estimated based on the output of the oxygen sensor.

17. A vehicle system, comprising:
wheels;
an engine for propelling the wheels via engine torque;
an electric motor for propelling the wheels via motor torque;
an oxygen sensor coupled to an exhaust passage of the engine; and
a controller with computer readable instructions stored on non-transitory memory for:
adjusting engine operation based on an ambient pressure of intake air flowing through an intake passage of the engine, where the ambient pressure is estimated during an engine non-fueling condition based on an output of the oxygen sensor at a reference voltage where water molecules are not dissociated and further based on an ambient humidity estimate and a conversion factor.

18. The system of claim 17 , wherein the engine non-fueling condition includes an engine pull-down from a threshold speed where the wheels are propelled via the motor torque, and wherein the controller includes instructions for correcting the output of the oxygen sensor at the reference voltage based on the ambient humidity estimate.

19. The system of claim 18 , further comprising a pressure sensor coupled to the intake passage of the engine, wherein the controller includes further instructions for estimating the ambient pressure via the pressure sensor when the engine is operating fueled and indicating degradation of the pressure sensor based on the ambient pressure estimated via the pressure sensor relative to the ambient pressure estimated via the oxygen sensor.

20. The system of claim 17 , wherein the reference voltage is a lower voltage where water molecules do not dissociate at the oxygen sensor, the controller including further instructions for estimating the ambient humidity estimate during the engine pull-down based on a difference in output of the oxygen sensor upon modulation of the reference voltage between the lower voltage and an upper voltage where water molecules do dissociate at the oxygen sensor, and wherein the output of the oxygen sensor includes a pumping current output upon application of the reference voltage.

Assignees

• Ford Global Tech Llc

Inventors

• Makled Daniel A
• Mcquillen Michael
• Surnilla Gopichandra
• Soltis Richard E

Classifications

• Y02T10/40

  Engine management systems · CPC title

• F01N2590/11

  for hybrid vehicles · CPC title

• F02D41/1456

  with sensor output signal being linear or quasi-linear with the concentration of oxygen · CPC title

• F01N13/008 Primary

  Mounting or arrangement of exhaust sensors in or on exhaust apparatus (sensor arrangements for engine control F02D41/1439) · CPC title

• F01N2900/12

  said parameters being related to the vehicle exterior · CPC title