Methods and systems for humidity and PCV flow detection via an exhaust gas sensor

Patent metadata

Field	Value
Publication number	US-9797323-B2
Application number	US-201514818646-A
Country	US
Kind code	B2
Filing date	Aug 5, 2015
Priority date	Jan 18, 2013
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

Methods and systems are provided for estimating a PCV flow to an engine based on the output of an exhaust gas oxygen sensor. During DFSO conditions, a reference voltage of the sensor is modulated initially with an intake throttle open and then with the intake throttle closed. PCV flow leaking past the piston valves in an aging engine, as well as an ambient humidity estimate, are inferred based on the outputs of the sensor during the modulating with the intake throttle open and closed.

First claim

The invention claimed is:

1. A method for an engine system, comprising:
during engine non-fueling conditions, where at least one intake valve and one exhaust valve are operating:
opening and closing an intake throttle;
modulating a reference voltage of an exhaust gas sensor with the intake throttle closed and open; and
indicating engine degradation based on an estimated positive crankcase ventilation (PCV) flow, the PCV flow estimated based on outputs of the sensor during the modulating, wherein the intake throttle is positioned upstream of an exhaust gas recirculation (EGR) inlet of an air intake system of the engine system.

2. The method of claim 1 , wherein spark timing is not adjusted during the modulating of the reference voltage of the exhaust gas sensor.

3. The method of claim 1 , wherein an air-fuel ratio is not adjusted during the modulating of the reference voltage of the exhaust gas sensor.

4. The method of claim 1 , wherein EGR is not adjusted during the modulating of the reference voltage of the exhaust gas sensor.

5. The method of claim 4 , wherein opening the intake throttle includes fully opening the intake throttle, and wherein the exhaust gas sensor is an exhaust gas oxygen sensor.

6. The method of claim 4 , wherein modulating the reference voltage includes switching the reference voltage between a first, lower voltage and a second, higher voltage.

7. The method of claim 4 , wherein the engine non-fueling conditions include a deceleration fuel shut off (DFSO).

8. The method of claim 4 , further comprising determining ambient humidity from the exhaust gas sensor, and adjusting the PCV flow and EGR subsequent to determining the ambient humidity.

9. The method of claim 4 , wherein indicating engine degradation based on the estimated PCV flow includes indicating engine degradation based on the estimated PCV flow being higher than a threshold.

10. The method of claim 9 , wherein modulating the reference voltage of the exhaust gas sensor with the intake throttle closed and open includes first modulating the reference voltage between first and second voltages with the intake throttle open, then closing the intake throttle, and then modulating the reference voltage between the first and second voltages with the intake throttle closed.

11. The method of claim 10 , wherein estimating PCV flow based on outputs of the sensor during the modulating includes estimating PCV flow based on a difference between a first change in pumping current output by the sensor during the modulating with the intake throttle open and a second change in pumping current output by the sensor during the modulating with the intake throttle closed.

12. The method of claim 11 , further comprising generating an indication of ambient humidity based on an output of the exhaust gas sensor with the intake throttle open.

13. The method of claim 12 , further comprising adjusting an engine operating parameter based on the indication of ambient humidity and the estimated PCV flow.

14. The method of claim 13 , wherein the engine operating parameter includes an amount of EGR, and wherein the adjusting an amount of EGR includes reducing the amount of EGR responsive to one or more of an indication of higher ambient humidity and an indication of higher than threshold PCV flow.

15. A method for an engine, comprising:
during a first engine non-fueling condition, opening an intake throttle, modulating a reference voltage of an exhaust gas oxygen sensor, and learning a first change in sensor output during the modulating;
during a second engine non-fueling condition, closing the intake throttle, modulating the reference voltage of the exhaust gas oxygen sensor, and learning a second change in sensor output during the modulating; and
generating an indication of positive crankcase ventilation (PCV) flow based on the first change relative to the second change, wherein the throttle is positioned upstream of an exhaust gas recirculation (EGR) inlet of an air intake system of the engine, wherein EGR is not adjusted during the modulating.

16. The method of claim 15 , wherein the first change in sensor output is a first change in pumping current output by the sensor during the modulating with the intake throttle open, and wherein the second change in sensor output is a second change in pumping current output by the sensor during the modulating with the intake throttle closed.

17. The method of claim 16 , further comprising generating an indication of ambient humidity based on the first change but not the second change in sensor output.

18. An engine system, comprising:
an engine with an intake manifold and an exhaust manifold;
an exhaust gas recirculation passage;
an exhaust gas oxygen sensor disposed in the exhaust manifold upstream of an exhaust catalyst;
an intake throttle disposed in the intake manifold; and
a control system in communication with the sensor, the control system including non-transitory instructions for:
during an engine deceleration fuel shut off (DFSO),
closing a positive crankcase ventilation (PCV) port configured to deliver blow-by gases from a crankcase of the engine to the intake manifold;
fully opening the intake throttle;
modulating a reference voltage of the sensor between a first, lower voltage and a second, higher voltage;
generating an indication of ambient humidity based on a first change in pumping current responsive to the modulating of the reference voltage;
maintaining the PCV port closed;
fully closing the intake throttle;
re-modulating the reference voltage of the sensor; and
generating an indication of PCV flow into the intake manifold based on a second change in pumping current responsive to the re-modulating of the reference voltage relative to the first change in pumping current; and

during an engine fueling condition following the engine DFSO, adjusting one or more of exhaust gas recirculation, engine air fuel ratio, and spark timing based on the ambient humidity;
wherein exhaust gas recirculation (EGR) is not adjusted during the modulating.

Assignees

• Ford Global Tech Llc

Inventors

• Surnilla Gopichandra
• Makled Daniel A
• Soltis Richard E

Classifications

• F02D41/1456

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

• F02D41/0055 Primary

  Special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus · CPC title

• F02D41/0005

  during deceleration · CPC title

• F02D41/123

  the fuel injection being cut-off · CPC title

• F02D13/0203

  Variable control of intake and exhaust valves · CPC title