Method and system for optimizing purge of exhaust gas constituent stored in an emission control device

• US 20030004634A1
• Filed: 06/19/2001
• Published: 01/02/2003
• Est. Priority Date: 06/19/2001
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Asik, Joseph Richard, Meyer, Garth Michael
• Granted Patent: US 6,691,020 B2
• Time in Patent Office: Days
• US Class Current: 701/108
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: B01D 53/96 Regeneration, reactivation or recycling of reactants
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F01N 3/101 Three-way catalysts
• CPC Class Codes: F02D 41/0275 the exhaust gas treating apparatus being a NOx trap or adsorbent
• CPC Class Codes: F02D 41/1439 characterised by the position of the sensor
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A method and system for optimizing the purging of a constituent gas of a vehicle engine'"'"'s generated exhaust gas from an emission control device is disclosed wherein the amplitude of the output signal generated by a downstream switching oxygen sensor, and the time response of the sensor, is used to iteratively adjust a current purge time to obtain an optimized purge time.

Claims

1. A method of optimizing a purge time for an emission control device located in the exhaust passage of an engine upstream from an oxygen sensor, during which an amount of a previously-stored constituent gas of the engine-generated exhaust gas is released from the device, the method comprising:

detecting the sensor output voltage;

calculating a purge time correction factor related to a characteristic of the sensor output voltage; and

calculating a subsequent purge time as a function of the product of the correction factor and a present purge time.

2. The method of claim 1, wherein the purge time correction factor is based on the error between a desired saturation time value and a calculated saturation time value.

3. The method of claim 2, wherein the sensor output voltage is sampled during a window to determine the peak voltage.

4. The method of claim 3, wherein the calculated saturation time value is based on the time that the peak voltage is greater than a reference voltage.

5. The method of claim 3, wherein the calculated saturation time is based on the value of the peak voltage.

6. The method of claim 3, wherein the calculated saturation time value is based on the value of the peak voltage if the peak voltage is less than or equal to a predetermined reference voltage and is otherwise based on the time that the peak voltage exceeds the reference voltage.

7. The method of claim 6, wherein the error is input to a feedback controller that produces the correction factor.

8. The method of claim 7, wherein there is a direct, monotonic relationship between the correction factor and the error.

9. The method of claim 7, wherein optimization of purge time is continued until the absolute value of the difference between present and subsequent purge time values, is less than an allowable tolerance.

10. The method of claim 9, wherein the error is normalized to a reference saturation value.

11. The method of claim 10, wherein the sensor is a switching type sensor.

13. The method of claim 12, wherein the fill time is based on device capacity as represented by the equation:

15. The system of claim 14, wherein the purge time correction factor is based on the error between a desired saturation time value and a calculated saturation time value.

16. The system of claim 15, wherein the calculated saturation time value is based on the value of the peak voltage if the peak voltage is less than or equal to a predetermined reference voltage and is otherwise based on the time that the peak voltage exceeds the reference voltage.

17. The system of claim 16, wherein the error is input to a feedback controller that produces the correction factor.

18. The system of claim 17, wherein optimization of purge time is continued until the absolute value of the difference between present and subsequent purge time values, is less than an allowable tolerance.

19. The system of claim 18, wherein the error is normalized to a reference saturation value.

20. The system of claim 19, wherein the sensor is a switching-type sensor.

12. A closed-loop method of optimizing a purge time for an emission control device located in the exhaust passage of an engine upstream from a switching oxygen sensor, during which an amount of a previously-stored constituent gas of the engine-generated exhaust gas is released from the device, the method comprising:

detecting the voltage of the sensor for an existing purge time, following an existing fill time, to determine whether the purge time should be changed;

if the peak voltage of the sensor is less than a predetermined reference voltage then calculating a first saturation time based on the peak voltage;

if the peak voltage is greater than the reference voltage then measuring the time that the peak voltage remains above the reference voltage and calculating a second saturation time related to the time that the peak voltage remains above the reference voltage;

utilizing the error between a desired saturation time and the calculated saturation time as feedback to a controller for producing a purge time correction factor;

calculating the next purge time equal to the product of the correction factor and the previous purge time and;

storing the purge time when the difference between a present and subsequent purge time is greater than a predetermined tolerance.

14. A system for optimizing a purge time for an emission control device located in the exhaust passage of an engine, during which an amount of a previously-stored constituent gas of the engine-generated exhaust gas is released from the device, the system comprising:

an oxygen sensor providing an output signal representative of the concentration of oxygen present in the exhaust flowing through the device during a sampling period; and

a control module for detecting the peak voltage of the sensor output voltage, calculating a purge time correction factor related to the peak voltage, and calculating a subsequent purge time as a function of the product of the correction factor and a present purge time.