Method and system for estimating temperature of a heated exhaust gas oxygen sensor in an exhaust system having a variable length pipe

• US 5,901,553 A
• Filed: 06/30/1997
• Issued: 05/11/1999
• Est. Priority Date: 03/29/1995
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Cullen, Michael John
• Primary Examiner(s): Verdier, Christopher
• Assistant Examiner(s): TRAN, BINH Q
• Application Number:
  US08/885,206
• Time in Patent Office: 680 Days
• Field of Search: 60/274, 60/276, 60/287, 60/286, 123/697, 123/690, 701/109, 701/103, 73/23.32, 204/421, 204/427, 364/557
• US Class Current: 60/274
• CPC Class Codes: F01N 2240/02 a heat exchanger
• CPC Class Codes: F01N 2410/00 By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device
• CPC Class Codes: F01N 3/20 specially adapted for catalytic conversion F01N3/22 takes precedence; Methods of operation or control of catalytic converters
• CPC Class Codes: F02D 41/1401 characterised by the control or regulation method F02D41/1473, F02D41/1477 take precedence
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1494 Control of sensor heater

Abstract

A method for estimating a temperature of a tip of an exhaust gas oxygen (EGO) sensor used with a heater in an electronic engine control for an engine having an exhaust system wherein the exhaust system includes a variable length exhaust pipe having a short path and a long path for transporting exhaust gas from the engine to the HEGO sensor and an exhaust valve positioned in the exhaust pipe for regulating the flow of exhaust gas between the short path and the long path utilizes control logic to determine whether the exhaust gas is flowing through the short path or the long path, determine a temperature of the unheated HEGO sensor based on the path of flow of the exhaust gas, and determine whether the heater is on. If the heater is not on, an amount of heat applied to the sensor is set to zero. If the heater is on, an increase in the temperature of the HEGO sensor is determined based on an amount of heat applied to the sensor. The control logic then determines the temperature of the heated HEGO sensor based on the temperature of the unheated HEGO sensor and the increase in the temperature.

Claims

1. A method for estimating a temperature of a tip of an exhaust gas oxygen sensor used with a heater (HEGO) in an electronic engine control for an engine having an exhaust system, the exhaust system including a variable length exhaust pipe having a short path and a long path for transporting exhaust gas from the engine to the HEGO sensor, the exhaust system further including an exhaust valve positioned in the exhaust pipe for regulating the flow of exhaust gas between the short path and the long path, the method comprising:

determining whether the exhaust gas is flowing through the short path or the long path;

determining a temperature of the unheated HEGO sensor based on the path of flow of the exhaust gas;

determining whether the heater is on;

if no, setting an amount of heat applied to the sensor to zero;

if yes, determining an increase in the temperature of the HEGO sensor based on an amount of heat applied to the sensor; and

determining the temperature of the heated HEGO sensor based on the temperature of the unheated HEGO sensor and the increase in the temperature.

2. The method as recited in claim 1 wherein determining the temperature of the unheated HEGO sensor comprises:

determining a temperature loss from a point near an exhaust flange of the exhaust pipe to the HEGO sensor based on the path of flow of the exhaust gas;

determining a steady state temperature of the HEGO sensor based on the temperature loss;

determining a time constant that describes a speed at which the heat from the exhaust of a running engine will dissipate from the tip of the HEGO sensor; and

determining a rolling average of the steady state temperature of the unheated HEGO sensor and the effect of the heat of the exhaust of a running engine on the HEGO sensor.

3. The method as recited in claim 2 wherein determining the temperature loss includes determining the temperature loss according to the following:

space="preserve" listing-type="equation">EXT.sub.-- LS.sub.-- FEU=fn446.sub.-- tmp* ((EXT.sub.-- FL+EXT.sub.-- FEU.sub.-- PREV)/2)-INFAMB!,

where EXT_-- LS_-- FEU corresponds to the temperature loss, fn446_-- tmp is a value indicative of a temperature drop between the exhaust flange and the HEGO sensor as a function of a flow signal, EXT_-- FL corresponds to the instantaneous temperature of exhaust gas at the exhaust flange, EXT_-- FEU_-- PREV corresponds to the previously determined value of an instantaneous temperature of the unheated HEGO sensor, and INFAMB corresponds to a value indicative of an estimate of ambient air temperature in degrees Fahrenheit.

4. The method as recited in claim 3 wherein determining the temperature loss includes determining the value fn446_-- tmp according to the following:

space="preserve" listing-type="equation">fn446.sub.-- tmp=path.sub.-- wgt*fn446.sub.-- short(AM)+(1-path.sub.-- wgt)*fn446.sub.-- long(AM),

where path_-- wgt corresponds to a value representative of the path flow of the exhaust gas, fn446_-- short(AM) corresponds to a temperature drop from the exhaust flange to the HEGO sensor via the short path expressed in units of degrees of actual temperature drop per degrees of potential temperature drop, and fn446_-- long(AM) corresponds to the temperature drop from the exhaust flange to the HEGO sensor via the long path expressed in units of degrees of actual temperature drop per degrees of potential temperature drop.

5. The method as recited in claim 1 wherein determining the increase in the temperature of the HEGO sensor includes determining the amount of heat being applied to the tip of the HEGO sensor utilizing a linear equation versus the HEGO sensor temperature in the following formula:

EXT_-- SS_-- FEH=EXT_-- FEH_-- INT-EXT_-- FEH_-- SLP*EXT_-- FEU where EXT_-- FEH_-- INT is an intercept of the applied heat versus time, EXT_-- FEH_-- SLP is the slope of the applied heat versus time and EXT_-- FEU is the temperature of the unheated HEGO sensor.

6. The method as recited in claim 1 wherein determining the increase in the temperature of the HEGO sensor includes determining the amount of heat being applied to the tip of the HEGO sensor utilizing a table lookup of the effect of the applied heat versus the temperature of the unheated HEGO sensor with piece-wise linear interpolation.

7. The method as recited in claim 1 wherein determining the temperature of the heated HEGO sensor comprises:

determining a speed at which the HEGO sensor will heat; and

determining a rolling average of the magnitude of the amount of heat applied to the HEGO sensor by the heater based on the amount of heat applied to the HEGO sensor and the speed at which the HEGO sensor will heat up.

8. The method as recited in claim 7 wherein determining the speed includes determining the speed utilizing a lookup table versus air mass.

9. The method as recited in claim 7 wherein determining the speed includes determining the speed utilizing a lookup table versus temperature of the unheated HEGO sensor.

10. A system for estimating a temperature of a tip of an exhaust gas oxygen sensor used with a heater (HEGO) in an electronic engine control for an engine having an exhaust system, the exhaust system including a variable length exhaust pipe having a short path and a long path for transporting exhaust gas from the engine to the HEGO sensor, the exhaust system further including an exhaust valve positioned in the exhaust pipe for regulating the flow of exhaust gas between the short path and the long path, the system comprising:

control logic operative to determine whether the exhaust gas is flowing through the short path or the long path, determine a temperature of the unheated HEGO sensor based on the path of flow of the exhaust gas, determine whether the heater is on, set an amount of heat applied to the sensor to zero if the heater is not on, determine an increase in the temperature of the HEGO sensor based on an amount of heat applied to the sensor if the heater is on, and determine the temperature of the heated HEGO sensor based on the temperature of the unheated HEGO sensor and the increase in the temperature.

11. The system as recited in claim 10 wherein the control logic, in determining the temperature of the unheated HEGO sensor, determines a temperature loss from a point near an exhaust flange of the exhaust pipe to the HEGO sensor based on the path of flow of the exhaust gas, determines a steady state temperature of the HEGO sensor based on the temperature loss, determines a time constant that describes a speed at which the heat from the exhaust of a running engine will dissipate from the tip of the HEGO sensor, and determines a rolling average of the steady state temperature of the unheated HEGO sensor and the effect of the heat of the exhaust of the running engine on the HEGO sensor.

12. The system as recited in claim 11 wherein the control logic determines the temperature loss according to the following:

space="preserve" listing-type="equation">EXT.sub.-- LS.sub.-- FEU=fn446.sub.-- tmp* ((EXT.sub.-- FL+EXT.sub.-- FEU.sub.-- PREV)/2)-INFAMB!,

where EXT_-- LS_-- FEU corresponds to the temperature loss, fn446_-- tmp is a value indicative of a temperature drop between the exhaust flange and the HEGO sensor as a function of a flow signal, EXT_-- FL corresponds to the instantaneous temperature of exhaust gas at the exhaust flange, EXT_-- FEU_-- PREV corresponds to the previously determined value of the instantaneous temperature of the unheated HEGO sensor, and INFAMB corresponds to a value indicative of an estimate of ambient air temperature in degrees Fahrenheit.

13. The system as recited in claim 12 wherein the control logic determines the value fn446_-- tmp according to the following:

space="preserve" listing-type="equation">fn446.sub.-- tmp=path.sub.-- wgt*fn446.sub.-- short(AM)+(1-path.sub.-- wgt)*fn446.sub.-- long(AM),

where path_-- wgt corresponds to a value representative of the path flow of the exhaust gas, fn446_-- short(AM) corresponds to a temperature drop from the exhaust flange to the HEGO sensor via the short path expressed in units of degrees of actual temperature drop per degrees of potential temperature drop, and fn446_-- long(AM) corresponds to the temperature drop from the exhaust flange to the HEGO sensor via the long path expressed in units of degrees of actual temperature drop per degrees of potential temperature drop.

14. The system as recited in claim 10 wherein the control logic, in determining the increase in the temperature of the HEGO sensor, determines the amount of heat being applied to the tip of the HEGO sensor utilizing a linear equation versus the HEGO sensor temperature in the following formula:

EXT_-- SS_-- FEH=EXT_-- FEH_-- INT-EXT_-- FEH_-- SLP*EXT_-- FEU where EXT_-- FEH_-- INT is an intercept of the applied heat versus time, EXT_-- FEH_-- SLP is the slope of the applied heat versus time and EXT_-- FEU is the temperature of the unheated HEGO sensor.

15. The system as recited in claim 10 wherein the control logic, in determining the increase in the temperature of the HEGO sensor, determines the amount of heat being applied to the tip of the HEGO sensor utilizing a table lookup of the effect of the applied heat versus the temperature of the unheated HEGO sensor with piece-wise linear interpolation.

16. The system as recited in claim 10 wherein the control logic, in determining the temperature of the heated HEGO sensor, determines the speed at which the HEGO sensor will heat, and determines a rolling average of the magnitude of the amount of heat applied to the HEGO sensor by the heater based on the amount of heat applied to the HEGO sensor and a speed at which the HEGO sensor will heat up.

17. The system as recited in claim 16 wherein the control logic, in determining the speed, determines the speed utilizing a lookup table versus air mass.

18. The system as recited in claim 16 wherein the control logic, in determining the speed, determines the speed utilizing a lookup table versus temperature of the unheated HEGO sensor.

19. An article of manufacture for an exhaust system of an internal combustion engine of an automotive vehicle, the exhaust system including a variable length exhaust pipe having a short path and a long path for transporting exhaust gas from the engine to a catalytic converter and an exhaust valve positioned in the exhaust pipe for regulating the flow of exhaust gas between the short path and the long path, the article of manufacture comprising:

a computer storage medium having a computer program encoded therein for determining whether the exhaust gas is flowing through the short path or the long path, determining a temperature of the unheated HEGO sensor based on the path of flow of the exhaust gas, determining whether the heater is on, setting an amount of heat applied to the sensor to zero if the heater is not on, determining an increase in the temperature of the HEGO sensor based on an amount of heat applied to the sensor if the heater is on, and determining the temperature of a heated HEGO sensor based on the temperature of an unheated HEGO sensor and the increase in the temperature.