Air-fuel ratio detection device and air-fuel ratio detection method

Patent metadata

Field	Value
Publication number	US-10934958-B2
Application number	US-201916402451-A
Country	US
Kind code	B2
Filing date	May 3, 2019
Priority date	May 8, 2018
Publication date	Mar 2, 2021
Grant date	Mar 2, 2021

Abstract

An air-fuel ratio detection device 1, 1′ comprises: a sensor element 2, 2′ including a sensor cell 10; a voltage application circuit 40, 40′ applying voltage to the sensor cell; a current detector 42, 42′ detecting an output current of the sensor cell; an air-fuel ratio calculating part 61 configured to calculate an air-fuel ratio of an exhaust gas; and a parameter detecting part 62 configured to detect or calculate a temperature correlation parameter correlated with a temperature of the sensor element. The air-fuel ratio calculating part is configured to calculate the air-fuel ratio of the exhaust gas based on the temperature correlation parameter and the output current detected when a predetermined voltage is applied to the sensor cell.

First claim

The invention claimed is:

1. An air-fuel ratio detection device comprising:
a sensor element including a sensor cell;
a voltage application circuit applying voltage to the sensor cell;
a current detector detecting an output current of the sensor cell;
an air-fuel ratio calculating part configured to calculate an air-fuel ratio of an exhaust gas; and
a parameter detecting part configured to detect or calculate a temperature correlation parameter correlated with a temperature of the sensor element, wherein
the air-fuel ratio calculating part is configured to calculate the air-fuel ratio of the exhaust gas based on the temperature correlation parameter and the output current detected when a predetermined voltage is applied to the sensor cell.

2. The air-fuel ratio detection device according to claim 1 , wherein the temperature correlation parameter is a temperature of the sensor element calculated from an impedance of the sensor cell.

3. The air-fuel ratio detection device according to claim 1 , wherein the air-fuel ratio calculating part is configured to convert the output current to a value corresponding to a reference value of the temperature correlation parameter based on the temperature correlation parameter, and calculate the air-fuel ratio of the exhaust gas from the converted value using the relationship of the output current and the air-fuel ratio of the exhaust gas at the reference value.

4. The air-fuel ratio detection device according to claim 2 , wherein the air-fuel ratio calculating part is configured to convert the output current to a value corresponding to a reference value of the temperature correlation parameter based on the temperature correlation parameter, and calculate the air-fuel ratio of the exhaust gas from the converted value using the relationship of the output current and the air-fuel ratio of the exhaust gas at the reference value.

5. The air-fuel ratio detection device according to claim 3 , wherein the air-fuel ratio calculating part is configured to multiply a correction coefficient corresponding to the temperature correlation parameter with the output current to thereby convert the output current to a value corresponding to the reference value.

6. The air-fuel ratio detection device according to claim 4 , wherein the air-fuel ratio calculating part is configured to multiply a correction coefficient corresponding to the temperature correlation parameter with the output current to thereby convert the output current to a value corresponding to the reference value.

7. The air-fuel ratio detection device according to claim 1 , wherein the air-fuel ratio calculating part is configured to use a relationship between the output current and the air-fuel ratio of the exhaust gas at a reference value of the temperature correlation parameter to calculate the air-fuel ratio of the exhaust gas from the output current, and correct the calculated air-fuel ratio based on the temperature correlation parameter to calculate the final air-fuel ratio of the exhaust gas.

8. The air-fuel ratio detection device according to claim 2 , wherein the air-fuel ratio calculating part is configured to use a relationship between the output current and the air-fuel ratio of the exhaust gas at a reference value of the temperature correlation parameter to calculate the air-fuel ratio of the exhaust gas from the output current, and correct the calculated air-fuel ratio based on the temperature correlation parameter to calculate the final air-fuel ratio of the exhaust gas.

9. The air-fuel ratio detection device according to claim 7 , wherein the air-fuel ratio calculating part is configured to add a value obtained by multiplying a correction coefficient corresponding to the temperature correlation parameter with a difference between the calculated air-fuel ratio and a stoichiometric air-fuel ratio to the stoichiometric air-fuel ratio to calculate the final air-fuel ratio of the exhaust gas.

10. The air-fuel ratio detection device according to claim 8 , wherein the air-fuel ratio calculating part is configured to add a value obtained by multiplying a correction coefficient corresponding to the temperature correlation parameter with a difference between the calculated air-fuel ratio and a stoichiometric air-fuel ratio to the stoichiometric air-fuel ratio to calculate the final air-fuel ratio of the exhaust gas.

11. The air-fuel ratio detection device according to claim 5 , wherein the correction coefficient is set to a value different for each sign of the output current.

12. The air-fuel ratio detection device according to claim 6 , wherein the correction coefficient is set to a value different for each sign of the output current.

13. The air-fuel ratio detection device according to claim 9 , wherein the correction coefficient is set to a value different for each sign of the output current.

14. The air-fuel ratio detection device according to claim 10 , wherein the correction coefficient is set to a value different for each sign of the output current.

15. A method of detecting an air-fuel ratio of exhaust gas using a sensor element including a sensor cell, the method comprising:
applying voltage to the sensor cell,
detecting an output current of the sensor cell,
detecting or calculating a temperature correlation parameter correlated with a temperature of the sensor element, and
calculating the air-fuel ratio of the exhaust gas based on the output current and the temperature correlation parameter.

16. An air-fuel ratio detection device comprising:
a sensor element including a sensor cell;
a voltage application circuit applying voltage to the sensor cell;
a current detector detecting an output current of the sensor cell; and
a control device, wherein
the control device is configured to calculate an air-fuel ratio of an exhaust gas and detect or calculate a temperature correlation parameter correlated with a temperature of the sensor element, and
the control device is configured to calculate the air-fuel ratio of the exhaust gas based on the temperature correlation parameter and the output current detected when a predetermined voltage is applied to the sensor cell.

Assignees

• Toyota Motor Co Ltd

Inventors

• Wakao Kazuhiro
• Aoki Keiichiro
• Mizutani Keisuke

Classifications

• G01N27/4076

  Reference electrodes or reference mixtures · CPC title

• F02D41/1439

  characterised by the position of the sensor · CPC title

• F02D41/1494 Primary

  Control of sensor heater · CPC title

• F02D41/1456 Primary

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

• G01N27/4071

  using sensor elements of laminated structure · CPC title