METHOD OF CONTROLLING ENGINE USING HEATED EXHAUST GAS SENSOR

Abstract

There is provided a method of controlling an internal combustion engine system. The method comprises supplying a first amount of electric energy to heat to an upstream sensor located in an exhaust gas passage from the internal combustion engine and upstream of an exhaust gas after-treatment device and adjusting an air-fuel mixture supplied to the internal combustion engine based on an output of the upstream sensor during a first engine operating condition, and supplying a second amount of electric energy, which is smaller than the first amount, to heat the upstream sensor and adjusting the air-fuel mixture based on an output of a downstream sensor located in the exhaust gas passage and downstream of the exhaust gas after-treatment device during a second engine operating condition. By adjusting the air fuel ratio based on an output of the downstream sensor in the second engine operating condition, the air-fuel mixture can be adjusted under less influence from the condensed water, because the downstream sensor is located downstream of the exhaust gas after-treatment device. Therefore, during the second engine operating condition, the air fuel ratio can be more precisely adjusted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by reading an example of embodiments in which the above aspects are used to advantage, referred to herein as the Detailed Description, with reference to the drawings wherein:

FIG. 1 shows a schematic view of an engine system in accordance with an embodiment of the present description;

FIG. 2 is a circuit diagram showing an upstream sensor which detects an oxygen concentration in the exhaust gas and has an electric heater in accordance with the embodiment;

FIG. 3 is a circuit diagram the electric heater of the upstream sensor in accordance with the embodiment;

FIG. 4 is a map which defines engine operating regions on an engine speed and desired engine torque;

FIG. 5 is a flowchart showing a routine to control the engine system in accordance with the embodiment of the present description;

FIG. 6 shows time charts of temperatures of exhaust gas oxygen sensors, heater control, and fuel control; and

FIG. 7 shows a graph of NOx emission versus air fuel ratios.

Claims

1. A method of controlling an internal combustion engine, comprising: supplying a first amount of electric energy to heat an upstream sensor located in an exhaust gas passage from said internal combustion engine and upstream of an exhaust gas after-treatment device and adjusting an air-fuel mixture supplied to said internal combustion engine based on an output of said upstream sensor during a first engine operating condition; andsupplying a second amount of electric energy, which is smaller than the first amount, to heat said upstream sensor and adjusting the air-fuel mixture based on an output of a downstream sensor located in said exhaust gas passage and downstream of said exhaust gas after-treatment device during a second engine operating condition.

2. The method as described in claim 1, wherein the air-fuel mixture is feedback controlled based on the output of said upstream or downstream sensor.

3. The method as described in claim 2, wherein said upstream and downstream sensors detect an oxygen concentration in said exhaust passage.

4. The method as described in claim 2, wherein the air-fuel mixture is feedback controlled around a stoichiometric air fuel ratio during said second engine operating condition.

5. The method as described in claim 4, wherein the air-fuel mixture is feedback controlled around an air fuel ratio leaner than the stoichiometric air fuel ratio during said first engine operating condition.

6. The method as described in claim 1, wherein the first amount of electric energy is adjusted to feedback control a temperature of said upstream sensor.

7. The method as described in claim 1, wherein the second amount of electric energy is zero.

8. The method as described in claim 1, wherein a temperature of said upstream sensor is above a predetermined temperature during said first engine operating condition and below said predetermined temperature during said second engine operating condition.

9. The method as described in claim 8, wherein said first amount of electric energy is adjusted to regulate the temperature of said upstream sensor to a temperature which is higher than said predetermined temperature.

10. The method as described in claim 1, wherein said second operating condition occurs within a predetermined period after an engine start.

11. The method as described in claim 10, wherein said predetermined period is a time period.

12. The method as described in claim 10, wherein said predetermined period is number of engine combustion events.

13. A method of controlling an internal combustion engine system having an upstream sensor located in said exhaust gas passage from an internal combustion engine and upstream of an exhaust gas after-treatment device and a downstream sensor located in said exhaust gas passage and downstream of said exhaust gas after-treatment, comprising: adjusting an air-fuel mixture supplied to said internal combustion engine by more heavily weighting an output of said downstream sensor than an output of said upstream sensor during a first predetermined period; andadjusting the air-fuel mixture by more heavily weighting the output of said upstream sensor than the output of said downstream sensor after said first predetermined period.

14. The method as described in claim 13, wherein the air fuel mixture is feedback controlled based on the output of said upstream or downstream sensor.

15. The method as described in claim 14, further comprising adjusting the air-fuel mixture without said feedback control during a second predetermined period before said predetermined period.

16. The method as described in claim 13, further comprising supplying electric energy to heat said upstream sensor after said first predetermined period.

17. The method as described in claim 16, wherein the air-fuel mixture is feedback controlled around an air fuel ratio leaner than a stoichiometric air fuel ratio based on the output of said upstream sensor after said first predetermined period.

18. An engine system comprising: an internal combustion engine;an air-fuel regulator configured to adjust an air-fuel mixture supplied to said internal combustion engine;an exhaust gas passage through which exhaust gas flows from said internal combustion engine;an exhaust gas after-treatment device arranged in said exhaust gas passage;an upstream sensor arranged in said exhaust gas passage and between said internal combustion engine and said exhaust gas after-treatment device and configured to detect an oxygen concentration in the exhaust gas and to output a first signal;an electric heater capable of heating said upstream sensor with supplied electricity;a downstream sensor arranged in said exhaust gas passage and downstream of said exhaust gas after-treatment device and configured to detect an oxygen concentration in the exhaust gas and to output a second signal; anda controller configured to control the supplied electricity to said electric heater to be greater during a first engine operating condition than during a second engine operating condition, and to control said air-fuel regulator to adjust an air-fuel mixture supplied to said internal combustion engine based on said first signal during said first engine operating condition and on said second signal during said second engine operating condition.

19. The engine system as described in claim 18, further comprising a counter configured to count an elapsed period since an engine start, and wherein said controller is further configured to determine a transition from said second engine operating condition to said first engine operating condition when said counter has counted a predetermined value.

20. The engine system as described in claim 18, wherein hydrogen is supplied to said internal combustion engine as fuel.