Combustible-gas sensor, diagnostic device for intake-oxygen concentration sensor, and air-fuel ratio control device for internal combustion engines

• US 20020139360A1
• Filed: 03/05/2002
• Published: 10/03/2002
• Est. Priority Date: 03/05/2001
• Status: Active Grant

• Current Assignee: Nippon Soken, Inc. (DENSO Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Nippon Soken, Inc. (DENSO Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Hyoudo, Yoshihiko, Sato, Fumihiko, Yoshioka, Mamoru, Takeuchi, Takayuki, Matsubara, Takuji, Daido, Shigeki, Oyama, Naohisa
• Granted Patent: US 6,739,177 B2
• Time in Patent Office: Days
• US Class Current: 123/698
• CPC Class Codes: F02D 41/0037 for diagnosing the engine diagnosis of purge control systems F02M25/0809
• CPC Class Codes: F02D 41/0042 Controlling the combustible mixture as a function of the canister purging, e.g. control of injected fuel to compensate for deviation of air fuel ratio when purging
• CPC Class Codes: F02D 41/144 Sensor in intake manifold
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system
• CPC Class Codes: F02M 25/08 adding fuel vapours drawn from engine fuel reservoir electrical control of purge system F02D41/003
• CPC Class Codes: F02M 26/19 Means for improving the mixing of air and recirculated exhaust gases, e.g. venturis or multiple openings to the intake system
• CPC Class Codes: F02M 26/46 for determining the characteristics of gases, e.g. composition

Abstract

Correction of a fuel injection amount in an internal combustion engine during purge of evaporative fuel is performed on the basis of an output from an intake-oxygen concentration sensor disposed in an intake passage of the internal combustion engine. If the amplitude of fluctuations in engine speed becomes equal to or greater than a predetermined value, it is determined that there is an anomaly in engine output. In addition, if an anomaly in engine output is detected during purge and if no anomaly in engine output is detected during stoppage of purge, an ECU determines that an anomaly has occurred in the intake-oxygen concentration sensor, cancels correction of the fuel injection amount based on an output from the intake-oxygen concentration sensor during purge, and corrects the fuel injection amount on the basis of outputs from exhaust-gas air-fuel ratio sensors.

Claims

1. An air-fuel ratio control device for internal combustion engines, comprising:

an evaporative fuel concentration sensor that is disposed in an intake passage of an internal combustion engine so as to detect a concentration of evaporative fuel contained in intake gas;

a purging device that supplies evaporative fuel in a fuel tank to the intake passage upstream of the evaporative fuel concentration sensor;

a vapor amount calculation portion that calculates an amount of the evaporative fuel contained in intake gas on the basis of a value detected by the evaporative fuel concentration sensor;

an intake-side purge control portion that performs intake-side purge control so as to correct a fuel supply amount of the engine on the basis of a value detected by the evaporative fuel concentration sensor while supplying the intake passage with evaporative fuel;

an anomalous output detection portion that detects an anomaly in engine output on the basis of a parameter regarding engine output;

a determination portion that determines whether or not the anomaly in engine output detected during the performance of the intake-side purge control has occurred as a result of the intake-side purge control; and

a sensor anomaly determination portion that determines that there is an anomaly in the evaporative fuel concentration sensor if it is determined that the anomaly in engine output has occurred as a result of the intake-side purge control.

2. The control device according to claim 1, wherein

the determination portion determines whether or not the anomaly in engine output has occurred as a result of the intake-side purge control, depending on whether or not the anomaly in engine output is detected during stoppage of the intake-side purge control.

3. The control device according to claim 1, wherein

the parameter regarding engine output is engine speed.

4. The control device according to claim 1, wherein

the parameter regarding engine output is exhaust-gas air-fuel ratio of the internal combustion engine.

5. The control device according to claim 1, further comprising:

an exhaust-gas air-fuel ratio sensor that is disposed in an exhaust passage of the internal combustion engine so as to output a signal corresponding to an exhaust-gas air-fuel ratio;

an exhaust-side air-fuel ratio control portion that controls an air-fuel ratio of mixture supplied to the internal combustion engine on the basis of an output from the exhaust-gas air-fuel ratio sensor; and

an intake-side purge control cancellation portion that cancels the intake-side purge control upon detection of an anomaly in the evaporative fuel concentration sensor.

6. The control device according to claim 5, further comprising:

a purge stoppage portion that stops purge of evaporative fuel if the anomaly in engine output is detected under a circumstance where the evaporative fuel is purged from the purging device, where the intake-side purge control has been canceled, and where the fuel supply amount is being corrected on the basis of an output from the exhaust-gas air-fuel ratio sensor.

7. The control device according to claim 1, further comprising:

a sensor-characteristics anomaly determination portion that determines whether or not there is an anomaly in output characteristics of the evaporative fuel concentration sensor if the sensor anomaly determination portion determines that there is an anomaly in the evaporative fuel concentration sensor; and

an intake-side purge control permission portion that permits the performance of the intake-side purge control if no anomaly is detected in the output characteristics.

8. An air-fuel ratio control device for internal combustion engines, comprising:

an evaporative fuel concentration sensor that is disposed in an intake passage of an internal combustion engine so as to detect a concentration of evaporative fuel contained in intake gas;

a purging device that supplies evaporative fuel in a fuel tank to the intake passage upstream of the evaporative fuel concentration sensor;

an intake-side purge control portion that performs intake-side purge control so as to correct a fuel supply amount of the engine on the basis of a value detected by the evaporative fuel concentration sensor while supplying the intake passage with evaporative fuel;

an exhaust-gas air-fuel ratio sensor that is disposed in an exhaust passage of the internal combustion engine so as to output a signal corresponding to an exhaust-gas air-fuel ratio;

an exhaust-side purge control portion that performs exhaust-side purge control so as to control an air-fuel ratio of mixture supplied to the internal combustion engine on the basis of a value detected by the exhaust-gas air-fuel ratio sensor while supplying the intake passage with evaporative fuel;

a system anomaly determination portion that determines whether or not there is an anomaly in a system that is required for the performance of the intake-side purge control; and

a control change portion that cancels the intake-side purge control and starting or continuing the exhaust-side purge control if an anomaly in the system is detected.

9. The control device according to claim 8, further comprising:

an intake pressure sensor that is disposed in the intake passage so as to generate an output corresponding to an intake pressure;

an intake pressure estimation portion that estimates the intake pressure on the basis of a state of the internal combustion engine;

a sensor output correction portion that corrects an output from the evaporative fuel concentration sensor on the basis of an output from the intake pressure sensor if the system anomaly determination portion determines that there is not an anomaly in the intake pressure sensor, as the system, and performs pressure-based correction of an output from the evaporative fuel concentration sensor on the basis of an estimated value of the intake pressure if the system anomaly determination portion determines that there is an anomaly in the intake pressure sensor, as the system; and

controller that continues the intake-side purge control on the basis of a result of correction made by the sensor output correction portion if the system anomaly determination portion determines that there is not a anomaly in the evaporative fuel concentration sensor despite the occurrence of an anomaly in the intake pressure sensor,

wherein

the evaporative fuel concentration sensor has output characteristics that are dependent on pressure.

10. The control device according to claim 8, further comprising:

a purge control valve that controls an amount of purge of evaporative fuel flowing from the purging device to the intake passage; and

a controller that continues correction of the fuel supply amount on the basis of a value detected by the evaporative fuel concentration sensor as a processing of the intake-side purge control if the system anomaly determination portion that there is not an anomaly in the evaporative fuel concentration sensor despite the occurrence of an anomaly in the purge control valve

11. The control device according to claim 10, wherein

the controller attempts to stop purge of the evaporative fuel if the exhaust-gas air-fuel ratio is out of an allowable range after continuation of correction of the fuel supply amount on the basis of a value detected by the evaporative fuel concentration sensor.

12. The control device according to claim 10, further comprising:

the controller attempts to stop purge of the evaporative fuel if there is an anomaly in the purge control valve and if there is an anomaly in the evaporative fuel concentration sensor.

13. The control device according to claim 8, wherein

the system anomaly determination portion determines that there is an anomaly in the evaporative fuel concentration sensor if the anomaly in engine output is not detected on the basis of the parameter regarding engine output during stoppage of the intake-side purge control and if the anomaly in engine output is detected on the basis of the parameter regarding engine output during the performance of the intake-side purge control.

15. The malfunction determination device according to claim 14, wherein

the determination portion stores an output from the intake-oxygen concentration sensor at the time when the intake pressure sensor detects a first pressure as a first sensor output and an output from the intake-oxygen concentration sensor at the time when the intake pressure detection means detects a second pressure as a second sensor output, calculates a characteristic value representing change characteristics of sensor output with respect to pressure on the basis of a ratio of a difference between the first and second sensor outputs to a difference between the first and second pressures, and determines that there is a malfunction in the intake-oxygen concentration sensor if the calculated characteristic value is equal to or greater than a predetermined upper-limit value or equal to or smaller than a predetermined lower-limit value.

16. The malfunction determination device according to claim 15, wherein

the upper-limit value is set on the basis of a tolerance for dispersion in the output from the intake-oxygen concentration sensor among individual products, and

the lower-limit value is set on the basis of an amount of change in the concentration of oxygen contained in intake gas during recirculation of exhaust gas into the intake passage of the engine, on the basis of an amount of change in the concentration of oxygen contained in intake gas during introduction of hydrocarbon components into the intake passage of the engine, or on the basis of both of them.

17. The malfunction determination device according to claim 16, wherein

the lower-limit value is set on the basis of the tolerance for dispersion in the output from the intake-oxygen concentration sensor among individual products during stoppage of both recirculation of exhaust gas into the intake passage of the engine and introduction of hydrocarbon components into the intake passage of the engine.

18. The malfunction determination device according to claim 17, wherein

the determination portion calculates the characteristic value again during stoppage of both recirculation of exhaust gas into the intake passage of the engine and introduction of hydrocarbon components into the intake passage of the engine if it is determined that there is a malfunction in the intake-oxygen concentration sensor on the ground that the characteristic value has become equal to or smaller than the lower-limit value during recirculation of exhaust gas or introduction of hydrocarbon components into the intake passage of the engine while the engine is in operation, and determines whether or not there is a malfunction in the intake-oxygen concentration sensor, on the basis of the calculated characteristic value.

20. The combustible-gas sensor according to claim 19, wherein:

the correction portion has a relation between a pressure measured in advance in the atmosphere of the reference gas and a sensor output at the pressure stored as a map, calculates a ratio of an output value of the sensor device at a given pressure to be measured to the sensor output at the given pressure as a reference output value, on the based of the map, and calculates a concentration of combustible gas from the ratio.

14. A malfunction determination device for determining whether or not there is a malfunction in an intake-oxygen concentration sensor that is disposed in an intake passage of an internal combustion engine so as to generate an output corresponding to a concentration of oxygen contained in intake gas of the engine, comprising:

an intake pressure sensor that is disposed so as to detect an intake pressure of the engine; and

a determination portion that determines whether or not there is a malfunction in the intake-oxygen concentration sensor, depending on whether or not a predetermined relation between amount of change in intake pressure of the engine and amount of change in the output from the intake-oxygen concentration sensor is established when the intake pressure of the engine changes.

19. A combustible-gas sensor that is equipped with a sensor device having a pair of electrodes which are formed on the surface of an oxygen-ion conductor and one of the electrodes is disposed in a space where measurement-target gas containing combustible gas and oxygen exists and that detects a concentration of combustible gas on the basis of a change in the concentration of oxygen contained in measurement-target gas resulting from an oxidizing reaction of combustible gas, comprising:

a correction portion that corrects a deviation in sensor output resulting from a pressure of measurement-target gas, on the basis of a sensor output in the atmosphere of a reference gas.

21. A combustible-gas sensor that is equipped with a sensor device having a pair of electrodes which are formed on the surface of an oxygen-ion conductor and one of the electrodes is disposed in a space where measurement-target gas containing combustible gas and oxygen exists and that detects a concentration of combustible gas on the basis of a change in the concentration of oxygen contained in measurement-target gas resulting from an oxidizing reaction of combustible gas, comprising:

a correction portion corrects a deviation in sensor output resulting from a pressure of the measurement-target gas, on the basis of a map of a relation between a flow speed of measurement-target gas and a sensor output.

22. The combustible-gas sensor according to claim 21, wherein

the correction portion determines that the flow speed of measurement-target gas affects the output only if the flow speed of measurement-target gas is lower than a predetermined value, and then performs to correct the deviation in the sensor output.

24. The combustible-gas sensor according to claim 23, wherein

the correction portion corrects the sensor output through multiplication of a predetermined value that is set in advance in accordance with the pressure-change speed, until the pressure-change speed becomes equal to or lower than the predetermined speed.

25. The combustible-gas sensor according to claim 23, wherein

the correction portion estimates the concentration of combustible gas on the basis of the rate of change in concentration of combustible gas and the sensor output during the period, until the pressure-change speed becomes equal to or lower than the predetermined speed.

23. A combustible-gas sensor that is equipped with a sensor device having a pair of electrodes which are formed on the surface of an oxygen-ion conductor and one of the electrodes is disposed in a space where measurement-target gas containing combustible gas and oxygen exists and that detects a concentration of combustible gas on the basis of a change in the concentration of oxygen contained in measurement-target gas resulting from an oxidizing reaction of combustible gas, comprising:

a correction portion that corrects a sensor output on the basis of a pressure-change speed or a rate of change in concentration of combustible gas during a certain period if the pressure-change speed remains higher than a predetermined speed for the period or more.