Method and diagnostic device for diagnosing a heatable exhaust gas sensor of an internal combustion engine

• US 9,062,623 B2
• Filed: 06/30/2010
• Issued: 06/23/2015
• Est. Priority Date: 07/01/2009
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Verdier, Cyril, Klein, Stefan, Lemke, Gerhard, Glashoff, Karsten, Brida, Peter, Meier, Frank, Seiler, Thomas
• Primary Examiner(s): Raevis, Robert R
• Application Number:
  US13/381,437
• Publication Number:
  US 20120167656A1
• Time in Patent Office: 1,819 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: F02D 41/1494 Control of sensor heater
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system
• CPC Class Codes: F02D 41/266 the computer being backed-up or assisted by another circuit, e.g. analogue
• CPC Class Codes: G01N 27/4175 Calibrating or checking the analyser

Abstract

A method is described for diagnosing a heatable exhaust gas sensor of an internal combustion engine, in which a predefined chronologically varying or constant voltage or a predefined chronologically varying or constant current is generated with the aid of a voltage source, the voltage or the current is applied to terminals of the exhaust gas sensor, a current or applied voltage, which flows through the voltage source when the voltage or the current is applied, is detected, and the current or the voltage is analyzed to diagnose the exhaust gas sensor. To diagnose the exhaust gas sensor, which permits a reliable and accurate diagnosis of the exhaust gas sensor and allows a statement about the type of a possibly existing error on the exhaust gas sensor, the method is executed independently of a control and/or regulating unit of the internal combustion engine, an operating temperature of the exhaust gas sensor being regulated to a predefined temperature value with the aid of a regulating element, which is separate from the control and/or regulating unit.

Claims

1. A method for diagnosing an electrochemical sensor, which is a heatable exhaust gas sensor of an internal combustion engine, the method comprising:

performing one of the following sets (a) and (b) of operations;

(a) generating a predefined chronologically varying or constant voltage with the aid of a voltage source;

applying the voltage to terminals/electrodes of the exhaust gas sensor;

detecting a current, which flows through the voltage source when the voltage is applied, is detected; and

analyzing the current to diagnose the exhaust gas sensor; and

(b) generating a predefined chronologically varying or constant current with the aid of a voltage source;

driving the current through the terminals/electrodes of the exhaust gas sensor;

applying a voltage, which is applied to the voltage source when the current is fed;

detecting the voltage, which is applied to the voltage source when the current is fed; and

analyzing a voltage to diagnose the exhaust gas sensor;

wherein the method is executed independently of a control and/or regulating unit of the internal combustion engine, and wherein an operating temperature of the exhaust gas sensor is regulated to a predefined temperature value with the aid of a regulating element, which is separate from the control and/or regulating unit, and

wherein the voltage is applied to the terminals, which are connected to electrode of a cell of the exhaust gas sensor, and a pump current is detected as the current.

2. The method of claim 1, wherein the voltage is varied step-by-step and/or in alternating directions in such a way that the voltage successively has different voltage values, and associated current values of the current are detected for at least two of these voltage values.

3. The method of claim 2, wherein a hysteresis with respect to a dependence between the applied voltage and the detected current is checked by analyzing the current values by comparing the current values with one another.

4. The method of claim 2, wherein a hysteresis with respect to a dependence between the applied voltage and a detected Nernst voltage is checked by analyzing Nernst voltage values between RE and IPN by comparing the Nernst voltage values with one another.

5. A method for diagnosing an electrochemical sensor, which is a heatable exhaust gas sensor of an internal combustion engine, the method comprising:

performing one of the following sets (a) and (b) of operations;

(a) generating a predefined chronologically varying or constant voltage with the aid of a voltage source;

applying the voltage to terminals/electrodes of the exhaust gas sensor;

detecting a current, which flows through the voltage source when the voltage is applied, is detected; and

analyzing the current to diagnose the exhaust gas sensor; and

(b) generating a predefined chronologically varying or constant current with the aid of a voltage source;

driving the current through the terminals/electrodes of the exhaust gas sensor;

applying a voltage, which is applied to the voltage source when the current is fed;

detecting the voltage, which is applied to the voltage source when the current is fed; and

analyzing a voltage to diagnose the exhaust gas sensor;

wherein the method is executed independently of a control and/or regulating unit of the internal combustion engine, and wherein an operating temperature of the exhaust gas sensor is regulated to a predefined temperature value with the aid of a regulating element, which is separate from the control and/or regulating unit, and

wherein the voltage is applied to the terminals which are connected to a trim resistor of the exhaust gas sensor.

6. The method of claim 5, wherein, as a function of a value of the trim resistor, a setpoint value for a pump current is ascertained, wherein a positive pump voltage is applied as the voltage, and wherein the exhaust gas sensor is checked as a function of the setpoint value and the pump current.

7. The method of claim 6, wherein a negative pump voltage is applied as the voltage, wherein an inverted pump current is detected as the current, and wherein it is checked whether the inverted pump current is in a predefined permissible range.

8. A method for diagnosing an electrochemical sensor, which is a heatable exhaust gas sensor of an internal combustion engine, the method comprising:

performing one of the following sets (a) and (b) of operations;

(a) generating a predefined chronologically varying or constant voltage with the aid of a voltage source;

applying the voltage to terminals/electrodes of the exhaust gas sensor;

detecting a current, which flows through the voltage source when the voltage is applied, is detected; and

analyzing the current to diagnose the exhaust gas sensor; and

(b) generating a predefined chronologically varying or constant current with the aid of a voltage source;

driving the current through the terminals/electrodes of the exhaust gas sensor;

applying a voltage, which is applied to the voltage source when the current is fed;

detecting the voltage, which is applied to the voltage source when the current is fed; and

analyzing a voltage to diagnose the exhaust gas sensor;

wherein the method is executed independently of a control and/or regulating unit of the internal combustion engine, and wherein an operating temperature of the exhaust gas sensor is regulated to a predefined temperature value with the aid of a regulating element, which is separate from the control and/or regulating unit, and

wherein the voltage is applied between a terminal of the exhaust gas sensor, which is connected to an electrode of the cell, which is an inner electrode of a pump cell, and an electrically conductive housing part of the exhaust gas sensor, a housing current is detected as the current, and it is checked whether the housing current is less than or equal to a predefined maximum value.

9. A method for diagnosing an electrochemical sensor, which is a heatable exhaust gas sensor of an internal combustion engine, the method comprising:

performing one of the following sets (a) and (b) of operations;

(a) generating a predefined chronologically varying or constant voltage with the aid of a voltage source;

applying the voltage to terminals/electrodes of the exhaust gas sensor;

detecting a current, which flows through the voltage source when the voltage is applied, is detected; and

analyzing the current to diagnose the exhaust gas sensor; and

(b) generating a predefined chronologically varying or constant current with the aid of a voltage source;

driving the current through the terminals/electrodes of the exhaust gas sensor;

applying a voltage, which is applied to the voltage source when the current is fed;

detecting the voltage, which is applied to the voltage source when the current is fed; and

analyzing a voltage to diagnose the exhaust gas sensor;

wherein the method is executed independently of a control and/or regulating unit of the internal combustion engine, and wherein an operating temperature of the exhaust gas sensor is regulated to a predefined temperature value with the aid of a regulating element, which is separate from the control and/or regulating unit, and

wherein at least one measured variable, which characterizes a cell resistance of the at least one cell of the exhaust gas sensor, which is the cell resistance of a Nernst cell of the exhaust gas sensor, is detected or ascertained, and a type of the exhaust gas sensor is ascertained as a function of the measured variable.

10. The method of claim 9, wherein at least one measuring voltage is applied to the cell as the voltage, and the current through the cell is detected as the measured variable for each measured voltage.

11. The method of claim 10, wherein at least two measuring voltages of different polarity are applied to the cell in succession.

12. The method of claim 9, wherein each measured variable is compared with a threshold value, and the type of the exhaust gas sensor is ascertained as a function of this comparison.

13. The method of claim 10, wherein, prior to the application of the measuring voltage to the cell, a cell voltage generated by the cell is detected, and at least one of the mentioned measured voltages is predefined as a function of the cell voltage.

14. A diagnostic device for checking a heatable exhaust gas sensor of an internal combustion engine, comprising:

one of the following sets (a) and (b) of components;

(a) at least one voltage source, which is configured to apply a predefined chronologically varying or constant voltage to terminals of the exhaust gas sensor;

at least one current sensor, which is configured to detect a current which flows through the voltage source when the voltage is applied; and

an analysis unit for analyzing the current to diagnose the exhaust gas sensor; and

(b) at least one voltage source, which is configured to generate a predefined chronologically varying or constant current, and which is configured for driving the current through terminals of the exhaust gas sensor;

a voltage sensor, which is configured to detect a voltage applied to the voltage source when the current is fed; and

an analysis unit, which is configured to analyze the voltage for diagnosing an electrochemical sensor;

wherein the diagnostic device is separated from a control and/or regulating unit of the internal combustion engine so that it may check the exhaust gas sensor independently of a control and/or regulating unit, the diagnostic device having a regulating element for regulating an operating temperature of the exhaust gas sensor to a predefined value, and

wherein the voltage is applied to the terminals, which are connected to electrode of a cell of the exhaust gas sensor, and a pump current is detected as the current.

15. The diagnostic device of claim 14, wherein the voltage is varied step-by-step and/or in alternating directions so that the voltage successively has different voltage values, and associated current values of the current are detected for at least two of these voltage values.

16. The diagnostic device of claim 15, wherein a hysteresis with respect to a dependence between the applied voltage and the detected current is checked by analyzing the current values by comparing the current values with one another.

17. The diagnostic device of claim 15, wherein a hysteresis with respect to a dependence between the applied voltage and a detected Nernst voltage is checked by analyzing Nernst voltage values between RE and IPN by comparing the Nernst voltage values with one another.

18. A diagnostic device for checking a heatable exhaust gas sensor of an internal combustion engine, comprising:

one of the following sets (a) and (b) of components;

(a) at least one voltage source, which is configured to apply a predefined chronologically varying or constant voltage to terminals of the exhaust gas sensor;

at least one current sensor, which is configured to detect a current which flows through the voltage source when the voltage is applied; and

an analysis unit for analyzing the current to diagnose the exhaust gas sensor; and

(b) at least one voltage source, which is configured to generate a predefined chronologically varying or constant current, and which is configured for driving the current through terminals of the exhaust gas sensor;

a voltage sensor, which is configured to detect a voltage applied to the voltage source when the current is fed; and

an analysis unit, which is configured to analyze the voltage for diagnosing an electrochemical sensor;

wherein the diagnostic device is separated from a control and/or regulating unit of the internal combustion engine so that it may check the exhaust gas sensor independently of a control and/or regulating unit, the diagnostic device having a regulating element for regulating an operating temperature of the exhaust gas sensor to a predefined value, and

wherein the voltage is applied to the terminals which are connected to a trim resistor of the exhaust gas sensor.

19. The diagnostic device of claim 18, wherein, as a function of a value of the trim resistor, a setpoint value for a pump current is ascertained, wherein a positive pump voltage is applied as the voltage, and wherein the exhaust gas sensor is checked as a function of the setpoint value and the pump current.

20. The diagnostic device of claim 19, wherein a negative pump voltage is applied as the voltage, wherein an inverted pump current is detected as the current, and wherein it is checked whether the inverted pump current is in a predefined permissible range.

21. A diagnostic device for checking a heatable exhaust gas sensor of an internal combustion engine, comprising:

one of the following sets (a) and (b) of components;

(a) at least one voltage source, which is configured to apply a predefined chronologically varying or constant voltage to terminals of the exhaust gas sensor;

at least one current sensor, which is configured to detect a current which flows through the voltage source when the voltage is applied; and

an analysis unit for analyzing the current to diagnose the exhaust gas sensor; and

(b) at least one voltage source, which is configured to generate a predefined chronologically varying or constant current, and which is configured for driving the current through terminals of the exhaust gas sensor;

a voltage sensor, which is configured to detect a voltage applied to the voltage source when the current is fed; and

an analysis unit, which is configured to analyze the voltage for diagnosing an electrochemical sensor;

wherein the diagnostic device is separated from a control and/or regulating unit of the internal combustion engine so that it may check the exhaust gas sensor independently of a control and/or regulating unit, the diagnostic device having a regulating element for regulating an operating temperature of the exhaust gas sensor to a predefined value, and

wherein the voltage is applied between a terminal of the exhaust gas sensor, which is connected to an electrode of the cell, which is an inner electrode of a pump cell, and an electrically conductive housing part of the exhaust gas sensor, a housing current is detected as the current, and it is checked whether the housing current is less than or equal to a predefined maximum value.

22. A diagnostic device for checking a heatable exhaust gas sensor of an internal combustion engine, comprising:

one of the following sets (a) and (b) of components;

(a) at least one voltage source, which is configured to apply a predefined chronologically varying or constant voltage to terminals of the exhaust gas sensor;

at least one current sensor, which is configured to detect a current which flows through the voltage source when the voltage is applied; and

an analysis unit for analyzing the current to diagnose the exhaust gas sensor; and

(b) at least one voltage source, which is configured to generate a predefined chronologically varying or constant current, and which is configured for driving the current through terminals of the exhaust gas sensor;

a voltage sensor, which is configured to detect a voltage applied to the voltage source when the current is fed; and

an analysis unit, which is configured to analyze the voltage for diagnosing an electrochemical sensor;

wherein the diagnostic device is separated from a control and/or regulating unit of the internal combustion engine so that it may check the exhaust gas sensor independently of a control and/or regulating unit, the diagnostic device having a regulating element for regulating an operating temperature of the exhaust gas sensor to a predefined value, and

wherein at least one measured variable, which characterizes a cell resistance of the at least one cell of the exhaust gas sensor, which is the cell resistance of a Nernst cell of the exhaust gas sensor, is detected or ascertained, and a type of the exhaust gas sensor is ascertained as a function of the measured variable.

23. The diagnostic device of claim 22, wherein at least one measuring voltage is applied to the cell as the voltage, and the current through the cell is detected as the measured variable for each measured voltage.

24. The diagnostic device of claim 23, wherein at least two measuring voltages of different polarity are applied to the cell in succession.

25. The diagnostic device of claim 22, wherein each measured variable is compared with a threshold value, and the type of the exhaust gas sensor is ascertained as a function of this comparison.

26. The diagnostic device of claim 23, wherein, prior to the application of the measuring voltage to the cell, a cell voltage generated by the cell is detected, and at least one of the mentioned measured voltages is predefined as a function of the cell voltage.