Method for detecting malfunctioning in a sensor

• US 20030055578A1
• Filed: 10/21/2002
• Published: 03/20/2003
• Est. Priority Date: 12/22/1999
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Strohmann, Manfred, Schulz, Udo, Straub, Detlev, Biester, Juergen, Hammel, Christof, Hartz, Martin
• Granted Patent: US 6,928,854 B2
• Time in Patent Office: Days
• US Class Current: 702/35
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for detecting a malfunction of a sensor measuring a measured quantity is provided, in which a signal-range check for the output signal of the sensor is performed, provided that the measured quantity is within a permissible range. If the measured quantity is outside the permissible range, no signal-range check is performed, but the output signal is used for detecting the measured quantity and for further calculations. The sensor may be, for example, a hot-film air-mass meter. If this is the case, the measured quantity is the drawn-in air mass, and the signal-range check is performed, provided that the engine operating state and thus the drawn-in air satisfies specifiable conditions. In addition to the signal-range check, onboard diagnoses with regard to specifiable plausibility criteria relating to the offset-drift and/or the sensitivity-drift of the sensor may also be performed.

Claims

1. A method for detecting a malfunction in the case of a sensor detecting a measured variable, whose output signal is processed in an evaluation unit and subjected to a signal-range check by comparing it to at least one specifiable limiting value, and a malfunction is detected if the output signal deviates from the limiting value in a specifiable manner, wherein the signal-range check is only implemented within a specifiable range of the measured variable and the output signal of the sensor continues to be processed even if the measured value is not within the specifiable range.

2. The method for detecting a malfunction as recited in claim 1, wherein the sensor is an air-mass flow sensor, the measured variable is the air mass drawn in by an internal combustion engine, and the signal range check and the further processing of the measured value are carried out in the control device of the internal combustion engine.

3. The method for detecting a malfunction as recited in claim 1 or 2, wherein the specifiable range of the measured variable is formed as a function of the rotational speed of the internal combustion engine.

4. The method for detecting a malfunction as recited in claim 1 or 2, wherein the specifiable range is formed as a function of the injection quantity and/or a combination of rotational speed and injection quantity.

5. The method for detecting a malfunction as recited in claim 3 or 4, wherein the signal-range check is only implemented if the injection-quantity limit is less than a specifiable quantity, this quantity being a function of speed and decreasing with an increase in speed.

6. The method for detecting a malfunction as recited in one of the preceding claims, wherein both a signal-range check-high and a signal-check-low are implemented and fault detection occurs at signal-range check-low if the measured quantity is less than a specifiable minimum value, and a fault is detected in signal-range check-high if the measured quantity is greater than a specifiable maximum value.

7. The method for detecting a malfunction as recited in one of the preceding claims, wherein, when a fault is detected within the permissible range for signal processing, the system reverts to a value previously recognized as correct, and this value is available as substitute value for further calculations.

8. The method for detecting a malfunction as recited in one of the preceding claims, wherein a plausibility check is implemented in addition to the signal-range check, but only if the signal-range check does not detect any faults, and if this additional plausibility check includes an offset-drift check and/or a sensitivity-drift check, in which further conditions, in particular voltage conditions, are monitored in specifiable operating phases of the internal combustion engine, which correspond to a rotational speed of approximately zero.

9. The method for detecting a malfunction as recited in claim 8, wherein the plausibility check of the offset drift is implemented in such a way that it checks whether the output voltage Ua of the sensor is greater than a lower limiting value UOBD,min and/or is less than an upper limiting value UOBD,max, and a fault of the offset-drift is detected and displayed if this condition has not been satisfied.

10. The method for detecting a malfunction as recited in claim 8, wherein the plausibility check of the sensitivity-drift is implemented with the exhaust-gas recirculation valve closed and the air-mass system intact;

the measured air-mass is normalized to normal conditions and the normalized air-mass is compared to at least one substitute value calculated using the general gas equation, and is detected as being too large a sensitivity drift in case of a specifiable deviation, and a corresponding fault is displayed and substitute measures are initiated, if warranted.

11. The method for detecting a malfunction as recited in claim 10, wherein a comparison to an upper and/or lower substitute value MEOBD,max, MEOBD,min is implemented when the sensitivity drift is checked for plausibility, a non-plausibility is detected in the case of a specifiable deviation.

12. The method for detecting a malfunction as recited in one of the preceding claims 8 through 11, wherein the plausibility check is continued for a specifiable time after a fault has been detected, and a definite fault is detected and a substitute function is activated only after this time has elapsed at continuing implausibility.

13. The method for detecting a malfunction as recited in one of the preceding claims 8 through 12, wherein the plausibility check is continued for a specifiable time after a malfunction has been detected, a fault remedy is adopted when plausibility is then detected.

14. A device for implementing a method for detecting a malfunction as recited in one of the preceding claims, wherein the device has at least one control device including a microprocessor, to which the quantities required for implementing the method are supplied, and which includes means for triggering the required measures and activating the substitute functions if a malfunction has been detected.