Method for monitoring a nitrogen oxide sensor of a motor vehicle

Abstract

The invention relates to a method for monitoring a nitrogen oxide sensor of a motor vehicle, wherein several individual fault criteria (14) assigned to the nitrogen oxide sensor are checked for their respective fulfillment and the nitrogen oxide sensor is monitored depending on the respective fulfillment of the respective fault criterion (14).

Description

[0001] The invention relates to a method for monitoring a nitrogen oxide sensor of a motor vehicle.

[0002] DE 10 2012 205 464 A1 discloses a method for diagnosing vehicle NOx sensor faults. A NOx sensor is monitored to determine whether the NOx sensor output remains above an upper threshold for more than a predetermined amount of time. If this is the case, a high-offset fault is determined for the NOx sensor.

[0003] The object of the present invention is to provide a method so that a nitrogen oxide sensor of a motor vehicle can be monitored in a particularly advantageous manner.

[0004] This object is achieved by a method having the features of patent claim 1. Advantageous embodiments of the invention are the subject of the dependent claim.

[0005] In order to create a method for monitoring a nitrogen oxide sensor (also referred to as a NOx sensor) of a motor vehicle, the invention provides that several individual error criteria assigned to the nitrogen oxide sensor, also referred to as individual criteria, are checked for their respective fulfillment, and that the nitrogen oxide sensor is monitored depending on the respective fulfillment of the respective error criterion. Compared to conventional solutions, the invention can limit the risk of false failures due to cross-sensitivity. In addition, the new method, which is a monitoring strategy for monitoring the nitrogen oxide sensor, can lower a failure threshold compared to conventional solutions.The idea underlying the invention is not only to check for compliance with one error criterion at a time, but to check the multiple individual error criteria, in particular for compliance, so that at least one or more error patterns can be checked, in particular simultaneously. Checking the individual error criteria enables particularly high robustness against false failures, so that unnecessary repair or service work and thus unnecessary visits to the workshop can be avoided. The method according to the invention enables, in particular, an assessment of the nitrogen oxide sensor, in particular with regard to whether the nitrogen oxide sensor is functioning as desired. Using a single criterion to assess whether the nitrogen oxide sensor is functioning can lead to false errors or less stringent calibrations.Multiple error conditions in the form of multiple, individual error criteria ensure more robust error detection compared to conventional solutions. This can help prevent failures, for example due to NH3 slip point. The process is implemented in software, for example, by a monitor, which is executed, for example, by an electronic computing device. The monitor and its structure are modular, so that new logic and sensors can be easily added to the monitor and to the monitoring performed by the monitor. Checking the individual error criteria for their fulfillment involves individual decisions, which enables particularly robust error detection with just one logic, especially when different failure modes are used.The monitoring is preferably designed in such a way that results of a previous, last monitoring cycle are not saved, so that a subsequent monitoring cycle, and thus the process, always starts again, in particular without taking into account the results of the releasing cycle.

[0006] In particular, the error criteria are checked, for example, using a sensor comparison and / or by MC / FC evaluation and / or by statistics. The error criteria can include a stuck-in-range error criterion and / or a drift error criterion and / or a dynamic error criterion and / or a response side of the nitrogen oxide sensor and / or a deviation and / or an offset of a value provided by the nitrogen oxide sensor from a reference value. Furthermore, at least one of the error criteria can include that a probe of the nitrogen oxide sensor is plugged in or connected, i.e., connected to an evaluation unit of the motor vehicle.

[0007] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the single figure, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0008] The drawing shows in the only figure a block diagram to illustrate a method for monitoring a nitrogen oxide sensor of a motor vehicle.

[0009] A method for monitoring a nitrogen oxide sensor of a motor vehicle is explained below with reference to the single figure. The nitrogen oxide sensor is also referred to as a NOx sensor and is arranged, for example, in an exhaust tract of the motor vehicle. Exhaust gas from an internal combustion engine of the motor vehicle, which is driven by the internal combustion engine, can flow through the exhaust tract. Any nitrogen oxides (NOx) contained in the exhaust gas can be detected by means of the nitrogen oxide sensor. The nitrogen oxide sensor can, for example, provide a sensor signal, also referred to as a measurement signal, which characterizes the nitrogen oxides contained in the exhaust gas detected, i.e. measured, by the nitrogen oxide sensor. For example, the motor vehicle comprises an electronic computing device which is or comprises an evaluation unit.The electronic computing device can, for example, receive the sensor signal and thereby determine the nitrogen oxides contained in the exhaust gas detected by the nitrogen oxide sensor. For example, the nitrogen oxide sensor comprises a probe by means of which the nitrogen oxides in the exhaust gas can be detected. If, for example, the probe is connected, in particular electrically, to the evaluation unit or the electronic computing device, then the probe is connected. However, due to incorrect installation or damage, for example, it may happen that the probe is not connected to the evaluation unit, meaning that the electronic computing device cannot receive correct values ​​for any nitrogen oxides contained in the exhaust gas via the nitrogen oxide sensor. A state in which the probe is not connected to the evaluation unit can be an undesirable error condition.It is advantageous to determine this fault condition, as well as any other fault conditions of the nitrogen oxide sensor. For this purpose, the aforementioned method for monitoring the nitrogen oxide sensor is performed.

[0010] For example, the method is carried out by means of the electronic computing device.

[0011] The method begins at block 10. At block 12, several individual error criteria 14 assigned to the nitrogen oxide sensor, also referred to as individual criteria, are checked for their respective fulfillment. At block 16, the nitrogen oxide sensor is monitored depending on the respective fulfillment of the respective error criterion. For example, an error state, i.e. a malfunction of the nitrogen oxide sensor, is determined if at least one, several, or all error criteria are met, in particular simultaneously. This enables robust monitoring of the nitrogen oxide sensor, in particular to the extent that an error state of the nitrogen oxide sensor is only determined if the nitrogen oxide sensor is actually malfunctioning. This can avoid unnecessary repair work and visits to the workshop.At the same time, advantageous and, in particular, low-emission operation of the internal combustion engine can be ensured. List of reference symbols 10 blocks 12 blocks 14 error criteria 16 blocks QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2012 205 464 A1

[0002]

Claims

[1] Method for monitoring a nitrogen oxide sensor of a motor vehicle, characterized by that several individual error criteria (14) assigned to the nitrogen oxide sensor are checked for their respective fulfillment and the nitrogen oxide sensor is monitored depending on the respective fulfillment of the respective error criterion (14). [2] Method according to claim 1, characterized by , that: - one of the error criteria (14) is a stuck-in-range error criterion; and / or - one of the error criteria (14) is a drift error criterion; and / or - one of the error criteria (14) is a dynamic error criterion; and / or - one of the error criteria (14) comprises that a probe of the nitrogen oxide sensor is connected to an evaluation unit of the motor vehicle; and / or. - one of the error criteria (14) comprises a response time of the nitrogen oxide sensor; and / or - one of the error criteria (14) comprises a deviation and / or an offset of a value provided by the nitrogen oxide sensor from a reference value.

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