Method for fault diagnosis of a temperature sensor in a motor vehicle and control unit

Abstract

The invention relates to a method for fault diagnosis (100) of a temperature sensor in a motor vehicle, the method comprising the following steps: (a) determining whether a dynamic operating phase (101) or a static operating phase (102) is present; (b) performing the fault diagnosis (100) of the temperature sensor when a dynamic operating phase (101) is present, wherein performing the fault diagnosis (100) comprises: (ba) receiving at least two values, wherein the at least two values ​​are each representative of a measured value (109) taken by the temperature sensor during the dynamic operating phase (101); (bb) detecting a fault of the temperature sensor if a difference between the two received values ​​is less than a predetermined threshold. The invention further relates to a corresponding control unit and computer program.

Description

TECHNICAL AREA

[0001] The present disclosure relates to methods for fault diagnosis of a temperature sensor in a motor vehicle, for example a temperature sensor arranged in an exhaust system of the motor vehicle, as well as corresponding control units and computer program products. BACKGROUND OF THE INVENTION

[0002] Sensor malfunctions in motor vehicles must be reliably detected to ensure dependable and efficient vehicle operation. For example, such malfunctions can be identified through on-board diagnostics (OBD), and the OBD system can provide the relevant information for reading. Various sensor diagnostics include so-called "stuck" diagnostics, where the sensor fails to register changes in the measured values ​​or registers them insufficiently. However, such diagnostics can often only be performed under precisely defined conditions, such as at the beginning of a driving cycle. SUMMARY AND FORMS OF EXECUTION

[0003] It is therefore an objective of the present disclosure to provide a particularly accurate and reliable method for fault diagnosis of a motor vehicle sensor, for example, a temperature sensor in an exhaust system. In particular, such a method should be executable multiple times during a driving cycle, ideally continuously throughout the driving cycle.

[0004] This problem is solved by a method for fault diagnosis of a temperature sensor in a motor vehicle, by a control unit, and by a computer program according to the independent patent claims. Advantageous embodiments and further developments are described in the respective dependent claims, the following description, and the drawings.

[0005] Thus, according to a first aspect, a method for fault diagnosis of a temperature sensor in a motor vehicle is provided. The method comprises the following steps: (a) Determining whether the motor vehicle is in a dynamic or a static operating phase; (b) Performing fault diagnosis of the temperature sensor when a dynamic operating phase is present. Performing fault diagnosis comprises: (ba) Receiving at least two values, each of which is representative of a measurement taken by the temperature sensor during the dynamic operating phase; (bb) Determining a fault of the temperature sensor if the difference between the two received values ​​is less than a predetermined threshold.

[0006] According to another aspect, a control unit is provided which is set up to carry out the procedure described above.

[0007] According to another aspect, a computer program is provided which includes commands that, when executed by a computer, cause it to carry out the procedure described above.

[0008] In the context of this disclosure, a "temperature sensor" can mean any sensor that provides a measured value representative of a temperature. The sensor can therefore measure the temperature directly as temperature or indirectly via measured values ​​correlated with the temperature. The temperature can be in the immediate vicinity of the sensor or at the sensor itself.

[0009] In the context of the disclosure, an "operating phase" of the vehicle may be defined based on the presence of certain operating conditions. Each operating phase may be delimited by a respective start time, from which the operating conditions are met, and a respective end time, from which the operating conditions are no longer met. A particular operating phase may occur multiple times during a driving cycle, for example, separated by one or more operating phases of a different type.

[0010] In the context of this disclosure, a "dynamic operating phase" can be defined as an operating phase of the motor vehicle in which a load change occurs, in particular either an increase or a decrease in load. Such a load change can occur if a state parameter correlated with the load undergoes a corresponding change, in particular a change that is greater than a predefined threshold. The state parameter correlated with the load change can, for example, be an operating temperature, in particular an operating temperature in a subsystem of the vehicle, such as an exhaust system. It can be a modeled operating temperature. The modeled operating temperature can, but need not, model the temperature measured by the temperature sensor.

[0011] Alternatively or additionally, a dynamic operating phase can be defined by a change in the operating temperature of the vehicle, in particular of a subsystem of the vehicle, for example the exhaust system.

[0012] In the context of this disclosure, a "static operating phase" can be defined as an operating phase of the motor vehicle in which no or only a slight load change occurs. This can be the case when a state parameter correlated with the load undergoes no or only a slight change, in particular a change that is smaller than a predefined threshold. The predefined threshold for determining the static operating phase may, but need not, coincide with the predefined threshold for determining the dynamic operating phase. As described above, the state parameter correlated with the load change can, for example, be an operating temperature, in particular an operating temperature in a subsystem of the vehicle, such as an exhaust system. It can be a modeled operating temperature.The modeled operating temperature can, but does not have to, model the temperature measured by the temperature sensor.

[0013] Alternatively or additionally, a static operating phase can be defined by a change in the operating temperature of the vehicle, in particular of a subsystem of the vehicle, for example the exhaust system.

[0014] According to one embodiment, in addition to the static operating phase and the dynamic operating phase, there is at least one further operating phase, for example, a transition phase. Alternatively, the static and dynamic operating phases may be the only possible operating phases.

[0015] According to one embodiment, the motor vehicle has an internal combustion engine, and the static and dynamic operating phases relate to the internal combustion engine. In particular, they relate to the load of the internal combustion engine.

[0016] According to one embodiment, fault diagnosis is only performed when a dynamic operating phase is present.

[0017] According to one embodiment, the fault diagnosis is carried out while the motor vehicle is being driven, in particular at a speed of the vehicle that deviates from zero, especially at a speed greater than or equal to ten kilometers per hour.

[0018] According to one embodiment, the fault diagnosis is performed multiple times during a driving cycle of the vehicle. A driving cycle can be defined by starting the engine and subsequently switching it off.

[0019] According to one embodiment, proper or error-free operation of the sensor is determined if the difference between the two received values ​​is greater than the predefined threshold or greater than a further predefined threshold that is itself greater than the predefined threshold. In the latter case, there would be an intermediate range in which no clear statement can be made as to whether an error has occurred or whether the sensor is operating correctly.

[0020] The described procedure and the corresponding control unit can be advantageous for enabling repeated fault diagnosis of the temperature sensor during a driving cycle. Ideally, the temperature sensor diagnosis can be performed continuously throughout the entire driving cycle, particularly to detect faults that only occur after the start of the driving cycle. This allows for a rapid response to such faults, preventing more serious damage to the vehicle. A fault to be detected could, for example, be a "stuck" or excessively slow temperature measurement.

[0021] For multiple or even continuous fault diagnosis, it may be necessary to distinguish between phases of the driving cycle during which reliable diagnosis is possible and phases during which diagnosis is not possible, or at least not always reliable. Such a distinction can be ensured by identifying dynamic and static operating phases. Accordingly, fault diagnosis is advantageously performed during, and in particular exclusively during, the dynamic operating phases.

[0022] Dynamic operating phases can be characterized, for example, by a temperature change, particularly a significant temperature change. Accordingly, a fault in the temperature measurement and / or the temperature sensor can be diagnosed if the temperature sensor readings do not reflect the aforementioned temperature change during the dynamic operating phase. This can be determined, for example, by calculating the difference between temperature values ​​measured by the temperature sensor during the dynamic operating phase.

[0023] For example, after a successful diagnostic check at the start of a driving cycle, during which no fault is detected, the temperature sensor may "get stuck" at a fixed value or measure temperature changes very slowly compared to the actual change. Such temperature measurement errors can be caused, for example, by an electrical fault, such as a power failure, connection problems, or external interference that causes changes in the sensor's position or leads to the sensor becoming at least partially dislodged from its mounting. Currently, such errors cannot be detected in a timely manner.

[0024] According to one embodiment, the method further includes modeling a temperature, for example, measured values ​​from the temperature sensor and / or a temperature at the temperature sensor and / or a temperature of a subsystem of the motor vehicle which includes the temperature sensor, for example, an exhaust system. The modeled temperature can relate to the position of the temperature sensor or to another position, in particular another position within the same subsystem.

[0025] According to one embodiment, the presence of the dynamic or static operating phase is determined based on a modeled temperature and / or based on a further temperature measured by another temperature sensor. The modeled temperature can be a temperature near the sensor or at the temperature sensor itself. The further temperature sensor can be arranged in the same subsystem as the temperature sensor. Such an embodiment can be advantageous because it allows for a quick and easy determination of when a diagnosis is appropriate. The described procedure can be particularly superior to a direct comparison between the modeled and measured temperatures.

[0026] According to one embodiment, the dynamic operating phase is indicative of a load change or a change in the engine load point of a motor vehicle engine, in particular an internal combustion engine of the motor vehicle. The load change or change in the engine load point can be characterized, for example, by at least one of the following operating modes: acceleration, fuel cut-off, accelerating, decelerating, starting, stopping, and shifting and clutch engagement.

[0027] According to one embodiment, no fault diagnosis of the temperature sensor is performed when the static operating phase is present. Such an embodiment can be advantageous because the diagnostic method described in this disclosure does not detect any faults, or does not reliably detect them, during a static operating phase.

[0028] According to one embodiment, the difference between a previous maximum value of the received values ​​during the dynamic operating phase and a previous minimum value of the received values ​​during the dynamic operating phase is determined as the difference between the two received values. The maximum value and / or the minimum value can refer to the entire current dynamic operating phase or only to a portion of it. For example, the maximum value and / or the minimum value of all values ​​received so far during the dynamic phase can be calculated. Once the difference exceeds the predefined threshold, the diagnostic process can then be terminated. Alternatively or additionally, after the dynamic phase has ended, the maximum value and / or the minimum value of all values ​​received during the entire dynamic phase can be calculated, and the corresponding difference can be used for the diagnostic process.

[0029] According to one embodiment, the previous minimum and / or maximum values ​​are determined using a trailing pointer. The trailing pointer can be implemented as software and / or hardware. Such an embodiment can be advantageous because a trailing pointer can simplify the calculation of the difference and, for example, save memory. Furthermore, a trailing pointer can be easily reset. The proposed method may be particularly suitable for the use of a trailing pointer.

[0030] According to one embodiment, one or more diagnostic parameters are reset at or after the end of the dynamic operating phase. The diagnostic parameters can be reset at the beginning or during the subsequent static operating phase. For example, the previous minimum and / or maximum values ​​can be reset, for instance, to the value currently received from the temperature sensor, in particular to the currently measured temperature value. Alternatively or additionally, the drag pointers can be reset.

[0031] According to one embodiment, the start and / or end of the dynamic operating phase is determined by a predetermined delay or waiting period. It may be necessary that the conditions for a dynamic or static operating phase be met for the duration of the delay or waiting period before the start or end of the dynamic operating phase is determined. The waiting periods at the beginning and end of the dynamic operating phase may differ or be the same.

[0032] Such an embodiment can be advantageous to ensure that, on the one hand, small dynamic changes are not already taken into account for fault diagnosis, which would lead to a false fault being detected, and on the other hand, short static intermediate phases do not already define an end of the dynamic phase, which would prematurely terminate the fault diagnosis and possibly also lead to a false fault being detected.

[0033] According to one embodiment, the respective predefined waiting times are constant. Such an embodiment can be advantageous because a simple and computationally inefficient waiting time is defined, which nevertheless at least partially prevents the previously described erroneous diagnoses.

[0034] According to one embodiment, the respective predefined waiting times depend on at least one of the following parameters: the load of the vehicle's internal combustion engine, the engine speed, and the mass flow rate through the vehicle's exhaust system. In other words, the waiting time reflects a system characteristic. Such an embodiment can be advantageous for reducing the risk of incorrect diagnoses.

[0035] According to one embodiment, at least one of the following situations is defined as a fault: a stuck measurement by the temperature sensor, a measurement by the temperature sensor that is too slow, a change in the position of the temperature sensor, at least partial dislodging of the temperature sensor from a mounting, for example, at least partial unscrewing, an electrical fault, and a connection problem. A stuck measurement can mean that a value output by the temperature sensor does not change or remains within a range of values ​​that is significantly smaller than a predetermined measuring range of the temperature sensor, in particular at most half as large.

[0036] According to one embodiment, the sensor is arranged in one of the following systems: an exhaust system, an internal combustion engine, a vehicle battery, and in particular, a thermal management system of the battery. The temperature sensor can be configured to measure an exhaust gas temperature. Alternatively, the temperature sensor can be configured to monitor the temperature of the vehicle battery. Even in the case of battery temperature monitoring, a corresponding heat generation is to be expected when the load changes.

[0037] According to one embodiment, the threshold value depends on the modeled temperature and / or on the additional temperature measured by the further temperature sensor. Alternatively or additionally, the threshold value can depend on the sensor's position, for example, in an exhaust system. The threshold value can also depend on whether the modeled temperature and / or the temperature measured by the further temperature sensor rises or falls after the start of the dynamic phase. Such an embodiment can be advantageous because fault diagnosis can be improved through such dependencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further advantages and beneficial designs and further developments of the method, the control unit and the computer program result from the following exemplary embodiments shown in connection with the figures.

[0039] They show: Fig. 1 and Fig. 2 each a comparison of a measured temperature and a modeled temperature during several dynamic and static operating phases within the framework of an embodiment of a method for fault diagnosis of a temperature sensor in a motor vehicle.

[0040] Identical, similar, or similarly effective elements are marked with the same reference symbols in the figures. In some figures, individual reference symbols have been omitted for clarity. The figures and the relative sizes of the elements depicted within them are not to be considered to scale. Rather, individual elements may be exaggerated for better representation and / or comprehensibility. DETAILED DESCRIPTION OF EXAMPLES OF EXECUTION

[0041] Fig. 1 and Fig. Figure 2 shows a comparison of a measured temperature (109) and a modeled temperature (110) during several dynamic and static operating phases (101, 102). Aspects of a fault diagnosis procedure (100) for a temperature sensor in the exhaust system of a motor vehicle are depicted. The procedure comprises the following steps: (a) determining whether a dynamic operating phase (101) or a static operating phase (102) of the motor vehicle is present; (b) performing the fault diagnosis (100) of the temperature sensor when a dynamic operating phase (101) is present.Performing the fault diagnosis (100) includes at least the following steps: (ba) Receiving at least two values, where the at least two values ​​are each representative of a measured value (109) taken by the temperature sensor during the dynamic operating phase (101); (bb) Detecting a fault of the temperature sensor if the difference between the two received values ​​is less than a specified threshold.

[0042] Fig. 1 and Fig. Figure 2 shows a time course of the temperature measured by the temperature sensor (109) and a corresponding modeled temperature (110). First, after a certain delay, during which the modeled temperature (110) already undergoes a noticeable change, a dynamic operating phase is detected (103). The dynamic operating phase (101) is characterized by a significant change in the modeled temperature value (110). From the beginning of the dynamic operating phase (101), the minimum previously measured temperature value (107) and the maximum previously measured temperature value (108) are recorded. If the difference between the maximum temperature value (108) and the minimum temperature value (107) exceeds the predefined threshold value (105), the sensor has passed the diagnostic test, i.e., no fault was detected (111).

[0043] If the modeled temperature value (110) no longer changes or only changes slightly, the end of the dynamic phase is detected again after a certain time delay, or the beginning of the subsequent static phase is detected. After the end of the dynamic phase and / or during the subsequent static phase, diagnostic parameters are reset (113), in particular the maximum measured temperature value (108) and the minimum measured temperature value (107) are reset, for example, to the currently measured temperature value. The subsequent static phase (102) lasts until a dynamic operating phase is detected again (103), as described above. Any number of dynamic operating phases (101) and static operating phases (102) can follow one another during a driving cycle.During the dynamic operating phases (101) a fault diagnosis can be carried out, while the diagnosis is inactive during the static operating phases (102).

[0044] Fig. 1 and Fig. The two differ in that in Fig. 1. A proper or error-free system is illustrated, while in Fig. 2 illustrates a faulty system. Also in Fig. 2. The temperature sensor passes the first diagnosis during the first dynamic operating phase (101). However, during the subsequent second diagnosis during the second dynamic operating phase (101), the difference between the maximum temperature value (108) and the minimum temperature value (107) during this operating phase remains below the specified threshold. Therefore, an error is detected (112).

[0045] Incremental and decremental diagnostics, as just described, can be performed, for example, during engine start-up in cold temperatures and also while driving. They are used to detect a malfunction of the temperature sensor, such as when the sensor is unable to measure a temperature increase because it has "gotten stuck" at a constant value. This could be caused by the sensor having become at least partially detached from the exhaust pipe, for example, due to system vibrations. This could result in the sensor measuring only the atmospheric temperature or ambient temperature instead of the exhaust gas temperature.

[0046] In summary, the following steps are introduced to facilitate the detection of sensor malfunctions, such as stuck or too slow temperature measurements, throughout the driving cycle.

[0047] First, dynamic conditions are determined (103). The diagnostic system is active during situations where the engine load point increases, such as during acceleration, or decreases, such as when the fuel supply is cut off. A turn-on delay is applied, after which the diagnostic system is activated to ensure that small dynamic changes are not detected, which could lead to a false fault detection. Once the system is in a dynamic state for a calibratable turn-off delay, the diagnostic condition is reset. The above steps can be repeated continuously throughout the driving cycle.

[0048] Secondly, static conditions are determined (104). The diagnostics are inactive during these conditions to prevent a false fault detection. A shutdown delay for the dynamic state is provided, after which the deactivation of the diagnostics is initiated and the diagnostics condition is reset.

[0049] The invention is not limited to the exemplary embodiments described therein. Rather, the invention encompasses every new feature as well as every combination of features, which in particular includes every combination of features in the exemplary embodiments and claims. REFERENCE MARK 100 fault diagnosis 101 dynamic operating phase / diagnostics active 102 Static operating phase / Diagnosis inactive 103 dynamic operating phase detected 104 static operating phase detected 107 Minimum value 108 Maximum value 109 measured temperature 110 modeled temperature 111 No error detected 112 errors detected 113 diagnostic parameters reset 114 Exhaust gas temperature 115 Time

Claims

[1] Method for fault diagnosis (100) of a temperature sensor in a motor vehicle, the method comprising the following steps: Determining whether a dynamic operating phase (101) or a static operating phase (102) is present; Carrying out the fault diagnosis (100) of the temperature sensor when a dynamic operating phase (101) is present, wherein carrying out the fault diagnosis (100) comprises: Receiving at least two values, wherein the at least two values ​​are each representative of a measured value (109) measured by the temperature sensor during the dynamic operating phase (101); Detect a temperature sensor error if the difference between the two received values ​​is less than a specified threshold. [2] Method according to the preceding claim, wherein the presence of the dynamic operating phase (103) or the static operating phase (102) is determined based on a modeled temperature (110) and / or based on a temperature measured by a further temperature sensor. [3] Method according to one of the preceding claims, wherein the dynamic operating phase (103) is indicative of a load change of an engine of the motor vehicle. [4] Method according to one of the preceding claims, wherein no fault diagnosis (100) of the temperature sensor is carried out when the static operating phase (104) is present. [5] Method according to one of the preceding claims, wherein a difference between a previous maximum value (108) of the received values ​​during the dynamic operating phase (101) and a previous minimum value (107) of the received values ​​during the dynamic operating phase (101) is determined as the difference between the two received values. [6] Method according to the preceding claim, wherein the previous minimum value (107) and / or the previous maximum value (108) are determined by means of a trailing pointer. [7] Method according to one of the preceding claims, wherein after an end of the dynamic operating phase (101) one or more diagnostic parameters are reset, in particular the previous minimum value (107) and / or the previous maximum value (108). [8] Method according to one of the preceding claims, wherein a start of the dynamic operating phase (103) and / or an end of the dynamic operating phase (104) is determined with a respective predetermined waiting time. [9] Method according to the preceding claim, wherein the respective predetermined waiting times are constant. [10] Method according to one of claims 1 to 8, wherein the respective predetermined waiting times depend on at least one of the following parameters: a load of an internal combustion engine of the motor vehicle, a speed of the internal combustion engine and a mass flow through an exhaust system of the motor vehicle. [11] Method according to one of the preceding claims, wherein at least one of the following situations is determined as an error: a stuck measurement of the temperature sensor, a measurement of the temperature sensor that is too slow, a change in a position of the temperature sensor, an at least partial detachment of the temperature sensor from a holder, an electrical error and a connection problem. [12] Method according to one of the preceding claims, wherein the temperature sensor is arranged in one of the following systems: an exhaust system, an internal combustion engine and a motor vehicle battery. [13] Method according to one of claims 2 to 12, wherein the predetermined threshold value depends on the modeled temperature (110) and / or on the temperature measured by the further temperature sensor and / or on a position of the temperature sensor. [14] Control device which is arranged to carry out a method according to one of the preceding claims. [15] A computer program comprising instructions which, when executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 13.

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