Methods and apparatus for monitoring sensors arranged in the exhaust region of an internal combustion engine

Abstract

A method is proposed for monitoring a sensor (22) arranged in the exhaust region of an internal combustion engine (10). The method includes: determining a sensor temperature using the sensor (22), determining a model temperature of the sensor (22), integrating the change in the sensor temperature and the change in the model temperature if the change in the sensor temperature is greater than a predetermined first threshold and the change in the model temperature is greater than a predetermined second threshold, and comparing the integral of the change in the sensor temperature with a predetermined fourth threshold.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for monitoring sensors arranged in the exhaust region of an internal combustion engine. Background Technology

[0002] A large number of sensors are known to be used in the exhaust region of internal combustion engines from existing technology.

[0003] The present invention will now be described with particular reference to a sensor for detecting particulate matter or particles, especially soot particles in the exhaust stream of an internal combustion engine, without limiting other embodiments and applications.

[0004] It is known in practice that the concentration of particulate matter (such as soot or dust particles) in exhaust gas is measured using two electrodes arranged on a ceramic substrate. This can be achieved, for example, by measuring the resistance of the ceramic material separating the two electrodes. More precisely, it measures the current flowing between the electrodes when a voltage is applied to them. Soot particles deposit between the electrodes due to electrostatic forces and form conductive bridges between them over time. The more bridges present, the greater the measured current increases. This results in increased short circuits between the electrodes. The sensor element is regenerated before each measurement by bringing it to at least 700°C via an integrated heating element, thereby burning off the soot deposits.

[0005] Therefore, this type of sensor operates based on the principle of impedance measurement of the mass of soot accumulated on the sensor element over a longer measurement period. This type of sensor is used, for example, in the exhaust system of an internal combustion engine, such as a diesel engine. Typically, the sensor is located downstream of the exhaust valve or soot particulate filter and is used to monitor the soot particulate filter.

[0006] In the case of exhaust sensors, such as particulate sensors, it is essential to monitor whether the exhaust sensor is installed in the exhaust system as intended. This can be achieved through diagnostics such as removal identification by measuring the temperature of the sensor element. Removal is identified if the modeled minimum temperature of the exhaust system is reached and the temperature of the sensor element is below a threshold. This occurs when the sensor element is not heated, i.e., during the measurement phase. Alternatively, a protection tube diagnostic is performed. If the heating power used to maintain a constant sensor temperature does not change or changes too little in response to variations in exhaust flow velocity, a removed or blocked protection tube is identified. This diagnostic approach is cumbersome.

[0007] A method and apparatus for monitoring components arranged in the exhaust region of an internal combustion engine are known from DE 10 2009 003 091 A1.

[0008] While existing devices and methods for monitoring sensors arranged in the exhaust region of an internal combustion engine have many advantages, they still contain room for improvement. Thus, due to the tolerance between the exhaust system's model temperature and the sensor temperature, identification can only be performed when the gap between the model temperature and the sensor temperature is sufficiently large, i.e., at a sufficiently high model temperature. This leads to difficulties in determining the frequency of diagnostic activation in vehicles where the particulate sensor is installed in a relatively cold location. Summary of the Invention

[0009] Therefore, a method and apparatus for monitoring sensors arranged in the exhaust region of an internal combustion engine are proposed, which at least largely avoid the drawbacks of known monitoring methods and, in particular, implement analytical processing for identifying removed sensors. This analytical processing is based on the analysis of temperature changes and is independent of absolute temperature values, allowing the diagnostics to be activated at lower temperatures compared to methods described in the prior art.

[0010] Within the scope of this disclosure, the terms “first,” “second,” “third,” “fourth,” and similar terms are used to distinguish specific features or components and should not indicate a specific order, such as weight.

[0011] In a first aspect of the invention, a method is provided for monitoring a sensor arranged in the exhaust region of an internal combustion engine. The method includes determining the sensor temperature using the sensor. Here, the sensor temperature can be determined directly or indirectly using the sensor.

[0012] The method further includes determining a model temperature for the sensor. This model temperature approximates the temperature at the sensor's mounting location. In other words, the model temperature is observed to be a temperature that reflects, as accurately as possible, the temperature measured by the sensor at the location where it is mounted. This model temperature can be formed using a real or modeled temperature source. In practice, a weighted average (calibrable) of the exhaust temperature and the wall temperature at the sensor mounting location is used as the model temperature for the sensor. If a real temperature sensor is available at a suitable location in the (vehicle's) exhaust manifold, it can be used for both the exhaust and wall temperatures, or a model can be created for both the exhaust and wall temperatures.

[0013] The method further includes integrating the change in sensor temperature and the change in model temperature if the change in sensor temperature exceeds a predetermined first threshold and the change in model temperature exceeds a predetermined second threshold. Accordingly, the temperature change is integrated only if it exceeds the corresponding threshold. The method further includes comparing the integral of the change in sensor temperature with a predetermined fourth threshold. Preferably, the change in both sensor temperature and model temperature is a temperature increase.

[0014] This analytical processing method fully utilizes the fact that, in the case of a removed sensor, the sensor temperature does not show a significant increase. The installed sensor, however, follows the exhaust system model temperature within a certain range. This method is based on the correlation between temperature rise and the exhaust system model temperature and sensor temperature. This correlation is achieved by integrating the temperature rise of both the model temperature and the sensor temperature separately when the rise exceeds a defined threshold. By appropriately selecting the integration threshold, signal noise and irrelevant temperature rises can be ignored. If insufficient consistency is observed, diagnostic errors can be set, thus identifying sensor removal.

[0015] The term "integral," as used herein, is a broad term and should be given the common and general meaning understood by those skilled in the art. The term is not limited to a specific or matching meaning. It may, in particular, refer to the higher-level concepts used for indefinite and definite integrals without restriction. The calculation of an integral is called performing integration. The definite integral of a function assigns a number to the function. If the definite integral of a real function is formed with respect to variables, the result can be interpreted in a two-dimensional coordinate system as the surface area of ​​the plane between the graph of the function, the x-axis, and the parallel lines of the definite integral relative to the y-axis. Here, the area below the x-axis is counted as negative. This is the directional surface area (also called area balance). This convention is chosen so that the definite integral is a linear mapping, which is a central characteristic of the terminology of integration, not only for theoretical considerations but also for concrete calculations. This also ensures that the so-called principal theorems of differential and integral calculations apply. The indefinite integral of a function assigns a set of functions to the function, the elements of which are called root functions. The root functions are characterized in that their first derivatives are consistent with the function being integrated. The main theorems for differential and integral calculus provide information on how definite integrals can be calculated from root functions.

[0016] The method further includes comparing the integral of the change in model temperature with a predetermined fourth threshold if the integral of the change in sensor temperature is greater than a predetermined third threshold. Therefore, if a sufficient temperature rise is observed, i.e., if the integral of the positive model temperature change reaches a calibrable threshold, the aforementioned analysis is performed.

[0017] The model temperature can be determined based at least on the exhaust temperature and / or the wall temperature of the exhaust zone at the sensor's mounting location.

[0018] The method may further include low-pass filtering of the sensor temperature and / or model temperature. Accordingly, low-pass filtering of the sensor temperature and / or model temperature may be performed to smooth the signal. The term "low-pass filter," as used herein, is a broad term and should be given the common and general meaning understood by those skilled in the art. The term is not limited to a specific or matched meaning. The term may refer in particular, without limitation, to filtering performed using a low-pass filter. In electronics, a filter is called a low-pass filter because it allows signal components with frequencies below its threshold frequency to pass through with almost no attenuation, while relatively attenuating components with higher frequencies. In communication technology, the threshold frequency is a frequency value above which the signal amplitude (voltage) or modulation amplitude at the output of the component drops below a predetermined value.

[0019] The method may further include forming a sensor temperature quotient and / or a model temperature quotient at a predetermined time step. To allow observation of temperature changes, the difference between the two temperatures is formed accordingly using a selectable time step dt.

[0020] The method may further include determining sensor removal and / or non-functional installation if the integral of the sensor temperature change is less than a predetermined fourth threshold, and determining sensor installation and / or functional installation if the integral of the sensor temperature change reaches or exceeds the predetermined fourth threshold. Therefore, if the integral of the positive sensor temperature change at that point in time is less than a calibrable threshold, an error is identified, i.e., sensor removal; otherwise, a result of no damage is reported.

[0021] The sensor can be a particle sensor.

[0022] The term "particle sensor," as used herein, is a broad term and should be given the common and general meaning understood by those skilled in the art. The term is not limited to a specific or matching meaning. It can refer, without limitation, specifically to a sensor configured for detecting microparticles or particles. The microparticles are preferably conductive. The functional principle of a particle sensor is based on the measurement of resistance. Ash particles are deposited on the electrode structure, forming ash paths between the electrodes. Before each measurement stage, the sensor element is regenerated by heating to obtain the defined state of the sensor element at the start of the measurement process.

[0023] The internal combustion engine can be a diesel motor, and the method can be performed within the scope of on-board diagnostics for diesel motors.

[0024] In another aspect, an apparatus for monitoring sensors arranged in the exhaust region of an internal combustion engine is proposed. The apparatus includes a control unit configured to perform the method described according to any of the above embodiments. This control unit can be implemented in a controller, such as a motor controller.

[0025] In another aspect, a computer program is proposed, which is configured to perform each step of the method according to any of the above embodiments.

[0026] In another aspect, an electronic storage medium is proposed on which such a computer program is stored.

[0027] In another aspect, an electronic controller is proposed that includes such an electronic storage medium. Attached Figure Description

[0028] Other optional details and features of the invention will become apparent from the following description of preferred embodiments, which are schematically illustrated in the accompanying drawings.

[0029] The attached diagram shows: Figure 1 This illustrates the technical environment in which the method according to the present invention is applied. Figure 2 The sensor element of a sensor implemented as a particle sensor is schematically shown in a top view. Figure 3 A flowchart of the method according to the present invention is shown. Figure 4 This illustrates an exemplary process of integrating temperature and positive temperature changes under intact conditions. Figure 5 An exemplary process of the integral of temperature and positive temperature changes under fault conditions is shown. Detailed Implementation

[0030] Figure 1 The technical environment in which the method according to the invention is applied is illustrated. Additionally, this technical environment may also include an exhaust aftertreatment device that incorporates measures for reducing at least one additional legally restricted component, such as NOx reduction measures.

[0031] Combustion air is supplied to an internal combustion engine 10, which can be implemented as a diesel motor, via an air supply device 12. The amount of combustion air is determined using an air quality meter 14 within the air supply device 12. This air quantity can be used to correct for the accumulation probability of particles present in the exhaust gas of the internal combustion engine 10. The exhaust gas from the internal combustion engine 10 is discharged through an exhaust system 16, in which an exhaust purification device 18 is arranged. This exhaust purification device 18 can be implemented as or may include a diesel particulate filter. Furthermore, in the example shown, an exhaust probe 20, implemented as a λ probe, and a sensor 22, implemented as a particulate sensor, are arranged in the exhaust system 16, providing signals from the exhaust probe and the sensor to a motor control device 24. The sensor 22 is positioned downstream of the exhaust purification device 18 in the exhaust flow direction. Additionally, the motor control device 24 is connected to the air quality meter 14 and determines the amount of fuel that can be supplied to the internal combustion engine 10 via a fuel metering device 26 based on the data supplied to the motor control device. Sensor 22, or an additional sensor, can also be arranged in front of the exhaust purification device 18 in the direction of exhaust flow. With the aid of the device shown, particulate emissions from the internal combustion engine 10 can be observed (On-Board Diagnose) and the installation of the exhaust purification device 18, which is configured as a diesel particulate filter (DPF), can be diagnosed or a malfunction of the exhaust purification device can be identified.

[0032] Figure 2 A schematic top view of the sensor element of sensor 22, implemented as a particle sensor, is shown. A first electrode 30 and a second electrode 32 are applied to an insulating carrier 28, which is made of, for example, alumina. The electrodes 30 and 32 are implemented as two interlocking, comb-shaped electrodes in an interdigitated manner. A first port 34 and a second port 36 are provided at the front ends of the electrodes 30 and 32, through which the electrodes 30 and 32, used for voltage supply and for performing measurements, can be connected to a control unit (not shown). Additionally, sensor 22 has a temperature sensor 38 by means of which the sensor temperature can be directly determined. The temperature sensor 38 can be implemented in the form of a platinum corrugated section, wherein the temperature-related resistance is determined by additional electrodes and the resistance can be analyzed within the motor control device 24.

[0033] Additionally, sensor 22 has a heating element 40 integrated in carrier 28 and an optional protective layer 42. Here, the heating element 40 can be configured to also function as temperature sensor 38, or the heating element 40 and temperature sensor 38 can be configured as separate electrical conductors with separate electrodes.

[0034] The working principle of this type of particle sensor has been well described in the literature, so it should only be briefly described below.

[0035] If such a sensor 22 operates in a gas flow that guides particles, for example in the exhaust passage of a diesel motor, particles from the gas flow will deposit on the sensor 22. In the case of a diesel motor, the particles are particularly soot particles with corresponding conductivity. Here, the particle deposition rate on the sensor 22 is related not only to the particle concentration in the exhaust gas but also primarily to the voltage applied to the electrodes 30, 32. The applied voltage generates an electric field that exerts a corresponding attractive force on charged particles and particles with dipole charges. Therefore, by appropriately selecting the voltage applied to the electrodes 30, 32, the particle deposition rate can be affected.

[0036] In this embodiment, at least the line sections of electrodes 30 and 32 and the carrier 28 are covered with an optional protective layer 42 on the electrode side. The optional protective layer 42 protects electrodes 30 and 32 from corrosion, given the typically high operating temperatures of the sensor 22. This optional protective layer is made of a material with low conductivity in this embodiment, but it could also be made of an insulator.

[0037] Particles from the gas stream are deposited in a layer on the protective layer 42 after a predetermined time. Due to the low conductivity of the protective layer 42, the particles form a conductive path between the electrodes 30 and 32, causing a change in resistance between the electrodes 30 and 32 depending on the amount of deposited particles. This change in resistance can be measured, for example, by applying a constant voltage to ports 34 and 36 of the electrodes 30 and 32 and determining the change in current through the accumulated particles.

[0038] If the protective layer 42 is constructed in an insulating manner, the deposited particles cause a change in the ohmic resistance of the sensor 22, which can be analyzed by corresponding measurements, preferably using a DC voltage.

[0039] The diagnostic method according to the invention is described in more detail below. The functionality of the method according to the invention, with variations described above or below, can hereby be advantageously implemented as software in the motor control device 24 of the internal combustion engine 10, or in the case of a diesel internal combustion engine, in the electronic diesel control (EDC) device. Accordingly, the motor control device 24 can be used as a control device for a device or controller to perform the method. For example, the method can be performed within the scope of on-board diagnostics of a diesel motor.

[0040] Figure 3A flowchart of the method according to the invention is shown. In step S10, the method according to the invention sets up a sensor temperature to be determined using sensor 22. This sensor temperature can be determined directly or indirectly. In the subsequent step S12, the sensor temperature is low-pass filtered. Additionally, temperature changes in the sensor temperature are detected, and in particular, temperature increases are detected. To allow observation of temperature changes, in the subsequent step S14, a difference quotient of the sensor temperature is formed over a predetermined time step dt. If the change in sensor temperature is greater than a predetermined first threshold, the change in sensor temperature is integrated in step S16. The first threshold is chosen such that changes due to signal noise are masked. Small changes are not considered where no corresponding pendant can be found in terms of changes in the model temperature of sensor 22. Here, the focus is not on comparing temperature changes within a single time step, but rather on comparing temperature changes over a larger time period, such as a few seconds.

[0041] In parallel with steps S10 to S16, the method is set in step S18 to determine the model temperature of sensor 22. This model temperature can be determined, for example, by means of another sensor. The model temperature is based at least on the exhaust temperature and / or the wall temperature of the exhaust area at the sensor's mounting location. In the subsequent step S20, the model temperature is low-pass filtered. Additionally, temperature changes in the model temperature are detected, and in particular, temperature increases are detected. To allow observation of temperature changes, in the subsequent step S22, a difference quotient of the model temperature is formed over a predetermined time step dt. If the change in model temperature exceeds a predetermined second threshold, the change in model temperature is integrated in step S24. The second threshold is chosen such that changes due to signal noise are masked. Only the following model temperature increase is considered: for the increase in model temperature, a corresponding response of the sensor temperature can also be observed. Here, the focus is not on comparing temperature changes within a single time step, but rather on comparing temperature changes over a larger time period, such as a few seconds.

[0042] If, in subsequent step S26, the integral of the model temperature change is greater than a predetermined third threshold, then in step S28, the integral of the sensor temperature change is compared with a predetermined fourth threshold. Otherwise, the method terminates after step S26. If, in step S28, the integral of the sensor temperature change is less than the predetermined fourth threshold, then in step S30, the removal of sensor 22 and / or non-functional installation is determined. If, in step S28, the integral of the sensor temperature change reaches or exceeds the predetermined fourth threshold, then in step S32, the installation of sensor 22 and / or functional installation is determined.

[0043] Figure 4This illustrates an exemplary process of the integral of temperature and positive temperature change under intact conditions. Time is plotted on the X-axis (44). The sensor temperature, model temperature, integral of the positive sensor temperature change, and integral of the positive model temperature change are shown on the Y-axis (46). Curve 48 shows the process of sensor temperature change. Curve 50 shows the process of sensor model temperature change. Curve 52 shows the process of the integral of the positive sensor temperature change. Curve 54 shows the process of the integral of the positive model temperature change. (The last sentence appears to be incomplete and possibly refers to a different plot.) Figure 4 As can be seen, with the sensor 22 intact, the sensor temperature follows the model temperature, resulting in curves 52 and 54 having similar, corresponding integral changes.

[0044] Figure 5 An exemplary process of integrating the temperature and positive temperature changes under fault conditions is shown. Only the process described below is related to... Figure 4 The differences are that the same or similar features are given the same reference numerals. For example, those that can be seen from... Figure 5 As can be seen, in the case of a faulty sensor 22, the sensor temperature does not follow the model temperature. Thus, as the model temperature increases, the sensor temperature remains almost constant, as can be seen from curves 48 and 50. Correspondingly, curve 54 increases, while curve 52 does not.

[0045] Another advantage of this analysis method is the expectation of high separation clarity, as the integral of sensor temperature does not increase or only slightly increases under fault conditions. Therefore, the fault threshold can be set very low, allowing analysis to proceed after relatively little model temperature rise. In exceptional cases, sensor temperature rise under fault conditions may be caused by heat buildup, such as when a vehicle is parked in a garage after being driven directly under high motor load. However, in such scenarios, the temperature rise is primarily small and relatively slow, making it possible to prevent integration of such a rise by appropriately selecting the integration threshold.

[0046] The analysis and processing method implemented in this invention fully utilizes temperature variations, i.e., under relatively dynamic driving conditions. Currently used methods presuppose relatively static conditions with small variations. That is, the analysis and processing method covers complementary driving conditions, thus both can be advantageously used simultaneously to identify disassembled sensors. In this case, the method that first yields diagnostic results can trigger error setting. It is also possible to consider using only the described new analysis and processing method.

[0047] The use of this invention can be demonstrated through analysis using corresponding software. The invention can also be demonstrated in terms of how the corresponding diagnostics should be applied to the sensor removal process. Furthermore, it can also be demonstrated by operating the sensor using the controller and corresponding software according to the invention.

Claims

1. A method for monitoring a sensor (22) arranged in the exhaust region of an internal combustion engine (10), the method comprising, - The sensor temperature is determined using the sensor (22). - Determine the model temperature of the sensor (22), If the change in the sensor temperature exceeds a predetermined first threshold and the change in the model temperature exceeds a predetermined second threshold, then the change in the sensor temperature is integrated, and the change in the model temperature is integrated. - If the integral of the model temperature change is greater than a predetermined third threshold, then the integral of the sensor temperature change is compared with a predetermined fourth threshold. - If the integral of the temperature change of the sensor is less than the predetermined fourth threshold, the removal of the sensor (22) and / or non-functional installation is determined, and if the integral of the temperature change of the sensor reaches or exceeds the predetermined fourth threshold, the installation of the sensor (22) and / or functional installation is determined.

2. The method according to claim 1, wherein, The determination of the model temperature is based at least on the exhaust temperature and / or the wall temperature of the exhaust area at the mounting location of the sensor (22).

3. The method according to claim 1 or 2, wherein the method further comprises low-pass filtering of the sensor temperature and / or the model temperature.

4. The method according to claim 1 or 2, wherein the method further comprises forming a sensor temperature quotient and / or a model temperature quotient at a predetermined time step.

5. The method according to claim 1 or 2, wherein, The sensor (22) is a particle sensor.

6. The method according to claim 1 or 2, wherein, The internal combustion engine (10) is a diesel motor, wherein the method is performed within the scope of on-board diagnostics of the diesel motor.

7. A device (24) for monitoring sensors (22) arranged in the exhaust region of an internal combustion engine (10), wherein, The device includes a control unit, wherein the control unit is configured to perform the method according to any one of claims 1 to 6.

8. A computer program product configured to perform each step of the method according to any one of claims 1 to 7.

9. An electronic storage medium on which a computer program product according to claim 8 is stored.

10. An electronic controller comprising the electronic storage medium according to claim 9.

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