Method and device for adjusting a characteristic curve of a sensor in an internal combustion engine

Abstract

Method for matching a characteristic curve (26, 46) of an air mass sensor (48) installed in an internal combustion engine (2), which is designed to provide an output signal (60) dependent on an air mass flow (8) in the internal combustion engine (2) based on the characteristic curve (46), wherein the internal combustion engine (2) comprises a boost pressure sensor (18), comprising: - Measuring the air mass flow (8) with the boost pressure sensor (18), which is designed to provide a reference signal (24) dependent on the air mass flow (8); - Measuring the air mass flow (8) with the built-in air mass sensor (48), which is intended to provide the output signal (60) dependent on the air mass flow (8); and - Adjusting the characteristic curve (46) of the built-in air mass sensor (48) at the characteristic curve point of the measured air mass flow (8) until the output signal (60) corresponds to the reference signal (8, 24).

Description

Technical area

[0001] The invention generally relates to internal combustion engines, in particular to sensors installed in internal combustion engines. Furthermore, the invention relates to the field of sensor calibration. State of the art

[0002] Air mass sensors are flow sensors used in control and measurement technology that determine the mass of air flowing through a system per unit of time, known as mass flow. In automotive engineering, the sensor values ​​provided by air mass sensors are used for engine management.

[0003] Furthermore, the cylinder filling of an internal combustion engine can be determined based on the measurements of so-called boost pressure sensors.

[0004] From DE 198 57 329 B4, a calibration of an air mass sensor in a calibration device with another air mass sensor is already known.

[0005] A comparison of different measured values ​​in a motor vehicle is already known from DE 199 27 674 B4.

[0006] The calibration of an air mass sensor using a calibration device is already known from DE 40 18 776 A1.

[0007] From DE 199 50 146 C2, an adjustment of an air mass sensor by comparison with calculated values ​​is known. Disclosure of the invention

[0008] According to the invention, a method for adjusting a characteristic curve of a sensor installed in an internal combustion engine according to claim 1 as well as a sensor, an engine system and a device according to the independent claims are provided.

[0009] Preferred embodiments are specified in the dependent claims.

[0010] According to a first aspect, a method for adjusting a characteristic curve of a sensor installed in an internal combustion engine, which is intended to provide an output signal dependent on an air mass flow in the internal combustion engine based on the characteristic curve, comprises: - measuring the air mass flow with a boost pressure sensor designed to provide a reference signal dependent on the air mass flow; - measuring the air mass flow with the built-in air mass sensor, which is designed to provide the output signal dependent on the air mass flow; and - Adjust the characteristic curve of the built-in air mass sensor at the characteristic point of the measured air mass flow until the output signal corresponds to the reference signal.

[0011] The invention is based on the idea that the boost pressure sensor could be used to measure the cylinder charge in an internal combustion engine. The air mass sensor could then be used together with the cylinder charge to calculate an exhaust gas recirculation flow in an internal combustion engine. For this purpose, the exhaust gas recirculation flow could be balanced via the cylinder charge and the fresh air mass flow detected by the air mass sensor. However, both the cylinder charge and the measurement of the fresh air mass flow are subject to manufacturing variations or tolerances, which reduce the accuracy of the calculation of the exhaust gas recirculation flow. This situation could be complicated by the specific installation of the air mass sensor in the internal combustion engine.

[0012] To account for the influences of the specific installation situation of the air mass sensor in the combustion engine, a characteristic curve could be statistically determined using many different air mass sensors, which would then be used to correct the measured values ​​of the air mass sensor. However, this would be very costly, as the statistical determination of the characteristic curve would fall within the development time of the air mass sensor. Since many applications with low production volumes are generally expected in the automotive sector, the development costs for a statistically determined characteristic curve per vehicle sold are not negligible.

[0013] In addition, the variations in the air mass sensor and the boost pressure sensor cannot be taken into account by the statistically determined characteristic curve.

[0014] In contrast, the idea of ​​the invention is to record all specimen variations and other influences that reduce the accuracy of the air mass sensor and / or the boost pressure sensor when installing the air mass sensor or the boost pressure sensor and to correct or adjust the characteristic curve of the air mass sensor or the boost pressure sensor when installing the air mass sensor.

[0015] Using the specified method, a sensor, in particular an air mass sensor or a boost pressure sensor, can be recalibrated after installation in an internal combustion engine by correcting or adjusting the characteristic curve of the air mass sensor or boost pressure sensor as described above. In this way, the sensor delivers precise measured values, making it fundamentally unnecessary to develop a characteristic curve tailored exclusively to the sensor's intended use. This shortens the sensor's development time and reduces its development costs. Furthermore, the sensor can, in principle, also be recalibrated after delivery of an end application using the internal combustion engine, such as a vehicle, so that the influence of the specific installation situation is taken into account.

[0016] Furthermore, the combustion engine can include exhaust gas recirculation, which is deactivated while the defined mass flow is directed through the air duct. By deactivating the exhaust gas recirculation, the total air mass flow guided through the installed sensor corresponds to the cylinder charge, so that the boost pressure sensor can initially be referenced to one or more reference cylinder charges using an external reference sensor. Finally, the calibrated boost pressure sensor itself can be used as a reference sensor for calibrating the air mass sensor. In this way, for example, the boost pressure sensor could be calibrated at the factory during engine production. The air mass sensor can then be calibrated upon completion of the final application, such as the vehicle, based on the referenced boost pressure sensor.This is particularly useful in automotive engineering, where individual components of the combustion engine, such as the intercooler and the air duct, are application-dependent and can only be installed on the combustion engine during final vehicle assembly. During final testing of the combustion engine in the engine factory, an air mass reference is available, but for the reasons mentioned above, this can only be applied to the boost pressure sensor. Based on the referenced boost pressure sensor, the air mass sensor can then be calibrated during final vehicle assembly.

[0017] Furthermore, the combustion engine is operated without load at various engine speeds while measuring the air mass flow with the reference sensor and the built-in sensor. This refinement is particularly advantageous if the air mass sensor and the boost pressure sensor are calibrated at two different times in the production chain of a final application with the combustion engine using the air mass sensor and the boost pressure sensor. During final assembly of the combustion engine, the boost pressure sensor can most easily be calibrated at idle. This condition can be easily recreated, for example, in an assembled vehicle to calibrate the air mass sensor by leaving the vehicle without gear, so that the installed combustion engine runs without load at various engine speeds.

[0018] According to a further embodiment, the internal combustion engine comprises a compressor in the air duct, which increases the boost pressure of the air mass flow before it enters a combustion chamber of the internal combustion engine. The compressor allows the boost pressure of the air mass flow to be varied, whereby the amount of cylinder charge supplied to the combustion chamber can be varied on the combustion chamber side. Thus, the boost pressure can be used as a setting variable to approach various characteristic curve points, at least over a limited range of the characteristic curve of the built-in sensor, and to compare them with the characteristic curve of the reference sensor. On the one hand, this can be used for accelerated calibration. On the other hand, the calibration of the characteristic curve of the built-in sensor can be carried out redundantly, which increases the reliability of the calibrated characteristic curve.

[0019] In a special development of the invention, the characteristic curve of the installed sensor is shifted based on the calibrated characteristic point. This is particularly useful for air mass sensors or boost pressure sensors that have a known characteristic curve behavior. For example, an ultrasonic air mass sensor has a linear characteristic curve. With the calibrated characteristic point, this known linear characteristic curve only needs to be passed through the calibrated characteristic point, and the ultrasonic air mass sensor is fully calibrated. The same applies to non-linear air mass sensors or boost pressure sensors with fundamentally known characteristic curves.

[0020] If the characteristic curve is unknown, but the characteristic behavior is known, the characteristic curve of the installed sensor could be interpolated based on the characteristic curve point or, optionally, additional recorded characteristic curve points. Alternatively, each individual characteristic curve point of the installed sensor can be determined using the specified method.

[0021] According to a further aspect, an air mass sensor is provided for outputting an output signal dependent on an air mass flow based on a characteristic curve, wherein the characteristic curve is adjusted according to the above method.

[0022] According to a further aspect, a boost pressure sensor is provided for outputting an output signal dependent on a cylinder charge of an internal combustion engine based on a characteristic curve, wherein the characteristic curve is adjusted according to the above method.

[0023] According to a further aspect, an internal combustion engine comprising a combustion chamber, an air duct conducting a mass flow into the combustion chamber and the above air mass sensor and / or the above boost pressure sensor is provided.

[0024] According to a further aspect, a device is provided for adjusting a characteristic curve of a sensor installed in an internal combustion engine, which is provided for providing an output signal dependent on an air mass flow in the internal combustion engine based on the characteristic curve, comprising: - a reference sensor for measuring the air mass flow, wherein the reference sensor is provided for providing a reference signal dependent on the air mass flow; - a built-in sensor for measuring the air mass flow, wherein the built-in sensor is provided for providing the output signal dependent on the air mass flow; and - an adjustment device for adjusting the characteristic curve of the built-in sensor at the characteristic point of the measured air mass flow until the output signal corresponds to the reference signal. Brief description of the drawings

[0025] Preferred embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 an exemplary schematic view of an internal combustion engine in a first production state; and Fig. 2 an exemplary schematic view of the combustion engine from Fig. 1 in a second production state. Description of embodiments

[0026] In the figures, identical elements are given the same reference symbols and are described only once.

[0027] Reference is made to Fig. 1, which shows an exemplary schematic view of an internal combustion engine 2 in a first production state.

[0028] The internal combustion engine 2 comprises a combustion chamber 4, to which fresh air 8 is supplied via a fresh air duct 6. The combustion exhaust gas 10 produced in the combustion chamber 4 by combustion can be expelled via an outlet 12. A portion 14 of the combustion exhaust gas 10 can be recirculated into the combustion chamber 4 via an exhaust gas recirculation duct 16 and the fresh air duct 8.

[0029] A boost pressure sensor 18 is arranged at the inlet to the combustion chamber 4 and is designed to detect a boost pressure in the combustion chamber 4. The boost pressure sensor 18 outputs a first measurement signal 20 that depends on the boost pressure to the combustion chamber 4. Based on this measurement signal 20, the boost pressure to the combustion chamber 4 can be calculated. If the boost pressure is known, it can be thermodynamically converted, in a manner known to those skilled in the art, into the air mass 24 that is drawn into the combustion chamber 4 per power stroke of the internal combustion engine 2. This air mass 24 is commonly known as the cylinder charge 24.

[0030] In practice, the entire conversion is performed using several characteristic curves, all of which can be adjusted together using the method according to the invention. For the sake of simplicity, the conversion between the measurement signal 22 and the cylinder charge 24 will be considered below using a single characteristic curve 26, which combines all the characteristic curves used in practice.

[0031] To calibrate the characteristic curve 26 associated with the boost pressure sensor 18, the internal combustion engine 2 is connected to a test bench 28, which pumps fresh air 8 into the internal combustion engine 2 from a pipe 30. A reference sensor 32 is inserted into the pipe 30 of the test bench 28. This reference sensor 32 detects the fresh air 8 pumped into the internal combustion engine 2 and outputs a second measurement signal 34 to a reference characteristic curve 36. The mass of the fresh air 8 pumped into the internal combustion engine 2 is determined via the reference characteristic curve 36 associated with the reference sensor 32.

[0032] An exhaust gas recirculation valve 38 is arranged in the exhaust gas recirculation channel 16, via which the exhaust gas recirculation channel 16 can be opened and closed based on an exhaust gas recirculation signal 40. Furthermore, the portion 14 of the combustion exhaust gas 10 recirculated via the exhaust gas recirculation channel 16 can be cooled via an exhaust gas recirculation cooler 42. During the calibration of the boost pressure sensor 18 or its characteristic curve 26, the exhaust gas recirculation valve 38 closes the exhaust gas recirculation channel 16 so that the cylinder charge 24 exactly corresponds to the fresh air 8 supplied from the test bench 28.

[0033] In order to compensate for installation-related and intrinsic manufacturing variations or tolerances of the boost pressure sensor 18, which can lead to errors in the measured cylinder charge 24, its characteristic curve 26 is calibrated based on at least one measurement with the reference sensor 32. For this purpose, the cylinder charge 24 measured via the boost pressure sensor 18 and its characteristic curve 26 is compared in a calibrating device 44 with the mass of the fresh air 8 measured via the reference sensor 32 and its reference characteristic curve 36. If the two values ​​24, 8 deviate from one another, the calibrating device 44 controls the characteristic curve 26 of the boost pressure sensor 18 with a first control signal 46 and corrects the corresponding characteristic curve value of the characteristic curve 26 that belongs to the measured point from the measurement signal 22 and the cylinder charge 24 in such a way that the cylinder charge 24 of the characteristic curve point is calibrated to the measured mass of the fresh air 8.The adjustment device 44 can now correct each individual characteristic curve value of the characteristic curve 26 in this way or interpolate the characteristic curve 26 if fewer measured characteristic curve values ​​are sufficient due to a known behavior of the characteristic curve 26 or the boost pressure sensor 18.

[0034] Preferably, the adjustment device 44 can output the exhaust gas recirculation signal 40 during its operation in such a way that the exhaust gas recirculation channel 16 is or remains closed.

[0035] Reference is made to Fig. 2, which is an exemplary schematic view of the internal combustion engine 2 from Fig. 1 in a second production state.

[0036] In the second production state of the combustion engine 2, it is assumed that the characteristic curve 26 of the boost pressure sensor 18 corresponds to the Fig. 1 described procedure.

[0037] In the second production state, an air mass sensor 48, an intercooler 50 and a turbocharger 52, also called a compressor, were added to the combustion engine 2.

[0038] The fresh air 8 can be compressed via the turbocharger before being fed to the combustion chamber 4 of the internal combustion engine 2. Since this heats the fresh air 8, the compressed fresh air 8 flows through the charge air cooler 50 to increase the mass of the fresh air 8 that can be absorbed in the combustion chamber 4. The boost pressure of the compressed fresh air 8 can be controlled by the balancing device 44 via a second control signal 54, which will be discussed in more detail later.

[0039] The two production states have been separated in this example to provide a clearer illustration of the situation. Calibration of boost pressure sensor 18 can also be performed after completion of the second production state. Pipe 30 of test bench 28 can be connected to turbocharger 52, with a standardized intercooler 50 generally being used on test bench 28. The position of air mass sensor 48 has not yet been conclusively defined on the test bench. Only after installation of combustion engine 2 with its own intercooler 50 in a vehicle can the production variations or tolerances of air mass sensor 48 be finally compensated for by a calibration analogous to the calibration of boost pressure sensor 18.

[0040] The air mass sensor 48 has a characteristic curve 56, by means of which a third measurement signal 58 detected by the air mass sensor 48 and dependent on the fresh air 8 is converted into a measured fresh air 60.

[0041] In order to compensate for installation-related and intrinsic variations or tolerances of the air mass sensor 48, which can lead to errors in the measured fresh air 60, its characteristic curve 26 is compared based on at least one measurement with the boost pressure sensor 18, which is already part of the first production state of the Fig.1 was calibrated. For this purpose, the fresh air 60 measured via the air mass sensor 48 and its characteristic curve 46 is compared in the adjustment device 44 with the cylinder charge 26 measured via the boost pressure sensor 18 and its characteristic curve 26. If the two values ​​60, 24 differ from one another, the adjustment device 44 controls the characteristic curve 46 of the air mass sensor 48 with a third control signal 62 and corrects the corresponding characteristic curve value of the characteristic curve 46 that belongs to the measured point from the third measurement signal 58 and the measured fresh air 60 in such a way that the measured fresh air 60 of the characteristic curve point is adjusted to the cylinder charge 24. Since the cylinder charge 24 has already been calibrated to the fresh air 8, the measured fresh air 60 is thus also calibrated to the fresh air 8.The adjustment device 44 can now correct each individual characteristic curve value of the characteristic curve 46 in this way or interpolate the characteristic curve 46 if fewer measured characteristic curve values ​​are sufficient due to a known behavior of the characteristic curve 46 or the air mass sensor 48.

[0042] The exhaust gas recirculation channel 14 should remain closed during the calibration of the characteristic curve 46 of the air mass sensor 48. As already explained, the calibration device 44 can ensure this by means of the exhaust gas recirculation signal 40.

[0043] To adjust various characteristic curve points of fresh air 8, the adjustment device 44 can adjust the boost pressure of the fresh air 8 via the second control signal 54. Depending on the boost pressure of the fresh air 8, the combustion chamber 4 can accommodate a higher or lower cylinder charge 24. In this way, a variation of the characteristic curve points of the fresh air 8 is possible, at least to a limited extent.

Claims

[1] Method for adjusting a characteristic curve (26, 46) of an air mass sensor (48) installed in an internal combustion engine (2), which is provided for providing an output signal (60) dependent on an air mass flow (8) in the internal combustion engine (2) based on the characteristic curve (46), wherein the internal combustion engine (2) comprises a boost pressure sensor (18), comprising: - measuring the air mass flow (8) with the boost pressure sensor (18), which is provided for providing a reference signal (24) dependent on the air mass flow (8); - measuring the air mass flow (8) with the built-in air mass sensor (48), which is provided for providing the output signal (60) dependent on the air mass flow (8); and - Adjusting the characteristic curve (46) of the built-in air mass sensor (48) at the characteristic curve point of the measured air mass flow (8) until the output signal (60) corresponds to the reference signal (8, 24). [2] Method according to claim 1, wherein before the calibration of the air mass sensor (48) the characteristic curve (26) of the boost pressure sensor (18) was calibrated by comparison with a reference sensor (32). [3] Method according to claim 1 or 2, wherein the internal combustion engine (2) comprises an exhaust gas recirculation (16) for recirculating combustion exhaust gas, wherein the exhaust gas recirculation (16) is closed during the measurement of the air mass flow (8) with the boost pressure sensor (18) and the built-in air mass sensor (48). [4] Method according to one of the preceding claims, wherein the internal combustion engine (2) is operated without load during the measurement of the air mass flow (8) with the boost pressure sensor (18) and the air mass sensor (48). [5] Method according to one of the preceding claims, wherein the internal combustion engine (2) comprises a compressor (52) which increases the boost pressure of the air mass flow (8) before entering a combustion chamber (4) of the internal combustion engine (2). [6] Method according to one of the preceding claims, wherein the characteristic curve (26, 46) is shifted based on the characteristic curve point. [7] Air mass sensor (48) for outputting an output signal (60) dependent on an air mass flow (8) based on the characteristic curve (46), wherein the characteristic curve (60) is adjusted according to a method according to one of the preceding claims. [8] Internal combustion engine (4) comprising a combustion chamber (4), an air duct (6) conducting a mass flow (8) into the combustion chamber (4) and an air mass sensor (48) according to claim 7. [9] Device (28) for adjusting a characteristic curve (26, 46) of an air mass sensor (48) installed in an internal combustion engine (2), which is provided for providing an output signal (60) dependent on an air mass flow (8) in the internal combustion engine (2) based on the characteristic curve (46), wherein the internal combustion engine (2) comprises a boost pressure sensor (18), comprising means for: - measuring the air mass flow (8) with the boost pressure sensor (18), which is provided for providing a reference signal (24) dependent on the air mass flow (8); and for - measuring the air mass flow (8) with the built-in air mass sensor (48), which is provided for providing the output signal (60) dependent on the air mass flow (8); and for - Adjusting the characteristic curve (46) of the built-in air mass sensor (48) at the characteristic curve point of the measured air mass flow (8) until the output signal (60) corresponds to the reference signal (8, 24).

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