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EP1255926B1 - Method and device for calibrating a pressure sensor - Google Patents

Method and device for calibrating a pressure sensor Download PDF

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Publication number
EP1255926B1
EP1255926B1 EP01911382A EP01911382A EP1255926B1 EP 1255926 B1 EP1255926 B1 EP 1255926B1 EP 01911382 A EP01911382 A EP 01911382A EP 01911382 A EP01911382 A EP 01911382A EP 1255926 B1 EP1255926 B1 EP 1255926B1
Authority
EP
European Patent Office
Prior art keywords
pressure
sensor
region
low
internal combustion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP01911382A
Other languages
German (de)
French (fr)
Other versions
EP1255926A2 (en
Inventor
Klaus Joos
Jens Wolber
Thomas Frenz
Hansjoerg Bochum
Matthias Kuesell
Markus Amler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
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Filing date
Publication date
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Publication of EP1255926A2 publication Critical patent/EP1255926A2/en
Application granted granted Critical
Publication of EP1255926B1 publication Critical patent/EP1255926B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M65/00—Testing fuel-injection apparatus, e.g. testing injection timing ; Cleaning of fuel-injection apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2441—Methods of calibrating or learning characterised by the learning conditions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
    • F02D41/2474—Characteristics of sensors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/3809—Common rail control systems
    • F02D41/3836—Controlling the fuel pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/22—Safety or indicating devices for abnormal conditions
    • F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices
    • F02D2041/223—Diagnosis of fuel pressure sensors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2250/00—Engine control related to specific problems or objectives
    • F02D2250/31—Control of the fuel pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2432—Methods of calibration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/3809—Common rail control systems
    • F02D41/3836—Controlling the fuel pressure
    • F02D41/3845—Controlling the fuel pressure by controlling the flow into the common rail, e.g. the amount of fuel pumped
    • F02D41/3854—Controlling the fuel pressure by controlling the flow into the common rail, e.g. the amount of fuel pumped with elements in the low pressure part, e.g. low pressure pump

Definitions

  • the present invention relates to a method and apparatus for calibrating a pressure sensor of a fuel metering system of an internal combustion engine, such as an engine.
  • the fuel metering system includes a high pressure pump for delivering fuel from a low pressure region to a high pressure region, injectors controllable in dependence on operating characteristic for metering the fuel from the high pressure region into combustion chambers of the internal combustion engine and the pressure sensor for measuring the pressure in the high pressure region.
  • the fuel metering system is designed, for example, as a Canton-Rail direct fuel injection system with a prefeed pump and an on-demand or demand-controlled high-pressure pump.
  • the prefeed pump is, for example, designed as an electric fuel pump and delivers fuel from a fuel reservoir into the low-pressure region of the fuel metering system. In the low pressure range prevails an admission pressure of for example 4 bar.
  • the high-pressure pump delivers the fuel from the low-pressure region into a high-pressure accumulator in the high-pressure region of the fuel metering system. In the high pressure accumulator prevails at gasoline fuel For example, a pressure of 150 to 200 bar and diesel fuel at a pressure of, for example, 1500 to 2000 bar.
  • a pressure control line branches off, which opens into the low-pressure region via a pressure control valve. From the low-pressure area of the fuel supply system branches off a low-pressure line, which leads via a low-pressure regulator back into the fuel tank.
  • Pressure sensors such as those used in fuel metering systems, typically have a static offset error, i. the zero point is not displayed reliably.
  • An offset error causes the measured value of pressure sensors, especially in the low pressure range, to have large relative deviations from the actual pressure value.
  • the object of the present invention is to calibrate a pressure sensor of a fuel metering system of an internal combustion engine such that the offset error is minimized.
  • the invention proposes, starting from the method of the type mentioned above, that a pressure prevailing in the high-pressure region is used as the reference pressure, that the pressure prevailing in the high-pressure region is measured as the sensor pressure by the pressure sensor, and the characteristic of the pressure sensor is such is corrected so that the difference between reference pressure and sensor pressure is minimized.
  • an adaptation of the sensor characteristic curve is thus carried out individually for each pressure sensor.
  • the inventive method is based on the consideration that in a measuring range. in which the pressure sensor the largest offset error, the reference pressure is determined with a higher accuracy than the sensor pressure can be measured by the pressure sensor. If the sensor characteristic curve is then corrected in such a way that the difference between the differential pressure and the sensor pressure is minimized, preferably set to zero, it can be assumed that the pressure sensor calibrated according to the method of the invention has a higher measuring accuracy than a pressure sensor with an unadapted sensor characteristic.
  • the present invention it is proposed that, after measuring the sensor pressure by the pressure sensor and before correcting the characteristic curve of the pressure sensor, it be checked whether the measured sensor pressure is within predefined plausibility limits. If the sensor pressure is outside a plausibility check, it is assumed that the pressure sensor is defective. In this case, an adaptation of the sensor characteristic makes no sense, the calibration of the pressure sensor is aborted and a corresponding error message is output.
  • the prerequisite for selecting the reference pressure is that the reference pressure can be determined with a higher accuracy than the sensor pressure can be measured by the pressure sensor.
  • the pressure in the high-pressure region is produced by activating a prefeed pump of the fuel metering system for generating the low-pressure in the low-pressure region and guiding the low-pressure into the high-pressure region.
  • the pre-pressure generated by the feed pump is also in the High pressure range of the fuel metering system.
  • the low-pressure regulator of the fuel metering system has, for example, an accuracy of about ⁇ 6%, which corresponds to a pre-pressure of about 4 bar ⁇ 240 mbar.
  • a pressure set at the low pressure regulator can thus be determined with a higher accuracy than the sensor pressure can be measured by the pressure sensor in the high pressure region.
  • the pressure prevailing in the low-pressure region can, for example, be conducted into the high-pressure region via additional pressure-equalizing lines or by opening already existing connecting lines between the low-pressure region and the high-pressure region.
  • the pressure set at a low pressure regulator of the fuel metering system in the low pressure range is then advantageously used.
  • the pressure from the low-pressure region through open inlet valves and exhaust valves of the high-pressure pump is passed into the high-pressure region, wherein the pressure set as the reference pressure of the low-pressure regulator of the fuel metering system in the low-pressure region taking into account the opening pressure of the intake valves and exhaust valves of the high pressure pump is used.
  • This embodiment has the advantage that no additional pressure compensation lines have to be provided between the low-pressure region and the high-pressure region; rather, an already existing connection between the low pressure area and the high pressure area via the inlet valves, the high pressure pump and the outlet valves is used to direct the pressure from the low pressure area to the high pressure area.
  • the opening pressures of the inlet and outlet valves of the high-pressure pump also have an accuracy of about ⁇ 6%, so that the reference pressure can be determined with an accuracy of at least ⁇ 500 mbar.
  • the reference pressure can be determined with an accuracy of at least ⁇ 500 mbar.
  • this corresponds to an accuracy of about ⁇ 0.3%. With such high accuracy, the sensor pressure can not be determined by the pressure sensor.
  • the reference pressure is measured by a high-precision low-pressure sensor arranged at least at times in the high-pressure region.
  • the low-pressure sensor can be introduced, for example, for the purpose of measuring the reference pressure in the high-pressure region of the fuel metering system and removed therefrom after the measurement.
  • the low-pressure sensor is permanently installed in the low-pressure region and that the reference pressure used is the measured value of the low-pressure sensor minus the opening pressures of the inlet and outlet valves of the high-pressure pump.
  • the low pressure sensor has a measuring range of about 5 bar.
  • the reference pressure is the ambient pressure.
  • the ambient pressure is usually present with a much higher accuracy than the sensor pressure through the Pressure sensor can be measured.
  • the ambient pressure can be measured via a special ambient pressure sensor. After a predetermined service life of the internal combustion engine, the ambient pressure can also be measured by a Saugrohr horrsensor.
  • the ambient pressure can also be entered manually. For example, the value entered may be a value measured at the location or a value typical of the location.
  • the prefeed pump can be activated, so that a pre-pressure builds up.
  • the pre-pressure is directed to the high pressure area.
  • the in the high pressure area, in particular in the high-pressure accumulator, adjusting pressure is measured and stored as normal value in a memory of the control unit of the internal combustion engine.
  • the pressure setting in the high-pressure region during a longer flow of the prefeed pump is then compared with the stored normal value. If the pressure and the normal value deviate from each other beyond a predetermined limit value, an error is concluded in the low-pressure region of the fuel metering system.
  • the reference pressure of the opening pressure of a pressure control valve or a pressure limiting valve of the fuel metering system is used in a specific operating state of the internal combustion engine.
  • a pressure control valve of the fuel metering system is usually normally closed with spring load. The pressure control valve is thus closed without electrical control and opens at a predetermined pressure.
  • This Opening pressure may depend on environmental parameters, such as engine speed, mass flow through the pressure control valve, ambient temperature, etc., but is generally known in certain operating conditions with relatively high accuracy. For example, in direct-injection gasoline internal combustion engines at idle speed, the opening pressure of the pressure control valve with an accuracy of about ⁇ 2.5 bar known. The inaccuracies of the pressure sensor of the fuel metering system are usually much higher.
  • the pressure control valve opens, it can be assumed that prevails in the high pressure region, a pressure which corresponds approximately to the opening pressure of the pressure control valve. This pressure is then used as the reference pressure for the adaptation of the sensor characteristic.
  • a fuel metering system with an on-demand high pressure pump does not have a pressure control valve but only a passive, spring loaded closed relief valve - (pressure relief valve) with the same pressure values as a pressure control valve.
  • the process of the invention can be carried out here in an analogous manner.
  • This development according to the invention has the additional advantage that errors of the fuel metering system can be detected during operation of the internal combustion engine.
  • the pressure control valve is switched off during certain operating states, ie closed.
  • the pressure which is established in the high-pressure region is measured and compared with a desired value which, depending on various operating parameters, in particular the mass flow through the pressure control valve and the temperature of the pressure control valve, in the control device Internal combustion engine is stored. If the measured pressure deviates from the desired value beyond a predetermined limit value, it is assumed that there is a fault in the fuel metering system.
  • Conceivable operating states for this function test are, for example, during a fuel cut or in an idling phase of the internal combustion engine.
  • the method be carried out automatically during the starting process of the internal combustion engine after switching on the ignition and before the activation of the starter. During this period, a pre-pressure in the low-pressure region of the fuel metering system is established by the prefeed pump; in the high pressure area is still no injection pressure.
  • the method be carried out automatically during the overrun of the internal combustion engine after switching off the internal combustion engine and before switching off the ignition. During the wake, injection pressure is no longer present in the high pressure area of the fuel metering system; The prefeed pump continues to build up a form.
  • the method after assembly or after a repair of the fuel metering system of the internal combustion engine, in particular after replacement of the pressure sensor, is carried out.
  • the pre-feed pump can be controlled in such a way that it builds up a pre-pressure.
  • the remaining elements of the fuel metering system are controlled in such a way that no injection pressure is applied in the high-pressure region and that the admission pressure is conducted from the low-pressure region into the high-pressure region.
  • the device comprises means for performing the method according to one of claims 1 to 11.
  • FIG. 3 is a flow chart of a preferred embodiment of a method for calibrating a pressure sensor of a fuel metering system of an internal combustion engine.
  • FIG. 2 is a common rail fuel direct injection system trained fuel metering system shown. It has a prefeed pump 1 and an on-demand or demand-controlled high-pressure pump 2.
  • the prefeed pump 1 is designed as an electric fuel pump and delivers fuel from a fuel reservoir 3 into a low-pressure region ND of the fuel metering system. In the low pressure range ND there is a pre-pressure of about 4 bar.
  • the high-pressure pump 2 conveys the fuel from the low-pressure region ND into a high-pressure reservoir 4, the so-called rail, in a high-pressure region HD of the fuel metering system.
  • the high-pressure accumulator 4 prevails at gasoline fuel pressure of about 150 to 200 bar and diesel fuel at a pressure of about 1500 to 2000 bar.
  • injectors branch off 5 which are controlled depending on the operating parameters and inject the fuel from the high-pressure accumulator 4 with the applied there injection pressure in combustion chambers 6 of the internal combustion engine with appropriate control.
  • a pressure sensor 7 is arranged in the high-pressure accumulator 4, by which the injection pressure prevailing in the high-pressure accumulator 4 is determined and a corresponding electrical signal is passed to a control unit 8 of the internal combustion engine.
  • the signal lines 9 are in FIG. 2 shown in dashed lines.
  • a pressure control line 10 branches off from the high-pressure accumulator 4 of the fuel metering system, which opens into the low-pressure region ND via a pressure control valve 11.
  • a low-pressure line 12 which leads via a low-pressure regulator 13 back into the fuel reservoir 3.
  • a Filter element 14 is arranged between the prefeed pump 1 and the high-pressure pump 2 .
  • a leak line 15 branches off, via which leak oil or gasoline of the high-pressure pump 2 can flow back into the fuel tank 3.
  • the pressure sensor 7 as used in the fuel metering system has a static offset error, i. the zero point is not displayed reliably.
  • An offset error causes the reading of the pressure sensor. 7, in particular in the low-pressure region, has large relative deviations from the actual prevailing pressure value.
  • the invention proposes a method for calibrating the pressure sensor 7, in which a low pressure prevailing in the high-pressure region HD is used as the reference pressure.
  • the reference pressure is with a high accuracy known or can be determined or measured with high accuracy.
  • the low pressure prevailing in the high-pressure region is also measured as the sensor pressure by the pressure sensor 7. After measuring the sensor pressure by the pressure sensor 7 is checked whether the measured sensor pressure is within predetermined plausibility limits. The characteristic of the pressure sensor 7 is then corrected so that the difference between the reference pressure and the sensor pressure is minimized.
  • the reference pressure there are a variety of ways to determine the reference pressure with a higher accuracy than the sensor pressure can be measured.
  • a reference pressure for example, the ambient pressure can be used.
  • the low pressure prevailing in the high-pressure accumulator 4 can also be generated by the prefeed pump 1.
  • the prefeed pump 1 of the fuel metering system is activated. It generates a form in the low-pressure area ND.
  • the admission pressure is led from the low-pressure area ND into the high-pressure area HD by opening the inlet valves and the outlet valves of the high-pressure pump 2.
  • the pressure set at the low-pressure regulator 13 of the fuel metering system in the low-pressure region ND is then used as the reference pressure, taking into account the opening pressure of the inlet valves and outlet valves of the high-pressure pump 2.
  • the low pressure regulator 13 of the fuel metering system has an accuracy of about ⁇ 6%, which corresponds to a pre-pressure of about 4 bar ⁇ 240 mbar.
  • the inlet and outlet valves of the high-pressure pump 2 also have an accuracy of about ⁇ 6%, so that the reference pressure can be determined with an accuracy of at least ⁇ 500 mbar.
  • the sensor pressure can not be determined by the pressure sensor 7.
  • the reference pressure is measured by a high-precision low-pressure sensor (not illustrated) arranged at least at times in the high-pressure region HD.
  • a low-pressure sensor can be introduced for measuring the low pressure in the high-pressure accumulator 4 and removed again after the measurement.
  • the method is preferably performed automatically during the starting process of the internal combustion engine after switching on the ignition and before the activation of the starter. Although during this time the prefeed pump is activated, however, no high pressure is generated in the high-pressure area HD.
  • the intake valves and exhaust valves of the high pressure pump 2 are adoptedichles designed as passive valves. By opening the inlet valves and the outlet valves of the high-pressure pump 2, the admission pressure is directed into the high-pressure accumulator.
  • the method can also be carried out automatically during the after-running of the internal combustion engine after switching off the internal combustion engine and before switching off the ignition.
  • the ignition is still switched on and the control unit 8 drives down the various functions of the motor vehicle in a controlled manner.
  • the prefeed pump 1 must be specifically controlled; and the intake valves and the exhaust valves of the high-pressure pump 2 must be open.
  • the inventive method is preferably according to the Assembly or after a repair of the fuel metering system of the internal combustion engine, in particular after replacement of the pressure sensor 7, carried out.
  • the opening pressure of the pressure control valve 11 of the fuel metering system in a specific operating state of the internal combustion engine can be used as the reference pressure.
  • the pressure control valve 11 is normally closed with spring load.
  • the pressure control valve 11 is therefore closed without electrical control and opens at a predetermined opening pressure.
  • the opening pressure may depend on environmental parameters such as engine speed, mass flow through the pressure control valve 11, ambient temperature, etc., but is generally known to be relatively accurate in certain operating conditions. For example, e.g. in directly injecting gasoline internal combustion engines at idle speed, the opening pressure of the pressure control valve 11 with an accuracy of about ⁇ 2.5 bar known. The inaccuracies of the pressure sensor 7 of the fuel metering system are usually much higher. If, during operation of the internal combustion engine at idle speed, the pressure control valve 11 opens, it can be assumed that in the high-pressure accumulator 4, a pressure prevails, which corresponds approximately to the opening pressure of the pressure control valve 11. This pressure is then used as the reference pressure for the adaptation of the sensor characteristic.
  • the inventive method in FIG. 1 begins in function block 20.
  • the ignition of the motor vehicle is turned on.
  • the prefeed pump 1 is activated, and in a functional block 23, the inlet valves and outlet valves of the high-pressure pump 2 are opened.
  • the reference pressure prevailing in the high-pressure accumulator 4 is read from a memory of the control unit 8. The reference pressure was determined in advance from the pressure set at the low-pressure regulator 13 taking into account the opening pressure of the intake valves and exhaust valves of the high-pressure pump 2 and stored in the memory.
  • a functional block 25 the pressure prevailing in the high-pressure accumulator 4 is then measured by the pressure sensor 7.
  • the stored in the memory of the controller 8 characteristic of the pressure sensor 7 is read in a function block 26.
  • the read-in characteristic curve of the pressure sensor 7 is shifted such that the difference between the reference pressure and the sensor pressure is minimized.
  • the corrected characteristic is then stored in a function block 28 in the memory of the controller 8.
  • the inventive method is then completed.
  • the control of the internal combustion engine by the control unit 8 is then based on the corrected characteristic of the pressure sensor 7.
  • the pressure sensor 7 now has such a high accuracy that the pressure prevailing in the high-pressure accumulator 4 pressures during the start phase (with the then in the high-pressure accumulator 4th prevailing low pressures) can be included in the calculation of the injection time of the injectors 5.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Measuring Fluid Pressure (AREA)
  • Fuel-Injection Apparatus (AREA)

Abstract

The invention relates to a method and a device for calibrating a pressure sensor (7) of a fuel dosing system of an internal combustion engine. Said fuel dosing system comprises a high-pressure pump (2) that delivers fuel from a low-pressure zone (ND) to a high-pressure zone (HD). The injectors (5) that dose the fuel from the high-pressure zone (HD) into the combustion chambers (6) of the internal combustion engine are controlled according to working characteristics. The dosing system further comprises the pressure sensor (7) that measures the pressure in the high-pressure zone (HD). The aim of the invention is to calibrate the pressure sensor (7) in such a manner that the offset-error can be reduced to a minimum. To this end, the pressure in the high-pressure zone (HD) is used as a reference pressure, the pressure in the high-pressure zone (HD) is measured by the pressure sensor (7) as the sensor pressure and the characteristic line of the pressure sensor (7) is corrected in such a manner that the difference from reference pressure and sensor pressure is reduced to a minimum.

Description

Stand der TechnikState of the art

Die vorliegende Erfindung betrifft ein Verfahren und eine Vorrichtung zum Kalibrieren eines Drucksensors eines Kraftstoffzumesssystems einer Brennkraftmaschine wie z.B. aus DE 195 47 647 bekannt. Das Kraftstoffzumesssystem weist eine Hochdruckpumpe zum Fördern von Kraftstoff aus einem Niederdruckbereich in einen Hochdruckbereich, betriebskenngrößenabhängig steuerbare Injektoren zum Zumessen des Kraftstoffs aus dem Hochdruckbereich in Brennräume der Brennkraftmaschine und den Drucksensor zum Messen des Drucks in dem Hochdruckbereich auf.The present invention relates to a method and apparatus for calibrating a pressure sensor of a fuel metering system of an internal combustion engine, such as an engine. From DE 195 47 647 known. The fuel metering system includes a high pressure pump for delivering fuel from a low pressure region to a high pressure region, injectors controllable in dependence on operating characteristic for metering the fuel from the high pressure region into combustion chambers of the internal combustion engine and the pressure sensor for measuring the pressure in the high pressure region.

das Kraftstoffzumesssystem ist beispielsweise als ein Cömmon-Rail-Kraftstoff-Direkteinspritzungssystem mit einer Vorförderpumpe und einer bedarfsgesteuerten bzw. bedarfsgeregelten Hochdruckpumpe ausgebildet. Die Vorförderpumpe ist beipielsweise als eine Elektrokraftstoffpumpe ausgebildet und fördert Kraftstoff aus einem Kraftstoff-Vorratsbehälter in den Niederdruckbereich des Kraftstoffzumesssystems. In dem Niederdruckbereich herrscht ein Vordruck von beispielsweise 4 bar. Die Hochdruckpumpe fördert den Kraftstoff aus dem Niederdruckbereich in einen Hochdruckspeicher in dem Hochdruckbereich des Kraftstoffzumesssystems. In dem Hochdruckspeicher herrscht bei Benzin-Kraftstoff beispielsweise ein Druck von 150 bis 200 bar und bei Diesel-Kraftstoff ein Druck von beispielsweise 1500 bis 2000 bar. Von dem Hochdruckspeicher zweigen mehrere Injektoren ab, die bei entsprechender Ansteuerung den Kraftstoff aus dem Hochdruckspeicher mit dem dort anliegenden Einspritzdruck in die Brennräume der Brennkraftmaschine einspritzen. Die Injektoren sind in Abhängigkeit von bestimmten Betriebskenngrößen ansteuerbar. In dem Hochdruckspeicher ist des Weiteren ein Drucksensor angeordnet, durch den der in dem Hochdruckspeicher herrschende Einspritzdruck ermittelt und ein entsprechendes elektrisches Signal an ein Steuergerät der Brennkraftmaschine geleitet wird. Schließlich zweigt aus dem Hochdruckbereich des Kraftstoffzumesssystems eine Drucksteuerleitung ab, die über ein Drucksteuerventil in den Niederdruckbereich mündet. Aus dem Niederdruckbereich des Kraftstoffversorgungssystems zweigt eine Niederdruckleitung ab, die über einen Niederdruckregler zurück in den Kraftstoff-Vorratsbehälter führt.The fuel metering system is designed, for example, as a Canton-Rail direct fuel injection system with a prefeed pump and an on-demand or demand-controlled high-pressure pump. The prefeed pump is, for example, designed as an electric fuel pump and delivers fuel from a fuel reservoir into the low-pressure region of the fuel metering system. In the low pressure range prevails an admission pressure of for example 4 bar. The high-pressure pump delivers the fuel from the low-pressure region into a high-pressure accumulator in the high-pressure region of the fuel metering system. In the high pressure accumulator prevails at gasoline fuel For example, a pressure of 150 to 200 bar and diesel fuel at a pressure of, for example, 1500 to 2000 bar. From the high-pressure accumulator branch off from several injectors, which inject the fuel from the high-pressure accumulator with the applied there injection pressure in the combustion chambers of the internal combustion engine with appropriate control. The injectors can be controlled depending on specific operating parameters. Furthermore, a pressure sensor is arranged in the high-pressure accumulator, by means of which the injection pressure prevailing in the high-pressure accumulator is determined and a corresponding electrical signal is passed to a control unit of the internal combustion engine. Finally, from the high-pressure region of the fuel metering system, a pressure control line branches off, which opens into the low-pressure region via a pressure control valve. From the low-pressure area of the fuel supply system branches off a low-pressure line, which leads via a low-pressure regulator back into the fuel tank.

Drucksensoren, wie sie auch in Kraftstoffzumesssystemen eingesetzt werden, weisen üblicherweise einen statischen Offset-Fehler auf, d.h. der Nullpunkt wird nicht zuverlässig angezeigt. Ein Offset-Fehler führt dazu, dass der Messwert von Drucksensoren insbesondere im Niederdruckbereich große relative Abweichungen zu dem tatsächlichen Druckwert aufweisen kann.Pressure sensors, such as those used in fuel metering systems, typically have a static offset error, i. the zero point is not displayed reliably. An offset error causes the measured value of pressure sensors, especially in the low pressure range, to have large relative deviations from the actual pressure value.

In der Starterphase von direkt einspritzenden Rail-Brennkraftmaschinen liegt in der Regel ein niedriger Druck vor. Die Brennkraftmaschine wird zumeist mit einem von der Vorförderpumpe erzeugten niedrigen Vordruck gestartet, und erst später wird auf den Hochdruck umgeschaltet. Da die über die Injektoren in die Brennräume eingespritzte Kraftstoffmasse stark von dem in dem Hochdruckspeicher herrschenden Einspritzdruck abhängig ist, müsste dieser in der Startphase der Brennkraftmaschine mit in die Berechnung der Einspritzzeit einbezogen werden. Aufgrund der oben beschriebenen Ungenauigkeiten des Drucksensors, insbesondere bei niedrigen Drücken, ist dies jedoch zumeist nicht möglich. Deshalb läuft nach dem Stand der Technik der Start einer direkt einspritzenden Brennkraftmaschine in der Regel ohne die Einrechnung des aktuellen, in dem Hochdruckbereich herrschenden Drucks ab.In the starter phase of direct-injection rail internal combustion engines is usually a low pressure. The internal combustion engine is usually started with a low pre-pressure generated by the prefeed pump, and only later is switched to the high pressure. Since the injected via the injectors into the combustion chambers fuel mass is heavily dependent on the pressure prevailing in the high-pressure accumulator injection pressure, this would have in the starting phase of the internal combustion engine to be included in the calculation of the injection time. Due to the above-described inaccuracies of the pressure sensor, especially at low pressures, but this is usually not possible. Therefore, according to the prior art, the start of a direct-injection internal combustion engine generally proceeds without the inclusion of the current pressure prevailing in the high-pressure region.

Aus den vorgenannten Nachteilen des Standes der Technik ergibt sich die Aufgabe der vorliegenden Erfindung, einen Drucksensor eines Kraftstoffzumesssystems einer Brennkraftmaschine derart zu kalibrieren, dass der Offset-Fehler minimiert wird.From the aforementioned disadvantages of the prior art, the object of the present invention is to calibrate a pressure sensor of a fuel metering system of an internal combustion engine such that the offset error is minimized.

Zur Lösung dieser Aufgabe schlägt die Erfindung ausgehend von dem Verfahren der eingangs genannten Art vor, dass ein in dem Hochdruckbereich herrschender Druck als Referenzdruck herangezogen wird, dass der in dem Hochdruckbereich herrschende Druck als Sensordruck durch den Drucksensor gemessen wird und dass die Kennlinie des Drucksensors derart korrigiert wird, dass die Differenz aus Referenzdruck und Sensordruck minimiert wird.To achieve this object, the invention proposes, starting from the method of the type mentioned above, that a pressure prevailing in the high-pressure region is used as the reference pressure, that the pressure prevailing in the high-pressure region is measured as the sensor pressure by the pressure sensor, and the characteristic of the pressure sensor is such is corrected so that the difference between reference pressure and sensor pressure is minimized.

Vorteile der ErfindungAdvantages of the invention

Da der Offset-Fehler von Drucksensor zu Drucksensor eine starke Streuung aufweist, ist keine allgemein gültige Applikation zur Minimierung eines Offset-Fehlers bei Drucksensoren möglich, sondern es muss jeder Drucksensor individuell abgeglichen werden.Since the offset error from pressure sensor to pressure sensor has a high degree of dispersion, no generally valid application for minimizing an offset error in pressure sensors is possible, but each pressure sensor must be individually adjusted.

Erfindungsgemäss wird also für jeden Drucksensor individuell eine Adaption der Sensorkennlinie durchgeführt. Das erfindungsgemäße Verfahren beruht auf der Überlegung, dass in einem Messbereich,. in dem der Drucksensor den größten Offset-Fehler aufweist, der Referenzdruck mit einer höheren Genauigkeit bestimmt wird, als der Sensordruck durch den Drucksensor gemessen werden kann. Wenn dann die Sensorkennlinie derart korrigiert wird, dass die Differenz aus Differenzdruck und Sensordruck minimiert, vorzugsweise gleich Null gesetzt, wird, kann davon ausgegangen werden, dass der nach dem erfindungsgemäßen Verfahren kalibrierte Drucksensor eine höhere Messgenauigkeit aufweist als ein Drucksensor mit nicht adaptierter Sensorkennlinie.According to the invention, an adaptation of the sensor characteristic curve is thus carried out individually for each pressure sensor. The inventive method is based on the consideration that in a measuring range. in which the pressure sensor the largest offset error, the reference pressure is determined with a higher accuracy than the sensor pressure can be measured by the pressure sensor. If the sensor characteristic curve is then corrected in such a way that the difference between the differential pressure and the sensor pressure is minimized, preferably set to zero, it can be assumed that the pressure sensor calibrated according to the method of the invention has a higher measuring accuracy than a pressure sensor with an unadapted sensor characteristic.

Gemäß einer vorteilhaften Weiterbildung der vorliegenden Erfindung wird vorgeschlagen, dass nach dem Messen des Sensordrucks durch den Drucksensor und vor dem Korrigieren der Kennlinie des Drucksensors überprüft wird, ob sich der gemessene Sensordruck innerhalb vorgegebener Plausibilitätsschranken befindet. Falls sich der Sensordruck außerhalb einer Plausibilitätsschranke befindet, wird davon ausgegangen, dass der Drucksensor defekt ist. In diesem Fall macht eine Adaption der Sensorkennlinie keinen Sinn, die Kalibrierung des Drucksensors wird abgebrochen und eine entsprechende Fehlermeldung ausgegeben.According to an advantageous development of the present invention, it is proposed that, after measuring the sensor pressure by the pressure sensor and before correcting the characteristic curve of the pressure sensor, it be checked whether the measured sensor pressure is within predefined plausibility limits. If the sensor pressure is outside a plausibility check, it is assumed that the pressure sensor is defective. In this case, an adaptation of the sensor characteristic makes no sense, the calibration of the pressure sensor is aborted and a corresponding error message is output.

Die Voraussetzung bei der Wahl des Referenzdrucks ist , dass der Referenzdruck mit einer höheren Genauigkeit bestimmt werden kann, als der Sensordruck durch den Drucksensor gemessen werden kann.The prerequisite for selecting the reference pressure is that the reference pressure can be determined with a higher accuracy than the sensor pressure can be measured by the pressure sensor.

Gemäß der vorliegenden Erfindung wird vorgeschlagen, dass der Druck in dem Hochdruckbereich erzeugt wird, indem eine Vorförderpumpe des Kraftstoffzumesssystems zur Erzeugung des Niederdrucks in dem Niederdruckbereich aktiviert und der Niederdruck in den Hochdruckbereich geleitet wird. Somit liegt der von der Vorförderpumpe erzeugte Vordruck auch in dem Hochdruckbereich des Kraftstoffzumesssystems an.According to the present invention, it is proposed that the pressure in the high-pressure region is produced by activating a prefeed pump of the fuel metering system for generating the low-pressure in the low-pressure region and guiding the low-pressure into the high-pressure region. Thus, the pre-pressure generated by the feed pump is also in the High pressure range of the fuel metering system.

Der Niederdruckregler des Kraftstoffzumesssystems weist bspw. eine Genauigkeit von etwa ± 6 % auf, was bei einem Vordruck von etwa 4 bar ± 240 mbar entspricht. Ein an dem Niederdruckregler eingestellter Druck kann somit mit einer höheren Genauigkeit bestimmt werden, als der Sensordruck durch den Drucksensor in dem Hochdruckbereich gemessen werden kann. Der in dem Niederdruckbereich herrschende Druck kann bspw. über zusätzliche Druckausgleichsleitungen oder durch Öffnen bereits vorhandener Verbindungsleitungen zwischen dem Niederdruckbereich und dem Hochdruckbereich in den Hochdruckbereich geleitet werden. Als Referenzdruck wird dann vorteilhafterweise der an einem Niederdruckregler des Kraftstoffzumesssystems in dem Niederdruckbereich eingestellte Druck herangezogen.The low-pressure regulator of the fuel metering system has, for example, an accuracy of about ± 6%, which corresponds to a pre-pressure of about 4 bar ± 240 mbar. A pressure set at the low pressure regulator can thus be determined with a higher accuracy than the sensor pressure can be measured by the pressure sensor in the high pressure region. The pressure prevailing in the low-pressure region can, for example, be conducted into the high-pressure region via additional pressure-equalizing lines or by opening already existing connecting lines between the low-pressure region and the high-pressure region. As reference pressure, the pressure set at a low pressure regulator of the fuel metering system in the low pressure range is then advantageously used.

Gemäß einer weiteren bevorzugten Ausführungsform der vorliegenden Erfindung wird vorgeschlagen, dass der Druck aus dem Niederdruckbereich durch geöffnete Einlassventile und Auslassventile der Hochdruckpumpe in den Hochdruckbereich geleitet wird, wobei als Referenzdruck der an einem Niederdruckregler des Kraftstoffzumesssystems in dem Niederdruckbereich eingestellte Druck unter Berücksichtigung des Öffnungsdrucks der Einlassventile und Auslassventile der Hochdruckpumpe herangezogen wird. Diese Ausführungsform hat den Vorteil, dass zwischen dem Niederdruckbereich und dem Hochdruckbereich keine zusätzlichen Druckausgleichsleitungen vorgesehen werden müssen; vielmehr wird eine bereits vorhandene Verbindung zwischen dem Niederdruckbereich und dem Hochdruckbereich über die Einlassventile, die Hochdruckpumpe und die Auslassventile dazu verwendet, den Druck aus dem Niederdruckbereich in den Hochdruckbereich zu leiten. Die Öffnungsdrücke der Einlass- und Auslassventile der Hochdruckpumpe weisen eine Genauigkeit von ebenfalls etwa ± 6 % auf, so dass sich der Referenzdruck mit einer Genauigkeit von mindestens ± 500 mbar bestimmen lässt. Bei einem in einem Kraftstoffzumesssystem einer direkt einspritzenden Benzin-Brennkraftmaschine eingesetzten Hochdrucksensor mit einem Messbereich von etwa 150 bar entspricht dies einer Genauigkeit von etwa ± 0,3 %. Mit einer so hohen Genauigkeit lässt sich der Sensordruck durch den Drucksensor nicht bestimmen.According to another preferred embodiment of the present invention, it is proposed that the pressure from the low-pressure region through open inlet valves and exhaust valves of the high-pressure pump is passed into the high-pressure region, wherein the pressure set as the reference pressure of the low-pressure regulator of the fuel metering system in the low-pressure region taking into account the opening pressure of the intake valves and exhaust valves of the high pressure pump is used. This embodiment has the advantage that no additional pressure compensation lines have to be provided between the low-pressure region and the high-pressure region; rather, an already existing connection between the low pressure area and the high pressure area via the inlet valves, the high pressure pump and the outlet valves is used to direct the pressure from the low pressure area to the high pressure area. The opening pressures of the inlet and outlet valves of the high-pressure pump also have an accuracy of about ± 6%, so that the reference pressure can be determined with an accuracy of at least ± 500 mbar. In a high pressure sensor used in a fuel metering system of a direct injection gasoline engine with a measuring range of about 150 bar, this corresponds to an accuracy of about ± 0.3%. With such high accuracy, the sensor pressure can not be determined by the pressure sensor.

Alternativ wird gemäß einer weiteren bevorzugten Ausführungsform der vorliegenden Erfindung vorgeschlagen, dass der Referenzdruck durch einen zumindest zeitweise in dem Hochdruckbereich angeordneten hochgenauen Niederdrucksensor gemessen wird. Der Niederdrucksensor kann beispielsweise zum Zwecke der Messung des Referenzdrucks in den Hochdruckbereich des Kraftstoffzumesssystems eingebracht und nach der Messung daraus wieder entfernt werden. Eine weitere Möglichkeit ist, das der Niederdrucksensor im Niederdruckbereich fest eingebaut ist und dass als Referenzdruck der gemessene Wert des Niederdrucksensors abzüglich der Öffnungsdrücke der Ein- und Auslassventile der Hochdruckpumpe verwendet wird. Der Niederdrucksensor weist einen Messbereich von etwa 5 bar auf. Aufgrund dieses im Vergleich zu dem Sensor des Kraftstoffzumesssystems beschränkten Messbereichs wirken sich relative Ungenauigkeiten (in Prozent) weniger stark auf den absoluten Wert (in bar) des gemessenen Druckes aus. Mit Hilfe des Niederdrucksensors kann der Referenzdruck somit wesentlich genauer gemessen werden, als der Sensordruck durch den Drucksensor gemessen werden kann.Alternatively, it is proposed according to a further preferred embodiment of the present invention that the reference pressure is measured by a high-precision low-pressure sensor arranged at least at times in the high-pressure region. The low-pressure sensor can be introduced, for example, for the purpose of measuring the reference pressure in the high-pressure region of the fuel metering system and removed therefrom after the measurement. Another possibility is that the low-pressure sensor is permanently installed in the low-pressure region and that the reference pressure used is the measured value of the low-pressure sensor minus the opening pressures of the inlet and outlet valves of the high-pressure pump. The low pressure sensor has a measuring range of about 5 bar. Because of this limited measurement range compared to the sensor of the fuel metering system, relative inaccuracies (in percent) have less of an effect on the absolute value (in bar) of the measured pressure. With the help of the low pressure sensor, the reference pressure can thus be measured much more accurately than the sensor pressure can be measured by the pressure sensor.

Gemäß einer anderen vorteilhaften Weiterbildung der vorliegenden Erfindung wird vorgeschlagen, dass als Referenzdruck der Umgebungsdruck herangezogen wird. Der Umgebungsdruck liegt in der Regel mit einer wesentlich höheren Genauigkeit vor, als der Sensordruck durch den Drucksensor gemessen werden kann. Der Umgebungsdruck kann über einen speziellen Umgebungsdrucksensor gemessen werden. Nach einer vorgegebenen Standzeit der Brennkraftmaschine kann der Umgebungsdruck auch durch einen Saugrohrdrucksensor gemessen werden. Der Umgebungsdruck kann auch manuell eingegeben werden. Der eingegebene Wert kann beispielsweise ein an dem Standort gemessener Wert oder ein für den Standort typischer Wert sein.According to another advantageous development of the present invention, it is proposed that the reference pressure is the ambient pressure. The ambient pressure is usually present with a much higher accuracy than the sensor pressure through the Pressure sensor can be measured. The ambient pressure can be measured via a special ambient pressure sensor. After a predetermined service life of the internal combustion engine, the ambient pressure can also be measured by a Saugrohrdrucksensor. The ambient pressure can also be entered manually. For example, the value entered may be a value measured at the location or a value typical of the location.

Als weiterer Vorteil dieser erfindungsgemäßen Weiterbildung ergibt sich eine zusätzliche Diagnosemöglichkeit des Kraftstoffzumesssystems. Nach erfolgter Adaption der Sensorkennlinie kann die Vorförderpumpe angesteuert werden, so dass sich ein Vordruck aufbaut. Der Vordruck wird in den Hochdruckbereich geleitet. Der sich in dem Hochdruckbereich, insbesondere in dem Hochdruckspeicher, einstellende Druck wird gemessen und als Normalwert in einem Speicher des Steuergeräts der Brennkraftmaschine abgelegt. Während des Betriebs der Brennkraftmaschine wird dann der sich bei einem längeren Vorlauf der Vorförderpumpe in dem Hochdruckbereich einstellende Druck mit dem gespeicherten Normalwert verglichen. Falls der Druck und der Normalwert über einen vorgegebenen Grenzwert hinaus voneinander abweichen, wird auf einen Fehler in dem Niederdruckbereich des Kraftstoffzumesssystems geschlossen.Another advantage of this development according to the invention results in an additional possibility of diagnosis of the fuel metering system. After adaptation of the sensor characteristic curve, the prefeed pump can be activated, so that a pre-pressure builds up. The pre-pressure is directed to the high pressure area. The in the high pressure area, in particular in the high-pressure accumulator, adjusting pressure is measured and stored as normal value in a memory of the control unit of the internal combustion engine. During operation of the internal combustion engine, the pressure setting in the high-pressure region during a longer flow of the prefeed pump is then compared with the stored normal value. If the pressure and the normal value deviate from each other beyond a predetermined limit value, an error is concluded in the low-pressure region of the fuel metering system.

Gemäß noch einer anderen vorteilhaften Weiterbildung der vorliegenden Erfindung wird vorgeschlagen, dass als Referenzdruck der Öffnungsdruck eines Drucksteuerventils bzw. eines Druckbegrenzungsventils des Kraftstoffzumesssystems in einem bestimmten Betriebszustand der Brennkraftmaschine herangezogen wird. Ein Drucksteuerventil des Kraftstoffzumesssystems ist üblicherweise stromlos geschlossen mit Federbelastung. Das Drucksteuerventil ist also ohne elektrische Ansteuerung geschlossen und öffnet bei einem vorgegebenen Druck. Dieser Öffnungsdruck kann von Umgebungsparametern, wie Drehzahl der Brennkraftmaschine, Massendurchfluss durch das Drucksteuerventil, Umgebungstemperatur usw., abhängen, ist jedoch in bestimmten Betriebszuständen grundsätzlich mit einer relativ hohen Genauigkeit bekannt. So ist z.B. bei direkteinspritzenden Benzin-Brennkraftmaschinen bei Leerlaufdrehzahl der Öffnungsdruck des Drucksteuerventils mit einer Genauigkeit von etwa ± 2,5 bar bekannt. Die Ungenauigkeiten des Drucksensors des Kraftstoffzumesssystems liegen üblicherweise wesentlich höher. Wenn während des Betriebs der Brennkraftmaschine bei Leerlaufdrehzahl das Drucksteuerventil öffnet, kann davon ausgegangen werden, dass in dem Hochdruckbereich ein Druck herrscht, der in etwa dem Öffnungsdruck des Drucksteuerventils entspricht. Dieser Druck wird dann als Referenzdruck für die Adaption der Sensorkennlinie herangezogen.According to yet another advantageous development of the present invention, it is proposed that the reference pressure of the opening pressure of a pressure control valve or a pressure limiting valve of the fuel metering system is used in a specific operating state of the internal combustion engine. A pressure control valve of the fuel metering system is usually normally closed with spring load. The pressure control valve is thus closed without electrical control and opens at a predetermined pressure. This Opening pressure may depend on environmental parameters, such as engine speed, mass flow through the pressure control valve, ambient temperature, etc., but is generally known in certain operating conditions with relatively high accuracy. For example, in direct-injection gasoline internal combustion engines at idle speed, the opening pressure of the pressure control valve with an accuracy of about ± 2.5 bar known. The inaccuracies of the pressure sensor of the fuel metering system are usually much higher. If, during operation of the internal combustion engine at idle speed, the pressure control valve opens, it can be assumed that prevails in the high pressure region, a pressure which corresponds approximately to the opening pressure of the pressure control valve. This pressure is then used as the reference pressure for the adaptation of the sensor characteristic.

Ein Kraftstoffzumesssystem mit einer bedarfsgesteuerten Hochdruckpumpe besitzt kein Drucksteuerventil, sondern nur ein passives, durch Federbelastung geschlossenes Überdruckventil -(Druckbegrenzungsventil) mit den gleichen Druckwerten wie ein Drucksteuerventil. Das erfindungsgemäße Verfahren kann hier in analoger Weise durchgeführt werden.A fuel metering system with an on-demand high pressure pump does not have a pressure control valve but only a passive, spring loaded closed relief valve - (pressure relief valve) with the same pressure values as a pressure control valve. The process of the invention can be carried out here in an analogous manner.

Diese erfindungsgemäße Weiterbildung hat darüber hinaus den Vorteil, dass Fehler des Kraftstoffzumesssystems während des Betriebs der Brennkraftmaschine erkannt werden können. Im Betrieb des Kraftfahrzeugs wird das Drucksteuerventil während bestimmter Betriebszustände stromlos geschaltet, d.h. geschlossen. Der sich in dem Hochdruckbereich einstellende Druck wird gemessen und mit einem Sollwert verglichen, der in Abhängigkeit von verschiedenen Betriebsparametern, insbesondere dem Massendurchfluss durch das Drucksteuerventil und der Temperatur des Drucksteuerventils, in dem Steuergerät der Brennkraftmaschine abgelegt ist. Falls der gemessene Druck über einen vorgegebenen Grenzwert hinaus von dem Sollwert abweicht, wird davon ausgegangen, dass ein Fehler des Kraftstoffzumesssystems vorliegt. Denkbare Betriebszustände für diesen Funktionstest sind beispielsweise während einer Schubabschaltung oder in einer Leerlaufphase der Brennkraftmaschine. Um den Temperatureinfluss auf den Funktionstest einzuschränken, ist es zusätzlich noch denkbar, den Funktionstest nur innerhalb eines vorgegebenen Temperaturbereichs auszuführen. Dies ist ohne Weiteres möglich, da der Funktionstest auf langsame Veränderungen des Kraftstoffzumesssystems reagiert und es üblicherweise ausreichend ist, den Funktionstest einmal pro Fahrt durchzuführen.This development according to the invention has the additional advantage that errors of the fuel metering system can be detected during operation of the internal combustion engine. During operation of the motor vehicle, the pressure control valve is switched off during certain operating states, ie closed. The pressure which is established in the high-pressure region is measured and compared with a desired value which, depending on various operating parameters, in particular the mass flow through the pressure control valve and the temperature of the pressure control valve, in the control device Internal combustion engine is stored. If the measured pressure deviates from the desired value beyond a predetermined limit value, it is assumed that there is a fault in the fuel metering system. Conceivable operating states for this function test are, for example, during a fuel cut or in an idling phase of the internal combustion engine. In order to limit the influence of temperature on the functional test, it is additionally conceivable to carry out the functional test only within a predetermined temperature range. This is easily possible since the function test reacts to slow changes in the fuel metering system and it is usually sufficient to carry out the functional test once per trip.

Gemäß einer bevorzugten Ausführungsform der vorliegenden Erfindung wird vorgeschlagen, dass das Verfahren während des Startvorgangs der Brennkraftmaschine nach dem Einschalten der Zündung und vor der Aktivierung des Anlassers automatisch durchgeführt wird. Während dieses Zeitraumes wird von der Vorförderpumpe ein Vordruck in dem Niederdruckbereich des Kraftstoffzumesssystems aufgebaut; in dem Hochdruckbereich liegt noch kein Einspritzdruck an.According to a preferred embodiment of the present invention, it is proposed that the method be carried out automatically during the starting process of the internal combustion engine after switching on the ignition and before the activation of the starter. During this period, a pre-pressure in the low-pressure region of the fuel metering system is established by the prefeed pump; in the high pressure area is still no injection pressure.

Des Weiteren wird vorgeschlagen, dass das Verfahren während des Nachlaufs der Brennkraftmaschine nach dem Abstellen der Brennkraftmaschine und vor dem Ausschalten der Zündung automatisch durchgeführt wird. Während des Nachlaufs liegt kein Einspritzdruck mehr in dem Hochdruckbereich des Kraftstoffzumesssystems an; die Vorförderpumpe baut weiterhin einen Vordruck auf.Furthermore, it is proposed that the method be carried out automatically during the overrun of the internal combustion engine after switching off the internal combustion engine and before switching off the ignition. During the wake, injection pressure is no longer present in the high pressure area of the fuel metering system; The prefeed pump continues to build up a form.

Schließlich wird vorgeschlagen, dass das Verfahren nach der Montage oder nach einer Reparatur des Kraftstoffzumesssystems der Brennkraftmaschine, insbesondere nach einem Austausch des Drucksensors, durchgeführt wird. Mit Hilfe eines geeigneten Testers kann die Vorförderpumpe derart angesteuert werden, dass sie einen Vordruck aufbaut. Die übrigen Elemente des Kraftstoffzumesssystems werden derart angesteuert, dass in dem Hochdruckbereich kein Einspritzdruck anliegt und dass der Vordruck aus dem Niederdruckbereich in den Hochdruckbereich geleitet wird.Finally, it is proposed that the method after assembly or after a repair of the fuel metering system of the internal combustion engine, in particular after replacement of the pressure sensor, is carried out. With the help of a suitable tester, the pre-feed pump can be controlled in such a way that it builds up a pre-pressure. The remaining elements of the fuel metering system are controlled in such a way that no injection pressure is applied in the high-pressure region and that the admission pressure is conducted from the low-pressure region into the high-pressure region.

Als Lösung der Aufgabe der vorliegenden Erfindung wird, ausgehend von der Vorrichtung zum Kalibrieren eines Drucksensors der eingangs genannten Art, des Weiteren vorgeschlagen, dass die Vorrichtung Mittel zur Durchführung des Verfahrens nach einem der Ansprüche 1 bis 11 aufweist.As a solution to the object of the present invention, starting from the device for calibrating a pressure sensor of the aforementioned type, further proposed that the device comprises means for performing the method according to one of claims 1 to 11.

Zeichnungendrawings

Ein bevorzugtes Ausführungsbeispiel der vorliegenden Erfindung wird im Folgenden anhand der Zeichnungen näher erläutert. Es zeigen:

Fig. 1
ein Ablaufdiagramm eines erfindungsgemäßen Verfahrens gemäß einer bevorzugten Ausführungsform; und
Fig. 2
ein Kraftstoffzumesssystem einer Brennkraftmaschine, in dem ein Drucksensor mittels des erfindungsgemäßen Verfahrens aus Fig. 1 kalibriert wird.
A preferred embodiment of the present invention will be explained in more detail below with reference to the drawings. Show it:
Fig. 1
a flow diagram of a method according to the invention according to a preferred embodiment; and
Fig. 2
a fuel metering system of an internal combustion engine, in which a pressure sensor by means of the inventive method Fig. 1 is calibrated.

Beschreibung der AusführungsbeispieleDescription of the embodiments

In Figur 1 ist ein Ablaufdiagramm einer bevorzugen Ausführungsform eines Verfahrens zum Kalibrieren eines Drucksensors eines Kraftstoffzumesssystems einer Brennkraftmaschine dargestellt. In Figur 2 ist ein als Common-Rail-Kraftstoff-Direkteinspritzungssystem ausgebildetes Kraftstoffzumesssystem dargestellt. Es weist eine Vorförderpumpe 1 und eine bedarfsgesteuerte bzw. bedarfsgeregelte Hochdruckpumpe 2 auf. Die Vorförderpumpe 1 ist als eine Elektrokraftstoffpumpe ausgebildet und fördert Kraftstoff aus einem Kraftstoff-Vorratsbehälter 3 in einen Niederdruckbereich ND des Kraftstoffzumesssystems. In dem Niederdruckbereich ND herrscht ein Vordruck von etwa 4 bar.In FIG. 1 FIG. 3 is a flow chart of a preferred embodiment of a method for calibrating a pressure sensor of a fuel metering system of an internal combustion engine. In FIG. 2 is a common rail fuel direct injection system trained fuel metering system shown. It has a prefeed pump 1 and an on-demand or demand-controlled high-pressure pump 2. The prefeed pump 1 is designed as an electric fuel pump and delivers fuel from a fuel reservoir 3 into a low-pressure region ND of the fuel metering system. In the low pressure range ND there is a pre-pressure of about 4 bar.

Die Hochdruckpumpe 2 fördert den Kraftstoff aus dem Niederdruckbereich ND in einen Hochdruckspeicher 4, den sog. Rail, in einem Hochdruckbereich HD des Kraftstoffzumesssystems. In dem Hochdruckspeicher 4 herrscht bei Benzin-Kraftstoff ein Druck von etwa 150 bis 200 bar und bei Diesel-Kraftstoff ein Druck von etwa 1500 bis 2000 bar. Von dem Hochdruckspeicher 4 zweigen vier Injektoren 5 ab, die betriebskenngrößenabhängig angesteuert werden und bei entsprechender Ansteuerung den Kraftstoff aus dem Hochdruckspeicher 4 mit dem dort anliegenden Einspritzdruck in Brennräume 6 der Brennkraftmaschine einspritzen.The high-pressure pump 2 conveys the fuel from the low-pressure region ND into a high-pressure reservoir 4, the so-called rail, in a high-pressure region HD of the fuel metering system. In the high-pressure accumulator 4 prevails at gasoline fuel pressure of about 150 to 200 bar and diesel fuel at a pressure of about 1500 to 2000 bar. From the high-pressure accumulator 4 four injectors branch off 5, which are controlled depending on the operating parameters and inject the fuel from the high-pressure accumulator 4 with the applied there injection pressure in combustion chambers 6 of the internal combustion engine with appropriate control.

In dem Hochdruckspeicher 4 ist des Weiteren ein-Drucksensor 7 angeordnet, durch den der in dem Hochdruckspeicher 4 herrschende Einspritzdruck ermittelt und ein entsprechendes elektrisches Signal an ein Steuergerät 8 der Brennkraftmaschine geleitet wird. Die Signalleitungen 9 sind in Figur 2 gestrichelt dargestellt. Schließlich zweigt aus dem Hochdruckspeicher 4 des Kraftstoffzumesssystems eine Drucksteuerleitung 10 ab, die über ein Drucksteuerventil 11 in den Niederdruckbereich ND mündet.In addition, a pressure sensor 7 is arranged in the high-pressure accumulator 4, by which the injection pressure prevailing in the high-pressure accumulator 4 is determined and a corresponding electrical signal is passed to a control unit 8 of the internal combustion engine. The signal lines 9 are in FIG. 2 shown in dashed lines. Finally, a pressure control line 10 branches off from the high-pressure accumulator 4 of the fuel metering system, which opens into the low-pressure region ND via a pressure control valve 11.

Aus dem Niederdruckbereich ND des Kraftstoffversorgungssystems zweigt eine Niederdruckleitung 12 ab, die über einen Niederdruckregler 13 zurück in den Kraftstoff-Vorratsbehälter 3 führt. Zwischen der Vorförderpumpe 1 und der Hochdruckpumpe 2 ist ein Filterelement 14 angeordnet. Von der Hochdruckpumpe 2 zweigt eine Leckleitung 15 ab, über die Lecköl bzw. Leckbenzin der Hochdruckpumpe 2 zurück in den Kraftstoffbehälter 3 fließen kann.From the low-pressure region ND of the fuel supply system branches off a low-pressure line 12, which leads via a low-pressure regulator 13 back into the fuel reservoir 3. Between the prefeed pump 1 and the high-pressure pump 2 is a Filter element 14 is arranged. From the high-pressure pump 2, a leak line 15 branches off, via which leak oil or gasoline of the high-pressure pump 2 can flow back into the fuel tank 3.

Der Drucksensor 7, wie er in dem Kraftstoffzumesssystem eingesetzt wird, weist einen statischen Offset-Fehler auf, d.h. der Nullpunkt wird nicht zuverlässig angezeigt. Ein Offset-Fehler führt dazu, dass der Messwert des Drucksensors. 7, insbesondere im Niederdruckbereich, große relative Abweichungen zu dem tatsächlich herrschenden Druckwert aufweist.The pressure sensor 7 as used in the fuel metering system has a static offset error, i. the zero point is not displayed reliably. An offset error causes the reading of the pressure sensor. 7, in particular in the low-pressure region, has large relative deviations from the actual prevailing pressure value.

In der Starterphase von direkt einspritzenden Common-Rail-Brennkraftmaschinen herrscht in der Regel ein niedriger Druck in dem Hochdruckspeicher 4. Die Brennkraftmaschine wird zumeist mit einem von der Vorförderpumpe 1 erzeugten niedrigen Vordruck gestartet, und erst später wird auf den Hochdruck umgeschaltet. Da die über die Injektoren 5 in die Brennräume 6 eingespritzte Kraftstoffmasse stark von dem in dem Hochdruckspeicher 4 herrschenden Einspritzdruck abhängig ist, müsste dieser in der Startphase der Brennkraftmaschine mit in die Berechnung der Einspritzzeit einbezogen werden. Aufgrund der oben beschriebenen Ungenauigkeiten des Drucksensors 7, insbesondere bei niedrigen Drücken, ist dies jedoch zumeist nicht möglich. Deshalb läuft nach dem Stand der Technik der Start einer direkt einspritzenden Brennkraftmaschine in der Regel ohne die Einrechnung des aktuellen, in dem Hochdruckbereich herrschenden Drucks ab.In the starter phase of direct-injection common-rail internal combustion engines there is usually a low pressure in the high-pressure accumulator 4. The internal combustion engine is usually started with a low pre-pressure generated by the feed pump 1, and only later is switched to the high pressure. Since the fuel mass injected into the combustion chambers 6 via the injectors 5 is heavily dependent on the injection pressure prevailing in the high-pressure accumulator 4, it would have to be included in the calculation of the injection time in the starting phase of the internal combustion engine. Due to the above-described inaccuracies of the pressure sensor 7, in particular at low pressures, but this is usually not possible. Therefore, according to the prior art, the start of a direct-injection internal combustion engine generally proceeds without the inclusion of the current pressure prevailing in the high-pressure region.

Um die Genauigkeit des Drucksensors 7 zu erhöhen, schlägt die Erfindung ein Verfahren zum Kalibrieren des Drucksensors 7 vor, bei dem ein in dem Hochdruckbereich HD herrschender niedriger Druck als Referenzdruck herangezogen wird. Der Referenzdruck ist mit einer hohen Genauigkeit bekannt oder kann mit einer hohen Genauigkeit bestimmt oder gemessen werden. Der in dem Hochdruckbereich herrschende niedrige Druck wird außerdem als Sensordruck durch den Drucksensor 7 gemessen. Nach dem Messen des Sensordrucks durch den Drucksensor 7 wird überprüft, ob sich der gemessene Sensordruck innerhalb vorgegebener Plausibilitätsschranken befindet. Die Kennlinie des Drucksensors 7 wird dann derart korrigiert, dass die Differenz aus Referenzdruck und Sensordruck minimiert wird.In order to increase the accuracy of the pressure sensor 7, the invention proposes a method for calibrating the pressure sensor 7, in which a low pressure prevailing in the high-pressure region HD is used as the reference pressure. The reference pressure is with a high accuracy known or can be determined or measured with high accuracy. The low pressure prevailing in the high-pressure region is also measured as the sensor pressure by the pressure sensor 7. After measuring the sensor pressure by the pressure sensor 7 is checked whether the measured sensor pressure is within predetermined plausibility limits. The characteristic of the pressure sensor 7 is then corrected so that the difference between the reference pressure and the sensor pressure is minimized.

Es gibt eine Vielzahl von Möglichkeiten, den Referenzdruck mit einer höheren Genauigkeit zu ermitteln als der Sensordruck gemessen werden kann. Als Referenzdruck kann bspw. der Umgebungsdruck herangezogen werden. Des Weiteren kann der in dem Hochdruckspeicher 4 herrschende niedrige Druck aber auch der von der Vorförderpumpe 1 erzeugt werden. Dazu wird die vorförderpumpe 1 des Kraftstoffzumesssystems aktiviert. Sie erzeugt einen Vordruck in dem Niederdruckbereich ND. Der Vordruck wird aus dem Niederdruckbereich ND in den Hochdruckbereich HD geleitet, indem die Einlassventile und die Auslassventile der Hochdruckpumpe 2 geöffnet sind. Als Referenzdruck wird dann der an dem Niederdruckregler 13 des Kraftstoffzumesssystems in dem Niederdruckbereich ND eingestellte Druck unter Berücksichtigung des Öffnungsdrucks der Einlassventile und Auslassventile der Hochdruckpumpe 2 herangezogen.There are a variety of ways to determine the reference pressure with a higher accuracy than the sensor pressure can be measured. As a reference pressure, for example, the ambient pressure can be used. Furthermore, the low pressure prevailing in the high-pressure accumulator 4 can also be generated by the prefeed pump 1. For this purpose, the prefeed pump 1 of the fuel metering system is activated. It generates a form in the low-pressure area ND. The admission pressure is led from the low-pressure area ND into the high-pressure area HD by opening the inlet valves and the outlet valves of the high-pressure pump 2. The pressure set at the low-pressure regulator 13 of the fuel metering system in the low-pressure region ND is then used as the reference pressure, taking into account the opening pressure of the inlet valves and outlet valves of the high-pressure pump 2.

Der Niederdruckregler 13 des Kraftstoffzumesssystems weist eine Genauigkeit von etwa ± 6 % auf, was bei einem Vordruck von etwa 4 bar ± 240 mbar entspricht. Die Einlass- und Auslassventile der Hochdruckpumpe 2 weisen eine Genauigkeit von ebenfalls etwa ± 6 % auf, so dass sich der Referenzdruck mit einer Genauigkeit von mindestens ± 500 mbar bestimmen lässt. Bei einem in einem Kraftstoffzumesssystem einer direkt einspritzenden Benzin-Brennkraftmaschine eingesetzten Hochdrucksensor 7 mit einem Messbereich von etwa 150 bar entspricht dies einer Genauigkeit von etwa ± 0,3 %. Mit einer so hohen Genauigkeit lässt sich der Sensordruck durch den Drucksensor 7 nicht bestimmen.The low pressure regulator 13 of the fuel metering system has an accuracy of about ± 6%, which corresponds to a pre-pressure of about 4 bar ± 240 mbar. The inlet and outlet valves of the high-pressure pump 2 also have an accuracy of about ± 6%, so that the reference pressure can be determined with an accuracy of at least ± 500 mbar. In one in a fuel metering system of a direct injection gasoline engine used high pressure sensor 7 with a measuring range of about 150 bar, this corresponds to an accuracy of about ± 0.3%. With such a high accuracy, the sensor pressure can not be determined by the pressure sensor 7.

Es ist auch denkbar, dass der Referenzdruck durch einen zumindest zeitweise in dem Hochdruckbereich HD angeordneten hochgenauen Niederdrucksensor (nicht dargestellt) gemessen wird. Ein solcher Niederdrucksensor kann zur Messung des niedrigen Drucks in den Hochdruckspeicher 4 eingeführt und nach der Messung wieder entnommen werden.It is also conceivable that the reference pressure is measured by a high-precision low-pressure sensor (not illustrated) arranged at least at times in the high-pressure region HD. Such a low-pressure sensor can be introduced for measuring the low pressure in the high-pressure accumulator 4 and removed again after the measurement.

Das Verfahren wird vorzugsweise während des Startvorgangs der Brennkraftmaschine nach dem Einschalten der Zündung und vor der Aktivierung des Anlassers automatisch durchgeführt. Während dieser Zeit ist zwar die Vorförderpumpe aktiviert, es wird jedoch noch kein Hochdruck in dem Hochdruckbereich HD erzeugt. Die Einlassventile und Auslassventile der Hochdruckpumpe 2 sind übelicherweise als passive Ventile ausgeführt. Durch Öffnen der Einlassventile und der Auslassventile der Hochdruckpumpe 2 wird der Vordruck in den Hochdruckspeicher geleitet.The method is preferably performed automatically during the starting process of the internal combustion engine after switching on the ignition and before the activation of the starter. Although during this time the prefeed pump is activated, however, no high pressure is generated in the high-pressure area HD. The intake valves and exhaust valves of the high pressure pump 2 are üblichicherweise designed as passive valves. By opening the inlet valves and the outlet valves of the high-pressure pump 2, the admission pressure is directed into the high-pressure accumulator.

Alternativ kann das Verfahren auch während des Nachlaufs der Brennkraftmaschine nach dem Abstellen der Brennkraftmaschine und vor dem Ausschalten der Zündung automatisch durchgeführt werden. Während des Nachlaufs ist die Zündung weiterhin eingeschaltet und das Steuergerät 8 fährt die verschiedenen Funktionen des Kraftfahrzeugs kontrolliert herunter. Zur Durchführung des Verfahrens während des Nachlaufs muss die Vorförderpumpe 1 gezielt angesteuert werden; und die Einlassventile und die Auslassventile der Hochddruckpumpe 2 müssen geöffnet sein.Alternatively, the method can also be carried out automatically during the after-running of the internal combustion engine after switching off the internal combustion engine and before switching off the ignition. During the caster, the ignition is still switched on and the control unit 8 drives down the various functions of the motor vehicle in a controlled manner. To carry out the process during the overrun, the prefeed pump 1 must be specifically controlled; and the intake valves and the exhaust valves of the high-pressure pump 2 must be open.

Das erfindungsgemäße Verfahren wird vorzugsweise nach der Montage oder nach einer Reparatur des Kraftstoffzumesssystems der Brennkraftmaschine, insbesondere nach einem Austausch des Drucksensors 7, durchgeführt.The inventive method is preferably according to the Assembly or after a repair of the fuel metering system of the internal combustion engine, in particular after replacement of the pressure sensor 7, carried out.

Es ist auch denkbar, das erfindungsgemäße Verfahren während des Betriebs der Brennkraftmaschine durchzuführen. Dazu kann als Referenzdruck bspw. der Öffnungsdruck des Drucksteuerventils 11 des Kraftstoffzumesssystems in einem bestimmten Betriebsszustand der Brennkraftmaschine herangezogen werden.It is also conceivable to carry out the method according to the invention during operation of the internal combustion engine. For this purpose, for example, the opening pressure of the pressure control valve 11 of the fuel metering system in a specific operating state of the internal combustion engine can be used as the reference pressure.

Das Drucksteuerventil 11 ist stromlos geschlossen mit Federbelastung. Das Drucksteuerventil 11 ist also ohne elektrische Ansteuerung geschlossen und öffnet bei einem vorgegebenen Öffnungsdruck. Der Öffnungsdruck kann von Umgebungsparametern, wie Drehzahl der Brennkraftmaschine, Massendurchfluss durch das Drucksteuerventil 11, Umgebungstemperatur usw., abhängen, ist jedoch in bestimmten Betriebszuständen grundsätzlich mit einer relativ hohen Genauigkeit bekannt. So ist z.B. bei direkt einspritzenden Benzin-Brennkraftmaschinen bei Leerlaufdrehzahl der Öffnungsdruck des Drucksteuerventils 11 mit einer Genauigkeit von etwa ± 2,5 bar bekannt. Die Ungenauigkeiten des Drucksensor 7 des Kraftstoffzumesssystems liegen üblicherweise wesentlich höher. Wenn während des Betriebs der Brennkraftmaschine bei Leerlaufdrehzahl das Drucksteuerventil 11 öffnet, kann davon ausgegangen werden, dass in dem Hochdruckspeicher 4 ein Druck herrscht, der in etwa dem Öffnungsdruck des Drucksteuerventils 11 entspricht. Dieser Druck wird dann als Referenzdruck für die Adaption der Sensorkennlinie herangezogen.The pressure control valve 11 is normally closed with spring load. The pressure control valve 11 is therefore closed without electrical control and opens at a predetermined opening pressure. The opening pressure may depend on environmental parameters such as engine speed, mass flow through the pressure control valve 11, ambient temperature, etc., but is generally known to be relatively accurate in certain operating conditions. For example, e.g. in directly injecting gasoline internal combustion engines at idle speed, the opening pressure of the pressure control valve 11 with an accuracy of about ± 2.5 bar known. The inaccuracies of the pressure sensor 7 of the fuel metering system are usually much higher. If, during operation of the internal combustion engine at idle speed, the pressure control valve 11 opens, it can be assumed that in the high-pressure accumulator 4, a pressure prevails, which corresponds approximately to the opening pressure of the pressure control valve 11. This pressure is then used as the reference pressure for the adaptation of the sensor characteristic.

Das erfindungsgemäße Verfahren in Figur 1 beginnt in dem Funktionsblock 20. In einem nachfolgenden Funktionsblock 21 wird die Zündung des Kraftfahrzeugs eingeschaltet. In einem Funktionsblock 22 wird die Vorförderpumpe 1 aktiviert, und in einem Funktionsblock 23 sind die Einlassventile und Auslassventile der Hochdruckpumpe 2 geöffnet. In einem Funktionsblock 24 wird der in dem Hochdruckspeicher 4 herrschende Referenzdruck aus einem Speicher des Steuergeräts 8 eingelesen. Der Referenzdruck wurde im Vorfeld aus dem an dem Niederdruckregler 13 eingestellten Druck unter Berücksichtigung des Öffnungsdrucks der Einlassventile und Auslassventile der Hochdruckpumpe 2 ermittelt und in dem Speicher abgespeichert.The inventive method in FIG. 1 begins in function block 20. In a subsequent function block 21 the ignition of the motor vehicle is turned on. In a function block 22, the prefeed pump 1 is activated, and in a functional block 23, the inlet valves and outlet valves of the high-pressure pump 2 are opened. In a functional block 24, the reference pressure prevailing in the high-pressure accumulator 4 is read from a memory of the control unit 8. The reference pressure was determined in advance from the pressure set at the low-pressure regulator 13 taking into account the opening pressure of the intake valves and exhaust valves of the high-pressure pump 2 and stored in the memory.

In einem Funktionsblock 25 wird dann der in dem Hochdruckspeicher 4 herrschende Druck von dem Drucksensor 7 gemessen. Die in dem Speicher des Steuergeräts 8 abgelegte Kennlinie des Drucksensors 7 wird in einem Funktionsblock 26 eingelesen. In einem Funktionsblock 27 wird die eingelesene Kennlinie des Drucksensor 7 derart verschoben, dass die Differenz aus Referenzdruck und Sensordruck minimiert wird. Die korrigierte Kennlinie wird dann in einem Funktionsblock 28 in dem Speicher des Steuergeräts 8 gespeichert. In einem Funktionsblock 29 ist das erfindungsgemäße Verfahren dann beendet.In a functional block 25, the pressure prevailing in the high-pressure accumulator 4 is then measured by the pressure sensor 7. The stored in the memory of the controller 8 characteristic of the pressure sensor 7 is read in a function block 26. In a function block 27, the read-in characteristic curve of the pressure sensor 7 is shifted such that the difference between the reference pressure and the sensor pressure is minimized. The corrected characteristic is then stored in a function block 28 in the memory of the controller 8. In a functional block 29, the inventive method is then completed.

Die Steuerung der Brennkraftmaschine durch das Steuergerät 8 erfolgt dann auf Grundlage der korrigierten Kennlinie des Drucksensors 7. Der Drucksensor 7 weist nunmehr eine so hohe Genauigkeit auf, dass die in dem Hochdruckspeicher 4 herrschenden Drücke auch während der Startphase (mit den dann in dem Hochdruckspeicher 4 herrschenden niedrigen Drücken) in die Berechnung der Einspritzzeit der Injektoren 5 einbezogen werden können.The control of the internal combustion engine by the control unit 8 is then based on the corrected characteristic of the pressure sensor 7. The pressure sensor 7 now has such a high accuracy that the pressure prevailing in the high-pressure accumulator 4 pressures during the start phase (with the then in the high-pressure accumulator 4th prevailing low pressures) can be included in the calculation of the injection time of the injectors 5.

Claims (8)

  1. Method for calibrating a pressure sensor (7) of a fuel metering system of an internal combustion engine, with the fuel metering system having a high-pressure pump (2) for feeding fuel from a low-pressure region (ND) into a high-pressure region (HD), having injectors (5), which can be activated in a manner dependent on characteristic operating variables, for metering the fuel from the high-pressure region (HD) into combustion chambers (6) of the internal combustion engine, and having the pressure sensor (7) for measuring the pressure in the high-pressure region (HD), with a pressure prevailing in the high-pressure region (HD) being determined as a reference pressure, with the pressure prevailing in the high-pressure region (HD) being measured by the pressure sensor (7) as a sensor pressure, and with the difference between the reference pressure and sensor pressure being formed, characterized in that a pressure is generated in the high-pressure region (HD) by virtue of a prefeed pump (1) of the fuel metering system being activated so as to generate a pressure in the low-pressure region (ND), and with the pressure being conducted from the low-pressure region (ND) into the high-pressure region (HD) and being taken into consideration as a reference pressure, with the characteristic curve of the pressure sensor (7) being corrected in such a way that the difference between the reference pressure and sensor pressure is minimized.
  2. Method according to Claim 1, characterized in that, after the measurement of the sensor pressure by the pressure sensor (7) and before the correction of the characteristic curve of the pressure sensor (7), it is checked whether the measured sensor pressure lies within predefined plausibility constraints.
  3. Method according to Claim 1 or 2, characterized in that the pressure is conducted from the low-pressure region (ND) through open inlet valves and outlet valves of the high-pressure pump (2) into the high-pressure region (HD), with the pressure which is set in the low-pressure region (ND) at a low-pressure regulator of the fuel metering system being taken into consideration, allowing for the opening pressure of the inlet valves and outlet valves of the high-pressure pump (2), as a reference pressure.
  4. Method according to Claim 1 or 2, characterized in that the reference pressure is measured by a high-precision low-pressure sensor which is arranged in the high-pressure region (HD) at least intermittently.
  5. Method according to one of Claims 1 to 4,
    characterized in that the method is carried out automatically during the starting process of the internal combustion engine after the ignition is switched on and before the starter is activated.
  6. Method according to one of Claims 1 to 5,
    characterized in that the method is carried out automatically during the run-down of the internal combustion engine after the internal combustion engine is shut down and before the ignition is switched off.
  7. Method according to one of Claims 1 to 6,
    characterized in that the method is carried out after the assembly of or after a repair to the fuel metering system of the internal combustion engine, in particular after an exchange of the pressure sensor (7).
  8. Device for calibrating a pressure sensor (7) of a fuel metering system of an internal combustion engine, with the fuel metering system having a high-pressure pump (2) for feeding fuel from a low-pressure region (ND) into a high-pressure region (HD), having injectors (5), which can be activated in a manner dependent on characteristic operating variables, for metering the fuel from the high-pressure region (HD) into combustion chambers (6) of the internal combustion engine, and having the pressure sensor (7) for measuring the pressure in the high-pressure region (HD), characterized in that the device has means for carrying out the method according to one of Claims 1 to 7.
EP01911382A 2000-01-29 2001-01-24 Method and device for calibrating a pressure sensor Expired - Lifetime EP1255926B1 (en)

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DE10003906 2000-01-29
DE10003906A DE10003906A1 (en) 2000-01-29 2000-01-29 Fuel dosing system pressure sensor calibrating process, involving using pressure in high-pressure zone as reference pressure
PCT/DE2001/000271 WO2001055573A2 (en) 2000-01-29 2001-01-24 Method and device for calibrating a pressure sensor

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US20030046990A1 (en) 2003-03-13
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EP1255926A2 (en) 2002-11-13
DE10003906A1 (en) 2001-08-09
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WO2001055573A3 (en) 2002-02-14
RU2260142C2 (en) 2005-09-10

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