EP1957945A1 - Device for determining a mass flow - Google Patents

Device for determining a mass flow

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Publication number
EP1957945A1
EP1957945A1 EP06819596A EP06819596A EP1957945A1 EP 1957945 A1 EP1957945 A1 EP 1957945A1 EP 06819596 A EP06819596 A EP 06819596A EP 06819596 A EP06819596 A EP 06819596A EP 1957945 A1 EP1957945 A1 EP 1957945A1
Authority
EP
European Patent Office
Prior art keywords
mass flow
sound
flow
temperature
speed
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.)
Withdrawn
Application number
EP06819596A
Other languages
German (de)
French (fr)
Inventor
Rudolf Bierl
Martin Lesser
Andreas Meyer
Frank Steuber
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.)
Continental Automotive GmbH
Original Assignee
Continental Automotive GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Continental Automotive GmbH filed Critical Continental Automotive GmbH
Publication of EP1957945A1 publication Critical patent/EP1957945A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/86—Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
    • G01F15/02—Compensating or correcting for variations in pressure, density or temperature
    • G01F15/04—Compensating or correcting for variations in pressure, density or temperature of gases to be measured
    • G01F15/043—Compensating or correcting for variations in pressure, density or temperature of gases to be measured using electrical means

Definitions

  • the invention relates to a device for determining a mass flow of a gas flowing in a flow channel, each with sound transducers arranged at the ends of a measuring section, to which an evaluation unit is connected, which uses the transit times of sound signals to determine the flow rate of the gas and the Determines the speed of sound and determines a total mass flow on the basis of the flow rate and on the basis of pressure and temperature.
  • a device for determining a mass flow of a gas flowing in a flow channel, each with sound transducers arranged at the ends of a measuring section, to which an evaluation unit is connected, which uses the transit times of sound signals to determine the flow rate of the gas and the Determines the speed of sound and determines a total mass flow on the basis of the flow rate and on the basis of pressure and temperature.
  • Such a device is known from US Pat. No. 4,754,650.
  • the known device has two ultrasound transducers, which are arranged at the ends of a measuring section and are introduced on the wall of a flow channel. With the help of
  • the flow rate of the gas flowing in the flow channel and the speed of sound of the sound signal in the gas can then be determined from the transit times.
  • the average molecular weight of the gas flowing in the flow channel is determined from the determined speed of sound. This makes it possible to determine the mass flow of the gas flowing in the flow channel at a known pressure and at a known temperature.
  • an installation unit with an ultrasonic flow meter is known from EP 0 477 419, which is provided in particular for measuring the air mass in a motor vehicle engine.
  • This installation unit also comprises sound transducers arranged at the ends of a measuring section, with which the transit time of sound signals can be determined.
  • the flow rate of the air flowing in the flow channel can then be determined from the transit time of the sound signals.
  • the mass flow of the incoming air can then be determined.
  • the sucked-in air always has a certain proportion of air humidity and thus of water mass.
  • the invention has for its object to provide a device for determining the mass flow of a gas in the presence of another gas.
  • the evaluation unit determines the flow rate based on the transit times of the sound signals and determines a total mass flow based on pressure and a temperature. Furthermore, the evaluation unit determines the speed of sound from the running times and uses this to determine a proportion of a further gas flowing in the flow channel. The evaluation unit is then able to correct the total mass flow to the mass flow of the gas.
  • the device therefore does not require a separate sensor for the proportion of the further gas in the gas flow. Rather, the mass flow of the gas can also be determined in the presence of another gas, provided the pressure and temperature are known.
  • the evaluation unit is connected to a temperature sensor and a pressure sensor, which provide the evaluation unit with current values for temperature and pressure. So that the device can also be operated with fluctuating pressure and temperature.
  • the evaluation unit uses the speed of sound to determine the water content in an air flow and corrects the total mass flow to the mass flow of the air flow.
  • the device is therefore particularly suitable for measuring the air mass flow in the intake tract of an internal combustion engine for a motor vehicle.
  • Figure 1 is a block diagram for determining the mass flow in a flow channel
  • FIG. 1 shows a measuring device 1 with which the air mass flow in an intake pipe 2 of the internal combustion engine of a motor vehicle can be determined.
  • the measuring device 1 comprises ultrasound transducers 4 arranged in a wall 3 of the intake pipe 2, which define a measuring section 5.
  • the measuring section 5 runs across the intake pipe 2 at an angle to a flow direction 6.
  • the ultrasound transducers 4 are able to both transmit and receive ultrasound.
  • the ultrasonic transducers 4 transmit and receive ultrasonic signals 7 in the direction of flow 6.
  • Further ultrasonic signals 8 are transmitted and received against the direction of flow 6.
  • a runtime measuring circuit 9 which follows the ultrasound transducers 4 determines runtimes t d and for the ultrasound signals 8 runtimes t u .
  • the flow rate v of the gas in the intake pipe 2 is, apart from various interfering effects which can falsify the measurement result, proportional to ⁇ t / t u t d, where ⁇ t is the difference between the running times t u and t d .
  • the speed of sound c of the gas in the intake pipe 2 is then proportional ⁇ t / tu t d where ⁇ t is the sum of the running times.
  • the speed of sound c is determined in an arithmetic unit 10 downstream of the transit time measuring circuit 9 and the flow rate v in a further arithmetic unit 11 downstream of the transit time measuring circuit 9.
  • a temperature sensor 12 with a downstream temperature measurement circuit 13 and a pressure sensor 14 with a downstream pressure measurement circuit 15 are also arranged on the intake pipe 2.
  • the measured values for temperature T and pressure p supplied by the temperature measuring circuit 13 and the pressure measuring circuit 15 can be used in a computing unit 16 arranged downstream of the arithmetic unit 11 to determine a total mass flow. Since the total pressure is made up of the partial pressure of the air and the partial pressure of the water vapor, the total mass flow is not equal to the air mass flow. Rather, the total mass flow must be corrected with regard to the water vapor mass flow.
  • the mass fraction of water vapor in the total mass flow is determined in a further arithmetic unit 17 on the basis of the speed of sound c determined in the arithmetic unit 10 and the measured value for the temperature provided by the temperature measuring circuit 13, and in a further arithmetic unit 18 the total mass flow to the mass flow of air corrected.
  • the value for the air mass flow can then be transferred to an output 19 of an engine control.
  • the measured value of the air humidity can be passed on to the engine control in a further output 20.
  • the transit time measuring circuit 9, the temperature measuring circuit 13, the pressure measuring circuit 15 and the arithmetic units 10, 11 and 16 to 18 form an evaluation unit 21 which can be integrated into a physical device or can also be distributed over several physical devices.
  • the function of the arithmetic units 10, 11 and 17 to 18 can also be done with the help of software based on a
  • Microprocessor of the evaluation unit 21 runs, be accomplished.
  • the runtime measuring circuit 9, the temperature measuring circuit 13, pressure measuring circuit 15 and the arithmetic units 10, 11 and 16 to 18 represent functional units which can be set up using software or hardware.
  • the measuring device 1 can significantly influence the measurement result, in particular in the temperature range above 10 ° C. This will be explained in more detail with reference to FIG. 2.
  • FIG. 2 shows a diagram in which the dependence of the speed of sound c in air as a function of the relative air humidity p is entered.
  • the air mass flow drawn in by an internal combustion engine can be determined.
  • a gas mixture comprising two main components is present and the mass flow of one of the two main components is to be determined.

Abstract

A gas, whose mass flow is intended to be determined, flows through a flow channel (2). A device (1) for determining the mass flow has sound transducers (4) at the ends of a measurement path (5), which sound transducers (4) can be used to determine the delay time of sound signals (7, 8). The flow rate of the gas and the speed of sound can be determined from the delay time. A total mass flow is determined from the flow rate and also from pressure and temperature. The proportion of a further gas in the total mass flow can be determined from the speed of sound and the total mass flow can be corrected to the mass flow of the gas.

Description

Beschreibung description
Vorrichtung zur Bestimmung eines Massenstroms Die Erfindung betrifft eine Vorrichtung zur Bestimmung eines Massenstroms eines in einem Stromungskanal stromenden Gases mit jeweils an den Enden einer Messstrecke angeordneten Schallwandlern, denen eine Auswerteeinheit nachgeschaltet ist, die aus den Laufzeiten von Schallsignalen die Stromungs- geschwindigkeit des Gases und die Schallgeschwindigkeit bestimmt und die anhand der Stromungsgeschwindigkeit sowie anhand von Druck und Temperatur einen Gesamtmassenstrom bestimmt Eine derartige Vorrichtung ist aus der US 47 54 650 bekannt. Die bekannte Vorrichtung weist zwei an den Enden einer Messstrecke angeordnete Ultraschallwandler auf, die an der Wand eines Stromungskanals eingebracht sind. Mit Hilfe der Ultraschallwandler kann die Laufzeit von Schallsignalen entlang der Messstrecke bestimmt werden. Aus den Laufzeiten kann dann die Stromungsgeschwindigkeit des im Stromungskanal stromenden Gases und die Schallgeschwindigkeit des Schallsignals im Gas ermittelt werden. Bei der bekannten Vorrichtung wird aus der ermittelten Schallgeschwindigkeit das mittlere Molekularge- wicht des im Stromungskanal fließenden Gases bestimmt. Dadurch ist es möglich, bei bekanntem Druck und bei bekannter Temperatur den Massenstrom des im Stromungskanal stromenden Gases zu bestimmen. Weiterhin ist aus der EP 0 477 419 eine Einbaueinheit mit einem Ultraschalldurchflussmesser bekannt, die insbesondere zur Luftmassenmessung in einem Kraftfahrzeugmotor vorgesehen ist. Diese Einbaueinheit umfasst ebenfalls an den Enden einer Messstrecke angeordnete Schallwandler, mit denen sich die Laufzeit von Schallsignalen bestimmen lasst. Aus der Laufzeit der Schallsignale kann dann die Stromungsgeschwindigkeit der im Stromungskanal stromenden Luft bestimmt werden. Über einen zusatzlichen Temperatursensor und einen weiteren Drucksensor kann dann der Massenstrom der einströmenden Luft ermittelt werden. Die angesaugte Luft weist jedoch immer einen gewissen Anteil an Luftfeuchtigkeit und damit an Wassermasse auf. The invention relates to a device for determining a mass flow of a gas flowing in a flow channel, each with sound transducers arranged at the ends of a measuring section, to which an evaluation unit is connected, which uses the transit times of sound signals to determine the flow rate of the gas and the Determines the speed of sound and determines a total mass flow on the basis of the flow rate and on the basis of pressure and temperature. Such a device is known from US Pat. No. 4,754,650. The known device has two ultrasound transducers, which are arranged at the ends of a measuring section and are introduced on the wall of a flow channel. With the help of the ultrasonic transducers, the transit time of sound signals along the measuring section can be determined. The flow rate of the gas flowing in the flow channel and the speed of sound of the sound signal in the gas can then be determined from the transit times. In the known device, the average molecular weight of the gas flowing in the flow channel is determined from the determined speed of sound. This makes it possible to determine the mass flow of the gas flowing in the flow channel at a known pressure and at a known temperature. Furthermore, an installation unit with an ultrasonic flow meter is known from EP 0 477 419, which is provided in particular for measuring the air mass in a motor vehicle engine. This installation unit also comprises sound transducers arranged at the ends of a measuring section, with which the transit time of sound signals can be determined. The flow rate of the air flowing in the flow channel can then be determined from the transit time of the sound signals. About one additional temperature sensor and another pressure sensor, the mass flow of the incoming air can then be determined. However, the sucked-in air always has a certain proportion of air humidity and thus of water mass.
Aufgrund der zusatzlichen Wassermasse ist der Messwert der Luftmasse fehlerbehaftet. Due to the additional water mass, the measured value of the air mass is faulty.
Ausgehend von diesem Stand der Technik liegt der Erfindung die Aufgabe zugrunde, eine Vorrichtung zur Bestimmung des Massenstromes eines Gases bei Anwesenheit eines weiteren Gases zu schaffen. Based on this prior art, the invention has for its object to provide a device for determining the mass flow of a gas in the presence of another gas.
Diese Aufgabe wird durch eine Vorrichtung mit den Merkmalen des unabhängigen Anspruchs gelost. In davon abhangigen An- spruchen sind vorteilhafte Ausgestaltungen und Weiterbildungen angegeben . This object is achieved by a device with the features of the independent claim. Advantageous refinements and developments are specified in the dependent claims.
Bei der Vorrichtung bestimmt die Auswerteeinheit anhand der Laufzeiten der Schallsignale die Stromungsgeschwindigkeit und ermittelt anhand von Druck und eines Temperatur einen Gesamtmassenstrom. Ferner ermittelt die Auswerteeinheit aus den Laufzeiten die Schallgeschwindigkeit und ermittelt daraus einen Anteil eines im Stromungskanal fließenden weiteren Gases. Die Auswerteeinheit ist dann dazu in der Lage, den Gesamtmassenstrom auf den Massenstrom des Gases zu korrigieren . In the device, the evaluation unit determines the flow rate based on the transit times of the sound signals and determines a total mass flow based on pressure and a temperature. Furthermore, the evaluation unit determines the speed of sound from the running times and uses this to determine a proportion of a further gas flowing in the flow channel. The evaluation unit is then able to correct the total mass flow to the mass flow of the gas.
Bei der Vorrichtung ist somit kein separater Sensor für den Anteil des weiteren Gases am Gasstrom notig. Vielmehr kann der Massenstrom des Gases auch bei Anwesenheit eines weiteren Gases bestimmt werden, sofern Druck und Temperatur bekannt sind . The device therefore does not require a separate sensor for the proportion of the further gas in the gas flow. Rather, the mass flow of the gas can also be determined in the presence of another gas, provided the pressure and temperature are known.
Bei einer bevorzugten Ausfuhrungsform ist die Auswerteeinheit an einen Temperatursensor und einen Drucksensor angeschlossen, die der Auswerteeinheit aktuelle Werte für Temperatur und Druck zur Verfugung stellen. Damit kann die Vorrichtung auch bei schwankendem Druck und variierender Temperatur betrieben werden. In a preferred embodiment, the evaluation unit is connected to a temperature sensor and a pressure sensor, which provide the evaluation unit with current values for temperature and pressure. So that the device can also be operated with fluctuating pressure and temperature.
Bei einer weiteren bevorzugten Ausfuhrungsform bestimmt die Auswerteeinheit anhand der Schallgeschwindigkeit den Wasseranteil in einem Luftstrom und korrigiert den Gesamtmassenstrom auf den Massenstrom des Luftstromes. In a further preferred embodiment, the evaluation unit uses the speed of sound to determine the water content in an air flow and corrects the total mass flow to the mass flow of the air flow.
Damit eignet sich die Vorrichtung insbesondere zur Messung des Luftmassenstroms im Ansaugtrakt eines Verbrennungsmotors für ein Kraftfahrzeug. The device is therefore particularly suitable for measuring the air mass flow in the intake tract of an internal combustion engine for a motor vehicle.
Weitere Einzelheiten und Vorteile der Erfindung gehen aus der nachfolgenden Beschreibung hervor, in der Ausfuhrungsbeispie- Ie der Erfindung anhand der beigefugten Zeichnung im Einzelnen erläutert werden. Es zeigen: Further details and advantages of the invention will become apparent from the following description, in which exemplary embodiments of the invention are explained in detail with reference to the accompanying drawing. Show it:
Figur 1 ein Blockschaltbild zur Bestimmung des Massenstroms in einem Stromungskanal; und Figure 1 is a block diagram for determining the mass flow in a flow channel; and
Figur 2 ein Diagramm, aus dem die Abhängigkeit der Schallgeschwindigkeit von der relativen Luftfeuchtigkeit für verschiedene Temperaturen hervorgeht. Figur 1 zeigt eine Messvorrichtung 1, mit der sich der Luftmassenstrom in einem Ansaugrohr 2 des Verbrennungsmotors eines Kraftfahrzeugs bestimmen lasst. Die Messvorrichtung 1 umfasst in einer Wand 3 des Ansaugrohres 2 angeordnete Ultraschallwandler 4, die eine Messstrecke 5 definieren. Die Messstrecke 5 verlauft quer durch das Ansaugrohr 2 im Winkel zu einer Stromungsrichtung 6. Figure 2 is a diagram showing the dependence of the speed of sound on the relative humidity for different temperatures. FIG. 1 shows a measuring device 1 with which the air mass flow in an intake pipe 2 of the internal combustion engine of a motor vehicle can be determined. The measuring device 1 comprises ultrasound transducers 4 arranged in a wall 3 of the intake pipe 2, which define a measuring section 5. The measuring section 5 runs across the intake pipe 2 at an angle to a flow direction 6.
Die Ultraschallwandler 4 sind in der Lage, sowohl Ultraschall zu senden als auch zu empfangen. So werden von den Ultra- schallwandlern 4 Ultraschallsignale 7 in Stromungsrichtung 6 ausgesandt und empfangen. Weitere Ultraschallsignale 8 werden entgegen der Stromungsrichtung 6 ausgesandt und empfangen. Für die Ultraschallsignale 7 bestimmt eine den Ultraschallwandlern 4 nachgeschaltete Laufzeitmessschaltung 9 Laufzeiten td und für die Ultraschallsignale 8 Laufzeiten tu . Die Stromungsgeschwindigkeit v des Gases im Ansaugrohr 2 ist abgese- hen von verschiedenen störenden Effekten, die das Messergebnis verfalschen können, proportional Δt/tu td wobei Δt die Differenz der Laufzeiten tu und td ist. Die Schallgeschwindigkeit c des Gases im Ansaugrohr 2 ist dann proportional ∑t/tu td wobei ∑t die Summe der Laufzeiten ist. The ultrasound transducers 4 are able to both transmit and receive ultrasound. Thus, the ultrasonic transducers 4 transmit and receive ultrasonic signals 7 in the direction of flow 6. Further ultrasonic signals 8 are transmitted and received against the direction of flow 6. For the ultrasound signals 7, a runtime measuring circuit 9 which follows the ultrasound transducers 4 determines runtimes t d and for the ultrasound signals 8 runtimes t u . The flow rate v of the gas in the intake pipe 2 is, apart from various interfering effects which can falsify the measurement result, proportional to Δt / t u t d, where Δt is the difference between the running times t u and t d . The speed of sound c of the gas in the intake pipe 2 is then proportional ∑t / tu t d where ∑t is the sum of the running times.
Die Schallgeschwindigkeit c wird in einem der Laufzeitenmess- schaltung 9 nachgeschalteten Rechenwerk 10 und die Stromungsgeschwindigkeit v in einem weiteren der Laufzeitmessschaltung 9 nachgeschalteten Rechenwerk 11 bestimmt. The speed of sound c is determined in an arithmetic unit 10 downstream of the transit time measuring circuit 9 and the flow rate v in a further arithmetic unit 11 downstream of the transit time measuring circuit 9.
Am Ansaugrohr 2 sind ferner ein Temperatursensor 12 mit nachgeschalteter Temperaturmessschaltung 13 und ein Drucksensor 14 mit nachgeschalteter Druckmessschaltung 15 angeordnet. Die von der Temperaturmessschaltung 13 und der Druckmess- Schaltung 15 gelieferten Messwerte für Temperatur T und Druck p können in ein dem Rechenwerk 11 nachgeordnetem Rechenwerk 16 dazu verwendet werden, einen Gesamtmassenstrom zu bestimmen. Da sich der Gesamtdruck aus dem Partialdruck der Luft und dem Partialdruck des Wasserdampfes zusammensetzt, ist der Gesamtmassenstrom nicht gleich dem Luftmassenstrom. Vielmehr muss der Gesamtmassenstrom hinsichtlich des Wasserdampfmas- senstromes korrigiert werden. Zu diesem Zweck wird in einem weiteren Rechenwerk 17 anhand der im Rechenwerk 10 bestimmten Schallgeschwindigkeit c und dem von der Temperaturmessschal- tung 13 gelieferten Messwertes für die Temperatur der Massenanteil des Wasserdampf am Gesamtmassenstrom bestimmt und in einem weiteren Rechenwerk 18 der Gesamtmassenstrom auf den Massenstrom der Luft korrigiert. Der Wert für den Luftmassenstrom kann dann an einem Ausgang 19 einer Motorsteuerung übergeben werden. Ferner kann an einem weiteren Ausgang 20 der Messwert der Luftfeuchte an die Motorsteuerung weitergegeben werden. A temperature sensor 12 with a downstream temperature measurement circuit 13 and a pressure sensor 14 with a downstream pressure measurement circuit 15 are also arranged on the intake pipe 2. The measured values for temperature T and pressure p supplied by the temperature measuring circuit 13 and the pressure measuring circuit 15 can be used in a computing unit 16 arranged downstream of the arithmetic unit 11 to determine a total mass flow. Since the total pressure is made up of the partial pressure of the air and the partial pressure of the water vapor, the total mass flow is not equal to the air mass flow. Rather, the total mass flow must be corrected with regard to the water vapor mass flow. For this purpose, the mass fraction of water vapor in the total mass flow is determined in a further arithmetic unit 17 on the basis of the speed of sound c determined in the arithmetic unit 10 and the measured value for the temperature provided by the temperature measuring circuit 13, and in a further arithmetic unit 18 the total mass flow to the mass flow of air corrected. The value for the air mass flow can then be transferred to an output 19 of an engine control. Furthermore, can the measured value of the air humidity can be passed on to the engine control in a further output 20.
Es sei angemerkt, dass die Laufzeitmessschaltung 9, die Temperaturmessschaltung 13, die Druckmessschaltung 15 und die Rechenwerke 10, 11 sowie 16 bis 18 eine Auswerteeinheit 21 bilden, die in ein physikalisches Gerat integriert sein kann oder aber auch über mehrere physikalische Gerate verteilt sein kann. Die Funktion der Rechenwerke 10, 11 sowie 17 bis 18 kann dabei auch mit Hilfe von Software, die auf einemIt should be noted that the transit time measuring circuit 9, the temperature measuring circuit 13, the pressure measuring circuit 15 and the arithmetic units 10, 11 and 16 to 18 form an evaluation unit 21 which can be integrated into a physical device or can also be distributed over several physical devices. The function of the arithmetic units 10, 11 and 17 to 18 can also be done with the help of software based on a
Mikroprozessor der Auswerteeinheit 21 lauft, bewerkstelligt werden . Microprocessor of the evaluation unit 21 runs, be accomplished.
Insofern stellen die Laufzeitenmessschaltung 9, die Tempera- turmessschaltung 13, Druckmessschaltung 15 sowie die Rechenwerke 10, 11 und 16 bis 18 funktionelle Einheiten dar, die mit Software oder Hardware eingerichtet werden können. In this respect, the runtime measuring circuit 9, the temperature measuring circuit 13, pressure measuring circuit 15 and the arithmetic units 10, 11 and 16 to 18 represent functional units which can be set up using software or hardware.
Ferner sei angemerkt, dass die Messvorrichtung 1 insbesondere im Temperaturbereich oberhalb von 10 °C das Messergebnis wesentlich beeinflussen kann. Dies sei anhand Figur 2 naher erläutert . Furthermore, it should be noted that the measuring device 1 can significantly influence the measurement result, in particular in the temperature range above 10 ° C. This will be explained in more detail with reference to FIG. 2.
Figur 2 zeigt ein Diagramm, in das die Abhängigkeit der Schallgeschwindigkeit c in Luft in Abhängigkeit von der relativen Luftfeuchtigkeit p eingetragen ist. Eine Kurve 22 zeigt die Änderung der Schallgeschwindigkeit c bei einer Temperatur T = 10 °C an. Eine weitere Kurve 23 veranschaulicht die Änderung der Luftgeschwindigkeit in Abhängigkeit von der relativen Luftfeuchtigkeit p bei der Temperatur T = 20 °C und eine weitere Kurve 24 die Variation der Schallgeschwindigkeit c bei einer Temperatur T = 30 °C. FIG. 2 shows a diagram in which the dependence of the speed of sound c in air as a function of the relative air humidity p is entered. A curve 22 shows the change in the speed of sound c at a temperature T = 10 ° C. A further curve 23 illustrates the change in air speed as a function of the relative air humidity p at the temperature T = 20 ° C. and a further curve 24 the variation in the speed of sound c at a temperature T = 30 ° C.
Anhand Figur 2 wird deutlich, dass die Änderung der Schallge- schwindigkeit verhältnismäßig stark von der Temperatur T abhangt. Die Abhängigkeit der Schallgeschwindigkeit c von der relativen Luftfeuchtigkeit p ist dagegen eher schwach ausgeprägt, wobei die Abhängigkeit umso großer wird, je hoher die Temperatur ist, da mit zunehmender Lufttemperatur der absolute Masseanteil des Wasserdampfs in Luft stark zunimmt. Bei einer Lufttemperatur von T = 10 °C betragt der Unter- schied der Schallgeschwindigkeit c bei der Luftfeuchtigkeit p = 0 % zu der Schallgeschwindigkeit c bei der Luftfeuchtigkeit p = 100 % etwa 0,5 m/s. Die gleiche Änderung der Schallgeschwindigkeit c wird auch durch eine Temperaturanderung um etwa 1 °C hervorgerufen. Bei der Lufttemperatur T = 30 °C betragt der Unterschied zwischen den Schallgeschwindigkeiten c bei den Luftfeuchtigkeiten p = 0 % und p = 100 % etwa 2,5 m/s . It is clear from FIG. 2 that the change in the speed of sound depends relatively strongly on the temperature T. The dependence of the speed of sound c on the relative humidity p is rather weak pronounced, the higher the temperature, the greater the dependence, since the absolute mass fraction of water vapor in air increases sharply with increasing air temperature. At an air temperature of T = 10 ° C, the difference between the speed of sound c at air humidity p = 0% and the speed of sound c at air humidity p = 100% is approximately 0.5 m / s. The same change in the speed of sound c is also caused by a temperature change of about 1 ° C. At the air temperature T = 30 ° C, the difference between the sound velocities c at the air humidity p = 0% and p = 100% is about 2.5 m / s.
Anhand Figur 2 wird deutlich, dass für eine Wasserkorrektur die Temperatur nach Möglichkeit mit einer Messungenauigkeit kleiner 1 °C bestimmt werden muss. Allerdings ist die Messungenauigkeit bei der Bestimmung der Temperatur bei Temperaturen unterhalb von 20 °C, insbesondere unterhalb 10 °C nicht unbedingt relevant, da bei diesen Temperaturen der absolute Wassergehalt in Luft gering ist, so dass das Messergebnis für den Luftmassenstrom nicht wesentlich verfälscht wird. It is clear from FIG. 2 that for a water correction the temperature has to be determined if possible with a measurement inaccuracy of less than 1 ° C. However, the measurement inaccuracy when determining the temperature at temperatures below 20 ° C, especially below 10 ° C, is not necessarily relevant, since at these temperatures the absolute water content in air is low, so that the measurement result for the air mass flow is not significantly falsified.
Mit der hier beschriebenen Vorrichtung lasst sich insbesondere der von einem Verbrennungsmotor angesaugte Luftmassenstrom bestimmen. Denkbar sind aber auch anderen Anwendungen, in denen ein Gasgemisch, das zwei Hauptkomponenten umfasst, vorliegt und der Massenstrom einer der beiden Hauptkomponenten bestimmt werden soll. With the device described here, in particular the air mass flow drawn in by an internal combustion engine can be determined. However, other applications are also conceivable in which a gas mixture comprising two main components is present and the mass flow of one of the two main components is to be determined.

Claims

Patentansprüche Claims
1. Vorrichtung zur Bestimmung eines Massenstroms eines in einem Stromungskanal (2) stromenden Gases mit jeweils an den Enden einer Messstrecke (5) angeordneten Schallwandlern (4), denen eine Auswerteeinheit (21) nachgeschaltet ist, die aus den Laufzeiten von Schallsignalen (7, 8) die Stromungsgeschwindigkeit des Gases und die Schallgeschwindigkeit bestimmt und die anhand der Stromungsgeschwindigkeit sowie anhand von Druck und Temperatur einen Gesamtmassenstrom bestimmt, 1. Device for determining a mass flow of a gas flowing in a flow channel (2), each having sound transducers (4) arranged at the ends of a measuring section (5), to which an evaluation unit (21) is connected, which is derived from the transit times of sound signals (7, 8) determines the flow rate of the gas and the speed of sound and which determines a total mass flow on the basis of the flow rate and on the basis of pressure and temperature,
d a d u r c h g e k e n n z e i c h n e t, d a s s die Auswerteeinheit (21) anhand der Schallgeschwindigkeit einen Anteil eines im Stromungskanal (2) stromenden weiteren Gases ermittelt und den Gesamtmassenstrom auf den Massenstrom des Gases korrigiert. Because of this, the evaluation unit (21) uses the speed of sound to determine a proportion of another gas flowing in the flow channel (2) and corrects the total mass flow to the mass flow of the gas.
2. Vorrichtung nach Anspruch 1, 2. Device according to claim 1,
d a d u r c h g e k e n n z e i c h n e t, d a s s ein Temperatursensor (12) die Auswerteeinheit (21) mit einem Wert für die Temperatur des in dem Stromungskanal (2) stromenden Gases beaufschlagt. Because of this, a temperature sensor (12) acts upon the evaluation unit (21) with a value for the temperature of the gas flowing in the flow channel (2).
3. Vorrichtung nach Anspruch 1 oder 2, 3. Device according to claim 1 or 2,
d a d u r c h g e k e n n z e i c h n e t, d a s s ein Drucksensor (14) die Auswerteeinheit (21) mit einem Wert für den im Stromungskanal (2) herrschenden Druck beaufschlagt . Because of this, a pressure sensor (14) acts on the evaluation unit (21) with a value for the pressure prevailing in the flow channel (2).
4. Vorrichtung nach einem der Ansprüche 1 bis 3, 4. Device according to one of claims 1 to 3,
d a d u r c h g e k e n n z e i c h n e t, d a s s der Stromungskanal ein Ansaugrohr (2) eines Verbrennungsmotors eines Kraftfahrzeugs ist. d a d u r c h g e k e n n z e i c h n e t that the flow channel is an intake pipe (2) of an internal combustion engine of a motor vehicle.
5. Vorrichtung nach einem der Ansprüche 1 bis 4, 5. Device according to one of claims 1 to 4,
d a d u r c h g e k e n n z e i c h n e t, d a s s die Auswerteeinheit (21) anhand der Schallgeschwindigkeit und der Temperatur den Anteil des im Stromungskanal stromenden Wasserdampfes ermittelt und den Gesamtmassenstrom auf den Luftmassenstrom korrigiert. characterized in that the evaluation unit (21) uses the speed of sound and the temperature to determine the proportion of the water vapor flowing in the flow channel and corrects the total mass flow to the air mass flow.
6. Vorrichtung nach Anspruch 4 oder 5, 6. The device according to claim 4 or 5,
d a d u r c h g e k e n n z e i c h n e t, d a s s die Auswerteeinheit (21) den Gesamtmassenstrom bei einer Temperatur oberhalb von 10 °C hinsichtlich des Wasserdampfan- teils korrigiert. That is, the evaluation unit (21) corrects the total mass flow at a temperature above 10 ° C with regard to the water vapor content.
EP06819596A 2005-12-08 2006-11-20 Device for determining a mass flow Withdrawn EP1957945A1 (en)

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DE102005059062A DE102005059062B4 (en) 2005-12-08 2005-12-08 Apparatus for determining a mass flow
PCT/EP2006/068640 WO2007065785A1 (en) 2005-12-08 2006-11-20 Device for determining a mass flow

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US (1) US8047082B2 (en)
EP (1) EP1957945A1 (en)
KR (1) KR20080080506A (en)
CN (1) CN101326427A (en)
DE (1) DE102005059062B4 (en)
WO (1) WO2007065785A1 (en)

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DE102005059062A1 (en) 2007-06-14
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CN101326427A (en) 2008-12-17
DE102005059062B4 (en) 2009-08-27
WO2007065785A1 (en) 2007-06-14

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