DE102006029199B3 - Method and device for measuring a mass air flow by means of ultrasound - Google Patents

Abstract

In the method and apparatus for measuring the mass air flow in a pipe, a transmitter transducer array S radiates a directional ultrasonic wave US from one side of the pipe 4 obliquely to the flow direction x. A reflector R arranged on the opposite side reflects the directed ultrasonic wave onto a receiver transducer array E. The mass flow is then determined as a function of deviations between the actual impact position A _ist and a target impact position A _{soll of} the reflected ultrasonic wave US '.

Description

The The present invention relates to a method and an apparatus for measuring the mass flow of an air flow in a pipe by means of Ultrasound, in particular in an intake pipe of an internal combustion engine.

It already a measuring method is known in which the air mass flow in the intake manifold of an internal combustion engine is measured by means of ultrasound. In this measurement method, two coaxial ultrasonic transducers at opposite Sides of the pipe wall at an angle across from arranged. The two ultrasonic transducers are alternately as Sender and receiver used. Due to the so-called drift effect, by the air flow and superimpose the ultrasonic wave in the flow direction, result in different maturities of the ultrasonic wave in both Directions. From measurements of different maturities can then the mass flow can be calculated. A disadvantage of this measurement method is, however, the considerable one Effort, the runtime measurement and their evaluation require.

From the DE 103 44 895 A1 an ultrasonic transducer array with a transmitting part and a receiving part is known. The individual array elements of the transmitting part send out phase-shifted sound signals, which meet after reflection on the opposite pipe wall to the receiving part. The received at the receiving part sound intensity is evaluated by a receiving electronics, so that the center of gravity of the measured intensity distribution can be determined.

In addition, from the DE 10 2004 013 251 A1 an ultrasonic flow sensor for measuring the volume or mass flow of a fluid in a pipeline with at least one ultrasonic transducer capable of transmitting and receiving ultrasonic signals. The ultrasonic flow sensor comprises an array of a plurality of ultrasonic transducers, which is arranged on one side of the pipeline, and a reflection surface opposite the array, on which the emitted ultrasonic signals are reflected, and a receiving electronics, which evaluates the ultrasonic signal received by the ultrasonic transducers.

The DE 44 16 826 A1 describes an apparatus and a method for determining the flow velocity of liquids and gases in flow-through pipes of different cross-sections. The method is based on the effect of the carryover of an ultrasonic signal sent into the flowing medium. The ultrasound signal is generated by a microstructured ultrasound transmitter, and by selecting a suitable frequency and transmitter dimensions, a narrow ultrasound beam with a small aperture angle is emitted.

Of the The present invention is based on the object, a method and an apparatus for measuring the mass flow of an air flow in specify a tube by means of ultrasound, which a possible require low measurement and evaluation effort.

These The object is achieved by the in claim 1 defined method and in claim 4 defined device solved.

According to the present Invention is a directional ultrasonic wave by means of a transmitter-transducer array emitted from one side of the tube wall at an angle oblique to the flow direction. One on the opposite Side of the tube wall arranged reflector reflects the directed Ultrasonic wave to an actual landing position of a receiver transducer array, that on the same side of the tube wall as the transmitter transducer array is arranged. Due to the drift effect caused by the air flow there are deviations between the actual impact positions and a target impact position of the reflected ultrasonic wave, what is used to determine the mass flow. The beam angle the directional ultrasonic wave becomes dependent on these deviations regulated so that the actual impact position as close as possible to the target impact position is held. The mass flow can then be made to hold the Actual impact position required control variable for the control of the radiation angle be determined.

The Method and device according to the invention have the advantage that required in the prior art transit time measurement and their complicated evaluation can be avoided. Rather, it is at the invention essentially only the evaluation of a voltage distribution at the receiver transducer array necessary. Since the determination of the manipulated variable for readjusting the radiation angle and the determination of the mass flow can be carried out via maps can, a high speed of the method is ensured.

Further advantageous embodiments of the invention are defined in the dependent claims.

Based The drawings will be a preferred embodiment of the invention explained in more detail. It shows:

1 a schematic of an apparatus for measuring an air mass flow in a tube by means of ultrasound and

2 a schematic sketch of the measuring device of 1 with further details on an enlarged scale.

1 schematically shows a pipe wall 4 a pipe 2 , which is traversed by air with the schematically indicated velocity distribution v _{s, x} . At the pipe 2 it is in particular the intake pipe of an internal combustion engine (not shown).

In the 1 schematically illustrated device is used to measure the mass flow (the mass flow rate) of the air flow by means of ultrasound. In short, the device consists of a transmitter-transducer array S, a reflector R, a receiver-transducer array E and an evaluation device 6 that have a regulator circuit with a regulator 8th and an evaluation circuit 10 having.

As in 1 As can be seen, the transmitter transducer array S and the receiver transducer array E, offset in the flow direction x, are on the same side of the tube wall 4 arranged while the reflector R on the opposite side of the pipe wall 4 is arranged. The transmitter-transducer array S radiates a directional ultrasonic wave US slants toward the flow direction at a radiation angle α in the direction of the reflector R. In this case, the x-component v _{u , x of} the velocity v _{u of} the ultrasound wave US and the X-component v _{s, x of} the flow velocity v _{s of} the air flow overlap, which leads to a "drifting" of the ultrasound wave US The drift effect is the stronger The greater the flow velocity v _{T of} the air flow, the impact point of the ultrasonic wave US at the reflector R and the point of impact of the reflected ultrasonic wave US 'at the receiver transducer array E will change according to the present invention Exploited mass flow, as will be explained in more detail below.

It is now additionally on 2 Referenced. The transducer arrays S and E each consist of a group of individual ultrasonic transducers S ₁ ... S _n or E ₁ ... E _n , which are arranged next to one another in the flow direction. The transmitter-converter array S is powered by a high voltage source 12 energized. The individual ultrasonic transducers S ₁ ... S _{n of} the transmitter-transducer array S are delay elements 14 assigned by an AC source 16 with alternating voltages AC ₁ ... AC _{n are} fed. This offers the possibility of the individual ultrasonic transducers S ₁ ... S _n with different delay times t ₁ ... t _n time lag to control so that the time-shifted radiated individual ultrasonic waves US ₁ ... US _n directivity is given, whereby the forward- Ultrasonic wave US is formed.

The reflector R ( 1 ), which reflects the directional ultrasonic wave US, is designed to focus the reflected ultrasonic wave US 'in order to concentrate the energy of the ultrasonic wave incident on the receiver transducer array E to the smallest possible area. Since focusing ultrasound reflectors are known in the art, will not be discussed in detail.

As in 2 indicated by solid lines, the reflected ultrasonic wave US 'has a bell-shaped energy distribution G. The maximum of the bell-shaped energy distribution G is defined as the actual impact position A _is the reflected ultrasonic wave US'.

The control loop of the evaluation device 6 has the task to hold the actual impact point A _is at a target impact position A _soll . The evaluation facility regulates this 6 the radiation angle α of the directed ultrasonic wave US so that the reflected ultrasonic wave US ' _is adapted to a target ultrasonic wave US' _soll , whose energy distribution G is indicated by dashed lines.

For this purpose, the output signal 18 the receiver transducer array E an evaluation 20 fed, which evaluates the position of the maximum of the energy distribution G and thus the actual impact position A _is determined. The signal representing the actual impact position A _is transmitted via a line 22 a comparator 26 fed, via a line 24 a target impact position A _{is to be} displayed. The comparator 26 determines the deviation between A _is and A _is and gives a corresponding signal to the controller 8th from. The regulator 8th determines a manipulated variable from this deviation using a control algorithm 32 in the form of delay times t ₁ ... t _n , with which the delay elements 14 the individual ultrasonic transducers S ₁ ... S _n have drive in order to influence the emission angle α of the directed ultrasonic wave US so that the actual impact point A _is the reflected ultrasonic wave US 'close as possible to the target impact position A _{is to} be maintained.

The control algorithm of the controller 8th accesses schematically indicated maps 30 back, which _is a function of the actual impact position A containing the respective delay times for the actuation of the individual ultrasonic transducer to the receiver transducer array E. The maps 30 are used for the calibration of the various pipe diameters by means of test series Measuring device determined.

In this case, it is possible to proceed in such a way that firstly the delay times t ₁ ... T _n required with zero mass flow are determined and the sum of these delay times is defined as the total delay time zero. Based on this, the total delay times for increasing mass flows up to a maximum total delay time for the maximum mass flow are then determined.

It is understood that the determination of the delay times for the delay elements 14 in the maps 30 can also be done in other ways. In the illustrated embodiment, with the output of the regulator 8th a memory 34 arranged in which the regulator 8th output manipulated variable 32 (Delay times) can be stored. An appropriate memory is not essential.

The manipulated variable 32 , ie the delay times of the delay elements required for influencing the emission angle α 14 , is also the evaluation circuit 10 fed, the basis of schematically indicated maps 38 From this the mass flow is determined. Also the maps 38 are determined in test series for different pipe diameters during the calibration of the measuring device.

It is understood that the evaluation device 6 Part of a central electronic control unit (not shown) may be.

As already mentioned, the method and the device according to the invention have the advantage that the travel time measurement required in the prior art and the associated complicated evaluation are eliminated. Rather, only a voltage distribution at the receiver transducer array needs to be evaluated in the manner described. Since the impact position A _is the reflected ultrasonic wave US 'is permanently adjusted at the receiver transducer array E, there is only small changes in the actual landing position _A, which simplifies the evaluation accordingly. The mass flow is immediately out of the manipulated variable 32 , ie, the different delay times for the control of the transmitter-converter array won. Since the determination of the manipulated variable 32 as well as the determination of the mass flow via maps 30 respectively. 38 takes place, a high speed of the entire measurement process is guaranteed.

2

pipe

4

pipe wall

6

evaluation

8th

regulator

10

evaluation

12

High voltage source

14

delay elements

16

AC voltage source

18

output

20

evaluation element

22 24

management

26

comparator

30

maps

32

manipulated variable

34

Storage

36

maps

A _is

Actual impact position

A _should

Target impact position

AC ₁ ... AC _n

AC voltages

e

Receiver transducer array

E ₁ ... E _n

separate Ultrasonic transducer of the receiver transducer array

G

bell-shaped energy distribution

R

reflector

S

Transmitter transducer array

S ₁ ... S _n

separate Ultrasonic transducer of the transmitter transducer array

t ₁ ... t _n

delay times

US

ultrasonic wave

US ₁ ... US _n

separate ultrasonic waves

US '

reflected ultrasonic wave

US ' _should

reflected Target ultrasonic wave

v _s

flow rate the air

v _{s, x}

X component the flow velocity the air

v _u

 speed the ultrasonic wave US

v _{u, x}

X component the speed of the ultrasonic wave

x

flow direction

 α

Beam

Claims (11)

Method for measuring the mass flow of an air flow in a pipe by means of ultrasound, in particular in an intake pipe of an internal combustion engine, comprising the following steps: emitting a directional ultrasonic wave (US) with a transmitter transducer array (S) from one side of the pipe wall ( 4 ) at a beam angle (α) obliquely to the flow direction (x) by individual ultrasonic transducers (S ₁ ... S _n ) of the transmitter-transducer array (S) with different delay times (t ₁ ... t _n ) are controlled in a time-shift reflect and focusing the directional ultrasonic wave (US) with a reflector (R) on an opposite side of the tube wall (US Pat. 4 ) on a Actual impact position (A _is ) on the first-mentioned side of the pipe wall ( 4 ), Receiving the directional ultrasonic wave (US) with a receiver transducer array (E) offset from the transmitter transducer array (S), controlling the radiation angle (α) of the ultrasonic wave (US) as a function of the deviations between the actual Impact position (A _is ) and the target impact position (A _soll ) such that the actual impact position (A _is ) as close as possible to the target impact position (A _soll ) is maintained, and determining the mass flow in response to a for holding the Actual impact position (A _is ) required manipulated variable ( 32 ) for the control of the radiation angle (α). Device for measuring the mass flow of an air flow in a pipe by means of ultrasound, in particular in an intake pipe of an internal combustion engine, with a transmitter converter array (S) in which individual ultrasonic transducers (S1 ... Sn) with different delay times (t1 ... tn) can be controlled with a time delay and that on one side of the pipe wall ( 4 ) and a directional ultrasonic wave (US) radiates at a radiation angle (α), a receiver transducer array (E) on the same side of the pipe wall ( 4 ) in the flow direction offset to the transmitter-transducer array (W), a reflector (R) disposed on an opposite side of the tube wall ( 4 ) is arranged to reflect and focus the directional ultrasonic wave (US) to an actual landing position (Rist) on the receiver transducer array, and to an evaluation device (12). 6 ), which detects the actual impact position (Rist) and determines the mass flow as a function of deviations between the actual impact position (Rist) and a target impact position (A _soll ) highlighted by the effect of the drift, while the evaluation device ( 6 ) a control loop with a controller ( 8th ), which in dependence on the deviations between the actual impact position (Rist) and the target impact position (A _soll ) the radiation angle (α) of the directed ultrasonic wave (US) so controls that the actual impact position (Rist) as close as possible is held at the target impact position (A _soll ). Apparatus according to claim 2, characterized in that the evaluation device ( 6 ) an evaluation circuit ( 10 ), which depends on the manipulated variable required to hold the actual impact position ( 32 ) determines the mass flow for the control of the radiation angle (α). Device according to claim 2 or 3, characterized in that the regulator ( 8th ) for determining the manipulated variable ( 32 ) for the control of the emission angle (α) on maps determined in tests ( 30 ). Apparatus according to claim 3 or 4, characterized in that the evaluation circuit ( 10 ) for determining the mass flow on maps determined in tests ( 38 ). Device according to one of claims 3 to 5, characterized in that the output of the regulator ( 8th ) with a memory ( 34 ) for storing the manipulated variable ( 32 ) connected is. Device according to one of claims 1 to 6, characterized in that the transmitter-transducer array (S) comprises a group of individual ultrasonic transducers (S1 ... Sn) arranged side by side in the flow direction and via delay elements ( 14 ) can be controlled in a time-shifted manner in order to generate the directed ultrasound wave (US) emitted under variable emission angles (α). Device according to claim 7, characterized in that the output of the regulator ( 8th ) with the delay elements ( 14 ) connected is. Device according to one of claims 1 to 8, characterized that the receiver transducer array (E) has a group of individual ultrasonic transducers (E1 ... En), in the flow direction are arranged side by side to those of the reflector (R) reflected Capture ultrasonic wave (US '). Device according to one of claims 1 to 9, characterized the reflector (R) focuses the directional ultrasonic wave (US) so that on the receiver transducer array (E) incident reflected ultrasonic wave (US ') a bell-shaped energy distribution (G) has. Device according to claim 10, characterized in that that the actual impact position (Rist) of the reflected ultrasonic wave (US ') at the receiver transducer array (E) the position of the maximum of the bell-shaped energy distribution (G) is.