WO2008138671A1

WO2008138671A1 - Ultrasound flow meter installation unit

Info

Publication number: WO2008138671A1
Application number: PCT/EP2008/053528
Authority: WO
Inventors: Rudolf Bierl; Martin Lesser; Andreas Meyer; Stephen Setescak; Frank Steuber
Original assignee: Continental Automotive Gmbh
Priority date: 2007-05-14
Filing date: 2008-03-26
Publication date: 2008-11-20
Also published as: DE102007022513B4; DE102007022513A1

Abstract

The invention relates to an inexpensive and reliably operating device for measuring flow, even in ranges of high and very high volume flows, an air mass sensor having two ultrasound converters (3, 4) disposed in a tube (2) constructed such that at least two ultrasound converters (3, 4) having electronics (5) provided near the ultrasonic converters (3, 4) are disposed in the tube cross-section for capturing a representative flow cross-section and the air mass sensor in the tube (2) is at least partially enclosed by at least one flow guide vane (8).

Description

description

XKiTRAS CHALL FLOWMETER INSTALLATION UNIT

The present invention relates to an air mass sensor.

In a known manner, an air-fuel mixture is brought under compression to combustion in internal combustion engines. The power output of the internal combustion engine depends on the ratio of fuel mass to air mass. The measurement of a respective air mass is carried out with an air mass sensor, which sits in the intake tract of the internal combustion engine. Due to the high economic importance of the motor vehicle sector is discussed below without limiting the use of inventive and generally applicable flow sensors only to the application for determining a sucked or otherwise supplied to an internal combustion engine air mass.

Numerous modern internal combustion engines are today equipped with an exhaust gas turbocharger, which causes a pre-compression of the air mass. Has been carried out at the beginning of the development of internal combustion engines attempting a pre-compression of an internal combustion engine air supplied with the aim of increasing the engine power by increasing the air flow and fuel flow per stroke, so today the charging of gasoline internal combustion engines is no longer primarily from the performance aspect but as a way to save fuel and reduce pollutants. In a known manner, a respective exhaust gas flow energy for pre-compression of the air mass flow through a current running in the exhaust gas turbine with it mechanically coupled fresh air compressor withdrawn, so that, for example, a diesel engine no longer as a naturally aspirated engine, but as a supercharged engine with charge air pressures of up to 1 5 bar or even 2.5 bar with significant increase in performance and reduced Pollutant emissions works. For this purpose, of course, an air mass in a predetermined ratio to admit a particular fuel mass, so that an air mass sensor plays a significant role in the economy and emission reduction of an internal combustion engine.

Since it depends on the mass ratios of fuel and air in the chemical process of combustion in any operating condition of an internal combustion engine, the mass flow of the intake / charge air is also continuously as accurately as possible to measure. Depending on the engine power of the internal combustion engine, the maximum air mass flow to be measured is in the range of 400 to approx. 1000 kg / h. Due to the low idle demand of modern internal combustion engines, the ratio of a minimum to a maximum air flow rate is between 1:90 to about 1: 100.

An air mass sensor can operate as a mass flow sensor according to a thermal principle, wherein a release of heat output of a heated by the flow of electric current sensor wire compared to a thermally insulated sensor wire is evaluated via a resistance bridge circuit as a measure of a respective flow rate.

An alternative approach, which clearly saves electrical energy compared to the electro-thermal measurement, has been described in general in the article "Flow Measurement Technique - An Overview", in the journal "Technisches Messen tm", 1979, No. 4, pages 145-149 , For this purpose it is known to build up a flow measurement on the basis of the so-called drift principle using a transmitting and a receiving ultrasonic measuring head. The two ultrasound measuring heads serve as a transmitter and a receiver and require a corresponding transceiver before signal evaluation. Furthermore, from the Automotive Handbook / Bosch, 23rd, updated and expanded edition, Verlag Vieweg, 1999, ISBN 3-528-03876-4, page 115, a method for ultrasonic flow measurement is known, after a running time of a sound pulse through Measure a measuring medium, such as air, under the helix angle α with the same measuring section 1 once against an air flow and once in the air flow direction. A resulting transit time difference of the sonic pulse is directly proportional to the volume flow.

In order to influence the air flow as little as possible and to minimize the space compared to other known arrangements, the ultrasonic transducers are arranged in known arrangements coaxially and obliquely opposite, such. B. in DE 33 31 519 C2 discloses. However, this leads to a reduction in the measuring effect with increasing angle of attack of the transducer to the horizontal. This results in a compromise of an installation length dependent on the angle of the transducers to the horizontal and the measuring effect of the arrangement. The diagonally opposite arrangement of the transducers offers the advantage of averaging the drift over a flow velocity distribution of the entire tube cross section.

According to the prior art, the flow measurement is realized by means of ultrasonic transducers by two coaxially oriented transducers are arranged obliquely opposite to the tube walls. Since one transducer is mounted on one side and the other transducer is mounted on the opposite side of the tube, cables of varying lengths are required from the electronics to the transducers. The cable lengths occurring between the control electronics and the respective ultrasonic transducers leads to additional runtime differences of the received signals. In addition, there is the risk of electrical or electromagnetic interference in these cables, which additionally falsify the measurement result. Based purely on a signal drift, which occurs due to the drifting of the sound through the fluid flow, a method and a device for measuring the flow velocity by means of ultrasound have been disclosed, for example, in DE 103 44 895 A1. Here, sound pulses are transmitted from an ultrasonic transmitter to an ultrasonic receiver, which are formed together as a transducer array and arranged in parallel aligned in a pipe wall. The sound waves pass through the entire pipe cross-section twice when reflected on the opposite pipe wall. The sound lobe emitted by a transmitter part of the transducer array is also bundled in such a way that it is focused substantially at one point on the receiver region of the array. Dependent on a respective typical average flow velocity from about 0.5 m / s to about 50 m / s occur at different levels of drift, which are detected by a division of the receiver area into individual small receiving cells of the array.

It is the object of the present invention to provide a low-cost and reliably operating device for flow measurement, also in the range of high and very high volume flows.

This object is solved by the features of the independent claim. Advantageous developments are the subject of the dependent claims.

A basis of the present invention is the recognition that known solutions and in particular ultrasonic air mass meter are suitable with at least one reflector only for use with specific pipe diameters. This is related to the limited installation depth of the device, which is given by the distance of the reflector from the housing. For pipe diameters that exceed the installation depth of the ultrasonic air mass meter with reflector by about twice and more, the air mass meter is only more exposed to low flow velocities. This can negatively influence the measurement result. When using HF ultrasound with frequencies> 250 kHz, it should be noted in addition that a respective signal run length or a transmission path of such sound waves is severely limited, inter alia, by signal attenuation, too great a drift in the case of large air masses and too large a fanning out of the signal.

However, an air mass measurement which is as accurate as possible and reliable in all operating states of an internal combustion engine is also suitable for high volume flows at pipe cross sections of more than about 40 mm up to about 120 mm for air mass flows at flow rates of 0.5-50 m / s at room temperature. Such pipe sections are u. a. used in fresh air supply for commercial vehicles, such. As line trucks or heavy trucks. In order to achieve the above object, at least two ultrasonic transducers with an electronics provided close to the ultrasound transducers are arranged in the tube cross section for detecting a representative flow cross section and at least partially enclosed by at least one flow guide vane in an air mass sensor constructed according to the invention. The guide vane is streamlined in such a way that it generates the lowest possible pressure loss in the pipe and influences the flow as little as possible. Next, the invention ensures that at the now comparatively long distances in a device according to the invention, the cable connections from the ultrasonic transducers to the electronics by the additional vane not substantially extended, but be mitigated. For this purpose, the electronics are at least partially integrated into the vane so that the distance from the transducers to the electronics is minimized.

Hereinafter, various embodiments of the invention will be described, wherein the sound transducer preferably for pairwise alternating operation as a transmitter and receiver are formed. In a particularly preferred embodiment of the invention, a system with at least one sound reflector or mirror reflects the ultrasonic wave emitted by the respective transmitting transducer to the second transducer used as receiving transducer. This device known per se with a reflector is supplemented according to the invention by at least one guide vane. The vane, at the end of the previous structure of the air mass meter is fixed with reflector, protrudes a certain depth into the pipe interior. This ensures that the previous structure of the air mass meter with reflector flows is exposed to the maximum occurring in the pipe flow velocity.

In a further embodiment of the invention, at least one honeycomb construction is integrated with the guide vanes to improve the flow conditions. Such a honeycomb construction is preferably aligned normal to the flow direction.

Preferably, the ultrasonic air mass meter consists of two parallel opposed vanes, between which two ultrasonic transducers are arranged. The ultrasonic transducers are mounted obliquely opposite with braces between the two vanes. The electronics are integrated in the vanes. As a result, the distance to the electrical connections of the ultrasonic transducer is kept as low as possible. In a further development, in addition to improving the flow conditions, honeycomb structures are integrated on the guide vanes, again preferably aligned normal to the flow direction.

However, in one embodiment of the invention, the construction of an ultrasonic air mass meter with reflector is mounted between two vanes. The electronics are preferably in turn integrated in one of the guide vanes in order to minimize the distance to the electrical connections of the ultrasonic transducers. Furthermore, the Improving the flow conditions at least one honeycomb construction to be integrated with the vanes, normal to the flow direction.

In a further embodiment of the invention, two guide blades protrude obliquely to the cross-sectional area and aligned parallel to one another in the fresh air tube. The two ultrasonic transducers are arranged between the two guide vanes. The electronics are integrated in the vanes to minimize the distance to the electrical connections of the ultrasonic transducers. In addition, honeycomb structures on the guide vanes, normal to the flow direction, can be integrated to improve the flow conditions.

With a continuous pairwise change of transmission and reception tasks of the two converters, comparisons of the transit times in the two signal directions in an electronic system are evaluated in adjustable short time intervals. Thus, sound waves in the flow direction and sound waves in the opposite direction are exchanged between the transducers at one time. Due to the special transducer arrangement, the effect of directed parallel to the pipe center axis drift is almost completely hidden. Essentially, only the transit time differences of the measurement signals of the transducers are evaluated for both transmission directions of the sound. In particular, as a result of this arrangement, each lateral emigration of a main lobe of the received signal from the region of the receiver transducer is largely excluded, independently of a flow velocity.

Preferably find as ultrasonic transducer compact piezoelectric transducer application. Thus, an overall very compact design of a device according to the invention is possible. The two transducers are put together in a push-in finger, which has a certain depth into the tube protrudes, fixed parallel to each other, arranged at a predetermined angle obliquely to the tube wall. Due to the arrangement in a plug-in finger, the system can be installed in any tube with a diameter that is greater than the insertion depth of the finger. Due to its design, the system requires very little installation length in the pipe. By shielding the sound path from the mirror system to the receiving transducer, the drift of the ultrasonic wave is decisively reduced by the medium compared to the conventional solution, so that both converters can also be arranged very close together. For this purpose, both transducers in the longitudinal and transverse direction of the intake pipe can be arranged closely juxtaposed or slightly offset from one another. In any case, a compact design of the Einsteckfingers can be achieved as an overall arrangement.

A system with at least one reflector deflects the ultrasonic wave emitted by the transmitting transducer to the receiving transducer and, in a preferred embodiment of the invention, is mechanically connected to the tube of the inserting finger. Thus, according to one embodiment of the invention results in a one-piece construction of all components. The entire arrangement can thus be very easily introduced into the tube and connected electrically to the outside of a signal processing.

The measurement signals of the transducers are evaluated for both transmission directions of the sound still within the tube, wherein an electronic unit for evaluation in the region of the transducers and at least partially protected by a flow guide vane is arranged. As a result, signal propagation paths are shortened and a risk of interference from interfering signals is reduced. In addition, a very compact unit is created, which emits a correspondingly in view of the harsh environment of an internal combustion engine or an entire vehicle according to electro-magnetically protected and / or amplified end signal. Further features and advantages of the invention are given below with description of embodiments with reference to the figures of the drawing. In the drawing show in a schematic representation:

Figure Ia: a section in the axial direction through an intake pipe with two mutually inclined arranged in a plane and connected to each other via a system of reflectors via a Schallausbreitungsweg ultrasonic transducers;

Figure Ib: a cross section through the arrangement of Figure Ia;

FIG. 1c shows a longitudinal section to the plan view of the arrangement according to FIG.

FIGS. 2a-2c:

Representations of an alternative design analogous to the representations according to the figures Ia - Ic with a honeycomb structure surrounding the sound propagation path to improve a flow quality;

Figures 3a - 3c: a section in the axial direction through an intake pipe with two mutually arranged at an angle of inclination between two vanes ultrasonic transducers, which are interconnected via a Schallausbreitungsweg, with a cross section and another longitudinal section of this embodiment;

Figures 4a - 4c: a modification of the embodiment analogous to the representations of the figure sequence 3a - 3c using honeycomb structures to improve the flow between the guide vanes; Figures 5a - 5c: a modification of the embodiment according to Figure Ia in a longitudinal section with arrangement between two vanes with two further views to the embodiment of Figure 5a;

FIGS. 6a-6c show a modification of the embodiment analogous to the illustrations of the sequence of FIGS. 5a-5c using honeycomb structures between the flow-improving guide vanes in the region of the ultrasonic transducers;

FIGS. 7a-7c show a further exemplary embodiment as a modification of a device according to FIG. 3a with the ultrasound transducers arranged between two guide vanes arranged at an angle with respect to a tube cross-sectional area

FIGS. 8a-8c show a modification of the embodiment analogous to the illustrations of the sequence of FIGS. 7a-7c using honeycomb structures between the flow-improving guide vanes in the area of the ultrasonic transducers.

Throughout the various figures, the same reference numerals and designations are used below for identical functional groups or assemblies.

The figure of Figure Ia shows a simplified longitudinal section through a device 1 with an intake pipe 2, in which two ultrasonic transducers 3, 4 are provided. The two ultrasonic transducers 3, 4 are arranged in the region of a central axis M of the intake pipe 2 and near an electronics 5 in the pipe cross-section such that they represent a representative Flow cross-section detect with maximum possible values of a velocity v (y, z) of the directed substantially in the x direction along the central axis M of the intake pipe 2 flow. For this purpose, the ultrasound transducers 3, 4 with respect to their dotted line drawn transmission / reception axes to each other at an angle α obliquely to a tube center axis M arranged so that the ultrasound waves emitted by a to a subsequent period as the transmitter ultrasonic transducers 3, 4 emitted are deflected by a reflector 7 fixed on here only indicated holders in an ultrasonic transducer 3, 4 each acting as a receiver. The running distance of the sound is predominantly in direct contact with the flow.

The ultrasonic transducers 3, 4 are connected to the electronics 5 for driving and signal evaluation. By this electronics, the ultrasonic transducers 3, 4 are operated alternately as a transmitter and receiver. It always forms a pair of a transmitter and a receiver with each reversed course of the sound signal, as indicated in Figure Ia. The results of an evaluation carried out in the electronics 5 on the basis of the output signals of the ultrasonic transducers 3, 4 are forwarded via a connector interface (not shown) to a subsequent engine management system.

The flow through a pipe, in particular at high flow velocities and / or high volume flows over a pipe cross-section, has no constant value. This is indicated above by the statement v (y, z) with the dependencies on the mutually orthogonal coordinates y, z. Representative values are nevertheless found in an area around the central axis M.

In applications with very high flow rates and correspondingly large pipe diameters of about 40 to about 120 mm, known devices for volume flow determination proved inadequate. Nevertheless, such measurement results for a reduction of pollutant emissions and an improvement in the efficiency of corresponding internal combustion engines are urgently needed. Under the primary interest in the most reliable possible signal measurement, in all embodiments presented here, a pressure loss and increased flow resistance caused by a measuring device are considered to be secondary. In this sense, internals are subsequently introduced into the pipe cross-section. To reduce the fluidically negative influences and to protect the components of the air mass sensor 1 in the tube 2 by a Strömungsleitschaufel 8 is at least partially enclosed. According to FIGS. 1 a and 1 c, in the present embodiment of the invention, an electronic unit 5 arranged close to the ultrasonic transducers 3, 4 is enclosed by two flow guide vanes 8 for forming a protective and flow-favorable profile. The Strömungsleitschaufeln 8, at the end of the actual air mass meter is fixed with reflector 7, projects a certain depth T in the interior of the tube 2. This ensures that the air mass meter is exposed with reflector 7 flows with the maximum occurring in the pipe 2 flow rate. The guide vane 8 is streamlined in such a way that it generates the lowest possible pressure loss in the pipe 2 and influences the flow as little as possible.

Furthermore, the illustrated construction ensures that the cable connections from the ultrasonic transducers 3, 4 to the electronics 5 are not extended by the additional guide blade 8. For this purpose, the electronics are integrated between the flow guide vanes 8 in a closed area, so that the distance from the transducers 3, 4 to the electronics 5 is kept as low as possible. This reduces the sensitivity to electromagnetic radiation. Furthermore, the low cable length reduces the influence of the electrical signal attenuation through the cables. Since the vane is directly connected to the air Ström is exposed, the electronics located therein is automatically cooled. By integrating the electronics into the vane, only the plug is present on the surface of the pipe. This drastically reduces the installation space of the ultrasonic air mass meter with reflector in height.

Thus, the two ultrasonic transducers 3, 4 are close to the electronics 5 with very short signal paths of the wiring and measure flow velocities in a central tube region for the detection of a representative cross section. Since at high flow velocities and frequencies> 250 kHz occur due to signal attenuation, excessive signal drift and fanning of the signal significant limitations in a free run length, the run length of the ultrasonic signal is limited by the installation of the device in the pipe cross-section through the arrangement shown. FIG. 1 b shows a cross section through the arrangement according to FIG. 1 a for clarification of the slim measuring structure projecting into the tube 2 over a length T. Pressure loss and increased flow resistance are reduced by the Strömungsleitschaufeln 8, as indicated by the figure of Figure Ic with a longitudinal section to the top view of the arrangement of Figure Ia with sketched flow lines.

FIGS. 2a-2c show illustrations of an alternative design analogous to the representations according to FIGS. 1a-1c with a honeycomb structure 9 surrounding the sound propagation path. The honeycomb structures are aligned normal to the flow direction or parallel to the central axis M. The honeycomb structure 9 serves to reduce the flow velocity at the ultrasonic transducers and thus causes an improvement in the flow quality, so that homogenization of the flow and thus an increase in the reliability of the measurements is achieved with known damping and lowering of a flow velocity. The honeycomb structure 9 can therefore be used as a defined reduction or Throttle can be used so that a true flow velocity v is calculated by a corresponding, stored in the electronics 5 calibration curve.

A further modification of the embodiment according to FIGS. 1a-1c is shown in FIGS. 3a-3c as a section in the axial direction through an intake pipe with two ultrasonic transducers arranged opposite one another at an angle of inclination, which are connected to one another via a sound propagation path. These are fixed by means of indicated braces between two guide vanes 10, 11, as becomes clear from the cross section of FIG. 3b and a further longitudinal section of this embodiment according to FIG. 3c. The electronics 5 are in turn integrated close to the ultrasound transducers 3, 4, here by being arranged in the guide vane 10 in order to minimize the distance to the electrical connections of the ultrasound transducers 3, 4. Compared with the variants described above, the opposite arrangement of the ultrasonic transducers 3, 4 between two guide vanes 10, 11 leads to increase the integration path over the cross section of the tube 2. The two opposing vanes 10, 11 lead to a narrowing of the flow cross-section. This leads to a calming of the flow at the ultrasonic transducers 3, 4.

The sequence of FIGS. 4a-4c shows a modification of the embodiment analogous to the illustrations of the sequence of FIGS. 3a-3c using honeycomb structures 9 for improving the flow between the guide vanes 10, 11, as stated above. Here, the honeycomb structure 9 does not extend over the entire cross-sectional length of the arrangement, as illustrated in the figure of Figure 4c.

FIGS. 5a-5c show a modification of the embodiment according to FIG. 1a in a longitudinal section with two further views to the embodiment according to FIG. 5a in the illustrations of FIGS. 5b and 5c. Here is the reflector 7 of the Arrangement of Figures Ia - Ic now mounted between two vanes 10, 11. The associated electronics 5 is integrated in the guide vanes, again to keep the distance to the electrical connections of the ultrasonic transducers 3, 4 as small as possible in a compact design of the arrangement and maximum protection against negative environmental influences.

A modification of the embodiment analogous to the illustrations of the sequence of figures 5a-5c using honeycomb structures 9 between the guide vanes 10, 11 for improving the flow in the area of the ultrasonic transducers is shown in FIGS. 6a-6c. Here, the honeycomb structure 9 used for improving the flow is not extended over the entire cross-sectional length of the arrangement in the manner already indicated in the illustration of FIG. 4c, see FIG. 6c.

FIGS. 7a-7c show a further exemplary embodiment as a modification of a device according to FIG. 3a with arrangement of the ultrasound transducers 3, 4 between two guide vanes 10, 11 which are inclined at an angle β with respect to a tube cross-sectional area. Two guide vanes 10, 11 thus project obliquely and parallelly each other in the tube 2 inside. This variant has similar properties as the u. a. with reference to the figures of the figures described variant. However, due to the inclined design of the vanes, the angle and depth of the ultrasonic transducers can more easily be varied. Furthermore, the design of the ultrasonic air mass meter as Einsteckfinger is facilitated by the shorter installation length. The two ultrasonic transducers 3, 4 are arranged at a fixed distance from one another facing each other between the two guide vanes 10, 11. Thus, the reflector can be omitted here again.

Finally, FIGS. 8a-8c illustrate a modification of the embodiment analogous to the representations of the sequence of FIGS. 7a-7c using honeycomb structures 9 between the FIGS Guide vanes 10, 11 for improving the flow in the ultrasonic transducer.

As a result, the arrangements described above are very compact. They can be made completely as a Einsteckfinger and arranged to be sealed over a relatively small opening in a suction pipe 2 quickly.

Claims

claims

1. air mass sensor with two ultrasonic transducers (3, 4), which are arranged in a tube (2), since you rchgekennzeichnet that at least two ultrasonic transducers (3, 4) with a near the ultrasonic transducer (3, 4) provided electronics (5) are arranged in the tube cross section for detecting a representative flow cross section and the air mass sensor in the tube (2) is at least partially enclosed by at least one flow guide vane (8).

2. Air mass sensor according to claim 1, since you rchgekennzeichnet that a reflector (7) or a system with at least one mirror or reflector (7, 8) is arranged so that from the respective transmitting transducer (3, 4) emitted ultrasonic wave ( 9) is reflected to the used as a receiving transducer second transducer (3, 4).

3. Air mass sensor according to one of the preceding claims, in that at least part of a transmission path of the ultrasonic wave (6) between the ultrasonic transducers (3, 4) with a honeycomb structure (9) is surrounding.

4. The air mass sensor according to the preceding claim, characterized in that the honeycomb structure (9) is aligned normal to the flow direction.

5. Air mass sensor according to one of the preceding claims, since you rchgekennzeichnet that the transmission path in a region of the tube center axis (M) is arranged.

6. Air mass sensor according to one of the preceding claims, in that both transducers (3, 4) arranged opposite each other at an inclination angle (α), fixed between two guide vanes 10, 11 and connected to each other via a sound propagation path.

7. The air mass sensor according to one of the preceding claims, wherein the ultrasonic transducers (3, 4) between two at an angle (ß) relative to a cross-sectional area of the tube

(2) inclined arranged vanes (10, 11) are fixed.

8. Air mass sensor according to one of the preceding claims, since you rchgekennzeichnet that the transducers (3, 4) are designed as compact piezoelectric ultrasonic transducers, the electronics together a (5) are arranged in a Einsteckfinger, which in a mounting position a certain depth (T) into the intake pipe (2) protrudes.

9. Air mass sensor according to one of the preceding claims, since you rchgekennzeichnet that the E- lektronik (5) is designed to output a signal over a current amount of air, the electronics in a foot sealingly enclosed by a vane (8, 10, 11) is.