DE102021214889A1 - Device for detecting at least one parameter of a fluid medium flowing through a channel - Google Patents

Abstract

A device (110) for detecting at least one parameter of a fluid medium flowing through a duct (112), in particular an intake air mass of an internal combustion engine or a fuel cell system, is proposed. The device (110) comprises: • at least one flow tube (114); and• at least one plug-in sensor (122) which is or can be inserted at least partially into the flow tube (114), in which the channel (112) is formed, the plug-in sensor (122) furthermore having at least one sensor chip (128) arranged in the channel (112) for determining the parameter of the fluid medium, wherein the plug-in sensor (122) has at least one inlet (146) into the channel (112) and one outlet (148) from the channel (112); characterized in that the device (110) further comprises at least one acoustic grid (126), the acoustic grid (126) being arranged at one end (119) of the flow tube (114), in particular at one end (119) of the flow tube (114), oriented towards a source of acoustic interference; and in that the acoustic grid (126) has at least one contour selected from the group consisting of: a surface contour (190) of at least a portion of a surface of the acoustic grid (126); an edge profile (191) of at least one edge (194) of the acoustic grid (126).

Description

State of the art

Numerous methods and devices for determining the flow properties of fluid media, ie liquids and/or gases, are known from the prior art. The flow properties can in principle be any physically and/or chemically measurable properties which qualify or quantify a flow of the fluid medium. In particular, this can be a flow rate and/or a mass flow and/or a volume flow.

In the following, the invention is described in particular with reference to so-called hot-film air-mass meters, as known, for example, from Konrad Reif (ed.), Sensors in Motor Vehicles, 1st edition 2010, pages 146-148. Such hot-film air mass meters are generally based on a sensor chip, in particular a silicon sensor chip, with a measuring surface over which the flowing fluid medium can flow. As a rule, the sensor chip comprises at least one heating element and at least two temperature sensors, which are arranged, for example, on the measuring surface of the sensor chip. A mass flow and/or volume flow of the fluid medium can be inferred from an asymmetry of the temperature profile detected by the temperature sensors, which is influenced by the flow of the fluid medium. Hot-film air-mass meters are usually designed as a plug-in sensor, which can be introduced into a flow tube in a fixed or interchangeable manner. For example, this flow tube can be an intake tract of an internal combustion engine or a fuel cell drive.

In order to be able to draw precise conclusions about certain flow properties of the fluid medium from the sensor signals of the hot-film air-mass meter, in many cases it is desirable to be able to provide further information about the fluid medium. Sensor devices for detecting a flow property of a fluid medium are also known, which have an air mass meter with a sensor element for detecting an air mass flow and a moisture sensor for detecting moisture in the fluid medium. In addition, the locally prevailing flow pressure of the fluid medium can be measured by a pressure sensor in order to optimize the operation of the internal combustion engine.

Despite the advantages brought about by these sensor devices, they still contain potential for improvement. In particular, acoustic disturbances can be present in the volume surrounding the stretch sensor.

Disclosure of Invention

A device for detecting at least one parameter of a fluid medium flowing through a channel and a method for producing a device for detecting at least one parameter of a fluid medium flowing through a channel are therefore proposed, which at least largely avoid the disadvantages of known devices and methods described above . In particular, acoustic disturbances in the volume surrounding the plug-in sensor should be avoided or reduced as much as possible. In particular, an acoustic sound pressure, an acoustic sound intensity and/or an acoustic speed fluctuation, so-called sound velocity, are to be reduced in order to reduce deviations from the characteristic curve.

In a first aspect of the present invention, a device for detecting at least one parameter of a fluid medium flowing through a duct, in particular an intake air mass of an internal combustion engine or a fuel cell system, is proposed.

The device includes at least one flow tube. The flow tube has at least a first end and at least a second end. Furthermore, the device comprises at least one plug-in sensor which is or can be introduced at least partially into the flow tube and in which the channel is formed. The plug-in sensor also has at least one sensor chip arranged in the channel for determining the parameter of the fluid medium. The plug-in probe has at least one inlet into the channel and one outlet from the channel.

Furthermore, the device comprises at least one acoustic grid. The acoustic grille is located at an end of the flow tube that is oriented towards a source of acoustic disturbances. In particular, the end may be between a hot film mass air flow (HFM) plug-in sensor and the source of acoustic interference. In the case of an internal combustion engine in particular, the end can be downstream of the HFM plug-in sensor in the direction of core elements of the internal combustion engine, in particular a turbocharger, or between the HFM plug-in sensor and an air compressor of a fuel cell drive.

The acoustic grating has at least one profiling selected from the group consisting of: a surface profiling of at least part of a surface of the acoustic grating; an edge profiling of at least one edge of the acoustic grid.

With regard to the at least one parameter of the fluid medium flowing through the channel, it can in particular be a flow property which can be qualitatively and/or quantitatively recorded. For example, reference may be made to the description of the prior art above. In particular, this flow property can be a flow rate and/or a mass flow and/or a volume flow of the fluid medium. The fluid medium can in particular be a gas, preferably air. The device can be used in particular in motor vehicle technology, for example in the intake tract of an internal combustion engine or in a fuel cell drive. In principle, however, other areas of use are also possible.

As explained above, the device according to the invention comprises at least one plug-in sensor. The plug-in sensor can be inserted into the flowing fluid medium, whereby an exchangeable or permanent insertion is conceivable. The plug-in sensor can, for example, protrude into the flow tube. The flow tube can have an opening into which the plug-in sensor can be inserted. The plug-in sensor can have a housing. In the context of the present invention, a housing is to be understood as a one-part or multi-part device which at least largely seals off the sensor chip and electronic and other components from the outside and at least largely protects them from mechanical effects and preferably also other types of effects, for example chemical effects and/or effects of moisture. The housing, as a one-part or multi-part device, typically fulfills additional functions, for example enabling electrical contact via a plug area and can in particular take aerodynamic requirements into account. The plug-in sensor, in particular the housing, can in particular be made at least partially from a plastic material, for example by means of an injection molding process. The piece sensor can be connected to a dome area of the flow tube in particular by means of at least one vibration welding method.

At least one electronic module with the at least one sensor chip can be accommodated in the plug-in sensor. The sensor chip can in particular be a flow sensor for detecting the at least one parameter of the medium flowing through the channel. A receptacle in the plug-in sensor means that the electronics module is at least partially, preferably completely, surrounded by the plug-in sensor. The electronics module can be arranged at least partially in at least one electronics space of the plug-in sensor. The electronics space preferably comprises at least one depression in the housing that is accessible from a surface of the housing, for example a cuboid depression. The electronics compartment can be accessible, for example for equipping, and can be permanently or reversibly closed by at least one closure element, for example at least one electronics compartment cover.

In this case, a sensor chip is to be understood in principle as any sensor element which is designed to detect the at least one parameter of the medium flowing through the channel. In particular, the sensor chip can be at least one micromechanical sensor chip for measuring the air mass flow, which contains at least one micromechanical sensor membrane. The silicon chip with the micromechanical sensor membrane can in particular comprise a measurement surface over which the flowing fluid medium can flow. At least one heating element and at least two temperature sensors can be located on this sensor surface, for example, it being possible to deduce the at least one flow property from an asymmetry of the temperature profile measured by the temperature sensors. The at least one sensor chip can be arranged, for example, on a sensor carrier of the electronic module, which protrudes into the flowing fluid medium.

The electronics module can in particular carry a control and/or evaluation circuit which is set up to control the sensor chip and/or to receive signals from the sensor chip, process them and make them available to a commonly used engine control unit. Accordingly, the electronics module can have at least one circuit carrier, for example. Furthermore, the electronics module can in particular have the at least one sensor carrier, which is preferably mechanically connected to the circuit carrier. For example, the circuit carrier can be arranged in the electronics space of the sensor housing, and the sensor carrier can project out of this electronics space into the fluid medium.

As stated above, the channel is formed in the plug-in sensor. The canal can be seen from the flui be permeable to the medium. The sensor carrier of the electronics module, which carries the sensor chip, can protrude from the electronics space into the channel. The duct can be designed in one piece, or also have at least one main duct and at least one bypass duct branching off from this main duct. The sensor carrier can preferably protrude into the bypass channel. The circuit carrier of the electronics module can in particular include a printed circuit board, which is used alone or which is also mounted on a mechanical carrier, for example a base plate in the form of a stamped and bent part that can be made of a metallic material. The sensor carrier can be connected directly to the circuit carrier or also to the carrier part, for example to the floor panel, for example by the sensor carrier being injection-molded onto the floor panel.

A flow tube within the meaning of the present invention is to be understood in principle as any hollow body through which a fluid medium can flow. In particular, it can be an elongate hollow body. The flow tube can be configured at least partially in a rotationally symmetrical manner. The flow tube can therefore also be referred to as a cylinder housing. The flow tube can be produced in particular by means of at least one injection molding process.

The device can further comprise at least one vane grid. The vane grid can be arranged at one end of the flow tube. In particular, the vane grid can be arranged upstream of the plug-in sensor in a main flow direction. The vane grid can have several vanes and webs for deflecting the fluid medium into the main flow direction prevailing at the plug-in sensor. The vanes can be arranged, at least in sections, in a circular, elliptical or variable radius manner. The vanes can be set up to reduce flow fluctuations and to generate homogeneous, high, low-turbulence flow velocities on the plug-in sensor. The flow tube and the vane grid can be made in one piece. In particular, the flow tube and the wing grating can be produced by means of an injection molding process. The vane grid can therefore also be referred to as a flow conditioning element. Furthermore, the vane grid can contribute to reducing acoustic interference of a certain frequency and wavelength, in particular such acoustic interference with wavelengths smaller than the diameter or the characteristic length of the flow tube in the area of the HFM plug-in sensor, so-called cut-off modes. Some of the design elements of the acoustic grille described below can also be applied to the wing grille.

As stated above, the device further comprises the at least one acoustic grating. In particular, the acoustic grid can be arranged downstream of the plug-in sensor in a main flow direction. The acoustic grid can be set up to avoid or reduce acoustic disturbances in the volume surrounding the plug-in sensor and thereby in particular deviations from a target air mass flow characteristic curve despite adverse acoustic excitation, in particular by a single- or multi-stage turbocharger of an internal combustion engine or, for example, an air compressor of a fuel cell drive . An overall volume can be subdivided into correspondingly smaller sub-volumes by the ring-shaped elements and by the web elements and can ensure that radiation is irregular in terms of wavelengths and sound intensities upstream of the plug-in sensor.

The acoustic grating can be produced in particular by means of at least one injection molding process. Furthermore, the acoustic grid can be connected to the flow tube by means of at least one ultrasonic welding method. The acoustic grating cannot be injected together with the flow tube and the wing grating, particularly for tool-related reasons. It can therefore be manufactured in a separate injection molding process. The separate acoustic grid can be pushed into the flow tube downstream of the plug-in sensor and permanently connected to the flow tube, for example using ultrasonic welding processes. Other connection methods such as caulking are conceivable. The acoustic grid can be produced together with the flow tube in a single injection molding process, in particular if the wing grid is produced in a separate injection molding process and is subsequently connected to the unit made up of flow tube and acoustic grid.

As stated above, the acoustic grille has at least one profile selected from the group consisting of: the surface profile of at least part of a surface of the acoustic grille; the edge profiling of the at least one edge of the acoustic grille.

“Surface profiling” can basically be understood to mean an aerodynamically customary profiling in the sense of a camber, thickness and curvature distribution and/or any additional or superimposed shaping of a surface by means of at least one pattern and/or by means of at least one structure. The latter possible additional In particular, structures take into account the task of reflecting incoming sound waves in different directions and thus reducing acoustic disturbances in the area of the openings of the bypass channel system in the case of acoustic superimposition of sound pressures and sound velocities of as many wave packets as possible. The pattern can be regular or irregular. Consequently, in a cross-sectional view, the surface can have correspondingly designed elevations and depressions. The surface profiling can therefore also be referred to as surface structuring or as a surface structure. The surface profiling can in particular be selected from the group consisting of: a continuous surface profiling; a parquetted surface profiling; a surface profiling by means of linear and/or abrupt level differences, especially in the case of mold parting lines; a surface profiling that also meets aerodynamic requirements in the form of a curvature and thickness distribution. Other exemplary embodiments are also conceivable in principle. In order to increase the probability of a desired reduction in sound pressures with wavelengths, phase angles and/or amplitudes that vary depending on the application, these structures can be implemented on a relatively small scale, for example on the order of 1 mm to 50 mm, in particular from 2 mm to 10 mm, with corresponding transition structures definitely smaller than 1 mm, in order to increase the aerodynamic quality in particular. Other dimensions are also conceivable in principle.
The edge profiling of the at least one edge of the acoustic grating can be selected from the group consisting of: a sinusoidal profiling, in particular a sinusoidal profiling, which is designed differently at different edges with regard to wavelength and/or amplitude; a profiling with battlements or recesses as segments, in particular with a right-angled or non-right-angled connection of the segments; a profiling with a polynomial-like curve. In principle, other configurations are also conceivable.

The acoustic grille may have at least one outer annular element and at least one inner annular element. The inner annular member and the outer annular member may be concentric with or offset from an axis of rotation of the flow tube. The outer annular member and the inner annular member may be interconnected by a plurality of web members, the web members preferably being disposed radially about the axis of rotation of the flow tube. As a further basic embodiment, web elements can lead from lateral surface boundaries of the flow pipe, for example along imaginary Cartesian main directions, to opposite pipe boundaries, that is to say without using ring-shaped elements.

The terms "inner ring-shaped element" and "outer ring-shaped element" are to be regarded as pure descriptions, without specifying a ranking and, for example, without excluding the possibility that several types of inner ring-shaped elements or outer ring-shaped elements or exactly one type each can be provided. Furthermore, additional inner and/or outer ring-shaped elements can be present, as will be explained in more detail below. The term “ring-shaped element” refers in particular to any element which at least partially has the shape of a ring. In particular, the inner ring-shaped element and/or the outer ring-shaped element can at least partially have the shape of a cylinder, in particular a circular cylinder. Furthermore, these elements can also be approximately ring-shaped. In cross section, these elements can therefore be designed, for example, as polygons, which can have at least approximately ring-shaped or even straight or approximately straight connecting elements, in particular between corners.

As stated above, the inner annular member and the outer annular member may be concentric about the axis of rotation of the flow tube. In the context of the present invention, the term “concentric” means that the inner ring-shaped element and the outer ring-shaped element are arranged symmetrically around a common center point. The inner annular member may have a radius that differs from a radius of the outer annular member. In particular, the radius of the inner annular element can be smaller than the radius of the outer annular element. A distance between the inner ring-shaped element and the outer ring-shaped element can be in particular 1 mm to 100 mm, preferably 5 mm to 75 mm and particularly preferably 10 mm to 50 mm. Other dimensions are also conceivable in principle. A distance between the inner ring-shaped element and the outer ring-shaped element can in principle be selected in the order of one or more centimeters up to the order of one or more decimeters. This can depend on acoustic disturbances and their wavelengths. The wavelengths can differ, for example, in applications in the classic combustion engine and applications in fuel cell drives or other applications, which ent speaking design adjustments of the acoustic grille can result.

Depending on the design and air mass flow requirements of the application, for example the internal combustion engine or the fuel cell drive, the diameter of the flow tube or a section of the flow tube typically varies from, for example, 30 mm to 150 mm in non-cylindrical variants. Depending on the acoustic signature of the disturbances and due to the above design of the flow tube, the number of ring-shaped elements and their spacing from one another and from the jacket of the flow tube can therefore also vary. The distance between the ring elements of the acoustic grid can vary for reasons of flow-mechanical resistance generation and because of the relevant acoustic wavelengths. The spatial extent of a ring element in the main direction of flow can also vary for the above reasons between, for example, 10 mm and 50 mm. The ring elements can, for example, have a material thickness of between 0.4 mm and 5 mm, for example in an aerodynamically favorable profile. These points also apply to the bar elements described.

As explained above, the web elements can be arranged, for example, radially around the axis of rotation of the flow tube. In the context of the present invention, the term “radial” means that the web elements extend at least partially, in particular in a straight line, along the radius of the outer ring-shaped element. In particular, the web elements can be spaced evenly apart from one another. In particular, two adjacent bar elements can be arranged at an angle to one another which corresponds to a quotient of 360° to a number of bar elements. Furthermore, the web elements can be unevenly spaced from one another. An acoustic energy and/or a phase position can be structured and/or irregularized by a non-uniform spacing from one another. Possibly only an uneven spacing can be realized in terms of production technology.

At least one element selected from the group consisting of: the inner ring-shaped element, the outer ring-shaped element, at least one of the web elements can have the surface profile and/or the edge profile of the at least one edge.

Furthermore, the acoustic grille can have at least one first inner ring-shaped element and at least one second inner ring-shaped element. The first inner annular member and the second inner annular member may be concentric or non-concentric about the axis of rotation of the flow tube. A radius of the first inner annular member may be larger than a radius of the second inner annular member. The first inner annular member and the second inner annular member may be connected to each other by a plurality of other web members. The other bar elements can be arranged radially or in a different orientation around the axis of rotation of the flow tube. The first inner annular member and the outer annular member may be connected to each other by the web members. The bar elements and the further bar elements can be arranged offset to one another. A number of the bar elements can differ from a number of the other bar elements.

At least one element selected from the group consisting of: the first inner ring-shaped element, the second inner ring-shaped element, at least one of the further web elements can have the surface profile and/or the edge profile of the at least one edge

Furthermore, the acoustic grille can have at least one ring-shaped element and the acoustic grille can have at least two straight ribs which extend inside the ring-shaped element.

At least one element selected from the group consisting of: the ring-shaped element, one of the at least two straight ribs, can have the surface profile and/or the edge profile of the at least one edge.

In particular, downstream edges, in particular trailing edges, of the at least one element can have the edge profiling. As a result, an overall length of the corresponding element in the main flow direction can be varied along the circumferential direction in the case of ring elements and along their circumferential direction in the case of bar elements and along their main direction in the case of bar elements, for example in the radial direction.

A further aspect of the present invention proposes a method for producing a device for detecting at least one parameter of a fluid medium flowing through a channel, as has already been described or will be described below.

1. a) Bereitstellen des Strömungsrohrs, wobei das Strömungsrohr das erste Ende und das zweite Ende aufweist;
2. b) Verbinden des Steckfühlers mit einem Dombereich des Strömungsrohrs, insbesondere mittels mindestens einen Vibrationsschweißverfahren; und
3. c) Verbinden des Akustikgitters mit dem Strömungsrohr, insbesondere mittels mindestens einem Ultraschall-Schweißverfahren.

The procedure includes the following steps:

1. a) providing the flow tube, the flow tube having the first end and the second end;
2. b) connecting the plug-in sensor to a dome area of the flow tube, in particular by means of at least one vibration welding process; and
3. c) Connecting the acoustic grid to the flow tube, in particular by means of at least one ultrasonic welding process.

The acoustic grid can be connected to the flow tube using at least one ultrasonic welding process. The acoustic grille can be manufactured using at least one injection molding process.

The flow tube can be manufactured using at least one injection molding process. In particular, the flow tube and the wing grating can be manufactured in one piece. In this way, the flow tube and the vane grid can be produced in step a).

In step b), the piece sensor can be connected to a dome area of the flow tube by means of at least one vibration welding process.

The proposed device has numerous advantages over known devices. Compared to known devices, various aspects of the geometric design of the acoustic grid prevent or reduce acoustic disturbances in the volume surrounding the plug-in sensor and, as a result, in particular deviations from the target characteristic curve despite adverse acoustic excitation, in particular from single-stage or multi-stage turbochargers or compressors of a fuel cell system. Other advantages due to the introduction of the acoustic grid in the flow tube include improved flow conditioning and directivity, also with regard to aerodynamic fluctuations with length scales in the order of the air filter, flow tube and plug-in sensor dimensions, as well as improved signal noise of the associated low-frequency interference and improved adjustability in of serial production.

character list

Further optional details and features of the invention result from the following description of preferred exemplary embodiments, which are shown schematically in the figures.

• 1A bis 1C eine Ausführungsform der erfindungsgemäßen Vorrichtung zur Erfassung mindestens eines Parameters eines durch einen Kanal strömenden fluiden Mediums (1A) sowie Detailansichten des Steckfühlers (1B und 1C);
• 2A bis 2C einen Steckfühler (2A), einen Bypasskanaldeckel mit positioniertem Sensorträger (2B) und ein Strömungssimulationsergebnis der Strömung im Bereich des Bypasskanals und in direkter Umgebung des Steckfühlers (2C);
• 3 eine Detailansicht einer weiteren Ausführungsform eines Bypasskanaldeckels mit dem strömungsführenden Bypasskanal;
• 4A bis 4E eine vom Turbolader eines Verbrennungsmotors oder Verdichters eines Brennstoffzellensystems zum Steckfühler laufende akustische Welle samt reflektierter Welle und akustischer Überlagerung (4A); Hitzdraht-Signale für die Aufzeichnung von Geschwindigkeiten und Schallschnellen an verschiedenen Messstellen (4B: Messstelle im Strömungsrohr aber außerhalb des Steckfühlers; und 4C: Messstelle im Bypasskanal im Bereich der Position des Sensorträgers); Detailansichten eines Hauptstrom- und Bypasskanalsystems (4D und 4E);
• 5A bis 5D ein Messprinzip einer erfindungsgemäßen Vorrichtung (5A), eine Geschwindigkeitsverteilung der Hintergrundströmung (5B), eine Geschwindigkeitsverteilung einer pulsierenden Strömung ohne Hintergrundströmung (5C) und eine Überlagerung eines pulsierenden Massentromes auf der Sensorkennlinie (5D);
• 6A bis 6C ein exemplarisches Ausführungsbeispiel eines Akustikgitters;
• 7A und 7B weitere exemplarische Ausführungsbeispiele eines Akustikgitters; und
• 8 ein weiteres exemplarisches Ausführungsbeispiel eines Akustikgitters.

Show it:

• 1A until 1C an embodiment of the device according to the invention for detecting at least one parameter of a fluid medium flowing through a channel ( 1A) as well as detailed views of the plug-in sensor ( 1B and 1C );
• 2A until 2C a plug-in sensor ( 2A) , a bypass channel cover with positioned sensor carrier ( 2 B) and a flow simulation result of the flow in the area of the bypass channel and in the immediate vicinity of the plug-in sensor ( 2C );
• 3 a detailed view of a further embodiment of a bypass channel cover with the flow-guiding bypass channel;
• 4A until 4E an acoustic wave running from the turbocharger of an internal combustion engine or the compressor of a fuel cell system to the plug-in sensor, including the reflected wave and acoustic superimposition ( 4A) ; Hot wire signals for recording velocities and sound velocities at various measuring points ( 4B : Measuring point in the flow pipe but outside the plug-in sensor; and 4C : measuring point in the bypass channel in the area of the position of the sensor carrier); Detailed views of a main flow and bypass duct system ( 4D and 4E) ;
• 5A until 5D a measuring principle of a device according to the invention ( 5A) , a velocity distribution of the background flow ( 5B) , a velocity distribution of a pulsating flow without background flow ( 5C ) and a superposition of a pulsating mass flow on the sensor characteristic ( 5D );
• 6A until 6C an exemplary embodiment of an acoustic grating;
• 7A and 7B further exemplary embodiments of an acoustic grid; and
• 8th another exemplary embodiment of an acoustic grille.

Embodiments of the invention

1A shows an embodiment of the device 110 according to the invention for detecting at least one parameter of a through a channel 112 (see 1C ) flowing fluid medium.

The device 110 comprises at least one flow tube 114. The flow tube 114 can also be referred to as the cylinder housing 116. The flow tube 114 may have at least a first end 118 and at least a second end 120 . Furthermore, the device 110 comprises at least one at least partially in the Strö 114 introduced or insertable plug-in sensor 122, in which the channel 112 (see 1C ) is trained.

Furthermore, the device 110 can include at least one wing grating 124 . The airfoil 124 may be disposed at the first end 118 of the flow tube 114 . Furthermore, the device 114 comprises at least one acoustic grid 126. The acoustic grid 126 can be arranged at one end 119, in particular at the second end 120, of the flow tube 114.

1B and 1C show detailed views of the plug-in sensor 122.

The plug-in sensor 122 also has at least one sensor chip 128 arranged in the channel 112 for determining the parameter of the fluid medium. The sensor chip 128 can be glued into a sensor carrier 130 . The sensor carrier 130 can form a unit together with a metal base plate 132 . In addition to the sensor chip 128, the electronics on their circuit board 134 can also be glued onto the base plate 132. The sensor chip 128 and the electronics can be connected to one another by bond connections. The electronics module that is created in this way can be glued into the plug-in sensor housing 136 and the entire plug-in sensor 122 can be closed with a bypass channel cover 138 and an electronics compartment cover 140 . After assembly, the bypass channel cover 138 and the opposite wall of the plug-in sensor 122 thus produce the flow volume of the channel 112 with the main flow channel 152 and the bypass channel 150. In addition, the plug-in sensor 122 can have at least one temperature sensor 142 and/or at least one humidity sensor 144 and/or at least include a pressure sensor (not shown graphically).

As in 1C As shown, the probe 122 has at least one inlet 146 into the channel 112 and at least one outlet 148 from the channel 112 . For an explanation of the fluid mechanical and metrological basic function is on the 1C referred. The flow paths of air contaminated with water (arrow with dots) and particles (arrow with dashes) and cleaned of the large particles and water droplets (arrow with solid line) are also shown.

In normal operation, air passes from the inlet 146 via the centrifugal deflector 155 (see 2 B) to the sensor carrier 130. Due to the centrifugal deflection 155, only the lighter particles (e.g. very small water and oil droplets as well as dust and soot particles) reach the bypass channel 150. Heavy particles leave the plug-in sensor 122 with the majority of the mass flow through the main flow channel 152 due to their mass inertia and the main flow channel outlet 158 or impact against the surrounding walls and are either thrown back into the flow volume and entrained by the flow close to the wall or finally creep largely out of the channel system 112 via the outlets 148 due to the wall shear forces.

At least one micromechanical sensor membrane can be applied to the sensor chip 128 (not shown). Since a heat transfer in the area of the sensor membrane is decisive both from the boundary layer flow on a sensor chip side of a sensor carrier 130 and to a certain extent from a flow further away from the wall, in particular in terms of a fluid-mechanical definition of a boundary layer, both on the sensor chip side and on the side facing away from the sensor chip 128 and moreover can be determined by a wake flow of the sensor carrier 130, these flow areas should be topologically or qualitatively and quantitatively as stable as possible. A changed topology is understood to mean a change in the structure defining the flow with marked points such as stagnation points, vortex foci, separation lines, etc. A quantitative change in the flow variables, in particular the fluctuation of speed and pressure, even without changing the topology, should also be avoided or be reduced. When passing sensor carrier 130, the mass flow through bypass channel 150 is therefore divided between the side facing sensor chip 128 and the side facing away from sensor chip 128, and a gap between an end face of sensor carrier 130 and a wall of bypass channel 150. Acoustic disturbances, i.e. high-frequency pressure and speed fluctuations, can lead to a change in the boundary layer flow over the micromechanical sensor membrane and thus to signal and characteristic curve deviations if the sound intensity is sufficiently high. Such acoustic disturbances can be generated by turbochargers used in modern internal combustion engines or by compressors in fuel cell systems, which are mostly electrically driven. The design elements described in this application serve to reduce the sound propagation and the sound intensity in order to reduce deviations in the characteristic curve.

2A shows an exemplary embodiment of a plug-in sensor 122, 2 B shows a bypass channel cover 138 with positioned sensor carrier 130 and 2C shows a flow simulation result of the flow in the area of the bypass channel and in the immediate vicinity of the plug-in sensor 122.

2A shows the bypass channel cover 138, the plug-in sensor housing 136, also called the device housing, the electronics compartment cover 140. Furthermore, an area 154 is marked in which the sensor carrier 130 is located. These components are glued together. The flow-guiding channel system extends from the inlet 146 via a first flow path to the bypass channel outlet 156. The sensor carrier 130 with the micromechanical sensor membrane is located in this path.

In 2 B the division of the total mass flow at the inlet 146 of the duct system into the bypass duct mass flow and the main flow duct mass flow is also indicated by arrows. The majority of the incoming mass flow exits again at the main flow channel 152 . Only a small part of the mass flow reaches the sensor carrier 130 with the micromechanical sensor chip 128, which contains the sensor membrane, along the centrifugal deflection 155 and counter-contour with tear-off edge and finally exits the plug-in sensor 122 at the bypass channel outlet 156. In addition, in 2 B the main flow channel outlet 158 is shown. In area 160, a 90° configuration of the upstream face wall and the underside in the inlet 146/main flow channel 152 area is shown.

The geometric design described above leads to an unsteady flow at the junction of bypass channel 150 and main flow channel 152 even in the case of stationary flow boundary conditions. This situation can be illustrated with the help of a flow simulation. In 2C shows the velocity distribution determined by flow simulation in an XY sectional plane through the bypass duct 150 and main flow duct 152 for a total mass flow of 80 kg/h through a flow tube 114 of size 6.4 (nominal engine air mass flow 640 kg/h) into the the plug-in sensor 122 was installed.

The micromechanical sensor membrane is located in area 162 .

The division of the total mass flow into the mass flow in the main flow channel 152 and the mass flow in the bypass channel 150 can be seen clearly. The stagnation point 164 on the wall opposite the centrifugal deflection is characteristic of the branching. A stagnation point migration can be seen in area 164 when different simulation times are considered. Furthermore, a flow separation can be seen in area 166 . The ratio of the branching mass flows is not constant even under stationary flow boundary conditions, but moves according to the flow-mechanical boundary conditions. These boundary conditions include, among other things, total mass flow, pressures at the inlets and outlets, degree of turbulence, angle of attack of the plug-in sensor 122 in the flow tube 114. Both the flow around the plug-in sensor and the flow through the channel system in the plug-in sensor 122 are almost always transient in character. The branching topology with separate outlets for the main flow 152 and the bypass channel 150 thus ensures mass flow fluctuations at the micromechanical sensor membrane. Depending on the associated frequencies, these fluctuations can be relevant to the characteristic curve and thus also have a negative impact on the adjustability in series production to a target characteristic curve or cause higher signal noise.

Detachments vary in time and space, and can be modified by acoustic excitation, as can the transition from laminar to turbulent flow. Detachments and transition states in the bypass duct system therefore influence the corresponding flow and velocity profiles, which can ultimately lead to the flow in the bypass duct system and, as a result, in particular the velocity profile and thus the heat transfer, in the event of strong acoustic disturbances, for example due to turbocharger or compressor excitation - relevant mass flow in the boundary layer of the micromechanical sensor element, ie above the sensor membrane and sensor chip 128 is changed. The aim of the measures described in this application is to avoid or reduce acoustic pressure and speed fluctuations in the area of the plug-in sensor 122, because these acoustic pressure and speed fluctuations can spread through the duct system to the sensor chip.

3 shows a detailed view of a further embodiment of a bypass duct cover 138 with a topologically different duct system 112. The bypass duct 150 and the main flow duct 152 have a common outlet 148. For this purpose, the bypass duct cover 138 has a merging zone 170 of the bypass duct 150 and the main flow duct 152 . Furthermore, in 3 a wall 172 is shown on an underside of the inlet 146 or a main flow channel 152, which influences various aerodynamic and acoustic aspects due to its geometric configuration and transition into the merging zone 170.

What the bypass channel systems shown and explained have in common is that their respective inlets 146 and outlets 148 have characteristic lengths and cross-sectional profiles. These are relevant to acoustics and acoustic wave propagation. Cross-section transitions and topological areas, such as those in 3 The junction zone 170 shown of the main flow 152 and bypass channel 150 influence the propagation of high-frequency speed and pressure disturbances to the micromechanical sensor membrane. An acoustic plenum, for example a cavity connected to the duct system due to incompletely sealed adhesions or an outlet into the free external flow, can also lead to a change in the acoustic propagation of disturbances.

4A shows an example of an acoustic wave running from the turbocharger of an internal combustion engine or the compressor of a fuel cell system to the plug-in sensor 122, together with the reflected wave and acoustic superimposition with pronounced wave antinodes and nodes. Such waves are modified at cross-sectional jumps or reverberant objects up to total reflection. Sound waves can therefore be reflected, for example from the area of the air filter or any resonator chambers, which are often used by vehicle manufacturers to generate a brand-specific sound from their engines or to reduce unwanted, mostly low-frequency, audible resonances. The superimposition of incoming and reflected waves can also lead to more or less stationary, standing waves or to acoustic beats, as in 4A shown as an example. Time signals of such acoustic disturbances can be recorded, for example, using hot-wire measurement technology. The hot-wire measurement technique enables flow velocities to be measured up to very high corner frequencies, ie the so-called acoustic velocity, i.e. the high-frequency fluctuations in velocity, can be measured. This in turn can be converted into acoustic sound pressures and sound intensities. This makes it possible to characterize the strength of the acoustic excitation up to the sound waves with frequencies of up to approx. 20 kHz, which are often suppressed by turbochargers. This noise radiation often occurs due to high aerodynamic loads on the fast-rotating turbocharger compressor blades. In 4B hot-wire signals for recording velocities and sound velocities at a measuring point in the flow tube 114 but outside of the plug-in sensor 122 are shown. 4C shows hot-wire signals in the bypass channel system 150, in particular in the bypass channel 150, approximately at the position of the sensor carrier 130. The hot-wire signals can be different, in particular with regard to the amplitude or sound intensity. Inside the bypass channel 150 can, as compared between 4B and 4C clearly higher sound pressures than exist outside of the plug-in sensor. The X-axis is the 4B and 4C the time t, on the Y-axis the velocity v or acoustic velocity of sound plotted. In the case of turbochargers in combustion engines, the volume at the measuring points described can reach a volume of 130 dB or more. Such acoustic disturbances are relevant with regard to the effects of characteristic curves and the actually desired measurement of the aerodynamic, lower-frequency measurement of the mass flow to the combustion engine or in the fuel cell.

In the 4D and 4E detailed views of a channel system 112 with main flow channel 152 and bypass channel 150 are shown. 4A until 4E also show the aerodynamic, non-acoustic pressure level during normal forward flow through the flow tube 114 to the intake valves of an internal combustion engine. At the inlet 146 of the duct system 112, as shown in FIGS 4D and 4E , there is a relatively high static pressure (marked "+"), at the main flow passage outlet 158 in 4D a neutral pressure (marking "0") and at the outlet of all duct system types a relatively low pressure (marking "-") due to the flow acceleration immediately before the outlet. The different spacing of the outlets in relation to the inlet 146 can be clearly seen. In order to ensure the normal aerodynamic flow through the channel system, a pressure difference driving the flow must exist. In the case of acoustic disturbances, pressure and velocity fluctuations can occur at the bypass inlets and outlets, depending on the frequency and thus the wavelength and sound intensity. In 4A In particular, the entry from the wave antinode to the wave node, i.e. over a quarter wavelength, is shown. Depending on the speed of the turbocharger compressor, frequencies of up to approx. 20 kHz can be present. The corresponding wavelengths and quarter-wavelengths are thus in the order of centimeters and fractions thereof. The coupling of this disturbance into the bypass canal system can in turn lead to resonances due to the characteristic acoustic dimensions of the branches of the canal system. Depending on the resonance modes, which can be visualized using the finite element method with density-bearing elements, for example, there can be strong pressure and speed fluctuations in the area of the sensor carrier 130 and the sensor chip 128 with its micromechanical sensor element.

5A shows the measuring principle of a device 110 according to the invention. The sensor chip 128 with its micromechanical sensor membrane is embedded in the sensor carrier 130 produced in the micro-injection molding process and is overflown during normal operation as shown. above that Sensor chip 128 and the membrane with the integrated heating zone 174 and the integrated electrical resistance taps therefore there is a flow boundary layer in which heat is given off to the air flowing past. In addition, heat conduction occurs in the micromechanical sensor membrane 173 and in the sensor chip 128 . In the case of overflow, this means that different temperatures T1 and T2 are measured at position 176 upstream of heating zone 174 and at position 178 downstream of heating zone 176 . The dashed line qualitatively shows the temperature curve in the membrane in the case of overflow. This temperature profile, and thus the resulting temperature difference ΔT, is easily measurable and differs from the state without flow, which is characterized by the solid line.

In 5B a velocity distribution of the background flow is shown. In 5C a velocity distribution of a pulsating flow without background flow is shown.

The velocity gradient du/dy is essential for the heat transport from the membrane into the boundary layer flow. This speed gradient of the aerodynamic basic flow is only subject to relatively small fluctuations, which are associated with relatively small frequencies and length scales. In the case of strong acoustic disturbances, a strongly pulsating fluctuation of the velocity gradient is superimposed on the basic flow (the so-called 2nd Stokes problem), which also changes the heat transfer and thus the measurable temperature difference.

Due to the non-linear heat transfer, these fluctuations are not mapped into an output signal, e.g. a voltage U, as in 5D presented qualitatively. A sinusoidal fluctuation in the mass flow ultimately leads to a low mass flow reading. This reduced mass flow display, also referred to as a negative dm/m characteristic curve error, has been demonstrated on various combustion engines from different manufacturers in the event of strong acoustic excitations. Similar effects and deviations can be expected for future applications in fuel cell systems with air compressors. Apart from this, flow conditions and the resulting velocity fields can be changed at various points on the plug-in sensor 122, in the duct system 112, in the bypass duct 150 and on the sensor carrier 130 due to strong acoustic interference, so that additional characteristic curve deviations can arise. Increased signal noise can also occur, which can make the application on the control unit side more difficult or impossible without further measures such as a low-pass filter.

6A until 6C show an exemplary embodiment of an acoustic grating 126. In 6A the acoustic grille 126 is shown in a perspective view in FIG 6B in a sectional view. 6C shows an exemplary embodiment of a surface profiling.

The acoustic grille 126 may include at least one outer annular member 180 and at least one inner annular member 182 . The inner annular member 182 and the outer annular member 180 may be concentric about an axis of rotation 184 of the flow tube 114 . The outer annular member 180 and the inner annular member 182 may be connected to each other by a plurality of web members 186 . The web elements 186 can be arranged radially about the axis of rotation 184 of the flow tube 114 . The ridge members 186 may be spaced evenly or unevenly from one another.

A clear width between the inner annular element 182 and the outer annular element 180 can be in the order of the wavelengths or quarter-wavelengths of the acoustic disturbances.

As in 6C shown, at least one surface of at least one element selected from the group consisting of: the inner annular element 182, the outer annular element 180, at least one of the web elements 186, at least one surface profile 190. In particular, they can be profiled, differently curved surfaces. This makes sense because of the continuously changing reflection angle of the acoustic waves, but also for aerodynamic reasons. The injection-molded surfaces represent sound-hard boundaries of the sound volume. In particular, the sound wave fronts running upstream from the compressor of the turbocharger and possibly reflected several times in the pipe system can hit the acoustic grid at different angles and are accordingly reflected in different partial volumes. At high speeds of the turbocharger and correspondingly high frequencies, what are known as transverse modes or also waves referred to as cut-off modes can run transversely to the axis of rotation 184 of the flow tube 114 . Beats and resonances of these modes are also possible. The in the 6A and 6B The variant of the acoustic grid shown and described divides the total volume in this pipe section into correspondingly smaller sub-volumes and already provides for an irregularization of the radiation upstream of the plug-in sensor 122.

In addition to or independently of the continuous profiling of the ring and web elements 180, 182, 186, the surfaces 188 of the acoustic grille 126 can also be designed as in 6C are indicated to be parqueted, which leads to a further irregularization of the reflections and thus to a further reduction of detrimental amplification effects, in particular with regard to the sound intensity or sound speed, i.e. the high-frequency speed fluctuations. The sound energy emitted by the turbocharger is therefore less directional and is spatially scattered. As in 6C shown, the injection molding tool separation must be considered as a boundary condition when realizing such tiling. In 6C the tool parting line 192 is shown. When the tool parts move towards one another, this is based on the largest elevations, here, for example, on the largest thicknesses of the underlying profiles.

7A and 7B show further exemplary embodiments of an acoustic grid 126.

As in 7A shown, at least one edge 194 of at least one element selected from the group consisting of: the inner ring-shaped element 182, the outer ring-shaped element 180, at least one of the web elements 186, at least one edge profile 191. In particular, edges 194 may be downstream edges. This feature can also be used to intervene further in the reflection of the acoustic waves. The continuous change of the remaining areas can be done, for example, as in 7A shown via sinusoidal curves or other curves.

Another configuration option is shown 7B . The acoustic grille 126 may include at least a first inner annular member 196 and at least a second inner annular member 198 . The first inner annular member 196 and the second inner annular member 198 may be concentric about the axis of rotation 184 of the flow tube 114 . The first inner annular member 196 and the second inner annular member 198 may be connected to one another by a plurality of other web members 200 . The additional web elements 200 can be arranged radially around the axis of rotation 184 of the flow tube 114 .

The fragmentation of the sound volume can be realized by an additional ring-shaped element and additional webs for connecting the ring-shaped elements. Distances between the elements can be selected in such a way that they are not multiples of one another, in order to avoid undesired superimposition of the sound waves and to further entangle the phase position of the acoustic waves or wave packets in the above sense. The amplitudes and wavelengths of the sinusoidal curves are also not multiples of one another, in order to further increase the irregularization of the reflections in the sound volume.

8th shows another exemplary embodiment of an acoustic grille 126.

The acoustic grille 126 may include at least one annular member 202 and the acoustic grille 126 may include at least two straight ribs 204 extending within the annular member 202 .

At least one element selected from the group consisting of: the annular element 202, one of the at least two straight ribs 204, can have the surface profile and/or the edge profile of the at least one edge 194.

Claims (10)

Device (110) for detecting at least one parameter of a fluid medium flowing through a channel (112), in particular an intake air mass of an internal combustion engine or a fuel cell system, the device (110) comprising: • at least one flow tube (114); and • at least one plug-in sensor (122) which is or can be inserted at least partially into the flow tube (114), in which the channel (112) is formed, the plug-in sensor (122) furthermore having at least one sensor chip (128) arranged in the channel (112) for determining the parameter of the fluid medium, wherein the plug-in sensor (122) has at least one inlet (146) into the channel (112) and one outlet (148) from the channel (112); characterized in that the device (110) further comprises at least one acoustic grid (126), the acoustic grid (126) being arranged at one end (119) of the flow tube (114), in particular at one end (119) of the flow tube (114) oriented toward a source of acoustic interference; and that the acoustic grating (126) has at least one profiling selected from the group consisting of: a surface profiling (190) of at least part of a surface of the acoustic grating (126); an edge profile (191) of at least one edge (194) of the acoustic grid (126). The device (110) of the preceding claim, wherein the surface profiling (190) is selected from the group consisting of: a continuous surface profiling; a parquetted surface profiling; a surface profiling by means of linear and/or abrupt level differences;. Device (110) according to one of the preceding claims, wherein the edge profiling (191) of the at least one edge (194) of the acoustic grating (126) is selected from the group consisting of: a sinusoidal profiling, in particular a sinusoidal profiling, which in terms of wavelength and/or or amplitude is designed differently at different edges; a profiling with battlements or recesses as segments, in particular with a right-angled or non-right-angled connection of the segments; a profiling with a polynomial-like curve. Device (110) according to any one of the preceding claims, wherein the acoustic grille (126) has at least one outer annular element (180) and at least one inner annular element (182), the inner annular element (182) and the outer annular element (180 ) are concentric about or offset from an axis of rotation (184) of the flow tube (114), the outer annular member (180) and the inner annular member (182) being interconnected by a plurality of web members (186), the web members (186) are preferably arranged radially around the axis of rotation (184) of the flow tube (114). Device (110) according to one of the two preceding claims, wherein the web elements (186) are spaced from one another evenly or unevenly. Device (110) according to one of the three preceding claims, wherein at least one element selected from the group consisting of: the inner annular element (182), the outer annular element (180), at least one of the web elements (186), the surface profiling (190 ) and/or the edge profiling (191) of the at least one edge (194). The device (110) of any preceding claim, wherein the acoustic grille (126) includes at least a first inner annular member (196) and at least a second inner annular member (198), the first inner annular member (196) and the second inner annular member (196). annular member (198) are disposed concentrically or non-concentrically about the axis of rotation (184) of the flow tube (114), the first inner annular member (196) and the second inner annular member (198) being interconnected by a plurality of further web members ( 200) are connected, the further web elements (200) being arranged radially around the axis of rotation (184) of the flow tube (114) or in a different orientation. Device (110) according to one of the preceding claims, wherein the acoustic grille (126) has at least one annular element (202), the acoustic grille (126) further having at least two straight ribs (204) which are located within the annular element (202 ) extend. Device (110) according to the preceding claim, wherein at least one element selected from the group consisting of: the ring-shaped element (202), one of the at least two straight ribs (204), the surface profile (190) and/or the edge profile (191 ) having at least one edge (194). Method for producing a device (110) for detecting at least one parameter of a fluid medium flowing through a channel according to one of the preceding claims, the method comprising the following steps: a) providing the flow tube (114); b) connecting the probe (122) to a dome portion of the flow tube (114); and c) connecting the acoustic grid to the flow tube (114).

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