DE102017204041A1 - Sensor device for detecting at least one flow characteristic of a fluid medium - Google Patents

Abstract

A sensor device (110) for detecting at least one flow characteristic of a fluid medium is proposed. The sensor device (110) comprises:
At least one sensor element (120) for detecting the flow property of the fluid medium, wherein the sensor element (120) has at least one substrate (124) and at least one cavern (132) formed in the substrate (124), the substrate (124) forming a Measuring side (152) and a mounting side (154), wherein the cavern (132) may be opened or closed to the mounting side (154) and on the measuring side (152) of a sensor membrane (128) is covered, which of the fluid Medium is overflowable,
At least one sensor housing (112), wherein the sensor housing (112) comprises at least one flow channel (114) with at least one inlet opening (116) and at least one outlet opening (118) for the fluid medium, wherein the sensor element (120) into the flow channel ( 114) protrudes; characterized in that the sensor element (120) is designed such that an exchange of the fluid medium between the measuring side (152) and the cavern (132) through the sensor element (120) is made possible therethrough.

Description

State of the art

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

The invention is described below in particular with reference to so-called hot-film air mass meter, as described for example in Konrad Reif (ed.), Sensors in the motor vehicle, 1 st edition 2010, pages 146-148. Such Heißfiluuftmassenmesser are usually based on a sensor chip, in particular a silicon sensor chip, with a measuring surface, which is overflowed by the flowing fluid medium. The sensor chip usually 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. From an asymmetry of the temperature profile detected by the temperature sensors, which is influenced by the flow of the fluid medium, it is possible to deduce a mass flow and / or volume flow of the fluid medium. Heißfileinuftmassenmesser are usually designed as plug-in sensor, which is fixed or interchangeable introduced into a flow tube.

For example, this flow tube may be an intake tract of an internal combustion engine.

Sensor membranes can usually have a thickness of a few micrometers. A pressure difference between an upper side and a lower side of the membrane can fundamentally lead to mechanical destruction. Therefore, sensor chips may be mounted so that a back part is glued and a front part comprising the membrane remains free and exposed to the fluid medium.

Out EP 2789 994 A1 is an air flow measuring device with good measurement accuracy known. The air flow measuring device comprises: a subchannel which receives a part of a fluid flow of an intake pipe; a sensor element disposed in the bypass passage to measure fluid flow; a circuit portion which converts the fluid flow detected by the sensor element into an electrical signal; a plug part having a plug electrically connected to the circuit part; and a housing supporting the sensor element and the circuit part. The sensor element is arranged in the intake pipe. The sensor element includes a cavity disposed in a semiconductor substrate and a membrane having a thin film portion covering the cavity. The sensor element is attached to a lead frame. At least one hole is disposed on the lead frame for communication between the cavity and the exterior of the molding unit.

Despite the advantages provided by these sensor devices, they still have room for improvement. In particular, the low mechanical strength of sensor chips with knife membranes is still a technical challenge.

Disclosure of the invention

Therefore, a sensor device for detecting at least one flow characteristic of a fluid medium is proposed, which at least largely avoids the above-described disadvantages of known sensor devices. In particular, the sensitivity of the membrane of conventional sensor chips should be taken into account so that in particular flow-related or climate-induced pressure differences between an overflowed from the fluid medium top of the sensor chip, hereinafter also referred to as the measurement side, and a bottom of the sensor chip, hereinafter also referred to as mounting side, not lead to destruction of the sensor chip. For this purpose, in particular an improved pressure equalization between the measuring side and the mounting side should be created.

With respect to the at least one flow characteristic to be detected, which can be detected qualitatively and / or quantitatively, reference may be made, for example, to the above description of the prior art. In particular, this flow property may be a flow velocity and / or a mass flow and / or a volume flow of the fluid medium. The fluid medium may in particular be a gas, preferably air and / or an exhaust gas. The sensor device can be used in particular in motor vehicle technology, for example in the intake tract of an internal combustion engine. However, other applications are possible in principle.
The invention is described below in particular with reference to so-called hot-film air mass meter, as described for example in Konrad Reif (ed.), Sensors in the motor vehicle, 1 st edition 2010, pages 146-148. It was pointed out that, however, other embodiments of the sensor device according to the invention are possible.

The sensor device according to the invention for detecting at least one flow characteristic of a fluid medium comprises at least one sensor element for detecting the flow property of the fluid medium. This sensor element can in particular be designed as a sensor chip, for example as a semiconductor chip.

The sensor element has at least one substrate, in particular a semiconductor substrate, and at least one cavity formed in the substrate. The substrate has a measurement side and a mounting side. The cavern can be opened or closed to the mounting side. The cavern is covered on the measuring side by a sensor membrane. The sensor membrane can be overflowed by the fluid medium. Furthermore, the sensor device comprises at least one sensor housing. The sensor housing comprises at least one flow channel with at least one inlet opening and at least one outlet opening for the fluid medium. The sensor element protrudes into the flow channel, for example in that a support element of the sensor element projects with the sensor element into the flow channel. The sensor element is designed such that an exchange of the fluid medium between the measurement side and the cavern through the sensor element is made possible.

In the context of the present invention, a "sensor housing" is basically a one-part or multi-part device which at least largely closes off the sensor device and at least largely protects it against mechanical effects and preferably also other types of actions, for example chemical effects and / or humidity influences. In particular, the sensor housing may comprise at least one plug-in sensor, wherein the plug-in sensor can be introduced into the flowing fluid medium. The plug-in sensor and the sensor housing may in particular be made at least partially of a plastic material, for example by means of an injection molding process. The sensor housing, in particular the plug-in sensor, for example, be plugged into a flow tube or be permanently mounted in a flow tube, so that the plug-in sensor, for example, flows around the fluid medium, which flows through the flow tube. The plug-in sensor can be fixed or detachably mounted in the flow tube. The flow tube may be formed separately or may also be part of the sensor device.

A "flow channel" in the sense of the present invention is basically to be understood as meaning any hollow body or hollow space through which a fluid medium can flow. In particular, it may be an elongated cavity, which may be designed straight or curved as desired. Furthermore, the flow channel can also be configured branched. The flow channel can in principle have any desired cross section, for example a square, rectangular, round, oval or polygonal cross section. The inlet port may be configured to transport the fluid medium into the flow channel. The inlet opening can therefore also be referred to as an inflow opening. Furthermore, the outlet opening may be arranged to transport the fluid medium out of the flow channel. The outlet opening can therefore also be referred to as a discharge opening.

A "sensor element" in the sense of the present invention basically means any device that is set up to detect at least one measured variable, for example a physical and / or chemical measured variable, in particular an optical and / or electrical measured variable. The sensor element may in particular be designed to generate at least one sensor signal, in particular at least one electrical sensor signal, for example an analog and / or digital sensor signal. A sensor element for detecting a flow property of a fluid medium is basically an arbitrary sensor which is set up to qualitatively and / or quantitatively detect the flow property. The sensor element can therefore also be referred to as a flow sensor. In particular, the sensor element may be at least one hot-film air mass measuring chip. In particular, this Heißfilmuftmassenmesserchip comprise at least one silicon chip, with a measuring surface, which is overflowed by the flowing fluid medium. On this sensor surface, for example, at least one heating element and at least two temperature sensors can be located, wherein from an asymmetry of the temperature profile measured by means of the temperature sensor on the at least one flow property can be closed.

The sensor element may in particular be a micromechanical sensor element. In the context of the present invention, the term "micromechanical" is generally to be understood as the property of a three-dimensional structure which has dimensions in the micrometer range, ie in the region below 1 mm. For example, widths of caverns, lateral dimensions of membranes or similar characteristic Dimensions that are in this range. However, dimensions in the range above 1 mm are also conceivable.

The sensor element protrudes into the flow channel. For example, the sensor element can be fastened on or in a sensor carrier, for example a sensor carrier made of plastic, for example in the form of a wing, which protrudes into the flow channel. The sensor chip may have, for example, a measuring surface or sensor surface which is arranged on the measuring side. The sensor element can protrude into the flow channel in such a way that the measurement side is completely or partially exposed, in particular the measurement surface, to the fluid medium and can be overflowed by the fluid medium.

As already stated above, the sensor element comprises the at least one sensor membrane. In principle, a "membrane" in the sense of the present invention is to be understood as meaning any element having an elongate shape and a thickness, wherein the dimension of the element in a lateral dimension exceeds the thickness of the element, for example by a factor of 10 to 1000, preferably by a factor of 200 to 500. Such membranes can be prepared, for example, by appropriate semiconductor techniques, such as etching, in which the substrate is etched in a section such that after completion of the process, only the membrane remains. In this etching process, the cavern is then simultaneously produced, which is covered by the membrane. In the context of the present invention, a "sensor membrane" is accordingly generally understood to mean a membrane which itself acts as a sensor or which carries one or more sensor elements. For example, as is usual with hot-film air mass meters, at least one heating element and at least two temperature sensors can be arranged on the sensor membrane, in particular on a side of the sensor membrane facing the measuring side.

Furthermore, as already explained above, the sensor element has the at least one substrate. In particular, it may be a semiconductor substrate which is micromechanically structured. The micromechanical structuring may in particular include the formation of the cavern and the membrane, so that the semiconductor substrate forms, for example, a frame which surrounds the cavern and is spanned by the membrane, which itself is a component of the semiconductor substrate or is formed separately. The substrate may be, for example, a disk-shaped or plate-shaped semiconductor substrate. In particular, the substrate may comprise a plurality of semiconductor substrates, which are interconnected by wafer bonding. The substrate may be formed in particular as a chip. In particular, the substrate may comprise silicon. Other semiconducting or insulating materials such as silicon carbide, GaN, sapphire and glass are also conceivable.

Under a "cavern" in the context of the present invention is basically to understand any cavity. In particular, it may be an open and / or free-form cavity or a closed cavity. The cavern can in principle have any basic shape in cross section, for example a trapezoidal shape. The cavern can be arranged facing a carrier element. The sensor element can be designed, for example, such that the membrane faces the measurement side and the cavity arranged below the membrane is opened towards the mounting side or is closed.

As already stated above, the sensor element, in particular the substrate, has a measuring side and a mounting side. In principle, these two sides preferably designate any two sides of the sensor element, for example the sensor chip, which lie opposite one another. These two sides are preferably arranged parallel to one another, for example in that these two sides form the mutually opposite flat surfaces of the sensor element, in particular of the sensor chip. Thus, the measuring side may in particular be the side of the sensor element which faces the fluid medium, whereas the mounting side may be the side which faces a sensor carrier. For example, the sensor element can be arranged on a surface of the sensor carrier and / or be introduced into a depression of the sensor carrier, wherein the mounting side assigns the sensor carrier. The sensor element may, for example, be connected to the sensor carrier in a material-locking manner, for example by an adhesive method. The sensor carrier may for example be designed as a wing and may protrude into the flow channel. A sensor surface of the sensor element, also referred to as sensor surface or measuring surface, can be arranged on the measurement side. The sensor surface may in particular be arranged on the membrane, also referred to as sensor membrane. Accordingly, the sensor membrane can be arranged in particular on the measurement side.

The sensor element can be arranged, for example, on a sensor carrier. The sensor carrier may for example be connected to an electronic module of the sensor device or be part of the electronic module. This electronic module can be arranged for example in an electronics compartment in the sensor housing, which of the flow channel is formed separately, wherein the sensor carrier protrudes from the electronics compartment into the flow channel. In particular, the electronic module can be embodied in one piece and, in particular, can carry a control and / or evaluation circuit of the sensor element, which is set up to control the sensor element and / or to receive signals from the flow sensor. Accordingly, the electronic module may have, for example, at least one circuit carrier, which is preferably mechanically connected to the sensor carrier. For example, the circuit carrier can be arranged in an electronics compartment of the sensor housing, and the sensor carrier can protrude out of this electronics compartment into the fluid medium.

The sensor device may also include one or more further sensor elements for detecting at least one further physical and / or chemical property of the fluid medium, for example at least one humidity sensor, a temperature sensor, a pressure sensor. Under a pressure sensor is basically to understand any sensor element which is adapted to detect a pressure of the fluid medium. In particular, these may be pressure sensors, as described, for example, Konrad Reif (ed.), Sensors in the motor vehicle, 1st edition 2010, pages 80-82 and 134-136. However, other types of pressure sensors are alternatively or additionally usable, for example pressure sensors, which are based directly on the use of one or more strain gauges or similar pressure sensor elements. For example, a temperature sensor may be arranged on an outer side of the sensor housing. However, other embodiments are possible in principle. The temperature sensor may in particular comprise at least one temperature-dependent resistor. Alternatively or additionally, other types of temperature sensors can be used. In particular, the temperature sensor can be overflowed freely by the flowing fluid medium. The temperature sensor can be connected in particular by a frictional connection and / or positive connection with the sensor housing, for example by caulking leads of the temperature sensor with an outer wall of the sensor housing or connected in any other way. Under a moisture sensor is basically any sensor element to understand, which is adapted to detect a moisture of the fluid medium. For example, resistive and / or capacitive sensor elements come into consideration here, as are known from the prior art. Examples of such humidity sensors are described in Konrad Reif (ed.), 1st ed. 2010, pages 98-101. However, other types of humidity sensors are in principle alternatively or additionally considered for use in the context of the present invention.

As already stated above, the sensor element is designed such that an exchange of the fluid medium between the measurement side and the cavern through the sensor element is made possible. In particular, the fluid medium can be exchangeable between an external environment of the sensor element and the cavern. An "external environment" is to be understood in particular as a space which directly adjoins the sensor element, in particular directly to the sensor membrane. In particular, the external environment may be an interior of the flow channel of the sensor housing. In particular, the term "exchange" designates that the fluid medium can enter the cavern from the external environment, for example the flow channel, and / or vice versa. The exchange can be done for example as a flow and / or by diffusion. In particular, a pressure equalization and / or a ventilation can be ensured in this way. In particular, the exchange between the measuring side and the cavern can be effected by at least one connecting element. In the context of the present invention, a "connecting element" is in principle to be understood as meaning any device which is set up to permit a fluid exchange between at least two spaces separated from one another. In particular, the at least two spaces separated from one another can be separated from one another by an element, and the connecting element can be arranged on the element and / or be part of the element. As explained in more detail below, the connecting element may for example comprise at least one passage opening, for example a channel, through the sensor element. In addition, the sensor device may also comprise a different type of connecting element, for example pores. In particular, the pores can be designed such that a percolation threshold can be exceeded so that a fluid passage through the pores from the measurement side to the cavern or vice versa is possible.

In particular, the sensor element may comprise at least one passage opening between the cavern and the measuring side. This passage opening can be formed, for example, in a semiconductor chip of the sensor element, within the sensor membrane and / or outside the sensor membrane. The term "passage opening" refers in particular to an opening which completely penetrates any element. The passage opening may extend from a first surface of the element via an interior of the element to a second surface of the element and thus may act as a connection between the first surface and the second surface. The passage opening can in principle have any desired cross section, for example a round, an oval or an angular cross section. Other embodiments are conceivable in principle. In particular, the passage opening may be formed as a cylindrical opening. In particular, the cross section of the passage opening may be significantly smaller than the cross section of the sensor membrane, for example by at least a factor of 2, at least a factor of 5, at least a factor of 10 or even at least a factor of 50 or at least a factor of 100 Through openings have, for example, at least two through holes, preferably at least three through holes and more preferably at least four through holes.

For example, the at least one passage opening may be formed wholly or partly in the sensor membrane. The passage opening may extend transversely, in particular perpendicularly, to a surface of the sensor element, for example, penetrate the sensor membrane vertically.

For example, the sensor membrane in plan view may have an angular shape, and the sensor membrane may have a plurality of through openings, which are each arranged in corners of the sensor membrane.

As already stated above, the sensor element may comprise the substrate. The passage opening can in particular be arranged wholly or partly outside the sensor membrane. The measuring side can be designed just. A passage opening longitudinal axis may be arranged transversely to the surface of the measuring side. The passage opening longitudinal axis can be arranged at an angle of 10 ° to 80 °, preferably from 20 ° to 70 ° and particularly preferably from 30 ° to 60 ° to the surface of the measuring side. However, other embodiments are conceivable in principle. The cavern may be delimited by at least one sensor substrate surface. The sensor substrate surface may be part of a surface of the recess. The passage opening can open inside the sensor substrate surface.

It can be provided one or more through holes. More than one passage opening is particularly useful in the case in which a passage opening is clogged by dirt, to provide one or more other functional through openings available. The one or more passage openings are preferably positioned in one or more areas where low mechanical stresses occur.

Furthermore, the sensor membrane may be a porous membrane which is permeable to the fluid medium. In the context of the present invention, a "porous membrane" is basically understood to mean a membrane which has pores in such a way that gas permeation through the membrane is possible. The porous membrane may in particular have pores with an average pore size between 10 nm and 500 μm, in particular between 50 nm and 100 μm, particularly preferably between 100 nm and 10 μm.

The sensor device according to the invention has numerous advantages over known sensor devices. In particular, it may be possible to provide pressure equalization across the sensor membrane without further aids. The sensor membrane may be so porous and / or have holes through which venting and thus pressure equalization is possible. The sensor element can be mounted over the entire surface. This can be avoided aerodynamically disadvantageous columns. Therefore, the sensor device can do without the use of other components. The holes can be generated directly during the manufacture of the sensor element.

Brief description of the drawings

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

• 1 eine schematische Darstellung einer Sensorvorrichtung zur Erfassung mindestens einer Strömungseigenschaft eines fluiden Mediums,
• 2A und 2B ein exemplarisches Sensorelement und in einer Schnittdarstellung (2A) und in einer Draufsicht (2B); und
• 3A und 3B ein exemplarisches Sensorelement in einer Schnittdarstellung (3A) und in einer Draufsicht (3B);

Show it:

• 1 a schematic representation of a sensor device for detecting at least one flow characteristic of a fluid medium,
• 2A and 2 B an exemplary sensor element and in a sectional view ( 2A ) and in a plan view ( 2 B ); and
• 3A and 3B an exemplary sensor element in a sectional view ( 3A ) and in a plan view ( 3B );

Embodiments of the invention

In 1 an exemplary embodiment of a sensor device 110 is shown. The sensor device 110 has at least one sensor housing 112 with at least one flow channel 114 on. The flow channel 114 includes at least one inlet opening 116 and at least one outlet opening 118 for the fluid medium. Furthermore, the sensor device comprises 110 at least one sensor element 120 which is in the flow channel 114 protrudes. The sensor device 110 can be a control and evaluation 122 which is also received in the sensor housing 112. This can also be referred to as an electronic module or designed as an electronic module. The sensor element 120 For example, on or in a sensor carrier 130 be introduced, which in the flow channel 114 protrudes, such that the sensor element 120 is flowed over by the fluid medium.

2A and 2 B show an exemplary sensor element 120 in a sectional view along a longitudinal axis of the sensor element ( 2A ) and in a plan view ( 2 B ). Furthermore, the sensor carrier 130 shown schematically, in which the sensor element 120 is introduced. For example, the sensor element 120 into a depression 121 of the sensor carrier 130 be introduced, as in particular in the sectional view according to 2A is recognizable.

The sensor element 120 in particular has a substrate 124 on. The substrate 124 has at least one in the substrate 124 trained cavern 132 on, as in particular in the sectional view according to 2A is recognizable. The substrate 124 has a measurement page 152 and a mounting side 154 on. The cavern 132 is to the mounting side 154 open or closed and on the measuring side 152 from a sensor membrane 128 covered, which can be overflowed by a fluid medium.

The sensor element 120 can, as stated above, on at least one sensor carrier 130 be applied or incorporated in whole or in part in this. In particular, the sensor carrier 130 have a receptacle, in particular a depression 121 in which the sensor element 120 is included. The cavern 132 can through at least one carrier surface 134 , through at least one sensor membrane surface 136 and through at least one surface 138 of the substrate 124 be limited.

In particular, the sensor membrane 128 at least one passage opening 140 between the cavern 132 and the measurement page 152 of the sensor element 120 include. In particular, the passage opening 140 be formed as a cylindrical opening. The passage opening 140 may be transverse, in particular perpendicular, to a surface 144 the measuring side 152 extend. The sensor membrane 128 can in particular four through holes 140 each, as in 2 B shown in corners 146 the sensor membrane 128 are arranged. However, other embodiments are possible.

3A and 3B show another exemplary sensor element 120 in a sectional view ( 3A ) and in a plan view ( 3B ). The sensor element 120 at least partially corresponds to the sensor element 120 according to the figures 2A and 2 B , so on the description of the 2A and 2 B can be referred to above.

Also in this case, the sensor element 120 again one or more through holes 140 on which a pressure equalization or fluid exchange between the measuring side 152 and the mounting side 154 , especially the measurement side 152 and the cavern 132 , enable. In this embodiment, however, the sensor substrate 132 the at least one passage opening 140 on. Accordingly, the passage opening 140 may also be wholly or partly outside the sensor membrane 128 be educated. It should be noted, however, that mixed embodiments are possible in which at least one passage opening 140 within the sensor membrane 128 is formed and at least one passage opening 140 in the sensor substrate 132 outside the sensor membrane 128 ,

The passage opening 140 according to the embodiment in the 3A and 3B can, as shown, especially outside the sensor membrane 128 be arranged. A passage opening longitudinal axis 148 can be across the surface 144 be arranged. A passage opening longitudinal axis 148 For example, at an angle of 30 ° to 70 ° to the surface 144 the measuring side 152 be arranged. The passage opening 140 can be within the surface 138 lead. For example, the sensor substrate 124 several through holes 140 which are on an outwardly facing surface 150 of the sensor substrate 124 lead.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2789994 A1 [0005]

Claims (9)

A sensor device (110) for detecting at least one flow characteristic of a fluid medium, wherein the sensor device (110) comprises: • at least one sensor element (120) for detecting the flow property of the fluid medium, wherein the sensor element (120) at least one substrate (124) and at least a cavern (132) formed in the substrate (124), wherein the substrate (124) has a measuring side (152) and a mounting side (154), wherein the cavity (132) on the measuring side (152) of a sensor membrane (128 ), which can be overflowed by the fluid medium, • at least one sensor housing (112), wherein the sensor housing (112) at least one flow channel (114) with at least one inlet opening (116) and at least one outlet opening (118) for the fluid medium comprising, wherein the sensor element (120) protrudes into the flow channel (114); characterized in that the sensor element (120) is designed such that an exchange of the fluid medium between the measuring side (152) and the cavern (132) through the sensor element (120) is made possible therethrough. Sensor device (110) according to the preceding claim, wherein the sensor element (120) has at least one passage opening (140) between the cavern (132) and the measuring side (152). Sensor device (110) according to the preceding claim, wherein the at least one passage opening (140) is formed wholly or partly in the sensor membrane (128). Sensor device (110) according to one of the two preceding claims, wherein the at least one through opening (140) is formed wholly or partly in the substrate (124). Sensor device (110) according to the preceding claim, wherein the measurement side (152) is planarized, wherein the passage opening (140) has a passage opening longitudinal axis (148), wherein the passage opening longitudinal axis (148) at an angle of 20 ° to 70 ° to a surface (144) of the measuring side (152) is arranged. Sensor device (110) according to one of the two preceding claims, wherein the passage opening (140) outside the sensor diaphragm (128) is arranged. A sensor device (110) according to any one of the three preceding claims, wherein the cavity (132) is bounded by at least one sensor substrate surface (138), the passage opening (140) opening within the sensor substrate surface (138). Sensor device (110) according to one of the five preceding claims, wherein the sensor element (120) has at least four passage openings (140). A sensor device (110) according to any one of the preceding claims, wherein the sensor membrane (128) is a porous membrane, the porous membrane being permeable to the fluid medium.

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