EP3132256A1

EP3132256A1 - Device for detecting a parameter of a gas, method for operating such a device, and measuring system for determining a parameter of a gas

Info

Publication number: EP3132256A1
Application number: EP15715256.2A
Authority: EP
Inventors: Andreas Krauss; Christoph Schelling
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-04-17
Filing date: 2015-04-09
Publication date: 2017-02-22
Also published as: DE102014207480A1; US20170038273A1; CN106461492A; JP2017514129A; WO2015158599A1

Abstract

The invention relates to a device (100) for detecting a parameter of a gas. The device (100) comprises at least one cavity (104) for receiving the gas from an outer area (108) and at least one membrane (106) for separating the cavity (104) from the outer area (108), wherein a first membrane (106) side (110) facing the outer area (108) has a first layer (114) of an electrically conductive material, and a second membrane (106) side (112) which faces the cavity (104) and lies opposite the first side (110) has a second layer (116) of an electrically conductive material. At least one portion of the membrane (106) has an ion-conductive material. The invention also relates to at least one pressure measuring element (118) which is arranged on the membrane (106) for detecting a gas pressure in the cavity (104).

Description

description

title

Device for detecting a parameter of a gas, method for operating such a device and measuring system for determining a parameter of a gas

State of the art

The present invention relates to a device for detecting a parameter of a gas, to a measuring system for determining a parameter of a gas, to a method for operating a device for detecting a parameter of a gas, to a corresponding device and to a corresponding computer program. Exhaust gas sensors for the detection of oxygen or nitrogen oxides are currently produced almost exclusively in ceramic technology or LTCC (Low Temperature Cofired Ceramics, low-temperature incineration ceramics). Active layers, which are used as ionic conductor, are usually made of yttria stabilized zirconia (YSZ) and are combined with other layers, eg. Example, alumina-based insulating layers or conductive layers, for. B. of Pt, which is structured and burned on metal paste pressure.

There are also concepts for constructing solid electrolyte based micromechanical sensors in which the electrical currents are proportional to the ionic currents through the electrolyte.

Furthermore, pressure sensors are known, which can measure small differential pressures or absolute pressures via a deformable membrane with very high resolution, wherein in the absolute pressure measurement with a gas-tight cavity a constant amount of gas trapped is used. Known processes for the production of cavities, which would be suitable, inter alia, for use in the sensors are, for. An APSM process or processes based on SOI.

DE 102004036032 A1 discloses a method for producing a

Semiconductor device, in which by means of a first epitaxial layer, which is applied to a semiconductor substrate, a membrane above a region in the semiconductor substrate is formed with a first doping and by means of a second epitaxial layer, which is applied to the semiconductor substrate, a structured stabilizing element is attached to the semiconductor substrate ,

DISCLOSURE OF THE INVENTION Against this background, the approach presented here becomes one

Apparatus for detecting a parameter of a gas, a measuring system for determining a parameter of a gas, a method for operating a device for detecting a parameter of a gas, furthermore a device using this method, and finally a

corresponding computer program presented according to the main claims.

Advantageous embodiments emerge from the respective subclaims and the following description.

An apparatus for detecting a parameter of a gas having a cavity for receiving the gas comprises two layers of an electrically conductive

Material on opposite sides of the cavity covering the ion-conducting membrane and arranged on the membrane

Pressure sensing element. Thus, a combined sensor consisting of a pressure sensor and a gas sensor based on an electrical voltage between the layers of the electrically conductive material can be realized.

A constructed according to the concept presented here sensor device allows an improvement of the detection of gases by means of

ion-conducting materials are directly and indirectly measurable, so z. As oxygen or noxious gases such as nitrogen oxides, in particular in the exhaust gas z. B. a vehicle. In a continuation of the approach proposed here, in particular instead of an instantaneous measurement of small gas concentrations, a little effort-requiring measuring mode that integrates over time can be realized. This can take into account applicable emission standards which, instead of detecting momentary concentrations, incorporate integrated values, e.g. B. the

Capture over a specific route, demand. Also, in a sensor device realized according to the concept proposed here, electrical currents can be inserted between the electrically conductive layers which do not require amplification and / or shielding. Thus, the cost of a downstream measurement can be effectively reduced.

The proposed concept also allows for a reduction of

Power consumption and the heating of the sensors, for example, by bringing in the operation of the device, only the ion-conducting layers and not the sensors as a composite on a heater to operating temperature.

By a thus possible very rapid heating a location of the sensors can be chosen freely, for example, with a long distance from unfavorable for a housing of the device, high exhaust gas temperatures of a

Vehicle engine. As a further advantage, in one development of the proposed concept, the use of one of the electrically conductive ones allows

Layers on the ion-conducting element as an electrode and as a heater structure a significantly simplified structure with lower costs and increased

Reliability. A device for detecting a parameter of a gas is presented, the device having the following features: at least one cavity for receiving the gas from an external space; at least one membrane for separating the cavity from the outer space, a first side of the membrane facing the outer space having a first layer of electrically conductive material and a cavity facing, the first side opposite, second side of the membrane a second layer of an electrically conductive material and wherein at least a portion of the membrane comprises an ion conducting material; and at least one pressure measuring element arranged on the membrane for detecting a gas pressure in the cavity. The device may be a sensor device for determining a gas concentration, e.g. B. in the exhaust of a vehicle act. For this purpose, one or more parameters of the gas can be detected, for example a size of a pumping current required for pumping the gas into the cavity and / or a gas pressure of the gas in the cavity. The at least one cavity may be in the form of a well in a substrate for supporting individual ones

Elements of the device may be applied, for example, by an executed on a surface of the substrate etching. The exterior space may refer to an environment outside the cavity. The exterior space may extend between the membrane and a housing of the device or beyond. In the outer space can prevail an ambient pressure. The

The diaphragm may be made of a material that permits elastic deformation and may be configured to form a bulge in the direction of the outside space in response to a gas pressure inside the cavity.

In particular, the membrane may be formed by means of the ion-conducting material to allow diffusion of the gas between the outer space and the cavity. The first and second layers of an electrically conductive material may be metal layers, to which an electrical potential can be applied via electrical contact terminals arranged on them and / or at which an electrical potential can be tapped off via the contact terminals. The pressure measuring element may, for example, be arranged and formed on the side of the membrane facing the outer space in order to detect the gas pressure piezoelectrically or piezoresistively. For example, it may be at the

Pressure measuring element act around a strain gauge or the

Pressure measuring element may have a strain gauge.

According to one embodiment of the device, the first layer of an electrically conductive material, the membrane and the second layer of an electrically conductive material may be formed to the gas at an applied voltage between the first layer and the second layer to pump through the membrane. Alternatively or additionally, the first layer of an electrically conductive material, the membrane and the second layer of an electrically conductive material may be formed to generate an electrical voltage between the first layer and the second layer upon diffusion of the gas through the membrane. So can easily by means of a

Detecting a pumping current for pumping the gas from the outer space into the cavity and / or out of the cavity into the outer space and, alternatively or additionally, by tapping one on the diffusion of the gas

based on a composition of the gas.

In particular, the first layer of an electrically conductive material and / or the second layer of an electrically conductive material may comprise a gas-permeable noble metal. Thus, a gas permeability of the membrane or the ion-conducting portion of the membrane can be advantageously obtained.

According to a further embodiment, the first layer of an electrically conductive material and / or the second layer of an electrically conductive material may have a first electrical contact connection and a second electrical contact connection and be designed to be electrically conductive between the first electrical contact connection and the first second electrical contact terminal to heat at least a portion of the membrane. A required for the heating of the membrane heat can be generated by applying different electrical potentials to the first and second electrical contact connection in a simple manner. So can be dispensed with a heating element in the device and thus costs and space can be saved.

In particular, the pressure measuring element can be arranged outside the portion of the membrane to be heated. Thus, it can be readily ensured that a measuring functionality of the pressure measuring element is not damaged by temperature fluctuations or the pressure measuring element

Temperatures can be affected. According to a particular embodiment, the first layer of an electrically conductive material and / or the second layer of an electrically conductive material may be formed meander-shaped, for example, a plane substantially parallel to the first and second sides of the membrane

meandering. In particular, the position of an electrically conductive material, which is used for heating the portion of the membrane, have the meandering course. So can be provided in a simple and robust way for optimal heating of the membrane, a prolonged heating. In addition, when using a non-gas-permeable material for the layers of an electrically conductive

Material exposed areas are created for a gas passage.

The device may include a stop member for limiting deflection of the diaphragm. The stop element may in particular be arranged on a bottom of the cavity. With this embodiment, damage to the membrane can be avoided in a simple and cost-effective manner.

According to a further embodiment, the device may have at least one second pressure measuring element. The second pressure measuring element may be arranged at a position deviating from a position of the pressure measuring element further position on the membrane. Thus, by detecting the gas pressure at different positions of the membrane, the gas pressure prevailing in the cavity can be determined even more accurately. In particular, a detection direction of the pressure measuring element may differ from a detection direction of the further pressure measuring element. The detection direction may be a direction in which the pressure-measuring element undergoes a physical and / or chemical change in picking up a measured variable. If the pressure measuring element is designed, for example, as a strain gauge, the detection direction of a strain direction of

Strain gauge corresponding. This special training this

Embodiment allows an even more accurate determination of the gas pressure.

According to a particular embodiment, the device may comprise at least one further cavity for receiving the gas from an outer space, at least one further membrane for separating the further cavity from the one External space and at least one further arranged on the membrane

Have pressure measuring element for detecting a gas pressure in the other cavity. In this case, a first side of the further membrane facing the outer space may have a further first layer of an electrically conductive material and a further second layer of an electrically conductive material facing the further cavity facing the first side, second side of the further membrane. At least a portion of the further membrane may comprise the ion conducting material. With this embodiment, two or more sensor elements can be integrated on the device. By the sensor elements can be used independently for the measuring process, can easily a

Functional test of the individual sensor elements are performed.

In particular, by a temporally offset and / or rotating use of the individual sensor elements a time-integrating mode for detecting the gas can be realized.

A measuring system for determining a parameter of a gas is also presented, wherein the measuring system has the following features: the device according to one of the above explained

Embodiments; and an evaluation device, wherein the evaluation device is coupled to the first layer of an electrically conductive material and / or the second layer of an electrically conductive material and / or the pressure measuring element and is designed to be based on at least one electrical potential of the first layer and / or second position and / or based on the detected by the pressure measuring element gas pressure in the cavity to determine the parameter of the gas.

The evaluation device may be configured to determine the gas alternately or simultaneously based on the electrical potential and based on the gas pressure. In particular, the evaluation device can be designed to determine the determination of the time-integral measurement Gas over a predetermined period, such as a ride of a vehicle repeatedly perform.

Furthermore, a method for operating a device for detecting a parameter of a gas is presented, wherein the device has at least one cavity for receiving the gas from an outer space, at least one membrane for separating the cavity from the outer space, wherein a first side of the membrane facing the outer space a first layer of an electrically conductive material and a cavity facing, the first side opposite, second side of the membrane has a second layer of an electrically conductive material and at least a portion of the membrane has an ion-conducting material, and at least one arranged on the diaphragm pressure measuring element for detecting a gas pressure in the cavity, and wherein the method comprises the following steps:

Applying an electrical voltage between the first layer and the second layer to pump the gas through the membrane from the outer space into the cavity; and

Detecting an electrical quantity at least at the first layer and / or the second layer and / or at the pressure measuring element to detect the parameter of the gas.

The electrical quantity, if it is detected at the first layer and / or the second layer, may be, for example, an electric current intensity of a pumping current for pumping the gas through the membrane. If the electrical variable is detected by the pressure measuring element, this may be an electrical voltage based on an elastic deformation of the pressure measuring element.

According to one embodiment, the method may further comprise a step of re-applying the voltage between the first layer and the second layer to pump the gas out of the cavity through the membrane into the exterior space and, correspondingly, a step of re-detecting the electrical quantity at least at the first layer and / or the second layer and / or on the pressure sensing element to recapture the parameter of the gas. This embodiment allows for easy,

cost-effective and flexible way of integrating over time a determination of the gas or a gas composition.

According to another embodiment, the method of operating the device may be implemented as a pulse width modulation method, wherein the step of applying the electrical voltage between the first layer and the second layer alternately with a step of applying an electrical voltage across the first layer or the second layer for heating the

Section of the membrane is executed. Thus, by means of the method, an advantageous combined heating of the membrane and determination of the measured value of the gas can be carried out by means of one and the same device element.

The approach presented here also provides a device which is designed to implement the steps of a variant of a method presented here

implement or implement appropriate facilities. Also by this embodiment of the invention in the form of a device, the object underlying the invention can be solved quickly and efficiently.

In the present case, a device can be understood as meaning an electrical device which processes sensor signals and outputs control and / or data signals in dependence thereon. The device may have an interface, which may be formed in hardware and / or software. In the case of a hardware-based embodiment, the interfaces can be part of a so-called system ASIC, for example, which contains a wide variety of functions of the device. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

Also of advantage is a computer program product or computer program with program code which is stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical disk Memory may be stored and for carrying out, implementing and / or controlling the steps of the method according to one of the above

described embodiments, in particular when the program product or program is executed on a computer or a device.

The approach presented here will be described below with reference to the attached

Illustrated drawings by way of example. Show it:

1 shows a cross section of an apparatus for detecting a parameter of a gas, according to an embodiment of the present invention.

FIG. 2 is a plan view of an apparatus for detecting a parameter of a gas according to another embodiment of the present invention; FIG.

3 is a block diagram of a measuring system for determining a

Parameters of a gas, according to an embodiment of the present invention; and

4 is a flowchart of a method for operating a device for detecting a parameter of a gas, according to an embodiment of the present invention.

In the following description of favorable embodiments of the present invention are for the in the various figures

represented and similar elements acting the same or similar

Reference numeral used, wherein a repeated description of these elements is omitted.

1 shows a schematic representation of a cross-section of an apparatus 100 for detecting a parameter of a gas, according to an embodiment of the present invention. For example, the device 100 may be installed in a vehicle and configured to provide a concentration of

Detect harmful gases in the exhaust of the vehicle. Thus, the device 100 may also be referred to as a sensor device or a sensor. The Device 100 has a substrate 102 in which a chamber or cavity 104 is applied. The cavity 104 is covered by a membrane 106. Thus, the membrane 106 separates the cavity 104 from an exterior space 108. A first side 110 of the membrane 106 faces the exterior space 108, and a second side 112 of the membrane 106 opposite the first side 110 faces the cavity 104. The first side 110 of the membrane 106 has a first layer 114 of an electrically conductive material, and the second side 112 of the membrane 106 has a second layer 116 of an electrically conductive material. Spaced from the first layer 114 of an electrically conductive material is a pressure measuring element 118 for detecting a gas pressure in the cavity 104 on the first side 110 of the membrane 106. The pressure measuring element 118 thus forms a pressure sensor element of the device 100.

In the embodiment of the device 100 shown in FIG. 1, the substrate 102 is formed of silicon. Alternatively, other materials suitable for MEMS technologies may be used. In addition to the provision of the cavity 104, the substrate 102 u. a. as a carrier, in particular for the membrane 106 and the pressure measuring element 118. The pressure measuring element 118 -here not shown here-also needed for a pressure measurement

Include elements, e.g. a temperature sensor or

temperature compensating elements. As a temperature sensor but also other elements of the sensor can be used, e.g. the resistance of a heater or a position 114 or 116 designed as a heater

1, the cavity 104 has been machined out of a surface or main side 120 of the substrate 102, for example by means of an etching process. A region of the surface 120 of the substrate 102 surrounding the cavity 104 is covered by an insulating layer 122. As the cross-section of the device 100 in Fig. 1 shows, the cavity 104 is formed as a cuboidal trough having a flat rectangular bottom 124 and a wall 126 perpendicular to the bottom 124. The cavity 104 is formed flat in that dimensions of the bottom 124 exceed a height of the wall 126.

Ideally, the chamber 104 is made as flat as possible to

low volume at the same time a large area of the membrane 106th to be able to act on. Thus even small amounts of pumped gas can achieve high pressure changes. The height of the chamber wall 126, however, is limited downwards, as with too small a distance of the heated membrane 106 to the chamber floor 124 here also a

Heat transfer would take place. Since the area to volume ratio of the chamber 106 is determined only by the height of the chamber 104, a miniaturization of the chamber 104 and an adaptation to geometric

Requirement of the pressure sensor 118 done. The minimum size of the chamber or cavity 104 may further be determined by reliability aspects, for example, a required minimum size for a pumping element to ensure a function even with deposits.

The membrane 106 has a rectangular shape corresponding to the bottom 124 of the cavity 104, dimensions of the membrane 106 being greater than the dimensions of the bottom 124 of the cavity 104. As the illustration in FIG.

1, a circumferential edge region of the membrane 106 is fixed to the insulating layer 122 of the substrate 102 on an edge region of the substrate 102 which surrounds the cavity 104 and thus separates the cavity 104 from the outer space 108. The membrane 106 is formed from an elastic material and can in response to a prevailing in the cavity 104 relative to the outer space 108 pressure in the direction of the cavity 104 and in the direction of

Exterior 108 arches. To permit transport of the gas through the membrane 106, at least a portion of the membrane 106 has

ion-conducting material. The layers 114, 116 are positioned congruently centered on the respective sides 110, 112 of the membrane 106 parallel to a plane in which the membrane 106 extends. The layers 114, 116 have in the plane of the membrane 106 smaller dimensions than the membrane 106 us in particular as the cavity 104 and are thus spaced from the substrate 102.

In the embodiment shown in Fig. 1, the first layer 114 and the second layer 116 of an electrically conductive material of a

gas-permeable precious metal formed. However, this is not absolutely necessary for the function of the device 100. It can according to

Embodiments also other metals and / or gas-permeable substances and non-metals for the layers 114, 116 are used. In the exemplary device 100 shown in FIG. 1, the first layer 114 and the second layer 116 of electrically conductive material are used as electrodes for generating a pumping current for pumping gas through the membrane 106 from the outer space 108 into the cavity 104 and / or the cavity 104 inserted into the outer space 108. For applying an electrical potential to the first layer 114 and the second layer 116, both layers 114, 116 each have at least one electrical contact connection 127. According to an alternative embodiment, the device 100 is formed using the layers 114, 116 in the above-mentioned embodiment to generate an electrical voltage between the first layer 114 and the second layer 116 upon diffusion of the gas through the membrane 106.

In the embodiment of the device 100 shown in FIG. 1, the pressure sensing element 118 is configured as a strain gauge and configured to provide an electrical voltage based on elastic deformation of the diaphragm 106 due to pump flow based gas transport into the cavity 104 or cavity 104 to create. For limiting a deflection of the membrane 106 in the direction of the cavity 104, the embodiment of the device 100 shown in FIG. 1 has a stop element 128. The stopper member 128 is shown in the illustration

Embodiment in the form of a in the direction of the membrane 106th

extending column centered on the bottom 124 of the cavity 104. To avoid a short circuit between the second layer 116 forming the lower electrode in the illustration and the substrate 102, the

Stop element 128 as the insulating layer 122 comprise an electrically insulating material. Alternatively, the stopper member may be made conductive so that upon contact between the conductive layer 116 and the stopper member 128, e.g. the pumping process is interrupted. Alternatively, the cavity can also be made so that during normal operation of the sensor there is a contact between 116 and 128 and that due to an impermissibly high internal pressure, a bulging of the membrane to a

detectable interruption leads. By a correlation of the signals of the pressure measuring elements and the contact with an electrically conductive Stop element can also take place a function detection or calibration of the pressure measuring elements.

In the exemplary embodiment of the device 100 shown in FIG. 1, the second or lower layer 116 of the electrically conductive material is meander-shaped in a plane parallel to the plane of the membrane 106 and is additionally used here as a heating element for heating one between the layers 114, 116 lying portion 130 of the membrane 106 is inserted. To generate a required for the heating function electrical current flow through the second layer 116, this has a second electrical contact terminal 132. As the illustration in Fig. 1 shows, the pressure measuring element 118 is disposed outside of the heated portion 130 of the membrane 106.

The exemplary sensor 100 shown in FIG. 1 comprises the membrane 106, which divides the interior or cavity 104 and, according to exemplary embodiments, further interior spaces 104 in the form of a closed or limited diffusion-open cavity and the exterior space 108, as well as the element 106

ion-conductive material interposed between the interior 104 and the

Outside space 108 is arranged. At least the part 130 of the membrane 106 made of ion-conductive material is designed to be heated. The strain gauge 118 is disposed outside the heated region 130 of the membrane 106. According to exemplary embodiments, the device 100 may also have further strain gauges 118, which may be arranged on the membrane 106 at further positions deviating from a position of the first strain gage 118.

About the ion-conducting element in the form of the membrane 106, the gas or a plurality of gases is defined from the outer space 108 in the interior or the cavity 104 of the sensor 100 is moved and / or vice versa. This "pumping" of gas provides pressure differences between the inner space 104 and the outer space 108 provided by the pressure sensor 118 here in the form of

Strain gauge are detected. Upon detection of the pumping current and / or the pressure, the gas concentration can be calculated. Be both

Parameters captured simultaneously, the functionality and accuracy of the Device 100 advantageously extended or advantageously checked in terms of a built-in self-test.

In the cross section of an exemplary construction of the sensor 100 shown in FIG. 1, the cavity 104 is covered by the membrane 106. The bending of the

Membrane 106 is detected by the measuring element 118 z. B. piezoelectric or piezoresistive detected. The here central portion 130 of the membrane 106 is heated by the membrane heater here in the form of the lower electrode 116. By the two electrodes 114, 116 above and below the ion-conducting membrane 106 is by applying an electric current gas, in particular

Oxygen pumped into and out of the cavity 104. In this case, the pressure changes, which can be measured by the bending of the membrane 106. In the construction of the device or of the sensor 100 shown by way of example in FIG. 1, the lower electrode 116 has a meandering shape and is simultaneously used as a heater for the membrane 106. In this pumping of gas to the outside, a higher pumping current flow, so that a short regeneration time can be achieved until the start of a next measurement.

The pumping of the gas into the closed chamber 104 via the ion-conducting element 106 leads there to a pressure increase, over the

Pressure measuring element 118 is measured piezoelectric or piezoresistive. When measuring pumping current and pressure, the gas concentration is measured. In an advantageous mode of operation of the sensor 100, the gas is first pumped into the chamber 104 and then out of the chamber 104, and both processes are measured. This allows the function of the complete

Sensors 100 are monitored in the sense of a self-test. Alternatively, it is also possible to pump gas into the cavity 104 with a small current that is difficult to measure, even over a relatively long period of time, which is precisely defined or measured, gas which is present only in a low concentration in the outer space 108. In this case, the gas accumulates in the chamber 104 until with the pressure sensor 118, the amount of gas pumped into the chamber 104 can be determined with sufficient accuracy. Before a new measurement process, the gas in the interior 104 is then pumped outward again, this process with an integration of the pumping current, so the flow of pumped pump, provides additional information about the amount of gas previously accumulated in the chamber 104.

In the concept of an exhaust gas sensor proposed herein, only the ionic conductive material needs to be brought to a high temperature. Since the ion-conducting properties are needed only on the membrane 106 or parts thereof, a very low-power heating can be realized. In the case of the partially heated sensor 100 or the partially heated thin-film membrane 106, the power consumption is drastically lower, in particular compared to conventional ceramic exhaust gas sensors. The rest

Sensor element 100 may be operated at ambient temperature or at a constant but only slightly above ambient temperature, e.g. B. on the heat dissipation from the heated membrane 106 or via a second heater. The heating in the membrane 106 can also determine the presence of gas in the chamber 104 and possibly also on the basis of different behavior with temperature changes of its composition. In the presence of gas in the chamber 104 takes place when heated by the membrane 106, a pressure increase, which can be measured with the sensor element 118. As a result of the heating, a function check or integrity check of the sensor 100 can be carried out at the same time. A defined increase in temperature must be at a defined, possibly previously determined via a calibration,

Pressure increase lead. In the embodiment of the device 100 shown in FIG

Heater for the membrane 106 used simultaneously as the lower electrode 116. This is here by the execution of the second electrically conductive layer 116 as a gas-permeable noble metal layer, for. B. of Pt or of a Pt-Rh alloy achieved. The heatable second electrically conductive layer 116 is structured in a meandering shape and has the two electrical

Connections 127, 132. Thus, the layer 116 can be used either for heating by connecting to the two terminals 127, 132 a

different potential is applied, or as an electrode by applying the same potential to both terminals 127, 132. For pumping purposes, this metal layer 116 can be made very low, so that the applied Heating voltage is very small and compared to the counterelectrode formed here by the first electrically conductive layer 114 has a nearly constant potential. As a result, only slight charging or polarization effects are formed in the membrane 130 on the side 112, which leads to a smaller influence on the measuring accuracy.

In the operating mode of heating the membrane 106 by a

Pulse width modulation method may be applied in the off-phase, a potential to the lower electrode 116 or a voltage applied to the lower electrode 116 potential can be measured. Advantageously, during the voltage application of the heater 116, all electrodes which are connected to the heated, ion-conducting layer 106, are switched to high impedance, in order to avoid charging or Polarrisationseffekte through potential differences to the heater 116 down.

According to alternative embodiments, the second electrically conductive layer 116 may be used exclusively as an electrode and a separate heater for heating the membrane 106 may be installed.

Fig. 2 shows a plan view of another embodiment of the

Device 100 for detecting a parameter of a gas. As the

2, the substrate 102 of the exemplary embodiment shown in FIG. 2 has four cavities 104 which are formed in the substrate 102 in a square and uniformly spaced from one another. Each of the four cavities 104 is in turn covered by a first electrically conductive layer 114 and a second electrically conductive layer 116 having at least partially ion-conducting membrane 106. A construction of each portion 104 of the device 100 having a cavity corresponds to that of the single-cavity embodiment shown in FIG. 1 and also comprises the same elements, with the difference that in the exemplary sensor 100 shown in FIG Assigned plurality of four here again designed as strain gauges pressure measuring elements 118. Each of the four regions 104 of the device 100 having a cavity 104 forms, as it were, one of four identical sensor elements 200 of the sensor 100. As shown in Fig. 2, for each cavity 104 having portion of the sensor 100 centered on each of the four sides of the rectangular cavity 104 each have a pressure sensing element 118 at a junction between the membrane 106 and the insulating layer 122 of the substrate 102 and spaced from the respective electrically conductive layer 114. According to this arrangement, two strain gauges 118 arranged on opposite sides of the cavity 104 each have a common detection direction 202 marked by a directional arrow, which is transverse to a further common detection direction 204 of the other two on opposite sides of the cavity 104 marked by a directional arrow arranged strain gauge 118 extends.

The sensor 100, as shown by way of example in FIG. 2, is suitable for use for the compensation of pressure fluctuations and for integrating measurements. This is realized by, for example, a first of

Sensor elements 200 z. B. measures only the ambient pressure, a second or a second and third of the sensor elements 200 offset by pumping time, but overlapping, measures the gas concentration or measure and a fourth of the sensor elements 200 is pumped empty. Ideally, the function of the sensor elements 200 will rotate after a certain time. In case of failure of one of the elements 200 can advantageously be further evaluated in an emergency operation.

In order to increase the accuracy, and to fluctuations in the pressure of the

Can compensate for outdoor space 108, according to embodiments of one of the four sensor elements 200 or another sensor element can be used as a reference pressure sensor without pumping function. It can also have multiple or all of the sensor elements 200 have the same functionality in time-shifted operation, wherein z. B. a first of the sensor elements 200 gas in its chamber 104 pumps, a second of the sensor elements 200 is pumped empty in this time and a third of the sensor elements 200 as

Reference element for the fluctuating pressure in the outer space 108 is used. According to further embodiments, by means of further - not shown in the figures - measuring elements at least the temperature and also an exhaust gas mass flow can be measured in order to be able to infer the actual flow mass of the exhaust gas and thus the gas concentration.

By exemplarily presented in Fig. 2 combination of several individual sensors or sensor elements 200 in the device 100, the accuracy of a measurement by mutual adjustment of the individual elements 200 z. Example, a pumping method for pumping gas through the membranes 106 and a pressure measuring method by means of the pressure measuring elements 118 can be increased. Due to the redundancy of the sensor elements 200 increases the reliability of the example used in the onboard diagnostics of a vehicle sensor 100. To a further increase in accuracy can also at least temporarily and or during a calibration some elements in a same mode (eg pure pressure measurement or pumps up to a certain pressure) so as to each time calibration parameters for each

Mode and for each sensor element relative to the other elements to determine and store in a memory of an evaluation device 302 (see FIG. 3). In a later use can to control the

Functionality in turn deviations of the sensor elements to each other are detected and in an impermissible extent of the deviations, an evaluation unit can respond appropriately, for. to issue a warning.

The illustrated in Fig. 2 exemplified redundant design of the device 100 with a plurality of smaller chambers 104 and sensors 200 offers in addition to the above-mentioned advantage that the individual elements 200 are operated alternately in regular operation, the possibility for a functional test of the sensor 100 the To be able to operate sensor elements 200 temporarily simultaneously. The function check can take place by comparing the measurement results of the individual sensors 200 after the simultaneous operation. In order to reduce mechanical stress on the membrane 106 even after a very low internal pressure of one or all of the sensor elements 200 after emptying, stop elements for restricting the movement of the membrane 106 are also arranged in the cavities 104 in the embodiment 100 of the device 100 shown in FIG not visible in the illustration in FIG. 2). 3 shows a basic block diagram of an exemplary measurement system 300 for determining a parameter of a gas. The measuring system 300 comprises an exemplary embodiment of the device 100 explained with reference to FIG. 1 as well as an evaluation device 302 coupled to the device 100 and is used in a vehicle 304 for determining a noxious gas concentration in an exhaust gas 306 of the vehicle 304.

The vehicle 304 may be a road-bound vehicle such as a passenger car or a truck. About a line system 308 of the vehicle 304 is a partial flow of the gas or

Deduced exhaust gas 306 and passed to the measuring system 300 in order to pressurize the sensor 100 with the gas 306. Depending on the design of the measuring system 300, the evaluation device 302 is coupled to the first layer of an electrically conductive material and / or the second layer of an electrically conductive material and / or the pressure measuring element of the device 100 (not explicitly shown in the illustration in FIG. 3) and designed to determine the pollutant gas concentration in the exhaust gas 306 based on at least one electrical potential of the first layer and / or the second layer and / or based on the gas pressure detected in the cavity of the device 100 by the pressure measuring element. The measuring system 300 can be located at any position in the

Vehicle 304, for example, also far away from an engine compartment 310 of the vehicle 304th

The device 100 illustrated in FIGS. 1 to 3 may be a miniaturized combined gas and gas turbine based on MEMS technology

Pressure sensor act. A production of the sensor 100 presented here takes place according to embodiments via a modified

Pressure sensor manufacturing process. In the sensor manufacturing can under

Use of an APSM process, the release of the formed porous material cavity 104 already during the application of the ion-conducting material 106 and a subsequent annealing carried out, in particular if for the application or annealing of the ion-conducting material 106 such. B. YSZ high temperature method can be used, for. B. Pulsed laser deposition with deposition temperatures of eg 800 ° C or subsequent annealing with similar or even higher temperatures. 4 shows a flowchart of one embodiment of a method 400 for operating a device for detecting a parameter of a gas. The method 400 may be carried out to operate a sensor as presented with reference to FIGS. 1 to 3 discussed above.

In a step 402, an electrical voltage is applied between a first layer and a second layer of electrically conductive material of the sensor to move gas through an ion-conducting membrane arranged between the first and the second layer from an outer space into a cavity of the sensor arranged below the membrane to pump. In a step 404, an electrical variable is detected at the first layer and / or the second layer and / or at a pressure measuring element of the sensor arranged on the membrane in order to detect the parameter of the gas. In a step 406, the voltage is again applied between the first layer and the second layer to pump the gas through the membrane from the cavity into the outer space. This is followed by a step 408 of re-detecting the electrical quantity at the first layer and / or the second layer and / or at the first layer

Pressure measuring element to recapture the parameter of the gas.

According to one embodiment, the method 400 may be implemented as a

Pulse width modulation method are executed. In this case, the step 402 of the application of the electrical voltage or the step 406 of the renewed application of the electrical voltage alternately with a step of

Applying an electrical voltage across the first layer or the second layer to heat the membrane are performed.

An ion-conducting material-based pressure sensor-sensor combination constructed according to the concept presented here is suitable for a

Use as a chemical gas sensor, in particular as an exhaust gas sensor for motor vehicles, and for stationary applications. A

Main application option is a lambda probe,

optionally with an alternative structure, also for detecting additional exhaust gas components such as nitrogen oxides. The embodiments described and shown in the figures are chosen only by way of example. Different embodiments may be combined together or in relation to individual features. Also, an embodiment can be supplemented by features of another embodiment.

Furthermore, the method steps presented here can be repeated as well as executed in a sequence other than that described.

If an exemplary embodiment comprises an "and / or" link between a first feature and a second feature, then this is to be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment either only first feature or only the second feature.

Claims

claims

An apparatus (100) for detecting a parameter of a gas (306), the apparatus (100) comprising: at least one cavity (104) for receiving the gas (306) from an exterior space (108); at least one membrane (106) for separating the cavity (104) from the outer space (108), wherein a first side (110) of the membrane (106) facing the outer space (108) has a first layer (114) of an electrically conductive material and a second side (112) of the membrane (106) facing the first side (110) facing the cavity (104) has a second layer (116) of an electrically conductive material, and wherein at least a portion of the membrane (106) is an ion-conducting Material has; and at least one disposed on or in the membrane (106)

Pressure measuring element (118) for detecting a gas pressure in the cavity (104), in particular wherein the pressure measuring element (118) may also include a temperature measuring device.

2. Device (100) according to claim 1, characterized in that the first layer (114), the membrane (106) and the second layer (116) are formed to at one between the first layer (114) and the second layer (116) voltage applied to pump the gas (306) through the membrane (106) and / or are adapted to a voltage between the first layer (114) during diffusion of the gas (306) through the membrane (106). and the second layer (116). Device (100) according to one of the preceding claims, characterized in that the first layer (114) and / or the second layer (116) has a first electrical contact terminal (127) and a second electrical contact terminal (132) and is designed to heating at least a portion (130) of the membrane (106) based on an electrical current flow between the first electrical contact terminal (127) and the second electrical contact terminal (132).

Device (100) according to claim 3, characterized in that the pressure-measuring element (118) is arranged outside the section (130) to be heated of the membrane (106).

Device (100) according to one of the preceding claims, characterized in that the first layer (114) and / or the second layer (116) is arranged meander-shaped.

Device (100) according to one of the preceding claims, characterized in that the device (100) a

Stop element (128) for limiting a deflection of the membrane (106), in particular wherein the stop element (128) on a bottom (124) of the cavity (104) is arranged.

Device (100) according to one of the preceding claims, characterized in that the device (100) has at least one second pressure measuring element (118) which is disposed at a further position deviating from a position of the pressure measuring element (118) on the membrane (106) in particular wherein a detection direction of the pressure measuring element (118) extends from a detection direction of the further pressure measuring element (118).

different.

Device (100) according to one of the preceding claims, characterized in that the device (100) at least one further cavity (104) for receiving the gas (306) from the Outside space (108), at least one further membrane (106) for separating the further cavity (104) relative to the outer space (108) and at least one further arranged on the membrane (106)

Pressure measuring element (118) for detecting a gas pressure in the further cavity (104), wherein a the outer space (108) facing the first side of the further membrane (106) has a further first layer (114) and one of the further cavity (104) facing in that the second side of the further membrane (106) opposite the first side has a further second layer, and wherein at least a portion of the further membrane (106) comprises the ion-conducting material.

A measurement system (300) for determining a parameter of a gas (306), the measurement system (300) comprising: the device (100) according to any one of the preceding claims; and an evaluation device (302), wherein the evaluation device (302) is coupled to the first layer (114) and / or the second layer (116) and / or the pressure measuring element (118) and is designed to be based on at least one electrical potential the first layer (114) and / or the second layer (116) and / or based on the gas pressure in the cavity (104) detected by the pressure measuring element (118) to determine the parameter of the gas (306).

A method (400) for operating a device (100) for detecting a parameter of a gas (306), the device (100) comprising at least one cavity (104) for receiving the gas (306) from an exterior space (108), at least one membrane (106) for separating the cavity (104) from the outer space (108), wherein a first side (110) of the membrane (106) facing the outer space (108) has a first layer (114) and faces the cavity (104) in that the second side (112) of the membrane (106) has a second layer (116) opposite the first side (110), and at least a portion of the membrane (106) comprises an ion-conducting material, and at least one comprising pressure measuring element (118) arranged on the membrane (106) for detecting a gas pressure in the cavity (104), and wherein the method (400) comprises the following steps:

Applying (402) an electrical voltage between the first layer (114) and the second layer (116) to pass the gas (306) through

Pump diaphragm (106) from the exterior space (108) into the cavity (104); and

Detecting (404) an electrical quantity at least at the first layer (114) and / or the second layer (116) and / or at the

Pressure sensing element (118) to detect the parameter of the gas (306).

The method (400) according to claim 10, characterized in that the method (400) further comprises a step of re-applying (406) the electrical voltage between the first layer (114) and the second layer (116) to remove the gas (306 ) through the membrane (106) from the cavity (104) into the outer space (108), and a step of re-detecting (408) the electrical quantity at least at the first layer (114) and / or the second layer (116 ) and / or at the pressure sensing element (118) to recapture the parameter of the gas (306).

Method (400) according to claim 10 or 11, characterized

characterized in that the method (400) for operating the device (100) is implemented as a pulse width modulation method, wherein the step of applying (400) the electrical voltage between the first layer (114) and the second layer (116)

alternating with a step of applying an electric

Voltage is applied across the first layer (114) or the second layer (116) to heat the portion (130) of the membrane (106).

Apparatus (100) adapted to perform all the steps of a method (400) according to any one of the preceding claims. Computer program adapted to perform all the steps of a method (400) according to one of the preceding claims.

A machine-readable storage medium having a computer program stored thereon according to claim 14.