DE102006058425A1 - Motor exhaust gas return to the air intake has a hot film anemometer with separate heat and temperature measurement resistance layers - Google Patents

Abstract

The exhaust gas return flow from the outlet (4) at a motor (1), to the motor air intake (2), gives an air/exhaust gas intake mixture. A controlled valve (5) is in the return flow, together with an exhaust gas cooling unit (8) and a hot film anemometer (10). The anemometer has a heat resistance and a temperature measurement resistance as separate resistance layers mounted on ceramic carriers.

Description

The The present invention relates to exhaust gas recirculation with a hot film anemometer.

DE 199 59 854 describes an exhaust gas recirculation, in which the incoming air is measured with a flow mass sensor according to the anemometric principle and for measuring the amount of exhaust gas, a second flow mass sensor is arranged in the exhaust duct after a water cooling.

The anemometric measuring principle of a flow rate sensor is from the DE 195 06 231 known.

DE 103 05 694 discloses a flow mass sensor for exhaust gas measurements in which the chip parts are made of thin metal foils. These sensors are susceptible to interference and may not deliver reproducible results.

It The object of the present invention is the susceptibility of exhaust gas recirculation minimize and maximize sensitivity.

The solution The object is achieved with the independent claims. The dependent claims are preferred versions.

Out the exhaust gas exiting the machine is fed to a hot-film anemometer, wherein from the determined flow rates of recirculated exhaust gas and possibly aspirated air, an actual value signal (X, X1, X2) formed and with a setpoint signal (w) for an optimal operating point the machine is compared, with a control deviation of the actual value signal to a Actuating signal leads, which engages with the aid of an actuator in the exhaust gas recirculation.

decisive is that the measurement of the flow masses neither in a water-cooled Area, still after a water-cooled area is done. According to the invention Hot film anemometer in front of the radiator arranged or inside an air cooled cooler.

According to the invention needs the flow rate be no longer determined by sucked air.

With the determined parameters of the vehicle internal combustion engine an optimization of engine operation with regard to low environmental impact and achieved efficiency, taking the parameters in a very simple way be determined.

Out the exhaust gas exiting the machine is fed to a hot-film anemometer, wherein from the determined flow rates of recirculated exhaust gas and possibly aspirated air, an actual value signal (X, X1, X2) formed and with a setpoint signal (w) for an optimal operating point the machine is compared, with a control deviation of the actual value signal to a Actuating signal leads, which engages with the aid of an actuator in the exhaust gas recirculation.

In An advantageous embodiment of the method is from the machine exiting exhaust gas from combustion products cleaned. Farther is especially for larger engines (e.g., for Truck) a cooling off of the exhaust gas - preferably to a temperature in the range of 70 ° C to 300 ° C - provided.

With Help of a control signal (Y, Y1) is at least one actuator triggered in the exhaust gas recirculation, the is preferably designed as a controllable valve.

In A preferred embodiment of the method is the setpoint signal (W) from a power demand signal (e.g., accelerator) and at least derived from a parameter of the machine. As a parameter has changed a signal proven, from the exhaust gas temperature or the speed as well as the mass of the recirculated exhaust gas is formed. At least one signal is used as machine parameter compared with a reference signal by difference value formation, being the crossing a predetermined difference value to a control signal (Y, Y1, Y2) leads.

While the Control signals Y, Y1 - preferably by means of controllable valve - directly intervene in the exhaust gas recirculation, Actuating signal Y2 acts on an actuator located in the inlet area the internal combustion engine is located in the a mixture of inflowing air and partially recirculated exhaust gas flows.

Preferably Actuator Y2 acts on a compressor in the inlet area of the Internal combustion engine, wherein with the aid of control signal Y2 the setting of blade angles according to the principle the variable blade geometry in compressors "is made.

It but it is also possible Actuating signal Y2 to act on a valve assembly.

Preferably The signals are converted into digital signals by means of an A / D converter and saved, followed by a comparison of the stored values with digital reference values carried out becomes.

In a preferred embodiment of the method, in the hot-film anemometer, at least two heating resistors maintained at a constant temperature are flowed one after another for measuring the flow mass of the exhaust gas; In this case, the heating resistors are each traversed by an adjustable current (I ₁ , I ₂ ), wherein from the strength of the currents (I ₁ , I ₂ ) a signal for the flow mass and its direction is formed.

Furthermore, in an advantageous embodiment of the method of at least one pulsating current I ₁ , I ₂ by alternating multiplication of the current amplitude with +1 and -1 and a subsequent difference value formation of the resulting flow of the mass flow determined.

at a device for (partial) exhaust gas recirculation from an exit region a vehicle internal combustion engine in an air inlet area, in which a controllable by means of control mixture of exhaust gas and inflowing Air can be fed to the machine is, according to the invention for determination the mass of recirculated exhaust gas Air a hot film anemometer in the exhaust gas recirculation channel before cooling or in an air-cooled one cooler arranged.

Of the Exit area is over a flow channel for the Exhaust gas recirculation, the a controllable valve as actuator and the hot-film anemometer has, connected to an inlet region of the internal combustion engine.

In order to is a fuel quantity depending from the mass airflow rate taking into account a power demand signal adjustable.

In a first preferred embodiment of the device, the Hot film anemometer at least one measuring resistor and at least one heating resistor on, with the resistors each formed in microsystem technology. advantageously, are the resistances as a thin film or thick-film element on the metrological basis of platinum or platinum group metal formed.

Of the Heating resistor or the heating resistors are for operation in the temperature range from 500 to 750 ° C intended.

A mass flow sensor with a measuring resistor short response time and a fast micro heater, for example, from EP 0 964 230 A2 known.

In a second advantageous embodiment of the invention, the Hot film anemometer at least two fast micro heaters or heating resistors, at well-defined solid overtemperatures e.g. 450 ° C and 550 ° C operated become. The temperatures are chosen to be more suitable Soot through pyrolysis is always burned and the micro heaters always remain clean. Fast control electronics feed the heaters by means of electricity, that their temperatures are kept constant. The evaluation the heating currents leaves one clear inference to both the mass flow and the mass temperature. By using platinum heating elements that can be used in both thick and also produced in thin-film technology could be, can be made by taking advantage of the well-defined resistance-temperature characteristic of Platinum heating temperatures of 500 ° C up to 750 ° C to adjust.

One significant advantage of the second embodiment (two heating resistors) is to be seen in the fact that practically no sooting occurs on the heating resistors, so that they are always operated with optimum measuring characteristics.

The Heating or measuring resistors are advantageously in at least two tracks on a plate-shaped membrane - preferably made of an electrically insulating and heat-resistant material such as Ceramic - formed.

In inventive development become hot-film anemometer for mass production suitably arranged and for mass production suitable hot-film anemometer for exhaust gas recirculation provided, which still counteract the drift, in particular self-cleaning hot-film anemometer or functionally stable heavy soils, such as Exhaust gas, suspendable Flow sensor elements.

One authoritative Aspect for The present invention is a self-cleaning of the temperature sensing element by annealing by means of a heating conductor. In particular, this heating element is on integrated on the chip side of the temperature measuring element. In a preferred execution At least two platinum thin-film resistors will be on a ceramic carrier plate arranged. this makes possible a heating of the temperature measuring element for heating or annealing of Impurities.

Especially are the two resistors the temperature measuring element arranged on a ceramic substrate, preferably on a massive ceramic tile.

When ceramic components of a multi-part ceramic component next to the carrier part, the preferably already assembled as a laminate, nor the temperature measuring element and to consider the heating element. Very particularly preferred is the carrier part formed as a lid or as a side or surface of a Hollow body, in particular its front side. Instead of a ceramic support, the resistors also arranged on a ceramic substrate on an alternative support be.

It is advantageous if the temperature measuring element rectangular ceramic Carrier plate with has two long and two narrow edges and that the ceramic Carrier plate in the Area of one of the narrow edges between ceramic films of the ceramic film laminate or arranged between at least two parts of the ceramic component are.

As well it is advantageous if the at least one heating element rectangular ceramic carrier plates with has two long and two narrow edges and that the ceramic Carrier plate in the Area of one of the narrow edges between ceramic films of the ceramic film laminate or arranged between at least two parts of the ceramic component is.

All particularly preferably, the temperature measuring element or the at least a heating element a rectangular ceramic carrier plate with two long and two narrow edges on which the ceramic carrier plates in openings a lid or a hollow body end face are arranged.

The Platinum thin film resistors preferably facing away from the ceramic film laminate or the ceramic components Arranged at the end of the carrier plates, one as possible low thermal influence of the platinum thin film resistors that is thermally inert Ceramic film laminate or to ensure the thermally inert ceramic components.

Around a mutual influence of temperature measuring element and heating element To prevent, it is advantageous if the platinum thin-film resistor of the heating element farther from the ceramic film laminate or ceramic component is arranged as the platinum thin-film resistor of the temperature sensing element. As a result, the platinum thin film resistors of Heating element not in the same flow fiber of the medium arranged like the platinum thin film resistors of the Temperature measurement element.

According to the invention becomes special preferably also provides an anemometric measuring device, at the film resistors in a lid or a hollow body in an opening or in openings of the Lids or hollow body are attached, with two resistors by one to three orders of magnitude are different.

• 1. Heizwiderstände zur Selbstreinigung des Temperatursensors als Bestandteil des Temperatursensors.
• 2. Heizwiderstände als Heizleistungssensoren zur Ermittlung eines Masseflusses nach dem anemometrischen Prinzip.

The one to three orders of magnitude greater resistance is suitable as a temperature measuring resistor and is referred to below as such. The smaller by one to three orders of magnitude compared to the temperature measuring resistors are suitable for heating. With regard to these heating resistors, a distinction is made in the context of the present invention between different functions:

• 1. Heating resistors for self-cleaning of the temperature sensor as part of the temperature sensor.
• 2. Heating resistors as heating power sensors for determining a mass flow according to the anemometric principle.

Heating power sensors with two heating conductors allow the determination of the direction of the mass flow. Heat output sensors with an additional temperature measuring resistor allow a precise temperature Adjusting the temperature of the heating power sensor. The present invention relates in this case exclusively to sheet resistors which are designed as a thick layer or thin layer, preferably in platinum, in particular as a platinum thin layer. The film resistors are arranged on a substrate, in particular on a ceramic substrate. You can run the ceramic substrate as a carrier or arrange on a support, such as a metal plate. In the terminology, film resistors applied to a carrier material are also referred to as film resistors, so that there is no linguistic distinction between film resistors in the narrower sense than the pure resistive film and film resistors, including the carrier material. The sheet resistors inserted in openings of a lid or hollow body comprise the substrate on which the thin or thick layer is arranged as a resistance layer.

In preferred embodiment are the film resistors arranged in the narrower sense on a ceramic underground. Various film resistors in the broader sense next to each other in an opening a lid or hollow body be arranged or separately in each case an opening. Preferably, heating power sensors and temperature sensors are different from each other spaced. Two heating conductors of a heating power sensor are preferred arranged one behind the other so that they are in the flow direction lie one behind the other. Preferably, heating power sensors with two heating conductors on a common underground or with two successively arranged, identical chips executed.

The openings the lid or hollow body are expediently Slots or holes.

Of the Lid is provided for sealing a pipe. Is the Lid made of metal, it can be welded to a metal tube. The film resistors in a broader sense are through the opening or the openings led the lid and in the opening or in the openings attached to the lid. The hollow body serves to accommodate the connections the sheet resistances, their sensitive part through the opening or the openings from the hollow body protrudes.

One authoritative Aspect of the present invention is that in thick or thin layer generated resistances to be easily installed in an exhaust duct in mass production Sensor element to be integrated. The solution according to the invention, sheet resistors in one Lid or hollow body to plug a simple seal of the lid or hollow body both in terms of support material the resistances as well as the material of the exhaust duct.

According to the invention is characterized ensures that the film resistances perpendicular to the base of a Lids or hollow body executable are. This results in production advantages over one continued in parallel to a plate Arrangement. The invention is not limited to a vertical design, but allows any angle to the surface the lid or hollow body. When An essential inventive advantage is the vertical component angles according to the present invention executable. Accordingly, the advantage of the present invention is particularly remarkable at angles of 60 to 90 degrees, in particular from 80 to 90 degrees on.

• • ist der Hohlkörper einseitig offen, insbesondere als einseitig verschlossenes Rohr ausgebildet;
• • ist der Deckel als Scheibe ausgebildet;
• • ist die Grundfläche einer Öffnung zur Aufnahme mindestens zweier Schichtwiderstände mindestens um eine Größenordnung kleiner als die Deckelgrundfläche oder eine entsprechende Hohlkörpergrundfläche;
• • weist der Deckel oder der Hohlkörper zwei Öffnungen zur Aufnahme von Schichtwiderständen auf;
• • besteht der Deckel aus keramischem Material;
• • sind die auf keramischem Trägermaterial gehaltenen Schichtwiderstände in der Öffnung eines keramischen Deckels, insbesondere einer keramischen Scheibe mit Glaslot befestigt;
• • sind die auf einem keramischen Substrat getragenen Schichtwiderstände in wenigstens einer Öffnung eines Metalldeckels oder Hohlkörpers, insbesondere einer auf einem Metallrohr geschweißten Metallscheibe mit Verguss oder Glas befestigt;
• • liegen die beiden Widerstände des Temperaturmesselements in einer Ebene;
• • rahmt der kleinere Widerstand (Heizer 202d) den größeren Widerstand (202a zur Temperaturmessung) ein.

In preferred embodiments

• • The hollow body is open on one side, in particular designed as a tube closed on one side;
• • The lid is designed as a disc;
• The base area of an opening for receiving at least two sheet resistances is at least one order of magnitude smaller than the cover base area or a corresponding hollow body base area;
• • The lid or the hollow body has two openings for receiving sheet resistors;
• • the lid is made of ceramic material;
• • held on ceramic substrate sheet resistors are mounted in the opening of a ceramic lid, in particular a ceramic disc with glass solder;
• The sheet resistors carried on a ceramic substrate are fastened in at least one opening of a metal cover or hollow body, in particular a metal disc with casting or glass welded to a metal tube;
• • are the two resistors of the temperature measuring element in one plane;
• • framed the smaller resistance (heater 202d ) the greater resistance ( 202a for temperature measurement).

The Measuring device according to the invention is suitable for flow sensors or soot sensors.

The hot-film anemometer is operated with the heating power resistor and the temperature sensor according to the anemometric principle. According to the invention, the temperature sensor is part of an anemo metric measuring device equipped with another heating conductor. As a result, a cleaning of the temperature sensor is made possible by annealing by means of heaters. It has proven useful in the anemometric measuring device to decouple the temperature sensor and the heating power sensor to be differentiated from the heater of the temperature sensor, preferably to space it, in particular to insert it in separate openings of the lid or hollow body. The temperature sensor has a much higher resistance than the heaters, typically one to three orders of magnitude higher. With the temperature sensor, the influence of the temperature of the exhaust gas on the determination of the flow mass can be corrected.

from Temperature sensor to distinguish is an optionally on the Heizleistungssensor arranged temperature measuring resistor, with the the temperature of the heating element is particularly accurate adjustable. One finished temperature measuring resistor is in contrast to the temperature sensor not for the measurement of the fluid temperature provided, since it during the Operation of the heating power sensor only for its temperature control suitable is.

Of the Heating power sensor and the temperature sensor preferably have both each have a heating conductor and a Temperaturmeßwiderstand on. Are heating power sensor and temperature sensor identical to yours functional determination determined by the electrical system.

It has proved its worth, the carriers platinum thin film resistors as to form thin platelets, so that is a very small thermal inertia of the system and thus a high response speed of the platinum thin-film resistors results. The formation of a ceramic composite can be sintered ceramic films are used, which then preferably glued to a glass solder become. The structure of the hot-film anemometer used materials can excellent for use in temperatures ranging from -40 ° C to + 800 ° C.

It is particularly preferred if the ceramic carrier platelets have a thickness in the range of 100 microns to 650 microns, in particular 150 microns to 400 microns. Al ₂ O _{3 has} proved to be suitable as the material for the ceramic carrier platelets, in particular with at least 96% by weight and preferably more than 99% by weight.

For the platinum thin film resistors has it is proven if these each have a thickness in the range of 0.5 microns to 2 microns, in particular 0.8 μm to 1.4 μm. heating resistors preferably have 1 to 50 ohms and tend to decrease of the components to low values. In the currently common dimensions of the components are preferred 5 to 20 ohms. Point temperature measuring resistors preferably 50 to 10,000 ohms and tend to diminish the components too low values. In the currently common dimensions The components are preferably 100 to 2,000 ohms. On the temperature chip the temperature measuring resistor is many times larger than the heating resistor. In particular, these resistances differ by one up to two orders of magnitude.

In order to protect the platinum thin-film resistors against a corrosive attack by the measuring medium, it has proven useful if these are each covered with a passivation layer. The passivation layer preferably has a thickness in the range from 10 μm to 30 μm, in particular from 15 μm to 20 μm. A passivation layer comprising at least two different individual layers, in particular individual layers of Al ₂ O ₃ and glass ceramic, has proven particularly useful. The thin-film technique is suitable for creating the preferred layer thickness of the Al ₂ O ₃ layer of 0.5 μm to 5 μm, in particular 1 μm to 3 μm.

The Platinum thin film resistors are preferably arranged on the end facing away from the cover or hollow body end of the carrier plates, one as possible low thermal influence of the platinum thin film resistors the thermally inert Lid or hollow body to ensure.

Around a mutual influence of temperature measuring element and heating element To prevent, it is advantageous if the platinum thin-film resistor of the heating element is arranged further away from the cover or hollow body as the platinum thin film resistor of the temperature measurement element. As a result, the platinum thin-film resistors of the Heating element not in the same flow fiber of the medium arranged like the platinum thin film resistors of the Temperature measurement element.

The preferred arrangement of the temperature measuring element is in the flow direction in front of the heating element.

Preferably are the carrier plates of the Heating element and the temperature measuring element spaced apart, and in particular parallel to each other.

It has especially for the measurement of media with changing flow direction proven, if two heating elements and a temperature measuring element or two temperature measuring elements and a heating element are arranged in a row.

It has proved its worth, the carrier plates of the Heating element and the temperature measuring element in the lid or hollow body spaced to arrange one another and parallel to each other.

With the hot-film anemometer according to the invention becomes a mass flow measurement of gaseous or liquid media in piping, especially when the carrier platelets in the flow direction of the medium are arranged.

Preferably are the carrier plates of the Heating element and the temperature measuring element spaced from each other in particular in series between the same ceramic films or Parts of the ceramic component arranged.

there has it proven when the ceramic film laminate is formed of two ceramic sheets or if the ceramic component consists of two ceramic tubes whose walls in cross-section each having a half-moon profile is formed.

It has especially for the measurement of media with changing flow direction proven, if a temperature measuring element, two heating elements and a temperature measuring element arranged in series.

Farther have arrangements proven, in which the ceramic film laminate formed from three ceramic films is.

there has it proven in particular if the carrier plates of the Heating element and the temperature measuring element by ceramic films spaced from each other and arranged parallel to each other.

It is preferred, a heating element between a first and a second Ceramic foil and a temperature measuring element between the second and a third ceramic foil of the three ceramic sheets, wherein the heating element and the temperature measuring element at the same height of the ceramic film laminate are arranged side by side.

Besides, has it is proven when a heating element between a first and a second ceramic foil the three ceramic sheets is arranged and that two temperature measuring elements between the second and a third ceramic foil of the three ceramic foils are arranged, wherein the heating element between the temperature measuring elements is arranged.

Farther have arrangements proven, in which the ceramic film laminate formed of four ceramic films is.

there it is preferred if a first temperature measuring element between a first and a second ceramic film of the four ceramic films and a second temperature sensing element between a third and a fourth ceramic foil of the four ceramic films is arranged and that a heating element between the second and the third ceramic foil is arranged, wherein the heating element and the temperature sensing elements on same height of ceramic foil laminate are arranged side by side.

Farther it is preferred if a first temperature measuring element between a first and a second ceramic film of the four ceramic films and a second temperature sensing element between a third and a fourth ceramic foil of the four ceramic films is arranged and that a heating element between the second and the third ceramic foil is arranged, wherein the temperature measuring elements at the same height of the ceramic film laminate are arranged side by side and the heating element offset from the Temperature measuring elements is arranged.

The Use of a hot-film anemometer according to the invention for mass flow measurement gaseous or more fluid Media through pipelines, wherein the carrier plates parallel to the flow direction of the medium are ideal.

In this case, the hot-film anemometer according to the invention is particularly suitable for measuring on gas shaped media having a temperature in the range of -40 ° C to + 800 ° C, as it has, for example, the exhaust gas of an internal combustion engine.

The Self-cleaning by heating the temperature measuring element is special for im Exhaust range of internal combustion engines, especially diesel engines arranged sensors suitable. Sooty sensors will heat up, especially annealing quickly fully functional again. Leave it this self-cleaning during Repeat the life of a motor as often as you like.

The Arrangement of several temperature measuring elements and heating elements allows on the support element in Ideally, the detection of the flow direction or of flow direction changes a medium. In this respect, it is advantageous to use the hot-film anemometer according to the invention for measuring on media with temporally changing flow direction use.

The object of the invention is described below with reference to 1a to 16 explained in more detail.

1a schematically shows the structure of a control circuit for an internal combustion engine with exhaust gas recirculation;

1b shows in the diagram a function of the number of combustion products V in g / km in dependence on the exhaust gas recirculation rate R;

1c For a better illustration of the optimization process - as discussed for example at the 16th Vienna Motor Symposium from 4 to 5 May 1995 - is a diagram of relative changes in the emission of hydrocarbons (HC), particulates and nitrogen oxides (NOx) depending on the Exhaust agitation rate;

2 schematically illustrates the structure of a control loop for two controlled variables;

3a shows the hot-film anemometer for exhaust gas recirculation in longitudinal section;

3b represents the actual hot film anemometer;

3c shows in a partial enlargement of the flow channel for the exhaust gas recirculation with the actual measuring element;

4 shows a hot film anemometer with two-layer ceramic film laminate and a temperature measuring element and a heating element (top view of 4a );

4a shows the hot-film anemometer 4 in side view;

5 shows a hot film anemometer with two-layer ceramic film laminate and two temperature sensing elements and two heating elements (top view of 5a );

5a shows the hot-film anemometer 5 in side view;

6 shows a hot film anemometer with two-layer ceramic film laminate and two temperature sensing elements and a double heating element (top view of 6a );

6a shows the hot-film anemometer 16 in side view;

7 shows a hot-film anemometer with three-layer ceramic film laminate, two temperature sensing elements and a double heating element in plan view;

8th shows a hot-film anemometer with three-layer ceramic film laminate, a temperature measuring element and a heating element in plan view;

8a shows the hot-film anemometer 8th in perspective view;

9 shows a hot-film anemometer with three-layer ceramic film laminate, a temperature measuring element and a heating element in plan view;

9a shows the hot-film anemometer 9 in side view;

9b shows the hot-film anemometer 9a in side view;

10 shows a hot-film anemometer with four-layer ceramic film laminate, two temperature sensing elements and a double heating element in plan view;

11 shows a hot-film anemometer with four-layer ceramic film laminate, two temperature sensing elements and a double heating element in plan view;

12 shows a hot-film anemometer with multi-part ceramic component, a temperature measuring element and a heating element in the cross section AA '(see 12a );

12a shows the hot-film anemometer 12 in side view;

13a shows a hot-film anemometer with arranged in a metal plate heating and temperature measuring element;

13b shows a hot-film anemometer with arranged in a ceramic disk heating and temperature measuring element;

14a shows a section according to 4 or 5 concerning an arrangement of sheet resistors in a ceramic disk;

14b shows the clipping according to 6a in plan view;

15 shows a hot-film anemometer with flow direction detection;

16 shows a hot film anemometer with two thermally decoupled heaters.

According to 1a has the internal combustion engine 1 a charged entry area 2 for incoming air and recirculated exhaust gas; Furthermore, on the exhaust side of the machine is an exit area 4 provided, from which a part of the exhaust gas in a flow channel 6 for exhaust gas recirculation is performed, with a controllable valve 5 , an exhaust gas cooling device 8th and a hot-film anemometer 10 is provided. The hot film anemometer 10 measures the amount of recirculated exhaust gas. The controllable valve 5 serves to regulate the exhaust gas partial pressure for the purpose of setting a specific quantity ratio between freshly flowing air and the amount of partially recirculated exhaust gas; the controllable valve 5 is from a regulator 15 controlled by a control signal Y. The flow channel 6 for the exhaust gas recirculation ends in a junction formed as a mixing chamber 12 a fresh air introduction 13 in the entrance area 2 the machine 1 , wherein for measuring incoming fresh air, an additional flow rate sensor 14 is optional.

The in the exit area 4 the machine 1 in the return to the flow channel 6 branched off part of the exhaust gas thus flows through one valve 5 , Cooling device 8th and hot-film anenometer 10 , The recirculated exhaust gas meets in the junction 12 on the incoming air of the fresh air discharge 13 after this possibly the optional mass flow sensor 14 has gone through.

The mixture of inflowing air and exhaust gas is a supercharger with compressor 30 supplied, which is preferably designed as an exhaust gas turbocharger, wherein the associated drive turbine in the outlet region 4 not shown for a better overview.

The non-return part of the exhaust gas passes through a conduit 25 - And possibly a cleaning device - to the outside, wherein the average temperature of the exhaust gas is about 400 ° C to 700 ° C.

Furthermore, in the region of the exhaust gas outlet region 4 a temperature sensor 16 to measure the exhaust gas temperature. The symbolic symbol here 15 gets over lead 21 a signal corresponding to the exhaust gas temperature X1 and via line 23 a signal Z corresponding to that of the optional flow rate sensor 14 measured amount of inflowing fresh air; Since this amount of incoming fresh air is usually not adjustable, this is by the in the control technology for Disturbance variables used symbol Z shown.

Furthermore, the controller via line 24 a setpoint W is supplied to control the exhaust gas temperature signal X, from which is determined by means of the regulator 15 output control signal a specific ratio of the partial currents of possibly via the optional mass flow sensor 14 fresh incoming air mass and the partial return of the over the hot-film anemometer 10 can set adjusted exhaust gas. A particular embodiment of the hot-film anemometer provides the exhaust gas recirculation temperature signal. But also the previous exhaust gas temperature measurement by means of temperature sensor 16 can be provided by mathematical modeling and omitted as a sensor.

In 1b schematically the sum V of the emitted pollutant particles and the nitrogen oxides in g / kg is shown, wherein a function as a function of the return rate R is shown. Based 1b It can be seen that the amount of nitrogen oxides of the curve N decreases with increasing recirculation rate, while the emitted pollutant particles of the curve P increase. In the region of the diagram denoted by point A1, the curve P of the particles and the curve N of the nitrogen oxides intersect in a kind of optimum, so that the Euronorm IV can be met.

According to the diagram in 1b is with the help of the regulator 15 ( 1a ) the control signal Y is formed so that both a minimum particle output according to curve P, as well as a minimum nitrogen oxide output according to curve N is set according to the diagram in which the combustion products V1 are plotted in g / km over the exhaust gas recirculation rate R. The optimum operating point A1 lies at the intersection of the curves P and N, at the coordinate values R1 and V1.

At the in 1a The scheme shown is a simplified embodiment of the scheme, in which only the exhaust gas temperature is supplied as a control variable or feedback signal X to the controller, this variable with a power specification as setpoint W (eg position of an accelerator pedal in the vehicle) is compared and control deviation a control signal Y on the controllable valve 5 acts so that always only so much exhaust gas through the flow channel 6 the exhaust gas recirculation is fed back that the power setpoint of the setpoint W is maintained.

However, it is also possible to use the regulator 15 to be used as so-called two-size controller, for example, the exhaust gas temperature via line 21 as signal X1 and the speed n of the internal combustion engine via line 22 are supplied as signal X2 to the controller, these two variables X1 and X2 according to the explained below 2 be coupled with each other.

Based 1c It can be seen that the hydrocarbons HC in the exhaust gas in the exhaust gas in the region of an exhaust gas recirculation rate R of 15 to 20% increase from approximately 100% to 125% starting from the region of "relative changes" RA, while those marked "P" The exhaust gas oxides located in the exhaust gas NOx, whose curve is denoted by "N", however, are from an initial value of RA at 100% at an exhaust gas recirculation rate of 0% to At a nitrogen oxide value in the range of about 50% at about 10% exhaust gas recirculation rate reduced, with the NOx value can be further reduced at an exhaust gas recirculation rate of 40% to a nitrogen oxide value of about 20%.

Based on the diagram of 1c It can be seen that an optimization of the various parameters of the exhaust gas for an exhaust gas recirculation rate in the range of about 15 to 30% is possible.

The maximum values of Euro Standard IV (exhaust gas) provided for exhaust gases in commercial vehicles with a gross vehicle weight of more than 3.5 t are shown in the following table: Commercial vehicles with a gross vehicle weight ≥ 3.5 t: Previous standard: Euro IV standard CO 4.0 g / kW / h 4.0 g / kW / h HC 1.1 g / kW / h 0 g / kW / h NOx 7.0 g / kW / h 2.0 g / kW / h PM 0.15 g / kW / h 0.08 g / kW / h

According to 2 is a two-size control provided, similar to in 1a the exhaust gas temperature as controlled variable X1 via line 21 the controller 15 is fed and beyond the speed n as controlled variable X2 via line 22 also the regulator 15 is supplied. With a first manipulated variable Y1 is a controllable valve 5 in the exhaust gas recirculation or in the flow channel 6 controlled during control signal Y2 of the controller 15 the angle of attack of the compressor blades in the compressor 30 Adjusted the inlet area, so that an optimal compromise between particle emissions and nitrogen oxide emissions according to 1b Operating point A1 is maintained. The actuating signal Y2 is via line 31 to the compressor 30 guided. It is important that both the recirculated exhaust gas quantity via control signal Y1 and the compressed amount of the incoming exhaust air mixture can be controlled as accurately as possible to the optimum operating point 1b adjust.

3a shows in longitudinal section the hot-film anemometer 10 , wherein in addition electrical connection connector can be seen above the sensor housing shown in longitudinal section. The entrance area is with signs 26 , the exit area with signs 28 Mistake.

In 3b is the hot film anemometer 10 shown enlarged in longitudinal section, wherein in the entrance area 26 a heatable measuring element 27 is recognizable while in the exit area 28 heating element 29 is recognizable.

In 3c is the hot film anemometer 10 in the cutout of the flow channel 6 shown according to the two or more heater principle. In this figure, two heating elements 29a . 29b to recognize as a micro heater. The associated controller is designed as part of the engine control electronics shown in fragmentary form, here with signs 15 ' is provided.

4 shows a hot-film anemometer with a ceramic film laminate 201 made from a first ceramic foil 201 from Al ₂ O ₃ and a second ceramic film 201b is formed from Al ₂ O ₃ . In series between the first ceramic foil 201 and the second ceramic foil 201b are a temperature measuring element 202 and a heating element 203 partially embedded and electrically contacted. It is possible to measure the mass flow according to the principle of the hot-film anemometer. The heating element 203 is thereby by an electrical control circuit (bridge circuit and amplifier in a control loop) either at a constant temperature (eg of 450 ° C) or a constant temperature difference (eg of 100 K) to the temperature measuring element 202 held. A change in the mass flow of the medium now causes a change in the power consumption of the heating element 203 which is electronically evaluable and directly related to the mass flow.

4a shows the hot-film anemometer 4 in side view. It can be seen that the temperature measuring element 202 and the heating element 203 via electrical conductors 204a . 204b . 204c . 204d . 205a . 205b with connection surfaces 204a . 204b ' . 204c ' . 204d . 205a ' . 205b ' electrically contacted. The electrical conductors 204a . 204b . 204c . 204d . 205a . 205b are on the first ceramic foil 201 arranged and partially of the second ceramic film 201b covered. Therefore, their location is partially indicated by dashed lines. The temperature measuring element 202 has a carrier plate 202c consisting of a single layer of Al ₂ O ₃ on. A platinum thin film element 202a for temperature measurement and 202d for heating and electrical connection cables 202b are on the back of the carrier plate 202c including electrically insulating coating arranged and therefore shown their location by dashed lines. The heating element 203 has a carrier plate 203c consisting of a single layer of Al ₂ O ₃ on. A platinum thin film element 203a as a heater and its electrical connection lines 203b are on the back of the carrier film 203c arranged and therefore shown their location by dashed lines.

The ceramic films 201 . 201b are in the area 206 either by direct sintering together or via a glass solder. The connection surfaces 204a ' . 204b ' . 204c ' . 204d ' . 205a ' . 205b ' are from the second ceramic foil 201b uncovered, so that a connection can be made with electrical connection cables, not shown here.

5 shows a hot-film anemometer with a ceramic film laminate 201 made from a first ceramic foil 201 from Al ₂ O ₃ and a second ceramic film 201b is formed from Al ₂ O ₃ . In series between the first ceramic foil 201 and the second ceramic foil 201b are two temperature measuring elements 202 . 208 and two heating elements 203 . 207 partially embedded and electrically contacted.

This in turn allows a measurement according to the principle of hot-film anemometer, as already to 4 described. The number of heating elements 203 . 207 and temperature measuring elements 202 . 208 but it now allows each one electrical control circuit for each heating element and a respective temperature measuring element ( 202 and 203 respectively. 207 and 208 ) to form and evaluate. It is now with this flow sensor element it is possible to detect the flow direction of a medium, since a transfer of thermal energy from the heating element, which is arranged first in the flow direction, to the subsequent heating element. The temperature change or heating of the subsequent heating element leads to a lower power consumption of this heating element, which can be evaluated as a signal for the flow direction of the medium.

5a shows the hot-film anemometer 5 in side view. It can be seen that the temperature measuring elements 202 . 208 and the heating elements 203 . 207 via electrical conductors 204a . 204b . 204c . 204d . 205a . 205b . 209a . 209b . 210a . 210b with connection surfaces 204a ' . 204b ' . 204c . 204d . 205a . 205b ' . 209a ' . 209b ' . 210a ' . 210b electrically contacted. The electrical conductors 204a . 204b . 204c . 204d . 205a . 205b . 209a . 209b . 210a . 210b are on the first ceramic foil 1a arranged and partially of the second ceramic film 201b covered. Therefore, their location is partially indicated by dashed lines. The temperature measuring element 202 has a carrier plate 202c consisting of two single layers of Al ₂ O ₃ and SiO ₂ on. A platinum thin film element 202a for temperature measurement and 202d for annealing and its electrical connection lines 202b are on the back of the carrier plate 202c arranged and therefore shown their location by dashed lines. The heating element 203 has a carrier plate 203c consisting of two single layers of Al ₂ O ₃ and SiO ₂ on. A platinum thin-film element 203a as a heater and its electrical connection lines 203b are on the back of the carrier plate 203c arranged and therefore shown their location by dashed lines. The heating element 207 has a carrier plate 207c consisting of two single layers of Al ₂ O ₃ and SiO ₂ on. A platinum thin film element 207a as a heater and its electrical connection lines 207b are on the back of the carrier plate 207c arranged and therefore shown their location by dashed lines. The temperature measuring element 8th has a carrier plate 208c consisting of two single layers of Al ₂ O ₃ and SiO ₂ on. A platinum thin film element 208d for temperature measurement and 202a for heating and its electrical connection lines 208b are on the back of the carrier plate 208c arranged and therefore shown their location by dashed lines.

The ceramic films 201 . 201b are in the area 206 either by direct sintering together or via a glass solder. The connection surfaces 204a ' . 204b ' . 204c ' . 204d ' . 205a ' . 205b ' . 209a ' . 209b ' . 210a ' . 210b ' 210c ' . 210d ' are from the second ceramic foil 201b uncovered, so that a connection can be made with electrical connection cables, not shown here.

7 shows a hot-film anemometer with a ceramic film laminate 201 made from a first ceramic foil 201 from Al ₂ O ₃ and a second ceramic film 201b is formed from Al ₂ O ₃ . In series between the first ceramic foil 201 and the second ceramic foil 201b are two temperature measuring elements 202 . 208 and a double heating element 211 . 211 ' partially embedded and electrically contacted. A double heating element is understood here to mean that two heating elements, which can be controlled electrically separately, are designed on a common carrier plate. Even with this flow sensor element, it is possible to detect the flow direction of a medium.

6a shows the hot-film anemometer 6 in side view. It can be seen that the temperature measuring elements 202 . 208 and the double heating element 211 . 211 ' via electrical conductors 204a . 204b . 204c . 204d . 205a . 205b . 209a . 209b . 210a . 210b 210c . 210d with connection surfaces 204a ' . 204b ' . 204c ' . 204d ' . 205a ' . 205b ' . 209a . 209b ' . 210a ' . 210b ' 210c ' . 210d ' electrically contacted. The electrical conductors 204a . 204b . 205a . 205b . 209a . 209b . 210a . 210b . 210c . 210d are on the first ceramic foil 201 arranged and partially of the second ceramic film 201b covered. Therefore, their location is partially indicated by dashed lines. The temperature measuring element 202 has a carrier plate 202c consisting of a single layer of Al ₂ O ₃ on. A platinum thin film element 202a for temperature measurement and 202d for heating and its electrical connection lines 202b are on the back of the carrier plate 202c including electrically insulating coating arranged and therefore shown their location by dashed lines. The double heating element 211 . 211 ' has a carrier plate 211c , consisting of two single layers of Al ₂ O ₃ and SiO ₂ on. Platinum thin film elements 211 . 211a ' as a heater and their electrical connection cables 211b . 211b 'are on the back of the carrier plate 211c including electrically insulating coating arranged and therefore shown their location by dashed lines. The temperature measuring element 208 has a carrier plate 208c , consisting of two single layers of Al ₂ O ₃ and SiO ₂ on. A platinum thin film element 208d for temperature measurement and 208a for heating and its electrical connection cables 208b are on the back of the carrier plate 208c arranged and therefore shown their location by dashed lines.

The ceramic films 201 . 201b be in the field 206 directly sintered together or connected by glass solder. The connection surfaces 204a ' . 204b ' . 204c ' . 204d ' . 205a ' . 205b ' . 209a . 209b ' . 210a ' . 210b ' 210c ' . 210d ' are from the second ceramic foil 201b uncovered, so connect with not shown here electrical connection cables can be made.

7 shows a hot-film anemometer with a ceramic film laminate 201 made from a first ceramic foil 201 , a second ceramic foil 201b and a third ceramic foil 201c is formed from Al ₂ O ₃ . Between the first ceramic foil 201 and the second ceramic foil 201b are two temperature measuring elements 202 . 202 ' partially embedded and electrically contacted. Between the second ceramic foil 201b and the third ceramic foil 201c is a double heating element 211 . 211 ' partially embedded and electrically contacted.

8th and 8a and 9 each show a hot-film anemometer with a ceramic film laminate 201 made from a first ceramic foil 201 , a second ceramic foil 201b and a third ceramic foil 201c is formed from Al ₂ O ₃ . Between the first ceramic foil 201 and the second ceramic foil 201b is a temperature measuring element 202 partially embedded and electrically contacted. Between the second ceramic foil 201b and the third ceramic foil 201c is a heating element 203 partially embedded and electrically contacted. With these flow sensor elements, it is not possible to detect the flow direction of a medium.

9a shows the flow sensor element 9 in side view. It can be seen that the temperature measuring element 202 and the heating element 203 via electrical conductors 204a . 204b . 205a . 205b with connection surfaces 204a ' . 204b ' . 205a ' . 205b ' electrically contacted. The electrical conductors 205a . 205b are on the first ceramic foil 201 arranged and partially of the second ceramic film 201b covered. Therefore, their location is partially indicated by dashed lines. The electrical conductors 204a . 204b , are on the second ceramic foil 201b arranged and partially from the third ceramic film 201c covered. Therefore, their location is partially indicated by dashed lines. The temperature measuring element 202 has a carrier film 202c consisting of a single layer of Al ₂ O ₃ on. A platinum thin film element 202a for temperature measurement and its electrical connection cables 202b are on the back of the carrier plate 202c including electrically insulating coating arranged and therefore shown their location by dashed lines. In a preferred embodiment, the carrier plate with an additional thin film element 202d equipped for heating the temperature element, which is electrically contacted analog. The heating element 20 has a carrier plate 203c consisting of a single layer of Al ₂ O ₃ on. A platinum thin film element 203a as a heater and its electrical connection lines 203b are on the back of the carrier plate 203c arranged and therefore shown their location by dashed lines. The ceramic films 201 . 201b are in the area 206 ' either by direct sintering together or via a glass solder. The connection surfaces 5a ' . 5b ' are from the second ceramic foil 1b uncovered, so that a connection can be made with electrical connection cables, not shown here. The ceramic films 1b . 1c are in the area 206 either by direct sintering together or via a glass solder. The connection surfaces 204a ' . 204b ' are from the third ceramic foil 201c uncovered, so that a connection can be made with electrical connection cables, not shown here.

9b shows the hot-film anemometer 9a in side view, this in the cross section of a pipeline 212 built-in. The carrier foils 202c . 203c of the temperature measurement element 202 and the heating element 203 are introduced parallel to the flow direction in the pipeline.

10 and 11 each show a hot-film anemometer with a ceramic film laminate 201 made from a first ceramic foil 201 , a second ceramic foil 201b , a third ceramic foil 201c and a fourth ceramic foil 201d is formed from Al ₂ O ₃ . Between the first ceramic foil 201 and the second ceramic foil 201b is a temperature measuring element 202 partially embedded and electrically contacted. Between the second ceramic foil 201b and the third ceramic foil 201c is a double heating element 211 . 211 ' partially embedded and electrically contacted. Between the third ceramic foil 201c and the fourth ceramic foil 201d is another temperature measuring element 202 ' partially embedded and electrically contacted.

12 shows a hot-film anemometer in cross-section AA '(see 12a ) with a multi-part ceramic component 213a . 213b . 214a . 214b from Al ₂ O ₃ , which is a temperature measuring element 202 and a heating element 203 having. The ceramic component 213a . 213b . 214a . 214b has two cavities 215a . 215b on, in the area of the temperature measuring element 202 or the heating element 203 are sealed gas-tight. For installation in a pipeline is a connection flange 216 available.

12a shows the hot-film anemometer 12 in side view. Here are the temperature measuring element 202 and the heating element 203 over here only partially recognizable electrical conductors 204a . 204b . 205a . 205b with connection surfaces 204a ' . 204b ' . 205a ' . 205b ' electrically contacted. The electrical conductors 204a . 204b . 205a . 205b are on a ceramic plate 214a arranged and - in this representation not visible - partly from a second ceramic plate 214b covered. The temperature measuring element 202 has a carrier plate 202c consisting of a single layer of Al ₂ O ₃ on. A platinum thin film element 202a for temperature measurement and its electrical connection cables 202b are on the back of the carrier film 202c arranged and therefore shown their location by dashed lines. In a preferred embodiment, the carrier plate 202c an additional platinum thin-film element 202d with an order of magnitude smaller resistance. This resistance intended for annealing or annealing is analogous to the thin-film element with an additional contact 202a electrically contacted. The heating element 203 has a carrier plate 203c consisting of a single layer of Al ₂ O ₃ on. A platinum thin film element 203a as a heater and its electrical connection lines 203b are on the back of the carrier plate 203c arranged and therefore shown their location by dashed lines.

The ceramic plates 214a . 214b are either by directly sintering together or with a glass solder together and with pipe shells 213a . 213b connected to the ceramic component. But it is also possible to use two half pipes ( 213a plus 214a ; 213b plus 214b ) to use where the ceramic plate 214a and the pipe shell 213a or the ceramic plate 214b and the pipe shell 214b are each combined to form a one-piece component. The connection surfaces 204a ' . 204b ' . 205a ' . 205b ' are from the second ceramic plate 214b uncovered, so that a connection can be made with electrical connection cables, not shown here.

To 13a is a hot film anemometer with potting or glass 118 in a carrier disk 121 made of heat- and exhaust-resistant stainless steel. Through a structured inner wall of the Vergussraums example by a thread 130 a good Verkrallung the potting is achieved. The area of the carrier disk 121 , through which the sensor element emerges toward the medium, has a rectangular contour which is only slightly larger than the sensor element cross-section.

This directs the hot-film anemometer into the media-carrying tube 105 held and the interior of the complete sensor sealed against the medium.

The carrier disk 121 is in a housing 124 used and with a round seam 122 tightly welded. In the housing tube 124 is the case 111 shrink wrapped. In the case 111 becomes the insulator 110 made of temperature-resistant plastic or ceramic with a ring 109 that by a bead 117 is fixed, held. At the cable exit is with the bead 116 a cable bushing made of an elastomer tightly fastened. leads 104 are through the holes of a grommet 114 guided. Each lead is over a crimp 125 with a contact sleeve 103 electrically connected. The contact sleeve 103 points under an insulating part 110 a broadening 126 and above the insulating part 110 an area 127 , which is wider than the contact sleeve diameter, on, so that the contact sleeve in the axial direction in the insulating part 110 is fixed. On the surface 127 become the connecting wires 102 with the weld 115 electrically contacted.

The attachment of the complete sensor to the media-carrying pipe 105 via a standard screw thread hose clamp 113 and one on the media-carrying pipe 105 welded, slotted Blechflanschteil 112 ,

The orientation of the hot-film anemometer 101 in the pipe 105 via a centering pin 119 on the casing tube 124 is attached and over the wide slot 120 in the sheet metal flange part 112 , Opposite a wide slot 120 is a narrow slot 123 provided, which only serves the Blechflanschteil 112 easier on the housing tube 124 to press on. This will allow mounting only in the correct angular position.

13b shows another embodiment with a ceramic carrier disk 107 in which the flow element 101 with glass solder 118 in the carrier disk 107 is attached. The carrier disk 107 is together with a high temperature resistant gasket 108 made of mica or graphite in the metallic version 106 crimped. The version 106 is also with the housing tube 124 tightly welded.

In an execution of the hot film anemometer the heating element is designed as a heating power sensor and the Temperature measuring element as a temperature sensor, the addition of a Wear heat conductor for glowing can.

To 15 For this purpose, two heating power sensors 128 arranged for direction detection of the media flow. In principle, the anemometric measuring principle works in such a way that the temperature measuring element accurately detects the temperature of the medium. The one or both heating elements of the heating power sensor (s) 128 are then at a constant excess temperature to the temperature sensor 129 held by an electrical circuit. The gas or liquid flow to be measured more or less cools the heating element (s) of the heating power sensor (s).

In order to maintain the constant over-temperature, the electronics must be able to supply current to the heating element (s) in the event of mass flow; this generates a voltage at an exact measuring resistor, which is correlated with the mass flow and can be evaluated. The double arrangement of the heating power sensor 128 or temperature sensor 129 allows direction detection of the mass flow.

By contrast, after 16 in one embodiment, as a soot sensor two heater power sensors inserted parallel opposite in a tubular housing.

The two heating power sensors 128 are still each with a glazed ceramic plate 131 Mistake.

In the specified arrangement is a Heizleistungssensor above operated at the pyrolytic incineration temperature; i.e. at approx. 500 ° C. Of the second heating power sensor is in this case in a lower temperature range from 200-450 ° C, preferably from 300 to 400 ° C operated. With soot deposit on this second heating power sensor, this deposit layer acts as thermal isolation and change of the IR radiation properties in the sense of an increasingly black body.

This can electronically in a reference measurement to the first heater power sensor be evaluated.

Claims (25)

Device for exhaust gas recirculation from an exit region ( 4 ) of a vehicle internal combustion engine ( 1 ) into an air inlet area ( 2 ), which is an adjustable mixture of exhaust gas and incoming air of the machine ( 1 ), and an amount of fuel is adjustable, wherein the exit area ( 4 ) via an exhaust gas recirculation line, which has a controllable valve ( 5 ), an exhaust gas cooling device ( 8th ) and a hot-film anemometer ( 10 ), with an entry area ( 2 ) of the internal combustion engine ( 1 ), wherein the hot-film anemometer ( 10 ) a heating resistor ( 29 . 128 . 203 . 207 ) and a temperature measuring resistor ( 27 . 129 . 202 . 208 ), the heating resistor ( 29 . 128 . 203 . 207 ) and the temperature measuring resistor ( 27 . 202 . 129 . 208 ) separate sheet resistors ( 128 . 129 . 202 . 203 . 207 . 208 . 211 ), characterized in that the temperature measuring resistor ( 27 . 129 . 202 . 208 ) and the heating resistor ( 29 . 128 . 203 . 207 ) each on a ceramic support ( 7 . 201 ) are attached. Device according to claim 1, characterized in that the sheet resistances ( 202 . 203 . 207 . 208 . 211 ) with conductor tracks ( 202a . 203a ) coated ceramic substrates ( 202c . 203c ) are. Device, in particular according to one of claims 1 or 2, for exhaust gas recirculation from an exit region ( 4 ) of a vehicle internal combustion engine ( 1 ) into an air inlet area ( 2 ), which is an adjustable mixture of exhaust gas and incoming air of the machine ( 1 ), and an amount of fuel is adjustable, wherein the exit area ( 4 ) via an exhaust gas recirculation line, which is a controllable valve ( 5 ), an exhaust gas cooling device ( 8th ) and a hot-film anemometer ( 10 ), with an entry area ( 2 ) of the internal combustion engine ( 1 ), wherein the hot-film anemometer ( 10 ) a heating resistor ( 29 ) and a temperature measuring resistor ( 27 . 202 . 129 . 208 ), the heating resistor ( 29 . 128 . 203 . 207 ) and the temperature measuring resistor ( 27 . 202 . 129 . 208 ) are separate sheet resistors, characterized in that the hot-film anemometer ( 10 ) in an exhaust gas recirculation passage before cooling ( 8th ) or in an air-cooled cooler. Device, in particular according to one of claims 1 to 3 for exhaust gas recirculation from an outlet region of a vehicle internal combustion engine in an air inlet region to which an adjustable mixture of exhaust gas and incoming air can be supplied to the machine, and an amount of fuel is adjustable, the exit region ( 4 ) via an exhaust gas recirculation line, which is a controllable valve ( 5 ), an exhaust gas cooling device ( 8th ) and a hot-film anemometer ( 10 ), with an entry area ( 2 ) of the internal combustion engine is connected, wherein the mass flow sensor a heating resistor ( 29 . 128 . 203 . 207 ) and a temperature measuring resistor ( 27 . 202 . 129 . 208 ), the heating resistor and the temperature measuring resistor ( 27 . 202 . 129 . 208 ) are separate sheet resistors, characterized in that neither for the fresh air nor for the cooled exhaust gas another hot-film anemometer ( 10 ) is arranged. Device according to one of the preceding claims, characterized in that the temperature measuring element ( 27 . 202 . 129 . 208 ) two platinum thin-film resistors ( 202a . 202d . 208a . 208d ) on a ceramic substrate ( 202c . 208c ), whose resistances are many times apart. Device according to one of the preceding claims, characterized in that a multi-part ceramic component of the hot-film anemometer ( 10 ) a carrier element ( 7 ), a temperature measuring element ( 27 . 202 . 129 . 208 ) and a heating element ( 29 . 128 . 203 . 207 ). Device according to one of the preceding claims, characterized in that its hot-film anemometer ( 10 ) an opening of a lid ( 107 ) or a hollow body surface in which a temperature measuring element ( 27 . 129 ) and a heating element ( 29 . 128 ) are attached. Device according to one of claims 5 to 7, characterized in that the two resistors ( 202a . 202d . 203a . 207a . 208a . 208d ) of the temperature measuring element ( 27 . 129 . 202 . 208 ) lie in one plane. Device according to one of claims 5 to 8, characterized in that the smaller resistance (heater 202d ) of the temperature measuring element ( 27 . 129 . 202 . 208 ) the greater resistance ( 202a for temperature measurement) of the temperature measuring element ( 27 . 129 . 202 . 208 ) framed. Device according to one of claims 1 to 9, whose hot-film anemometer ( 10 ), Sheet resistors comprising a substrate having an electrically insulating surface and a structured resistive layer ( 202a . 202d . 208a . 208d ) in one or more openings of a lid (s) ( 107 ) or a hollow body end face, the sheet resistances ( 128 . 129 ) are mounted in the opening (s) and wherein two sheet resistances differ in resistance by one to three orders of magnitude. Device according to claim 10, characterized in that two sheet resistors ( 128 . 129 ) on a common ceramic substrate ( 107 ) are held in an opening. Apparatus according to claim 10 or 11, characterized in that on ceramic substrates ( 202c . 203c . 207c . 208c ) two resistors in the strict sense as resistors in the form of interconnects ( 202a . 203a . 207a . 208a ) and the two ceramic substrates ( 202c . 203c . 207c . 208c ) are fastened in each case in an opening. Device according to one of claims 10 to 12, characterized that the footprint the opening (s) at one to five orders of magnitude smaller than the lid base or front side. Device according to one of claims 10 to 13, characterized in that the lid ( 107 ) is disc-shaped. Device according to one of claims 1 to 14, in which a temperature sensor ( 27 . 202 . 129 . 208 ) and a heating power sensor ( 29 . 128 . 203 . 207 ) in a carrier element ( 107 ), characterized in that the temperature sensor ( 27 . 202 . 129 . 208 ) a temperature measuring resistor and a heating conductor as platinum thin-film or thick-film resistors ( 202a . 202d . 208a . 208d ) has on ceramic substrate. Apparatus according to claim 15, characterized in that the carrier element ( 107 . 201 ) consists of temperature-resistant inorganic material (250 ° C, in particular> 400 ° C continuous use temperature). Device according to one of claims 15 or 16, characterized in that the temperature measuring element ( 129 ) and the heating element ( 128 ) perpendicular to the carrier element ( 107 ) are arranged. Method for exhaust gas recirculation in an air inlet region of a vehicle internal combustion engine to which an adjustable mixture of cooled exhaust gas and incoming air is supplied to the engine and an amount of fuel is supplied and from recirculated exhaust gas by means of a hot-film anemometer ( 10 ) an actual value signal (X, X1, X2) is formed and compared with a setpoint signal (w) for an optimum operating point of the machine, wherein a control deviation of the actual value signal leads to a control signal (Y, Y1, Y2), which engages in the exhaust gas recirculation, the hot-film anemometer ( 10 ) a temperature measuring resistor ( 27 . 202 . 129 . 208 ) and a heating resistor ( 29 . 128 . 203 . 207 ), characterized in that the exhaust gas in front of a radiator ( 8th ) or in an air-cooled cooler having a sheet resistors hot film anemometer ( 10 ) is supplied. A method according to claim 21, characterized in that the temperature measuring element ( 27 . 202 . 129 . 208 ) a platinum thin film resistor ( 202a ) on a ceramic substrate for temperature measurement and with an additional platinum thin-film resistor ( 202d ) is heated. Method for self-cleaning a hot-film anemometer ( 10 ) of a device according to one of claims 1 to 17, wherein a temperature measuring element ( 27 . 129 . 202 . 208 ) and a heating element ( 29 . 128 . 203 . 207 ) on a common carrier element ( 107 . 201 ) are arranged, characterized in that the temperature measuring element ( 27 . 202 . 129 . 208 ) a platinum thin film resistor ( 202a ) on a ceramic substrate ( 202c ) for temperature measurement and with an additional platinum thin-film resistor ( 202d ) is heated. Method for self-cleaning a hot-film anemometer ( 10 ) of a device according to one of claims 1 to 17, wherein a temperature measuring element and a heating element ( 29 . 128 . 203 . 207 ) in an opening of a lid ( 107 ) or a hollow body surface, characterized in that the temperature measuring element ( 27 . 202 . 129 . 208 ) a platinum thin film resistor ( 202a ) on a ceramic substrate ( 202c ) for temperature measurement and with an additional platinum thin-film resistor ( 202d ) is heated. Method for producing a hot-film anemometer ( 10 ) of a device according to claim 6, wherein a temperature measuring element ( 27 . 129 . 202 . 208 ) and a heating element ( 29 . 128 . 203 . 207 ) on a carrier element ( 107 . 201 ) are arranged, characterized in that the carrier element ( 201 ) made of ceramic films ( 201 . 201b . 201c ) is laminated. Method for producing a hot-film anemometer ( 10 ) of a device according to one of claims 7 to 17 of sheet resistors and a lid ( 107 ) or a hollow body, wherein at least two sheet resistors, whose resistance differ by one or two orders of magnitude, in openings of the cover ( 107 ) or hollow body and fastened in the openings. Method for self-cleaning a hot-film anemometer ( 10 ) of a device according to one of claims 7 to 17, wherein a temperature measuring element and a heating element ( 29 . 128 . 203 . 207 ) are inserted into a carrier element, characterized in that the temperature measuring element ( 27 . 202 . 129 . 208 ) a platinum thin film resistor ( 202a ) on a ceramic substrate ( 202c ) for temperature measurement and with an additional platinum thin-film resistor ( 202d ) is heated. Use of a device according to claim 6 for mass flow measurement of gaseous or liquid media through pipelines ( 12 ), with carrier foils ( 2c . 3c . 7c . 8c . 11c ) are arranged parallel to the flow direction of the medium.