DE102016125354B4 - Gas measuring device and gas measuring method - Google Patents

Abstract

Gas measuring device (10) for measuring an exhaust gas flowing in an exhaust pipe (100) of an internal combustion engine, characterized by a housing (20) with at least one housing section (25) formed outside the exhaust pipe (100) of an internal combustion engine, in which a sensor (50) is located completely outside the exhaust pipe (100), the gas measuring device (10) comprising at least one feed channel (30) which diverts a partial exhaust gas flow into the housing (20), the sensor (50) being an NOx sensor , dera) a ceramic substrate (51),b) an oxidic semiconductor layer (52) applied to the substrate, namely a tungsten trioxide layer or a manganese oxide layer, andc) at least two electrodes which are electrically contacted with the semiconductor layer (52). , wherein the feed channel (30) is a pitot tube or a dead water tube.

Description

The invention relates to a gas measuring device for measuring an exhaust gas flowing in an exhaust pipe of an internal combustion engine. In addition, the invention relates to a gas measuring method using a gas measuring device according to the invention.

Exhaust gas sensors in the automotive sector are known from the prior art, with the aid of which the concentration of nitrogen oxides (NO, NO ₂ ) can be measured. The nitrogen oxides are not measured directly. Rather, the oxygen released in the process is determined by targeted reduction of the nitrogen. This is possible in particular with the aid of an oxygen-ion-conducting material that is operated using the amperometric measuring method. Such sensors consist of several multilayer cofired ZrOz layers. However, these sensors have several disadvantages. In particular, the detection limit of such sensors is 100 ppm for NO ₂ . From today's point of view, such sensors are therefore too imprecise for exhaust gas tests. A further disadvantage is that the individual ceramic layers of such sensors have to be manufactured individually and the sensors are therefore extremely expensive. At a sensor price of EUR 70 - 90 per sensor, such sensors cannot be used across the board in vehicles with internal combustion engines.

Furthermore, nitrogen oxide sensors based on oxidic semiconductor layers are known. Adsorption of NO ₂ on the surface of the oxidic semiconductor changes its electrical resistance as a result of doping or dedoping. These sensors are extremely sensitive to NO ₂ and can also be manufactured inexpensively. However, such sensors are extremely sensitive to heat.

EP 1 445 608 A1 discloses a gas sensor, primarily an oxygen sensor, for use in an exhaust system. The sensor of the sensor unit is located inside the exhaust pipe. Consequently, in accordance with the device EP 1 445 608 A1 only such sensors are used that withstand the high temperatures in an exhaust gas flow.
In DE 198 56 369 A1 describes a resistive gas sensor whose gas-sensitive layer consists of a mixture of WO ₃ /TiO ₂ ≥50% by weight.

The invention is based on the object of specifying a further developed gas measuring device which enables cost-effective measurement of an exhaust gas flowing in an exhaust pipe of an internal combustion engine. In particular, the use of nitrogen oxide sensors for exhaust gas monitoring of internal combustion engines should be made possible. Furthermore, it is the object of the present invention to specify a further developed gas measuring method.

According to the invention, this object is achieved with regard to the gas measuring device by the features of claim 1. With regard to the gas measurement method, the object is achieved by the features of claim 8.

The invention is based on the idea of specifying a gas measuring device for measuring an exhaust gas flowing in an exhaust pipe of an internal combustion engine, the gas measuring device comprising a housing with at least one housing section formed outside the exhaust pipe of an internal combustion engine, with a sensor being located in the housing section is. Furthermore, the gas-measuring device includes a feed channel, which diverts a partial exhaust gas flow into the housing. In other words, part of the exhaust gas flowing through the exhaust pipe is branched off from the exhaust pipe and diverted into the housing, in particular into the housing section formed outside of the exhaust pipe.

1. a) ein keramisches Substrat,
2. b) eine auf dem Substrat aufgebrachte oxidische Halbleiterschicht, nämlich eine Wolframtrioxid-Schicht oder eine Manganoxid-Schicht, und
3. c) mindestens zwei Elektroden, die mit der Halbleiterschicht elektrisch kontaktiert sind,

umfasst.According to the invention, the sensor is a NOx sensor

1. a) a ceramic substrate,
2. b) an oxidic semiconductor layer applied to the substrate, namely a tungsten trioxide layer or a manganese oxide layer, and
3. c) at least two electrodes which are electrically contacted with the semiconductor layer,

includes.

According to the invention, the feed channel is a pitot tube or a dead water tube. In the following, a dynamic pressure sensor is not to be understood as a pitot tube. Rather, the shape of the pipe is decisive. The feed duct serves to conduct a partial exhaust gas stream of the exhaust gas flowing in the exhaust pipe into the housing, in particular into the housing section formed outside of the exhaust pipe.

The partial exhaust gas flow is preferably cooled from the inlet of the exhaust gas pipe until it reaches the sensor. It is therefore possible to use a gas measuring device with known nitrogen oxide sensors based on oxidic semiconductor layers. The supply channel, in particular the pitot tube or the dead water tube, are used to ensure that a constant proportion of the exhaust gas, namely a constant partial exhaust gas flow in the Housing section is passed. The feed channel can form a kind of bypass together with the housing.

In one embodiment of the invention, the housing can be formed entirely outside the exhaust pipe. In such an embodiment, only a portion of the feed channel and/or a portion of a feed channel and a discharge channel is/are located at least in sections within the exhaust pipe.

The gas-measuring device can also include a discharge channel that establishes a fluid connection from the interior of the housing to the exhaust pipe and/or to the surroundings of the housing. Accordingly, it is possible for the partial exhaust gas flow, after it has flowed over the sensor, to be fed back either directly into the area surrounding the housing and/or via the discharge duct into the exhaust gas pipe. By suitably directing the partial exhaust gas flow, dead water areas can be avoided in order to enable a fast response time of the sensor.

In one embodiment, the discharge channel can be designed in the shape of a periscope. Accordingly, such a feed duct initially comprises a curved section which is preferably oriented counter to the direction of flow of the exhaust gas. In other words, the inlet opening of the exhaust pipe is arranged in the exhaust pipe counter to the direction of flow. A line section angled at 90° is preferably connected to the bent section of the supply line channel. This line section preferably ends in an outlet opening through which the partial exhaust gas flow flows into the housing of the gas measuring device. In other words, the outlet opening is used for the fluid connection of the feed channel to the housing.

In one embodiment of the invention, the discharge channel can be designed as a separate pipe from the supply channel. In particular, it is possible for the discharge channel to be formed in a vertical extension to the feed channel. Such an embodiment of the discharge channel is used for fluid connection from the housing interior to the housing environment. Furthermore, it is possible for the discharge channel to be mirror-symmetrical to the feed channel. Accordingly, the discharge channel can also be designed in the shape of a periscope, with the curved section of the discharge channel being aligned in the flow direction of the exhaust gas in the exhaust pipe. In such an embodiment, the line sections of the discharge channel and of the feed channel can run parallel to one another.

In a further embodiment of the invention, the gas measuring device can comprise a double-walled tube with an inner tube and an outer tube. An intermediate space formed between the inner pipe and the outer pipe is preferably designed as a/the discharge channel. In such an embodiment, the inner tube is preferably designed as a feed channel. The supply channel and the discharge channel are preferably dimensioned in such a way that their flow resistances are similar to one another.

The outlet opening of a discharge channel is preferably oriented in the direction of flow of the exhaust gas in such a way that a negative pressure is generated in the discharge channel. This principle is also implemented in the design with a double-walled tube. The outer tube preferably has a plurality of openings, in particular a plurality of slit-shaped openings. In the present example, the Pitot tube is to be understood as an angled tube whose inlet opening opposes the inflowing exhaust gas, while the outlet opening is either outside the exhaust gas flow or is oriented parallel to the exhaust gas flow. Due to the pressure difference between the two openings, a separate fluid flow occurs in the pitot tube, in which the partial exhaust gas flow is conducted to the housing section formed outside of the exhaust gas tube.

In a further embodiment of the invention, the discharge channel can have at least one opening, the discharge channel being positioned in the exhaust pipe in such a way that the exhaust gas flowing in the exhaust pipe flows through the opening. If the feed channel is designed as a dead water pipe, the partial exhaust gas flow reaches the housing section designed outside of the exhaust pipe by diffusion.

In a further embodiment of the invention, an element that cleans and/or conditions the partial exhaust gas flow can be formed in the feed duct. An element that cleans the partial exhaust gas flow can in particular be a particle filter and/or a catalytic converter. Furthermore, it is possible for a device for adjusting the temperature of the partial exhaust gas flow to be configured in the feed duct. A metering device for gases and/or aerosols can, for example, be designed as an element that conditions the partial exhaust gas flow.

The gas measuring device preferably comprises at least one sleeve with an external thread and/or a ring with an external thread, the sleeve and/or ring being designed to connect the housing to the exhaust gas pipe. In a particularly preferred embodiment form, the sleeve and/or the ring are formed on the feed channel. When the gas measuring device is designed with a sleeve described in this way and/or a ring described in this way, it is possible to introduce the gas measuring device into the exhaust gas pipe in the sense of a screw-in sensor.

Furthermore, it is possible for the gas-measuring device to have a preferably ring-shaped fastening flange. This attachment flange can be attached to the exhaust pipe.

1. a) ein keramisches Substrat,
2. b) eine auf dem Substrat aufgebrachte oxidische Halbleiterschicht, und
3. c) mindestens zwei Elektroden, die mit der Halbleiterschicht elektrisch kontaktiert sind.

The sensor located in the housing of the gas measuring device can be a gas mass flow sensor and/or a gas sensor and/or a temperature sensor. The sensor is particularly preferably an NOx sensor. In a highly preferred embodiment of the invention, the sensor is an NO ₂ sensor. Furthermore, it is possible that not only one sensor but several sensors are formed in the housing. In such a case, the gas-measuring device comprises a sensor assembly that has a number of different sensors.
The gas measuring device has an NOx sensor, in particular an NO ₂ sensor, which includes:

1. a) a ceramic substrate,
2. b) an oxidic semiconductor layer applied to the substrate, and
3. c) at least two electrodes which are electrically contacted with the semiconductor layer.

In other words, the at least two electrodes are in electrical contact with the oxidic semiconductor layer. The oxidic semiconductor layer is a tungsten trioxide layer or a manganese oxide layer (MnO, Mn ₂ O ₃ ). The use of other metal oxides is also possible.

Furthermore, the NOx sensor, particularly the NO ₂ sensor, can include a heating element. The heating element is preferably located on the opposite side of the substrate to the oxidic semiconductor layer. Furthermore, it is possible for a porous covering ceramic to be applied to the oxidic semiconductor layer. This covering ceramic protects the oxidic semiconductor layer.

The electrodes described under c) are preferably two interlocking comb electrodes. Such electrodes can be applied to the ceramic substrate, for example, by screen printing. The at least two electrodes are preferably made of platinum. The (comb) electrodes are then coated with the oxidic semiconductor layer. The oxidic semiconductor layer can be applied by screen printing or by RF sputtering. The heating element described, in particular the heating resistor, can then be applied to the still free side of the substrate. The heating resistor can be made of platinum, for example.

The heating element, in particular the heating resistor, allows the temperature of the ceramic substrate to be controlled during operation. At the same time, the temperature can also be measured via the resistor. Preferably, all leads to the contacts are made of Teflon insulated wires.

In a further embodiment of the invention it is possible to cover the oxidic semiconductor layer with a further gas-permeable protective layer. This layer can consist of manganese dioxide (MnO ₂ ), for example. The additional gas-permeable protective layer serves in particular to prevent contamination from foreign gases.

Overall, it can be stated that based on the gas measuring device according to the invention, an analysis of an exhaust gas flowing in an exhaust pipe (in particular an analysis of the nitrogen oxides) can be carried out with sensors of high sensitivity. The trained nitrogen oxide sensors have a high sensitivity of 0 - 100 ppm. The inventive derivation of a partial exhaust gas flow into a housing section formed outside of the exhaust gas pipe leads to fast response times of the sensor. This is desired, for example, in the case of rapid load changes in the internal combustion engine. This is due to the fact that the partial exhaust gas flow is guided directly and continuously via the sensor and dead water areas are avoided.

1. a) Ableiten eines Teil-Abgasstroms des Abgases aus dem Abgasrohr mittels des Ableitungskanals;
2. b) Leiten des Teil-Abgasstroms in den außerhalb des Abgasrohrs ausgebildeten Gehäuseabschnitt;
3. c) Leiten des Teil-Abgasstroms über den Sensor.

A further aspect of the invention relates to a gas measuring method which is carried out using a gas measuring device according to the invention. The gas measurement process is characterized by the following process steps:

1. a) diverting a partial exhaust gas flow of the exhaust gas from the exhaust pipe by means of the discharge channel;
2. b) conducting the partial exhaust gas flow into the housing section formed outside of the exhaust pipe;
3. c) Passing the partial exhaust gas flow over the sensor.

In step b), the partial exhaust gas stream is cooled. The partial exhaust gas flow is cooled such that the temperature of the partial exhaust gas flow at the sensor is less than 500° C., in particular less than 400° C., in particular less than 300° C. Due to the cooling of the partial exhaust gas flow according to the invention, a sensor based on an oxidic semiconductor layer can be used in particular.

Between step b) and step c), the partial exhaust gas stream can be cleaned and/or conditioned. The partial exhaust gas flow is preferably cleaned by means of a particle filter or by means of a catalytic converter. Furthermore, it is possible for further gas and/or aerosol to be added to the partial exhaust gas flow. The partial exhaust gas flow can be conditioned by adding further gas or aerosol.

The gas measurement method can include a step d) in which the partial exhaust gas flow is fed back into the exhaust pipe or is diverted into the surroundings of the housing.

The gas measuring method and the gas measuring device are preferably designed in such a way that the sensor is a gas sensor that measures the concentration of gas components of the partial exhaust gas flow.

The invention is explained in more detail below using exemplary embodiments with reference to the accompanying schematic drawings.

• 1 eine erfindungsgemäße Gas-Messvorrichtung gemäß einer ersten Ausführungsform;
• 2 eine Prinzip-Darstellung einer Bypass-Anordnung;
• 3 - 6 weitere Ausführungsformen der erfindungsgemäßen Gas-Messvorrichtung.

In these show:

• 1 a gas measuring device according to the invention according to a first embodiment;
• 2 a schematic representation of a bypass arrangement;
• 3 - 6 further embodiments of the gas measuring device according to the invention.

In the following, the same reference numerals are used for the same and equivalent parts.

In 1 1 shows a gas measuring device 10 according to the invention for measuring an exhaust gas flowing in an exhaust pipe 100 (shown schematically) of an internal combustion engine. The gas measuring device 10 also includes a housing 20. In the exemplary embodiment shown, the complete housing 20 is formed outside of the exhaust gas pipe 100. FIG. In other specific embodiments, it is also possible for only one housing section to be formed outside of the exhaust gas pipe 100 .

The gas measuring device 10 also includes a feed channel 30 which diverts a partial exhaust gas flow into the housing 20 . The feed channel 30 is designed as a pitot tube. This comprises a first angled section 31 and a line section 32 protruding therefrom at 90°. The inlet opening 33 is oriented opposite to the direction of flow S of the exhaust gas. The outlet opening 34 of the feed channel 30 is formed outside of the exhaust pipe 100 . The pressure difference between the inlet opening 33 and the outlet opening 34 results in a separate fluid flow in the feed channel 30 . In this fluid flow, a partial exhaust gas flow flows in the direction of the housing 20.

The partial exhaust gas flow can be routed directly to the sensor 50 in the housing 20 . The temperature inside the housing 20 is preferably 300°C at most. By arranging a filter 70 in the feed channel 30, cleaning is effected in addition to the cooling of the partial exhaust gas stream. Accordingly, a clean gas space is formed within the housing 20 .

In the example shown, the sensor 50 consists of a ceramic substrate 51, an oxidic semiconductor layer 52 applied to the substrate 51 and at least two electrodes which are electrically contacted with the semiconductor layer. Sensor 50 is preferably an NOx sensor, in particular an NO ₂ sensor. A heating element, in particular a heating resistor, can be formed on the rear side of the substrate 51 . Furthermore, a porous covering ceramic 54 is formed above the oxidic semiconductor layer 52 .

After the partial exhaust gas flow has flowed around the sensor 50 , the partial exhaust gas flow is routed through the discharge channel 40 to the exhaust gas pipe 100 . The discharge channel 40 thus establishes a fluid connection from the housing interior 21 to the exhaust pipe 100 . In the present exemplary embodiment, the gas measuring device 10 has a double-walled tube 15 with an inner tube 35 and an outer tube 36 . The intermediate space formed between the inner tube 35 and the outer tube 36 is in the present case designed as a discharge channel 40 . The feed channel 30 , on the other hand, is formed by the inner tube 35 .

The discharge channel 40 has a plurality of openings 41 through which the partial exhaust gas flow can escape into the exhaust pipe 100 . The openings 41 are preferably formed or arranged in the outer pipe 36 in such a way that the exhaust gas stream S flows through the openings 41 . As a result, a pressure gradient forms between the openings 41 of the outer tube 36 and the housing section 25 and there is a flow of fluid from the housing portion 25 into the exhaust stream.

The gas measuring device 10 also includes a sleeve 60 with an external thread 61. The sleeve 60 also includes a flange section 62. The flange section 62 rests on the exhaust pipe 100. FIG. The sleeve 60 can be screwed into the exhaust pipe 100 with the aid of the external thread 61 .

In 2 an exhaust gas pipe 100 with a gas measuring device 10 according to the invention is shown schematically. This figure shows schematically that the gas measuring device 10 can include two separate tubes, namely a supply channel 30 and a discharge channel 40 . The gas measuring device 10 is designed in the sense of a bypass. This means that a partial exhaust gas flow is branched off from the exhaust gas flowing in the exhaust gas pipe 100 , is conducted into the housing 20 by means of the feed channel 30 and to the sensor 50 formed in the interior 21 of the housing. The partial exhaust gas flow is then fed back into the exhaust gas pipe 100 . In this construction, too, the partial exhaust gas flow is expediently cooled to below 400° C. before it hits the sensor 50 .

In 2 it is also indicated that a plurality of sensors, namely an NO ₂ sensor 50 and an NOx sensor 50 ′, can be formed in the interior of the housing 21 .

In 3 a further embodiment of the gas measuring device 10 is shown. The feed channel 30 shown there also has an angled section 31 and a vertical line section 32 . The feed channel 30 ends in the housing 20 in which the sensor 50 is located. The discharge channel 40, in particular the inlet opening 42, is formed in a vertical extension to the feed channel 30. The discharge channel 40 is used for the fluid connection from the housing interior 21 to the housing environment 101. The outlet opening 43 of the discharge pipe 40 is accordingly formed in the housing environment 101.

In 4 a further embodiment of a gas measuring device 10 is shown. The feed channel 30 and the discharge channel 40 are essentially mirror-symmetrical to one another. Accordingly, both channels 30 and 40 each have an angled section 31 and 44 and a line section 32 and 45 . Both line sections 32 and 45 are located in a protective sleeve 75 . It can be seen that the inlet opening 42 of the discharge channel 40 is formed in a horizontal extension to the outlet opening 34 of the feed channel 30 . In order to enable such an arrangement of the openings 33 and 42, both the feed channel 30 and the discharge channel 40 each have a bent section 37 and 47.

In 5 a gas measuring device 10 with a housing 20 is shown, the housing 20 being located completely outside the exhaust gas pipe 100 . The sensor 50 is again located in the interior of the housing 21 . The measured values of the sensor 50 can be transmitted by means of a line 55 . The axial end section 39 of the feed channel 30 is introduced into the interior 21 of the housing. In the example shown, the feed channel 30 and the discharge channel 40 are designed as a single component. The pipe is designed as a dead water pipe. The partial exhaust gas flow does not reach sensor 50 by direct line. Rather, a partial exhaust gas flow reaches sensor 50 by diffusion of the exhaust gas flowing in exhaust gas pipe 100. Pipe 30 or 40 has a trumpet-like opening section 38 for this purpose. The inlet opening 33 or 43 is positioned in the exhaust pipe 100 in such a way that the exhaust gas flowing in the exhaust pipe 100 flows past the opening 33 or 43 .

In 6 an alternative embodiment of a gas measuring device 10 is shown. This has in contrast to the embodiments of 3 - 5 no sleeve 60 but only a mounting flange 65.

Furthermore, the complete housing 20 is not formed outside of the exhaust gas pipe 100, but only the housing section 25. The sensor 50 is located in this housing section 25. In the example shown, a plurality of supply channels 30 are formed. These are designed as openings in the housing 20 . Several rows of supply channels 30 are preferably formed. The drain passage 40 is formed inside the case 20 . In other words, the housing 20 is configured concentrically with the discharge channel 40 . The outlet opening 43 is designed as an opening in the end face 26 of the housing 20 . Since the sensor 50 is also formed outside the exhaust gas pipe 100 in this example, the partial exhaust gas flow is cooled on the way from the feed ducts 30 to the sensor 50 .

Reference List

10

gas measuring device

15

Double-walled tube

20

housing

21

case interior

25

housing section

26

face

30

supply channel

31

Angled section

32

line section

33

entrance opening

34

exit port

35

inner tube

36

outer tube

37

bend section

38

opening section

39

end section

40

drainage channel

41

opening

42

entrance opening

43

exit port

44

Angled section

45

line section

47

bend section

50, 50'

sensor

51

substrate

52

Oxide semiconductor layer

53

heating element

54

covering layer

55

management

60

sleeve

61

external thread

62

flange section

65

mounting flange

70

filter

75

protective sleeve

100

exhaust pipe

101

housing environment

S

Flow direction of exhaust gas

Claims (11)

Gas measuring device (10) for measuring an exhaust gas flowing in an exhaust pipe (100) of an internal combustion engine, characterized by a housing (20) with at least one housing section (25) formed outside the exhaust pipe (100) of an internal combustion engine, in which a sensor (50 ) is located completely outside the exhaust pipe (100), the gas measuring device (10) comprising at least one feed channel (30) which derives a partial exhaust gas flow into the housing (20), the sensor (50) being a NOx sensor which is a) a ceramic substrate (51), b) an oxidic semiconductor layer (52) applied to the substrate, namely a tungsten trioxide layer or a manganese oxide layer, and c) at least two electrodes which are connected to the semiconductor layer (52) are electrically contacted, includes, wherein the feed channel (30) is a pitot tube or a dead water tube. Gas measuring device (10) according to claim 1 , characterized by a discharge channel (40) which establishes a fluid connection from the interior of the housing (21) to the exhaust pipe (100) and/or to the surroundings of the housing (101). Gas measuring device (10) according to one of the preceding claims, characterized by a double-walled tube (15) with an inner tube (35) and an outer tube (36), with an intermediate space formed between the inner tube (35) and the outer tube (36) as a a/the discharge channel (40) is formed and/or the inner tube (35) forms the feed channel (30). Gas measuring device (10) according to claim 2 or 3 , characterized in that the discharge channel (40) has at least one opening (41, 43), the discharge channel (40) being positioned in the exhaust pipe (100) in such a way that the exhaust gas flowing in the exhaust pipe (100) flows through the opening (41, 43) flows. Gas measuring device (10) according to one of the preceding claims, characterized in that in the feed duct (30) there is an element which cleans and/or conditions the partial exhaust gas flow, in particular at least one particle filter (70) and/or at least one catalytic converter and/or at least a device for adjusting the temperature of the partial exhaust gas flow and/or at least one dosing device for gas and/or aerosol. Gas measuring device (10) according to one of the preceding claims, characterized by a sleeve (60) with an external thread (61) and/or a ring with an external thread for connecting the housing (20) to the exhaust pipe (100), the sleeve (60) and/or the ring is preferably formed on the feed channel (30). Gas measuring device (10) according to one of the preceding claims, characterized in that the NOx sensor (50), in particular an NO ₂ sensor, comprises a heating element (53). Gas measuring method using a gas measuring device (10) according to one of Claims 1 until 7 , characterized by the method steps: a) deriving a partial exhaust gas stream of the exhaust gas from the exhaust pipe (100) of an internal combustion engine by means of the feed channel (30); b) conducting the partial exhaust gas flow into the housing section (21) formed at least outside the exhaust gas pipe (100); c) passing the partial exhaust gas flow over the sensor (50, 50'), the partial exhaust gas flow being cooled in step b), in particular in such a way that the temperature of the partial exhaust gas flow at the sensor (50, 50') is less than 500 °C. Gas measurement method claim 8 , characterized in that between step b) and step c) the partial exhaust gas flow is cleaned and/or conditioned, in particular the partial exhaust gas flow is cleaned by means of a particle filter (70) or catalyst or additional gas and/or aerosol is added to the partial exhaust gas flow will. Gas measurement method according to one of Claims 8 until 9 , characterized by a step d) in which the partial exhaust gas stream is returned to the exhaust pipe (100) or is derived into the housing environment (101). Gas measurement method according to one of Claims 8 until 10 , characterized in that the sensor (50, 50 ') measures the concentration of gas components of the partial exhaust gas flow.

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