DE102016125354A1 - Gas measuring device and gas measuring method - Google Patents

Abstract

The invention relates to a gas measuring device (10) for measuring an exhaust gas flowing in an exhaust pipe (100) of an internal combustion engine. According to the invention, the gas measuring device comprises a housing (20) with at least one housing section (25) formed outside the exhaust pipe (100), wherein a sensor (50, 50 ') is located in the housing section (25). Furthermore, the gas measuring device (10) comprises a feed duct (30), which diverts a partial exhaust gas flow into the housing (20).

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, by targeted reduction of nitrogen, the released oxygen is determined. This is possible in particular with the aid of an oxygen-ion-conducting material which is operated in the amperometric measuring method. Such sensors consist of several multilayer cofired ZrO ₂ layers. However, these sensors have several disadvantages. In particular, the detection limit of such sensors is 100 ppm for NO ₂ . Therefore, from today's perspective, such sensors are too inaccurate for exhaust emission tests. Another disadvantage is that the individual ceramic layers of such sensors must be manufactured individually and the sensors are therefore extremely expensive. Such sensors can not be used nationwide in vehicles with internal combustion engines at a sensor price of 70 - 90 EUR per sensor.

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

The invention is based on the object to provide a further developed gas measuring device, which allows a 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 is to be made possible. Furthermore, it is an object of the present invention to provide 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 measuring method, the object is achieved by the features of claim 11.

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, wherein the gas measuring device comprises a housing with at least one housing section formed outside the exhaust pipe, wherein a sensor is located in the housing section. Furthermore, the gas measuring device comprises a supply channel, which discharges a partial exhaust gas flow into the housing. In other words, a part of the exhaust gas flowing through the exhaust pipe is branched out of the exhaust pipe and discharged into the housing, in particular in the housing section formed outside the exhaust pipe.

The supply duct is preferably designed as a pitot tube or as a dead water pipe. The pitot tube may in particular be a pitot tube. As Pitotrohr is not to be understood in the following a back pressure sensor. Rather, the shape of the pipe is crucial. The supply duct serves to guide a partial exhaust gas flow of the exhaust gas flowing in the exhaust pipe into the housing, in particular into the housing section formed outside the exhaust pipe.

Preferably, the partial exhaust gas stream is cooled from the inlet of the exhaust pipe until reaching the sensor. Therefore, it is possible to use a gas measuring device with known nitrogen oxide sensors based on oxide semiconductor layers. The supply duct, in particular the pitot tube or the dead water pipe, serve to ensure that a constant proportion of the exhaust gas, namely a constant partial exhaust gas flow, is always conducted into the housing section. The supply channel can form a kind of bypass together with the housing.

The housing may be formed completely outside the exhaust pipe in one embodiment of the invention. In such an embodiment, only a portion of the supply duct and / or a portion of a supply duct and a discharge duct is / are at least partially within the exhaust pipe.

The gas sensing device may further include a drainage channel that provides fluid communication from the interior of the housing to the exhaust tube and / or housing environment. Accordingly, it is possible that the partial exhaust gas stream after it has flowed over the sensor, either directly into the housing environment and / or is returned via the discharge channel in the exhaust pipe. By suitable management of the partial exhaust gas flow, it is possible to avoid dead water areas in order to enable a fast response time of the sensor.

The discharge channel may be formed periskop-shaped in one embodiment. Accordingly, such a supply duct initially comprises a bent portion, which is preferably aligned counter to the flow direction of the exhaust gas. In other words, the inlet opening of the exhaust pipe is arranged counter to the flow direction in the exhaust pipe. At the bent portion of the supply passage is preferably followed by a 90 ° angled line section. 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 output port is for fluid communication of the supply passage with the housing.

In one embodiment of the invention, the discharge channel may be formed as a pipe separate from the feed channel. In particular, it is possible that the discharge channel is formed in a vertical extension to the feed channel. Such an embodiment of the discharge channel is used for fluid communication from the housing interior to the housing environment. Furthermore, it is possible that the discharge channel is formed mirror-symmetrically to the supply duct. Accordingly, the discharge channel can also be formed periscope-shaped, wherein the bent portion of the discharge channel is aligned in the flow direction of the exhaust gas in the exhaust pipe. The line sections of the discharge channel and the supply channel can run parallel to each other in such an embodiment.

In a further embodiment of the invention, the gas measuring device may comprise a double-walled tube with an inner tube and an outer tube. Preferably, a gap formed between the inner tube and the outer tube is formed as a discharge channel (s). The inner tube is preferably formed in such an embodiment as a feed channel. The feed channel and the discharge channel are preferably dimensioned such that their flow resistances are similar to each other.

The outlet opening of a discharge channel is preferably oriented in the direction of the flow direction of the exhaust gas in such a way that a negative pressure is created in the discharge channel. Even when training with a double-walled pipe, this principle is realized. Preferably, the outer tube has a plurality of openings, in particular a plurality of slot-shaped openings. Under the pitot tube is understood in the present example, an angled pipe, the inlet opening opposes the incoming exhaust gas, while the outlet opening is either outside of the exhaust stream or oriented parallel to the exhaust stream. 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 the exhaust tube.

In a further embodiment of the invention, the discharge channel may have at least one opening, wherein the discharge channel is positioned in the exhaust pipe such that the exhaust gas flowing in the exhaust pipe flows through the opening. If the supply duct is designed as a dead water pipe, the partial exhaust gas flow passes through diffusion into the housing section formed outside the exhaust pipe.

In a further embodiment of the invention may be formed in the supply duct, a part of the exhaust gas stream cleaning and / or conditioning element. An element which purifies the partial exhaust gas flow may in particular be a particle filter and / or a catalyst. Furthermore, it is possible that a device for temperature adjustment of the partial exhaust gas flow is formed in the supply passage. As a part of the exhaust gas flow conditioning element, for example, the formation of a metering device for gases and / or aerosols is possible.

Preferably, the gas measuring device comprises at least one sleeve with an external thread and / or a ring with an external thread, wherein the sleeve and / or ring are formed for connecting the housing to the exhaust pipe. In a particularly preferred embodiment, the sleeve and / or the ring are formed on the feed channel. In the construction of the gas measuring device with a sleeve thus described and / or a ring thus described, it is possible to introduce the gas measuring device in the sense of a Einschraubfühlers in the exhaust pipe.

Furthermore, it is possible that the gas-measuring device has a, preferably annular, mounting flange. This mounting flange may be attached to the exhaust pipe.

The sensor located in the housing of the gas measuring device may be a gas mass flow sensor and / or a gas sensor and / or a temperature sensor. Particularly preferably, the sensor is a NOx sensor. In an extremely 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 having a plurality of different sensors.

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.

If the gas measuring device has a NOx sensor, in particular a NO ₂ sensor, this sensor comprises:

1. a) a ceramic substrate,
2. b) an applied on the substrate oxide semiconductor layer, 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 oxide semiconductor layer. The oxide semiconductor layer is preferably a tungsten trioxide layer. Furthermore, it is possible that the oxide semiconductor layer has manganese oxide (MnO, Mn ₂ O ₃ ). The use of other metal oxides is possible.

Furthermore, the sensor, in particular the NOx sensor, in particular the NO ₂ sensor, may comprise a heating element. The heating element is preferably located on the opposite side of the substrate to the oxide semiconductor layer. Furthermore, it is possible for a porous cover ceramic to be applied to the oxide semiconductor layer. This cover ceramic protects the oxide semiconductor layer.

The electrodes described under c) are preferably two intermeshing comb electrodes. Such electrodes can be applied to the ceramic substrate by screen printing, for example. Preferably, the at least two electrodes are made of platinum. Subsequently, the (comb) electrodes are coated with the oxide semiconductor layer. The application of the oxide semiconductor layer can be carried out by screen printing or by RF sputtering. Following this, the described heating element, in particular the heating resistor can be applied to the still free side of the substrate. The heating resistor may for example consist of platinum. 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 oxide semiconductor layer with a further gas-permeable protective layer. This layer may for example consist of manganese dioxide (MnO ₂ ). The additional gas-permeable protective layer serves in particular to prevent contamination by foreign gases.

Overall, it should be noted 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 nitric oxide sensors have a high sensitivity of 0 - 100 ppm. The derivation according to the invention of a partial exhaust gas flow into a housing section formed outside the exhaust pipe leads to fast response times of the sensor. This is desired, for example, during rapid load changes of the internal combustion engine. This is due to the fact that the partial exhaust gas flow through the sensor is guided directly and continuously 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 measuring method is characterized by the following method steps:

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

In step b), the partial exhaust gas stream is preferably cooled. The cooling of the partial exhaust gas flow takes place in such a way 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 stream according to the invention, it is possible in particular to use a sensor based on an oxide semiconductor layer.

Between step b) and step c), the partial exhaust gas stream can be cleaned and / or conditioned. Preferably, the partial exhaust gas stream is purified by means of a particulate filter or by means of a catalyst. Furthermore, it is possible that further gas and / or aerosol is added to the partial exhaust gas flow. By adding further gas or aerosol, the partial exhaust gas flow can be conditioned.

The gas metering method may include a step d) in which partial exhaust gas flow is returned to the exhaust pipe or drained into the housing environment.

Preferably, the gas measuring method and the gas measuring device are designed such that the sensor is a gas sensor is that measures the concentration of gas constituents of the partial exhaust gas stream.

The invention will be explained in more detail by means of 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.

Hereinafter, like reference numerals are used for like and equivalent parts.

In 1 is a gas measuring device according to the invention 10 for measuring one in an exhaust pipe 100 (shown schematically) of an internal combustion engine flowing exhaust gas. The gas measuring device 10 further includes a housing 20 , In the illustrated embodiment, the complete housing 20 outside the exhaust pipe 100 educated. In further embodiments, it is also possible that only a housing portion outside of the exhaust pipe 100 is trained.

The gas measuring device 10 further comprises a supply duct 30 that has a partial exhaust flow into the housing 20 derives. The supply duct 30 is designed as a pitot tube. This includes a first angled section 31 and a 90 ° projecting line section 32 , In the angled section 31 is the entrance opening 33 of the supply duct 30 educated. The entrance opening 33 is opposite to the flow direction S oriented to the exhaust gas. The exit opening 34 of the supply duct 30 is outside the exhaust pipe 100 educated. Due to the pressure difference between the inlet opening 33 and the exit port 34 it comes in the supply channel 30 to a separate fluid flow. In this fluid flow, a partial exhaust gas flow flows in the direction of the housing 20 ,

The partial exhaust gas flow may be in the housing 20 directly to the sensor 50 be directed. Preferably, the temperature is within the housing 20 maximum 300 ° C. By arranging a filter 70 in the supply duct 30 In addition to the cooling of the partial exhaust gas flow, a cleaning is effected. Accordingly, inside the case 20 a clean gas space formed.

The sensor 50 in the example shown, consists of a ceramic substrate 51 on the substrate 51 applied oxide semiconductor layer 52 and at least two electrodes electrically contacted with the semiconductor layer. Preferably, the sensor is 50 to a NOx sensor, in particular a NO ₂ sensor. On the back of the substrate 51 may be formed a heating element, in particular a heating resistor. Above the oxide semiconductor layer 52 is furthermore a porous cover ceramic 54 educated.

After flowing around the sensor 50 with the partial exhaust gas flow, the partial exhaust gas flow through the discharge channel 40 to the exhaust pipe 100 directed. The discharge channel 40 thus provides a fluid connection from the housing interior 21 to the exhaust pipe 100 ago. In the present embodiment, the gas measuring device 10 a double-walled pipe 15 with an inner tube 35 and an outer tube 36 on. The between the inner tube 35 and the outer tube 36 formed gap is present as a drainage channel 40 educated. The supply duct 30 is, however, by the inner tube 35 educated.

The discharge channel 40 has several openings 41 on, through which the partial exhaust gas flow into the exhaust pipe 100 can escape. The openings 41 are preferably in the outer tube 36 formed or arranged that the exhaust gas flow S over the openings 41 flows. This creates a pressure gradient between the openings 41 of the outer tube 36 and the housing section 25 from and there is a flow of fluid from the housing section 25 in the exhaust stream.

The gas measuring device 10 further comprises a sleeve 60 with an external thread 61 , The sleeve 60 further comprises a flange portion 62 , The flange section 62 lies on the exhaust pipe 100 on. With the help of external thread 61 can the sleeve 60 in the exhaust pipe 100 be screwed.

In 2 is schematically an exhaust pipe 100 with a gas measuring device according to the invention 10 displayed. This figure shows schematically that the gas measuring device 10 two separate tubes, namely a supply channel 30 and a drainage channel 40 may include. The gas measuring device 10 is designed in the sense of a bypass. That is, a partial exhaust gas flow is from the exhaust pipe 100 diverted flowing exhaust gas, by means of the supply duct 30 in the case 20 and to the inside of the case 21 trained sensor 50 directed. Subsequently, the partial exhaust gas flow is again in the exhaust pipe 100 fed. Even with this construction, the partial exhaust gas flow is advantageously cooled below 400 ° C, before this on the sensor 50 meets.

In 2 is further indicated that a plurality of sensors, namely a NO ₂ sensor 50 and a NOx sensor 50 'inside the housing 21 can be trained.

In 3 is another embodiment of the gas measuring device 10 shown. Also the supply channel shown there 30 has an angled section 31 and a vertical line section 32 on. The supply duct 30 ends in the case 20 in which the sensor is located 50 located. The discharge channel 40 , in particular the entrance opening 42 , is in vertical extension to the supply duct 30 educated. The discharge channel 40 serves for fluid connection from the inside of the housing 21 to the housing environment 101 , The exit opening 43 of the discharge pipe 40 is therefore formed in the housing environment 101.

In 4 is another embodiment of a gas measuring device 10 shown. The supply duct 30 and the drainage channel 40 are essentially mirror-symmetrical to each other. Accordingly, both channels have 30 and 40 each angled section 31 and 44 and a line section 32 and 45 on. Both line sections 32 and 45 are in a protective sleeve 75 located. It can be seen that the entrance opening 42 of the discharge channel 40 in horizontal extension to the exit opening 34 of the supply duct 30 is trained. In order to allow such an arrangement of the openings 33 and 42, both the supply duct 30 as well as the discharge channel 40 each a bending section 37 and 47 on.

In 5 is a gas measuring device 10 with a housing 20 shown, with the housing 20 completely outside the exhaust pipe 100 located. Inside the case 21 again is the sensor 50 , By means of a line 55 can be the measured values of the sensor 50 be transmitted. The axial end section 39 of the supply duct 30 is in the housing interior 21 introduced. In the example shown, the supply channel 30 and the drainage channel 40 formed as a single component. The tube is designed as a dead water pipe. The partial exhaust gas flow does not reach the sensor by direct conduction 50 , Rather, a partial exhaust gas flow passes through the diffusion in the exhaust pipe 100 flowing exhaust gas to the sensor 50 , For this purpose, the tube 30 respectively. 40 a trumpet-like opening section 38 on. The entrance opening 33 respectively. 43 is in the exhaust pipe 100 positioned that in the exhaust pipe 100 flowing exhaust gas over the opening 33 respectively. 43 flows away.

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

Furthermore, it is not the complete case 20 formed outside of the exhaust pipe 100 but only the housing portion 25 , In this housing section 25 is the sensor 50 located. In the example shown are several supply channels 30 educated. These are formed as openings in the housing 20. Preferably, several rows of feed channels 30 educated. The discharge channel 40 is inside the case 20 educated. The housing 20 In other words, it is concentric with the discharge channel 40 educated. The exit opening 43 is as an opening in the front side 26 of the housing 20 educated. As in this example, the sensor 50 outside the exhaust pipe 100 is formed, the partial exhaust gas flow is on the way from the supply ducts 30 to the sensor 50 cooled.

LIST OF REFERENCE NUMBERS

10

Gas-measuring device

15

Double walled pipe

20

casing

21

housing interior

25

housing section

26

front

30

supply channel

31

Angled section

32

line section

33

entrance opening

34

output port

35

inner tube

36

outer tube

37

flexure

38

opening section

39

end

40

Waterway

41

opening

42

entrance opening

43

output port

44

Angled section

45

line section

47

flexure

50, 50 '

sensor

51

substratum

52

Oxidic semiconductor layer

53

heating element

54

covering

55

management

60

shell

61

external thread

62

flange

65

mounting flange

70

filter

75

protective sleeve

100

exhaust pipe

101

housing environment

S

Flow direction exhaust gas

Claims (15)

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) having at least one housing section (25) formed outside the exhaust pipe (100), in which a sensor (50) is located wherein the gas measuring device (10) comprises at least one supply passage (30), which discharges a partial exhaust gas flow into the housing (20). Gas measuring device (10) after Claim 1 , characterized in that the supply channel (30) is a pitot tube, in particular a pitot tube, or a dead water pipe. Gas measuring device (10) after Claim 1 or 2 characterized by a drain passage (40) providing fluid communication from the interior of the housing (21) to the exhaust pipe (100) and / or the housing environment (101). Gas measuring device (10) according to any one of the preceding claims, characterized by a double-walled tube (15) having an inner tube (35) and an outer tube (36), wherein a gap formed between the inner tube (35) and the outer tube (36) one / the discharge channel (40) is formed and / or the inner tube (35) forms the supply channel (30). Gas measuring device (10) after Claim 3 or 4 , characterized in that the discharge channel (40) has at least one opening (41, 43), wherein the discharge channel (40) is positioned in the exhaust pipe (100) such that the exhaust gas flowing in the exhaust pipe (100) via the opening (41, 43) flows. Gas-measuring device (10) according to any one of the preceding claims, characterized in that in the feed channel (40) a partial exhaust gas flow-cleaning and / or conditioning element, in particular at least one particulate filter (70) and / or at least one catalyst and / or at least a device for adjusting the temperature of the partial exhaust gas stream and / or at least one metering device for gas and / or aerosol is formed. Gas measuring device (10) according to any one of the preceding claims, characterized by a sleeve (60) having an external thread (61) and / or a ring with an external thread for connecting the housing (20) with the exhaust pipe (100), wherein the sleeve (60) and / or the ring is preferably formed on the feed channel (30). Gas measuring device (10) according to any one of the preceding claims, characterized in that the sensor (50) is a gas mass flow sensor or a gas sensor, in particular a NOx sensor, particularly preferably a NO ₂ sensor. Gas measuring device (10) after Claim 8 , characterized in that the NOx sensor (50), in particular the NO ₂ sensor, a) a ceramic substrate (51), b) an applied on the substrate oxide semiconductor layer (52), in particular a tungsten trioxide layer, and c ) comprises at least two electrodes electrically contacted with the semiconductor layer (52). Gas measuring device (10) after Claim 8 or 9 , characterized in that the NOx sensor (50), in particular the NO ₂ sensor, a heating element (53). Gas measuring method using a gas measuring device (10) according to one of Claims 1 to 10 characterized by the steps of: a) diverting a partial exhaust gas flow of the exhaust gas from the exhaust pipe (100) by means of the supply duct (30); b) passing the partial exhaust gas flow into the at least outside of the exhaust pipe (100) formed housing portion (21); c) passing the partial exhaust gas flow over the sensor (50, 50 '). Gas measuring method according to Claim 11 , characterized in that in step b) the partial exhaust gas flow is cooled, in particular such that the temperature of the partial exhaust gas flow at the sensor (50, 50 ') is less than 500 ° C, in particular less than 300 ° C. Gas measuring method according to Claim 11 or 12 , characterized in that between step b) and step c) the partial exhaust gas flow is purified and / or conditioned, in particular the partial exhaust gas flow by means of particle filter (70) or catalyst is cleaned or added to the partial exhaust gas stream further gas and / or aerosol becomes. Gas measuring method according to one of Claims 11 to 13 characterized by a step d) of returning the partial exhaust gas stream into the exhaust pipe (100) or discharging it to the housing environment (101). Gas measuring method according to one of Claims 11 to 14 , characterized in that the sensor (50, 50 ') measures the concentration of gas constituents of the partial exhaust gas flow.

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