WO2018219550A1

WO2018219550A1 - Gas sensor

Info

Publication number: WO2018219550A1
Application number: PCT/EP2018/059867
Authority: WO
Inventors: Konrad MEISTER; Milan Kotynek; Karel VACHA; Simon Rentschler
Original assignee: Robert Bosch Gmbh
Priority date: 2017-05-30
Filing date: 2018-04-18
Publication date: 2018-12-06
Also published as: DE102018203389A1

Abstract

The invention relates to a gas sensor for determining at least one constituent or at least one property of a measurement gas, having a sensor element (14) which is installed in a housing (11) and has a gas-sensitive end section (141) which distally projects from the housing (11) along a longitudinal direction (78) of the gas sensor (1) and is exposed to the measurement gas, having a protective tube module (20) which covers the gas-sensitive end section (141) and is secured to the housing (11), wherein the protective tube module (20) has an inner protective tube (21) which surrounds the end section (141) with a radial and axial distance, with the result that an interior space (121) is formed between the housing (11) and the inner protective tube (21), in which interior space the gas-sensitive end section (141) is situated, wherein the protective tube module (20) has an outer protective tube (22) which surrounds the inner protective tube (21), with the result that an exterior space (122) is formed between the outer protective tube (22) and the inner protective tube (21) in the interior of the protective tube module (20). The outer protective tube (22) and the inner protective tube (21) are formed in such a manner that a bypass flow through the inner protective tube (21) is reliably formed.

Description

description

title

gas sensor

State of the art

A gas sensor for determining at least one component or at least one property of a measuring gas is already known from the prior art.

The gas sensor known from EP 0 978 721 B1 comprises a detection element with a front section; a detection section of the front portion of

Detection element is formed; and a protector covering the detection section; wherein the protector has a first portion and a second portion radially outward of the first portion, the first portion having a sidewall with a first gas inlet, the sidewall having an axial forward end and a tapered portion, of which the tapered portion is formed the axial front end of the side wall is formed; wherein at least one second side gas inlet is formed in a side wall portion of the second portion and a first gas outlet is formed in the first portion, the at least one second side gas inlet being disposed at a location radially opposite to the tapered portion; and wherein a second gas outlet is formed in the second portion, wherein the first gas outlet is formed in a front end surface of the second portion, and wherein the second gas outlet is formed in a front end surface of the second portion, wherein the tapered portion of the first portion in FIG Shape of a truncated cone is formed, which is connected to the front end of a cylindrical body. Disclosure of the invention

The present invention is based on the desire for a gas sensor that simultaneously realizes as well as possible a number of properties which were previously regarded as conflicting with one another. Thus, the sensor function and the heatability as well as the dynamics of the gas sensor should be independent of its orientation about its longitudinal axis when it is exposed to a lateral flow of sample gas. The gas sensor should also be robust to particles contained in the measurement gas, such as water droplets and / or soot particles. At the same time, however, the gas sensor should also have a high degree of dynamics, that is, it should rapidly provide a correspondingly changed signal when the concentration of the component of the measuring gas changes or when the property of the measuring gas changes.

The gas sensor according to the invention with the features of claim 1 is able to do this.

Thus, the gas sensor according to the invention has a housing, which in turn for example has a thread and an external hexagon, so that the gas sensor with its distal end ahead in a receiving socket of an exhaust tract of a

Internal combustion engine is screwed.

In the housing, a sensor element is installed. It may be, for example, a planar or rod-shaped, sintered, ceramic sensor element of a

Exhaust gas sensor, for example, an oxygen sensor or a NOx sensor or a particulate sensor, which is basically known from the prior art.

For example, the housing has an inner bore, in which the sensor element is held by a sealing device, which consists for example of steatite and / or boron nitride. The sensor element is, for example, in both longitudinal directions over the

Sealing device and over the housing over.

The sensor element has a gas-sensitive end section which has, for example, at least one electrode of an electrochemical cell or one

Interdigital electrode has. This gas-sensitive end section protrudes distally from the housing and the sealing device along the longitudinal direction of the gas sensor and is therefore exposed to the measuring gas.

The gas-sensitive end portion of the sensor element is covered with a protective tube module fixed to the housing, so that the measurement gas does not interact directly, but in a manner with the sensor element, which is defined by the geometry and arrangement of the protective tube module. The protective tube module can be fixed, for example, by a circumferential weld on the housing. The protective tube module has an inner protective tube and an outer protective tube, wherein the inner protective tube surrounds the gas-sensitive end portion of the sensor element with radial and axial distance and further encloses an inner space and wherein the

Outer protective tube surrounds the inner protective tube and also a between the

Surrounds outer protective tube and formed in the inner protective tube outside.

The outer protective tube has at least one inlet opening. In the context of this application, the at least one inlet opening is to be understood as an inlet opening, if there is only one inlet opening, alternatively all inlet openings should be understood if there are several inlet openings.

The outer protective tube also has at least one outlet opening. In the context of this application, the at least one outlet opening is to be understood to mean the one outlet opening, if there is only one outlet opening, alternatively all the outlet openings should be understood if there are several outlet openings.

The inner protective tube also has at least one inlet opening and at least one outlet opening. This is to be understood in accordance with the meaning of the above for the at least one inlet opening and the at least one outlet opening of the outer protective tube.

To determine whether an opening of the outer protective tube is an inlet opening or an outlet opening, it can be assumed in particular that the at least one outlet opening is arranged distally in the longitudinal direction of the at least one inlet opening and / or that the at least one outlet opening in the radial direction inside the at least one Inlet opening is arranged. As explained, the at least one inlet opening and / or the at least one outlet opening may each comprise a plurality of openings. The indicated relation then applies to each entrance opening with respect to each exit opening.

In order to determine whether an opening of the inner protective tube is an inlet opening or an outlet opening, the same applies in particular, mutatis mutandis. The division made in the previous paragraphs of the openings in

Inlet openings and outlet openings are in particular again which flows form in a gas sensor according to the invention, which is exposed to an outer lateral gas flow, the flow velocity in the region of the distal end of the gas sensor is greater than in a more proximal region of the gas sensor. This applies, for example, to a gas sensor, which in the receiving socket of a

Exhaust tract of an internal combustion engine is screwed in accordance with the rules, ie in particular to cut a central axis of a line of the exhaust tract.

Thus, during operation of the exhaust gas sensor according to the invention, in particular measuring gas enters through the at least one inlet opening of the outer protective tube into the protective tube module and into the outer space.

The at least one inlet opening of the outer protective tube has a swirl element, in the case of a plurality of inlet openings of the outer protective tube, in particular, each has

Inlet opening of the outer protective tube to a swirl element, so that forms a vortex around the longitudinal axis of the gas sensor in the outer space. At least part of the

Measuring gas, which can also be referred to as the main flow, thus follows the vortex to the at least one outlet opening of the outer protective tube, where it leaves the protective tube module. Any massive particles present in the exhaust, such as

Water droplets and / or soot are transported in this way along the outer protective tube in the distal direction to the outlet opening of the outer protective tube and there from the

Protective tube module eliminated without ever interacting in a potentially damaging manner with the gas-sensitive end portion of the sensor element.

The vortex formed around the longitudinal axis of the gas sensor moreover has the effect that a static pressure is lower in its interior than in its outer regions. In the present case, this causes in particular a pressure gradient, according to a relative overpressure in the region of the inlet openings of the inner protective tube and a relative negative pressure in the region of the outlet opening of the inner protective tube. The pressure gradient in particular drives a corresponding flow through the inner protective tube, which conveys measuring gas to the gas-sensitive end section of the sensor element. This flow through the inner protective tube in particular represents a bypass flow to the main flow, which branches off from the main flow in the outer space after a, in particular comparatively short, flow path to the gas-sensitive end section of the sensor element and, after flowing through the inner space and re-entry into the outer space

especially reunited with the mainstream. It has thus been recognized according to the invention that the formation of the vortex in the outer space is able to produce the advantageous effects described above.

It has also been recognized according to the invention that these effects become more pronounced the more undisturbed the vortex can form in the outer space, i. the less the turbulence in the outer space is decelerated by friction on the protective tube module or by flow obstacles.

It is therefore proposed according to the invention that the outer space projects beyond the housing distally in the longitudinal direction by an outer longitudinal extension and that the

Interior the housing protrudes distally in the longitudinal direction by an interior longitudinal extent and that the external longitudinal extent is at least twice as large as the interior longitudinal extent. The result is a correspondingly large extent of the outer space, in which the turbulence undisturbed by the inner protective tube can form freely and largely unhindered.

In contrast, it comes in the known from the prior art gas sensor, which does not have the features essential to the invention and in which the at least one second side gas inlet is disposed at a location radially opposite the tapered portion, substantially only for the formation of a rotating gap flow with correspondingly high friction losses.

In other words, in particular according to the invention, it is therefore proposed that the eddy formed in the outer space through a flow through the inner protective tube

Forming a static pressure gradient between the inlet opening of the

Inner protective tube and the outlet opening of the inner protective tube drives and in the

Exterior space formed vortex is formed predominantly in a spatial area of the exterior space, which, viewed from the interior of the entire housing in

Longitudinally opposite.

The formation of the vortex is supported by the arrangement of the openings of the inner protective tube and the outer protective tube, when all openings of the outer protective tube, so the at least one inlet opening and the at least one outlet opening of the

Outer protective tube, distal of all openings of the inner protective tube, ie distal of the at least one inlet opening and distal of the at least one outlet opening of the inner protective tube, are arranged.

The inlet openings of the outer protective tube can by a plurality of

Be given in the same height in the longitudinal direction on a

Cloak surface of the outer protective tube can be arranged. They can thus form a perforated ring, in which the openings are arranged at equal distances to their nearest neighbors. For example, six or eight openings may be provided. It can be provided that each inlet opening has a swirl element, in particular a swirl flap.

The swirl flaps can be made by creating a straight cut in the outer protective tube and then pressing in or pushing out the portion of the outer protective tube adjacent to the cut. Preferably, the swirl flaps have a shape such that a flow entering the outer protective tube essentially rests only tangentially on the outer protective tube and a radial flow component is only slight. This can be achieved in that the swirl flaps, viewed from the outside, are convexly shaped in a first area spaced from the intersection and are concave in a second area facing the intersection. The formation of a strong vortex in the outer protective tube can be maximized by aligning the swirl flap or the swirl flaps in the tangential direction, i.e., the swirl flap. initially impart no velocity component to the distal direction of the incoming flow. It may be advantageous for the inner protective tube to be arranged closely on the sensor element. In particular, with a heated sensor element and compared to cool exhaust gas, the inner protective tube heats up in this way particularly strong and as a result, there is a reduced input of soot in the inner protective tube due to

thermophoretic effect. The close concern can be quantitatively expressed in that the distance in the longitudinal direction of the gas-sensitive end section in the

Inner protective tube is not more than 15% of the external longitudinal extent.

The vortex in the outer space can be formed even better if the outer protective tube is frusto-conical in its distal end region, for example in a distal end region whose extent in the longitudinal direction is not less than 5% and not more than 15% of the outer longitudinal extension, frustoconical runs and / or runs in such a frusto-conical shape that half the opening angle of the associated cone is 30 ° to 60 °.

It can be provided that the at least one outlet opening of the outer protective tube is a plurality of outlet openings, which at one at the distal end of the

Outer protective tube arranged bottom are arranged eccentrically and are designed as slots whose extension in the tangential direction is greater than in the radial direction, in particular at least 50% greater than in the radial direction. In this case, the swirling flow can move the outside space through the outlet openings of the

Leave outer protective tube with reduced flow resistance.

It can be provided that the at least one inlet opening of the inner protective tube has at least one swirl element for forming a further swirl around the longitudinal direction in the interior

In the case of several inlet openings of the inner protective tube, in particular, each

Inlet opening of the outer protective tube to a swirl element, so that reliably forms in the interior of the further vortex around the longitudinal axis of the gas sensor. It can be provided that the swirl element of the inlet opening of the outer protective tube and the swirl element of the inlet opening of the inner protective tube in each other

have opposite tangential directions, or at least each have a component in opposite tangential directions, so that the vortex and the other vertebra are oriented opposite to each other. As a result, the measuring gas undergoes a sudden deflection of up to 180 ° when entering the inner protective tube, which can not follow any massive particles present in the exhaust gas, such as drops of water and / or soot, as a result of inertia. These particles thus remain in the outer space arranged between the inner protective tube and the outer protective tube and can therefore not damage the sensor element. Only measurement gas that has been cleaned of massive particles, such as water drops and / or soot, reaches the sensor element.

The effect occurs particularly reliable when all the twist elements of all

Entrance openings of the outer protective tube to all swirl elements of all inlet openings of the inner protective tube in opposite tangential directions have, or at least one component in each case opposite tangential

Have directions, so that the vortex and the other vertebra in opposite directions are oriented.

A swirl element of an inlet opening of the outer protective tube or of the inner protective tube, in the sense of the application in the direction in which sample gas passes through the inlet opening, through the swirl element, enters the outer space or the inner space.

In order to flow through the interior efficiently, it can be provided that the swirl element of the inlet opening of the inner protective tube has a component in the axial direction facing the housing, so that it enters the interior

Flow imparts a component in the axial direction facing the housing.

If the volume of the interior distally overhanging the housing in the longitudinal direction has the shape of a straight circular cylinder whose diameter is greater than its height, this is a particularly flat area. In particular in

Cooperation with the above-described pressure conditions in the interior and in the outer space and in particular in conjunction with the above-described

Orientation of the swirl elements leads to a flow through the interior with high dynamics. As explained above, a vortex forms around the longitudinal axis of the outer space

Gas sensors off. While this vortex, as explained above, in the region of the outer space, which is distal to the interior, due to the features of the invention can form particularly undisturbed, occurs in the region of the outer space, on the proximal, ie the housing facing side of the Entry opening of the

Outside protection tube is, in particular in a region of the outer space, which is formed as located between the outer protective tube and the inner protective tube annular gap, increased friction on the protective tube module. The flow is therefore potentially disturbed in this area and the formation of the vortex is also potentially disturbed. In the case where it comes only reduced to the formation of a total uniform vortex in the specified area of the outer space, there is the

Reduced flow rate and increased a corresponding static pressure. The mechanism explained above, which drives the flow through the interior, is consequently less effective.

By means of the further education measure that the outer protective tube in an axial between the at least one inlet opening of the outer protective tube and the housing

arranged region and / or at the axial height of an annular gap formed between the outer protective tube and the inner protective tube has at least one elongated embossment facing in the proximal longitudinal direction in the direction of the vortex, the formation of a uniform vortex around the longitudinal axis of the gas sensor in this region of the outer space supported. As a result, there the flow velocity is high and a corresponding static pressure is low. The above explained

Mechanism which effects the separation of water from the exhaust gas reaching the sensor element is therefore particularly effective.

An embossing of the outer protective tube is understood in particular to mean a structure which is formed at least on the inner surface of the outer protective tube and bulges there in a radially inward direction. It can be produced in particular by embossing an outer protective tube made of sheet metal from outside to inside. Of course, in the present case, alternative production methods for producing the embossment are possible. The embossing is thus able to interact in particular with a flow in the outer space.

An elongated embossing of the outer protective tube is understood in particular to mean a structure which extends further in a longitudinal extent than in a transverse extent, for example at least twice or at least three times. The embossment is thus able to stabilize in particular a flow in its longitudinal direction in the outer space.

The oblong embossment points in the direction of its longitudinal extent. If it is viewed in the proximal longitudinal direction (ie in the direction of the housing) in the direction of the vortex formed in the outer space, it supports and stabilizes it and overall improves the sensor functionalities explained at the outset.

The elongated embossing can be formed straight on the outer protective tube, so in total lie in a spatial plane. The oblong embossment (or this spatial plane) can be arranged, for example, with the longitudinal axis of the sensor at an angle of 45 °, or at an angle which is 30 ° to 60 °.

The elongated embossment may alternatively have a curved course instead of a straight course. The specified angles then relate

sections on tangents to the embossment. It is provided in particular that the at least one elongated embossment in

Is arranged longitudinally between the at least one inlet opening of the outer protective tube and the housing. There is thus, in particular along the outer protective tube, no direct, straight-line connection between the at least one inlet opening of the outer protective tube and the housing. The interaction between flow and embossing is intensified in this case and a direct transport of water droplets to the inlet opening of the inner protective tube is prevented. It is in particular proceed that the at least one inlet opening consists of a plurality of inlet openings, which are arranged along the circumference of the outer protective tube on a perforated ring with the same distance from each other and each associated with an elongated embossment, so that the respective elongated embossment in

Longitudinal direction between the respective inlet opening of the outer protective tube and the housing is arranged. The interaction between flow and stamping is intensified in this case.

A protrusion of the embossment into the outer space is quantitatively expressed by the measure V. It indicates the shape deviation of the outer protective tube radially inward in the region of the embossment.

One or more of the following lower bounds for V are contemplated: 0.3mm 0.5mm, 1mm, 2mm; 0.5 * sheet thickness of the outer protective tube, sheet thickness of the

Outer protective tube, 2 * plate thickness of outer protective tube; 4 * sheet thickness of

Outer protective tube; 1% of the external longitudinal extent, 2% of the external space

External longitudinal extent, 4% of the external longitudinal extent, 7% of

Exterior length.

One or more of the following lower barriers for the longitudinal extent of the elongated embossment are contemplated: 3mm, 5mm, 10mm, 20mm; 5 * sheet thickness of outer protective tube, 10 * sheet thickness of outer protective tube, 20 * sheet thickness of

Outer protective tube; 40 * sheet thickness of the outer protective tube; 10% of

External longitudinal extent, 20% of the external longitudinal extent, 30% of the external longitudinal extent

Exterior length. Other developments of the invention are also subject of the dependent claims and the embodiment.

Brief description of the drawings

The invention is explained in more detail in the following description with reference to the embodiment shown in the drawings. It shows:

1 shows a detail of a longitudinal section through a first invention

Gas sensor,

2a, 2b are views of the inner protective tube of the gas sensor of Figure 1,

3a, 3b are views of the outer protective tube of the gas sensor of Figure 1,

Fig. 4 shows the gas sensor of Figure 1 when properly installed in a

Exhaust pipe

FIG. 5 schematically shows the gas flows forming in the protective tube module of the gas sensor from FIG. 1 when properly installed according to FIG

FIG. 4,

6a-d are schematic drawings for explaining the present invention, Fig. 7 is an external view of a second gas sensor according to the invention,

8 shows a detail of a longitudinal section through the gas sensor of Figure 7,

9 is an external view of a third gas sensor according to the invention.

Ausführbeispiele

FIG. 1 shows a gas sensor according to the invention, for example a lambda probe. The gas sensor has a housing 11. In the housing 11 is a ceramic

Sensor element 14 defined by a seal 15, which consists for example of steatite and / or boron nitride. From the seal 15 and the housing 11 is a Gas-sensitive end portion 141 of the sensor element 14 along a longitudinal direction 78 of the gas sensor 1 distally forth and is exposed to a sample gas. On the housing 11, a protective tube module 20 is fixed by welding, so that it covers the gas-sensitive end portion 141.

The protective tube module 20 has an inner protective tube 21 and an outer protective tube 22.

The inner protective tube 21 encloses the gas-sensitive end portion 141 with radial and axial distance. Between the inner protective tube 21 and the housing 11, an inner space 121 is thus formed, in which the gas-sensitive end portion 141 is located. The distance a between sensor element 14 and inner protective tube 21 in the axial direction is only 2 mm in the example, so that the inner protective tube 21 also heats up when the sensor element 14 is heated, which has the advantage that a deposit of particles,

For example, soot particles, is suppressed on the inner protective tube 21 or on the sensor element 14 by thermophoresis.

The interior 121 projects beyond the housing 11 distally in the longitudinal direction 78 by one

Interior longitudinal extension Im, which in this example is 6 mm. The space region 121 'of the interior 121 projecting distally over the housing 11 in the longitudinal direction 78 has the shape of a straight circular cylinder whose diameter d is greater than its height H, in the example about 60% larger.

The inner protective tube 21 has on its lateral surface 213 a perforated ring of

For example, 8 inlet openings 211, which are arranged at the same axial height and at equal distances from each other and are not projected by the gas-sensitive end portion 141 in the longitudinal direction 78 distally.

The inlet openings 211 have swirl elements 211a, the orientation of which has a tangential component and additionally a component in the axial direction facing the housing 11. The swirl elements 211a thus have in Figure 1 obliquely downwards. The swirl elements 211a are, for example, by creating a straight cut in the

Inner protective tube 21 and subsequent impressions of the adjacent section

Area of the inner protective tube 21 made. The swirl flaps 211a are convexly shaped in the portion spaced from the cut and concave in the section facing the cut, respectively, as viewed from outside the inner protective tube 21 on the swirl flap 211a. The inner protective tube 21 has a plurality of outlet openings 212 on its end face formed as a bottom 214, which forms its distal end. The outer protective tube 22 encloses the inner protective tube 21, so that between the

Outside protection tube 22 and in the inner protective tube 21 in the interior of the protective tube module 20, an outer space 122 is formed. The outer protective tube 22 has in Example 8

Inlet openings 221 which are arranged on the lateral surface 223 of the outer protective tube 22 at the same axial height and at equal distances from each other on a perforated ring. The inlet openings 221 are distal in the longitudinal direction

Inner protective tube 21 is arranged.

The inlet openings 221 have swirl elements 221a which point in the tangential direction. The swirl elements 221a are produced, for example, by producing a straight cut in the outer protective tube 22 and then pressing in the region of the outer protective tube 22 adjacent to the cut. The swirl flaps 221a are convexly shaped in the portion spaced from the cut and concave in the cut-facing portion, as viewed from the outside, respectively

Outer protective tube 22 on the swirl flap 221 a.

The outer protective tube 22 has a multiplicity of outlet openings 222, which are arranged eccentrically on a bottom 224 arranged at the distal end of the outer protective tube 22 and are designed as oblong holes 222 L whose extent in the tangential direction is greater than in the radial direction, for example approximately 70% larger than in the radial direction.

The outer space 122 projects beyond the housing 11 in the longitudinal direction 78 by one

External space extension, which in the example is 21 mm. The inner protective tube 21 of the gas sensor 1 shown in FIG. 1 is shown in FIG. 2a in the perspective from bottom to top in FIG. 1 and in FIG. 2b in the perspective from left to right in FIG.

The outer protective tube 22 of the gas sensor 1 shown in FIG. 1 is shown in FIG. 3a in the perspective from bottom to top in FIG. 1 and in FIG. 3b in the perspective of FIG shown left to right in Figure 1.

Gas sensors 1 of the type in question are in particular as intended in an exhaust pipe 2, for example an internal combustion engine, mounted, in such a way that they are from the exhaust laterally, so perpendicular to the longitudinal direction 78 of the gas sensor 1, flows. Even deviations from an exactly vertical flow, for example, up to 8 ° are possible and generally well tolerated in the proposed design. Here is a flow velocity v _ou t in the area of the end hole of the

Exhaust gas sensor 1 formed outlet opening 222 of the outer protective tube 22 is greater than a flow velocity v, _n in the region of the inlet openings 221 of the

Outside protection tube 22. Such flow conditions exist, for example, when the gas sensor 1 is screwed as shown in Figure 4 with its thread IIa in the mating thread 2c of an integrated in the wall 2b of the exhaust pipe 2 receiving nozzle 2d, without thereby to intersect a central axis 2a of the exhaust pipe 2. It is preferred that the distal end of the gas sensor 1 points downwards, so that penetration of drops possibly contained in the measurement gas is reduced gravitationally. Due to the different flow velocities v _ou t, v, _n in the area of

Inlet openings 221 and the outlet opening 222 of the outer protective tube 22 forms within the outer protective tube 22 a gradient of the static pressure, which is a flow through the outer protective tube 22 from the inlet openings 221 to the

Outlets 222 drives, see Figure 5.

Due to the formation of the inlet openings 221 with swirl flaps 221 a, the measurement gas enters with a tangential velocity component in the exterior space 122. So there is a total of a vortex rotx of the sample gas around the longitudinal axis 78 of the gas sensor. The vortex rotx is indicated in FIG. 5 by a solid line. In cooperation of the vortex rotx with the flow through the outer protective tube 22, the sample gas flows along a main flow 3 on spiral paths, one of which is shown in Figure 5, from the inlet openings 221 to the outlet opening 222 of the outer protective tube. The vortex redx is predominantly in one

Space portion 122 'of the outer space 122 is formed, which is disposed completely distal to the inner space 121. The formation of the vortex rotx is therefore largely undisturbed by the inner protective tube 21. In particular, massive particles, such as soot particles and / or water droplets, pass through the outer protective tube 22 driven by the main flow 3 and from its inertia on a spiral path along the inner surface of the outer protective tube 22. At the distal end 224 of the outer protective tube 22, they exit the outlet opening 222 of the outer protective tube 22 out without ever being in a potentially damaging way with the gas sensitive

End portion 141 of the sensor element 14 to interact.

The formation of the vortex rotx in the outer space 122 has the further effect that a static pressure in its interior, near the longitudinal axis 78 of the gas sensor, is less than a static pressure in the outer region.

This results in a relative overpressure in the region of the inlet openings 211 of the inner protective tube 21 and creates a relative negative pressure in the region of

Outlet opening and 212 of the inner protective tube 21. As a result, it comes to the flow through the inner protective tube 21 by a branched off from the main flow 3

Bypass flow 4. In the interior 121, this bypass flow 4 strikes the gas-sensitive end section 141 of the sensor element 14 after a comparatively short flow path, ie after a very short time. Subsequently, the bypass flow 4 exits the outlet opening 212 of the inner protective tube 21 again into the outer space 122 and unites again with the mainstream 3.

Due to the relatively strong deflection when branching off the bypass flow 4 from the main flow 3, massive particles, such as water droplets and / or soot particles, predominantly follow the main flow 3. They thus do not reach the gas-sensitive end section 141 of the sensor element 14 in a potentially damaging manner.

Due to the swirl flaps 211a of the inlet openings 211 of the inner protective tube 21, the bypass flow 4 in the interior 121 forms a further vortex rotin, which is opposite to the vortex redx oriented. He has the technical effect of that

Measuring gas when entering the inner protective tube 21 undergoes a sudden deflection by up to 180 °, the possibly present in the exhaust gas massive particles, such as water droplets and / or soot, inertia can not follow. These particles thus remain in the outer space 122 arranged between the inner protective tube 21 and the outer protective tube 22 and can thus not damage the sensor element 14. Only measurement gas which has been cleaned of massive particles, such as water drops and / or soot, reaches the sensor element 14. FIG. 6a shows a somewhat modified gas sensor, to which reference can largely be made to what has been described above. The flows inside the protective tube module 20 are explained in principle and simplified with reference to the elementary partial flows 600 - 606.

An external flow 600 reaches the gas sensor. There is an inflow 601 through swirl flaps 221a provided with inlet openings 221 of the outer protective tube 22 in the outer space 122. There forms a vortex 602 from. In the example, this rotates in a top-down plan view in FIG. 6a in a clockwise direction. The vortex 602 corresponds to the main flow 3 shown in FIG. 5. From the vortex 602, a secondary flow 603 branches off into a region of the outer space 122 located below the inlet openings 221 of the outer protective tube 22. This area forms a radial between the

For this there is an inflow 604 in the inner protective tube 21 through the inlet openings 211 of the inner protective tube 21 into the interior 121. After interaction with the

Sensor element 14 is an outflow 605 from the interior 121 into the outer space 122 through the outlet openings 212 of the inner protective tube 21. An outflow 606 from the outer space 122 and from the protective tube module 20 out through the

Outlet openings 222 of the outer protective tube 22nd

In order to obtain the best possible separation of water droplets contained in the flow, a high quality of the vortex 602 within the protective tube module 20 can be achieved. This also applies to the secondary stream 603 branched off from the vortex 602. Ideally, it likewise rotates in an unambiguous direction as shown in FIG. 6b and thus acts like a centrifugal separator directly in front of the inlet openings 211 of FIG

Inner protective tube 21.

In practice, however, there are limitations through the manufacturing process and constraints on the geometric design of the protection tube module 20, for example, with respect to the position and orientation of the swirl flaps 221a. A high quality and directivity of the rotating flow as shown in Figure 6b is therefore not guaranteed. The result may be additional counterflow 603 'in the annulus 302 between the outer containment tube 22 and the inner containment tube 21 (see Figures 6c and 6d) and, consequently, reduced centrifugal separation. The emergence of the opposite flow 603 'in this area can now be prevented according to an embodiment of the present invention in that the

Secondary stream 603 receives a clear rotation direction predetermined by the provision of at least one elongated embossment 301, see Figure 7 and Figure 8.

In the example, the outer protective tube 22 has, in an area arranged axially between its inlet openings 221 and the housing 11, and at the axial height of the annular gap 302 elongate embossments 301, which are seen in the proximal longitudinal direction 78 (ie from top to bottom in FIG ) in the direction of the vortex 602 (ie clockwise in FIG. 8 in plan view from above). In this example, the stampings 301 are between the inlet openings 221 of the outer protective tube 22 and the

Housing 11 arranged that a direct vertical connection between them is interrupted by the stampings 301. A direct access of water droplets to the inlet openings 211 of the inner protective tube 21 is thereby prevented.

The stampings 301 shown in this example have a length of about 10 mm and a width of about 1.5 mm. They are about as deep as the sheet thickness of the

Outer protective tube 22. The embossments 301 are aligned at an angle of 45 ° to the longitudinal axis 78 of the gas sensor.

A third embodiment (Figure 9) differs in that the

Deformations in their longitudinal direction not straight, but curved.

Claims

claims

A gas sensor for determining at least one component or at least one property of a measuring gas, in particular an exhaust gas of an internal combustion engine, with a sensor element (14) installed in a housing (11), which extends from the housing (11) along a longitudinal direction (78) of the Gas sensor (1) distally projecting, gas-sensitive end portion (141) exposed to the measurement gas, with a gas-sensitive end portion (141) covering, fixed to the housing (11)

Protective tube module (20), wherein the protective tube module (20) has an inner protective tube (21) enclosing the radial and axial distance end section (141), so that an inner space (121) is formed between the housing (11) and the inner protective tube (21). in which the gas-sensitive end portion (141) is located, wherein the protective tube module (20) has an outer protective tube (22) enclosing the inner protective tube (21), such that between the outer protective tube (22) and the inner protective tube

(21) in the interior of the protective tube module (20) an outer space (122) is formed, wherein the outer protective tube (22) at least one inlet opening (221) for the entry of sample gas into the outer space (121), wherein the at least one inlet opening (221) of the outer protective tube (22) has at least one swirl element (221a) for forming a vortex (rotx) about the longitudinal direction (78) in the outer space (122) and the outer protective tube (22) also has at least one outlet opening (222) for exiting sample gas from the Outer space (122) out of the protective tube module (20) out, wherein the inner protective tube (21) has at least one inlet opening (211) for the entry of sample gas from the outer space (122) in the interior (121) and also at least one outlet opening (212) to the exit of sample gas from the

Interior space (121) in the outer space (122), characterized in that the outer space (122) the housing (11) in the longitudinal direction (78) to a

External longitudinal extension (l _ex ) protrudes distally and that the interior (121) the housing (11) in the longitudinal direction (78) by an interior longitudinal extent (Im) distally beyond and that the external longitudinal extent (l _ex ) is at least twice as large as the interior longitudinal extent (Im ).

2. Gas sensor according to claim 1, characterized in that in the outer space (121) formed vortex (rotx) a flow through the inner protective tube (21) by forming a static pressure gradient between the inlet opening (211) of the

Inner protective tube (21) and the outlet opening (212) of the inner protective tube (21) drives and the vortex (redx) formed in the outer space (122) is formed wholly or substantially predominantly in a space region (122 ') of the outer space (122) which is separated from the outer space (122)

Inner space (121) seen completely opposite the housing (11) in the longitudinal direction (78).

Gas sensor according to one of claims 1 or 2, characterized in that the at least one inlet opening (211) of the inner protective tube (21) and the at least one outlet opening (212) of the inner protective tube (21) all proximally of all the at least one inlet opening (221) of the outer protective tube (22) and the at least one

Outlet opening (222) of the outer protective tube (22) are arranged.

Gas sensor according to one of the preceding claims, characterized in that the at least one inlet opening (221) of the outer protective tube (22) by a

A plurality of on a lateral surface (223) of the outer protective tube (22) lying inlet openings (221) are formed, wherein at each of the inlet openings (221) in each case at least one swirl element (221a) is arranged.

Gas sensor according to the preceding claim, characterized in that the majority of lying on the lateral surface (223) of the outer protective tube (22)

Inlet openings (221) are arranged on the side facing away from the housing (11) in the longitudinal direction of the inner protective tube (21).

Gas sensor according to one of the preceding claims, characterized in that the at least one outlet opening (222) of the outer protective tube (22) is a plurality of outlet openings (222) which at a at the distal end (224) of the outer protective tube (22) arranged bottom (224 ) are arranged off-center and as elongated holes (222 L) are formed whose extension in the tangential direction is greater than in the radial direction, in particular at least 50% greater than in the radial direction.

Gas sensor according to one of the preceding claims, characterized in that the at least one inlet opening (211) of the inner protective tube (21) by a plurality of on a lateral surface (213) of the inner protective tube (21) lying inlet openings (211) are formed, wherein each of the inlet openings (211) at least one

Swirl element (211a) for forming a further vortex (rotin) about the longitudinal direction (78) in the inner space (121).

8. Gas sensor according to the preceding claim, characterized in that the swirl element (221a) of the inlet opening (221) of the outer protective tube (22) and the swirl elements (211a) of the inlet openings (211) of the inner protective tube (21) have mutually opposite tangential directions, so that the vortex (rotx) and the further vortex (rotin) are oriented in opposite directions.

9. Gas sensor according to one of the two preceding claims, characterized

characterized in that the swirl element (211a) of the inlet opening (211) of the

Inner protective tube (21) oriented in the direction of the housing (11) axial direction, so that it enters the interior (121) entering a flow

Component in the direction of the housing (11) facing axial direction.

10. Gas sensor according to one of the preceding claims, characterized in that the at least one outlet opening (212) of the inner protective tube (21) at the distal end (214) of the inner protective tube (21) is arranged, wherein in particular a plurality

Outlet openings (212) of the inner protective tube (21) at the distal end (214) of the

Inner protective tube (21) are arranged.

11. Gas sensor according to one of the preceding claims, characterized in that the at least one inlet opening (211) of the inner protective tube (21) by a plurality of inlet openings (211) of the inner protective tube (21) is formed, which lie at the same height in the longitudinal direction and to their nearest neighbors have the same distance. 12. Gas sensor according to one of the preceding claims, characterized in that the outer protective tube (22) in its distal end region (225) is frusto-conical, for example in a distal end region (225) whose extension in the longitudinal direction not less than 5% and not more than 15% of

Exterior longitudinal extension (l _ex ) makes, frusto-conical and / or runs in such a truncated cone that half the opening angle (ß) of the associated cone is 30 ° to 60 °.

13. Gas sensor according to one of the preceding claims, characterized in that the gas-sensitive end portion (141) the at least one inlet opening (211) of the inner protective tube (21) in the longitudinal direction (78) not completely surmounted.

14. Gas sensor according to one of the preceding claims, characterized in that the distance (a) in the longitudinal direction (78) of the gas-sensitive end portion (141) to the inner protective tube (21) is not more than 15% of the outer longitudinal extent (l _ex ).

15. Gas sensor according to one of the preceding claims, characterized in that the housing (11) in the longitudinal direction (78) distally superior space region (121 ') of the interior (121) has the shape of a straight circular cylinder (30) whose

Diameter (d) is greater than its height (H).

16. Gas sensor according to one of the preceding claims, characterized in that the outer protective tube (22) in an axially between the at least one inlet opening (221) of the outer protective tube (22) and the housing (11) arranged region, and / or at the axial height of a between the outer protective tube (22) and the

Inner protective tube (21) formed annular gap (302), at least one elongated

Has embossment (301) facing in the proximal longitudinal direction (78) in the direction of the vertebra (602, rotx).

17. Gas sensor according to the preceding claim, characterized in that the at least one inlet opening (221) consists of a plurality of inlet openings (221) which are arranged along the circumference of the outer protective tube (22) on a perforated ring with the same distance from each other and each having an elongated Be assigned embossment (301), so that the respective elongated embossment (301) in the longitudinal direction (78) between the respective inlet opening (221) of the outer protective tube (22) and the housing (11) is arranged.