WO2019223934A1

WO2019223934A1 - Gas sensor having a deflection surface on the base housing side for throttling the fluid flow

Info

Publication number: WO2019223934A1
Application number: PCT/EP2019/059287
Authority: WO
Inventors: Vojtech RUBAS; Milan Kotynek; Sebastian Schulte Am Huelse
Original assignee: Robert Bosch Gmbh
Priority date: 2018-05-24
Filing date: 2019-04-11
Publication date: 2019-11-28
Also published as: KR20210013561A; EP3803364A1; DE102018208178A1

Abstract

The invention relates to a gas sensor (10), particularly a particle sensor, for determining at least one state variable of a measuring gas, particularly the particle concentration in the exhaust of an internal combustion engine, having a base housing (12) and a protective tube module (14) arranged on the base housing, which comprises an inner protection tube (18) extending in a longitudinal direction (16), in which a sensor element (58) can be arranged, and an outer protection tube (26) enclosing the inner protection tube at least in sections, wherein measuring gas can flow in between the outer protection tube and the inner protection tube and can be deflected in a deflection region (37) in order to flow into the inner protection tube, wherein the deflection region comprises a deflection surface (42) formed by the base housing, and wherein there is a gap (50) between the deflection surface and the inner protection tube, through which the measuring gas can flow into the inner protection tube, wherein the deflection surface has the smallest distance to the inner protection tube in the longitudinal direction at the gap.

Description

description

title

GAS SENSOR WITH A BASIC HOUSING SURFACE FOR THROTTING THE FLUID FLOW

State of the art

The invention relates to a gas sensor according to the preamble of claim 1. The invention also relates to an associated protective tube module and an associated basic housing.

Gas sensors are used for example for measuring exhaust gas parameters in the exhaust system of motor vehicles. For example, lambda sensors, NOx sensors or soot particle sensors are used. The functional unit of these sensors comprises a sensor element. The sensor element is regularly surrounded by a protective tube module, which protects the sensor element against unwanted external influences and allows a targeted flow of the sensor element with sample gas.

Disclosure of the invention

The problem underlying the invention is solved by a gas sensor according to claim 1. Advantageous developments are specified in the subclaims. Features which are important for the invention can also be found in the following description and in the drawings, wherein the features, both alone and in different combinations, can be important for the invention, without being explicitly referred to again.

Consequently, a gas sensor, in particular a particle sensor, for determining at least one state variable of a measurement gas, in particular the

Particle concentration in the exhaust gas of an internal combustion engine, proposed. Of the The gas sensor comprises a base housing and a protective tube module arranged on the base housing, which comprises an inner protective tube extending in a longitudinal direction in which a sensor element can be arranged or arranged, and an outer protective tube surrounding the inner protective tube at least in some sections. In this case, measuring gas can be flowed into the protective tube module between the outer protective tube and the inner protective tube, and in a deflection region for inflow into the protective tube

Inner protective tube deflectable. The deflection area includes one of

Base housing formed deflection, wherein between the deflection and the inner protective tube, a gap is present, through the sample gas into the inner protective tube can be flowed, and wherein the deflection at the gap has the smallest distance to the inner protective tube in the longitudinal direction.

Due to the formation of the gap between the inner protective tube and the

Base housing-side deflection surface, can be achieved in an advantageous manner initially throttling the flowing into the space between the inner protective tube and outer protective fluid flow. Due to the design of the deflection surface so that these at the gap the smallest distance to

Inner protective tube, in addition, the fluid flow can be deflected in the direction of the sensor element in comparison to the prior art, so that a total of an advantageous fluid flow in the gas sensor for

Sensor element can be provided out.

Furthermore, the possibility is given by the present invention, the sensitivity of the gas sensor, for example, to soot concentrations when the gas sensor is designed as a soot particle sensor to increase.

Furthermore, it is possible to provide improved protection of the gas sensor from cooling during regeneration.

In one embodiment of the gas sensor, the deflection surface extends in cross-section obliquely to a direction orthogonal to the longitudinal direction plane. As a result of this oblique design, a particularly preferred direct deflection of the fluid flow flowing into the protective tube module towards the sensor element can be provided. It is also conceivable that the deflection is formed as a flat surface. In cross section, the deflection can therefore be formed as a straight line. This also results in a particularly advantageous direct flow of the

Sensor element.

In a further embodiment, the deflection region comprises a

Basic housing facing end portion of the outer protective tube. Of the

Deflection region can consequently be limited to one of the deflection surface and the other by the end portion of the outer protective tube. As a result, a direct flow of the sensor element can be provided comparatively easily.

In this context, it is conceivable that the outer protective tube bears against the end of the deflecting surface facing away from the gap, so that the deflecting region has a substantially triangular shape in cross section. The outer protective tube can thus form a triangular or substantially triangular recess together with the deflection surface. Consequently, can

Fluid flow in the area between outer protective tube and inner protective tube flow into the protective tube module and then be deflected in the deflection towards the gap and finally overflow the sensor element. The outer protective tube and the deflection surface therefore in particular include an angle of less than 90 °. The angle may for example be between 40 ° and 50 ° and in particular 45 °. With a design of 45 °, the deflection surface can consequently form the hypotenuse of the triangular deflection region.

It is also conceivable that the inner protective tube has an inner side, and that the base housing has an opening bounded by an inner side toward the inner protective tube, the inner side of the aperture being adjacent to the deflection surface. Through the opening, the sensor element can be inserted into the inner protective tube. The inside of the opening can consequently pass into the deflection surface at one, in particular circumferential, edge. This edge can in particular represent the smallest distance of the deflection surface in the longitudinal direction to the inner protective tube and thus together with the basic housing facing free end of the

Inner protective tube to limit the gap. Furthermore, it can be provided that the inside of the inner protective tube is arranged flush with the inside of the opening. The inside of the

Breakthrough can thus be separated over the gap in the longitudinal direction of the inside of the inner protective tube.

In this context, it is conceivable that the protective tube module has a collar-like connecting portion for connecting the inner protective tube to the outer protective tube, wherein the connecting portion has at least one opening through which the measuring gas can flow into the deflection region. The protective tube module can therefore be designed in particular in one piece. In this case, the collar-like connecting portion also the

Limit deflection area. Further, by the at least one breakthrough further throttling of the fluid flowing into the protective tube module can be provided before the additional throttling through the gap. This results in a particularly advantageous flow guidance in the gas sensor to the sensor element.

We also suggest that the inner protective tube with the outer protective tube firmly bonded, in particular welded, is. It is in particular conceivable that the end region facing away from the base housing

Inner protective tube extends beyond the outer protective tube in the longitudinal direction. On the base housing facing away from the free end of the outer protective tube, the inner protective tube may be welded to the inner protective tube.

It is also conceivable that the protective tube module is materially connected to the basic housing, in particular welded, is. This results in a particularly stable and durable connection between the thermowell module and the base housing.

The problem underlying the invention is also solved by a basic housing for a gas sensor according to the invention. Additionally or alternatively, the problem underlying the invention is also solved by a protective tube module for a gas sensor according to the invention. Such a basic housing can therefore in particular comprise a deflection surface. In cooperation with the thermowell module can by the formation of a Gaps are provided a throttling and in particular also a particularly advantageous fluid supply to the sensor element.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are explained with reference to the drawing.

Show it:

Figure 1 Schematic cross section through a basic housing with it

arranged protective tube module of a gas sensor according to one embodiment;

FIG. 2 shows a detail of the protective tube module according to FIG. 1;

FIG. 3 shows a detail of the basic housing according to FIG. 1; and

Figure 4 shows a schematic cross section through a base housing with it

arranged protective tube module of a gas sensor according to another embodiment.

Functionally equivalent elements and regions bear the same reference numerals in the following figures and are not explained again in detail.

In Figure 1, a gas sensor as a whole carries the reference numeral 10. The gas sensor 10 initially comprises a base housing 12 (see Figure 3), which may be made of metal, for example. The base housing 12 has a fastening section, not shown here, for arranging the gas sensor on a flow channel, not shown here, for measuring gas. The flow channel can be, for example, the exhaust pipe of an internal combustion engine, for example the internal combustion engine of a motor vehicle.

At the base housing 12, a protective tube module 14 (see Figure 2) is attached. The protective tube module 14 has a main extension in the longitudinal direction 16. The base housing 12 and / or the protective tube module 14 may in particular be rotationally symmetrical about a central longitudinal axis 15. The Protective tube module 14 comprises an inner protective tube 18, which may be cylindrical, in particular circular cylindrical, with an inner side 19. The inner protective tube 18 is substantially pot-shaped and comprises a tube jacket 20 and a tube plate 22 with an opening 24 which is formed as a central hole. The inner protective tube 18 is surrounded by a pot-shaped outer protective tube 26 at a radial distance. The outer protective tube 26 likewise comprises a tube jacket 28 and a borehole 30 with an opening 32, through which the inner protective tube 18 is positively or in the

Essentially passed through a positive fit. The tube plate 30 of the

Outer protective tube 26 is in this case opposite the tube plate 22 of the

Inner protective tube 18 set back so that the inner protective tube 18, the outer protective tube 26 projects beyond in the longitudinal direction 16.

The inner protective tube 18 is connected to the outer protective tube 26 via a collar-like connecting portion 34. In this case, the protective tube module 14 may be integrally formed. The collar-like connecting portion 34 is provided on the base housing 12 facing the free end 36 of the inner protective tube 18. The connecting section 34 comprises a number of openings 38 extending in the longitudinal direction 16.

Below the connecting portion 34 in the direction of the base housing 12, a deflection region 37 is provided. This is generally triangular in shape and is limited on the one hand by a bottom 39 of the connecting portion 34 and the other by an end portion 40 of the outer protective tube 26, wherein the bottom 39 and the end portion 40 form an angle of 90 ° with each other. The basic housing has a circumferential deflection surface 42. The deflection surface is formed as a straight line in cross section and extends obliquely to a plane 45 extending orthogonally to the longitudinal axis 16 (see FIG.

In the cross section illustrated in FIG. 1, the deflection surface 42 encloses an angle of 45 ° with the end section 40 of the outer protective tube 26. The deflection region 37 is thus formed as a kind of circumferential triangular groove. The base housing 12 further includes an opening 44 for

Protective tube module 14 out. The opening 44 is bounded by an inner side 46 which merges at an edge 48 into the deflection surface 42. The edge 48 is arranged opposite the free end 36 of the inner protective tube 18 in the longitudinal direction 16, so that a gap 50 between the inner protective tube 18 and the base housing 12 is formed. In the tube 28 of the

Outer protection tube 26, a number of openings 52 are provided. In

Longitudinal direction 16, 52 swirl elements 54 are provided in the upper region of the openings. These protrude into the space 56 between outer protective tube 26 and inner protective tube 18 and direct the mass flow in the direction of the base housing 12. As shown in FIG. 1 only schematically, a sensor element 58 is arranged in the inner protective tube 18. The sensor element 58 may comprise, for example, an interdigital electrode (IDE). Such an IDE can be used, for example, to determine the amount of soot deposited thereon as a measure of the

Soot concentration in the exhaust serve. The sensor element 58 can thus be designed, in particular, as a gas-sensitive end section of, for example, a rod-shaped ceramic body, which is arranged in the base housing 12 and can be guided into the inner protective tube 18 through the opening 44.

The outer protective tube 26 finally includes a voltage applied to the base housing 12 and this partially encompassing free end portion 17. The end portion 17 may in particular be welded to the base housing 12 in order to attach the protective tube module 14 cohesively to the base housing 12.

The operation of the gas sensor 10 is then as follows:

The gas sensor 10 may, for example, in an exhaust pipe of a

Internal combustion engine to be installed. The sensor element 58 can in particular be provided for determining the particle concentration, for example the soot concentration, in the exhaust gas of the internal combustion engine, so that it can be a particle sensor, in particular a soot particle sensor.

However, it is also conceivable that the sensor element 58 is designed to determine another state variable of a measurement gas. So can

For example, the sensor element 58 as a so-called lambda probe for Determining the oxygen concentration in the exhaust gas of an internal combustion engine be designed or as a sensor element 58 for determining the

Nitrogen oxide concentration in the exhaust gas of an internal combustion engine. Also

Temperature sensor for measuring the exhaust gas temperature may be such a sensor element 58.

In order to determine the at least one state variable of a measuring gas, as indicated by the arrows 60, the measuring gas from the exhaust pipe, on or in which the gas sensor 10 is arranged, via the openings 52 in the space 56 between the inner protective tube 18 and outer protective tube 26th stream. Then, the measuring gas flows further through the openings 38 in the connecting portion 34. In this case, the mass flow of the measuring gas is throttled through the connecting portion 34.

Then, the measurement gas flows in the deflection region 37 and is of the

Deflection 42 directed to the gap 50 out. At the gap 50, the mass flow of the sample gas is throttled again. Then the sample gas flows in

Substantially parallel flows toward the sensor element 58, so that a state variable by means of the sensor element 58 can be determined. Then, the sample gas flows through the opening 24 in the inner protective tube 18 from the

Protective tube module 14 back into the exhaust pipe.

By providing the deflection surface 42 and the throttling by the

Openings 38 and later through the gap 50, a particularly favorable flow of the sensor element 58 can be provided. Furthermore, this also makes it possible, in particular, to increase the sensitivity of the sensor element 58 and / or to provide improved protection against cooling during the regeneration of the gas sensor 10.

FIG. 4 differs from the embodiment according to FIGS. 1 to 3 in that the inner protective tube 18 is not fixed on the outer protective tube 26 via the connecting section 34, but rather that the inner protective tube 18 on the outer protective tube 26 is fixed to the tube plate 30 of the outer protective tube 26 on the outer tube 26

Contact point 27 of outer protective tube 26 and inner protective tube 18 by means of a welded joint 29 is attached. By eliminating the connection section 34 falls the throttling of the mass flow through this way. However, the mass flow is still throttled through the gap 50.

Claims

claims

1. gas sensor (10), in particular particle sensor, for determining at least one state variable of a measuring gas, in particular the

Particle concentration in the exhaust gas of an internal combustion engine, with a

A housing (12) and a housing (12) arranged on the protective tube module (14) extending in a longitudinal direction (16) inner protective tube (18) in which a sensor element (58) can be arranged or arranged, and the inner protective tube (18 ) in any case partially surrounding outer protective tube (26), wherein sample gas between the outer protective tube (26) and the inner protective tube (18) through the protective tube module (14) can be flowed and in a deflection region (37) for inflow into the inner protective tube (18) is deflected , characterized in that the deflection region (37) one of

Base housing (12) formed deflecting surface (42), and that between the deflection surface (42) and the inner protective tube (18), a gap (50) is present, through the measuring gas in the inner protective tube (18) can be flowed, wherein the deflection surface (42 ) at the gap (50) has the smallest distance to the inner protective tube (18) in the longitudinal direction (16).

2. Gas sensor (10) according to claim 1, characterized in that the deflection surface (42) in cross section obliquely to an orthogonal to the

Extending longitudinally (16) extending plane.

3. Gas sensor (10) according to claim 1 or 2, characterized in that the deflection surface (42) is formed as a flat surface.

4. Gas sensor (10) according to at least one of the preceding claims, characterized in that the deflection region (37) has a

Basic housing (12) facing the end portion (40) of the outer protective tube (26).

5. Gas sensor (10) according to claim 4, characterized in that the outer protective tube (26) at the gap (50) facing away from the end

Deflection surface (42) is applied, so that the deflection region (37) is formed in cross-section substantially triangular.

6. Gas sensor (10) according to at least one of the preceding claims, characterized in that the inner protective tube (18) has an inner side, and that the base housing (12) to the inner protective tube (18) towards one of an inner side (46) limited opening (44 ), wherein the inside (44) of the opening (44) adjacent to the deflection surface (42).

7. Gas sensor (10) according to claim 6, characterized in that the

Inner side of the inner protective tube (18) is arranged flush with the inner side (46) of the opening (44).

8. Gas sensor (10) according to at least one of the preceding claims, characterized in that the protective tube module (14) has a collar-like connecting portion (34) for connecting the inner protective tube (18) with the outer protective tube (26), wherein the connecting portion (34) at least has an opening (38), can flow through the measuring gas in the deflection region (37).

9. Gas sensor (10) according to at least one of the preceding claims, characterized in that the inner protective tube (18) with the

Outer protective tube (26) materially connected, in particular welded, is, and / or that the protective tube module (14) to the base housing (12) integrally connected, in particular welded, is.

10. basic housing (12) and / or protective tube module (14) for a gas sensor (10) according to at least one of the preceding claims.