EP3105578A1

EP3105578A1 - Sensor arrangement for determining a propagation time of sound waves in a liquid medium and method for producing a sensor arrangement

Info

Publication number: EP3105578A1
Application number: EP15700317.9A
Authority: EP
Inventors: Danil HAAR; Peter Corsten
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2014-02-10
Filing date: 2015-01-15
Publication date: 2016-12-21
Also published as: WO2015117802A1; DE102014202343A1

Abstract

The invention relates to a sensor arrangement (10) for determining a sound propagation time-dependent property of a liquid, in particular a sound velocity, comprising: - a sound transducer (23) for outputting and/or receiving a sound signal; - a reflector element (32) for reflecting the sound signal; - a reflector holder (3) having a dimensionally stable holding element (31) for holding the reflector element (32); - a carrier element for fixing the arrangement of the sound transducer (23) and the holding element (31) of the reflector holder (3); wherein the holding element (31) of the reflector holder (3) extends substantially parallel to the sound signal path between the sound transducer (23) and the reflector element (32) and extends at least partially into an area facing away from the reflector element (32) downstream of the sound transducer (23).

Description

description

Sensor arrangement for determining a transit time of sound waves in a liquid

Medium and method for producing a sensor arrangement

Technical area

The present invention relates to sensor assemblies for use in a

A liquid container in a motor vehicle, wherein a quality of the liquid in the container is determined based on a running time of sound sources. Furthermore, the present invention relates to measures for preventing a sensor drift due to mechanical influences during assembly of the sensor arrangement and due to aging tolerances.

In particular, the present invention relates to methods of manufacturing such sensor arrays.

State of the art

Sensor arrangements are already known with which the quality and / or concentration of a liquid in a container can be determined. In particular, such sensor arrangements for determining the quality and concentration of a

Exhaust gas aftertreatment fluid, such as Adblue®, used in a fluid container.

The exhaust aftertreatment fluid may consist of a 32.5% solution of high purity urea in demineralized water and for exhaust aftertreatment of

Combustion exhaust gases of diesel engines are used. This is the

Exhaust aftertreatment liquid sprayed into the combustion exhaust gas, so that the nitrogen oxides are split into nitrogen, water and carbon dioxide. Contain in the exhaust aftertreatment fluid impurities such as unburned diesel fuel, water, ethylene glycol or the like, so reduces the ability of Exhaust aftertreatment liquid to reduce the nitrogen oxides in the combustion exhaust, or even damage may occur in the exhaust aftertreatment system.

The document US 2012/01 18059 A1 discloses a sensor arrangement for determining a quality of a liquid in a container. The sensor arrangement has a piezoelectric sound transducer which emits sound waves in the direction of a reflector plate and receives correspondingly reflected sound waves. Based on the measurement of the transit time of a sound wave signal from the transducer to the reflector plate and back a quality of the liquid can be derived in the container.

Such sensor arrangements are initially calibrated, in particular with respect to the distance between the sound transducer and the reflector plate. In general, however, the piezoelectric transducer and the reflector plate before mounting the

Sensor arrangement formed as a separate components, and it may due to temperature or aging-related deformations of components of the sensor assembly or the sensor assembly in total to a change in the distance between the

Sound transducer and the reflector plate come. This can lead to erroneous transit time measurements of the sound signal in the initially calibrated sensor arrangements.

It is an object of the present invention to provide a sensor arrangement for determining a transit time of a sound signal in a liquid, the temperature and aging-related tolerance is reduced. It is a further object to provide a method for producing such a sensor arrangement.

Disclosure of the invention

This object is achieved by the sensor arrangement for determining a transit time of a

Sound signal in a liquid according to claim 1 and solved by the method for producing a sensor arrangement according to the independent claim.

Further embodiments are specified in the dependent claims.

According to a first aspect, a sensor arrangement for determining a

sonic delay-dependent property of a liquid, in particular a

Speed of sound, provided, comprising: a sound transducer for outputting and / or receiving a sound signal;

a reflector element for reflecting the sound signal;

a reflector holder with a dimensionally stable holding element for holding the reflector element;

a support member for fixing the arrangement of the sound transducer and the

Retaining element of the reflector holder;

wherein the retaining element of the reflector holder substantially parallel to

Sound signal path between the transducer and the reflector element and at least partially in an area facing away from the reflector element behind the area

Sound transducer extends.

The above sensor arrangement is based on a measurement of a transit time of a sound signal between a sound transducer and a reflector element, which are arranged opposite one another with a non-changing, constant distance. For this purpose, the sound transducer and the reflector element are arranged in a fixed local relation to each other. The duration of the sound signal can be used as a characteristic variable for a

Property of the liquid in the container, in particular for the quality or quality of the liquid, are considered.

One idea of the above sensor arrangement is to arrange the reflector element on a temperature and age resistant retaining element, which engages behind at least partially remote from the reflector element side of the transducer. In this way it can be ensured that with temperature and / or aging-related deformations of the carrier material, the distance between the transducer and the reflector element remains unchanged.

Furthermore, the reflector holder can be integrally formed with the holding element and the reflector element, in particular from a stamped sheet.

The reflector holder can be made of an aging and temperature-resistant material, in particular of a metal.

The reflector holder may be formed of a dimensionally stable or dimensionally stable material than the carrier element. In particular, the reflector holder may be formed of a metal and the carrier element of a plastic. It can be provided that the sound transducer and the reflector holder in a

Support material of a support element are embedded, from which protrudes the reflector element.

Furthermore, the holding element of the reflector holder can be annular and surround the sound transducer so that the reflector element is one of the sound transducer

output sound signal, in particular back to the transducer, reflected.

The holding element of the reflector holder may have a passage opening and / or a

Have recess and / or structuring.

In particular, it can be provided that the holding element has a bead and / or with a curvature transverse to the extension direction of the sound signal path between the

Sound transducer and the reflector element is provided.

The sound transducer may be part of a measuring electronics, which is arranged in a capsule housing, wherein the sound transducer in a transducer pocket which protrudes from the capsule housing, is arranged.

According to one embodiment, the carrier material can hold the reflector holder on the capsule housing such that the reflector element is arranged opposite the transducer pocket.

According to a further aspect, a method for producing a sensor arrangement is provided, which comprises the following steps:

Arranging a reflector holder with a holding element and a reflector element on a measuring electronics with a sound transducer, so that a signal emitted and / or received by the transducer sound signal to the reflector element is reflected, wherein the holding element substantially parallel to the sound signal path between the transducer and the reflector element and at least partly in one of the

Reflector element facing away from the area behind the transducer extends; and

Fixing the arrangement with the reflector holder and the transducer using a support element.

In particular, the arrangement with the reflector holder and the sound transducer can be fixed by embedding the arrangement in a carrier material of the carrier element. Brief description of the drawings

Embodiments are explained below with reference to the accompanying drawings. Show it:

Figure 1 a is a perspective view of a capsule housing for receiving a

Measurement electronics;

Figure 1 b is a sectional view through the capsule housing for receiving the

Measurement electronics;

2 shows a measuring electronics with electrical connections for use in the

Capsule housing;

Figure 3a is a perspective view of an inserted into the capsule housing

Measurement electronics;

Figure 3b is a sectional view of the measuring electronics used in the capsule housing;

Figure 4 is a perspective view with a patch on the capsule housing

Retaining ring with a reflector plate;

Figure 5 shows a separate representation of the measuring electronics and the retaining ring with the

Reflector plate as active elements of the sensor assembly; and

Figure 6 is a perspective view of the sensor assembly for use in a

Container for holding a liquid and for determining a dependent on a sound velocity property of the liquid. Description of embodiments

FIGS. 1 a to 6 show individual stages of a method for producing a

Sensor assembly 10 is shown, wherein the perspective view of Figure 6, the complete sensor assembly 10 shows.

FIG. 1 a shows a perspective view of a capsule housing 1 and FIG. 1 b shows a corresponding sectional view through the capsule housing 1. The capsule housing 1 has an inner space 1 1 for receiving a measuring electronics 2. The interior 1 1 is accessible from a first side 12 of the capsule housing 1. On one of the accessible first side 12 opposite second side 13 is an outwardly projecting

Schallwandlertasche 14 formed, which for inserting a sound generator on the

Interior 1 1 is accessible. The capsule housing 1 is formed in the present embodiment is substantially cuboid, wherein the transducer pocket 14 at a

Edge region of the capsule housing 1 with respect to a longitudinal direction L is arranged.

In principle, other forms for the capsule housing 1 are possible, which allow a recording of the measuring electronics 2.

The capsule housing 1 is preferably made of an electrically non-conductive material, in particular an injection-moldable plastic, by injection molding or the like

Manufacturing process produced.

Laterally offset with respect to the longitudinal direction L, a sensor pocket 15, which likewise projects beyond the second side 13, is formed on an edge region. Like the sounder pocket 14, the sensor pocket 15 is hollow and accessible via the interior 1 1.

The capsule housing 1 further comprises in the inner space 1 1 directed on the webs 16, which are arranged on the inner surfaces of two transverse to the longitudinal direction L opposite sides and extend into the interior of the inner space 1 1. These serve as a support surface for a printed circuit board 21 of the measuring electronics 2 (not shown) in the interior of the interior 1 1.

On a side surface 18 of the capsule housing 1 through openings 19 for

Implementation of connecting leads for the measuring electronics 2 provided. In Figure 2, the measuring electronics 2 is separated perspectively shown. The measuring electronics 2 comprises a printed circuit board 21, on which electronic components 22 are arranged and interconnected for carrying out a transit time measurement or for electronic signal processing for a sound signal. Furthermore, a sound transducer 23 and a temperature sensor 24 are applied to the circuit board 21, which are arranged on the circuit board 21, that when inserting the circuit board 21 in the capsule housing 1, the transducer 23 into the cavity of the transducer pocket 14 and the temperature sensor 24 in the cavity the sensor pocket 15 protrudes. The sound transducer 23 may, for example, be a piezoelectric sound generator and sensor which can both emit and receive a sound signal, in particular an ultrasound signal.

Furthermore, the printed circuit board 21 or the electronic circuit arranged thereon is coupled via connecting lines 25 to a plug connector 26. About the connector 26, it is possible to control the measuring electronics 2 in a suitable manner, to supply with electrical energy and read out measured variables.

FIG. 3 a further shows the measuring electronics 2 inserted into the capsule housing 1

shown in perspective. The printed circuit board 21 of the measuring electronics 2 rests on the support webs 16 directed into the inner space 11, wherein the connecting lines 25 are guided through the lead-through openings 19 in the direction of the connector 26. Furthermore, the sound transducer 23 is in the cavity of the transducer pocket 14 and the

Temperature sensor 24 in the cavity of the sensor pocket 15th

FIG. 3b shows a sectional view through the arrangement of the process stage of FIG. 3a. One recognizes the embedded in the interior 1 1 circuit board 21 of

Measuring electronics 2. To fix the measuring electronics 2 and to protect them is the

Measuring electronics 2 in the interior 1 1 together with the sound transducer 23 and the

Temperature sensor 24 shed using an epoxy or synthetic resin 27 or the like.

FIG. 4 shows a perspective view of a further process stage. On the provided with the measuring electronics 2 capsule housing 1 is now a reflector holder 3 with an annular support member 31 and a reflector element, in this

Embodiment designed as a reflector plate 32 is arranged. However, as a reflector element may also be a differently shaped element with a suitable

Sound reflection surface can be provided. The annular retaining element 31 has a size which surrounds at least the transducer pocket 14. The reflector plate 32 is from the plane of extent of the annular

Holding element 31 arranged angled in the direction of the transducer pocket 14. The reflector plate 32 starts from an inner edge 34 of the annular retaining element 31 and preferably forms a right angle with the plane of the annular retaining element 31.

The reflector holder 3 is preferably made of a metallic material, in particular of a stamped sheet, in particular in an integrated manner, formed by a stamping process. The reflector holder 3 is arranged above the capsule housing 1 such that the

Extension plane of the annular support member 31 is substantially parallel to the second side 13 of the capsule housing 1 extends. As a result, the reflector plate 32 is substantially perpendicular to the second side 13 of the capsule housing 1. The reflector plate 32 is in

Substantially arranged the transducer pocket 14 in the longitudinal direction L of the capsule housing 1 opposite.

Apart from its annular extension, the retaining element 31 can also have a curvature or peripheral beads. In particular, an outer edge 33 of the annular retaining element 31 can be bent in relation to an inner edge 34 of the retaining element 31 in the direction of the extent of the reflector plate 32. In this way, the stability of the holding member 31 against deformation can be further improved.

Furthermore, the holding member 31 may be provided with through holes 36, recesses 37 or other structuring, which after an encapsulation with a

Carrier ensure a reliable hold in the substrate.

FIG. 5 shows an illustration of the arrangement of the reflector holder 3 and the measuring electronics 2. It can be seen that the sound transducer 23 of the measuring electronics 2 is substantially opposite the reflector plate 32 such that sound waves emitted by the sound transducer 23 are reflected back by the reflector plate 32 in the direction of the sound transducer 23. The distance between the transducer 23 and the reflector plate 32 is constant. In this way, a measurement of the time duration between a transmission of a

Sound signal can be closed by the transducer 23 and receiving a correspondingly reflected sound signal through the transducer 23 to a speed of sound in a medium, which is located between the transducer 23 and the

Reflector plate 32 is located. In particular, such a measuring arrangement for the determination a property of a liquid, such as an exhaust aftertreatment fluid, eg, Adblue®. In particular, the quality of the

Exhaust gas aftertreatment liquid are determined by the prevailing speed of sound therein. Since the density of the liquid as a rule also depends on its temperature, the temperature sensor 24 is arranged in the vicinity of the sound signal path between the sound transducer 23 and the reflector plate 32.

FIG. 6 shows a finished sensor arrangement 10, wherein the capsule housing 1 and the reflector holder 3 arranged thereon are encapsulated with a carrier material in an injection molding process so that the reflector holder 3 is permanently connected to the capsule housing 1 via a carrier element 4 formed from the carrier material. This penetrates

Carrier material in the through holes 36 and the recesses 37 and thereby fixes the reflector holder 3 reliably in the carrier material of the carrier element 4th

The carrier element 4 surrounds the capsule housing 1 substantially completely and thus forms in the direction of the second side 13 an annular projection 41, which is arranged above the annular holding element 31 with respect to the second side 13. In essence, the projection 41 is annularly formed so as to surround the sound transducer pocket 14, the reflector plate 32, and the sensor pocket 15. While the substrate the

Transducer cover 14 completely surrounds, so that it is embedded in the carrier material, the reflector plate 32 of the reflector holder 3 is recessed for improved reflection behavior to form a solid sound-reflecting surface for the sound emitted by the transducer 23 sound.

It is essential that the distance between the sound transducer 23 and the reflector plate 32 remains constant over the life and temperature variations such as occur during an assembly process. In particular, by the annular retaining element 31, which encloses the transducer pocket 14, can be reliably ensured that even with deformation of the substrate substantially no change in the distance between the reflector plate 32 and the transducer 23 takes place.

In further embodiments, the holding member 31 instead of in the ring form the

Sound transducer 23 and the Schallwandlertasche 14 surrounded in other formumschließender manner to a suitable fixation of the reflector plate 32 with respect to the

Schallwandlertasche 14 and the transducer 23 to achieve. Alternatively, it is possible to use a retaining element 31 instead of in the form surrounding the sound converter pocket 14 Holding element 31 also in U-shape or the like provided. Finally, to ensure a constant distance between the reflector plate 32 and the transducer pocket 14, at least partial engagement of the transducer pocket 14 with a portion of the retaining element 31 may be sufficient.

LIST OF REFERENCE NUMBERS

capsule housing

sensor arrangement

inner space

first page

second page

Transducer pocket

sensor case

projections

edge

side surface

Through openings

measuring electronics

circuit board

components

transducer

temperature sensor

interconnectors

Connectors

Epoxy or synthetic resin

reflector mounting

retaining element

reflector plate

outer edge

inner edge

Through openings

recesses

support element

annular projection

Claims

- 12 - Claims

1. Sensor arrangement for determining a sound propagation time-dependent property of a liquid, in particular a sound velocity, comprising:

a sound transducer (23) for outputting and / or receiving a sound signal; a reflector element (32) for reflecting the sound signal;

a reflector holder (3) with a holding element (31) for holding the

Reflector element (32);

a support member for fixing the arrangement of the sound transducer (23) and the holding member (31) of the reflector holder (3);

wherein the holding element (31) of the reflector holder (3) substantially parallel to the sound signal path between the sound transducer (23) and the

Reflector element (32) and at least partially extends in an area remote from the reflector element (32) behind the sound transducer (23).

2. Sensor arrangement (10) according to claim 1, wherein the reflector holder (3) with the holding element (31) and the reflector element (32) in one piece, in particular from a stamped sheet is formed.

3. Sensor arrangement (10) according to claim 1 or 2, wherein the reflector holder (3) made of an aging and temperature-resistant material, in particular of a metal, is formed.

4. Sensor arrangement (10) according to one of claims 1 to 3, wherein the

Reflector holder (3) is formed from a dimensionally stable or dimensionally stable material than the carrier element.

5. Sensor arrangement (10) according to one of claims 1 to 4, wherein the sound transducer (23) and the reflector holder (3) in a carrier element with a carrier material, in which the sound transducer (23) and the reflector holder (3) are embedded from the reflector element (32) protrudes. - 13 -

6. Sensor arrangement (10) according to one of claims 1 to 5, wherein the holding element (31) is annular and surrounds the sound transducer (23) so that the reflector element (32) reflects a signal emitted by the sound transducer (23) sound signal.

7. Sensor arrangement (10) according to one of claims 1 to 6, wherein the holding element (31) has a passage opening (36) and / or a recess (37) and / or other structuring.

8. Sensor arrangement (10) according to one of claims 1 to 7, wherein the retaining element

(31) has a bead and / or is provided with a curvature transverse to the extension direction between the sound transducer (23) and the reflector element (32).

9. Sensor arrangement (10) according to one of claims 1 to 8, wherein the sound transducer (23) is part of a measuring electronics (2) which is arranged in a capsule housing (1), wherein the sound transducer (23) in a transducer pocket (14). coming from the

Capsule housing (1) protrudes, is arranged.

10. Sensor arrangement (10) according to claim 9, wherein the carrier material, the

Reflector holder (3) on the capsule housing (1) holds that the reflector element

(32) of the transducer pocket (14) is arranged opposite.

1 1. A method for producing a sensor arrangement (10), comprising the following steps:

- Arranging a reflector holder (3) with a holding element (31) and a reflector element (32) on a measuring electronics (2) with a sound transducer (23), so that one of the sound transducer (23) output and / or received sound signal to the reflector element (32) is reflectable, wherein the holding element (31) substantially parallel to the sound signal path between the sound transducer (23) and the reflector element (32) and at least partially in an area facing away from the reflector element (32) behind the area

Sound transducer (23) extends; and

Fixing the arrangement of reflector holder (3) and sound transducer (23) with a support element (4), so that the reflector holder (3) is held on the sound transducer (23). - 14 -

12. The method of claim 1 1, wherein the arrangement with the reflector holder (3) and the sound transducer (23) by embedding the arrangement in a carrier material of the carrier element (4) is fixed.