WO2009074428A1

WO2009074428A1 - Device for measuring the filling level of a fluid in a container

Info

Publication number: WO2009074428A1
Application number: PCT/EP2008/065630
Authority: WO
Inventors: Michael Gerlach
Original assignee: Robert Bosch Gmbh
Priority date: 2007-12-12
Filing date: 2008-11-17
Publication date: 2009-06-18
Also published as: DE102007059853B4; DE102007059853A1

Abstract

The invention relates to a device for measuring the filling level of a fluid in a container for storing the fluid, in particular a fluid for reducing nitrogen oxides in exhaust gases of internal combustion engines. Said device comprises an ultrasonic transducer for producing an ultrasonic signal and for capturing the ultrasonic signals reflected in the region of the liquid level. Deflection means are provided in the container for deflecting the ultrasonic signal.

Description

description

title

Device for measuring a level of a liquid in a container

State of the art

The invention relates to a device for measuring a level according to the preamble of the main claim. A device for measuring a filling level from DE 199 42 378 A1 is already known, in which an ultrasonic transducer is arranged outside a container near one end of a sound guide channel provided between a container bottom and a top wall. The ultrasonic transducer sends ultrasonic waves into the sound guide channel, the ultrasonic waves being reflected at a liquid level. The reflected ultrasonic waves are received by the ultrasonic transducer and evaluated in an evaluation unit. From a running time of the ultrasonic waves, a level is determined.

Disclosure of the invention

The inventive device for measuring a level with the characterizing features of the main claim has the advantage of a simple construction for reliable detection of a level.

The measures listed in the dependent claims are advantageous

Further developments and improvements of the device specified in the main claim for measuring a level possible.

An arranged between a transducer and a Umlenkmitel sound guide body ensures advantageously a well-detectable Reference signal, although the deflection means may be optimized to direct the majority of the emitted ultrasonic energy to the liquid surface.

It is particularly advantageous to have the sound guide body in its

Longitudinal extent between transducer and deflection at least partially open, so that falls below a freezing point of the tank liquid this has the opportunity, in contrast, for example, the situation with sound guide body in the form of closed tubes to exchange with the liquid outside the sound channel, so that freezing damage on

Level sensor, i. can be avoided at the sound guide body, as a result of an emerging ice pressure by ice emerging in the sound guide body can also spread outside the sound conduction body.

A further sound guide body or a sound guide body extending on the sound path beyond a deflecting means advantageously further improves the signal reflected by the liquid level. Reflection losses can be reduced or avoided.

These further sound conduction areas can also be advantageously opened, i. in particular slotted or cupped, be formed.

In addition, it is additionally advantageous to produce the sound guide channel or the one or more sound guide body made of elastic plastic, as an additional safety measure against damage during freezing

Liquid in the sound-carrying bodies.

From the features mentioned in the further claims and the description, there are further advantages.

Brief description of the drawings Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it

FIG. 1 shows a known tank arrangement,

FIG. 2 shows a device for level determination arranged in a tank,

FIG. 3 shows a shell-shaped sound guide body,

FIG. 4 shows a slotted tube,

FIG. 5 shows a fill level sensor with slotted tube,

FIG. 6 shows a fill-level sensor with a slotted tube in a plan view,

Figure 7 shows a sensor with integrated sound guide body and

Figure 8 shows another device in a tank for level determination.

Embodiments of the invention

FIG. 1 shows a device known from DE 10312102 for measuring a fill level of a liquid in a container. The device consists essentially of a container 1, a sound guide channel 2 and a

Ultrasonic transducer 3. In the container 1 is any liquid 4, such as urea solution or ammonia solution, up to a level 5. For example, from a container bottom 8 of the container 1 from a delivery line 9 extends to a arranged outside of the container 1 delivery unit 10, the Promotes liquid 4 from the container 1 and a subsequent arbitrary process 11, for example, an injection into an exhaust passage of an internal combustion engine, feeds. The urea solution and the ammonia solution are so-called reducing agents, which are injected into the exhaust passage of the internal combustion engine to reduce nitrogen oxide emissions. The container 1 has a vent line 12, for example, to a ceiling wall 15 of the container 1 is provided and connects the container 1 with the atmosphere. By the vent line 12 ensures that no over or under pressure can arise in the container 1. The sound guide channel 2 is connected at one end at least indirectly via a connecting channel 16 to the container 1 and at the other end to the ventilation line 12. The connecting channel 16 does not open directly into the container 1 in the embodiment according to the drawing in order not to reduce the strength of the container 1. Instead, the connecting channel 16 is connected at its end facing the container bottom 8, for example, with the delivery line 9. However, the connecting channel 16 could also be connected in a manner not shown directly to the container bottom 8 and thus to the container 1. The sound guide channel 2 is arranged outside of the container 1. The sound guide channel 2 extends in a flow area 17 initially in the plane of the container bottom 8 in the horizontal direction of a side wall 21 of the container 1 against. The connecting channel 16 opens into the flow area 17 of the sound guide channel 2. The connecting channel 16, for example, extends transversely to the flow area 17. The flow area 17 is adjoined by a measuring tube area 18 of the sound guide channel 2, which at the end facing the flow area 17 has a first bend 19 with a first Bending radius 22 and a deflection 23 has. The deflection 23 is for example ninety degrees, but may also be less than or greater than ninety degrees. The deflection 23 is understood to mean an angle. At the first bend 19 of the measuring tube region 18, the measuring tube region 18 then extends, for example, in a straight line in the direction of the ceiling wall 15. However, the measuring tube region 18 can also have further bends and run in a looped manner. By doing

Sound channel 2 is filled with liquid container 1 to a level 5.1. According to the known hydrostatic law of the so-called communicating tubes, a liquid level 5.1 sets in the sound guide channel 2, which is identical to the liquid level 5 in the container 1, since the sound guide channel 2 is at least indirectly connected to the container 1. Via the connection channel 16, liquid can flow into the sound guide channel 2 or out of the sound guide channel 2. This happens as soon as the level 5 and the level 5.1 are different. If the level 5 is higher than the level 5.1, for example, after refueling of the container 1, liquid flows over the If the level 5.1 is higher than the level 5, for example by the removal of liquid from the container 1 by means of the delivery unit 10, liquid flows vice versa from the sound channel 2 via the connecting channel 16 in the delivery line 9 or with direct connection of the

Connecting channel 16 to the container 1 in the container 1. The sound guide channel 2 has, for example, a round cross section with an inner diameter which is smaller than one centimeter. The inner diameter is for example five millimeters. The cross section of the sound guide channel 2 may also be oval or polygonal. The sound guide channel 2 consisting of flow area 11 and measuring tube 16 is for example made in one piece. The ultrasonic transducer 3 is arranged on the connecting channel 16 facing the end of the sound guide channel 2. The ultrasound transducer 3 is, for example, a pulse echo sensor which clocked generates and emits short sound pulses and a running time t between the

Time of transmission of the pulse and the time of return of the reflected sound pulse, the so-called echo measures. However, it is also possible to use another sensor which, for example, continuously generates and transmits sound waves, in which case the transit time t is not determined, but a phase shift between the emitted and reflected sound waves is measured. The ultrasound transducer 3 is, for example, transmitter and receiver at the same time. However, it is also possible to use an ultrasonic transducer 3 in which the transmitter and receiver are spatially separated. The sound pulse generated by the ultrasonic transducer 3 with a predetermined intensity is mainly transmitted to the liquid in the sound guide channel 2. The sound pulse propagates in the liquid at a sound velocity in the direction of the sound guide channel 2, is guided by the wall of the sound guide channel 2, hits at the level of the level 5.1 on the liquid level of the liquid in the sound guide channel 2 and is reflected there. The reflected sound pulse now moves in the opposite direction back to the ultrasonic transducer 3. About the product of the speed of sound and running time of the level 5 is determined. In the sound guide channel 2, for example in the lead region 17, at least one reference reflection surface 24 is provided, which is flat, for example, and projects transversely partially into the sound guide channel 2. Of the Acoustic pulse reflected at the reference reflection surface 24 is referred to as a reference echo. The duration of the reference echo is known as soon as it has been measured once at a certain temperature and a certain pressure, and is stored, for example, in an electronic evaluation unit 25, which via a signal line 26 with the

Ultrasonic transducer 3 is connected. A distance to be covered by a sonic pulse between the reference reflection surface 24 and the ultrasound transducer 3 is also known and stored, for example, in the evaluation unit 25. The duration of the sound pulses depends on the speed of sound in the liquid. The speed of sound in the

Liquid is dependent on the density of the liquid. The density of the liquid in turn depends on the temperature and the pressure of the liquid. By comparing the stored in the evaluation unit 25 running time of a reference echo with the measured during a level measurement duration of a reference echo disturbances, such as a change in temperature, pressure or density of the liquid can be deducted by the evaluation unit 25 subsequently, so that a in this way corrected measurement of the level is almost independent of temperature and pressure. By comparing the duration of the measured reference echo with the duration of the reference echo stored in the evaluation unit 25, it is possible with known temperature of the liquid 4 and known pressure in the container 1, liquid properties, such as the density to calculate and verify. In this way, for example, it can be checked whether the correct liquid 4 has been filled into the container 1 or whether the concentration, for example in the case of a urea solution as liquid 4, is within the predetermined range. To determine the temperature of the liquid, for example, a temperature sensor is integrated in the ultrasonic transducer 3 or a temperature sensor is provided in the container 1.

FIG. 2 shows a container or tank 1 with a device 30 according to the invention for level determination located in the interior 36 of the tank. The tank can be filled with an aqueous urea solution called "AdBlue" via an opening which can be closed with a tank lid 31. AdBlue for exhaust gas removal can be taken from the tank via a removal line 33 connected in the area of the bottom 8, similar to FIG become. The device comprises an ultrasonic transducer 3 and a deflecting means 35 designed as a mirror, both of which are arranged in the region of the tank bottom 8. The ultrasonic transducer is disposed at one end of a first sound guide body 37 formed as a plastic tube, while the other end of the plastic tube is inserted in a mounting block 41 that holds the mirror 35. Perpendicular to the first sound guide body 37 or perpendicular to the liquid level 34, a second sound guide body 39, also designed as a plastic pipe, projects out of the mounting block 41 in the direction of the liquid level 34. The ultrasonic transducer can be controlled via the evaluation unit 25, for example, the control unit of a motor vehicle, or it can be evaluated sound signals received via the evaluation unit for determining the tank level. The two plastic tubes have, for example, an outer diameter of about 1.5 centimeters and an inner diameter of about 1 centimeter. The device extends from the sound transducer over the first

Sound guide body 37 to the mirror 35 over a length of about 7 centimeters along the bottom of the tank, while starting from the tank bottom according to such a highly refillable tank has a height of about 18 centimeters.

The ultrasound is emitted by the transducer, deflected at the mirror 35 upwards and reflected at the liquid surface. The signal thus reflected, which has passed through both the first sound guide body completely and the second sound guide body twice up to the level of the liquid level, is received by the transducer 3. A second reflection signal results from a partial reflection of the ultrasound through the mirror directly back to the transducer 3. This signal has after transmission, regardless of the tank level, only the first sound guide body 37 (twice) go through. The level-independent signal can be used for Meßwertkalibrierung by the compensation of temperature or

Quality fluctuations of the AdBlue located in the tank are made possible by detecting the transit time through a predetermined, level-independent path through the first sound guide body 37, which as a rule is always filled with AdBlue. In a simple embodiment, the mirror can also be omitted and replaced by a bend of a plastic tube, which unites in one-piece design first and second sound guide body in itself. Preferably, this plastic tube is coated in the interior, in particular in the region of this bend with a reflective layer, on the one hand, a change in direction of the

Sound signals along the bend and on the other a partial direct reflection back to the transducer supported. In a further alternative embodiment, the second sound guide body 39 can also be omitted, as long as a free "visual connection" between deflecting means and liquid level is ensured in the tank.

In further alternative arrangements, the first and second sound guide bodies 37 and 39 can also be formed by a half-shell 51 according to FIG. 3 and / or a slotted pipe 53 according to FIG.

FIG. 5 shows, without representation of a tank, a fill level sensor in a side view 61, in which the second sound guide body is omitted and the first sound guide body is formed from a slotted tube 370. In plan view 63 of this sensor is shown in Figure 6, which provides insight into the opening 65 of the mounting block 41 through which the deflection mirror 35 is partially visible.

Figure 7 shows a device or a level sensor with integrated sound guide body 71, which consists of an L-shaped plastic body. The reference path or the "first" sound guide body of the integrated body

71 transmits the ultrasound transducer 3 terminal between the transducer 3 and deflection 73, the tubular body has a recess 75, so that in this area a bowl-shaped formation results, which provides in the case of freezing of the tank contents the entire tank volume as a compensating volume, so that the level sensor or the plastic body can not be damaged by freezing and thus expanding water in the region of the integrated body 71. The same applies to the "second" sound guide body of the integrated body 71 behind the deflection region 73 with a corresponding recess 77, which is guided to the local end of the integrated body 71. In the deflection region 73 can inside a Reflective layer applied or introduced a reflective prism. But it can also be a plastic with good reflective properties for the entire integrated sound guide body are used, so that without providing additional measures, the deflection can also be formed solely by the shape of the plastic tube in the deflection 73. Alternatively, the

Plastic pipe in the deflection be performed in a curved shape.

Figure 8 shows a built-in tank 1 level sensor assembly without additionally provided sound guide body. The controlled via the line 26 from the controller 25, fixed in the bottom region of the tank

Ultrasonic transducer 3 sonicates a spaced, also in the bottom region arranged prism or deflection means 35, which can deflect the sound waves up to the liquid surface. The double lines 85 symbolize a sound emission of the transducer 3 in the direction of the deflection means, a reflection by the deflection means upward, a reflection by the liquid level and finally a new reflection by the deflection means back to the transducer, which receives the signal again. The double lines 81 symbolize a (partial) reflection from the transducer emitted ultrasonic signals through the deflection directly back to the converter; This signal is used in the manner already described for Meßwertkalibrierung. In a simple

Embodiment, the prism can also be omitted and the deflection means are formed by a sonicated by the ultrasonic transducer 3 wall 87 of the tank 1. The wall 87 is here the inside of the container located side of the tank wall 21st

Claims

claims

1. A device for measuring a level of a liquid (4) in a container (1) for storing the liquid, in particular a liquid for the reduction of nitrogen oxides in exhaust gases of internal combustion engines, with an ultrasonic transducer (3) for generating an ultrasonic signal and for receiving the in Reflected area of a liquid level (34)

Ultrasonic signal, characterized in that in the interior (36) of the container (1) a deflection means (35) is provided for deflecting the ultrasonic signal in the direction of the liquid level (34).

2. Apparatus according to claim 1, characterized in that the deflection takes place such that the ultrasonic signal (85), the liquid behind the

Passing deflector substantially perpendicular to the liquid level.

3. Apparatus according to claim 1 or 2, characterized in that between the ultrasonic transducer (3) and the deflection means (35) a sound guide body (37) is arranged.

4. Apparatus according to claim 3, characterized in that the

Sound guiding body as a slotted tube (53) or, at least partially, shell-shaped (51, 75) is formed.

5. Device according to one of the preceding claims, characterized in that between the deflection means (35) and the liquid level (34), a second sound guide body (39) is arranged.

6. The device according to claim 5, characterized in that the second sound guide body (39) as a slotted tube (53) or, at least partially, shell-shaped (51, 77) is formed.

7. Apparatus according to claim 3 or 4, and according to claim 5 or 6, characterized in that the first and second sound guide body are integrally connected to each other.

8. Device according to one of claims 3 to 7, characterized in that the or the sound guide body are made of elastic plastic.

9. Device according to one of the preceding claims, characterized in that the ultrasonic transducer (3) is arranged in the container laterally from the deflection means (35).

10. The device according to claim 9, characterized in that the deflection means (35) and the ultrasonic transducer (3) in the container (1) in

Substantially arranged at the same height relative to the bottom (8) of the container.

11. The device according to claim 10, characterized in that the deflection means (35) and the ultrasonic transducer (3) in the region of the container bottom (8) are arranged.