METHOD FOR DETERMINING THE FILL STATE IN A TANK

• US 20170122789A1
• Filed: 01/13/2017
• Published: 05/04/2017
• Est. Priority Date: 07/14/2014
• Status: Active Grant

• Current Assignee: Vitesco Technologies GmbH (Continental AG)
• Original Assignee: Continental Automotive GmbH (Continental AG)
• Inventors: Diouf, Cheikh, Mesmer, Denis, Borsoi, Sonny, Dupriez, Mathieu
• Granted Patent: US 10,386,221 B2
• Time in Patent Office: Days
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2610/1406 Storage means for substances, e.g. tanks or reservoirs
• CPC Class Codes: F01N 2900/1814 Tank level
• CPC Class Codes: F01N 3/2066 Selective catalytic reduction [SCR]
• CPC Class Codes: G01F 23/2962 Measuring transit time of reflected waves
• CPC Class Codes: G01F 23/80 Arrangements for signal processing
• CPC Class Codes: G01F 25/20 of apparatus for measuring liquid level
• CPC Class Codes: G01N 2291/011 Velocity or travel time
• CPC Class Codes: G01N 2291/0222 Binary liquids
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01N 2291/045 External reflections, e.g. on reflectors
• CPC Class Codes: G01N 2291/101 one transducer
• CPC Class Codes: G01N 29/024 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y10S 367/902 Speed of sound compensation
• CPC Class Codes: Y10S 367/908 Material level detection, e.g. liquid level

Abstract

The disclosure relates to a method for determining a level of a liquid in a tank with an ultrasonic fill state sensor and at least two reference surfaces for reflecting an ultrasonic wave transmitted by the ultrasonic fill state sensor. A first reference surface is arranged below a second reference surface. The method includes determining a first propagation speed of an ultrasonic wave to the first reference surface on a first measurement path and a second propagation speed from the first reference surface to the second reference surface on a second measurement path. The method also includes measuring a propagation time of an ultrasonic wave from the ultrasonic fill state sensor to a liquid level of the liquid in the tank, selecting the first propagation speed or the second propagation speed based on at least one selection criterion, and calculating a fill state using the propagation time measured.

Claims

1. A method for determining a level of a liquid in a tank with an ultrasonic level sensor and at least two reference surfaces for reflection of an ultrasonic wave that is emitted from the ultrasonic level sensor, wherein a first reference surface is disposed below a second reference surface, the method comprising the following steps:

a) determining a first propagation speed of an ultrasonic wave in the liquid over a first measuring distance from the ultrasonic level sensor to the first reference surface;

b) determining a second propagation speed of an ultrasonic wave in the liquid over a second measuring distance from the first reference surface to the second reference surface;

c) measuring a propagation time of an ultrasonic wave from the ultrasonic level sensor to a liquid level of the liquid in the tank;

d) selecting the first propagation speed or the second propagation speed depending on at least one selection criterion; and

e) computing a level with the propagation time measured in step c) and the propagation speed selected in step d).

2. The method of claim 1, wherein the ultrasonic level sensor is disposed outside of the tank and an ultrasonic wave of the ultrasonic level sensor passes through a coupling layer before it enters the liquid in the tank, wherein the coupling layer comprises a tank wall and the propagation time of the ultrasonic wave in the coupling layer is taken into account in step a) with a correction factor.

3. The method of claim 1, wherein steps a) through e) are repeated iteratively and when selecting the propagation speed in step d) a propagation speed selected for a previous iteration of the method is considered.

4. The method of claim 1, wherein a computed level is used as a first selection criterion in step e), wherein for a level below a level limit value the first propagation speed is selected and for a level above a level limit value the second propagation speed is selected.

5. The method of claim 1, wherein a comparison between the first propagation speed and the second propagation speed is performed as a second selection criterion in step d), wherein the first propagation speed is selected if a speed deviation between the first propagation speed and the second propagation speed exceeds a speed limit.

6. The method of claim 1, wherein the propagation time measured in step c) is checked as a third selection criterion in step d), wherein the second propagation speed is not selected if the measured propagation time lies outside a time interval corresponding to twice the propagation time to the second reference surface and the first propagation speed was selected for a previous iteration of the method.

7. The method of claim 1, wherein, during the calculation of the level in step e), the following substeps are executed:

i) computing the level based on the selected propagation speed;

ii) checking whether a level which is determined at the second propagation speed corresponds to twice a height of the second reference surface;

iii) determining a fluctuation in a second response signal of the second reference surface at the ultrasonic level sensor in a time interval;

iv) checking whether the fluctuation in the second response signal exceeds a prespecified limit value; and

v) correcting the level which is computed in step i) to the height of the second reference surface when steps ii) and iv) are complete.

8. The method of claim 1, wherein in step d) a change from the first propagation speed to the second propagation speed only takes place if a stationary mode exists.

9. The method of claim 1, wherein an input signal of the at least one selection criterion used in step d) is filtered with a low pass filter.

10. The method of claim 1, wherein an input signal of the at least one selection criterion used in step d) is filtered with a hysteresis.

11. A motor vehicle having a tank for an operating liquid, the tank comprising an ultrasonic level sensor for determining the level in the tank and at least two reference surfaces for reflection of an ultrasonic wave that is emitted by the ultrasonic level sensor, a first reference surface is disposed below a second reference surface, and at least one controller is arranged for level determination to carry out a method for determining the level of the liquid in the tank, the method comprising the following steps:

a) determining a first propagation speed of an ultrasonic wave in the liquid over a first measuring distance from the ultrasonic level sensor to the first reference surface;

b) determining a second propagation speed of an ultrasonic wave in the liquid over a second measuring distance from the first reference surface to the second reference surface;

c) measuring a propagation time of the ultrasonic wave from the ultrasonic level sensor to a liquid level of the liquid in the tank;

d) selecting the first propagation speed or the second propagation speed depending on at least one selection criterion; and

e) computing a level with the propagation time measured in step c) and the propagation speed selected in step d).

12. The motor vehicle of claim 11, wherein the ultrasonic level sensor is disposed outside of the tank and an ultrasonic wave of the ultrasonic level sensor passes through a coupling layer before it enters the liquid in the tank, wherein the coupling layer comprises a tank wall and the propagation time of the ultrasonic wave in the coupling layer is taken into account in step a) with a correction factor.

13. The motor vehicle of claim 11, wherein steps a) through e) are repeated iteratively and when selecting the propagation speed in step d) a propagation speed selected for a previous iteration of the method is considered.

14. The motor vehicle of claim 11, wherein a computed level is used as a first selection criterion in step e), wherein for a level below a level limit value the first propagation speed is selected and for a level above a level limit value the second propagation speed is selected.

15. The motor vehicle of claim 11, wherein a comparison between the first propagation speed and the second propagation speed is performed as a second selection criterion in step d), wherein the first propagation speed is selected if a speed deviation between the first propagation speed and the second propagation speed exceeds a speed limit.

16. The motor vehicle of claim 11, wherein the propagation time measured in step c) is checked as a third selection criterion in step d), wherein the second propagation speed is not selected if the measured propagation time lies outside a time interval corresponding to twice the propagation time to the second reference surface and the first propagation speed was selected for a previous iteration of the method.

17. The motor vehicle of claim 11, wherein, during the calculation of the level in step e), the following substeps are executed:

i) computing the level based on the selected propagation speed;

ii) checking whether a level which is determined at the second propagation speed corresponds to twice a height of the second reference surface;

iii) determining a fluctuation in a second response signal of the second reference surface at the ultrasonic level sensor in a time interval;

iv) checking whether the fluctuation in the second response signal exceeds a prespecified limit value; and

v) correcting the level which is computed in step i) to the height of the second reference surface when steps ii) and iv) are complete.

18. The motor vehicle of claim 11, wherein in step d) a change from the first propagation speed to the second propagation speed only takes place if a stationary mode exists.

19. The motor vehicle of claim 11, wherein an input signal of the at least one selection criterion used in step d) is filtered with a low pass filter.

20. The motor vehicle of claim 11, wherein an input signal of the at least one selection criterion used in step d) is filtered with a hysteresis.