Method and device for optically determining a filling level in liquid-filled containers

• US 20030155538A1
• Filed: 02/18/2003
• Published: 08/21/2003
• Est. Priority Date: 02/18/2002
• Status: Active Grant

• Current Assignee: Kautex Textron GmbH & Company KG (Textron Inc)
• Original Assignee: Kautex Textron GmbH & Company KG (Textron Inc)
• Inventors: Siepmann, Georg
• Granted Patent: US 6,921,911 B2
• Time in Patent Office: Days
• US Class Current: 250/577
• CPC Class Codes: G01F 23/2927 for several discrete levels, e.g. with more than one light-conducting sensing element
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: Y10S 250/904 with single light guide element to guide light in a continuous path

Abstract

In a method of optically determining a level of liquid in a liquid-filled container a light guide body projects into the container. The light guide body has an end face for the entry and exit of light and stepped side faces forming separate reflection faces. The light is totally reflected at those reflection faces which are not immersed in the liquid but refracted into the liquid at immersed reflection faces. The totally reflected light is reflected back to the end face. The intensity of the light beam reflected totally by each reflection face back to the end face is measured separately. Measurement signals for determining the filling level are subjected to plausibility checking to recognise and eliminate measurement faults and errors. The invention can be used for determining the level of liquid in a container or tank for fuel, washing water, oil, hydraulic fluid and the like in a motor vehicle.

Claims

1. A method of determining a filling level in a liquid-filled container using a light guide body which projects into the volume of the container and which has an end face for the entry and exit of light and side faces providing reflection faces separated by steps,

wherein light introduced into the light guide body at said end face is totally reflected at those reflection faces which are not immersed in liquid in the container but is refracted into the liquid at immersed reflection faces,

wherein light totally reflected by a reflection face is reflected back to the end face, and p1 wherein the intensity of the light beam totally reflected by each reflection face and back to the end face is measured separately.

2. A method as set forth in claim 1

wherein intensity measurement for each light beam reflected totally by a reflection face and back to the end face is effected by means of at least one photosensor.

3. A method as set forth in claim 2

wherein the measurement signals of the totally reflected light are passed to a display unit to display the filling level of liquid in the container.

4. A method as set forth in claim 3

wherein the measurement signals of the totally reflected light are evaluated and checked before display.

5. A method as set forth in claim 4

wherein the evaluation procedure includes plausibility checking for recognising and eliminating measurement errors.

6. A method as set forth in claim 4

wherein the evaluation operation includes correction in respect of at least one of the effects consisting of light attenuation in the light guide body, noise and scatter light.

7. A method as set forth in claim 1

wherein at least one reference signal is produced and evaluated, and

the reference signal is reflected completely independently of the filling level of liquid in the container.

8. A method as set forth in claim 7

wherein a respective reference signal which is independent of said filling level is produced for the longest and shortest signal paths through the light guide body and evaluated.

9. A method as set forth in claim 1

wherein for each reflection plane a reference signal reflected independently of said filling level is produced and evaluated.

10. A method as set forth in claim 1

wherein the light guide body is of rectangular cross-section.

11. A method as set forth in claim 1

wherein the light guide body is of square cross-section.

12. A method as set forth in claim 1

wherein the light guide body is of elliptical cross-section.

13. Device for determining a filling level in a liquid-filled container, including

a light guide body which is adapted in operation of the device to project into the internal volume of the container, the light guide body being of rectangular cross-section and having an end face with an entry region for the entry of light into the light guide body and an exit region for the exit of light from the light guide body and first and second side faces each comprising steps providing at least two reflection faces, the reflection faces at the one side face being associated with respective reflection faces at the other side face, wherein the reflection faces of the first side face are at least in part such that light entering the light guide body at said entry region is refracted into the liquid when the reflection face in question is immersed in the liquid but is totally reflected back into the light body in a direction towards the second side face thereof when the reflection face in question is not immersed in the liquid and the light totally reflected by a reflection face at said first side face is reflected by the respectively associated reflection face at the second side face in a direction towards the exit region of said end face, and

measuring means for separately measuring the intensity of a light beam totally reflected by each said reflection face of said second side face.

14. Device as set forth in claim 13

wherein the reflection faces of the first side face are permanently reflective.

15. Device as set forth in claim 13

wherein the reflection faces of the second side face are permanently reflective.

16. Device as set forth in claim 13

wherein the reflection faces of the first side face are at least in part of a permanently reflective nature in a portion thereof.

17. Device as set forth in claim 13

wherein the reflection faces of the second side face are at least in part of a permanently reflective nature in a portion thereof.

18. Device as set forth in claim 13

wherein the measuring means are disposed on the light exit region of said end face.

19. Device as set forth in claim 13

wherein the measuring means are disposed in the light exit region of said end face.

20. Device as set forth in claim 13 including

a light guide cable connecting the measuring means to said light exit region of said end face, said cable having at least one separate optical fiber for each said reflection face.

21. Device as set forth in claim 13

wherein said reflection faces form an angle of substantially 45°

with the direction of incident light.

22. Device as set forth in claim 13

wherein said measuring means includes at least one photosensor for each reflection face.

23. Device as set forth in claim 22

wherein said measuring means comprises a line sensor.

24. Device as set forth in claim 13 including

an evaluation means for implementing a plausibility check in respect of signals from said measuring means for recognising and eliminating measurement errors.

25. Device as set forth in claim 24 including

a microcontroller.

26. Device as set forth in claim 13 including

a light source for providing light for said light guide body,

wherein the limit band of the light source, the light guide spectrum of said light guide body and the sensitivity spectrum of the photosensor are matched to each other.

27. Device for determining a filling level in a liquid-filled container, including

a light guide body which is adapted in operation of the device to project into the internal volume of the container, having an end face with an entry region for the entry of light into the light guide body and an exit region for the exit of light from the light guide body and a side face comprising steps providing at least two at least substantially annular reflection faces, wherein said reflection faces are so designed at least over a portion of their periphery that light entering the light guide body at the entry region is refracted into the liquid at a respective reflection face when the reflection face in question is immersed in the liquid but is totally reflected back into the light guide body in a direction on to the oppositely disposed region of the reflection faces and from there further to said end face when the said reflection face is not immersed in the liquid, and

measuring means for separately measuring the intensity of the respective light beam totally reflected by each said reflection face to said end face.

28. Device as set forth in claim 27

wherein at least some of the reflection faces are of a permanently reflective nature over a part of the periphery.

29. Device as set forth in claim 27

wherein said light guide body is of a circular cross-section.

30. Device as set forth in claim 27

wherein said light guide body is of an elliptical cross-section.

31. Device as set forth in claim 27

wherein the measuring means are disposed on the light exit region of said end face.

32. Device as set forth in claim 27

wherein the measuring means are disposed in the light exit region of said end face.

33. Device as set forth in claim 27 including

a light guide cable connecting the measuring means to said light exit region of said end face, said cable having at least one separate optical fiber for each said reflection face.

34. Device as set forth in claim 27

wherein said reflection faces form an angle of substantially 45°

with the direction of incident light.

35. Device as set forth in claim 27

wherein said measuring means includes at least one photosensor for each reflection face.

36. Device as set forth in claim 27

wherein said measuring means comprises a line sensor.

37. Device as set forth in claim 27 including

an evaluation means for implementing a plausibility check in respect of signals from said measuring means for recognising and eliminating measurement errors.

38. Device as set forth in claim 37 including

a microcontroller.

39. Device as set forth in claim 37 including

a light source for providing light for said light guide body,

wherein the limit band of the light source, the light guide spectrum of said light guide body and the sensitivity spectrum of the photosensor are matched to each other.

40. Device for determining a filling level in a liquid-filled container, including

an elongate light guide body having a side surface and an end face with an entry region for the entry of light into the light guide body and an exit region for the exit of light from the light guide body, the light guide body further comprising at said side surface steps defining at least two reflection faces at a spacing in the direction of elongation of the light guide body,

means for mounting the light guide body to a said container in a position such that the light guide body projects into the internal volume of the container,

the arrangement being such that in operation light entering the light guide body at said entry region is refracted into the liquid at a said reflection face immersed in the liquid but at a said reflection face clear of the liquid said light is totally reflected back into the light guide body on to the side surface at a location in opposite relationship to the location of its reflection and is totally reflected therefrom in a direction towards the exit region of said end face, and

measuring means for separately measuring the intensity of the light beam totally reflected at a said reflection face which is clear of the liquid.