Motion measuring device

• US 20030080728A1
• Filed: 08/07/2002
• Published: 05/01/2003
• Est. Priority Date: 08/10/2001
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Finkler, Roland, Daalmans, Gabriel
• Granted Patent: US 6,850,053 B2
• Time in Patent Office: Days
• US Class Current: 324/164
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence
• CPC Class Codes: G01P 15/003 Kinematic accelerometers, i.e. measuring acceleration in relation to an external reference frame, e.g. Ferratis accelerometers G01P15/001, G01P15/16, G01P15/165 take precedence
• CPC Class Codes: G01P 3/49 using eddy currents
• CPC Class Codes: G01P 3/505 by using eddy currents

Abstract

In the inductive motion sensor, there are provided magnetic field generating means (4, 5, 7, 8) for generating a magnetic exciting field and a measuring device for measuring a mutually induced measurement magnetic field as a measure of the motion. The measuring device is arranged with an offset from the magnetic field generating means in the motion direction and is thereby no longer subjected to the temperature-dependent variations of the exciting field.

Claims

1. Device for measuring a motion of a moving body (2), which is electrically conducting in at least one region, with

a) magnetic field generating means (4, 5, 7, 8) for producing a magnetic field (B₀), which penetrates the electrically conducting region of the moving body in at least one spatially limited partial area (5),

b) at least one measuring device (30, 32, 33) for measuring a measurement magnetic field (B_F) which is induced by electrical currents (I_F) in the electrically conducting region of the moving body depending on the motion of the moving body, and which is a measure for at least one motion variable of the moving body,

wherein

c) the measuring device is offset in the motion direction of the moving body relative to the partial area in the moving body or relative to the magnetic field generating means.

2. Device according to claim 1,wherein the measuring device is arranged proximate to the magnetic field generating means, in particular with a spacing from the magnetic field generating means or from the partial area penetrated by the magnetic field in the motion direction that is a smaller than the dimension of the partial area penetrated by the magnetic field in the moving body as measured in the motion direction.

3. Device according to claim 1 or claim 2, wherein the measuring device is arranged in the motion direction immediately following the magnetic field generating means or the partial area in the moving body penetrated by the magnetic field.

4. Device according to one or more of the preceding claims, wherein the at least one measuring device measures the measurement magnetic field at a location where it is oriented essentially perpendicular to the motion direction of the moving body, or a component of the measurement magnetic field that is oriented essentially perpendicular to the motion direction.

5. Device according to one or more of the preceding claims, with at least two measuring devices, which are arranged on opposite sides of the moving body, preferably directly opposite to each other.

6. Device according to one or more of the preceding claims, with at least two measuring devices that are arranged on the same side of the moving body.

8. Device according to one or more of the claims 5 to 7, wherein the measurement signals of two measuring devices that depend on the motion of the moving body are superimposed with the same polarity, whereas interfering signals caused by changes in the distances between the moving body and the measuring devices are superimposed with opposite polarity.

10. Device according to one or more of the preceding claims, wherein at least two pairs of measuring devices are provided that are arranged on opposite sides of the moving body, wherein the pairs in the motion direction are arranged on opposite sides of the magnetic field generating means.

11. Device according to one or more of the claims 5 to 8, wherein the measuring devices have essentially the same distance from the magnetic field generating means and/or the moving body, or are arranged essentially symmetrically to the magnetic field generating means and/or the magnetic body.

12. Device according to one or more of the claims 5 to 7, wherein the measuring devices are constructed essentially in the same manner and/or produce essentially measurement signals of the same strength for the same motion of the moving body.

13. Device according to one or more of the preceding claims, wherein magnetic flux guiding means for guiding the measurement magnetic field are associated with the measuring device, which preferably form a closed magnetic circuit.

14. Device according to one or more of the preceding claims, wherein magnetic flux guiding means for guiding the measurement magnetic field of the magnetic field generating means are associated with the measuring device, which preferably form a closed magnetic circuit.

15. Device according to claim 13 and claim 14, wherein the magnetic flux guiding means for the magnetic field generating means and the magnetic flux guiding means for the measuring device(s) are formed separate of each other.

16. Device according to claim 13 and claim 14, wherein at least partially common magnetic flux guiding means are provided for the magnetic field generating means and the measuring device.

17. Device according to one or more of the claims 13 to 16, wherein the magnetic flux guiding means are made at least predominately of a magnetically conducting and/or a soft magnetic material.

18. Device according to one or more of the claims 13 to 17, wherein the magnetic flux conducting means have a high electrical conductivity and/or low eddy current losses and/or a low noise.

19. Device according to claim 13 and claim 14, or one of the claims depending from claim 13 and claim 14, wherein the magnetic flux guiding means for the magnetic field generating means have a higher magnetic permeability and/or higher eddy current losses than the magnetic flux guiding means for the measuring device.

20. Device according to claim 13 or one of the claims depending from claim 13, wherein the magnetic flux guiding means for the measuring device are made at least predominately of a material made of iron powder or a ferritic magnetic material.

21. Device according to claim 14 or one of the claims depending from claim 14, wherein the magnetic flux guiding means for the magnetic field generating means are made at least predominately of soft iron.

22. Device according to claim 14 or one of the claims depending from claim 14, wherein the at least one and preferably each measuring device is arranged with an offset in the motion direction adjacent to the magnetic flux guiding means for the magnetic field generating means.

23. Device according to one or more of the preceding claims, wherein the at least one measuring device comprises at least one induction coil.

24. Device according to claim 23, wherein each induction coil surrounds a magnetic flux conducting element.

25. Device according to claim 24, wherein at least one magnetically conducting termination element is arranged on the end faces of each induction coil.

26. Device according to one or more of the preceding claims, wherein the magnetic field generating means comprises at least one permanent magnet (4, 5, 7, 8) for generating the magnetic field, preferably at least two permanent magnet (7, 8) with opposite magnetic poles (S, N) facing each other, with the moving body (2) moving or being moveable between the magnetic poles.

27. Device according to claim 26 and referring back to claim 14, wherein at least one measuring device is arranged in the motion direction at least partially within the magnetic flux conducting means for the magnetic field generating means and with an offset next to the permanent magnets.

28. Device according to one or more of the claims 14 to 16 or 18 to 22, wherein the magnetic field generating means and/or the magnetic flux conducting means and/or the measuring device and/or the magnetic flux conducting elements and/or termination elements of the at least one induction coil are secured to at least one associated support or to a common support and/or are thermally coupled with the support.

29. Device according to claim 28, wherein the support has a good thermal conductivity and, in particular, is made of a metal.

30. Device according to one or more of the preceding claims, wherein the at least one measuring device includes at least one magnetic field sensor, in particular a Hall sensor, a magneto-resistive sensor or a field plate.

31. Device according to one or more of the preceding claims, wherein each measuring device is arranged essentially outside the magnetic field of the magnetic field generating means.

32. Device according to one or more of the preceding claims for measuring a motion of a moving body that rotates or is rotatable about a rotation axis, wherein at least two measuring heads, each having at least one measuring device, and magnetic field generating means are provided which are arranged diametrically opposed with respect to the rotation axis.

33. Device according to one or more of the preceding claims, wherein the magnetic field generating means produce a magnetic field that penetrates the electrically conductive region of the moving body in a partial area that is contiguous or continuous in the motion direction of the moving body.

34. Device according to one or more of the claims 1 to 32, wherein the magnetic field generating means produce a magnetic field that penetrates the electrically conductive region of the moving body in the motion direction of the moving body in at least two spaced apart partial areas.

7. Device with at least two measuring devices, which are arranged in the motion direction on opposite sides of the magnetic field generating means or of the partial area penetrated by the magnetic field.

9. Device according to claim 7 or claim 8, wherein the two measuring devices produce measurement signals with the same polarity for the same motion of the moving body, or are electrically connected with opposite polarity.