Position measuring system

• US 20010052771A1
• Filed: 05/01/2001
• Published: 12/20/2001
• Est. Priority Date: 05/24/2000
• Status: Active Grant

• Current Assignee: Balluff Verwaltungsges mbH
• Original Assignee: Balluff Verwaltungsges mbH
• Inventors: Jagiella, Manfred
• Granted Patent: US 6,714,004 B2
• Time in Patent Office: Days
• US Class Current: 324/207.16
• CPC Class Codes: F15B 15/2846 using detection of markings, e.g. markings on the piston rod
• CPC Class Codes: F15B 15/2861 using magnetic means
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01D 2205/775 Tapered profiles
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence
• CPC Class Codes: G01D 5/2033 controlling the saturation of a magnetic circuit by means of a movable element, e.g. a magnet

Abstract

In order to provide a position measuring system, comprising a transmitter, a sensor with an inductive element to which the transmitter is coupled electromagnetically and an evaluating unit, wherein the sensor and the transmitter are adapted to be positioned relative to one another, whereby said position measuring system will be of simple construction and can thus be manufactured economically while being employable universally, provision is made for the inductive element to be coupled to an oscillator which is affected by the Q factor and/or the effective inductance of the inductive element, for the Q factor and/or the effective inductance of the inductive element to be determined by the size of an effective sensor region to which the transmitter is coupled, and/or by the size of an effective transmitter region which is coupled to an effective sensor region, and for the sensor and/or the transmitter to be formed in such a manner that the size of the effective sensor region to which the transmitter is coupled, and/or the size of the effective transmitter region which is coupled to the effective sensor region is dependent upon the relative position between the transmitter and the sensor in a direction transverse to a direction of separation therebetween.

Claims

1. A position measuring system comprising a transmitter (32;

54;

90;

102;

140), a sensor (12;

44;

84;

100;

134) with an inductive element (16;

50;

94;

136) to which the transmitter is coupled electromagnetically, and an evaluating unit (24;

46;

86;

132), wherein the sensor and the transmitter are adapted to be positioned relative to one another, characterised in that the inductive element (16;

50;

94;

136) is coupled to an oscillator which is affected by the Q factor and/or the effective inductance of the inductive element, in that the Q factor and/or the effective inductance of the inductive element (16;

50;

94;

136) is determined by the size of an effective sensor region to which the transmitter is coupled, and/or by the size of an effective transmitter region which is coupled to an effective sensor region, and in that the sensor and/or the transmitter are formed in such a manner that the size of the effective sensor region to which the transmitter is coupled, and/or the size of the effective transmitter region which is coupled to the effective sensor region is dependent on the relative position between the transmitter and the sensor in a direction transverse to a direction of separation (58;

106) therebetween.

2. A position measuring system in accordance with

claim 1

, characterised in that the sensor (12;

44;

84;

100;

134) and/or the transmitter (32;

54;

90;

102;

140) are formed in such a manner that an overlapping region between a projection of an effective transmitter surface area onto the sensor having an effective sensor surface area is dependent on the relative position between the sensor and the transmitter in a direction transverse to the direction of projection (58;

106).

3. A position measuring system in accordance with

claim 1

, characterised in that the evaluating unit (24;

46;

86;

132) determines a characteristic value of the oscillator.

4. A position measuring system in accordance with

claim 3

, characterised in that a frequency of the oscillator is determined.

5. A position measuring system in accordance with

claim 3

, characterised in that an amplitude of the oscillator is determined.

6. A position measuring system in accordance with

claim 1

, characterised in that the inductive element (16;

50;

94;

136) is essentially flat.

7. A position measuring system in accordance with

claim 6

, characterised in that the inductive element (16;

50;

94;

136) is designed as a printed coil.

8. A position measuring system in accordance with

claim 1

, characterised in that the evaluating unit (24;

46;

86;

132) is arranged on a circuit board (14;

48;

88;

130) upon which the inductive element (16;

50;

94;

136) is seated.

9. A position measuring system in accordance with

claim 1

, characterised in that the measurable distance between the transmitter (32;

54;

90;

140) and the sensor (12;

44;

84;

134) is essentially determined by a linear dimension of the inductive element (16;

50;

94;

136).

10. A position measuring system in accordance with

claim 1

, characterised in that the transmitter (32;

54;

90;

102;

140) is a passive element.

11. A position measuring system in accordance with

claim 1

, characterised in that the transmitter (140) comprises a magnet.

12. A position measuring system in accordance with

claim 11

, characterised in that a soft magnetic material (138) is arranged at or in the vicinity of the inductive element (136).

13. A position measuring system in accordance with

claim 12

, characterised in that the soft magnetic material (138) is arranged in such a manner that it is adapted to be brought into a state of local saturation in an effective sensor region.

14. A position measuring system in accordance with

claim 12

, characterised in that a soft magnetic material (138) is deposited on a circuit board (130) upon which the inductive element (136) is seated.

15. A position measuring system in accordance with

claim 12

, characterised in that a circuit board (130), upon which the inductive element (136) is seated, has a soft magnetic material (138) wound therearound.

16. A position measuring system in accordance with

claim 12

, characterised in that the soft magnetic material is arranged in a form such that the dimensions of its shape transverse to a measurement path vary along said measurement path.

17. A position measuring system in accordance with

claim 16

, characterised in that the soft magnetic material is arranged in the form of a triangle.

18. A position measuring system in accordance with

claim 1

, characterised in that the inductive element (50;

94;

136) is designed in such a manner that its shape transverse to a measurement path (60) varies along said measurement path (60).

19. A position measuring system in accordance with

claim 18

, characterised in that the inductive element (50;

136) comprises triangular windings.

20. A position measuring system in accordance with

claim 1

, characterised in that the inductive element (94) extends over an angular range for the purposes of measuring revolutions.

21. A position measuring system in accordance with

claim 20

, characterised in that the angular range comprises a substantially full circle.

22. A position measuring system in accordance with

claim 1

, characterised in that the transmitter comprises an electrically or magnetically conductive element (32;

54;

90;

102).

23. A position measuring system in accordance with

claim 1

, characterised in that a projected overlapping area between an effective transmitter area and the inductive element (100) varies along a measurement path.

24. A position measuring system in accordance with

claim 23

, characterised in that the transmitter (102;

114;

122) is designed in such a manner that an effective transmitter region, which is coupled to the inductive element (100), varies in shape transverse to a measurement path along said measurement path.

25. A position measuring system in accordance with

claim 24

, characterised in that the transmitter (102;

114) is provided with a triangular structure (108;

112).

26. A position measuring system in accordance with

claim 24

, characterised in that the effective transmitter region is formed by a coating (108;

112) on the transmitter (102;

114).

27. A position measuring system in accordance with

claim 24

, characterised in that the transmitter (122) is provided with recesses (124).

28. A position measuring system in accordance with

claim 24

, characterised in that the sensor is comprised by an inductive proximity sensor (98) which comprises an oscillatory circuit with an inductive element.

29. A position measuring system in accordance with

claim 22

, characterised in that a magnetic screening (34, 42, 98) is provided for the inductive element.

30. A position measuring system in accordance with

claim 1

, characterised by a plurality of inductive elements (50, 66;

100, 110).

31. A position measuring system in accordance with

claim 30

, characterised in that the sensor comprises a plurality of tracks formed by inductive elements.

32. A position measuring system in accordance with

claim 30

, characterised in that a plurality of inductive elements (50, 66;

100;

110) are so arranged and interconnected with reference to the transmitter (54;

102) that a position measurement process can be carried out which is substantially independent of the spacing of the transmitter (54;

102) from the sensor.

33. A position measuring system in accordance with

claim 32

, characterised in that a transmitter (54;

102) is positioned between two mutually spaced inductive elements (50, 66;

100;

110).

34. A position measuring system in accordance with

claim 33

, characterised in that the inductive elements are directed in opposite senses.

35. A position measuring system in accordance with

claim 33

, characterised in that a process of forming the difference with regard to the sensor signals from the two inductive elements (50, 66;

100;

110) is carried out.

36. A position measuring system in accordance with

claim 33

, characterised in that a process of forming the sum with regard to the sensor signals from the two inductive elements (50, 66;

100;

110) is carried out.

37. A position measuring system in accordance with

claim 6

, characterised in that the inductive element is arranged on a flexible support means.

38. A position measuring system in accordance with

claim 37

, characterised in that the inductive element is arranged on a flexible foil.

39. A position measuring system in accordance with

claim 1

, characterised in that the sensor and/or the transmitter are constructed in such a manner that, by virtue of the corresponding shaping, a certain characteristic curve of the position measuring system is established for a sensor signal in dependence on a measurement path.

40. A position measuring system in accordance with

claim 1

, characterised in that an error signal is derivable from the evaluating unit, wherein the evaluating unit is adapted to be checked as to whether one or more parameters of the inductive element lie within a tolerance range.