Position measuring instrument

• US 5,386,642 A
• Filed: 02/04/1993
• Issued: 02/07/1995
• Est. Priority Date: 02/04/1992
• Status: Expired due to Fees

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Metz, Gerald, Spies, Alfons
• Primary Examiner(s): Wirthlin, Alvin
• Application Number:
  US08/013,704
• Time in Patent Office: 733 Days
• Field of Search: 33/708, 33/706, 324/207.21, 338/32 R
• US Class Current: 33/708
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01P 13/04 Indicating positive or negative direction of a linear movement or clockwise or anti-clockwise direction of a rotational movement

Abstract

A position measuring instrument for measuring the relative position of two objects movable relative to one another. The position measuring instrument comprises a periodic measurement scale division having a period t and a scanner unit, wherein the scanner unit and the periodic measurement scale division move relative to one another in a measuring direction. In addition, the scanner unit comprises four groups (A-D) each comprising at least four magnetoresistive elements (A_n -D_n) (n=1, 2, 3, 4, . . .), which are interconnected in the form of a series-parallel circuit to form a half bridge circuit having an upper branch and a lower branch. The upper branch comprises a magnetoresistive element from each group (A-D) and the lower branch comprises a corresponding magnetoresistive element from each group (A-D). Furthermore, the magnetoresistive elements of the upper branch are offset from the corresponding magnetoresistive elements of the lower branch by t/2. The position measurement instrument further comprises an evaluation device to form position measurement values from position-dependent output signals generated by the magnetoresistive elements in response to relative movement between the periodic measurement scale division and the scanner unit.

Claims

1. A position measuring instrument for measuring the relative position of a first object and a second object movable relative to one another, comprising:

a periodic measurement scale division having a period t and secured to said first object;

a scanner unit secured to said second object, wherein said scanner unit and said periodic measurement scale division move relative to one another in a measuring direction;

said scanner unit comprising four groups (A-D) each comprising at least four magnetoresistive elements (A_n -D_n) (n=1, 2, 3, 4, . . .), wherein said at least four magnetoresistive elements (A_n -D_n) (n=1, 2, 3, 4, . . .) of each of said four groups (A-D) are interconnected in the form of series-parallel circuits to form two half bridge circuits having an upper branch and a lower branch;

wherein said upper branch comprises a magnetoresistive element from each group (A-D) and said lower branch comprises a corresponding magnetoresistive element from each group (A-D);

said magnetoresistive elements of said upper branch are offset from the corresponding magnetoresistive elements of said lower branch by t/2; and

an evaluation device to form position measurement values from position-dependent output signals generated by said magnetoresistive elements in response to relative movement between said periodic measurement scale division and said scanner unit.

2. The position measuring instrument of claim 1, wherein each group (A-D) extends over a period t of said periodic measurement scale division.

3. The position measuring instrument of claim 1, wherein when there are m (m=4, 5, . . .) total magnetoresistive elements (A_n -D_n) of each group (A-D), their respective mutual spacing is t/m.

4. The position measuring instrument of claim 1, wherein when there are four magnetoresistive elements (A_n -D_n) of each group (A-D), their respective mutual spacing is t/4.

5. The position measuring instrument of claim 1, wherein said half bridge circuit comprises a quarter bridge having at least four magnetoresistive elements interconnected arbitrarily among one another.

6. The position measuring instrument of claim 1, wherein said periodic measurement scale division comprises magnetized regions of alternatingly opposite polarity in said measuring direction.

7. The position measuring instrument of claim 1, wherein said periodic measurement scale division comprises alternating regions of good magnetic conductivity and poor magnetic-conductivity in said measuring direction.

8. The position measuring instrument of claim 7, wherein said scanner unit comprises a permanent magnet.

9. The position measuring instrument of claim 7, wherein said periodic measurement scale division comprises alternatingly successive lands and indentations in said measuring direction.

10. The measuring instrument of claim 1, wherein said evaluation device has an interpolation unit.

11. A position measuring instrument for measuring the relative position of a first object and a second object movable relative to one another, comprising:

a periodic measurement scale division having a period t and secured to said first object;

a scanner unit, wherein said scanner unit and said periodic measurement scale division move relative to one another in a measuring direction;

said scanner unit comprising eight groups (A-H) each comprising at least four magnetoresistive elements (An-Hn) (n=1, 2, 3, 4, . . .), wherein said at least four magnetoresistive elements (A_n -H_n) (n=1, 2, 3, 4, . . .) of each of said eight groups (A-H) are interconnected in the form of a series-parallel circuit to form a full bridge circuit having a left-hand branch and a right-hand branch;

wherein said left-hand branch comprises a magneto-resistive element from each group (A-H) and said right-hand branch comprises a corresponding magnetoresistive element from each group (A-H);

said magnetoresistive elements of said left-hand branch are offset from the corresponding magnetoresistive elements of said right-hand branch by t/2; and

an evaluation device to form position measurement values from position-dependent output signals generated by said magnetoresistive elements in response to relative movement between said periodic measurement scale division and said scanner unit.

12. The position measuring instrument of claim 11, wherein each group (A-H) extends over a period t of said periodic measurement scale division.

13. The position measuring instrument of claim 11, wherein when there are m (m=4, 5, . . .) total magnetoresistive elements (A_n -H_n) of each group (A-H), their respective mutual spacing is t/m.

14. The position measuring instrument of claim 11, wherein when there are four magnetoresistive elements (A_n -D_n) of each group (A-D), their respective mutual spacing is t/4.

15. The position measuring instrument of claim 11, wherein said full bridge circuit comprises a quarter bridge having at least four magnetoresistive elements interconnected arbitrarily among one another.

16. The position measuring instrument of claim 11, wherein said periodic measurement scale division comprises magnetized regions of alternatingly opposite polarity in said measuring direction.

17. The position measuring instrument of claim 11, wherein said periodic measurement scale division comprises alternating regions of good magnetic conductivity and poor magnetic conductivity in said measuring direction.

18. The position measuring instrument of claim 17, wherein said scanner unit comprises a permanent magnet.

19. The position measuring instrument of claim 17, wherein said periodic measurement scale division comprises alternatingly successive lands and indentations in said measuring direction.

20. The measuring instrument of claim 11, wherein said evaluation device has an interpolation unit.

21. A position measuring instrument for measuring the relative position of a first object and a second object movable relative to one another, comprising:

a periodic measurement scale division having a period t and secured to said first object;

a scanner unit secured to said second object, wherein said scanner unit and said periodic measurement scale division move relative to one another in a measuring direction;

said scanner unit comprising eight groups (A-H) each comprising at least four magnetoresistive elements (A_n -H_n) (n=1, 2, 3, 4, . . .), wherein said at least four magnetoresistive elements (A_n -H_n) (n=1, 2, 3, 4, . . .) of each of said four groups (A-H) are interconnected in the form of a series-parallel circuit to form a full bridge circuit having an upper branch and a lower branch;

wherein said upper branch comprises a magnetoresistive element from each group (A-H) and said lower branch comprises a corresponding magnetoresistive element from each group (A-H);

said magnetoresistive elements of said upper branch are offset from the corresponding magnetoresistive elements of said lower branch by t/2; and

an evaluation device to form position measurement values from position-dependent output signals generated by said magnetoresistive elements in response to relative movement between said periodic measurement scale division and said scanner unit.

22. The position measuring instrument of claim 21, wherein each group (A-H) extends over a period t of said periodic measurement scale division.

23. The position measuring instrument of claim 21, wherein when there are m (m=4, 5, . . .) total magnetoresistive elements (A_n -H_n) of each group (A-H), their respective mutual spacing is t/m.

24. The position measuring instrument of claim 21, wherein when there are four magnetoresistive elements (A_n -H_n) of each group (A-H), their respective mutual spacing is t/4.

25. The position measuring instrument of claim 21, wherein said full bridge circuit comprises a quarter bridge having at least four magnetoresistive elements interconnected arbitrarily among one another.

26. The position measuring instrument of claim 21, wherein said periodic measurement scale division comprises magnetized regions of alternatingly opposite polarity in said measuring direction.

27. The position measuring instrument of claim 21, wherein said periodic measurement scale division comprises alternating regions of good magnetic conductivity and poor magnetic conductivity in said measuring direction.

28. The position measuring instrument of claim 27, wherein said scanner unit comprises a permanent magnet.

29. The position measuring instrument of claim 27, wherein said periodic measurement scale division comprises alternatingly successive lands and indentations in said measuring direction.

30. The measuring instrument of claim 21, wherein said evaluation device has an interpolation unit.