Position indicating encoder with magnetic end position determining elements

• US 5,793,201 A
• Filed: 02/21/1995
• Issued: 08/11/1998
• Est. Priority Date: 02/22/1994
• Status: Expired due to Fees

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Mauerberger, Herbert, Kranitzky, Walter, Nelle, Gunther
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US08/391,979
• Time in Patent Office: 1,267 Days
• Field of Search: 324/207.13, 324/207.14, 324/207.2, 324/207.21-207.26, 324/173, 324/174, 324/251, 324/252, 324/235, 324/227, 338/32 H, 307/309, 33/706, 33/707, 33/708
• US Class Current: 324/207.14
• CPC Class Codes: G01B 7/02 for measuring length, width or thickness G01B7/004, G01B7/12 take precedence
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 3/08 with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2457 Incremental encoders having reference marks

Abstract

An encoder for determining a position of an object and including a measuring standard, a standard carrier, and a scanner displaceable relative to the measuring standard for scanning the measuring standard, with the limit positions switches being formed as magnetic stripes secured in the end positions of the at least one of measuring standard and the standard carrier, and with the scanner including a Hall element for scanning the magnetic stripes.

Claims

1. An encoder for determining a position of an object, comprising:

a measuring standard with a graduation having, with respect to a measuring direction, righthand and lefthand regions each having a limit position region defining a limit position of the object;

first magnetic means located at the righthand region and defining the limit position region of the righthand region;

second magnetic means located at the lefthand region and defining the limit position region of the lefthand region;

a scanner displaceable relative to the measuring standard and including means for scanning same for determining the position of the object relative to the measuring standard and a Hall element for scanning the first and second magnetic means for generating a first Hall element voltage at the first magnetic means and a second Hall element voltage at the second magnetic means; and

a circuit for distinguishing the limit position regions of the righthand and lefthand regions by comparing the first and second Hall element voltages with at least one comparison voltage.

2. A encoder as set forth in claim 1, further comprising control means for controlling displacement of the scanner relative to the measuring standard, and wherein upon the Hall element reaching the limit position of one of the righthand and lefthand region, a turnoff signal is communicated to the control means for stopping displacement of the object.

3. An encoder as set forth in claim 1, wherein the first and second magnetic means are magnetic stripes having opposite sides defining north- and south-poles, the north-pole of the first magnetic stripe and the south-pole of the second magnetic stripe facing the scanner, and wherein the north- and south-poles define magnetic fields extending transverse to the measuring direction.

4. An encoder for determining a position of an object, comprising:

a measuring standard including a reference mark having, with respect to a measuring direction, righthand and lefthand regions;

a measuring standard carrier;

magnetic means provided on at least one of the measuring standard and the standard carrier for determining the righthand and lefthand regions and comprising a magnetic strip located at one of the righthand and lefthand regions of the reference mark; and

a scanner displaceable relative to the measuring standard in the measuring direction for scanning the measuring standard and including a Hall element for scanning the magnetic stripe and for generating a signal indicative of the righthand and lefthand regions of the reference mark upon scanning of the magnetic stripe.

5. An encoder as set forth in claim 4, wherein the magnetic stripe extends along an entire measuring length of the one of the righthand and lefthand regions, and wherein the magnetic means includes further magnetic stripes provided in the end regions of the measuring standard.

6. An encoder as set forth in claim 4, further comprising control means for controlling displacement of one of the measuring standard and the scanner, and wherein, upon occurrence of one of the monitoring circuit generating the error signal and the Hall element reaching a limit position, a turn-off signal is communicated the control means.

7. An encoder as set forth in claim 6, wherein the turn-off signal is communicated to two conductors in accordance with push-pull action.

8. An encoder as set forth in claim 4, wherein the Hall element has a plurality of outputs, wherein the encoder includes a plurality of conductors connecting the plurality of Hall element outputs with the monitoring circuit, wherein the generating means includes comparison means having a plurality of comparison voltages defining an error-free operational region of the Hall element, and wherein the error signal is generated when voltages of the plurality of conductors deviates from the comparison voltages.

9. An encoder as set forth in claim 8, wherein the monitorning circuit has bias voltage terminal means and reference potential terminal means, and wherein the plurality of conductors connecting the Hall element outputs to the monitoring circuit includes two conductors connected to the bias voltage terminal means and the reference potential terminal means, respectively, at which the error signal is generated.

10. An encoder as set forth in claim 8, wherein the comparison means includes two comparators each having two inputs, wherein the voltage of the conductor connected to the bias voltage terminal means, together with the bias voltage, are fed to one of the inputs of one of the comparators, and one of the comparison voltages is fed to another of the inputs of the one of the comparators, and wherein the voltage of the conductor connected to the reference potential terminal means, together with the reference potential, are fed to one of the inputs of another of the comparators, and another of the comparison voltages is fed to another of the outputs of another of the comparators.

11. An encoder as set forth in claim 4, further comprising a circuit for distinguishing two opposite end positions, wherein the Hall element is connected to the distinguishing circuit in which a Hall element voltage is compared with at least one comparison voltage and which generates two end position-defining signals in response to the comparison, wherein two outputs of the distinguishing circuit and the output of the evaluation circuit are connected to a logic circuit, with the two end position-defining signals being generated at the two outputs of the distinguishing circuit, respectively, and wherein the logic circuit has two outputs, a combination of signals generated at the two outputs of the logic circuit defining the end positions and a condition of the Hall element.

12. An encoder as set forth in claim 4, wherein the Hall element is associated with a stationary magnet that sets a predetermined magnitude of a Hall voltage of the Hall element different from 0 voltage.

13. An encoder as set forth in claim 12, wherein a magnetic field of the stationary magnetic is opposite to an external magnetic field to be crossed by the Hall element.

14. An encoder as set forth in claim 4, further comprising a circuit for monitoring a predetermined operation of the Hall element which is connected to the monitoring circuit, the monitoring circuit including an output and means for generating an error signal at the output upon deviation of an operational voltage of the Hall element from a predetermined operational voltage thereof.

15. An encoder for determining a position of an object, comprising

a measuring standard having, with respect to a measuring direction, righthand and lefthand regions each having a limit position region defining a limit position of the object;

a measuring standard carrier;

a magnetic means provided on at least one of the measuring standard carrier and the measuring standard and including magnetic strip means located at one of the righthand and lefthand regions of the measuring standard and defining the limit position region of the one of the righthand and lefthand regions; and

a scanner displaceable relative to the measuring standard and including means for scanning same for determining the position of the object relative to the measuring standard, and a Hall element for scanning the magnetic stripe means for determining both the righthand and lefthand regions and the limit position region to define the limit position of the object, the Hall element generating a signal for stopping an object displacement upon scanning the limit position region.

16. An encoder for determining a position of an object, comprising:

a measuring standard;

a measuring standard carrier;

magnetic means provided on one of the measuring standard and the standard carrier and including a magnetic stripe at least in one of limit position regions for defining a limit position of the object; and

a scanner displaceable relative to the measuring standard and including means for scanning same for determining the position of the object relative to the measuring standard, and a Hall element for scanning the magnetic stripe for determining a moment the object reaches the limit position region and for generating a signal for deactuating an object drive for stopping displacement of the object.

17. An encoder as set forth in claim 16, further comprising a circuit for controlling a predetermined operation of the Hall element.

18. An encoder as set forth in claim 17, wherein the measuring standard includes a graduation and a track with a plurality of reference marks associated with the graduation, and wherein the magnetic means comprises another magnetic stripe associated with one of the plurality of reference marks for selecting the one of the plurality of reference marks.

19. An encoder as set forth in claim 18, wherein the another magnetic stripe has opposite flat sides defining flat N- and S-poles, the another magnetic stripe being secured on at least one of the measuring standard and standard carrier, with one of the flat sides abutting a surface of the at least one of the measuring standard and standard carrier and another of the flat-sides, defining one of N- and S-poles, facing the scanner, and wherein the magnetic stripe and the another magnetic stripe associated with the one reference mark are so secured on the at least one of the measuring standard and the standard carrier that the magnetic stripe has the S-pole thereof facing the scanner and the another magnetic stripe has the N-pole thereof facing the scanner.

20. An encoder as set forth in claim 17, wherein the magnetic stripe having opposite flat sides defining flat N- and S-poles, the one magnetic stripe being secured on the at least one of the measuring standard and standard carrier, with one of the flat sides abutting a surface of the at least one of the measuring standard and standard carrier and another of the flat-sides, defining one of N- and S-poles, facing the scanner, and wherein the N- and S-pole define together a magnetic field extending transverse to the measuring direction.

21. An encoder as set forth in claim 20, wherein the magnetic means comprises a further magnetic stripe provided in another limit position region for defining another limit position of the object, wherein the further magnetic stripe has opposite flat sides defining flat N- and S-poles, with one of the flat sides abutting the surface of the at least one of the measuring standard and standard carrier and another of the flat sides defining one of the N- and S-poles facing the scanner, and wherein the magnetic stripe and the further magnetic stripe are so secured on the at least one of the measuring standard and the standard carrier that one of the magnetic stripe and the further magnetic stripe has the N-pole thereof facing the scanner and another of the magnetic stripe and the further magnetic stripe has the S-pole thereof facing the scanner to thereby provide for distinguishing the one and another limit positions of the object.

22. An encoder as set forth in claim 21, further comprising a circuit for distinguishing two opposite end positions, and wherein the Hall element is connected to the distinguishing circuit, in which a Hall element voltage is compared with at least one comparison voltage and which generate two end-position-defining output signals in response to the comparison.

23. An encoder as set fort in claim 21, further comprising a circuit for distinguishing two opposite end positions, wherein the Hall element is connected to the distinguishing circuit in which a Hall element voltage is compared with at least one comparison voltage and which generates two end position-defining signals in response to the comparison, wherein two outputs of the distinguishing circuit and the output of the evaluation circuit are connected to a logic circuit, with the two end position-defining signals being generated at the two outputs of the distinguishing circuit, respectively, and wherein the logic circuit has two outputs, a combination of signals generated at the two outputs of the logic circuit defining the end positions and a condition of the Hall element.

24. An encoder as set forth in claim 20, wherein the standard carrier is formed as a housing, and wherein the magnetic stripe is supported on the housing.

25. An encoder as set forth in claim 20, wherein the at least one of the measuring standard and the standard carrier has a groove for receiving the magnetic stripe.

26. An encoder as set forth in claim 25, wherein the standard carrier is formed as a housing, and the receiving groove is provided in the housing.

27. An encoder as set forth in claim 17, wherein the monitoring circuit includes an output and means for generating an error signal at the output upon deviation of an operational voltage of the Hall element from a predetermined operational voltage thereof.

28. An encoder as set forth in claim 27, further comprising control means for controlling displacement of one of the measuring standard and the scanner, and wherein, upon occurrence of one of the monitoring circuit generating the error signal and the Hall element reaching a limit position, a turnoff signal is communicated the control means.

29. An encoder as set forth in claim 27, wherein the Hall element has a plurality of outputs, wherein the encoder includes a plurality of conductors connecting the plurality of Hall element outputs with the monitoring circuit, wherein the monitoring circuit includes comparison means having a plurality of comparison voltages defining an error-free operational region of the Hall element, and wherein the error signal is generated when voltages of the plurality of conductors deviates from the comparison voltages.

30. An encoder as set forth in claim 29, wherein the monitoring circuit has bias voltage terminal means and reference potential terminal means, and wherein the plurality of conductors connecting the Hall element outputs to the monitoring circuit includes two conductors connected to the bias voltage terminal means and the reference potential terminal means, respectively, at which the error signal is generated.

31. An encoder as set forth in claim 29, wherein the comparison means includes two comparators each having two inputs, wherein the voltage of the conductor connected to the bias voltage terminal means, together with the bias voltage, are fed to one of the inputs of one of the comparators, and one of the comparison voltages is fed to another of the inputs of the one of the comparators, and wherein the voltage of the conductor connected to the reference potential terminal means, together with the reference potential, are fed to one of the inputs of another of the comparators, and another of the comparison voltages is fed to another of the outputs of another of the comparators.

32. An encoder as set forth in claim 27, wherein the Hall element is associated with a stationary magnet that sets a predetermined magnitude of a Hall voltage of the Hall element different from 0 voltage.

33. An encoder as set forth in claim 32, wherein a magnetic field of the stationary magnetic is opposite to an external magnetic field to be crossed by the Hall element.

34. An encoder as set forth in claim 17, wherein measuring standard defines a plurality of limit positions and includes a plurality of reference marks, and the magnetic means comprises a first plurality of magnetic stripes associated with the limit positions and a second plurality of magnetic stripes associated with the plurality of reference marks, the Hall element scanning both the first and second magnetic stripes.

35. An encoder as set forth in claim 17, wherein the magnetic stripe is glued to the at least one of the measuring standard and the standard carrier.