Angle measuring instrument

• US 20030093907A1
• Filed: 11/15/2002
• Published: 05/22/2003
• Est. Priority Date: 11/16/2001
• Status: Active Grant

• Current Assignee: Dr. Johannes Heidenhain GmbH
• Original Assignee: Dr. Johannes Heidenhain GmbH
• Inventors: Schroter, Andreas, Oberhauser, Johann, Tiemann, Marc
• Granted Patent: US 6,828,783 B2
• Time in Patent Office: Days
• US Class Current: 33/1.0PT
• CPC Class Codes: G01D 5/2053 by a movable non-ferromagnetic conductive element

Abstract

An angle measuring instrument having a device for determining a shaft angular position within one shaft rotation, and a device for determining a number of executed shaft rotations having a gear including at least one gear for converting the shaft rotary motion into rotary motion having a defined reduction ratio. The gear unit includes at least one gear wheel which rotates in a defined ratio to the shaft rotary motion. Devices are provided for generating sensor signals which are positionally dependent and are dependent upon the shaft rotations, in which the detecting device inductively scans reduced rotational movements of the shaft, and has alternating electrically conductive and electrically non-conductive graduation regions and a scanning device, movable relative to the graduation structure, including a device for generating a homogeneous electromagnetic field and a sensor device to scan the graduation structure and to transmit sensor signals which are dependent upon the shaft rotations.

Claims

1. An angle measuring instrument, comprising:

a first device configured to determine an absolute angular position of a rotating shaft within one shaft rotation; and

a second device configured to determine a number of executed shaft rotations having;

a gear including at least one gear unit configured to convert rotary motion of the shaft into a rotary motion having a defined reduced ratio, the gear unit including at least one gear wheel configured to rotate in a defined ratio to the rotary motion of the shaft; and

a detecting device configured to generate sensor signals positionally dependent and dependent upon the number of executed shaft rotations, the detecting device configured to scan reduced rotational movements of the shaft, said detecting device including;

a graduation structure having alternating electrically conductive and electrically non-conductive graduation regions; and

a scanning device movable relatively to the graduation structure, said scanning device including;

an excitation device configured to generate an electromagnetic excitation field; and

a sensor device configured to scan the graduation structure and to transmit the sensor signals dependent upon the number of executed shaft rotations.

2. The angle measuring instrument according to claim 1, wherein the detecting device is configured to scan the reduced rotational movements of the shaft one of inductively and capacitively.

3. The angle measuring instrument according to claim 1, wherein the sensor device includes at least one sensor track having at least two sensor windings phase-shifted with respect to one another and configured to emit phase-offset, periodically modulated sensor signals in response to a relative motion between the scanning device and the graduation structure, the excitation device including exciter elements positioned on both sides of the at least one sensor track configured to produce a most homogeneous possible configuration of the electromagnetic field in a region of the sensor track.

4. The angle measuring instrument according to claim 3, wherein the exciter elements include one of a current-carrying conductor track and a plurality of current-carrying conductor tracks arranged in parallel to one another, wherein the conductor tracks of the exciter elements are interconnected such that current flow is oriented in opposite directions in the conductor tracks positioned on both sides of the sensor track.

5. The angle measuring instrument according to claim 3, wherein the graduation structure is arranged on a circular graduation board and includes a first, circularly formed graduation track including an electrically conductive circular segment and an electrically non-conductive circular segment, the scanning device including a scanning structure positioned on a circular scanning board, a sensor device of which includes the sensor track assigned to the graduation track, the sensor windings of the sensor track configured to determine an absolute position over a detectable measuring range.

6. The angle measuring instrument according to claim 5, wherein the graduation structure includes a second circularly formed graduation track radially adjacent to the first graduation track and formed as a periodic sequence of a plurality of electrically conductive graduation regions and electrically non-conductive graduation regions, the scanning device including a scanning structure, a sensor device of which includes a second sensor track assigned to the second graduation track and a sensor winding of which is configured to enable an additional, incremental positional determination.

7. The angle measuring instrument according to claim 5, wherein the graduation structure is formed on one of a copper-coated graduation board, a structurally patterned metal disk, a partially metallized plastic part and a metallized gear wheel.

8. The angle measuring instrument according to claim 1, wherein the first device configured to determine the absolute angular position of the rotating shaft within one shaft rotation includes:

a detecting device having a graduation structure positioned on a graduation device; and

a scanning device mounted on a scanning board configured to transmit the sensor signals which are dependent upon the absolute angular position of the rotating shaft within one shaft rotation, the output signals of the detecting device configured to determine the absolute angular position of the rotating shaft within one shaft rotation, and the sensor signals of the detecting device configured to determine a number of executed shaft rotations transmittable to an evaluation unit.

9. The angle measuring instrument according to claim 8, wherein the graduation device and the scanning device of the first device configured to determine the absolute angular position of the rotating shaft within one shaft rotation and the evaluation unit are positioned coaxially with respect to the shaft.

10. The angle measuring instrument according to claim 9, wherein the graduation device and the scanning device of the first device configured to determine the absolute angular position of the rotating shaft within one shaft rotation are positioned on one side of the evaluation unit, and the graduation device and the scanning device of the second device configured to determine the number of executed shaft rotations on another side of the evaluation unit.

11. The angle measuring instrument according to claim 9, wherein the scanning device of the first device configured to determine the absolute angular position of the rotating shaft within one shaft rotation and the scanning device of the second device configured to determine the number of executed shaft rotations on both sides of a common scanning board are positioned opposite to a particular graduation devices assigned to the scanning devices.

12. The angle measuring instrument according to claim 1, wherein the graduation structure is arranged on a peripheral surface of a cylindrical member and includes a first graduation track including an electrically conductive and an electrically non-conductive peripheral cylinder section, the scanning device includes a scanning structure arranged on a cylindrical housing and has a sensor device having a sensor track assigned to the graduation structure and sensor windings wound on the peripheral cylinder surface are configured to enable an absolute positional determination over a detectable measuring range.

13. The angle measuring instrument according to claim 12, wherein the graduation structure has a second graduation track axially adjacent to the first graduation track and formed as a periodic sequence of a plurality of electrically conductive graduation regions and electrically non-conductive graduation regions and the scanning device includes a scanning structure positioned on the cylindrical housing, the sensor device including a second sensor track assigned to the graduation structure and the sensor windings wound on the peripheral cylinder surface configured to enable an additional incremental positional determination.

14. The angle measuring instrument according to claim 12, wherein the graduation structure is formed on one of a copper-coated cylindrical member, a structurally patterned metal cylinder, and on a surface and peripheral area of a partially metallized plastic part on a metallized gear wheel.

15. The angle measuring instrument according to claim 7, wherein the graduation structure is fabricated by one of a two-component injection-molding process including inserts and by coating a substructure.

16. The angle measuring instrument according to claim 15, wherein the scale-graduation structure includes one of a metallic material and of a conductive plastic, and the graduation structure is formed by one of height gradations and recesses.

17. The angle measuring instrument according to claim 12, wherein the sensor windings are arranged on a flexible conductor secured to the peripheral surface of the cylindrical housing, radially encircling the housing.

18. The angle measuring instrument according to claim 3, wherein the detecting device configured to determine the number of executed shaft rotations has a plurality of gear units for a defined reduction of the rotational movements of the shaft, the exciter elements configured to receive excitation signals assigned to the gear units and modulated to a carrier frequency, and the exciter elements configured to be fed excitation signals modulated to a carrier frequency which differs by the carrier frequency that is applied to the exciter elements.

19. The angle measuring instrument according to claim 18, wherein the exciter elements assigned to the gear units are fed by a common exciter resonant circuit.

20. The angle measuring instrument according to claim 19, wherein the scanning devices of individual gear units are connected via a multiplex device to a common evaluation unit.

21. The angle measuring instrument according to claim 20, wherein the scanning devices assigned to the gear units are configured to amplify, filter and demodulate two high-frequency modulated sensor signals which are 90°

out-of-phase, the measuring instrument further comprising a device configured to receive amplified low-frequency sensor signals sent via an analog/digital converter, configured to calculate positional values and configured to send an encoded output signal to at least one of a display device and follow-up electronics.

22. The angle measuring instrument according to claim 21, wherein the device configured to calculate positional values is configured to undertake an adjustment using a table of correction values.

23. The angle measuring instrument according to claim 21, wherein the multiplex device, the analog/digital converter, a device configured to store a table of correction values, and at least one of the display device and the follow-up electronics are configured to receive a clock-pulse signal transmitted by a clock-pulse generator.

24. The angle measuring instrument according to claim 14, wherein the graduation structure is fabricated by one of a two-component injection-molding process including inserts and by coating a substructure.

25. The angle measuring instrument according to claim 24, wherein the scale-graduation structure includes one of a metallic material and of a conductive plastic, and the graduation structure is formed by one of height gradations and recesses.