Multi-turn absolute magnetic encoder

Patent metadata

Field	Value
Publication number	US-9389099-B2
Application number	US-201414760355-A
Country	US
Kind code	B2
Filing date	Jan 10, 2014
Priority date	Jan 11, 2013
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

A multi-turn absolute magnetic encoder, comprising (M+1) counting units, a single-turn signal processing unit, and a multi-turn signal processing unit. Each counting unit comprises counting wheels with a cylindrical ring permanent magnet fixed thereon, and a tunneling magnetoresistive angular displacement sensor. The magnetoresistive angular displacement sensor is located within a region in a detection plane of the permanent magnet at within a specific radius range from the axis of the cylindrical ring permanent magnet, within the detection plane the angle of a component of a magnetic field generated by the permanent magnet is linearly proportional to the rotation angle of the cylindrical ring permanent magnet. The single-turn signal processing unit calculates and outputs a code characterizing the absolute angular position of the input shaft based on the sensor signal of the first counting unit; and the multi-turn signal processing unit calculates and outputs the integer number of turns of the input shaft based on the sensor signals of the second counting unit to (M+1) counting units.

First claim

The invention claimed is:

1. A multiturn magnetic absolute encoder, comprising:
a first (M+1) counting unit, where M is an integer greater than or equal to 1;
a single turn signal processing unit; and
a multiturn signal processing unit,
wherein, each counting unit includes:
a permanent magnet coaxially mounted in a counting wheel; and
a tunneling magnetoresistive angular displacement sensor to detect the magnetic field component produced by the permanent magnet in the detection plane of the permanent magnet and output a signal, the permanent magnet has a cylindrical ring structure, and contains a first permanent magnet unit and a second permanent magnet unit, where the first permanent magnet unit and the second permanent magnet unit are symmetrically located with respect to the diametral cross section of the permanent magnet, the magnetization of the first permanent magnet unit and the magnetization of the second permanent magnet unit are parallel to the central axis cylindrical ring permanent magnet, but aligned in opposite directions, or the magnetization of the first permanent magnet unit and the magnetization of the second permanent magnet unit are aligned perpendicular to the diametral cross-sectional plane of the cylindrical ring permanent magnet, and aligned in same direction, within each counting unit, the tunneling magnetoresistive angular displacement sensor located in a specific region of the detection plane of the cylindrical ring permanent magnet within a certain radial distance from the cylindrical ring permanent magnet's axis, inside this region defined by this specific radius, the permanent magnet produces a magnetic field in the detection plane with a component oriented at an angle that is linearly related to the rotation angle of the rotating permanent magnet, a single turn processing unit to process the output signal of the first counting unit in order to calculate a code representative of the absolute rotational position of the counting wheel within one rotation, and a multiturn signal processing unit to calculate and output the integer number of rotations of the input shaft using sensor signals from the second to the M+1 counting units.

2. The multiturn magnetic absolute encoder of claim 1 , wherein the first counting wheel is directly fixed to the input shaft.

3. The multiturn magnetic absolute encoder of claim 1 , wherein the second counting unit to the M counting unit each includes a reduction gear set, wherein each counting gear set output shaft is the input shaft of the next counting unit, and a counting wheel is fixed on the output shaft, additionally a multiturn signal processing unit is used to calculate and output the number of rotations of each input shaft from the tunneling magnetoresistive angular displacement sensor signals of each counting wheel.

4. The multiturn magnetic absolute encoder of claim 1 , wherein the value of M ranges from 1 to 10.

5. The multiturn magnetic absolute encoder of claim 1 , wherein the number of revolutions of counting wheel m relative to counting wheel m+1 has a turns ratio of N:1, where m is an integer from 1 to M, and N is an integer greater than 1.

6. The multiturn magnetic absolute encoder of claim 5 , wherein the number of revolutions of counting wheel m relative to counting wheel m+1 has a turns ratio of 10:1.

7. The multiturn magnetic absolute encoder of claim 1 , wherein the permanent magnet has an outer diameter of 3 to 200 mm, an inner diameter of 1 to 100 mm, and a thickness of 1 to 50 mm.

8. The multiturn magnetic absolute encoder of claim 1 , wherein the tunneling magnetoresistive angular displacement sensor includes two orthogonal uniaxial angle sensors or a biaxial tunneling magnetoresistive angular displacement sensor with two Wheatstone bridge sensors rotated at 90 degrees with respect to each other.

9. The multiturn magnetic absolute encoder of claim 1 , wherein the permanent magnets have a detection plane that is located adjacent and parallel to the end circular face of the permanent magnet.

10. The multiturn magnetic absolute encoder of claim 1 , wherein the tunneling magnetoresistive angular displacement sensors are located in the detection surface of the permanent magnet within a distance of 1 to 5 mm from the circular end face.

11. The multiturn magnetic absolute encoder of claim 1 , wherein the magnetization of the first permanent magnet unit and the magnetization of the second permanent magnet unit are the same size.

12. The multiturn magnetic absolute encoder of claim 1 , wherein, the permanent magnet is composed one or more of the following materials including RECo 5 , where RE=Sm and/or Pr; RE 2 TM 17 , where RE=Sm, TM=Fe, Cu, Co, Zr and/or Hf; RE 2 TM 14 B, where RE=Nd, Pr, and/or Dy, TM=Fe and/or Co; FeCrCo alloy; an NbFeB alloy, or the permanent magnet is comprised of permanent magnet powder embedded in plastic, rubber, or a resin composite.

Assignees

• Multidimension Technology Co Ltd

Inventors

• Deak James Geza
• Zhou Zhimin

Classifications

• G01D5/145

  influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06) · CPC title

• G01D5/2497 Primary

  Absolute encoders (G01D5/2454 takes precedence) · CPC title

• G01D5/147

  influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other · CPC title

• G01D2205/26

  Details of encoders or position sensors specially adapted to detect rotation beyond a full turn of 360°, e.g. multi-rotation · CPC title