WINDING AND SCALE CONFIGURATION FOR INDUCTIVE POSITION ENCODER

• US 20180113004A1
• Filed: 12/21/2017
• Published: 04/26/2018
• Est. Priority Date: 08/24/2016
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Cook, Ted Staton
• Granted Patent: US 10,612,943 B2
• Time in Patent Office: Days
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence
• CPC Class Codes: G01D 5/2216 by a movable ferromagnetic element, e.g. a core

Abstract

An electronic position encoder includes a scale comprising first and second pattern tracks including respective signal modulating scale patterns, a detector and a signal processing configuration. The detector includes first-track and second-track field generating coil portions that surround first and second interior areas aligned with the first pattern track and second pattern track, respectively. The first-track and second-track field generating coil portions each include first and second elongated portions extending along the measuring axis direction, connected to end portions extending along a y-axis direction transverse to the measuring axis. The detector includes sensing elements that span across the first and second interior areas along the y-axis direction. A nominal y-axis trace width dimension of the elongated portions is at least 0.1 times a y-axis width of the first and/or second interior areas. In various implementations, a shielded end section may be used to connect the elongated portions.

Claims

1. An electronic position encoder usable to measure a relative position between two elements along a measuring axis direction that coincides with an x-axis direction, the electronic position encoder comprising:

a scale extending along the measuring axis direction and including a signal modulating scale pattern comprising first and second pattern tracks arranged parallel to one another, each pattern track having a track width dimension along a y-axis direction that is perpendicular to the x-axis direction between its interior boundary that is closest to the other pattern track and its exterior boundary that is farthest from the other pattern track, and each pattern track comprising signal modulating elements that are arranged to provide a spatially varying characteristic which changes as a periodic function of position along the x-axis direction;

a detector portion configured to be mounted proximate to the pattern tracks and to move along the measuring axis direction relative to the pattern tracks, the detector portion comprising;

a field generating coil configuration fixed on a substrate, comprising;

a first-track field generating coil portion surrounding a first interior area aligned with the first pattern track and having a nominal first interior area length dimension along the x-axis direction and a nominal first interior area width dimension along the y-axis direction and generating a changing first magnetic flux in the first interior area in response to a coil drive signal, and

a second-track field generating coil portion surrounding a second interior area aligned with the second pattern track and having a nominal second interior area length dimension along the x-axis direction and a nominal second interior area width dimension along the y-axis direction and generating a changing magnetic flux in the second interior area in response to the coil drive signal; and

a plurality of sensing elements arranged along the x-axis direction and fixed on the substrate, each of the sensing elements having a nominal sensing element width dimension along the y-axis direction that spans the first and second interior areas, wherein the plurality of sensing elements are configured to provide detector signals which respond to a local effect on the changing magnetic flux provided by adjacent signal modulating elements of the scale pattern; and

a signal processing configuration that is operably connected to the detector portion to provide the coil drive signal and that determines the relative position between the detector portion and the scale pattern based on detector signals input from the detector portion,

wherein;

the field generating coil configuration comprises;

an input portion comprising at least two connection portions that connect the coil drive signal from the signal processing configuration to the field generating coil configuration;

first-track inside and outside elongated portions extending along the x-axis direction adjacent to the first interior area, the first-track inside elongated portion located adjacent to the first-track interior boundary and the first-track outside elongated portion located adjacent to the first-track exterior boundary, the first-track inside and outside elongated portions each having a nominal first-track generating trace width dimension along the y-axis direction; and

second-track inside and outside elongated portions extending along the x-axis direction adjacent to the second interior area, the second-track inside elongated portion located adjacent to the second-track interior boundary and the second-track outside elongated portion located adjacent to the second-track exterior boundary, the second-track inside and outside elongated portions each having a nominal second-track generating trace width dimension along the y-axis direction;

at least a majority of the nominal sensing element width dimension is included between the first-track outside elongated portion and the second-track outside elongated portion, and

the field generating coil configuration is configured such that each nominal first-track generating trace width dimension is at least 0.1 times the nominal first interior area width dimension, and each nominal second-track generating trace width dimension is at least 0.1 times the nominal second interior area width dimension.

2. The electronic position encoder of claim 1, wherein each nominal first-track generating trace width dimension is at least 0.15 times the nominal first interior area width dimension and each nominal second-track generating trace width dimension is at least 0.15 times the nominal second interior area width dimension.

3. The electronic position encoder of claim 2, wherein each nominal first-track generating trace width dimension is at least 0.25 times the nominal first interior area width dimension and each nominal second-track generating trace width dimension is at least 0.25 times the nominal second interior area width dimension.

4. The electronic position encoder of claim 2, wherein each nominal first-track generating trace width dimension is at least 0.5 times the nominal first interior area width dimension and each nominal second-track generating trace width dimension is at least 0.5 times the nominal second interior area width dimension.

5. The electronic position encoder of claim 1, wherein each nominal first-track and second-track generating trace width dimension is at least 25 times a skin depth of the elongated portions at a nominal operating frequency defined corresponding to the detector signals that arise in response to the changing magnetic flux.

6. The electronic position encoder of claim 1, wherein:

the field generating coil configuration and the sensing elements are insulated from one another;

the sensing element width dimension of at least one sensing element is greater than a dimension spanning between the first-track outside elongated portion and the second-track outside elongated portion and extends beyond an interior edge of at least one of the first-track outside elongated portion and the second-track outside elongated portion by an amount defined as an overlap dimension; and

the field generating coil configuration is configured such that each nominal generating trace width dimension is larger than the overlap dimension.

7. The electronic position encoder of claim 6, wherein the elongated portions are fabricated in a first layer of a printed circuit board, and the sensing elements comprise conductive loops fabricated in one or more layers of the printed circuit board that include a layer different than the first layer, at least in a vicinity of the overlap dimension.

8. The electronic position encoder of claim 1, wherein at least a majority of the nominal sensing element width dimension is included within the first and second interior areas.

9. The electronic position encoder of claim 1, wherein the substrate comprises a printed circuit board, and at least the field generating coil configuration comprises conductive traces fabricated on the printed circuit board.

10. The electronic position encoder of claim 1, wherein the interior track boundaries of the first and second pattern tracks are located proximate to one another.

11. The electronic position encoder of claim 1, wherein:

the first and second pattern tracks each comprise the same type of signal modulating elements that are arranged according to a same spatial period or wavelength W along the x-axis direction in the first and second pattern tracks, wherein the signal modulating elements in the second pattern track are offset along the measuring axis direction by a nominal scale track offset of approximately W/2 relative to the signal modulating elements in the first pattern track;

the field generating coil configuration is configured to generate the first-track changing magnetic flux with a first polarity in the first interior area, and generate the second-track changing magnetic flux with a second polarity that is opposite to the first polarity in the second interior area; and

the plurality of sensing elements comprise magnetic flux sensing loops formed by conductive traces fabricated on a printed circuit board, wherein at least a majority of the magnetic flux sensing loops each span the first and second interior areas along the y-axis direction and provide the same sensing loop polarity in the first and second interior areas.

12. The electronic position encoder of claim 1, wherein:

the first and second pattern tracks each comprise the same type of signal modulating elements that are arranged according to a same spatial period or wavelength W along the x-axis direction in the first and second pattern tracks, wherein the signal modulating elements in the second pattern track are offset along the measuring axis direction by a nominal scale track offset of approximately W/2 relative to the signal modulating elements in the first pattern track;

the field generating coil configuration is configured to generate the first-track changing magnetic flux with a first polarity in the first interior area, and generate the second-track changing magnetic flux with a second polarity that is the same as the first polarity in the second interior area; and

the plurality of sensing elements comprise magnetic flux sensing loops formed by conductive traces fabricated on a printed circuit board, wherein at least a majority of the magnetic flux sensing loops each span the first and second interior areas along the y-axis direction and include a cross over or twisting of their conductive traces to provide opposite sensing loop polarities in the first and second interior areas.

13. The electronic position encoder of claim 12, wherein for at least a majority of the magnetic flux sensing loops, the cross over or twisting of their conductive traces is located in a region including the first-track inside elongated portion and the second-track inside elongated portion between the first interior area and the second interior area.

14. The electronic position encoder of claim 1, wherein the first-track field generating coil portion and the second-track field generating coil portion each comprises a single turn surrounding their interior area.

15. The electronic position encoder of claim 1, wherein the field generating coil configuration comprises at least one shielded end portion that extends generally along the y-axis direction and connects to at least one elongated portion that is nominally located at an elongated portion z distance from a front surface of the detector portion that faces the scale pattern, along a z axis direction that is perpendicular to the x-axis and y-axis directions, wherein that shielded end portion comprises:

a shielded end section that is nominally located at a shielded end section z distance from the front surface of the detector portion, wherein the shielded end section z distance is greater than the elongated portion z distance; and

the detector portion further comprises a conductive shield region extending along the x-axis and y-axis directions and nominally located at a shield region z distance from the front surface, wherein the shield region z distance is smaller than the shielded end section z distance, and the shield region is located between at least part of the shielded end section and the front surface of the detector portion.

16. The electronic position encoder of claim 15, wherein the at least one shielded end portion includes a first-track shielded end portion that connects the first-track inside and outside elongated portions, and a second-track shielded end portion that connects the second-track inside and outside elongated portions.

17. The electronic position encoder of claim 15, wherein the elongated portions are fabricated in a first layer of a printed circuit board, the shielded end section is fabricated in a second layer of the printed circuit board, and the shield region is fabricated in a layer of the circuit board that is closer to the front surface than the second layer of the printed circuit board.

18. The electronic position encoder of claim 17, wherein the shield region is fabricated in a layer of the printed circuit board that is located between the first layer and the second layer.

19. The electronic position encoder of claim 15, wherein a connection between an elongated portion and the shielded end section comprises a printed circuit board feedthrough that extends along the z-axis direction.

20. The electronic position encoder of claim 19, wherein the shield region is fabricated in a layer of the printed circuit board that is located between the first layer and the second layer, and the printed circuit board feedthrough passes through an opening fabricated in the shield region.