OPTICAL ENTIRE-CIRCUMFERENCE ENCODER AND MOTOR SYSTEM

• US 20110227518A1
• Filed: 03/15/2011
• Published: 09/22/2011
• Est. Priority Date: 03/19/2010
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Yaskawa Denki
• Original Assignee: Kabushiki Kaisha Yaskawa Denki
• Inventors: INOUE, Sadatoshi, Muraoka, Jiro
• Granted Patent: US 8,575,876 B2
• Time in Patent Office: Days
• US Class Current: 318/400.4
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders

Abstract

An optical entire-circumference encoder includes a plurality of rotation slits provided to transmit light at an equal pitch radially around a rotation axis as a center in a rotation track. A plurality of fixed slits is provided to transmit light at an equal pitch in a plurality of regions radially around the rotation axis as the center in a fixed track. A plurality of light receivers is disposed in a vicinity of the rotation axis to receive a light guided by the light guide in the regions respectively. The fixed slits in one of the regions and the fixed slits in another region adjacent to the one of the regions among the regions in the fixed track are formed so that a phase difference by which a rotation direction of the rotor is determined occurs between light reception signals of the plurality of light receivers.

Claims

1. An optical entire-circumference encoder comprising:

a rotation track which is rotatable to follow a rotor rotatable around a rotation axis and which is provided to be in a ring shape around the rotation axis as a center;

a plurality of rotation slits provided to transmit light at an equal pitch radially around the rotation axis as the center in the rotation track;

a fixed track which is fixedly set in a ring shape in correspondence with the rotation track on one side of the rotation track and which is divided into a plurality of regions in a circumferential direction of the fixed track;

a plurality of fixed slits provided to transmit light at an equal pitch in the plurality of regions radially around the rotation axis as the center in the fixed track;

a light guide to guide light which passed through the plurality of fixed slits and the plurality of rotation slits toward a vicinity of the rotation axis while condensing the light; and

a plurality of light receivers disposed in the vicinity of the rotation axis to receive the light guided by the light guide in the plurality of regions respectively, the plurality of fixed slits in one of the plurality of regions and the plurality of fixed slits in another region adjacent to the one of the plurality of regions among the plurality of regions in the fixed track being formed so that a phase difference by which a rotation direction of the rotor is determined occurs between light reception signals of the plurality of light receivers.

2. The optical entire-circumference encoder according to claim 1,

wherein a number of the plurality of regions is an integral multiple of four.

3. The optical entire-circumference encoder according to claim 1,

wherein the light guide has a plurality of light shields to block light over the plurality of regions, and

wherein the plurality of light shields are provided to be in positions corresponding to borders of the plurality of regions.

4. The optical entire-circumference encoder according to claim 1,

wherein the plurality of regions of the fixed track are set rotation-symmetrically of a number of the plurality of regions around the rotation axis, and

wherein the plurality of fixed slits in each of two regions among the plurality of regions having a point-symmetrical relation with respect to the rotation axis are formed so that a phase difference of 0°

or 180°

in electric angle occurs between light reception signals of two light receivers among the plurality of light receivers.

5. The optical entire-circumference encoder according to claim 4, further comprising:

a position data generator configured to generate position data including the rotation direction of the rotor based on a result of performing addition or subtraction on two light reception signals obtained from the two regions having the point-symmetrical relation.

6. The optical entire-circumference encoder according to claim 1, further comprising:

a substrate including a light source to emit light and the plurality of light receivers, the light source being positioned on the rotation axis on a side opposite to the rotation track in the fixed track; and

a reflector disposed on another side of the rotation track and provided to reflect light which passed through the plurality of fixed slits and, after that, passed through the plurality of rotation slits toward the plurality of rotation slits,

wherein the light guide is formed to extend from the rotation axis to the fixed track so as to cover the substrate while sandwiching the substrate between the light guide and the fixed track,

wherein the light guide irradiates the fixed track with light emitted from the light source disposed on the rotation axis, and

wherein the light guide guides light reflected by the reflector, after that, sequentially passed through the plurality of rotation slits and the plurality of fixed slits to the plurality of light receivers while condensing the light toward the rotation axis.

8. The optical entire-circumference encoder according to claim 2,

wherein the light guide has a plurality of light shields to block light over the plurality of regions, and

wherein the plurality of light shields are provided to be in positions corresponding to borders of the plurality of regions.

7. A motor system comprising:

a motor device configured to rotate a rotary shaft;

an optical entire-circumference encoder coupled to the rotary shaft and configured to measure position of the rotary shaft, the optical entire-circumference encoder comprising;

a rotation track which is rotatable follow the rotor and which is provided to be in a ring shape around the rotation axis as a center;

a plurality of rotation slits provided to transmit light at an equal pitch radially around the rotation axis as the center in the rotation track;

a fixed track which is fixedly set in a ring shape in correspondence with the rotation track on one side of the rotation track and which is divided into a plurality of regions in a circumferential direction of the fixed track;

a plurality of fixed slits provided to transmit light at an equal pitch in the plurality of regions radially around the rotation axis as the center in the fixed track;

a light guide to guide light which passed through the plurality of fixed slits and the plurality of rotation slits toward a vicinity of the rotation axis while condensing the light; and

a plurality of light receivers disposed in the vicinity of the rotation axis to receive the light guided by the light guide in the plurality of regions respectively, the plurality of fixed slits in one of the plurality of regions and the plurality of fixed slits in another region adjacent to the one of the plurality of regions among the plurality of regions in the fixed track being formed so that a phase difference by which a rotation direction of the rotor is determined occurs between light reception signals of the plurality of light receivers; and

a controller configured to control rotation of the motor device based on the position measured by the optical entire-circumference encoder.