Relative rotational angular displacement detection device having a magnetic detection unit that detects a magnetic flux of an annular plane portion from a surface of a ring body

Patent metadata

Field	Value
Publication number	US-9771096-B2
Application number	US-201514601222-A
Country	US
Kind code	B2
Filing date	Jan 20, 2015
Priority date	Sep 14, 2012
Publication date	Sep 26, 2017
Grant date	Sep 26, 2017

Abstract

A relative rotational angular displacement detection device includes a pair of rotatable members rotatable relative to each other in a circumferential direction. A permanent magnet is attached to one of the rotatable members and includes magnetic poles magnetized in an axial direction of the axis of rotation and arranged to alternate in polarity in the circumferential direction. A magnetic flux guiding ring includes an annular ring body attached to the other of the rotatable members and is arranged coaxially with the axis of rotation, and a plurality of protruding portions each having a circumferential width smaller than the circumferential width of the magnetic pole. A magnetic detection unit is configured to detect magnetic fluxes of the ring body of the magnetic flux guiding ring. The magnetic flux guiding ring is magnetized depending on the positions of the protruding portions relative to the positions of the magnetic poles.

First claim

The invention claimed is:

1. A relative rotational angular displacement detection device, comprising:
a pair of rotatable members rotatable relative to each other about an axis of rotation in a circumferential direction;
a permanent magnet attached to one of the pair of rotatable members and including magnetic poles magnetized in an axial direction of the axis of rotation, the magnetic poles being arranged so as to alternate in polarity in the circumferential direction, the magnetic poles each having a circumferential width;
a magnetic flux guiding ring including
an annular ring body, the annular ring body being attached to the other of the pair of rotatable members and arranged coaxially with the axis of rotation, the annular ring body including an annular plane portion that extends in a direction intersecting with the axial direction of the axis of rotation,
a plurality of protruding portions each having a circumferential width, the plurality of protruding portions protruding from the annular ring body toward one side with respect to radial directions radiating from the axis of rotation, the plurality of protruding portions being arranged so as to partially overlap the permanent magnet when seen in the axial direction of the axis of rotation,
each respective protruding portion of at least one of the plurality of protruding portions being configured such that the circumferential width of the respective protruding portion, at a portion thereof that overlaps an edge of the permanent magnet at an other side with respect to one of the radial directions, is smaller than the circumferential width of one of the magnetic poles of the permanent magnet at an edge of the one magnetic pole at the other side when seen in the axial direction of the axis of rotation,
the annular ring body being magnetized with a strength of magnetization changing depending on positions of the protruding portions relative to positions of the magnetic poles; and

a magnetic detection unit facing one surface of the annular ring body with a gap therebetween with respect to the axial direction of the axis of rotation, the magnetic detection unit being configured to detect magnetic fluxes of the annular plane portion from the one surface of the annular ring body, wherein
the annular ring body is formed of a single piece.

2. The relative rotational angular displacement detection device as recited in claim 1 , wherein
each of the protruding portions has a tapered shape with the circumferential width thereof decreasing.

3. The relative rotational angular displacement detection device as recited in claim 1 , wherein
each of the protruding portions extends outward in a respective radial direction of the radial directions.

4. The relative rotational angular displacement detection device as recited in claim 1 , wherein
the relative rotational angular displacement detection device is configured to detect the magnetic fluxes by the magnetic detection unit without positively forming a magnetic closed loop circuit.

5. The relative rotational angular displacement detection device as recited in claim 1 , wherein the magnetic detection unit includes a magnetic sensor for detecting magnetic fluxes oriented in the axial direction of the axis of rotation among magnetic fluxes of the annular plane portion.

6. The relative rotational angular displacement detection device as recited in claim 5 , wherein at least one of the annular ring body and the magnetic sensor is arranged at a position different from the positions of the protruding portions with respect to the axial direction of the axis of rotation.

7. The relative rotational angular displacement detection device as recited in claim 6 ,
wherein the magnetic detection unit includes an intermediate yoke having a first plane portion, and
further wherein the first plane portion is arranged between the magnetic sensor and the annular ring body and arranged so as to face the annular plane portion of the annular ring body with a gap therebetween with respect to the axial direction of the axis of rotation.

8. The relative rotational angular displacement detection device as recited in claim 7 , wherein a surface area of the first plane portion is smaller than a surface area of the annular plane portion.

9. The relative rotational angular displacement detection device as recited in claim 7 ,
wherein at least one of the annular ring body, the intermediate yoke and the magnetic sensor is arranged at a position different from the positions of the protruding portions with respect to the radial directions of the axis of rotation.

10. The relative rotational angular displacement detection device as recited in claim 1 , wherein
the magnetic poles form an N-pole group and an S-pole group,
the magnetic flux guiding ring has a first state in which the strength of magnetization is relatively low and a second state in which the strength of the magnetization is relatively high compared to the first state,
in the first state, the protruding portions are positioned relative to the magnetic poles to have a first difference between a strength of magnetization of the magnetic flux guiding ring magnetized by the N-pole group and a strength of magnetization of the magnetic flux guiding ring magnetized by the S-pole group,
in the second state, the protruding portions are positioned relative to the magnetic poles to have a second difference between the strength of magnetization of the magnetic flux guiding ring magnetized by the N-pole group and the strength of the magnetization of the magnetic flux guiding ring magnetized by the S-pole group, the second difference being larger than the first difference.

11. The relative rotational angular displacement detection device as recited in claim 10 , wherein
in the first state, the protruding portions are positioned relative to the magnetic poles such that the magnetic flux guiding ring is magnetized substantially equally by the N-pole group and the S-pole group,
in the second state, the protruding portions are positioned relative to the magnetic poles such that the magnetic flux guiding ring is magnetized by substantially only one of the N-pole group and the S-pole group.

12. A torque detection device comprising:
the relative rotational angular displacement detection device as recited in claim 1 ; and
an elastic member arranged between the pair of rotatable members, the elastic member configured to constantly apply a biasing force in a relative rotation direction to the pair of rotatable members,
wherein the pair of rotatable members is provided with a relative rotation restriction part,
the relative rotation restriction part being configured to prevent rotation of the rotatable members relative to each other after a first of the pair of rotatable members is rotated relative to a second of the rotatable members through a predetermined rotational angle against the biasing force of the elastic member.

13. A torque control device comprising:
the relative rotational angular displacement detection device as recited in claim 1 ;
a rotation driving member connected to a first of the pair of rotatable members, the rotation driving member configured such that a user gives a rotational force thereto;
a power source configured to give a rotational force to a second of the rotatable members; and
a control unit configured to, when the first rotatable member is rotated relative to the second rotatable member through a predetermined rotational angle, control the rotational force that the power source gives to the second rotatable member depending on an output of the magnetic detection unit.

14. A power a

Assignees

• Yamaha Motor Co Ltd

Inventors

• Hino Haruyoshi
• Nakamura Kazuto

Classifications

• G01D5/2451 Primary

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

• B62D5/046 Primary

  Controlling the motor · CPC title

• G05B11/011

  details of the correcting means · CPC title

• B62M6/50

  characterised by detectors or sensors, or arrangement thereof · CPC title

• A61G5/04

  motor-driven (A61G5/06 takes precedence; motor-operated rests A61G5/12; for vehicles with handlebars, equipped with three or more wheels B62K5/003, B62K5/023) · CPC title