Magnetic encoder device and rotation detection device

Patent metadata

Field	Value
Publication number	US-9976874-B2
Application number	US-201414904223-A
Country	US
Kind code	B2
Filing date	Jul 2, 2014
Priority date	Jul 16, 2013
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

A magnetic encoder device ( 3 ) of the present invention includes a base portion ( 33 ) having a mounting surface ( 33 b ) for mounting to a rotary shaft ( 2 ), a cored bar ( 35 ) fitted and fixed over the base portion ( 33 ), and a double-row magnetic encoder track ( 30 ) formed on the cored bar ( 35 ). Through movement of each of magnetic poles of the magnetic encoder track ( 30 ) over a region opposed to a magnetic sensor ( 4 ), an angle of the rotating rotary shaft is detected. The base portion ( 33 ) is formed of a sintered metal, and the mounting surface ( 33 b ) is subjected to sizing.

First claim

The invention claimed is:

1. A magnetic encoder device, comprising:
a rotary member; and
a magnetic encoder track formed on the rotary member, the magnetic encoder track comprising a plurality of magnetic poles arranged in a circumferential direction of the rotary member, each of the plurality of magnetic poles of the magnetic encoder track being movable in a region opposed to a magnetic sensor to detect an angle of rotation of a rotary shaft, wherein:
the rotary member has a first surface for mounting the rotary member to the rotary shaft, and a second surface for positioning the rotary member during formation of the magnetic encoder track by magnetization;
the first surface and the second surface of the rotary member are formed of a sintered metal, the sintered metal having a large number of micropores; and
at least the first surface and the second surface of the sintered metal are subjected to sizing.

2. The magnetic encoder device according to claim 1 , wherein:
the rotary member comprises:
a base portion made of the sintered metal having the first surface; and
a supporting member fitted and fixed over the base portion; and

the magnetic encoder track is formed on the supporting member.

3. The magnetic encoder device according to claim 1 , wherein the rotary member comprises a base portion made of the sintered metal having the first surface, and a molded portion formed by a rubber, a resin or a sintered compact containing a magnetic powder, and
the magnetic encoder track is formed on the molded portion.

4. The magnetic encoder device according to claim 3 , wherein:
the base portion comprises a first engagement portion;
the molded portion comprises a second engagement portion configured to be engaged with the first engagement portion in the circumferential direction of the rotary member; and
the first engagement portion and the second engagement portion construct a rotation stopper.

5. The magnetic encoder device according to claim 4 , wherein the second engagement portion of the molded portion is molded by using the first engagement portion of the base portion as a molding die.

6. The magnetic encoder device according to claim 3 , wherein:
the base portion is formed of a sintered metal containing iron; and
an oxide film is formed at least on a contact region of a surface of the base portion with the molded portion.

7. The magnetic encoder device according to claim 6 , wherein the oxide film is further formed on the first surface of the base portion.

8. The magnetic encoder device according to claim 3 , wherein:
the base portion is formed by molding and sintering a base powder; and
a mean particle diameter of the base powder is set to from 60 μm to 100 μm.

9. The magnetic encoder device according to claim 8 , wherein the base powder contains iron powder as a main component.

10. The magnetic encoder device according to claim 3 , wherein a rough surface portion having a larger surface roughness than a surface roughness of the first surface is formed on a contact region of a surface of the base portion with the molded portion.

11. The magnetic encoder device according to claim 10 , wherein the rough surface portion is formed at least on the surface of the base portion, which is opposed to the magnetic encoder track.

12. The magnetic encoder device according to claim 3 , wherein:
any one of an outer peripheral surface and an end surface of the base portion is opposed to the magnetic sensor;
a thickness-reduced portion is formed between the outer peripheral surface and the end surface of the base portion; and
an angle (θ) of inclination formed by a line connecting a first boundary portion corresponding to a boundary between the thickness-reduced portion and the outer peripheral surface and a second boundary portion corresponding to a boundary between the thickness-reduced portion and the end surface with respect to a sensing direction of the magnetic sensor is set to satisfy θ<45°.

13. The magnetic encoder device according to claim 12 , wherein the thickness-reduced portion comprises a chamfer.

14. The magnetic encoder device according to claim 12 , wherein the thickness-reduced portion comprises a chamfer and a flat surface adjacent to the chamfer.

15. The magnetic encoder device according to claim 3 , wherein a material containing a thermoplastic resin and a magnetic powder as main components is used as a material of the molded portion.

16. The magnetic encoder device according to claim 1 , wherein the magnetic encoder track comprises a first track and a second track, each comprising magnetic poles.

17. A rotation detection device, comprising:
the magnetic encoder device of claim 1 ;
a rotary shaft; and
a magnetic sensor opposed to the magnetic encoder track.

18. A method for producing a magnetic encoder device comprising: a rotary member; and a magnetic encoder track formed on the rotary member, the rotary member comprising a base portion made of sintered metal having a first surface and a supporting member fitted and fixed over the base portion, and the magnetic encoder track comprising a plurality of magnetic poles arranged in a circumferential direction of the rotary member, each of the plurality of magnetic poles of the magnetic encoder track being movable in a region opposed to a magnetic sensor to detect an angle of rotation of a rotary shaft, wherein:
the rotary member has the first surface for mounting the rotary member to the rotary shaft, and a second surface for positioning the rotary member during formation of the magnetic encoder track by magnetization, the method comprising:
forming the first surface and the second surface of the rotary member of a sintered metal, the sintered metal having a large number of micropores;
sizing at least the first surface and the second surface of the sintered metal;
forming the magnetic encoder track on the supporting member; and
magnetizing the magnetic encoder track under a state in which the supporting member is fixed to the base portion.

Assignees

• Ntn Toyo Bearing Co Ltd

Inventors

• Takahashi Toru
• Nakajima Tatsuo
• Hakamata Hiroyuki
• Uemoto Ikuo
• Miyazaki Shinji
• Harano Takuji
• Oda Takayuki

Classifications

• G01D5/246

  by varying the duration of individual pulses · CPC title

• G01D5/24438 Primary

  Special design of the sensing element or scale · CPC title

• G01D5/2452

  incorporating two or more tracks having an (n, n+1, ...) relationship · CPC title

• G01D5/14 Primary

  influencing the magnitude of a current or voltage · CPC title