Magnetic encoder and manufacturing method thereof

Patent metadata

Field	Value
Publication number	US-9752898-B2
Application number	US-201514707305-A
Country	US
Kind code	B2
Filing date	May 8, 2015
Priority date	Jun 4, 2014
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

An axial-type magnetic encoder includes an annular fixing member that is fabricated by press molding, and an annular plastic magnet that is attached by injection molding to a sensor-opposed surface of the annular fixing member. When the annular fixing member includes a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, the magnetic encoder has a high-form accuracy surface on the sensor-opposed surface more radially outward than a range of a diameter (d−2·r) determined by an inner diameter d of the cylindrical part and a radius r of a corner between the cylindrical part and the inward flange part. An outer diameter of the annular plastic magnet is positioned on the high-form accuracy surface.

First claim

The invention claimed is:

1. An axial-type magnetic encoder, comprising:
an annular fixing member that has a cylindrical part attached to a rotating body and an inward flange part extended more radially inward than an end edge of the cylindrical part and is fabricated by press molding; and
an annular plastic magnet that is attached by injection molding to a sensor-opposed surface of the annular fixing member, wherein
when the annular fixing member is composed of a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, the magnetic encoder has a high-form accuracy surface on the sensor-opposed surface more radially outward than a range of a diameter (d−2·r) determined by an inner diameter (d) of the cylindrical part and a radius (r) of a corner between the cylindrical part and the inward flange part, and
an outer diameter of the annular plastic magnet is positioned on the high-form accuracy surface.

2. The magnetic encoder according to claim 1 , wherein
the annular fixing member is composed of a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, and
the high-form accuracy surface is formed on the sensor-opposed surface by performing a press process to press stepwise a back surface of the sensor-opposed surface.

3. The magnetic encoder according to claim 1 , wherein
the annular fixing member is composed of a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, and
the high-form accuracy surface is formed on the sensor-opposed surface by performing a chamfering press process or stepwise press process to press by surface a round corner between the cylindrical part and the inward flange part.

4. The magnetic encoder according to claim 1 , wherein
the annular fixing member is composed of a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, and
the high-form accuracy surface is formed on the sensor-opposed surface by performing a bead process on an annular blank in a concentric manner to form a ribbed portion and then performing a press process to squeeze an outer side of the ribbed portion to mold the annular fixing member, thereby to eliminate the round corner between the cylindrical part and the inward flange part.

5. The magnetic encoder according to claim 1 , wherein
the high-form accuracy surface is formed on the sensor-opposed surface by performing a press process on a member composed of a large-diameter cylindrical part larger in diameter than the cylindrical part and a large-diameter inward flange part extended radially inward from an end edge of the large-diameter cylindrical part to narrow the large-diameter cylindrical part, and then setting a radially outward portion of the large-diameter inward flange part as an outward projection projecting radially outward.

6. A manufacturing method of an axial-type magnetic encoder, comprising:
a press molding step of fabricating by press molding an annular fixing member that has a cylindrical part attached to a rotating body and an inward flange part extended more radially inward than an end edge of the cylindrical part; and
an injection molding step of, while the annular fixing member is placed in an axial draw mold, injecting a dissolved annular plastic magnet material into the mold, wherein
the manufacturing method includes a step of, while the annular fixing member is composed of a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, forming by a press process a high-form accuracy surface on a sensor-opposed surface more radially outward than a range of a diameter (d−2·r) determined by an inner diameter (d) of the cylindrical part and a radius (r) of a corner between the cylindrical part and the inward flange part, and
the injection molding step is performed in the state where the annular fixing member is placed in the mold such that a mold matching surface is positioned on the high-accuracy surface.

7. The manufacturing method of a magnetic encoder according to claim 6 , wherein
the annular fixing member is composed of a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, and
the press process is a press process by which to press stepwise a back surface of the sensor-opposed surface.

8. The manufacturing method of a magnetic encoder according to claim 6 , wherein
the annular fixing member is composed of a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, and
the press process is a chamfering press process or stepwise press process by which to press by surface a round corner between the cylindrical part and the inward flange part.

9. The manufacturing method of a magnetic encoder according to claim 6 , wherein
the annular fixing member is composed of a cylindrical part and an inward flange part extended radially inward from an end edge of the cylindrical part, and
the press process is a press process by which to subject an annular blank to a bead process in a concentric manner to form a ribbed portion and then squeeze an outer side of the ribbed portion.

10. The manufacturing method of a magnetic encoder according to claim 6 , wherein the press process is a press process performed on a member composed of a large-diameter cylindrical part larger in diameter than the cylindrical part and a large-diameter inward flange part extended radially inward from an end edge of the large-diameter cylindrical part to narrow the large-diameter cylindrical part and form the cylindrical part.

Assignees

• Nakanishi Metal Works Co

Inventors

• Taki Masayuki
• Saitoh Mitsuru

Classifications

• G01P3/487

  delivered by rotating magnets · CPC title

• G01P3/443

  mounted in bearings (bearings F16C) · CPC title

• G01D5/2451

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

• F16C41/007 Primary

  Encoders, e.g. parts with a plurality of alternating magnetic poles · CPC title

• B29L2031/752

  Measuring equipment · CPC title