Magnetic encoder and bearing device including magnetic encoder

Patent metadata

Field	Value
Publication number	US-9476735-B2
Application number	US-201414499874-A
Country	US
Kind code	B2
Filing date	Sep 29, 2014
Priority date	Oct 24, 2013
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

A magnetic encoder 1 including a support member 2 attached to a rotating body 12 and a magnet member 3 fixed to the support member 2 , the support member 2 and the magnet 4 are not attached to each other using an adhesive but the support member 2 and the plastic magnet 4 are joined together by molding shrinkage or wrap-around form of the magnet 4 , and the material for the magnet 4 is selected such that the value of the ratio ((αp−αm)/εc) of a difference (αp−αm) between flowing-direction linear expansion coefficient (αp) of the magnet 4 and linear expansion coefficient (αm) of the support member 2 , to tensile breaking strain (εc) of the material for the magnet 4 is equal to or less than a value beginning at a threshold (Nth) based on a prescribed value of cycle member at thermal shock destructive test.

First claim

The invention claimed is:

1. A magnetic encoder comprising:
an annular support member that is formed from a steel plate and attached to a rotating body; and
an annular magnet member that is fixed to the support member and has N and S poles magnetized circumferentially at regular intervals in a multipolar manner, wherein
the magnet member is a plastic magnet,
there is no adhesive layer between the support member and the plastic magnet, and the support member and the plastic magnet are joined together by molding shrinkage of the plastic magnet or wrap-around form of the plastic magnet, and
the material for the plastic magnet is selected such that the value of the ratio ((αp−αm)/εc) of a difference (αp−αm) between flowing-direction linear expansion coefficient (αp) of the plastic magnet and linear expansion coefficient (αm) of the support member, to tensile breaking strain (εc) of the material for the plastic magnet is equal to or less than a value beginning at a threshold (Nth) based on a prescribed value of cycle number at thermal shock destructive test, and tensile strength (σc) of the plastic magnet is equal to or more than a value beginning at a threshold (Fth) based on a prescribed value of axial binding force between the plastic magnet and the support member, and
wherein the magnetic encoder is an axial type, and includes a joint portion resulting from molding shrinkage at a radially outer peripheral part of the plastic magnet and includes a joint portion resulting from wrap-around from a radially inner peripheral part of the plastic magnet.

2. A bearing device comprising the magnetic encoder according to claim 1 , wherein
the rotating body is an inner ring of a bearing, and
the bearing device further includes a cup-shaped protective cover that is press-fitted into an outer ring of the bearing as a non-rotating body to cover the magnetic encoder.

Assignees

• Nakanishi Metal Works Co

Inventors

• Ito Yoshihiro

Classifications

• F16C33/723

  Shaft end sealing means, e.g. cup-shaped caps or covers · CPC title

• G01P3/487 Primary

  delivered by rotating magnets · CPC title

• F16C2326/02

  Wheel hubs or castors · CPC title

• G01D5/145

  influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06) · CPC title

• G01P3/443

  mounted in bearings (bearings F16C) · CPC title