Patent ID: 9476735
Filing Date: 2016-10-25
CPC Classification: B29C,B29K,F16C,G01D,G01P

Claim Text:
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.