Variation of the Pole Length in Pole-Oriented Bonded Rings due to the Location and Number of Injection Points

Katharina H Kurth,Dietmar Drummer

doi:10.1155/2017/8241859

Abstract

Polymer bonded magnets are compounds consisting of a polymer matrix with embedded hard magnetic filler particles. These materials are mainly used in applications in actor or sensor technology. One example is the application as multipolar encoder wheel in magnetic sensors. Depending on the application different requirements have to be fulfilled, such as a high pole length accuracy and repeatability. This investigation deals with the production of multipolar rings in the injection molding process for sensor applications and influences of the design of the gating system on the pole length accuracy. It is shown that the number of injection points and developing weld lines, as well as the positioning of the injection points, has a major influence on the magnetization characteristics of the molded rings. In general, a positioning of injection points and weld lines in the pole pitch and higher number of injection points lead to rings with a high reproduction accuracy of the pole length of the mold.

Highlights

Magnetic sensor system applications are further increasing, in particular in the automotive industry, and in mechanical engineering and consumer electronics [1]
Examples are sensors for the position of the headlight or torque and rotation angle sensors for electronic steering systems [1]. These magnetic sensor systems are always consisting of a magnetic sensitive electric component and a field generating magnet [1, 3]
The pole length is one important quality criterion of multipolar bonded magnetic rings used as encoder wheels

Summary

Introduction

Magnetic sensor system applications are further increasing, in particular in the automotive industry, and in mechanical engineering and consumer electronics [1]. Examples are sensors for the position of the headlight or torque and rotation angle sensors for electronic steering systems [1]. These magnetic sensor systems are always consisting of a magnetic sensitive electric component and a field generating magnet [1, 3]. Using rotating systems with a multipolar encoder wheel, the electric component senses the alternating magnetic field and, information about the rotational speed, angle, or turning position [2, 5, 6]. Specific requirements for the magnet have to be ensured, such as a steep slope of the flux density in the pole pitch, a small pole length [7], and precise pole length [7, 11]

Methods

Discussion

Conclusion