Magnetic rotation-angle detector

Patent metadata

Field	Value
Publication number	US-9702735-B2
Application number	US-201314378559-A
Country	US
Kind code	B2
Filing date	May 21, 2013
Priority date	May 22, 2012
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

Provided is a magnetic rotation-angle detector that includes a disk-shaped magnet that is magnetized so as to change magnetic poles n times per rotation (where n is an integer equal to or larger than 1); a magnetic-body slit plate that is rotated together with the magnet, where a part having a high magnetic flux permeability and a part having a low magnetic flux permeability are alternately and repeatedly arranged thereon so as to change the magnetic flux permeability m times per rotation (where m is an integer equal to or larger than 2 and m>n); a magnetic sensor that detects magnetism from the magnet when the magnet has passed by through the magnetic-body slit plate; and a calculation unit that obtains the rotation angle of the magnet from the output from the magnetic sensor.

First claim

The invention claimed is:

1. A magnetic rotation-angle detector comprising:
a magnetic sensor in which magnetic detection elements are arranged with a space of π/n [rad], where n is an integer equal to or larger than 1; or π/m [rad], where m is an integer equal to or larger than 2, and m>n therebetween and that separates and takes a signal of a rotation period of m or a rotation period of n from a magnetic field change in which the rotation period of m and the rotation period of n are superimposed;
a rotating disk-shaped magnet that is magnetized so as to present, to the magnetic sensor, a complete 360 degree cycle of magnetic polarity change n times per rotation;
a unit, comprising a magnetic-body slit plate that is rotated together with the magnet, that generates a magnetic filed change in which a rotation period of m and a rotation period of n are superimposed per rotation of the unit, the magnetic-body slit plate that is rotated together with the magnetic-body slit plate being provided with a part having a high magnetic flux permeability and a part having a low magnetic flux permeability that are alternately and repeatedly arranged thereon, so as to cycle a magnetic flux permeability m times per rotation; and
a calculator unit that separates a signal component having a frequency of n and a signal component having a frequency of m from an output from the magnetic sensor and obtains a rotation angle of the magnet.

2. The magnetic rotation-angle detector according to claim 1 , wherein
a non-magnetic body spacer is provided between the magnet and the magnetic-body slit plate, and
a fixed space is provided between the magnet and the magnetic-body slit plate.

3. The magnetic rotation-angle detector according to claim 1 ,
further comprising a disk-shaped second magnet that is provided on an inner side of the magnet and that is magnetized so as to present, to the magnetic sensor, a complete 360 degree cycle of magnetic polarity k times per rotation, where k is an integer equal to or larger than 1, and k<n.

4. The magnetic rotation-angle detector according to claim 1 , wherein
the magnetic-body slit plate is formed by printing a magnetic ink on a surface of the magnet.

Assignees

• Mitsubishi Electric Corp

Inventors

• Musha Takeshi
• Inoue Jin
• Nakajima Hajime
• Okamuro Takashi

Classifications

• G01D5/245 Primary

  using a variable number of pulses in a train · CPC title

• G01D5/165 Primary

  by relative movement of a point of contact {or actuation} and a resistive track · CPC title

• G01B7/30

  for measuring angles or tapers; for testing the alignment of axes · CPC title

• G01D5/147

  influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other · CPC title

• G01D5/00

  Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable (G01D3/00 takes precedence; specially adapted for apparatus giving results other than momentary value of variable G01D1/00) · CPC title