Magnetic metal sensor and method for detecting magnetic metal

• US 6,236,200 B1
• Filed: 05/19/1998
• Issued: 05/22/2001
• Est. Priority Date: 05/21/1997
• Status: Expired due to Term

• Current Assignee: MORI Seiki Company Limited (Dmg Mori Co., Ltd.)
• Original Assignee: Sony Precision Technology, Inc. (Sony Group Corp.)
• Inventors: Kusumi, Masaaki, Nekado, Yasuo
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): JOLLY, ANTHONY S
• Application Number:
  US09/080,957
• Time in Patent Office: 1,099 Days
• Field of Search: 324/207.26, 324/228, 324/243, 324/239, 324/260, 324/219, 324/220, 324/207.16, 324/207.12, 324/207.24, 324/207.25, 324/332, 324/236, 324/207.19, 324/207.2, 324/202, 324/174
• US Class Current: 324/207.26
• CPC Class Codes: G01V 3/105 forming directly coupled primary and secondary coils or loops
• CPC Class Codes: H03K 17/9505 Constructional details

Abstract

A magnetic metal sensor having a high response speed and which can detect small-sized metal pieces and can elongate the separation from the metal pieces. A magnetic metal sensor 2 has a core 22 defining a substantially U-shaped open magnetic path and coils 23, 24 of the same polarity mounted on the core 22. A uniform magnetic field along the direction of magnetic sensitivity is applied by a magnet 25 across the coils 24, 24. If magnetic metal approaches to a open magnetic path portion of the core 22 of the magnetic metal sensor 2, the magnetic reluctance of the magnetic circuit formed by the core and air is changed, as a result of which the impedance of the cores 23, 24 is changed. The magnetic metal sensor 2 detects the possible presence of magnetic metal or its displacement based on impedance changes of the paired coils 23, 24.

Claims

1. A magnetic metal sensor moved relative to a unit under detection comprised of a plurality of magnetic metal pieces arrayed side-by-side at a predetermined interval λ

along a direction of side-by-side arraying of said plurality of magnetic metal pieces for detecting said magnetic metal pieces, comprising;

a pair of magneto-electric conversion units each having a magnetically sensitive portion which responds to variations in a magnetic field along a direction of magnetic sensitivity; and

magnetic field generating means for applying the magnetic field along the direction of magnetic sensitivity to the magnetically sensitive portions of said pair of respective magneto-electric conversion units,

wherein the improvement resides in that

the magnetically sensitive portions in said pair of respective magneto-electric conversion units are of the same polarity, the direction of magnetic sensitivity is perpendicular to the direction of side-by-side arraying of said magnetic metal pieces, and a separation g′

between neighboring magnetic metal pieces along a movement direction is given by;

2. The magnetic metal sensor as claimed in claim 1 wherein the magnetically sensitive portions include respective coils energized by respective currents of a predetermined frequency for generating a second magnetic field along a second direction parallel to the direction of magnetic sensitivity.

3. The magnetic metal sensor as claimed in claim 1 wherein the magnetically sensitive portions include respective magnetic impedance effect devices fed with respective currents of a predetermined frequency along a second direction parallel to the direction of magnetic sensitivity.

4. A magnetic metal sensor comprising:

a pair of magneto-electric conversion units each having a magnetically sensitive portion which responds to variations in a magnetic field along a direction of magnetic sensitivity;

magnetic field generating means for applying the magnetic field along the direction of magnetic sensitivity to the magnetically sensitive portions of said pair of respective magneto-electric conversion units; and

switching means for switching a polarity in the direction of magnetic sensitivity of one of the magnetically sensitive portions of said pair of respective magneto-electric conversion units, wherein

when the magnetically sensitive portions of said pair of respective magneto-electric conversion units are of the same polarity, the magnetically sensitive portions move relative to portions under detection in a side-by-side arraying direction of the portions under detection for detecting the portions under detection, the portions under detection including a plurality of magnetic metal pieces arranged side-by-side at a predetermined interval λ

, the direction of magnetic sensitivity is perpendicular to the side-by-side arraying direction of the magnetic metal pieces, a separation g′

between neighboring magnetic metal pieces along a movement direction is

5. The magnetic metal sensor as claimed in claim 4 wherein the magnetically sensitive portions include respective coils energized by a current of a predetermined frequency for generating a second magnetic field along a second direction parallel to the direction of magnetic sensitivity.

6. The magnetic metal sensor as claimed in claim 4 wherein the magnetically sensitive portions include respective magnetic impedance effect devices fed with respective currents of a predetermined frequency along a second direction parallel to the direction of magnetic sensitivity.

7. A method for detecting a plurality of magnetic metal pieces arrayed side-by-side at a predetermined interval, comprising:

arraying a magnetic metal sensor including a pair of magneto-electric conversion units having respective magnetically sensitive devices responding to variations in a magnetic field along a direction of magnetic sensitivity and a magnetic field generator for applying a magnetic field along the direction of magnetic sensitivity to the magnetically sensitive devices of said pair of respective magnetic-electric conversions units, so that the direction of magnetic sensitivity of the magnetically sensitive devices is perpendicular to a side-by-side arraying direction of the magnetic metal pieces and the magnetically sensitive devices are of the same polarity, the magnetically sensitive devices being arrayed so that a separation g′

between neighboring magnetically sensitive devices will be given by