Sensing device for detecting change in an applied magnetic field achieving high accuracy by improved configuration

• US 6,169,396 B1
• Filed: 07/17/1997
• Issued: 01/02/2001
• Est. Priority Date: 02/19/1997
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yokotani, Masahiro, Shinjo, Izuru
• Primary Examiner(s): STRECKER, GERARD R
• Application Number:
  US08/896,166
• Time in Patent Office: 1,265 Days
• Field of Search: 324/173, 324/174, 324/207.12, 324/207.21, 324/207.25, 324/252, 338/32.R
• US Class Current: 324/207.21
• CPC Class Codes: G01D 5/147 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 Class Codes: G01R 33/09 Magnetoresistive devices

Abstract

A sensing device capable of obtaining an output signal corresponding precisely to a predetermined position (angle), for example, of a protruding or recessed portion of a moving magnetic-material member without being affected by temperature change. The sensing device includes: a magnet for generating a magnetic field; a rotary magnetic material member for changing the magnetic field generated by the magnet, the rotary member being disposed at a predetermined distance apart from the magnet; and a giant magnetoresistance element for detecting the change in the magnetic field induced by the rotary magnetic material member and generating a plurality of outputs having a peak value different from each other, the operating range of the giant magnetoresistance element being set such that a uniform change in resistance occurs over the operating range regardless of the direction of change in the magnetic field induced by the rotary magnetic material member, wherein the center of the giant magnetoresistance element is shifted from the center of the magnet in a direction parallel to a plane including the direction of the change in magnetic field induced by the rotary magnetic material member.

Claims

1. A sensing device comprising:

a single magnet for generating a magnetic field;

magnetic field variation inducing means for changing the magnetic field generated by said magnet, said magnetic field variation inducing means being disposed a predetermined distance apart from said magnet; and

a giant magnetoresistance disposed between said magnet and said magnetic field variation inducing means in the path of said generated magnetic field having a magnetic field sensing plane, said giant magnetoresistance detecting the change in the magnetic field induced by said magnetic field variation inducing means and generating a plurality of outputs having peak voltage values different from each other, said giant magnetoresistance including a plurality of magnetoresistance patterns formed on the magnetic field sensing plane, said plurality of magnetoresistance patterns being located at positions corresponding to said plurality of outputs having different peak voltage values, the magnetoresistance pattern for generating an output having the greatest peak voltage value of said plurality of magnetoresistance patterns being located at a position which results in the greatest change in resistance in relation to the positions of others of said plurality of magnetoresistance patterns, as a result of the change in magnetic field induced by said magnetic field variation inducing means.

2. A sensing device as claimed in claim 1, wherein:

a bridge circuit is constructed using said plurality of giant magnetoresistance patterns;

and wherein a magnetic field is applied to said plurality of giant magnetoresistance patterns in such a manner that the magnetic field applied to a giant magnetoresistance pattern located on one side of said bridge circuit is different in polarity from that applied to a giant magnetoresistance pattern located on another side of said bridge circuit.

3. A sensing device as claimed in claim 2, further comprising means for detecting a crossing point between the outputs of the giant magnetoresistance patterns located on the respective branches of said bridge circuit.

4. A sensing device as claimed in claim 3, wherein said means for detecting the crossing point comprises a differential amplifier having a plurality of amplifiers for amplifying the mid-point voltage of said bridge circuit, and a comparator for comparing the outputs of said plurality of amplifiers with each other.