Rotation sensor

Details Rotation sensor Rotation sensor

1999-10-22

2001-11-27

Patidar, Jay (Department: 2862)

Electricity: measuring and testing

Magnetic

Displacement

C324S252000, C324S207250

Reexamination Certificate

active

06323644

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistance element for detecting a variation of magnetic field and particularly relates to a magnetic detection element which is provided with a giant magnetoresistance element with high level output, method of production of it and magnetic detection device.
2. Description of the Prior Art
Generally speaking, a magnetoresistance element (hereinafter relate to MR element) is an element whose resistance value changes depending on an angle between a magnetization direction of a thin film consisting of a ferromagnetic substance (e.g. Ni—Fe, Ni—Co, etc.) and a direction of electric current.
Resistance of the MR element as above takes a minimum value when an electric current direction and magnetization direction intersects at right angle and takes a maximum value when angle between electric current direction and magnetization direction becomes zero: i.e., both of directions are the same or reversed each other completely. Such a change of resistance value is referred to MR change rate and generally Ni—Fe and Ni—Co takes a rate of 2~3% and 5~6% respectively.
FIG.
9
and
FIG. 10
are a side view and a perspective view respectively showing a structure of a conventional magnetic detection device.
As shown by
FIG. 9
, a conventional magnetic detection device is provided with a rotation shaft
41
, a disk shaped magnetic rotating body having at least one or more of uneven face of recess and protrusion on its periphery and rotating synchronously with a rotation of the rotation shaft
41
, a MR element
43
which is arranged with a gap having a predetermined distance with the periphery of the rotating body, a magnet
44
fixed to the back side of the MR element
43
for supplying a magnetic field to the MR element
43
and an integrated circuit
45
for processing an output of the MR element
43
; and the MR element
43
consists of a magnetic resistance pattern
46
and a thin film surface
47
(magnetosensitive surface).
In the foregoing magnetic detection device, the magnetic field penetrating through to thin film surface
47
, i.e. a magnetosensitive surface of the MR element
43
changes due to the rotation of the magnetic body
42
, thereby the resistance value of the magnetic pattern
46
changes.
However, the output level of the MR element
43
used for the magnetic detection device as above is low and therefor a detection with high accuracy can not be performed. In order to overcome this problem, recently a magnetic detection element employing a giant magnetoresistance element (hereinafter refer to as GMR element) with a high level output has been proposed.
FIG. 11
shows characteristics of a conventional GMR element.
The GMR element exhibiting the characteristics shown by
FIG. 11
is a laminated layers member acting as so called an artificial lattice membrane arranged in lamination of an alternate succession of a magnetic layer having a thickness of several Å to several tens Å and a non magnetic layer (Fe/Cr, and permalloy/Cu/Co/Cu, Co/Cu, FeCo/Cu) which is disclosed by an article bearing a title of “magnetoresistance effect of an artificial lattice” appearing in Journal of Japanese Applied Magnetism, Vol.15, No,51991, pp.813~821. This laminated member has an extraordinarily high MR effect (MR change rate) comparing with the MR element as mentioned above and also is possible to obtain the same change of resistance regardless of direction of external magnetic field with respect to electric current.
In order to detect a change of magnetic field, carrying out formation of a substantial magnetosensitive surface using a GMR element, formation of electrode on each end of the magnetosensitive surface and forming a bridge circuit between these ends, connecting a power supply for a constant voltage and a constant current between two electrodes facing each other, and converting change of resistance value of the GMR element to change of voltage and then it is possible to arrange the detection of change of magnetic field being acted on the GMR element.
FIG.
12
and
FIG. 13
are a side view and a perspective view, respectively, of a structure of a magnetic detection device using a conventional GMR element.
FIG.
12
and
FIG. 13
, this magnetic detection device comprises a rotation shaft
41
, a disk shaped magnetic rotating body as a means of providing a magnetic field change due to a rotating magnetic field synchronously with the rotation of the rotating shaft
41
and having at least one uneven surface of recess and protrusion on that rotating body, a GMR element
48
which is arranged with a gap of predetermined spacing facing the outer periphery of the magnetic rotating body
42
, a magnet
44
as a means for providing a magnetic field to the GMR element
48
and an integrated circuit
45
for processing output of the GMR element
48
; and the GMR element
48
has a magnetic resistance pattern
49
as a magnetosensitive pattern and a thin film surface
50
.
In the magnetic detection device as above, a magnetic field penetrating through the thin film surface (magnetosensitive surface)
50
of the GMR element
48
changes due to rotation of the magnetic rotating body
42
, thereby resistance value of the magnetoresistance pattern
49
changes.
FIG. 14
is a black diagram of a magnetic detection device employing a conventional GMR element, and
FIG. 15
is a detailed block diagram of a magnetic detection device employing a conventional GMR element.
A magnetic detection device shown by FIG.
14
and
FIG. 15
comprises a Wheatstone bridge circuit using a GMR element
48
which is arranged with a gap having a predetermined distance with a magnetic rotating body
42
and is supplied with a magnetic field from the magnet
44
, a differential amplifier circuit
52
for amplifying an output of the Wheatstone bridge circuit
51
, a comparator circuit
53
for outputting “0” or “1” signal by comparing this output value of the differential amplifying circuit
52
with a reference value and an output circuit
54
for performing switching upon reception of the output of the comparator circuit
53
.
FIG. 16
shows an example of a circuit arrangement of a magnetic detection device using a conventional GMR element.
FIG. 16
, a Wheatstone bridge circuit
51
has, for example, the GMR element
48
a
,
48
b
,
48
c
, and
48
d
on each side of it; and the GMR element
48
a
and GMR element
48
c
are connected to the power supply terminal VCC, the GMR element
48
b
and the GMR element
48
d
are grounded, each of the other end of the GMR element
48
a
and that of the GMR element
48
b
is connected to a connection point
55
and each of the other and of the GMR element
48
c
and the GMR element
48
d
is connected to a connection point
56
.
The connection point
55
of the Wheatstone bridge circuit
51
is connected to an inverse input terminal of the amplifier
59
of the differential amplifier circuit
58
through a resistor
57
, and the connection point
56
is connected to a non-inverse input terminal of the amplifier
59
through a resistor
60
and further connected to a potential dividing circuit
62
which provides a reference voltage on the basis of the voltage supplied from the power supply terminal VCC.
An output terminal of the amplifier
59
is connected to it's own inverse terminal through a resistor
63
and also is connected to an inverse input terminal of the amplifier
65
of the comparator circuit
64
; and a non-inverse input terminal of the amplifier
65
is connected to a potential dividing circuit
66
which provides a reference voltage on the basis of the voltage supplied from the power supply terminal VCC and also is connected to an output terminal of an amplifier
65
through an resister
67
.
An output end of the comparator circuit
64
is connected to base of a transistor
69
of the output circuit
68
, collector of the transistor
69
is connected to an output terminal
70
of the output circuit
68
and is connected also to the power supply terminal VCC thr

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