Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1997-08-11
2001-07-03
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207110, C324S207120, C324S207200, C324S207210, C324S207250, C324S252000, C324S225000
Reexamination Certificate
active
06255811
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic detector using a resistor having hysteresis to detect rotation and movement of a magnetic body.
2. Description of the Related Art
FIG. 16
is a top view showing a magnetoresistive element formed on a silicon substrate to be used for a conventional magnetic detector.
FIG. 17
is an electric circuit diagram of the magnetoresistive element in FIG.
16
. As shown in
FIGS. 16 and 17
, a magnetoresistive element M is constituted so as to amplify and generate the voltage difference between middle points (nodes)
5
and
6
by bridge-connecting four same resistors
1
to
4
each other, connecting two faced vertexes to a power supply, Vb and an earth GND respectively, and connecting the middle point (node)
5
between resistors
1
and
4
and the middle point (node)
6
between resistors
2
and
3
to two input terminals of a differential amplifier
9
respectively through resistors
7
and
8
.
The resistance value of each of resistors
1
to
4
of a magnetoresistive element M symmetrically changes by using Y axis or X axis as a symmetry axis correspondingly to X-and Y-directional applied magnetic fields as shown in FIG.
18
and shows the same curve unless the magnetoresistive element M has hysteresis to a magnetic field change. However, in the case of a magnetoresistive element having hysteresis to a magnetic field change, the resistance value changes depending on the magnetic-field applied direction as shown in FIG.
19
.
The magnetic circuit of a conventional magnetic detector using the above magnetoresistive element generally comprises the magnetoresistive element M, magnetic object to be detected
10
, and magnet
11
as shown in FIG.
20
. In this case, it is assumed that a conventional magnetic detector detects the irregularity of a rotator serving as the magnetic object to be detected
10
. That is, the magnetic object to be detected
10
comprises a rotator having a concave
10
a
and a convex
10
b
at the outer periphery and the magnet
11
is set so as to face the concave
10
a
and convex
10
b
at the outer periphery of the rotator
10
. A magnetoresistive element M is set between the rotator
10
and the magnet
11
.
When the rotator
10
rotates, the magnetic flux density passing through the magnetoresistive element M changes nearby the boundary between the convex
10
a
and concave
10
b
, that is, the edge of the convex
10
a
if the convex
10
a
of the rotator
10
approaches the magnet
11
and the resistance values of the resistors
1
and
3
at the side A of the magnetoresistive element M increase and the resistance values of the resistors
2
and
4
at the side B of the magnetoresistive element M increase. Therefore, the differential output waveform of a magnetoresistive element M having no hysteresis becomes the waveform shown in FIG.
21
and waveforms corresponding to the concave
10
a
and convex
10
b
become same. Therefore, there is a problem that it is impossible to detect the concave and convex
10
a
and
10
b
of the rotator
10
.
Moreover, a magnetoresistive element M having hysteresis generates a signal corresponding to the size (distance) D of a gap between the rotator
10
and the magnetoresistive element M while the element M rotates in a constant direction. However, if the rotational direction of the rotator
10
is reversed, there is a problem that a signal level is inverted as shown in FIG.
22
.
Furthermore, in the case of the above conventional magnetic circuit, the resistance change value of a magnetoresistive element M decreases at a high temperature. Therefore, as shown in
FIG. 23
, there is a problem that a signal obtained through rotation of the rotator
10
serving as an object to be detected and the signal accuracy has temperature dependency.
Therefore, to solve the problems of the above conventional example, it is an object of the present invention to provide a magnetic detector capable of obtaining a signal corresponding to the size of the gap between a magnetic object to be detected and a resistor without depending on the moving direction or moving speed of a magnetic object to be detected.
It is another object of the present invention to provide a magnetic detector capable of decreasing the temperature dependency of an output signal (amplitude) of a magnetoresistive element.
SUMMARY OF THE INVENTION
A magnetic detector of the present invention comprises a magnet set nearby a rotatable magnetic object to be detected and a magnetoresistive element having hysteresis and set between the magnetic object to be detected and the magnet so as to tilt from the magnetizing direction of the magnet up to a predetermined angle.
According to the above structure, the magnetic detector can generate a signal corresponding to the distance between the magnetic object to be detected and the magnetoresistive element at a high accuracy independently of the moving direction or moving speed of the magnetic object to be detected.
According to one aspect of the present invention, the magnetic detector is provided with at least a pair of resistors having hysteresis and arranged separately from each other in the rotational direction of the magnetic object to be detected.
According to another aspect of the present invention, the magnet is set so that its magnetizing direction becomes parallel with a line passing through the rotational center of the magnetic object to be detected and the center of at least said two resistors and at least said two resistors are arranged so as to tilt from the line in the rotational direction of the magnetic object to be detected.
According to still another aspect of the present invention, the magnet is set so that its magnetizing direction tilts from the line passing through the rotational center of the magnetic object to be detected and the center of at least said two resistors in the rotational direction of the magnetic object to be detected and at least said two resistors are arranged perpendicularly to the line.
According to still another aspect of the present invention, the temperature dependency of the output amplitude of the magnetoresistive element is decreased by changing the tilt angle of the magnetoresistive element.
According to still another aspect of the present invention, the temperature dependency of the output amplitude of at least said two resistors is decreased by changing the interval between the resistors in the rotational direction of the magnetic object to be detected.
According to still another aspect of the present invention, the temperature dependency of the output amplitude of said two resistors by changing the tilt angle of the magnetoresistive element and moreover changing the interval between said two resistors in the rotational direction of the magnetic object to be detected.
According to a preferred aspect of the present invention, the tilt angle of the magnetoresistive element ranges between 10° and 40°.
According to another preferred aspect of the present invention, the tilt angle of the magnetoresistive element ranges between 20° and 25°.
REFERENCES:
patent: 4079360 (1978-03-01), Ookubo et al.
patent: 4725776 (1988-02-01), Onodera et al.
patent: 5477143 (1995-12-01), Wu
patent: 5801529 (1998-09-01), Umemoto et al.
patent: 6014023 (2000-01-01), Yokotani et al.
patent: 3426 784 (1986-01-01), None
patent: 195 07 304 (1995-09-01), None
patent: 195 80 095 (1996-02-01), None
patent: 60-155917 (1985-08-01), None
patent: 61-83910 (1986-04-01), None
Gonsalves et al., “Speed/position sensor based upon magnetoresistive effect”, European Patent application, pp. 1-10, Mar. 1991.
Fukui Wataru
Hatazawa Yasuyoshi
Shinjo Izuru
Mitsubishi Denki & Kabushiki Kaisha
Patidar Jay
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Magnetic detector with a magnetoresistive element having... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic detector with a magnetoresistive element having..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic detector with a magnetoresistive element having... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2479367