Electricity: measuring and testing – Magnetic – Magnetometers
Reexamination Certificate
1998-10-21
2001-03-20
Strecker, Gerard (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetometers
C324S207210, C324S174000, C257S427000, C338S03200R
Reexamination Certificate
active
06204662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic field sensing element for detecting a change in a magnetic field, and more particularly, to an element used in a device for detecting the number of rotations of, for example, a gear-like magnetic rotating body.
2. Description of the Related Art
FIG. 26
is a partial enlarged view of an essential portion of a conventional magnetic field sensing device.
FIGS. 27 and 28
are a sectional side elevation and a bottom view, respectively, showing the internal structure of the conventional magnetic field sensing device. It is to be noted that the bottom view of
FIG. 28
shows the magnetic field sensing device of
FIG. 27
with its case removed.
As shown in
FIG. 26
, the conventional magnetic field sensing device comprises a magnetic field sensing device body
1
and a connector
2
connected with the magnetic field sensing device body
1
.
As shown in
FIG. 27
, the magnetic field sensing device body
1
comprises a cylindrical case
3
made of synthetic resin, an electric circuit body
4
housed in the case
3
, a rectangular-parallelopiped-shaped permanent magnet
5
provided at an end portion of the electric circuit body
4
(on the right side in FIG.
27
), and a magnetic field sensing element
6
provided on the front surface of the permanent magnet
5
with a built-in giant magnetic resistance element (hereinafter referred to as a GMR element).
Further, as shown in
FIG. 28
, the electric circuit body
4
comprises a substrate
7
made of synthetic resin, resistors
8
and capacitors
9
provided on the substrate
7
, and wiring
10
for electrically connecting the resistors
8
, the capacitors
9
, and the magnetic field sensing element
6
.
In the above-mentioned magnetic field sensing device, rotation of the gear-like magnetic rotating body
11
provided in proximity to the magnetic field sensing element makes concavities
11
a
and convexities
11
b
of the magnetic rotating body
11
alternately approach the magnetic field sensing element
6
, and thus, cause a change in the magnetic field of the permanent magnet
5
applied to the magnetic field sensing element
6
.
This change in the magnetic field is detected as a change in voltage by the GMR element (not shown) inside the magnetic field sensing element
6
. The change in voltage thus generated in the GMR element is output via a differential amplification circuit and a comparison circuit both in the magnetic field sensing element
6
, to the outside as a pulse wave electric signal. This electric signal is transmitted via a terminal of the connector
2
to a computer unit (not shown) which calculates the rotation angle of the magnetic rotating body
11
. It is to be noted that the resistors
8
and the capacitors
9
form a filter circuit which prevents external noise, including external surges, from penetrating to the magnetic field sensing element
6
.
In the conventional magnetic field sensing element, since a lot of time is required to solder the resistors
8
and the capacitors
9
to the substrate
7
, there is a problem in that the production efficiency of the magnetic field sensing device is low and the manufacturing cost is high.
Further, since space is required for assembling the resistors
8
and the capacitors
9
on the substrate
7
, there is a problem in that the size of the magnetic field sensing element and the magnetic field sensing device as a whole accordingly become larger.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above mentioned problems, and an object of the present invention is to provide a miniaturized magnetic field sensing element and a magnetic field sensing device with improved production efficiency and a lower manufacturing cost.
According to one aspect of the invention there is provided a magnetic field sensing element comprising: a giant magnetic resistance element formed on a substrate for detecting a change in a magnetic field; an integrated circuit formed on the substrate for carrying out predetermined arithmetic processing based on a change in the magnetic field detected by the giant magnetic resistance element; and an input side protective resistor and an output side protective resistor provided on the input side and the output side, respectively, of the integrated circuit, wherein the metal film from which the input side resistor and the output side resistor are formed is identical to the metal film from which the integrated circuit is formed.
According to another aspect of the invention, there is provided a magnetic field sensing element comprising: an integrated circuit formed on a substrate for carrying out predetermined arithmetic processing based on a change in a magnetic field detected by a giant magnetic resistance element; a level difference buffer layer formed on the integrated circuit and having a smooth surface; an input side protective resistor and an output side protective resistor provided on the level difference buffer layer together with the giant magnetic resistance element and connected to the input side and the output side, respectively, of the integrated circuit; and wiring for connecting the input side protective resistor with the integrated circuit and for connecting the output side protective resistor with the integrated circuit, wherein the metal film from which the input side resistor and the output side resistor are formed is identical to the metal film from which the wiring is formed.
In a preferred form of the invention, the metal film has a specific resistance of 2×10
−6
&OHgr;·cm or more.
In accordance with another aspect of the present invention, the metal film is mainly formed of aluminum.
In accordance with a further aspect of the invention, the input side resistor and the output side resistor formed of the metal film are 10 to 20 &mgr;m in width.
In a preferred form of the present invention, the input side resistor and the output side resistor formed of the metal film are 1 to 2 &mgr;m in thickness.
In a further preferred form of the present invention, the input side resistor and the output side resistor are formed on the substrate.
According to further aspect of the invention, there is provided a magnetic field sensing device comprising: a magnetic rotating body having convexities and concavities along its outer periphery for rotating about an axis of rotation; a magnet arranged so as to face the outer periphery of the magnetic rotating body; and a magnetic field sensing element to a surface of the magnet facing the outer periphery of the magnetic rotating body, wherein the magnetic element detects a change in a magnetic field between the magnetic rotating body and the magnet upon rotation of the magnetic rotating body, and, based on the result of the detection, calculates the amount of rotation of the magnetic rotating body.
REFERENCES:
patent: 4687994 (1987-08-01), Fulkerson et al.
patent: 5084674 (1992-01-01), Lachmann et al.
patent: 6072311 (2000-06-01), Shinjo et al.
patent: 195 23 322 (1997-01-01), None
patent: 196 49 400 (1997-12-01), None
patent: 197 44 090 (1998-10-01), None
patent: 3-48715 (1991-05-01), None
patent: 7-198736 (1995-08-01), None
Hatazawa Yasuyoshi
Nada Takuji
Shinjo Izuru
Yokotani Masahiro
Mitsubishi Denki & Kabushiki Kaisha
Strecker Gerard
Sughrue Mion Zinn Macpeak & Seas, PLLC
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