Title: Electronic instrument having a magnetic sensor
Abstract: A magnetic sensor of an electronic instrument has a circular or substantially circular component that assumes magnetism in the vicinity of its circumference. An X axis magnetic sensor detects a magnetic field component in the X axis direction that is arranged in a position inside the vicinity of the circumference of the component, or is arranged such that a detection axis of the magnetic sensor overlaps an X axis passing through the center of the component in an arbitrary position on the X axis or on its extended line. A Y axis magnetic sensor detects a magnetic component in a Y axis direction that is arranged inside the vicinity of the circumference of the component, or is arranged such that a detection axis of the magnetic sensor overlaps a Y axis passing through the center of the component and perpendicular to the X axis in an arbitrary position on the Y axis or on its extended line. A correcting circuit corrects the signals outputted from the X axis magnetic sensor and the Y axis magnetic sensor.
Patent Number: 6,860,022 Issued on 03/01/2005 to Kato, et al.
| Inventors:
|
Kato; Kazuo (Chiba, JP);
Nirasawa; Shoji (Chiba, JP)
|
| Assignee:
|
Seiko Instruments Inc. (Chiba, JP)
|
| Appl. No.:
|
655848 |
| Filed:
|
September 5, 2003 |
Foreign Application Priority Data
| Feb 16, 2000[JP] | 2000-038438 |
| Current U.S. Class: |
33/356; 33/DIG.1; 324/247 |
| Intern'l Class: |
G01C 017//38 |
| Field of Search: |
33/356,357,358,355 R,DIG. 1,366.11
324/225,252,247
368/10
|
References Cited [Referenced By]
U.S. Patent Documents
| 4179741 | Dec., 1979 | Rossani | 701/224.
|
| 4482255 | Nov., 1984 | Gygax et al. | 368/10.
|
| 4668100 | May., 1987 | Murakami et al. | 368/10.
|
| 4686772 | Aug., 1987 | Sobel | 33/333.
|
| 5187872 | Feb., 1993 | Dufour | 33/356.
|
| 5481506 | Jan., 1996 | Kita | 368/10.
|
| 5511319 | Apr., 1996 | Geerlings et al. | 33/356.
|
| 5521501 | May., 1996 | Dettmann et al. | 324/252.
|
| 5596551 | Jan., 1997 | Born et al. | 368/10.
|
| 5850624 | Dec., 1998 | Gard et al. | 702/92.
|
| 5883861 | Mar., 1999 | Moser et al. | 368/10.
|
| 6286221 | Sep., 2001 | Voto et al. | 33/356.
|
| 6385133 | May., 2002 | Miyauchi | 368/10.
|
| 6543146 | Apr., 2003 | Smith et al. | 33/356.
|
| 6606799 | Aug., 2003 | Kato | 33/356.
|
| 6640454 | Nov., 2003 | Kato et al. | 33/356.
|
| 2002/0023362 | Feb., 2002 | Kato | 33/356.
|
| Foreign Patent Documents |
| 1024345 | Aug., 2000 | EP.
| |
| 03071011 | Mar., 1991 | JP.
| |
| 06300869 | Oct., 1994 | JP.
| |
| 10170663 | Jun., 1998 | JP.
| |
| WO 99067596 | Dec., 1999 | WO.
| |
Other References
Patent Abstracts of Japan, vol. 1998, No. 11, Sep. 30, 1998 EPO publication
No. 10170663 dated Jun. 26, 1998.*
Patent Abstracts of Japan, vol. 1995, No. 01, Feb. 28, 1995 EPO publication
No. 06300869 dated Oct. 28, 1994.*
Patent Abstracts of Japan, vol. 015, No. 230, Jun. 12, 1991 EPO publication
No. 03071011 dated Mar. 26, 1991.
|
Primary Examiner: Gutierrez; Diego
Assistant Examiner: Smith; R. Alexander
Attorney, Agent or Firm: Adams & Wilks
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is based on divisional U.S. application Ser. No.
09/778,461, filed on Feb. 7, 2001, now U.S. Pat. No. 6,640,454, which is
hereby incorporated by reference, and priority thereto for common subject
matter is hereby claimed.
Claims
What is claimed is:
1. An electronic instrument having a magnetic sensor comprising:
a circular or substantially circular component that is susceptible to
magnetization;
a magnetic sensor to output a signal corresponding to a direction of a
magnetic field that is arranged in an arbitrary position on a straight
line passing the center of said component such that said straight line and
a detection axis of magnetism coincide; and
a correcting circuit to correct the signal outputted from said magnetic
sensor in accordance with the relative position between said component and
said magnetic sensor.
2. An electronic instrument having a magnetic sensor according to claim 1,
wherein said component that is susceptible to magnetization is a battery
made of stainless steel.
3. An electronic instrument having a magnetic sensor according to claim 1,
wherein said electronic instrument is an electronic azimuth indicator, a
wristwatch with an electronic azimuth indicator, a pressure gauge with an
electronic azimuth indicator, a car navigation terminal apparatus, a
portable electronic instrument with an electronic azimuth indicator, or an
electronic instrument with an electronic azimuth indicator.
4. An electronic instrument having a magnetic sensor comprising:
a circular or substantially circular component that is susceptible to
magnetization;
an X axis magnetic sensor to detect a magnetic field component in an X axis
direction that is arranged in an arbitrary position in a distance within
the area of approximately 2.sup.-1/2 of the radius from the center of said
component, or is arranged such that a detection axis of said magnetic
sensor overlaps an X axis passing through the center of said component in
an arbitrary position on said X axis or on its extended line;
a Y axis magnetic sensor to detect a magnetic field component in a Y axis
direction that is arranged in an arbitrary position in a distance within
the area of approximately 2.sup.-1/2 of the radius from the center of said
component, or is arranged such that a detection axis of the magnetic
sensor overlaps an Y axis passing through said component and perpendicular
to said X axis in an arbitrary position on said Y axis or on its extended
line; and
a correcting circuit to correct the signals outputted from said X axis
magnetic sensor and said Y axis magnetic sensor in accordance with the
relative position between said component and said X and Y magnetic
sensors.
5. An electronic instrument having a magnetic sensor according to claim 4,
wherein said component that is susceptible to magnetization is a battery
made of stainless steel.
6. An electronic instrument having a magnetic sensor according to claim 4,
wherein said magnetic sensor, said Y axis magnetic sensor or said X axis
magnetic sensor consists of a two axis magnetic sensor that is capable of
measuring both the magnetic field components in said X axis direction and
in said Y axis direction perpendicular to said X axis.
7. An electronic instrument having a magnetic sensor according to claim 4,
wherein said electronic instrument is an electronic azimuth indicator, a
wristwatch with an electronic azimuth indicator, a pressure gauge with an
electronic azimuth indicator, a car navigation terminal apparatus, a
portable electronic instrument with an electronic azimuth indicator, or an
electronic instrument with an electronic azimuth indicator.
8. An electronic instrument having a magnetic sensor comprising:
a circular or substantially circular component assuming magnetism in the
vicinity of its circumference by processing;
a magnetic sensor to output a signal corresponding to a direction of a
magnetic field that is arranged in an arbitrary position on a straight
line passing the center of said component such that said straight line and
a detection axis of magnetism coincide; and
a correcting circuit to correct the signal outputted from said magnetic
sensor depending on the relative position between said component and said
magnetic sensor.
9. An electronic instrument having a magnetic sensor according to claim 8,
wherein said circular or substantially circular component is a battery
made of stainless steel.
10. An electronic instrument having a magnetic sensor according to claim 8,
wherein said electronic instrument is an electronic azimuth indicator, a
wristwatch with an electronic azimuth indicator, a pressure gauge with an
electronic azimuth indicator, a car navigation terminal apparatus, a
portable electronic instrument with an electronic azimuth indicator, or an
electronic instrument with an electronic azimuth indicator.
11. An electronic instrument having a magnetic sensor comprising:
a circular or substantially circular component assuming magnetism in the
vicinity of its circumference by processing;
an X axis magnetic sensor for detecting a magnetic field component in the X
axis direction that is arranged in a position inside said vicinity of the
circumference assuming magnetism of said circular or substantially
circular component, or is arranged such that a detection axis of said
magnetic sensor overlaps an X axis passing through the center of said
component in an arbitrary position on the X axis or on its extended line;
a Y axis magnetic sensor for detecting a magnetic component in a Y axis
direction that is arranged inside said vicinity of the circumference
assuming magnetism of said circular or substantially circular component,
or is arranged such that a detection axis of said magnetic sensor overlaps
a Y axis passing through the center of said component and perpendicular to
said X axis in an arbitrary position on the Y axis or on its extended
line; and
a correcting circuit to correct the signals outputted from said X axis
magnetic sensor and said Y axis magnetic sensor.
12. An electronic instrument having a magnetic sensor according to claim
11, wherein said circular or substantially circular component is a battery
made of stainless steel.
13. An electronic instrument having a magnetic sensor according to claim
11, wherein said magnetic sensor, said Y axis magnetic sensor or said X
axis magnetic sensor consists of a two axis magnetic sensor that is
capable of measuring both the magnetic field components in said X axis
direction and in said Y axis direction perpendicular to said X axis.
14. An electronic instrument having a magnetic sensor according to claim
11, wherein said electronic instrument is an electronic azimuth indicator,
a wristwatch with an electronic azimuth indicator, a pressure gauge with
an electronic azimuth indicator, a car navigation terminal apparatus, a
portable electronic instrument with an electronic azimuth indicator, or an
electronic instrument with an electronic azimuth indicator.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic instrument having a magnetic
sensor, particularly to an electronic azimuth indicator including a part
having magnetic susceptibility that affects a magnetic sensor, or to a
various kinds of electronic instruments provided with such an electronic
azimuth indicator.
2. Description of the Prior Art
As an example of such an electronic instrument that has been conventionally
used, there is a wristwatch provided with an electronic azimuth indicator.
Such a wristwatch with an electronic azimuth indicator has a problem that,
when a magnetic sensor is arranged in the vicinity of a part that is
susceptible to magnetization or a part assuming magnetism, accurate
detection of a direction is difficult because such a part adversely affect
the magnetic sensor.
To describe it more concretely, geomagnetism can be generally regarded as
an even magnetic field. When a spherical magnetic body is arranged in such
an even magnetic field, the magnetic field is distorted as shown in FIG.
14. FIG. 14 shows a state of the magnetic field in which a spherical
magnetic body is arranged in an even magnetic field. As can be seen from
the figure, the direction of the magnetic field is deflected to the
direction of a spherical magnetic body 19 as shown by a magnetic field 9a
in the vicinity of the spherical magnetic body 19. Such a phenomenon is
observed when an article assuming magnetism (a magnetic body) is placed
within the magnetic field.
In addition, an electronic instrument such as a wristwatch with an
electronic azimuth indicator uses a magnetic body such as a battery and a
capacitor, and particularly there are a lot of button batteries that use
304 stainless steel processed to have a circular shape. Although it is
generally considered that such 304 stainless steel does not have
magnetism, when the stainless steel elongates due to die cutting or
bending, magnetism may occur in the direction of the elongation.
For example, as shown in FIG. 15, if the entire outer configuration of the
circular stainless steel is processed to elongate in the circumference
direction, the elongation occurs from the inside to the outside with
respect to the outer configuration as shown by arrows. Magnetism is
observed with the direction of the elongation as an axis.
Therefore, when it is necessary to arrange a magnetic sensor in the
vicinity of a magnetic body or a button battery, there is a possibility
that detection of magnetic field components is adversely affected due to
the above -mentioned effects.
As prior art for solving this problem, there is the invention described in
the Japanese Patent Application Laid-open No. Hei 6-309869. In this prior
art, a distance between various kinds of electronic parts and a magnetic
sensor that is sufficient to eliminate influence of the electronic parts
is studied in detail, and the position of the magnetic sensor is
determined based on the study. That is, the magnetic sensor is arranged as
far as possible from an electronic part that is susceptible to
magnetization to make the influence of the electronic part to the magnetic
sensor minimum.
PROBLEMS TO BE SOLVED BY THE INVENTION
However, the invention described in the Japanese Patent Application
Laid-open No. Hei 6-300869 has a problem that, since a magnetic sensor is
arranged apart from an electronic part that is susceptible to
magnetization, the configuration of the magnetic sensor is considerably
limited regarding a place where it is arranged, which is a substantial
restriction in designing the product. Particularly, since there is a
strong need for miniaturization of a portable electronic apparatus, this
restriction in arrangement is a large problem from the viewpoint of
securing freedom of designing including planning. Such a restriction in
arrangement not only poses a problem of not being capable of adopting a
novel form conforming to a fashion as an outward design (form), but also
is a problem in an aspect of functionality.
That is, a size and form are a part of important functions in itself in a
portable electronic instrument. For example, in the case of a portable
electronic instrument, particularly a wristwatch, or a barometer, a
pressure gauge and the like that are used in skydiving, skin diving or the
like, a shape with a part carelessly protruding from the outer
configuration or a too large shape is not only inconvenient for handling,
but also is an obstacle in an emergency operation, which even has a
possibility of resulting in an unexpected accident.
Further, since it is necessary to secure a distance between a part that is
susceptible to magnetization and a magnetic sensor, a frame and a
substrate that support the part and the sensor inevitably take a large
shape. Thus, there is a problem that materials used in the frame, the
substrate and the like increase in volume, which not only increases
manufacturing costs but also increases packaging costs and transportation
costs.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an
electronic instrument that uses a magnetic sensor and a circular or
substantially circular component assuming magnetism, wherein it is not
necessary to arrange the magnetic sensor spaced apart from the component.
It is another object of the present invention to provide an electronic
instrument that uses a circular or substantially circular component
assuming magnetism in the vicinity of the circumference thereof and a
magnetic sensor during processing steps of making materials and parts
circular or substantially circular shape, wherein it is not necessary to
arrange the magnetic sensor spaced apart from the component.
In order to attain the above-mentioned objects, a first aspect of the
present invention is an electronic instrument characterized by comprising:
a circular or substantially circular component that is susceptible to
magnetization; a magnetic sensor to output a signal corresponding to a
direction of a magnetic field that is arranged in an arbitrary position in
a distance within the area of approximately 2.sup.-1/2 of the radius from
the center of the circular or substantially circular component; and
correcting circuit to correct the signal outputted from the magnetic
sensor in accordance with the relative position between the component and
the magnetic sensor.
With this configuration, even if the magnetic sensor is located in the
upper or lower side of the circular or substantially circular component
that is susceptible to magnetization, since the magnetic sensor can be
arranged in an arbitrary position as long as it is within a predetermined
distance from the center of the component, freedom of selecting a place
where the magnetic sensor is arranged is expanded in designing the
electronic instrument, and miniaturization and the like of an electronic
instrument can be attained while maintaining high precision.
An electronic instrument in accordance with a second aspect of the present
invention is an electronic instrument having a magnetic sensor,
characterized by comprising: a circular or substantially circular
component that is susceptible to magnetization; a magnetic sensor to
output a signal corresponding to a direction of a magnetic field that is
arranged in an arbitrary position on a straight line passing the center of
the component such that the straight line and a detection axis of the
magnetism coincide; and correcting circuit to correct the signal outputted
from the magnetic sensor in accordance with the relative position between
the component and the magnetic sensor.
With this configuration, even if the magnetic sensor cannot be arranged in
an arbitrary position within a predetermined distance from the center of
the circular or substantially circular component that is susceptible to
magnetization, since it is possible to arrange the magnetic sensor in an
arbitrary position on a straight line passing the center of the component
such that the straight line and a detection axis of the magnetism
coincide, freedom of selecting a place where the magnetic sensor is
arranged is expanded in designing the electronic instrument, and
miniaturization and the like of an electronic instrument can be attained
while maintaining high precision.
An electronic instrument in accordance with the third aspect of the present
invention is an electronic instrument having a magnetic sensor,
characterized by comprising: a circular or substantially circular
component that is susceptible to magnetization; an X axis magnetic sensor
for detecting a magnetic field component in an X axis direction that is
arranged in an arbitrary position in a distance within the area of
approximately 2.sup.-1/2 of the radius from the center of the component,
or is arranged such that a detection axis of the magnetic sensor overlaps
an X axis passing through the center of the component in an arbitrary
position on the X axis or on its extended line; a Y axis magnetic sensor
for detecting a magnetic field component in a Y axis direction that is
arranged in an arbitrary position in a distance within the area of
approximately 2.sup.-1/2 of the radius from the center of the component,
or is arranged such that a detection axis of the magnetic sensor overlaps
a Y axis passing through the center of the component and perpendicular to
the X axis in an arbitrary position on the Y axis or on its extended line;
and correcting circuit to correct the signals outputted from the X axis
magnetic sensor and the Y axis magnetic sensor in accordance with the
relative position between the component and the X and Y magnetic axes.
With this configuration, since each of the X axis magnetic sensor and the Y
axis magnetic sensor can be arranged in an arbitrary position within a
predetermined distance from the center of the circular or substantially
circular component, or in an arbitrary position on a straight line passing
the center of the component where the arbitrary line and a detection axis
of the magnetism coincide, freedom of designing can be further increased,
and miniaturization and the like of an electronic instrument can be
attained while maintaining high precision.
An electronic instrument in accordance with a fourth aspect of the present
invention is an electronic instrument having a magnetic sensor
characterized in that the component that is susceptible to magnetization
is a battery made of 304 stainless steel. Recently, there are many
electronic parts such as a button battery that have the size of the
above-mentioned battery, which in conjunction with this configuration,
makes it possible to make an electronic instrument using such a battery
higher in performance, miniaturized, and so forth.
An electronic instrument in accordance with a fifth aspect of the present
invention is an electronic instrument having a magnetic sensor,
characterized by comprising: a circular or substantially circular
component assuming magnetism in the vicinity of its circumference by
processing; a magnetic sensor to output a signal corresponding to a
direction of a magnetic field that is arranged in a position inside the
vicinity of the circumference assuming magnetism of the circular or
substantially circular component; and correcting circuit to correct the
signal outputted by the magnetic sensor in accordance with the relative
position between the component and the magnetic sensor.
With this configuration, even if the magnetic sensor is arranged in the
upper and the lower side of the circular or substantially circular
component assuming magnetism in the vicinity of its circumference by
processing, since the magnetic sensor can be arranged in an arbitrary
position as long as it is within a predetermined distance from the center
of the component, freedom of selecting a place where the magnetic sensor
is arranged is expanded in designing the electronic instrument, and
miniaturization and the like of an electronic instrument can be attained
while maintaining high precision.
An electronic instrument in accordance with a sixth aspect of the present
invention is an electronic instrument having a magnetic sensor,
characterized by comprising: a circular or substantially circular
component assuming magnetism in the vicinity of its circumference by
processing; a magnetic sensor to output a signal corresponding to a
direction of a magnetic field that is arranged in an arbitrary position on
a straight line passing the center of the component such that the straight
line and a detection axis of magnetism coincide; and correcting circuit to
correct the signal outputted from the magnetic sensor depending on the
relative position between the component and the magnetic sensor.
With this configuration, even if the magnetic sensor cannot be arranged in
an arbitrary position within a predetermined distance from the center of
the circular or substantially circular component assuming magnetism in the
vicinity of its circumference by processing, since the magnetic sensor can
be arranged in an arbitrary position on an arbitrary straight line passing
through the center of the component such that the straight line and an
detection axis of magnetism coincide, freedom of selecting a place where
the magnetic sensor is arranged is expanded in designing the electronic
instrument, and miniaturization and the like of an electronic instrument
can be attained while maintaining high precision.
An electronic instrument in accordance with a seventh aspect of the present
invention is an electronic instrument having a magnetic sensor,
characterized by comprising: a circular or substantially circular
component assuming magnetism in the vicinity of its circumference by
processing; an X axis magnetic sensor for detecting a magnetic field
component in an X axis direction that is arranged in a position inside the
vicinity of the circumference assuming magnetism of the circular or
substantially circular component, or is positioned such that a detection
axis of the magnetic sensor overlaps an X axis passing the center of the
component in an arbitrary position on the X axis or on its extended line;
a Y axis magnetic sensor for detecting a magnetic component in a Y axis
direction that is arranged inside the vicinity of the circumference
assuming magnetism of the circular or substantially circular component, or
is arranged such that a detection axis of the magnetic sensor overlaps a Y
axis passing the center of the component and perpendicular to the X axis
in an arbitrary position on the Y axis or on its extended line; and
correcting circuit to correct the signals outputted from the X axis
magnetic sensor and the Y axis magnetic sensor in accordance with the
relative position between the magnetic sensor and the X axis and the Y
axis magnetic sensors.
With this configuration, since each of the X axis magnetic sensor and the Y
axis magnetic sensor can be arranged in an arbitrary position within a
predetermined distance from the center of the circular or substantially
circular component assuming magnetism in the vicinity of its circumference
by processing or in an arbitrary position on an arbitrary straight line
passing the center of the component such that the straight line and an
detection axis of magnetism coincide, freedom of designing can be further
increased, and miniaturization of an electronic instrument can be attained
while maintaining high precision.
An electronic instrument in accordance with an eighth aspect of the present
invention is an electronic instrument having a magnetic sensor
characterized in that the circular or substantially circular component
assuming magnetism in the vicinity of its circumference by processing is a
battery made of 304 stainless steel.
With this configuration, in conjunction with existing many electronic parts
such as a button battery that have the size of the above-mentioned
battery, an electronic instrument using such an electronic part can be
made higher in performance, further miniaturized, and so forth.
An electronic instrument in accordance with a ninth aspect of the present
invention is an electronic instrument having a magnetic sensor,
characterized in that the magnetic sensor, the Y axis magnetic sensor or
the X axis magnetic sensor consists of a two axis magnetic sensor that is
capable of measuring both the magnetic field components in the X axis
direction and in the Y axis direction perpendicular to the X axis.
With this configuration, since the two axes can be measured by one magnetic
sensor, an electronic instrument can be made higher in performance, more
miniaturized, and so forth.
An electronic instrument in accordance with a tenth aspect of the present
invention is characterized in that the electronic instrument is an
electronic azimuth indicator, a wristwatch with an electronic azimuth
indicator, a pressure gauge with an electronic azimuth indicator, a car
navigation terminal apparatus, a portable electronic instrument with an
electronic azimuth indicator, or an electronic instrument with an
electronic azimuth indicator.
With this configuration, freedom of designing many electronic instruments
such as the above-mentioned ones having magnetic sensors can be increased,
and miniaturization and higher performance of the electronic instruments
are made possible.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred form of the present invention is illustrated in the
accompanying drawings in which:
FIG. 1 is an equivalent circuit diagram for illustrating a function of a
general magnetic sensor to be used in an electronic instrument;
FIG. 2 is an illustration for showing the relationship between a detection
signal of a magnetic sensor and a direction of a magnetic field when the
magnetic sensor is caused to make a complete turn in an even magnetic
field;
FIG. 3 is a graph showing the relationship between a magnetic field
component and a detection voltage Vby when a magnetic sensor is caused to
make a complete turn in a magnetic field;
FIG. 4 is an illustration for showing an outer configuration, a size, and a
direction of a detection axis of a magnetic sensor used in data
measurement for the present invention;
FIG. 5 is an illustration showing an outer configuration of batteries used
in an experiment, and a data measuring position and a coordinate, as well
as measurement results by a magnetic sensor;
FIG. 6 is a graph plotting actual detection data of a Y axis magnetic
sensor in an even magnetic field and in a coordinate D of FIG. 5:
Y=-1.0,X=-1.0 of FIG. 5;
FIG. 7 is a graph plotting actual detection data of the Y axis magnetic
sensor in coordinates E, F, G and H in FIG. 5;
FIG. 8 is an exploded perspective view showing an electronic azimuth
indicator in accordance with an embodiment of the present invention;
FIG. 9 is a functional block diagram showing an electric configuration of
an electronic azimuth indicator 10 in accordance with an embodiment of the
present invention;
FIG. 10 is a circuit diagram showing more detailed embodiment of a Y axis
magnetic sensor 56, a X axis magnetic sensor 55, a sensor driving circuit
4, a the selection circuit 3 of FIG. 4.
FIG. 11 are diagrams each showing a display example of an electronic
azimuth indicator in accordance with an embodiment of the present
invention.
FIG. 12 are diagrams showing embodiments for showing in detail arranged
places of magnetic sensors X and Y in accordance with the present
invention.
FIG. 13 are illustrations showing examples of magnetism exhibited in the
vicinity of the circumference of 304 stainless steel and the like by die
cutting or part molding for forming the stainless steel and the like into
a circular shape, and an arrangement of an magnetic sensor for this
purpose;
FIG. 14 is a diagram showing a state of a magnetic field in which a
spherical magnetic body is arranged in an even magnetic field; and
FIG. 15 is an illustration explaining magnetism generated by elongation
when 304 stainless steel and the like is subjected to die cutting or
bending.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention will now be described with reference
to the drawings.
An equivalent circuit of a general one axis magnetic sensor is shown in
FIG. 1. A magnetic sensor 1 is for outputting an electric signal
corresponding to a deflection e .theta. with respect to a direction of a
magnetic field as a voltage difference between an output signals SYL and
SYH. The difference of the output voltage is amplified and converted to a
digital signal by a differential amplifier (not shown) and an A/D
converter.
A relationship between a direction of a magnetic field and a detection
signal of a magnetic sensor will now be described. FIG. 2 is a diagram
illustrating the relationship between a detection signal of a magnetic
sensor and a magnetic field in an even magnetic field. In FIG. 2, (1)
through (6) show a magnetic component By of the Y axis and detection
voltage Vby of the Y axis sensor in the respective directions when the
magnetic sensor makes completely turn in the even magnetic field, (b)
shows directions of the even magnetic field with respect to the magnetic
sensor, and (a) shows the relationship between the magnetic field
component By in the Y axis direction and the detection voltage Vby of the
Y axis sensor.
(1) in FIG. 2 shows a case in which the X axis of the magnetic sensor and
the magnetic field are in the same direction. Then, as can be seen from
(a), since the magnetic component By of the Y axis direction is "0", the
detection voltage Vby is also "0". (2) in FIG. 2 shows a case in which the
magnetic sensor and the magnetic field shift 45.degree. toward the Y axis.
(3) shows a state in which the direction of the magnetic field is the same
as the Y axis direction. The detection voltage Vby gradually increases as
the magnetic sensor turns around from (1) to (3), and when the magnetic
field is in the same direction as the Y axis ((3) in FIG. 2), the voltage
reaches its largest value. The magnetic sensor is further turned around
thereafter, the detection voltage Vby drops to "0" again in a state (4) in
which the magnetic field and the magnetic sensor are in the opposite
directions. Thereafter, the detection voltage reaches its largest value in
the opposite direction when the Y axis of the sensor and the magnetic
field are in the opposite directions (5), and then returns to the state in
the original position (6).
As the above description have made clear, the relationship between the
detection voltage Vb detected by the magnetic sensor and the direction of
the magnetic field By shows a linear relation as shown by dotted lines in
(b) of (1) through (6) in FIG. 2. Therefore, it is possible to calculate a
correct orientation from the voltage Vby that are in a detected output.
However, when something that is easily magnetized is placed in the even
magnetic field, since the magnetic field is affected and changes its
direction near a magnetic body as described above, it has been considered
difficult to detect a correct orientation when a magnetic sensor is placed
near a magnetic body.
This point will now be described with reference to FIG. 3. FIG. 3 is a
graph showing the relationship between the magnetic field component By and
the detection voltage Vby when the magnetic sensor is caused to make a
complete turn in the magnetic field as in FIG. 2. In order to make
description to be easily understood, a case in which nothing is placed in
an even magnetic field and a case in which an article that is susceptible
to magnetization is placed in the even magnetic field are is shown
schematically.
In FIG. 3, a line a indicates an output of the magnetic sensor when the
magnetic sensor is placed in the even magnetic field and is caused to made
a complete turn in the place, and a line b indicates an example of a case
in which an article that is susceptible to magnetization is placed in the
even magnetic field and the magnetic sensor is placed in the vicinity
thereof to make measurement in the place. A line c indicates an example of
a case in which an article that is susceptible to magnetization is placed
in the even magnetic field and measurement is made in another place near
the article.
As shown by the line a on the graph of FIG. 3, in the even magnetic field,
the detection voltage (Vby) of the magnetic sensor is proportional to the
magnetic field direction (By), and varies linearly passing the origin O.
On the other hand, on the line b indicating a case in which an article
that is susceptible to magnetization is placed near the magnetic sensor,
the detection voltage (Vby) of the magnetic sensor does not indicate a
linear proportional relationship with respect to the change of the
magnetic field direction (By), and deflection G is caused in the detection
voltage (Vby) by the magnetic field direction (By). In such a case,
detection of an accurate orientation is difficult.
The line c in FIG. 3 indicates a case in which an article that is
susceptible to magnetization is placed near the magnetic sensor, but the
magnetic sensor is arranged in a predetermined position. It is found that,
even if an article that is susceptible to magnetization is placed near the
magnetic sensor, the relation between the detection voltage (Vby) of the
magnetic sensor and the magnetic field direction (By) has linearity by
arranging the magnetic sensor in a predetermined position. However,
inclination of the straight line is different from that in the case of an
even magnetic field, and the line does not pass the origin O and is spaced
apart from the origin by "H". Therefore, since the relationship has
linearity, accurate measurement of orientation is possible if the
inclination and the "H" are corrected.
In addition, although not shown in the figure, the distance "H" from the
origin O and inclination of the straight line respectively vary depending
on a measurement position of the magnetic sensor. Details thereof will be
described later.
Under the above-mentioned prerequisite, the inventors of this patent
application measured and analyzed data using a button type battery (model
number CR2025) manufactured by Matsushita Denchi Kogyo Kabushiki Kaisha
and a button type battery (model number CR1616) manufactured by Kabushiki
Kaisha Sony Energy Tech in order to find mutual relationship among the
direction of a magnetic field, the position of a part that is susceptible
to magnetization and the position of a magnetic sensor. As a result, it
was found that a position exists where a detection voltage (Vby) of the
magnetic sensor varies linearly (hereinafter referred to as "has
linearity") in accordance with a direction of a magnetic field (By) even
in the vicinity of the battery. This indicates that it is possible to
arrange the magnetic sensor and the battery in proximity to each other
unlike the above-mentioned prior art.
Description will be made with reference to FIGS. 4 through 7. FIG. 4 is a
magnetic sensor of a magnetic resistance type used for the data
measurement in this experiment. The size of the magnetic sensor is
approximately 1.2 mm long, approximately 0.6 mm wide, and approximately
0.4 mm thick, which is extremely small. In addition, a detection axis of
magnetism is in a longitudinal direction of the magnetic sensor. Further,
the magnetic sensor is similar to a magnetic sensor described in the U.S.
Pat. No. 5,521,501.
In FIG. 4, reference numeral 55 denotes an X axis magnetic sensor for
detecting a magnetic field component in the X axis direction, and
reference numeral 56 denotes a Y axis magnetic sensor for detecting a
magnetic field component in the Y axis direction. The X axis magnetic
sensor 55 and the Y axis magnetic sensor 56 are implemented on a printed
substrate such that the detection axes are perpendicular each other.
FIG. 5 shows the outer configuration of the above-mentioned batteries
manufactured by Matsushita Denchi Kogyo Kabushiki Kaisha and Kabushiki
Kaisha Sony Energy Tech, and a data measuring position and a coordinate of
the above-mentioned magnetic sensor. FIG. 5 shows the X axis magnetic
sensor 55 and the Y axis magnetic sensor 56 when the center of the battery
is set in the center of the coordinate axes, the coordinates are divided
into a lattice shape with a predetermined distance interval, and the
magnetic sensors are arranged such that the point of intersection of the
detection axes coincide with the lattice.
Then, as a result of the measurement at each lattice point, if it is
recognized that there is linearity between variation of a magnetic field
direction (By) and a detection output (Vby), the X axis magnetic sensor 55
or the Y axis magnetic sensor 56 is circled, and, if not, the X axis
magnetic sensor 55 or the Y axis magnetic sensor 56 is crossed out.
Further, the battery used in this experiment has a thin cylindrical shape
of CR2025, and has a structure covered by the 304 stainless steel. A
diameter L and a lattice interval A of the battery are L=20 mm, A=5 mm in
the case of CR2025, and L=16 mm, A=4 mm in the case of CR1616.
Description will now be made using actual detection data. FIG. 6 is a graph
plotting actual detection data of the Y axis magnetic sensor in the even
magnetic field and in the coordinate D in FIG. 5: Y=-1.0,X=-1.0 (unit: cm)
when the battery CR2025 is used, where a line a indicates detection data
in the even magnetic field and a line d indicates detection data in the
coordinate D. As can be seen from FIG. 6, the line a indicating detection
outputs in the even magnetic field shows linearity passing the origin O,
and detection outputs measured near the battery form the line d in an oval
shape, which does not have linearity.
FIG. 7 is a graph plotting detection data of the Y axis magnetic sensor in
the coordinates E, F and G in FIG. 5 when the battery CR2025 is used. A
line e in an oval shape shows detection data of the Y axis magnetic sensor
in the coordinate E: Y=-1.0, X=-0.5, and it will be seen that the line
does not have linearity as in the case of the coordinate D. A line f plots
detection data of the Y axis magnetic sensor in the coordinate F: Y=-0.5,
X=-0.5, and it will be seen that, although the line does not pass the
origin O, output of the magnetic sensor varies linearly in accordance with
the direction of the magnetic field. Lines g and h plot detection data of
the Y axis magnetic sensor in the coordinates G: Y=0, X=-0.5 and H:
Y=-1.0, X=0. As in the case of the line f, it will be seen that, although
the lines do not pass the origin O, output of the magnetic sensor varies
linearly in accordance with the direction of the magnetic field.
Therefore, linearity can be acquired if the sensor is arranged in a
predetermined area from the center, or even if the sensor is not arranged
in a predetermined area, linearity can be acquired when it is arranged on
the Y axis. Further, although not illustrated, the X axis magnetic sensor
has results similar to the above.
FIG. 5 shows whether or not linearity can be acquired in detection results
for each measurement position. In FIG. 5, detection outputs of the X axis
magnetic sensor and the Y axis magnetic sensor are measured for each
coordinate position shown in the figure as described above, and
measurement results are shown for each coordinate position. Through these
measurements as well as collection and analysis of data, the following
facts have been found. As to be seen from FIG. 7, if the Y axis magnetic
sensor is arranged in a distance within approximately 2.sup.-1/2 of the
radius R from the center of a battery 20, detection output (Vby) has
linearity whichever position the sensor is located. FIG. 7 shows the
detection output of the Y axis magnetic sensor, while detection outputs
(Vbx) of the X axis magnetic sensor also has linearity as shown in FIG. 5.
In addition, although FIG. 7 shows detection data of a battery with the
diameter of 20 mm, batteries with different diameters show similar
characteristics. In a battery with the diameter of 16 mm manufactured by
Kabushiki Kaisha Sony Energy Tech, detection data in the coordinate
X=-0.4, Y=-0.4 (unit: cm) shows that the magnetic sensor output (Vby)
varies linearly in accordance with change in the direction of the magnetic
field (By) similar to the data of the coordinate F in FIG. 7.
In addition, distribution of determinations on the presence or absence of
linearity for each coordinate position in the battery with the diameter of
16 mm has the same results as the battery with the diameter of 20 mm.
However, in this case, the measurement position interval A shown in FIG. 5
is A=0.4 cm.
Further, it has been found that, even if the X axis magnetic sensor X or
the Y axis magnetic sensor Y is arranged in a position exceeding
approximately 2.sup.-1/2 of the radius R, when the detection axes (XA, YA)
of these sensors are arranged such that the axes overlap an axis passing
the center O of the battery 20, linearity is acquired between change in
the direction of the magnetic field and the detection output. In this way,
if linearity is acquired between the change in the direction of the
magnetic field and the detection output, even if the detection axes are
shifted from the origin O or the inclination is different, an accurate
orientation can be calculated by correcting these deflections.
An embodiment of the present invention will now be described with reference
to FIG. 8. FIG. 8 is an exploded perspective view showing a physical
structure of an electronic azimuth indicator in accordance with the
embodiment of the present invention. FIG. 8 shows only parts necessary for
describing the present invention, and smaller parts such as a control unit
are omitted. Basically, the electronic azimuth indicator is composed of a
battery 51, two magnetic sensors 55 and 56 for detecting magnetic field
components of the X axis and the Y axis, and a liquid crystal panel 58
that is a display unit.
The button type battery 51 with a metal such as 304 stainless steel
covering its exterior is mounted on a circuit substrate 54 via a battery
plus terminal 52 and a frame A while being pressed by a battery cover 50.
The battery plus terminal 52 is fixed to the circuit substrate 54 by lock
screws 60. A battery minus terminal 59 is provided on the circuit
substrate 54 such that the battery minus terminal 59 is pressingly brought
into contact with the minus terminal portion of the battery 51 when the
battery 51 is mounted.
On the circuit substrate 54, the X axis magnetic sensor 55 for detecting
magnetic field component in the X axis direction and the Y axis magnetic
sensor 56 for detecting magnetic field component in the Y axis direction
are provided in positions close to the center of the battery 51. A frame B
is provided under the circuit substrate 54, and the liquid crystal panel
58 is fixed under the frame B. The liquid crystal panel 58 consists of a
liquid crystal and a pair of sheets, at least one of which is transparent,
for sealing the liquid crystal therebetween. In the liquid crystal panel a
plurality of liquid crystal pixels are arranged in a matrix-line manner,
and each pixel is driven by an electronic signal. The liquid crystal panel
58 is electrically connected to the circuit substrate by a pair of
connectors 57 and performs displaying based on a control signal from a
control unit (not shown). Further, the liquid crystal panel 58 may be the
one in which all the contents that should be displayed are arranged
segmentally in advance using segments.
In this embodiment, miniaturization of the electronic azimuth indicator is
attained by providing the magnetic sensors 55 and 56 close to the center
of the battery 51. In this way, as described above, since outputs of the
magnetic sensors 55 and 56 have linearity with respect to the direction of
the magnetic field as long as the magnetic sensors 55 and 56 are arranged
in arbitrary positions within an area in a predetermined distance from the
center of the battery 51, or on the X axis passing the center of the
battery or on the Y axis perpendicular to the X axis, even if the magnetic
sensors are in the lower or the upper sides of the battery 51, the
accuracy in the orientation detection is not be deteriorated. Therefore,
the magnetic sensors can be arranged in arbitrary positions within the
above-mentioned area according to necessities of planning or designing,
and miniaturization, improvement of design, and reduction of costs can be
attained.
FIG. 9 is a functional block diagram showing an electric configuration of
an electronic azimuth indicator 10 in accordance with an embodiment of the
present invention. For ease of understanding, parts that are functionally
identical with those in FIG. 8 are denoted by the same numbers. As in FIG.
8, a Y axis magnetic sensor 56 is a magnetic sensor for detecting magnetic
field component in the Y axis direction, and an X axis magnetic sensor 55
is a magnetic sensor for detecting magnetic field component in the X axis
direction, which detect deflection amounts of the X axis and the Y axis
with respect to the geomagnetism as electric signals and output them.
A sensor driving circuit 4 provides driving power to the magnetic sensors
55 and 56. A selection circuit 3 selects the magnetic sensor 55 or 56 that
should detect a signal in accordance with control signals ENY and ENX from
a control circuit 8. A detection signal from the magnetic sensor 55 or 56
selected by the selection circuit 3 is converted to a digital signal from
an analog signal by an A/D converting circuit 5.
A correcting circuit 6 corrects an output signal from the A/D converting
circuit 5 in accordance with installed places or characteristics of the
magnetic sensors 55 and 56. As shown in the line c of FIG. 3, although a
detection output having linearity with respect to changes in the direction
of the magnetic field can be acquired from the magnetic sensors 55 and 56
arranged in a predetermined position near a battery 51, an output value is
deflected by "H" from the origin O in accordance with the arranged places
of the magnetic sensors unlike the case in which the magnetic sensors are
arranged in the even magnetic field. Therefore, an accurate orientation is
calculated by correcting, using the correcting circuit 6, the deflection
due to the arranged places of the magnetic sensors, bias due to
characteristics and the like held by each magnetic sensor, as well as
shift (declination) of the magnetic north and the north on the map.
An orientation display signal corrected by the correcting circuit 6 is
supplied to a displaying circuit 7, and is displayed by the displaying
circuit 7 under the control of a controlling circuit 8. Here, as is
evident to those having ordinary skills in the art, the controlling
circuit 8 and the correcting circuit 6 may respectively be composed of a
microprocessor and an RAM, an ROM and the like storing therein a
predetermined program or data.
More detailed embodiment of the Y axis magnetic sensor 56, the X axis
magnetic sensor 55, the sensor driving circuit 4, and the selection
circuit 3 of FIG. 9 is shown in FIG. 10. Either of the magnetic sensor 55
or 56 is selected by the control signal ENX or ENY from the controlling
circuit 8, and electric power is supplied to the selected magnetic sensor
55 or 56 from the sensor driving circuit 4.
ENY and ENX are not in the active state (are not "H") simultaneously. When
ENY is "H", a transistor 11 is in the on state, and driving electric power
is supplied to the Y axis magnetic sensor 56. Since switching gates 13 and
14 are open and gates 15 and 16 are closed, output signals SYH and SYL
from the Y axis magnetic sensor 56 are sent to the A/D converting circuit
5. Since the gates 15 and 16 are closed then, the output signals SYH and
SYL are differential amplified by the A/D converting circuit 5 and, at the
same time, are outputted as digital signals corresponding to volumes of
the output signals.
Similarly, ENX is a signal for selecting the X axis magnetic sensor 55
which supplies electric power to the X axis magnetic sensor 55 by turning
on a transistor 12 and, at the same time, sends outputs SXH and SXL of the
X axis magnetic sensor 55 to the A/D converting circuit 5 by opening the
switching gates 15 and 16.
As shown in FIG. 9, the output signals SXH, SXL, SYH and SYL are
analog/digital converted in the A/D converting circuit 5, and are
displayed by the displaying circuit 7 via the correcting circuit 6.
Examples of a case in which display is made by an electronic azimuth
indicator 70 are shown in FIG. 11. For example, if the electronic azimuth
indicator 70 is directed to the north, a direction indication mark 71
represented by a bold arrow, an orientation 72 represented as N, and a
bias angle 73 from the north are shown in FIG. 11A. In this case, since
the orientation is "N", that is the north, and the bias is "0", the figure
indicates that the direction of the direction indication mark 71 is the
north (more strictly, the magnetic north). In FIG. 11B, since the
orientation 72 is "NE", that is the northeast, and the angle 73 from the
north is "45", the figure indicates that the direction of the direction
indication mark 71 is in the orientation 450 from the north. Similarly,
FIG. 11C indicates that the direction of the direction indication mark 71
is the east, which is in the orientation 900 from the north. Although
display form such as the above is shown here, those having ordinary skills
in the art can freely select a display form, a display method, a display
medium and the like, for example, an LED may be lit instead of the arrow
of the direction indication mark 71.
Arrangement of the magnetic sensor will now be described more in detail
with reference to FIG. 12. FIG. 12 show embodiments for describing in
detail arranged places of magnetic sensors 55 and 56 in accordance with
the present invention. A component in a circular shape having magnetism
(for example, a battery consisting of a frame of 304 stainless steel) 21,
the X axis magnetic sensor 55 and the Y axis magnetic sensor 56
respectively provided in an electronic instrument 30 are shown in FIG. 12A
through FIG. 12E. FIG. 12A and FIG. 12B of are examples in which the X
axis magnetic sensor 55 and the Y axis magnetic sensor 56 are arranged in
a distance within 2.sup.-1/2 of the radius R from the center O of a
component 21. The sensors can be arranged in arbitrary positions as long
as the positions are within the area. Detection axis orientations of the
sensors do not need to be on an axis passing the center O of the
component. The X axis magnetic sensor 55 and the Y axis magnetic sensor 56
are arranged such that their detection angles are perpendicular to each
other.
FIG. 12C shows an example of a case in which the X axis magnetic sensor 55
and the Y axis magnetic sensor 56 are arranged outside 2.sup.-1/2 of the
radius R of the component 21 and in the vicinity of the circumference of
the component 21. In this case, the magnetic sensor 55 or 56 must be
arranged on an X axis or a Y axis passing the center O of the component 21
such that the detection axes of the magnetic sensors 55 and 56 overlap the
X axis and the Y axis.
FIG. 12D is an example in which only the Y axis magnetic sensor 56 is
arranged outside the component 21 in FIG. 12C. In this case as well, the Y
axis magnetic sensor 56 must be arranged on the Y axis such that its
detection axis overlaps the Y axis passing the center of the component 21.
In FIG. 12E, the X axis magnetic sensor 55 is arranged in a position
slightly outside the circumference of the component 21, and the Y axis
magnetic sensor 56 is provided in a position within 2.sup.-1/2 of the
radius R from the center of the component 21. In this case, although the X
axis magnetic sensor 55 must be on the X axis passing the center O of the
component 21 as in FIG. 12C and FIG. 12D, the Y axis magnetic sensor 56
can be provided in an arbitrary position within 2.sup.-1/2 of the radius
R.
FIG. 13 show arrangements of the X axis magnetic sensor 55 and the Y axis
magnetic sensor 56 in a case in which a place assuming magnetism varies
depending upon stress applied by bending or die cutting and materials. For
example, if a place assuming magnetism is limited to a considerabl
