U.S. patent application number 11/466776 was filed with the patent office on 2006-12-14 for long magnetic sensor.
This patent application is currently assigned to MURATA MANUFACTURING CO., LTD.. Invention is credited to Tamotsu MINAMITANI, Masanaga NISHIKAWA, Koji SHINMURA, Masaya UEDA.
Application Number | 20060279280 11/466776 |
Document ID | / |
Family ID | 34908808 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060279280 |
Kind Code |
A1 |
MINAMITANI; Tamotsu ; et
al. |
December 14, 2006 |
LONG MAGNETIC SENSOR
Abstract
A plurality of magnetosensitive portions of a plurality of
magnetic resistance elements and a plurality of magnets are aligned
substantially linearly to be perpendicular to a moving direction of
a detection object, and directions of magnetic poles of the magnets
are alternately inversed, such that directions of magnetic fluxes,
which are perpendicular to a surface on which the magnetosensitive
portions of the magnetic resistance elements are arranged, of the
continuously disposed magnets, are alternately inverse.
Inventors: |
MINAMITANI; Tamotsu;
(Nagaokakyo-shi, Kyoto-fu, JP) ; SHINMURA; Koji;
(Nagaokakyo-shi, Kyoto-fu, JP) ; UEDA; Masaya;
(Nagaokakyo-shi, Kyoto-fu, JP) ; NISHIKAWA; Masanaga;
(Nagaokakyo-shi, Kyoto-fu, JP) |
Correspondence
Address: |
MURATA MANUFACTURING COMPANY, LTD.;C/O KEATING & BENNETT, LLP
8180 GREENSBORO DRIVE
SUITE 850
MCLEAN
VA
22102
US
|
Assignee: |
MURATA MANUFACTURING CO.,
LTD.
10-1 Higashikotari 1-chome
Nagaokakyo-shi
JP
|
Family ID: |
34908808 |
Appl. No.: |
11/466776 |
Filed: |
August 24, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP05/02854 |
Feb 23, 2005 |
|
|
|
11466776 |
Aug 24, 2006 |
|
|
|
Current U.S.
Class: |
324/252 |
Current CPC
Class: |
G01R 33/09 20130101;
G07D 7/04 20130101 |
Class at
Publication: |
324/252 |
International
Class: |
G01R 33/02 20060101
G01R033/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2004 |
JP |
2004-054767 |
Claims
1. A long magnetic sensor comprising: a plurality of magnetic
resistance elements which are provided with magnetosensitive
portions on surfaces thereof or in the vicinities of the surfaces,
a longitudinal direction of each of the magnetosensitive portions
being substantially perpendicular to a moving direction of a
detection object; and a plurality of magnets arranged to apply
magnetic fields to the magnetosensitive portions of the plurality
of magnetic resistance elements; wherein the magnetosensitive
portions of the plurality of magnetic resistance elements and the
plurality of magnets are aligned substantially linearly to be
substantially perpendicular to the moving direction of the
detection object; and the plurality of magnets are disposed such
that directions of magnetic fluxes, which are substantially
perpendicular to the surfaces with the magnetosensitive portions of
the plurality of magnetic resistance elements, of adjacent pairs of
the plurality of magnets are inverse to each other.
2. The long magnetic sensor according to claim 1, wherein the
plurality of magnets are disposed in one-to-one correspondence with
the plurality of magnetic resistance elements.
3. The long magnetic sensor according to claim 1, wherein each of
the plurality of magnetic resistance elements is disposed such that
at least two of the plurality of magnets define a unit in the order
of arrangement of the plurality of magnets, and each of the
plurality of magnetic resistance elements entirely spans the at
least two magnets.
4. The long magnetic sensor according to claim 3, wherein the at
least two of the plurality of magnets includes two magnets.
5. The long magnetic sensor according to claim 3, wherein the at
least two of the plurality of magnets includes three magnets.
6. The long magnetic sensor according to claim 1, wherein each of
the plurality of magnetic resistance elements is disposed to span
the adjacent magnets at each of positions at which the plurality of
magnets are adjacent to each other.
7. The long magnetic sensor according to claim 1, further
comprising: a case arranged to house the plurality of magnetic
resistance elements and the plurality of magnets; wherein frames
are provided in the case such that the plurality of magnets are
disposed along an alignment direction of the plurality of magnetic
resistance elements in a zigzag manner in a plane parallel to the
magnetosensitive portions of the plurality of magnetic resistance
elements.
8. The long magnetic sensor according to claim 1, further
comprising: a case arranged to house the plurality of magnetic
resistance elements and the plurality of magnets; and a cover
arranged to cover the plurality of magnetic resistance elements and
the plurality of magnets.
9. The long magnetic sensor according to claim 8, wherein the case
is made of a synthetic resin.
10. The long magnetic sensor according to claim 8, wherein the case
includes claw-engaging grooves, and the cover includes cover-fixing
claws which are engaged with the claw-engaging grooves.
11. A long magnetic sensor comprising: a case; a plurality of
magnets disposed on the case; a plurality of magnetic resistance
elements disposed on the plurality of magnets, and which are
provided with magnetosensitive portions on surfaces or in the
vicinities of the surfaces, a longitudinal direction of each of the
magnetosensitive portions being substantially perpendicular to a
moving direction of a detection object; wherein the plurality of
magnets applies magnetic fields to the magnetosensitive portions of
the plurality of magnetic resistance elements; the magnetosensitive
portions of the plurality of magnetic resistance elements and the
plurality of magnets are aligned substantially linearly to be
substantially perpendicular to the moving direction of the
detection object; and the plurality of magnets are disposed such
that directions of magnetic fluxes, which are substantially
perpendicular to the surfaces with the magnetosensitive portions of
the magnetic resistance elements, of the adjacent ones of the
magnets are inverse to each other.
12. The long magnetic sensor according to claim 11, wherein the
plurality of magnets are disposed in one-to-one correspondence with
the plurality of magnetic resistance elements.
13. The long magnetic sensor according to claim 11, wherein each of
the plurality of magnetic resistance elements is disposed such that
at least two of the plurality of magnets define a unit in the order
of arrangement of the plurality of magnets, and each of the
plurality of magnetic resistance elements entirely spans the at
least two magnets.
14. The long magnetic sensor according to claim 13, wherein the at
least two of the plurality of magnets includes two magnets.
15. The long magnetic sensor according to claim 13, wherein the at
least two of the plurality of magnets includes three magnets.
16. The long magnetic sensor according to claim 1, wherein each of
the plurality of magnetic resistance elements is disposed to span
the adjacent magnets at each of positions at which the plurality of
magnets are adjacent to each other.
17. The long magnetic sensor according to claim 11, wherein frames
are provided in the case such that the plurality of magnets are
disposed along an alignment direction of the plurality of magnetic
resistance elements in a zigzag manner in a plane parallel to the
magnetosensitive portions of the plurality of magnetic resistance
elements.
18. The long magnetic sensor according to claim 11, further
comprising a cover arranged to cover the magnetic resistance
elements and the magnets.
19. The long magnetic sensor according to claim 11, wherein the
case is made of a synthetic resin.
20. The long magnetic sensor according to claim 18, wherein the
case includes claw-engaging grooves, and the cover includes
cover-fixing claws which are engaged with the claw-engaging
grooves.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a long magnetic sensor for
detecting a magnetic pattern which is printed on, for instance,
paper money.
[0003] 2. Description of the Related Art
[0004] Magnetic sensors for distinguishing, for example, paper
money and securities on which predetermined patterns are printed
using magnetic inks are disclosed in Japanese Patent No. 2921262
(Patent Document 1) and Japanese Unexamined Patent Application
Publication No. 2003-107142 (Patent Document 2). A configuration of
the long magnetic sensor disclosed in Patent Document 1 is shown in
FIGS. 8A and 8B. FIG. 8A is a plan view showing magnetosensitive
portions with a cover being removed. In this example, magnetic
resistance elements (MR elements) 2a to 2e are provided with pairs
of magnetosensitive portions 20a to 20e, respectively. The magnetic
resistance elements 2a to 2e are aligned and fixed in a case 1. A
detection object is arranged in a direction that is perpendicular
to the longitudinal direction of such a long magnetic sensor
200.
[0005] FIGS. 9A and 9B are front elevation views showing a
structure of the lower portions of the magnetic resistance
elements, and the state of magnetic fields which are applied to the
magnetic resistance elements. Note that only three magnetic
resistance elements 2b to 2d are shown here. Magnets 5b to 5d are
disposed at lower portions of the magnetic resistance elements 2b
to 2d so that magnetic fluxes pass through the magnetic resistance
elements 2b to 2d perpendicularly.
[0006] FIG. 9B shows the state where magnetic substances (magnetic
inks) 101c, 101cd, and 101d of the detection object are in the
vicinity of the long magnetic sensor. The magnetic substances 101c,
101cd, and 101d reach the vicinity of the long magnetic sensor
sequentially with a time-lag. When the magnetic substances 101c,
101cd, and 101d are present within the magnetic fields produced by
the magnets 5c and 5d, concentration of the magnetic fluxes is
induced to the magnetic substances, and the magnetic flux density
of the magnetic fluxes passing through the magnetosensitive
portions 20c and 20d is increased. This causes an increase in the
resistances of the magnetic resistance elements, and thus, the
presence of the magnetic substances 101c, 101cd, and 101d is
detected.
[0007] However, many of the magnetic fluxes headed toward the
magnetic substance 101cd, which are located at the central portions
of the two adjacent magnetosensitive portions 20c and 20d, do not
pass through the magnetosensitive portions 20c and 20d, but rather,
pass through a gap Gh formed therebetween. Since changes in the
magnetic flux density of the magnetic fluxes passing through the
gap Gh do not alter a magnetic resistance effect due to the
magnetosensitive portions 20c and 20d, a detection level (detection
capability) in the vicinity of the gap Gh is degraded. FIG. 8B
shows exemplary characteristics of the detection level with respect
to locations in the longitudinal direction of the long magnetic
sensor.
[0008] However, the long magnetic sensor including the location
where the detection level is degraded as shown in FIG. 8B is
inappropriate when it is necessary to detect the magnetic substance
pattern extending over the detection object. To solve this problem,
as disclosed in Patent Document 2, a configuration is provided in
which magnets and magnetic resistance elements are disposed in a
zigzag arrangement, respectively, in a plane parallel to the
magnetosensitive portions of the magnetic resistance elements.
[0009] FIG. 10A shows a configuration of such a long magnetic
sensor. FIG. 10A is a plan view showing the magnetosensitive
portions with the cover being removed. In this example, the
magnetic resistance elements 2a to 2g are disposed in the case 1 in
a staggered, zigzag manner in a plane parallel to the
magnetosensitive portions. A detection object is arranged in a
direction that is perpendicular to the longitudinal direction of
the long magnetic sensor 200.
[0010] As described above, the arrangement of the plurality of
magnetic resistance elements 2a to 2g in a zigzag manner ensures a
substantially uniform detection level over the longitudinal
direction of the long magnetic sensor as shown in the exemplary
characteristics shown in FIG. 10B.
[0011] However, as shown in FIG. 10A, in the long magnetic sensor
in which the magnetic resistance elements are disposed in a zigzag
manner in a plane parallel to the magnetosensitive portions, the
locations of the two adjacent magnetic resistance elements may be
deviated from each other by a gap Gv in a moving direction of the
detection object. Accordingly, additional signal processing or data
processing is required for correcting a time-lag corresponding to
the positional deviation of Gv. In addition, since a correction
amount of the positional deviation between the adjacent magnetic
resistance elements may be different from that between other
adjacent magnetic resistance elements depending on the accuracy of
the moving speed of the detection object, it is difficult to
provide a uniform output.
[0012] Furthermore, while the detection object is moved between the
case of the long magnetic sensor and a conveying roller, if a
distance between the magnetosensitive portions and the detection
object is varied in a path between lines Lf and Lb as shown in FIG.
10A, the detection level may also be varied. Accordingly, it is
also difficult to properly adjust the distance between the
conveying roller and the long magnetic sensor.
SUMMARY OF THE INVENTION
[0013] To overcome the problems described above, preferred
embodiments of the present invention provide a long magnetic sensor
in which no substantial gap is provided at any detection position
in the longitudinal direction or in a direction that is
substantially perpendicular thereto (moving direction of an
detection object).
[0014] A long magnetic sensor according to a preferred embodiment
of the present invention includes a plurality of magnetic
resistance elements which are provided with magnetosensitive
portions on surfaces or in the vicinities of the surfaces, a
longitudinal direction of each of the magnetosensitive portions
being substantially perpendicular to a moving direction of a
detection object, and a plurality of magnets for applying magnetic
fields to the magnetosensitive portions of the magnetic resistance
elements, in which the magnetosensitive portions of the plurality
of magnetic resistance elements and the plurality of magnets are
aligned substantially linearly to be perpendicular to the moving
direction of the detection object, and the magnets are disposed
such that directions of magnetic fluxes, which are substantially
perpendicular to the surfaces with the magnetosensitive portions of
the magnetic resistance elements provided, of the adjacent magnets
are inverse to each other.
[0015] The magnets are preferably disposed in one-to-one
correspondence with the magnetic resistance elements.
[0016] Each of the magnetic resistance elements is preferably
arranged such that at least two of the plurality of magnets define
a unit in the order of arrangement of the magnets and the magnetic
resistance element entirely spans the at least two magnets.
[0017] Each of the magnetic resistance elements is preferably
arranged to span the adjacent magnets at each of positions where
the plurality of magnets are adjacent to each other.
[0018] Frames are preferably provided in a case for housing the
magnets such that the magnets are arranged along an alignment
direction of the magnetic resistance elements in a zigzag manner in
a plane parallel to the magnetosensitive portions of the magnetic
resistance elements.
[0019] Since directions of the magnetic poles of the adjacent
magnets which apply magnetic fields to the magnetic resistance
elements are inverse to each other, when considering the two
adjacent magnetic resistance elements, the magnetic fields are
distributed such that the lines of magnetic force extend upwardly
out from the lower portion of the magnetic resistance element, and
downwardly into the lower portion of the magnetosensitive portion
of the other magnetic resistance element adjacent to the
former.
[0020] Accordingly, when the magnetic substance of the detection
object reaches the position between the two adjacent magnetic
resistance elements, the magnetic flux density of the magnetic
fluxes passing through the magnetosensitive portions of the two
magnetic resistance elements is changed, thereby enabling the
detection of the magnetic substance.
[0021] In addition, since the positions of the plurality of
magnetic resistance elements of the long magnetic sensor are
linearly disposed, at the time of attaching the long magnetic
sensor to a device, a diameter of a roller for moving the detection
object, and a distance therebetween is easily adjusted. Further,
since the magnetic poles of the adjacent magnets are heteropolar,
the magnets are attracted to each other and do not repel each
other. Accordingly, the magnets are easily housed in magnet
housings of the case.
[0022] Since the magnets are disposed in one-to-one correspondence
with the magnetic resistance elements, the magnetic flux passes
perpendicularly through each magnetosensitive portion at the
central portion of the magnetosensitive portion of the magnetic
resistance element, similarly to the conventional art. Accordingly,
the detection characteristics similar to that of the conventional
art are obtained at the central portion of the magnetosensitive
portion.
[0023] Since each of the magnetic resistance elements is disposed
such that at least two of the plurality of magnets define a unit in
the order of arrangement of the magnets, and the magnetic
resistance element entirely spans the at least two magnets, the
number of the magnets is increased (at least twice) with respect to
that of the magnetic resistance elements, and positions of the
lines of magnetic force are arranged at a narrow pitch in a
direction toward the detection object.
[0024] Accordingly, an ability to compensate the degradation of the
output is enhanced at the end portions of the magnetosensitive
portion of the magnetic resistance element, and the output
characteristics similar to that of the conventional art are
provided at the central portion of the magnetosensitive
portion.
[0025] Since each of the magnetic resistance elements is arranged
to span the adjacent magnets at each of positions where the
plurality of magnets are adjacent to each other, the central
portion of the magnet is located between the two magnetic
resistance elements adjacent to each other. Generally, the magnetic
flux density of the central portion of the magnet is high and
stable as compared to the end portions thereof, the degradation of
the detection level between the magnetic resistance elements is
compensated for, thereby providing the detection level
characteristics having a flat line over the longitudinal direction.
In addition, even when the positions of the borders of the adjacent
magnets are unevenly disposed, the variation in the detection level
due to the unevenness is reduced.
[0026] Since the frames are arranged in the case such that the
magnets are disposed along the alignment direction of the magnetic
resistance elements in a zigzag manner in a plane parallel to the
magnetosensitive portions of the magnetic resistance elements, in
view of the design of the case structure for housing the magnetic
resistance elements and the magnets, the positions of the magnets
relative to the case are accurately determined, and consequently,
the long magnetic sensor with the attachment accuracy being
improved and the characteristics thereof being uniform is stably
produced.
[0027] Other features, elements, steps, characteristics and
advantages of the present invention will become more apparent from
the following detailed description of preferred embodiments of the
present invention with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIGS. 1A and 1B are external perspective views showing a
long magnetic sensor according to a first preferred embodiment of
the present invention.
[0029] FIGS. 2A-2C illustrate a positional relationship between
magnetic resistance elements and magnets of the long magnetic
sensor, and detection level characteristics with respect to
positions in the longitudinal direction.
[0030] FIGS. 3A and 3B illustrate a magnetic flux density
distribution due to the magnet of the long magnetic sensor, and a
change in magnetic flux density due to the presence of a magnetic
substance.
[0031] FIGS. 4A and 4B illustrate an example of a positional
relationship between the adjacent magnetic resistance elements, and
another example of a positional relationship between the adjacent
magnets.
[0032] FIGS. 5A and 5B illustrate positional relationships between
magnetic resistance elements and magnets of a long magnetic sensor
according to a second preferred embodiment of the present
invention.
[0033] FIG. 6 illustrates a positional relationship between
magnetic resistance elements and magnets of a long magnetic sensor
according to a third preferred embodiment of the present
invention.
[0034] FIG. 7 illustrates a positional relationship between
magnetic resistance elements with respect to a case, of a long
magnetic sensor according to a fourth preferred embodiment.
[0035] FIGS. 8A and 8B illustrates a configuration of a long
magnetic sensor disclosed in Patent Document 1, and exemplary
characteristics thereof.
[0036] FIGS. 9A and 9B illustrate an example of a magnetic flux
density distribution of the long magnetic sensor.
[0037] FIGS. 10A and 10B illustrate a configuration of a long
magnetic sensor disclosed in Patent Document 2, and exemplary
characteristics thereof.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0038] A configuration of a long magnetic sensor according to a
first preferred embodiment of the present invention will be
described below with reference to FIGS. 1A to 4B.
[0039] FIGS. 1A and 1B are external perspective views showing a
long magnetic sensor, in which FIG. 1A shows the state in the
middle of attaching a cover, and FIG. 1B shows the state with the
cover attached. Magnetic resistance elements 2a, 2b, 2c, 2d . . .
are mounted on the upper portion of a case 1 made of synthetic
resin. Terminal pins 6 which are connected to the plurality of
magnetic resistance elements 2a, 2b, 2c, 2d . . . project at the
lower portion of the case 1. Claw-engaging grooves 3 are provided
on both lateral sides of the case 1 along the longitudinal
direction.
[0040] A metal cover 4 is provided with cover-fixing claws which
are engaged with the claw-engaging grooves 3 of the case. When the
cover 4 slides in the longitudinal direction while both the
claw-engaging grooves 3 and the cover-fixing claws are engaged with
each other, the cover 4 covers the upper portion of the case 1 as
shown in FIG. 1B. A detection object 100 is moved in a direction
substantially perpendicular to the longitudinal direction of the
long magnetic sensor 200 as shown by an arrow in the drawing.
[0041] The cover 4 is provided with a cover terminal 11 to be
electrically ground connected to a circuit board.
[0042] FIG. 2A is a plan view showing a state with the cover
removed from the long magnetic sensor shown in FIGS. 1A and 1B.
FIG. 2B is a cross-sectional view taken along a plane perpendicular
to the surface with magnetosensitive portions provided thereon, and
passing through the plurality of magnetic resistance elements and
the plurality of magnets. Note that FIGS. 2A and 2B only show the
magnetic resistance elements 2a to 2e. In addition, FIG. 2B, the
illustration of the case 1 is omitted.
[0043] Magnets 5a to 5e are provided at the lower portions of the
magnetic resistance elements 2a to 2e, respectively.
Magnetosensitive portions 20a to 20e are provided at the magnetic
resistance elements 2a to 2e, respectively. When the detection
object 100 shown in FIG. 1B is a sheet of paper, such as paper
money, while the object may not always be moved in a direction
exactly perpendicular to the longitudinal direction of the long
magnetic sensor 200, the magnetosensitive portions 20a to 20e are
provided on the surfaces or in the vicinities of the surfaces of
the magnetic resistance elements 2a to 2e such that the
longitudinal direction of the magnetosensitive portions 20a to 20e
are substantially perpendicular to the moving direction of the
detection object.
[0044] Directions of magnetic poles (N-pole and S-pole) of the
magnets 5a to 5e are arranged such that the magnetic fluxes pass
substantially perpendicularly through the magnetic resistance
elements 2a to 2e, and the directions of the magnetic poles of the
adjacent magnet are inverse to each other. That is, the N-pole of
the magnet 5a faces the magnetic resistance element 2a, while the
S-pole of the magnet 5b which is adjacent to the magnet 5a faces
the magnetic resistance element 2b. Then the N-pole of the magnet
5c which is adjacent to the magnet 5b faces the magnetic resistance
element 2c. Similarly to the above-described arrangement, the
direction of the magnetic poles of the adjacent magnets is inverse
to each other.
[0045] FIGS. 3A and 3B are examples of a magnetic field
distribution when the directions of the magnetic poles of the
magnets are disposed as shown in FIG. 2A. As shown in FIG. 3A,
lines of magnetic force from the N-pole of the magnet 5c extend
upwardly and pass through the magnetosensitive portion 20c of the
magnetic resistance element 2c. Then the lines of magnetic force
extend downwardly through the magnetosensitive portions 20b and 20d
of the magnetic resistance elements 2b and 2d, and then to the
S-poles of the magnets 5b and 5d. At this time, the lines of
magnetic force of the magnetic flux from the N-pole of the magnet
5c are curved in a loop form and then extend to the S-poles of the
adjacent magnets 5b and 5d.
[0046] As shown in FIG. 3B, when the magnetic substances 101c,
101cd and 101d of the detection object are in the vicinities of the
magnetic resistance elements 2c and 2d, and the magnetosensitive
portions 20c and 20d, sequentially with a time-lag, the magnetic
flux heading toward the magnet 5d from the magnet 5c is attracted
by the magnetic substance 101cd, passes through the
magnetosensitive portions 20c and 20d of the magnetic resistance
elements 2c and 2d nearly perpendicularly, and the magnetic flux
density thereof is increased. Consequently, the presence of the
magnetic substance 101cd is detected due to the change in
resistances of the magnetic resistance elements 2c and 2d. In
addition, since the magnetic flux density of the magnetic flux
passing through the magnetosensitive portion 20c of the magnetic
resistance element 2c is increased because of the presence of the
magnetic substance 101c, it is detected that the magnetic substance
101c has reached this location due to the change in the resistance
of the magnetic resistance element 2c. Similarly, since the
magnetic flux density of the magnetic flux passing through the
magnetosensitive portion 20d of the magnetic resistance element 2d
is increased because of the presence of the magnetic substance
101d, it is detected that the magnetic substance 101d has reached
this position due to the change in the resistance of the magnetic
resistance element 2d.
[0047] FIG. 2C shows exemplary characteristics of the detection
level with respect to positions of the long magnetic sensors in the
longitudinal direction. When the magnetic resistance element is
viewed in a plane parallel to the magnetosensitive portion, since
the magnetic substance is detected even at a position where the
magnetosensitive portion is not provided, as shown in the drawing,
the detection level is not degraded at any position in the
longitudinal direction of the long magnetic sensor and provides a
substantially uniform detection level.
[0048] In the examples as shown in FIGS. 2A through 3B, while small
gaps are provided between the adjacent magnets and between the
adjacent magnetic resistance elements, the continuously disposed
magnets 5a, 5b and 5c are closely attached as shown in FIG. 4A.
Alternatively, as shown in FIG. 4B, the gap between the
continuously disposed magnets 5a, 5b and 5c may be different from
that of the continuously disposed magnetic resistance elements 2a,
2b and 2c, namely, the gap between the magnets 5a, 5b and 5c may be
larger than that among the magnetosensitive portions 20a, 20b and
20c of the magnetic resistance elements 2a, 2b and 2c.
[0049] Next, a long magnetic sensor according to a second preferred
embodiment will be described below with reference to FIGS. 5A and
5B.
[0050] As shown in an example in FIG. 5A, the magnetic resistance
element is disposed such that two of the plurality of magnets
define a unit in the order of arrangement, and the magnetic
resistance element spans the two magnets. Particularly, a magnetic
resistance element 2ab is arranged to span the magnets 5a and 5b.
In addition, a magnetic resistance element 2cd is arranged to span
the magnets 5c and 5d.
[0051] With this structure, the magnetic flux from the magnet 5a
comes into the adjacent magnet 5b. The magnetic flux from the
magnet 5a passes through the left portion of the magnetosensitive
portion 20ab, then passes through the right portion thereof, and
then extends into the magnet 5b. Similarly, the magnetic flux from
the magnet 5c passes through the left portion of a magnetosensitive
portion 20cd, then passes through the right portion thereof, and
then extends into the magnet 5d. Further, the magnetic flux from
the magnet 5c passes through the left portion of the
magnetosensitive portion 20cd, then passes through the right
portion of the magnetosensitive portion 20ab, and then extends into
the magnet 5b.
[0052] Accordingly, when viewed in a plane parallel to the
magnetosensitive portion, if the magnetic substance of the
detection object is present at the central portion of the
magnetosensitive portion 20ab, 20cd, the presence of the magnetic
substance is detected due to the change in the resistance of the
magnetic resistance element provided with the magnetosensitive
portion. In addition, if the magnetic substances is present at a
position where the magnetosensitive portion is not provided, such
as a position between the magnetosensitive portions 20ab and 20cd,
similarly to the first preferred embodiment, the presence of the
magnetic substance is detected due to the change in the resistances
of both the magnetic resistance elements 2ab and 2cd provided with
the magnetosensitive portions 20ab and 20cd.
[0053] In addition to the example shown FIG. 5A, the magnetic
resistance elements may be disposed such that, for instance as
shown in FIG. 5B, three magnets (5a, 5b and 5c) and (5d, 5e and 5f)
define units, respectively, in the order of arrangement, and
magnetic resistance elements 20abc and 20def entirely span the
units of the magnets, respectively. Alternatively, four or more
magnets may define a unit. That is, a magnetic resistance element
may be disposed such that at least two of the magnets define a
unit, and the magnetic resistance element entirely spans the at
least two magnets.
[0054] Next, a long magnetic sensor according to a third preferred
embodiment will be described below with reference to FIG. 6.
[0055] In this example, a magnetic resistance element is disposed
to span the adjacent magnets, at each of positions where the
magnets are adjacent to each other. In this example, the magnetic
resistance element 2ab is disposed to span the magnets 5a and 5b.
Then, a magnetic resistance element 2bc is disposed to span the
magnets 5b and 5c. In addition, the magnets 5a, 5b and 5c are
disposed such that the magnetic poles of the continuously disposed
magnets are alternately inverse to one another.
[0056] With this configuration, the central portion of the magnet
is located at a position corresponding to a gap provided between
the magnetosensitive portions of the two adjacent magnetic
resistance elements. In the example shown in FIG. 6, the central
portion of the magnet 5b is located at a position corresponding to
a gap Gh provided between the magnetosensitive portions 20ab and
20bc of the magnetic resistance elements 2ab and 2cd. Since the
magnetic flux density of the central portion of the magnet is high
and stable as compared with that of the end portions, the magnetic
flux density between the adjacent magnetosensitive portions is
greater than other region. Consequently, the degradation of the
detection level at the position corresponding to the gap Gh is
compensated for, and detection level characteristics having a flat
line over the longitudinal direction is obtained.
[0057] In addition, even when the borders of the adjacent magnets
are unevenly disposed, since the magnetic flux density at the
position corresponding to the gap Gh is maintained high, the
variation in the detection level due to the unevenness is reduced.
Note that the characteristics shown between the magnets are similar
to that of the second preferred embodiment.
[0058] Next, a long magnetic sensor according to a fourth preferred
embodiment will be described below with reference to FIG. 7.
[0059] FIG. 7 is a plan view partially showing a plane parallel to
the magnetosensitive portions of the magnetic resistance elements
of the long magnetic sensor. The magnetic resistance elements 2a to
2c are linearly disposed as shown by a chain line in FIG. 7. The
magnets 5a, 5b and 5c are disposed at the magnetic resistance
elements 2a, 2b and 2c, respectively. Unlike the first preferred
embodiment, frames 10 are provided at the bottom surface of the
case 1 such that the magnets are disposed along the arrangement of
the magnetic resistance elements 2a to 2c in a staggered manner in
a plane parallel to the magnetosensitive portions 20a, 20b and 20c
of the magnetic resistance elements. Accordingly, the frames 10
define magnet housings disposed in a zigzag manner, so that the
positions of the magnets can be easily determined relative to the
case by sequentially attaching the magnets to the frames 10. In
addition, since the directions of the magnetic poles of the
adjacent magnets are inverse to each other, and therefore the
magnets are attracted to each other to be linearly disposed as
shown by a chain line in the drawing, the positions of the magnets
can be automatically set in a direction that is substantially
perpendicular to the chain line in the drawing.
[0060] Note that FIG. 7 shows an example in which the arrangement
of the magnets relative to the case is applied to the first
preferred embodiment. However, this arrangement may be
alternatively applied to the second and third preferred embodiments
in a similar manner.
[0061] The present invention can be used for absorbing vibration
due to friction between moving plates.
[0062] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the present invention. The scope
of the present invention, therefore, is to be determined solely by
the following claims.
* * * * *