U.S. patent application number 10/782089 was filed with the patent office on 2004-08-26 for magnetic switch capable of performing normal detection for a long period of time.
This patent application is currently assigned to ALPS ELECTRIC CO., LTD.. Invention is credited to Okumura, Hirofumi.
Application Number | 20040164826 10/782089 |
Document ID | / |
Family ID | 32866507 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040164826 |
Kind Code |
A1 |
Okumura, Hirofumi |
August 26, 2004 |
MAGNETIC SWITCH CAPABLE OF PERFORMING NORMAL DETECTION FOR A LONG
PERIOD OF TIME
Abstract
A magnetic switch hardly affected by an external magnetic field
even if a cheap magnet is used and capable of performing magnetic
detection for a long period of time is provided. A first magnetic
path L1 and a second magnetic path L2 in which a stationary rail 13
and a movable rail 14 lead magnetic fluxes are formed in a
non-shielding state where magnetism shielding means 18 is not
interposed in a gap G between a magnet M and a Hall element H to
secure the number of magnetic fluxes that pass through the Hall
element H. Therefore, it is not necessary to use a costly rare
earth magnet having a large number of generated magnetic fluxes. In
n shielding state where the magnetism shielding means 18 is
interposed in the gap G, the first magnetic path L1 is shielded. As
a result, the number of magnetic fluxes that pass through the Hall
element H is almost zero. Since the magnet M and the Hall element H
are covered with the stationary rail 13 and the movable rail 14,
the magnetic switch is hardly affected by the external magnetic
field.
Inventors: |
Okumura, Hirofumi;
(Miyagi-ken, JP) |
Correspondence
Address: |
BEYER WEAVER & THOMAS LLP
P.O. BOX 778
BERKELEY
CA
94704-0778
US
|
Assignee: |
ALPS ELECTRIC CO., LTD.
|
Family ID: |
32866507 |
Appl. No.: |
10/782089 |
Filed: |
February 18, 2004 |
Current U.S.
Class: |
335/220 |
Current CPC
Class: |
H03K 17/9517 20130101;
B60N 2/0705 20130101; B60N 2002/0268 20130101; B60R 21/01554
20141001; H03K 17/9502 20130101; B60N 2/0244 20130101; B62H 1/02
20130101; B60N 2002/684 20130101; B60N 2/0715 20130101 |
Class at
Publication: |
335/220 |
International
Class: |
H01H 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2003 |
JP |
2003-045418 |
Claims
What is claimed is:
1. A magnetic switch, comprising: magnetism detecting means having
a Hall element that faces a magnet through a gap; and magnetism
shielding means provided so as to freely enter and exit the gap,
wherein the external surface of the magnetism detecting means is
covered with a case made of a magnetic material.
2. The magnetic switch according to claim 1, wherein the magnetism
shielding means is made of a magnetic material.
3. The magnetic switch according to claim 1, further comprising: a
stationary rail fixed to a floor; a movable rail guided by the
stationary rail and provided so as to be freely movable; and a seat
fixed to the movable rail and capable of being moved back and forth
along with the movable rail, wherein the magnetism detecting means
is provided in either the stationary rail or the movable rail, and
the magnetism shielding means is provided in the other.
4. The magnetic switch according to claim 1, further comprising: a
vehicle body; and a stand for supporting the vehicle body, wherein
the magnetism detecting means is provided in either the vehicle
body or the stand, or the magnetism shielding means is provided in
the other.
5. The magnetic switch according to claim 1, wherein the magnet and
the Hall element are integrally received in the case.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a magnetic switch including
a magnet and a Hall element, and particularly, to a magnetic switch
with excellent sensitivity, which is hardly affected by an external
magnetic field, even if a cheap magnet with a small number of
magnetic fluxes is used.
[0003] 2. Description of the Related Art
[0004] The invention described in Patent Document 1 is noted as an
example of conventional magnetic detection switches. As described
in FIGS. 2 to 7 of Patent Document 1, the magnetic detection switch
detects the position of a seat, freely movable back and forth,
provided in the body of a vehicle.
[0005] The seat is fixed to a movable rail provided so as to be
movable back and forth with respect to a stationary rail fixed to
the floor of the body of the vehicle. A laterally extending support
member is provided on the outside of the stationary rail. A
magnetic sensor is fixed to the support member. The magnetic sensor
has a detecting unit in which a pair of facing pieces is made of a
resin material and faces each other so as to with a U-shaped
section. A magnet is buried in one facing piece. A Hall element is
provided in the other facing piece. A flange having an L-shaped
section is provided on the side of the movable rail. The tip of the
flange is adapted to be capable of entering the detecting unit of
the magnetic sensor.
[0006] The tip of the flange is not interposed in the detecting
unit of the magnetic sensor when the seat is moved backward. The
tip of the flange is interposed in the detecting unit of the
magnetic sensor when the seat is moved to the foremost position. At
this time, it is possible to detect that the seat is moved to the
foremost position by shield the magnetic fluxes generated by the
magnet from reaching the Hall element.
[0007] [Patent Document 1]
[0008] U.S. Pat. No. 6,053,529
[0009] However, since the magnetic sensor described in Patent
Document 1 has a structure in which an exclusive magnetic path
through which magnetic fluxes pass does not exist between the N
pole and the S pole of the magnet, that is, an open loop structure,
the magnet is demagnetized, when it is used for a long period of
time, thus reducing the number of magnetic fluxes that pass through
the Hall element. Thus, a magnetic sensor is conceivable that is
operated by reducing the sensitivity of the Hall element to detect
only a small number of magnetic fluxes. However, in this case, the
magnetic sensor may erroneously operate due to the influence of a
small external magnetic field; in particular, a speaker of onboard
acoustic equipment may be provided near the floor on which the
magnetic sensor is provided. As a result, the magnetic sensor may
be affected by the external magnetic field generated by the
speaker, which result in an erroneous operation.
[0010] Further, in order to use the magnetic sensor with improved
sensitivity of the Hall element, a rare earth magnet with a large
number of generated magnetic fluxes may be used. However, in this
case, there is a problem that the cost of the magnetic sensor
jumps.
[0011] Since the magnetic sensor is arranged on the outside of a
rail, dusts (metal pieces) in the vehicle easily gathers in the
detecting unit having the U-shaped section. Therefore, the magnetic
fluxes that pass through the detecting unit are shielded by the
metal pieces in the dusts. As a result, the magnetic sensor
erroneously operates and cannot correctly detect the position of
the seat.
SUMMARY OF THE INVENTION
[0012] In order to solve the above problems, it is an object of the
present invention to provide a magnetic switch that is hardly
affected by an external magnetic field, even if a cheap magnet
having a small number of generated magnetic fluxes is used, and
that is capable of performing normal magnetic detection for a long
period of time.
[0013] According to the present invention, a magnetic switch
comprises magnetism detecting means having a Hall element that
faces a magnet through a gap and magnetism shielding means provided
so as to freely enter and exit the gap. The external surface of the
magnetism detecting means is covered with a case made of a magnetic
material.
[0014] According to the present invention, since a magnetic path
functioning as a passageway of magnetic fluxes is formed between
the magnet and the Hall element, the magnetic lines of force
generated by the magnet easily form a closed loop easily.
Therefore, it is possible to secure the required number of magnetic
fluxes. It is also possible to prevent demagnetization of the
magnet at an early stage. Further, since the Hall element is
provided in the magnetic path, the sensitivity of the Hall element
does not necessarily deteriorate, that is, it is possible to
maintain the sensitivity to larger than a predetermined level. As a
result, it is possible to reduce the likelihood of the erroneous
operation caused by an external magnetic field. Further, since the
external surface of the magnetic switch is covered with a magnetic
material, the magnetic switch is hardly affected by the external
magnetic field. Therefore, it is possible to provide a magnetic
switch with a high degree of precision.
[0015] The magnetism shielding means is preferably made of a
magnetic material.
[0016] According to the above structure, in an shielding state
where magnetism shielding means is interposed between the magnet
and the Hall element, it is possible to shield magnetic fluxes in
the magnetic path, which is expected to pass through the Hall
element, thus making the number of magnetic fluxes almost zero, and
to form a closed magnetic path between the path that is expected to
pass through the Hall element and the path that does not pass
through the Hall element. Therefore, it is possible to prevent
demagnetization of the magnet even if the shielding state continues
for a long period of time.
[0017] For example, the magnetic switch may comprise a stationary
rail fixed to the floor, a movable rail guided by the stationary
rail and provided so as to be freely movable, and a seat fixed to
the movable rail and capable of being moved back and forth along
with the movable rail. The magnetism detecting means is provided in
either the stationary rail or the movable rail and the magnetism
shielding means is provided in the other.
[0018] Otherwise, the magnetic switch may comprise a vehicle body
and a stand for supporting the vehicle body. The magnetism
detecting means is provided in one of the vehicle body and the
stand and the magnetism shielding means is provided in the
other.
[0019] Moreover, the magnet and the Hall element are preferably
integrally received in the case.
[0020] Since magnetism detecting means is compact, it is possible
to easily mount the magnetism detecting means in a predetermined
position of the movable rail.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a side view illustrating an onboard seat in which
a magnetic switch is used according to an embodiment of the present
invention;
[0022] FIG. 2 is a perspective view illustrating a seat-moving
mechanism;
[0023] FIG. 3 is a sectional view taken along the line III-III of
FIG. 2, which illustrates a magnetic switch provided in the
seat-moving mechanism;
[0024] FIG. 4 illustrates aspects of a magnetic field in a magnetic
detection switch. FIG. 4A illustrates a non-shielding state in
which a shielding member is not interposed. FIG. 4B illustrates a
shielding state in which the shielding member is interposed;
and
[0025] FIG. 5 illustrates another embodiment of the magnetic
switch. FIG. 5A is a side view illustrating a two-wheeled vehicle.
FIG. 5B is an enlarged side view illustrating a stand of the
two-wheeled vehicle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] FIG. 1 is a side view illustrating an onboard seat in which
a magnetic switch is used according to an embodiment of the present
invention. FIG. 2 is a perspective view illustrating a seat-moving
mechanism. FIG. 3 is a sectional view taken along the line III-III,
which illustrates a magnetic switch provided in the seat-moving
mechanism. FIG. 4 illustrates aspects of magnetic fields in a
magnetic detection switch. FIG. 4A illustrates a non-shielding
state in which a shielding member is not interposed. FIG. 4B
illustrates a shielding state in which the shielding member is
interposed.
[0027] As illustrated in FIGS. 1 to 3, the magnetic switch detects
the position of a seat in a vehicle.
[0028] As illustrated in FIG. 1, a seat 1 includes a chair 2, a
back 3, and a head 4 and is mounted on a seat-moving mechanism 10
provided on the floor of the vehicle. A handle (not shown) is
provided in front of the seat 1 if the seat 1 is a driver's seat. A
dashboard (not shown) is provided in front of the seat 1 if the
seat 1 is the assistant driver's seat. An air bag device (not
shown) is provided in the center of the handle and in the
dashboard. Should the vehicle collides with another vehicle, the
air bag device operates to rapidly expand the air bag in the air
bag device.
[0029] The seat-moving mechanism 10 includes a stationary rail 13
fixed to the floor through fixing members 11 and 12 and a movable
rail 14 provided to be fitted with the stationary rail 13. The
stationary rail 13 and the movable rail 14 are made of a metal
containing a magnetic material, such as iron or nickel.
[0030] As illustrated in FIG. 3, movable rollers 15 that freely
rotate are provided inside the stationary rail 13. A pair of
supporting parts 14a is bent in the form of a letter "U" at the
ends of the movable rail 14 and is put on the movable rollers 15.
Therefore, the movable rail 14 may be freely moved back and forth
with respect to the stationary rail 13. The seat 1 is connected and
fixed at the bottom of the chair 2 thereof to the movable rail 14.
Therefore, it is possible to control the position of the seat 1 in
its forward and backward direction.
[0031] The seat-moving mechanism 10 is provided with regulating
means (not shown) for regulating the forward movement of the
movable rail 14 when the amount of forward movement of the seat 1
reaches a certain point (when the seat 1 is located at its foremost
position). Also, a locking member (not shown) for locking the
movable rail 14 in the position where the forward and backward
movement of the seat 1 is prevented and an unlocking member (not
shown) for unlocking the movable rail 14 to allow the movement of
the movable rail 14 are provided.
[0032] As illustrated in FIG. 2, magnetism detecting means 20 is
provided inside the movable rail 14. The magnetism detecting means
20 is covered with a case 21 made of a resin material. A pair of
facing pieces 21a and 21b is provided underneath the case 21. A
magnet M is provided inside the one facing piece 21a, and a Hall
element H is provided inside the other facing piece 21b. The magnet
M is magnetized in such a manner that one surface (the illustrated
right end) thereof is N pole and the other surface (the illustrated
left end) thereof is S pole. A gap G is provided between the facing
piece 21a and the facing piece 21b.
[0033] Magnetism shielding means 18 is provided at the front
position of the stationary rail 13. The magnetism shielding means
18, made of a magnetic material, such as iron or nickel, is adapted
to enter the gap G of the magnetism detecting means 20.
[0034] When the seat 1 is moved to the foremost position,
regulating means (not shown) operates to regulate the forward
movement of the movable rail 14. At this time, as illustrated in
FIG. 3, the magnetism shielding means 18 is interposed in the gap G
of the magnetism detecting means 20.
[0035] When the seat 1 is located other than the foremost position,
the magnetism shielding means 18 is not interposed in the gap G of
the magnetism detecting means 20.
[0036] As illustrated in FIG. 4A, in a state where the magnetism
shielding means 18 is not interposed in the gap G of the magnetism
detecting means 20 (the non-shielding state), a first magnetic path
L1 is formed. In the first magnetic path L1, the magnetic fluxes
generated by one surface (the N pole) of the magnet M enter the
movable rail 14 from one side of the movable rail 14 made of the
magnetic material, come out from the other side of the movable rail
14 through movable rail, and reach the other surface (the S pole)
of the magnet M. At the same time, a second magnetic path L2 is
formed. In the second magnetic path L2, the magnetic fluxes that
enter the movable rail 14 from one side thereof comes out from the
movable rail 14, enter the side of the stationary rail 13, pass
through the stationary rail 13, come out from the bottom of the
stationary rail 13, and reach the other surface (the S pole) of the
magnet M. The Hall element H is provided to be located in the
course of the first magnetic path L1 and is set to the ON state in
the non-shielding state.
[0037] As illustrated in FIG. 4B, in a state where the magnetism
shielding means 18 is interposed in the gap G of the magnetism
detecting means 20 (the shielding state), since the magnetism
shielding means 18 is provided between the magnet M and the Hall
element H to face them, magnetic paths L3 and L4 are formed. In the
magnetic paths L3 and L4, the magnetic fluxes generated by one
surface (the N pole) of the magnet M enter the movable rail 14 from
one side thereof, enter both sides of the stationary rail 13 from
both sides of the movable rail 14, pass through the stationary rail
13, are transmitted to the magnetism shielding means 18 provided on
the bottom of the stationary rail 13, come out from the tip of
magnetism shielding means 18, and reach the other surface (the S
pole) of the magnet M. At the same time, the magnetism shielding
means 18 can shield the first magnetic path L1, making the number
of magnetic fluxes that pass through the Hall element H almost
zero. Therefore, the output of the Hall element H is set to the OFF
state in the shielding state.
[0038] As mentioned above, the magnetism shielding means 18 and the
magnetism detecting means 20 constitute a magnetic switch for
switching the output thereof in response to the presence or absence
of the magnetic fluxes that pass through the Hall element H.
[0039] In the non-shielding state, the first and second magnetic
paths L1 and L2 that lead the magnetic fluxes generated by the N
pole of the magnet M to the S pole are formed and the Hall element
H is provided in one magnetic path, that is, the first magnetic
path L1. Therefore, it is possible to easily secure the required
number of magnetic fluxes for driving the Hall element H. As a
result, it is possible to detect that the magnetism shielding means
18 is not interposed between the magnet M and the Hall element H,
that is, that the seat 1 is not located at its foremost position
without deteriorating the sensitivity of the Hall element H.
[0040] In the shielding state, since it is possible to make the
number of magnetic fluxes that pass through the Hall element H
almost zero, it is possible to detect when the magnetism shielding
means 18 is interposed between the magnet M and the Hall element H
and when the seat 1 is located at its foremost position. Therefore,
it is possible to prevent injuries due to the large and sudden
expansion of an air bag by setting the speed at which the air bag
of the air bag device expands to be low.
[0041] According to the above-mentioned simple structure, it is
possible to correctly detect whether the seat 1 is located at its
foremost position, to effectively ensure a small number of
generated magnetic fluxes of the magnet M, and to reduce the loss
of the magnetic fluxes. Therefore, it is not necessary to use a
costly rare earth magnet. Further, since the external surface of
the case 21 is covered with the seat-moving mechanism 10 made of a
magnetic material, it is possible to prevent the demagnetization of
the magnet M at an early stage. Therefore, it is possible to
provide a magnetic switch capable of normally detecting the
position of a seat for a long period of time.
[0042] Further, since it is possible to provide the magnetism
detecting means 20 and the magnetism shielding means 18 inside the
seat-moving mechanism 10 (the stationary rail 13 and the movable
rail 14) made of a magnetic material, it is possible to make a
magnetic switch that is hardly affected by an external magnetic
field and to prevent the magnetic switch from erroneously
operating.
[0043] Moreover, since the magnetism detecting means 20 and the
magnetism shielding means 18 are not exposed to the outside of the
seat-moving mechanism 10, it is possible to prevent metal pieces in
the dust from entering the gap G and to prevent the magnetic switch
from erroneously operating. Furthermore, since the magnetism
detecting means 20 and the magnetism shielding means 18 are receive
in the seat-moving mechanism 10 and do not protrude to the outside
unlike in the conventional technology, the magnetism detecting
means 20 and the magnetism shielding means 18 do not serve as
obstacles.
[0044] As mentioned above, the magnetism detecting means 20 is
provided in the movable rail 14 and the magnetism shielding means
18 is provided in the stationary rail 13. However, on the contrary,
the magnetism detecting means 20 may be provided in the stationary
rail 13, and the magnetism shielding means 18 may be provided in
the movable rail 14.
[0045] The magnetism shielding means 18 is provided at the front
position. However, on the contrary, the magnetism shielding means
18 may be longitudinally provided at any position other than the
front position in the form of a wall and nothing may be provided at
the front position. In this case, the polarities of the output of
the Hall element H in the non-shielding state and in the shielding
state are reversed. That is, the output of the Hall element H is in
the OFF state in the non-shielding state, and is in the ON state in
the shielding state.
[0046] FIG. 5 illustrates another embodiment of the magnetic
switch. FIG. 5A is a side view illustrating a two-wheeled vehicle.
FIG. 5B is an enlarged side view illustrating a stand of the
two-wheeled vehicle.
[0047] As illustrated in FIGS. 5A and 5B, a stand 31 for supporting
the two-wheeled vehicle is provided in a two-wheeled vehicle 30
such as a bicycle or a motorcycle. As illustrated in FIG. 5B, the
stand 31 attached to the body frame 32 of the two-wheeled vehicle
30 can rotate between an upright state indicated by a solid line
and a horizontal state indicated by a dotted line. It is possible
to stop the two-wheeled vehicle 30 by making the stand 31 upright
and to travel with the two-wheeled vehicle 30 by making the stand
31 horizontal.
[0048] Magnetism shielding means 33 that protrudes to the direction
where the stand 31 rotates from the vertical state to the
horizontal state is integrated with the stand 31. The stand 31 and
the magnetism shielding means 33 are made of a magnetic material
such as iron.
[0049] Magnetism detecting means 40 is provided in the body frame
32. The structure of the magnetism detecting means 40 is almost the
same as that of the magnetism detecting means 20. That is, a pair
of facing pieces is mounted so as to face downward and a magnet and
a Hall element are provided in each facing piece so that a gap is
provided between the magnet and the Hall element. The magnet and
the Hall element are received in a resin case and the external
surface (excluding the portion that faces the facing pieces) is
covered with a magnetic material such as iron.
[0050] As indicated in FIG. 5B by a solid line, when the stand 31
is in the upright state, in the magnetism detecting means 40, a
magnetic path is formed. In the magnetic path, the magnetic fluxes
generated by the N pole that is one surface of the magnet pass
through the gap, the Hall element, and the inside of the case that
covers the external surface of the magnetism detecting means 40 and
reach the S pole, that is, the other surface of the magnet.
Therefore, it is possible to secure the number of magnetic
fluxes.
[0051] On the other hand, as illustrated in FIG. 5B, when the stand
31 is in the horizontal state, since the magnetism shielding means
33 of the stand 31 enters the gap G of the magnetism detecting
means 40, the magnetic path is shielded similarly to the case
illustrated in FIG. 4B. As a result, the number of magnetic fluxes
that pass through the Hall element becomes almost zero.
[0052] Therefore, it is possible to detect whether the stand 31 is
in the vertical or horizontal state by sensing the output of the
Hall element. When the stand 31 is in the vertical state, the
engine is not started. As a result, it is possible to prevent the
two-wheeled vehicle from traveling in a dangerous state where the
stand 31 erects.
[0053] As mentioned above, since it is possible to sense the state
of the stand 31 by non-contact sensing means, the sensing means
hardly breaks down or erroneously operates. Further, since it is
possible to prevent demagnetization of the magnet by covering the
external surface of the magnetism detecting means 40 with a case
made of a magnetic material, it is possible to sense the state of
the stand 31 for a long period of time.
[0054] The magnetism detecting means may be provided in the stand,
and the magnetism shielding means may be provided in the body
frame.
[0055] As mentioned above, according to the present invention,
since it is possible to secure the number of magnetic fluxes that
pass through the Hall element, the sensitivity of the Hall element
does not necessarily deteriorate. Therefore, it is not necessary to
use a rare earth magnet having a large number of generated magnetic
fluxes and a cheap magnetic switch may be provided. Further, since
the magnetism detecting means is covered with the magnetic
material, it is possible to make a magnetic switch that is hardly
affected by the external magnetic field.
* * * * *