U.S. patent application number 10/823723 was filed with the patent office on 2004-12-16 for seat position detection device.
Invention is credited to Endo, Hirofumi, Suzuki, Takashi, Tagawa, Satoru, Yasuda, Keiji.
Application Number | 20040251723 10/823723 |
Document ID | / |
Family ID | 33469978 |
Filed Date | 2004-12-16 |
United States Patent
Application |
20040251723 |
Kind Code |
A1 |
Endo, Hirofumi ; et
al. |
December 16, 2004 |
Seat position detection device
Abstract
A seat position detection device includes a detection means for
detecting physical relationship between a stationary rail supported
by a vehicle body and a movable rail rigidly connecting a seat and
sliding along the stationary rail wherein the detection means
includes a magnetic body provided at one of the stationary rail and
the movable rail and a magnetic sensor provided at the other of the
stationary rail and the movable rail, and the magnetic body is
arranged at an entire length of a specified region in sliding
direction of the movable rail, and a magnetic pole thereof is
directed perpendicular to the slide direction, and the magnetic
sensor outputs a signal in response to magnetism from the magnetic
body.
Inventors: |
Endo, Hirofumi; (Toyota-shi,
JP) ; Suzuki, Takashi; (Obu-shi, JP) ; Tagawa,
Satoru; (Takahama-shi, JP) ; Yasuda, Keiji;
(Handa-shi, JP) |
Correspondence
Address: |
REED SMITH LLP
Suite 1400
3110 Fairview Park Drive
Falls Church
VA
22042
US
|
Family ID: |
33469978 |
Appl. No.: |
10/823723 |
Filed: |
April 14, 2004 |
Current U.S.
Class: |
297/284.1 ;
297/284.3 |
Current CPC
Class: |
B60N 2/0715 20130101;
B60N 2/071 20130101; B60N 2002/0268 20130101; B60N 2002/0272
20130101 |
Class at
Publication: |
297/284.1 ;
297/284.3 |
International
Class: |
A47C 003/025 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 14, 2003 |
JP |
2003-108550 |
Claims
What we claim is:
1. A seat position detection device comprising; a detection means
for detecting physical relationship between a stationary rail
supported by a vehicle body and a movable rail rigidly connecting a
seat and sliding along the stationary rail; the detection means
includes a magnetic body provided at one of the stationary rail and
the movable rail and a magnetic sensor provided at the other of the
stationary rail and the movable rail, and the magnetic body is
arranged at an entire length of a specified region in sliding
direction of the movable rail, and a magnetic pole thereof is
directed perpendicular to the slide direction, and the magnetic
sensor outputs a signal in response to magnetism from the magnetic
body.
2. A seat position detection device according to claim 1, wherein a
sliding range of the seat is divided into two regions, and the
magnetic body is attached to one of the divided region so that the
magnetic sensor faces to one of the N pole and the S pole
thereof.
3. A seat position detection device according to claim 1, wherein
the sliding range of the seat is divided into two regions, and the
magnetic body includes two portions which are attached to one of
the divided portion so that the magnetic sensor faces to one of the
N pole and the S pole thereof, respectively.
4. A seat position detection device according to claim 1, wherein
the magnetic body is not exposed outside of the fixed rail or
movable rail.
5. A seat position detection device according to claim 1, wherein
the magnetic body is shaped as a sheet.
6. A seat position detection device according to claim 1, wherein
the magnetic body is attached to one of the stationary rail and the
movable rail by magnetic attraction.
7. A seat position detection device according to claim 1, wherein
the magnetic sensor includes a Hall element for outputting a signal
according to magnetic flux density and a switching circuit for
outputting a signal when a voltage level of the signal from the
Hall element exceeds a predetermined value.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
U.S.C. .sctn.119 with respect to a Japanese Patent Application
2003-108550, filed on Apr. 14, 2003, the entire content of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention generally relates to a seat position
detection device. More particularly, the present invention pertains
to a seat position detection device detecting physical relationship
between a stationary rail and a movable rail.
BACKGROUND OF THE INVENTION
[0003] An example of the seat position detection device is
disclosed in U.S. Pat. No. 6,053,529. In this patent, a magnetic
sensor is mounted so as to extend from a stationary rail mounted to
a vehicle floor. The L-shaped sensor flange is attached upside down
with a horizontal leg attached on a first end to the flange side of
a movable rail attached in a slidable relationship with a
stationary rail and on a second end attached to a downturn leg.
Accordingly, the seat position is judged whether or not the
downturn leg of the sensor flange is placed between the magnetic
sensor and the magnetic body.
[0004] Another example of the seat position detection device is
disclosed in Japanese Patent Laid-Open Publication No. 2003-19051.
This seat position sensor also includes a magnetic sensor supported
by a movable rail, a magnetic body supported by the movable rail as
opposed to the magnetic sensor, and a flange provided between the
magnetic sensor and the magnetic body. The L-shaped sensor flange
is made of a plate-like magnetic body such as a steel plate, and
adapted to underneath of a stationary rail. Namely, one plane of
the flange is attached to the stationary rail, and the other plane
thereof is located perpendicular to a floor. The seat position is
judged whether or not the sensor flange is placed between the
magnetic sensor and the magnetic body.
[0005] In these two documents, the seat position detecting device
can be took place without contacting in the detection system since
a Hall element detects a change of the magnetic flux density
generated from the magnet. However, a shielding member (the sensor
flange or the flange) is provided such as a vertical wall in
parallel with the stationary rail and the movable rail, and the
shielding member is provided between the magnet and the Hall
element. Thus, relatively large space is required to arrange the
detection system.
[0006] In addition, another example of the seat position detection
device is disclosed in Japanese Patent Laid-Open Publication No.
2002-200933. In this seat position sensor, sensor member is
provided at a movable rail and includes a magnet and a Hall effect
IC (magnetic sensor) accommodated in a case with L-shaped cross
section. In this art, when the stationary rail is placed close to
the sensor, the Hall effect IC can not detect a magnetic flux since
the stationary rail intercepts the magnetic flux generated from the
magnet. On the other hand, when the stationary rail is not close to
lower rail by moving a seat to foreside, the Hall effect IC can
detect a magnetic flux generated from the magnet.
[0007] The shielding member is not needed in this configuration. In
this point, number of component may be reduced, and arrangement
space may be reduced for the detection system. Although, if a
magnet chip is accidentally adhered to the stationary rail, the
Hall effect IC may be detect the magnetic flux generated at the
magnet chip.
[0008] In addition, another example of the seat position detection
device is disclosed in U.S. Pat. No. 4,909,560. This seat position
sensor is applied in which the seat is movable along the slide
direction using a driving force, and magnetism is used to estimate
the seat position. In this art, a Hall effect IC (magnetic sensor)
is mounted to a slide (movable rail), and a magnetic strip
positioned close to the Hall effect IC is supported by track. The
magnetic strip has a series of magnet poles of alternated polarity.
Therefore, as a gear box including the Hall effect IC is moved
backward and forward, the Hall effect IC passes in close proximity
to each of the poles in the magnetic strip and switches its output
transistor off and on as the IC passes the alternating north an
south poles in the magnet strip. A square wave generated by the
Hall effect IC can be counted by a control module to provide the
position data of the seat.
[0009] In this art, the seat position detecting device detects the
seat position precisely. However, a control module is needed to
judge the seat position by processing signals transmitted from the
Hall effect IC. The control module counts signals transmitted from
the Hall effect IC in response to seat movement, and memorizes the
seat position. To memorize the seat position even when the main
power is turned off, such as a semiconductor memory (for example,
EEPROM (Electronically Erasable and Programmable Read Only Memory))
for saving the seat position data or a back up electric power
supply are required. It makes the system complicated.
SUMMARY OF THE INVENTION
[0010] In light of foregoing, according to an aspect of the present
invention, a seat position detection device includes a detection
means for detecting physical relationship between a stationary rail
supported by a vehicle body and a movable rail rigidly connecting a
seat and sliding along the stationary rail wherein the detection
means includes a magnetic body provided at one of the stationary
rail and the movable rail and a magnetic sensor provided at the
other of the stationary rail and the movable rail, and the magnetic
body is arranged at an entire length of a specified region in
sliding direction of the movable rail, and a magnetic pole thereof
is directed perpendicular to the slide direction, and the magnetic
sensor outputs a signal in response to magnetism from the magnetic
body.
[0011] It is preferable that a sliding range of the seat is divided
into two regions, and the magnetic body is attached to one of the
divided region so that the magnetic sensor faces to one of the N
pole and the S pole thereof.
[0012] It is still further preferable that the sliding range of the
seat is divided into two regions, and the magnetic body includes
two portions which are attached to one of the divided portion so
that the magnetic sensor faces to one of the N pole and the S pole
thereof, respectively.
[0013] It is still further preferable that the magnetic body is not
exposed outside of the fixed rail or movable rail.
[0014] It is still further preferable that the magnetic body is
shaped as a sheet.
[0015] It is still further preferable that the magnetic body is
attached to one of the stationary rail and the movable rail by
magnetic attraction.
[0016] It is still further preferable that the magnetic sensor
includes a Hall element for outputting a signal according to
magnetic flux density and a switching circuit for outputting a
signal when a voltage level of the signal from the Hall element
exceeds a predetermined value.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0017] The foregoing and additional features and characteristics of
the present invention will become more apparent from the following
detailed description considered with reference to the accompanying
drawing figures wherein:
[0018] FIG. 1 is a side view schematically illustrating a physical
arrangement including a seat, a steering wheel, and a magnetic
sensor according to a first embodiment of the present
invention;
[0019] FIG. 2 is a block circuit diagram illustrating controlling
system according to a first embodiment of the present
invention;
[0020] FIG. 3 is a cross sectional view schematically illustrating
a position of a Hall effect IC according to a first embodiment of
the present invention;
[0021] FIG. 4 is a side view schematically illustrating a magnetic
state generated from a magnet according to a first embodiment of
the present invention;
[0022] FIG. 5 is a side view schematically illustrating physical
arrangement of a magnet and a Hall effect IC as moving a movable
rail according to a first embodiment of the present invention;
[0023] FIG. 6 is a side view schematically illustrating physical
arrangement of a magnet and a magnetic sensor according to a second
embodiment of the present invention;
[0024] FIG. 7 is a chart indicating detection signal and output of
a Hall element according to a second embodiment of the present
invention;
[0025] FIG. 8 is a side view schematically illustrating physical
arrangement of a magnet and a Hall effect IC according to a third
embodiment of the present invention;
[0026] FIG. 9 is a cross sectional view schematically illustrating
physical arrangement of a magnet and a Hall effect IC according to
a fourth embodiment of the present invention; and
[0027] FIG. 10 is a cross sectional view schematically illustrating
physical arrangement of a magnet and a Hall effect IC according to
a fifth embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] A preferred embodiment of the present invention will be
described herein below in detail with reference to the accompanying
drawings.
[0029] A first embodiment of the present invention is explained
referring to FIGS. 1 to 5.
[0030] As shown in FIG. 1, a seat 1 is provided in a vehicle body
A, and a steering wheel 2 is provided in front of the seat 1. The
seat 1 is supported on a floor 3 by a seat position adjusting
mechanism B to adjust, seat position backward and forward. The
steering wheel 2 has an airbag device built-in.
[0031] A controlling system for operating the airbag is shown in
FIG. 2. In the controlling system, signals from a speed sensor 6, a
gravity sensor 7 and a Hall effect IC 8 (an example of magnetic
sensor Se) are inputted to a control unit 5 (ECU), and the control
unit 5 outputs a control signal into the airbag device 4.
[0032] The speed sensor 6 is a generic designation of detecting
system that estimate traveling speed of the vehicle body A
according to condition of an accelerator, revolution speed of an
engine, and condition of a transmission. The gravity sensor 7
functions so as to estimate impact energy applied to the vehicle
body A, and then to output the impact energy as an electric signal.
The Hall effect IC 8 functions so as to output a signal for judging
the seat 1 location according to the magnetic intensity (magnetic
flux density) generate from a magnet (magnetic body) M as described
later. The airbag device 4 includes one airbag and two gas
generation members to generate different gas amount each other. A
signal path for operating each gas generation member is formed
between the control unit 5 and both gas generation members.
[0033] The seat 1 includes a seat cushion 1A and a seat back 1B.
The seat sliding range by the seat position adjusting mechanism B
is divided into two regions at a control point P. For example, a
first region provided in front side of the control point P is
determined to as an unrestricted area X. On the other hand, a
second region provided in backside of the control point P is
determined to as a restricted area Y. The physical arrangement of
the Hall effect IC 8 and the magnet M is set to that the Hall
effect IC 8 outputs a detection signal while the seat 1 is located
in the unrestricted area X. And also the Hall effect IC 8 does not
output the detection signal while the seat 1 is located in the
restricted area Y. Although the unrestricted area X and the
restricted area Y have been indicated as almost same length as
shown in FIG. 1, the ratio between them are not limited to this
configuration as shown in FIG. 1.
[0034] The control unit 5 includes a microprocessor, and judges
expansion level of the airbag depending on the seat position. When
the airbag device 4 is worked in the case of that the Hall effect
IC 8 judges that the seat 1 is in the unrestricted area X, the
control unit 5 runs a process in which the airbag expands larger
than the case of that the Hall effect IC 8 judges that the seat 1
is in the restricted area Y.
[0035] The Hall effect IC 8 (an example of the magnetic sensor Se)
accommodates a Hall element and a switching circuit as a unit. The
Hall element outputs a voltage signal according to magnetic flux
density with a polarity according to direction of magnetic flux
generated from the magnet M. The switching circuit outputs a
detection signal when the voltage from the Hall element exceeds a
predetermined threshold level, and does not output a detection
signal (or output connector outputs low voltage) when the voltage
from the Hall element does not exceed a predetermined threshold
level regardless of polarity of the voltage.
[0036] Simply, a Hall element or a MR element may be used as a
magnetic sensor Se without using the Hall effect IC. In this case,
a processing circuit is used to process a signal from the Hall
element or the MR element in reference to the predetermined
threshold.
[0037] The feature of the seat position detection device according
to the first embodiment of the present invention is that the
magnetic detection means includes the Hall effect IC 8 and the
magnet M to act the magnetism to the Hall effect IC 8, and a
detection apparatus includes the detection mean and a member
supporting them.
[0038] A pair of stationary rails 10 is fixed to the floor 3 of the
vehicle A through the intermediary of a bracket 11 provided at both
front end and rear end of each stationary rail 10. A pair of
movable rails 12 is attached to each stationary rail 10 with
slidable relationship, and supports the seat 1. As shown in FIG. 3
and FIG. 5, stationary rails 10 are formed by bending of a steel
plate (an example of magnetic material) to form a bottom portion
10a provided as horizontal posture, a pair of vertical wall
portions 10b horizontally folded into upward at both sides of the
bottom portion 10a, a pair of upper portions 10c horizontally
folded to inward side at upper end of vertical wall portions 10b,
and a pair of folding ends 10d folded into downward at the other
end of upper portions 10c. Accordingly, an opening portion is
formed between both folding ends 10d.
[0039] The movable rail 12 is also formed using steel plates (which
is an example of magnetic material) formed including a vertical
wall portion 12a lapped and jointed two steel plates by spot
welding and so on, bottom portions 12b formed by bending lower ends
of a pair of wall portions 12a to opposite direction each other,
and folding ends 12c folded to upward at the other end of each
bottom portion 12b. The movable rail 12 is inserted to inferior of
the stationary rail 10, and plurality of free rotating rollers 13
are provided between the bottom portion 10a of the stationary rail
10 and the bottom portion 12b of the movable rail 12. Thus, the
movable rail 12 is slidably supported along longitudinal direction
of the stationary rail 10.
[0040] The seat position adjusting mechanism B is constructed as
explained below. Plurality of hollow portions (not shown) is formed
with a predetermined interval along longitudinal direction of the
stationary rail 10. A lock member for engaging to one of the hollow
portions is attached to the movable rail 12 with biasing to the
engaging direction thereof by a spring. A handle 15 (see FIG. 1) is
provided at front side of the movable rail 12 to operate engagement
or disengagement between the lock member and one of the hollow
portions. Accordingly, an operator can operate the handle 15 to
release the locking condition of the seat position adjusting
mechanism B and move the seat 1 in the longitudinal direction of
the movable rail 12 (or stationary rail 11). Then, the operator can
lock the seat position adjusting mechanism B by releasing the
operation of the handle 15. In this time, the lock member is
engaged with one of the hollow portions, and physical relationship
between the stationary rail 10 and the movable rail 12 can be
adjusted within predetermined interval.
[0041] The sheet type magnet M is provided to the top face of the
upper portion 10c for one of the stationary rail 10. The magnet M
is made of a flexible material including magnetized material
(namely rubber type magnet), and single pole with N pole or S pole
is formed on one side of the sheet type magnet M. The length of the
magnet M attached to the stationary rail 10 corresponds to the
unrestricted area X in the seat sliding range. As fastener means to
attach the magnet M to the top face of the upper portion 10c, an
adhesive material, a screw, a rivet and the like may be used. In
addition, the magnet M may be attached to the stationary rail 10 by
its own magnetic attraction. For example, the magnet may be
attached to the stationary rail 10 wherein a convex portion formed
at under surface of the magnet M is inserted to a concave portion
formed on the stationary rail 10.
[0042] The Hall effect IC 8 is attached to the wall portion 12a for
one of the movable rail 12, which corresponds to the stationary
rail 10 attaching the magnet M. The Hall effect IC 8 is located
upward of the magnet M to separate from the magnet M with a
distance (height) D, and to overlap with the magnet M in plane view
when the seat 1 is located in the unrestricted area X.
[0043] Although sensitivity of the Hall effect IC 8 to detect the
magnet M is higher in narrower distance between them (distance D
shown in FIG. 3), the distance D may be set to few millimeter in
consideration of power supplying to the Hall effect IC 8 and
arrangement of a cable 8a to the wall portion 12a to transmit a
detection signal. A protection cover, which is made of nonmagnetic
material (for example, aluminum plate, cupper plate, resin plate
and so on), may be provided at the wall portion 12a to cover the
Hall effect IC 8.
[0044] As mentioned above, since the magnet M is provided at the
stationary rail 10 made of magnetic material, the magnetic flux
generated at lower surface side of the magnet M is conducted to a
magnetic circuit composed of the stationary rail 10 as shown in
FIG. 4. Accordingly, the magnetic flux is conducted to upper
surface side of the magnet M with inhibiting the magnetic flux
leakage to downward of the stationary rail. Then, magnetic flux
density above the magnet M may be elevated, and detection
sensitivity by the Hall effect IC 8 may become high. In addition,
when a detection point of the Hall effect IC 8 is placed in front
of the front end of the stationary rail 10 at seat 1 position
adjusting, the magnetic flux generated from the magnet M may not
affect the Hall effect IC 8 since front end of the magnet M and
front end of the stationary rail 10 is approximately matched.
[0045] To utilize the function of the stationary rail 10 and the
magnet M, the dimension of the magnet M in the back-and-forth
direction is set to approximately match the dimension of the
unrestricted area X as described above. Accordingly, the detection
point of the Hall effect IC 8 is set to approximately match to the
front end of the stationary rail 10 if location of the seat 1 is
set to the control point P.
[0046] According to the configuration of the first embodiment, as
shown in FIG. 5(a), if the location of the seat 1 is placed in the
unrestricted area X, the Hall effect IC 8 detects the magnetism
generated from the magnet M and outputs the detection signal since
the Hall effect IC 8 is located above the magnet M. Accordingly, as
shown in FIG. 5(b), if the location of the seat 1 is set in the
restricted area Y, the Hall effect IC 8 may not output the
detection signal since the Hall effect IC 8 may not detect the
magnetism generated from the magnet M. For example, if the seat 1
is moved from the unrestricted area X to the restricted area Y,
these two areas are accurately identified with a boundary (control
point P) since the magnetic flux acting to the Hall effect IC 8
density is drastically changed when the Hall effect IC 8 passes the
control point. The Hall effect IC 8 outputs the detection signal if
the magnetic flux density detected by the Hall effect IC 8 exceeds
a set value without reference to either N pole or S pole. Thus, for
example, if a magnet chip is accidentally adhered to the upper
surface of the stationary rail 10, the Hall effect IC 8 may detect
without mistake, and the position of the seat 1 may be identified
preventing mistake.
[0047] A second embodiment of the present invention is explained
referring to FIGS. 6, 7. (In the second embodiment, common numbers
and symbols are used for parts having same functions with the first
embodiment.)
[0048] In the second embodiment, configuration of the seat position
detection device is changed from the first embodiment thereof.
Configuration of the seat position adjusting mechanism B for
supporting the seat 1 and control system operating the airbag
device 4 is basically same as the first embodiment thereof.
[0049] Namely, as shown in FIG. 6, two magnets M, M are attached to
upper surface of the upper portion 10c of the stationary rail 10 on
either side of the control point. Magnets M, M are made of flexible
material (namely rubber type magnet) with belt like shape and are
placed according to the unrestricted area X and restricted area Y,
respectively. One of the magnets M is attached to the stationary
rail 10 at a corresponding position to the unrestricted area X
wherein the upper surface acts as S pole. The other of the magnets
M is attached to the stationary rail 10 at a corresponding position
to the restricted area Y wherein the upper surface acts as N pole.
The Hall effect IC 8 (magnetic sensor Se) is placed above each
magnet M, M whole the adjusting range of the seat 1.
[0050] Although it is not shown in the figure, a unit of a Hall
element and a switching circuit may be used as the magnetic sensor
Se. In this configuration, for example, the Hall element outputs a
voltage signal according to magnetic flux density with a polarity
according to direction of magnetic flux generated from the magnet
M. The switching circuit outputs a detection signal from one
terminal when the positive voltage from the Hall element exceeds a
predetermined threshold level, and outputs a detection signal from
the other terminal when the negative voltage from the Hall element
exceeds a predetermined threshold level. In addition, another
configuration of the magnetic sensor Se may be used wherein the
magnetic sensor Se outputs a signal having a current value
corresponding to one of Hi or Lo as a detection result of the Hall
element.
[0051] According to the configuration of the second embodiment, for
example, if the seat 1 is moved from the unrestricted area X to the
restricted area Y, polarity of a voltage signal outputted from the
Hall element changes from positive voltage to negative voltage on
the basis of zero voltage, as shown in FIG. 7. The Hall element
outputs the detection signal from one of the terminals
corresponding to either the restricted area Y or unrestricted area
X if the magnetic flux density detected by the Hall element exceeds
a set value. Namely, if the location of the seat 1 is placed in the
restricted area Y, the Hall element outputs the detection signal
(Y) from one terminal. Accordingly, if the location of the seat 1
is placed in the unrestricted area X, the Hall element may output
the detection signal (X) from the other terminal. Then, position of
the seat 1 may be identified preventing mistake since the Hall
effect IC 8 can receive high magnetic flux density whole adjusting
range of the seat 1 position.
[0052] In particular, if a magnet chip is accidentally adhered to
the upper surface of the magnet M, the polarity at upper surface of
the magnet chip (facing the magnetic sensor Se) becomes same
polarity as upper surface of the magnet M (facing the magnetic
sensor Se). Then, effect of adhered magnet chip may be prevented,
and detection of the seat 1 position may be identified preventing
mistake.
[0053] In addition to above mentioned embodiments of the present
invention, for example, embodiments explained below may be
constructed. (In the second embodiment, common numbers and symbols
are used for parts having same functions with the first
embodiment.)
[0054] (A Third Embodiment)
[0055] In the third embodiment, the magnet M may be arranged to
face at least two poles on upper surface along the unrestricted
area X. For example, as shown in FIG. 8 both magnets M, M facing N
pole and S pole at upper surface are adjacently arranged in the
unrestricted area X on the stationary rail in the third embodiment.
The Hall effect IC 8 is composed as same as the first embodiment
thereof. Thus, any other combination of polarity of the magnet may
be arranged since the Hall effect IC outputs a detection signal if
the magnetic flux density is high regardless of polarity of the
magnet M.
[0056] (A Forth Embodiment)
[0057] As shown in FIG. 9, the magnet M may be attached to the
vertical wall portion 12a of the movable rail 12, and the Hall
effect IC 8 may be provided at the stationary rail 10. By
supporting the Hall effect IC 8 to the fixed portion (stationary
rail), the cable conducted from the Hall effect IC can be fixed to
the fixed portion. Thus, there is no need to use flexible material
for the cable 8a such as spiral type, and it may reduce cost for
production and may improve reliability in use.
[0058] (A Fifth Embodiment)
[0059] In the fifth embodiment, a relative displacement system
including the magnet M and the Hall effect IC 8 is provided in the
stationary rail 10. More particularly, as shown in FIG. 10, the
magnet M is attached to the folding end 12c of the movable rail,
and the Hall effect IC 8 is provided at a nearby site of the magnet
M and on the vertical wall portion 10b of the stationary rail 10 in
which the Hall effect IC 8 is partially accommodated in the
vertical wall portion 10b (whole the Hall effect IC 8 may be
accommodated in the vertical wall portion 10b). In this manner,
according to accommodate the magnet M and the Hall effect IC 8 to
interior space of the stationary rail 10, the surface of the magnet
M and the detector plane of the Hall effect IC 8 may be maintained
to unpolluted state since adherence of dust is prevented to the
surface of the magnet M and the detector plane of the Hall effect
IC 8. In other wards, the magnet M and the Hall effect IC 8 are
protected. In particular, to arrange the magnet m and the Hall
effect IC 8 in interior space of the stationary rail 10, the magnet
M may be provided at the side of the stationary rail 10, and the
Hall effect IC 8 may be provided at the side of the movable rail 12
in addition to the arrangement shown in the FIG. 10.
[0060] The principles, a preferred embodiment and mode of operation
of the present invention have been described in the foregoing
specification. However, the invention which is intended to be
protected is not to be construed as limited to the particular
embodiment disclosed. Further, the embodiment described herein is
to be regarded as illustrative rather than restrictive. Variations
and changes may be made by others, and equivalents employed,
without departing from the spirit of the present invention.
Accordingly, it is expressly intended that all such variations,
changes and equivalents which fall within the spirit and scope of
the present invention as defined in the claims, be embraced
thereby.
* * * * *