U.S. patent application number 11/647204 was filed with the patent office on 2007-08-09 for vehicle seat load detection device.
Invention is credited to Makoto Ono, Wataru Sakuma.
Application Number | 20070182226 11/647204 |
Document ID | / |
Family ID | 38333317 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070182226 |
Kind Code |
A1 |
Sakuma; Wataru ; et
al. |
August 9, 2007 |
Vehicle seat load detection device
Abstract
A magnet is attached to springs of a sheet cushion. A connecting
member is attached to side portions of a seat cushion frame. A
magnetic sensor having a magnetic impedance element is fixed on the
connecting member while being positioned right below the magnet. By
seating of an occupant on the seat cushion, springs are downwardly
bent to bring the magnet closer to the magnetic sensor and to
thereby change the magnetic field of the magnet detected with the
magnetic sensor. The load applied by an occupant to the seat
cushion is detected on the basis of the change of the magnetic
field.
Inventors: |
Sakuma; Wataru; (Nagoya-shi,
JP) ; Ono; Makoto; (Kariya-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W., SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
38333317 |
Appl. No.: |
11/647204 |
Filed: |
December 29, 2006 |
Current U.S.
Class: |
297/217.3 |
Current CPC
Class: |
B60N 2/7094 20130101;
B60N 2/002 20130101; A47C 31/00 20130101 |
Class at
Publication: |
297/217.3 |
International
Class: |
A47C 31/00 20060101
A47C031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 7, 2006 |
JP |
2006-030201 |
Claims
1. A vehicle seat load detection device for detecting a load
applied to a vehicle seat having a non-bendable fixed member
irrespective of the existence/nonexistence of the load and a
flexible member displaceable relative to the fixed member by being
bent under the applied load, through the amount of bending of the
flexible member, the vehicle seat load detection device comprising:
a magnetism generator which generates a magnetic field provided on
one side of the fixed member and the flexible member, and a
magnetic sensor having a magnetic impedance element provided on the
other side to detect the magnetic field generated by the magnetism
generator, wherein the flexible member is bent by an amount
corresponding to the load applied to the vehicle seat to change the
distance between the magnetism generator and the magnetic sensor
and to thereby change the magnetic field generated by the magnetism
generator, and the load applied to the vehicle seat is detected on
the basis of the detected change of the magnetic field.
2. The vehicle seat load detection device according to claim 1,
wherein the magnetic sensor is attached to the fixed member.
3. The vehicle seat load detection device according to claim 2,
wherein the vehicle seat has a seat cushion to be sat on by an
occupant; the flexible member comprises a plurality of spring
members downwardly bendable by sitting on the seat cushion; the
fixed member comprises a sheet frame for fixing the end portion of
the spring members; a supporting member for supporting the
magnetism generator is provided on the plurality of the spring
members; a connecting member is stretched below the supporting
member between two side portions of the seat frame facing each
other so as to be opposed to the supporting member through a
predetermined distance; the magnetic sensor is fixed on the
connecting member; and the supporting member is downwardly bent
together with the plurality of the spring members by seating on the
vehicle seat to bring the magnetism generator closer to the
magnetic sensor.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from Japanese Patent
Application No. 2006-030201 filed Feb. 7, 2006. The entire content
of this priority application is incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present invention relates to a vehicle seat load
detection device for detecting a load applied to a vehicle
seat.
BACKGROUND
[0003] There has been a need to determine the
existence/nonexistence of an object on a vehicle seat by detecting
a load applied from an occupant to the vehicle seat in order to
control the operation of an airbag according to the
existence/nonexistence of an occupant and the size of the physical
constitution of the occupant. Springs which are bendable members
incorporated in the seat cushion of the vehicle seat are ordinarily
displaced by several ten millimeters by bending caused by seating.
Accordingly, detection of the load applied from an occupant to the
vehicle seat on the basis of the displacement of the bendable
members incorporated in the vehicle seat essentially requires using
a sensor capable of detecting the amount of relative displacement
through several ten millimeters between the bendable members and a
fixed member. If this detection is realized by means of a
conventional displacement sensor such as a magnetic sensor in a
simple manner, it is necessary to use a considerably large
magnetism generator or dispose a plurality of sensors for
measurement of the displacement in one place. A device including
such a generator or sensors cannot be mounted in the vehicle
seat.
[0004] A conventional art provided to solve this problem is known,
which relates to a load detection device for detecting a load
applied to a vehicle seat by converting the amount of bending of a
seat cushion caused by seating into a minuscule displacement by
means of a converting member, and by detecting this minuscule
displacement with a strain gauge (see, for example, Japanese Patent
Laid-Open No. 2005-49272, pp. 4-6, FIGS. 1 through 6, and a
published Japanese translation of a PCT application No.
2001-512573, pp. 7-8, FIG. 3).
[0005] In the above-described conventional art, however, there is a
need to use a special displacement amount converting member
connected to a spring member in the vehicle seat for the purpose of
converting a displacement of the spring member by seating into a
minuscule displacement, resulting in an increase in the number of
components and an increase in manufacturing cost.
SUMMARY
[0006] In view of the above-described circumstances, an object of
the present invention is to provide a low-cost vehicle seat load
detection device having a reduced number of component parts.
[0007] In a vehicle seat load detection device according to the
present invention, a flexible member is bent by an amount
corresponding to a load applied to a vehicle seat to change the
distance between a magnetism generator and a magnetic sensor having
a magnetic impedance element and to thereby change a magnetic field
generated by the magnetism generator, and the load applied to the
vehicle seat is detected on the basis of the detected change of the
magnetic field.
[0008] The magnetic sensor having a magnetic impedance element has
high magnetic sensitivity and is capable of detecting the
displacement of the magnetism generator positioned at a distance of
several ten millimeters therefrom by detecting the change of the
magnetic field. Therefore, the vehicle seat load detection device
of the present invention is capable of directly detecting the load
applied to the vehicle seat from the amount of bending of the
flexible member without using any special displacement amount
converting member or the like.
[0009] According to illustrative aspects of the present invention,
arrangements described below are preferred.
[0010] (1) The magnetic sensor is attached to a fixed member to
ensure that the magnetic sensor to which a harness, an electronic
circuit or other components are connected is not moved by
occupant's seating or the like, and that the durability of the
electrical connection therebetween can be improved. Also, the
facility with which furnishing with the harness connected to the
magnetic sensor is performed is improved and the facility with
which the magnetic sensor is attached to the vehicle seat is also
improved.
[0011] (2) A supporting member for supporting the magnetism
generator is provided on a plurality of spring members; a
connecting member is stretched below the supporting member between
two side portions of a seat frame facing each other so as to be
opposed to the supporting member through a predetermined distance;
the magnetic sensor is fixed on the connecting member; and the
supporting member is downwardly bent together with the plurality of
spring members by seating on the vehicle seat to bring the
magnetism generator closer to the magnetic sensor. Thus, the
distance between the magnetism generator and the magnetic sensor is
changed by bending of the plurality of spring members to enable the
load applied to the vehicle seat to be detected with improved
accuracy.
[0012] The vehicle seat load detection device of the present
invention is capable of directly detecting the load applied to the
vehicle seat from the amount of bending of the flexible member.
Therefore there is no need to provide any special displacement
amount converting member or the like. Thus, the number of component
parts of the vehicle seat load detection device can be reduced and
the vehicle seat load detection device can be easily manufactured
at a reduced cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a perspective view of a vehicle seat in an
illustrative aspect of the present invention;
[0014] FIG. 2 is a perspective view of a state in which a
cushioning material is removed from the vehicle seat shown in FIG.
1;
[0015] FIG. 3 is a sectional view taken along line A-A in FIG.
2;
[0016] FIG. 4 is an enlarged view of a portion shown in FIG. 3;
[0017] FIG. 5 is a diagram schematically showing the vehicle seat
load detection device in the illustrative aspect of the present
invention;
[0018] FIG. 6 is a sectional view showing a state in which the
spring shown in FIG. 3 is bent;
[0019] FIG. 7 is a graph showing the relationship between the
amount of bending of the springs and the output voltage from the
magnetic sensor;
[0020] FIG. 8 is a diagram schematically showing an example of
modification of the device in the illustrative aspect of the
present invention; and
[0021] FIG. 9 is a diagram schematically showing an example of
modification different from that shown in FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED ILLUSTRATIVE ASPECTS
[0022] Illustrative aspects of the present invention will be
described with reference to FIGS. 1 to 7.
[0023] A vehicle seat load detection device 5 according to an
illustrative aspect of the present invention is attached to a
vehicle seat 1. The vehicle seat 1 has a seat cushion 2 and a seat
back 3 (see FIG. 1). The seat cushion 2 is mounted on a floor panel
(not shown) of a vehicle by means of lower rails 4. The seat back 3
is mounted on the seat cushion 2. The seat back 3 can be turned
along the vehicle front-rear direction.
[0024] The seat cushion 2 on which an occupant sits has a seat
cushion frame 22 (corresponding to the fixed member and the seat
frame of the present invention). The seat cushion frame 22 supports
a cushioning material. The seat cushion frame 22 is fixed on upper
rails 21 movably engaging with the lower rails 4 (see FIG. 2). The
seat cushion frame 22 has left and right side portions 22a facing
each other. Rear ends of the side portions 22a are connected to
each other by a connecting shaft 23. Ends of a plurality of springs
24 (corresponding to the flexible member and the spring members of
the present invention) are respectively attached to a front side
portion 22b of the seat cushion frame 22 and the connecting shaft
23. Each of the plurality of springs 24 extends in the front-rear
direction. Each spring 24 is downwardly bent by a load applied
thereto, for example, when an occupant sits on the vehicle seat 1
and is, therefore, displaceable relative to the seat cushion frame
22 not bendable under any load.
[0025] The seat back 3 has a seat back frame 31 supporting a
cushioning material as in the case of the seat cushion 2. Ends of a
plurality of spring members 32 are attached to left and right side
portions of the seat back frame 31 (see FIG. 2).
[0026] The plurality of springs 24 of the seat cushion 2 are
connected to each other by a magnetism generator supporting member
51 (corresponding to the supporting member of the present
invention) constituting the vehicle seat load detection device 5 of
the present invention (see FIG. 3). The magnetism generator
supporting member 51 is a non-magnetizable material, e.g., a
nonferrous metal or a synthetic resin. The magnetism generator
supporting member 51 has a base 51a generally in the form of a
plate. Curled attachment portions 51b which can be attached to the
springs 24 with a certain degree of freedom are formed at opposite
ends of the base 51a. The attachment portions 51b of the magnetism
generator supporting member 51 formed at the opposite ends of the
base 51a are fitted around portions of the springs 24 located at
the side ends. Therefore the magnetism generator supporting member
51 engage with the plurality of springs 24.
[0027] A yoke 51c formed from a material having a high
permeability, e.g., a metal is incorporated in a central portion of
the base 51a. A plurality of supporting projections 51d extend
downward from the central portion of the base 51a. A magnet 52
(corresponding to the magnetism generator of the present invention)
is fitted between the supporting projections 51d. Claw portions
51d1 of the supporting projections 51d engage with the magnet 52 to
prevent the magnet 52 from coming off (see FIG. 4). The magnet 52
is a permanent magnet for generating a magnetic field and has a
cylindrical shape. The magnet 52 is supported on the base 51a so
that the magnetic poles are vertically oriented. The upper surface
of the magnet 52 abuts against the lower surface of the yoke 51c.
The magnet 52 is surrounded by the supporting projections 51d
extending downward.
[0028] A connecting member 22c in the form of a plate corresponding
to the fixed member of the present invention is stretched between
the side portions 22a of the seat cushion frame 22 facing each
other. The connecting member 22c is placed below the magnetism
generator supporting member 51 at a predetermined distance from the
same so as to face the magnetism generator supporting member
51.
[0029] A magnetic sensor 53 having a magnetic impedance element (MI
element) is fixed on the connecting member 22c. The magnetic sensor
53 is fixed so that its magnetism sensing direction is aligned with
the axis of the above-described orientation of the magnetic poles
of the magnet 52 (see FIG. 3). A harness 55 for signal transmission
is connected to the magnetic sensor 53.
[0030] The magnetic impedance element included in the magnetic
sensor 53 is the same as the magnetism sensing element disclosed in
Japanese Patent Laid-Open No. 2002-195854 or 2004-264050. This
magnetic impedance element is a magnetic element using a magnetic
phenomenon in which an impedance produced by applying a current
changing with time to a magnetic wire such as an amorphous alloy
wire is changed by an external magnetic field. With this magnetic
impedance element, a magnetic field (magnetic flux) generated by
the magnet 52 is detected.
[0031] As shown in FIG. 5, the magnet 52 is placed so that the
north pole is provided at the lower end, and so that the
orientation of the magnetic pole coincides with the direction of
bending of the magnetism generator supporting member 51 and the
springs 24 (the direction indicated by arrow L in FIG. 5). The
magnetism sensing direction of the magnetic sensor 53 (indicated by
arrow Z in FIG. 5) also coincides with the direction of bending of
the magnetism generator supporting member 51 and the springs 24. A
load converter 56 is connected to the magnetic sensor 53. A voltage
ew output from the magnetic sensor 53 is converted by the load
converter 56 into a signal representing a load applied from an
occupant to the vehicle seat 1.
[0032] A method of detecting a load applied from an occupant to the
vehicle seat 1 with the vehicle seat load detection device 5
according to this illustrative aspect of the present invention will
now be described.
[0033] When no occupant is sitting on the seat cushion 2, no bend
is caused in the springs 24 and the predetermined distance is
maintained between the magnet 52 and the magnetic sensor 53. At
this time, the magnetic sensor 53 detects the magnetic field
(magnetic flux) formed by the magnet 52 and generates the
predetermined voltage ew corresponding to the magnetic field (see
FIGS. 3 and 5). The yoke 51c with which the upper end of the magnet
52 is blocked has the function of causing lines of magnetic force
produced from the magnet 52 to pass through the yoke 51c to gather
below the magnet 52 instead of extending upward, thus increasing
the sensitivity of the magnetic sensor 53.
[0034] When a vehicle occupant sits on the seat cushion 2, the
magnetism generator supporting member 51 is downwardly bent
together with the plurality of springs 24 by an amount according to
the load applied from the occupant. With the downward bending of
the magnetism generator supporting member 51, the magnet 52
supported on the magnetism generator supporting member 51 is
brought closer to the magnetic sensor 53 fixed on the connecting
member 22c (see FIG. 6). The magnetic field of the magnet 52
detected with the magnetic sensor 53 is changed according to the
change in the distance between the magnet 52 and the magnetic
sensor 53. The level of voltage ew output by the magnetic sensor 53
is also changed thereby.
[0035] The relationship between the stroke S (the amount of
bending) of the springs 24 and the magnetism generator supporting
member 51, and the voltage ew is as shown in the diagram of FIG. 7.
By using this relationship, the amount of bending of the magnetism
generator supporting member 51 and the springs 24 can be detected
from the voltage ew output by the magnetic sensor 53. When the
amount of bending of the magnetism generator supporting member 51
and the springs 24 is found, the magnitude of the load applied to
the plurality of springs 24 integral with the magnetism generator
supporting member 51 can be detected on the basis of the spring
characteristics of the springs 24.
[0036] As described above, the output voltage ew from the magnetic
sensor 53 is converted by the load converter 56 into the signal
representing the load applied from the occupant to the vehicle seat
1. That is, the vehicle seat load detection device 5 can detect the
load applied to the vehicle seat 1 on the basis of the change of
the magnetic field detected with the magnetic sensor 53.
[0037] In the vehicle seat load detection device 5 according to
this illustrative aspect, when a vehicle occupants sits on the
vehicle seat 1, the springs 24 are bent by the amount according to
the load applied from the occupant to the vehicle seat 1. With the
bending of the springs 24, the distance between the magnet 52 and
the magnetic sensor 53 is changed. With the change in the distance
between the magnet 52 and the magnetic sensor 53, the magnetic
field of the magnet 52 detected with the magnetic sensor 53 is
changed. The load applied to the vehicle seat 1 can be detected on
the basis of the change of the magnetic field detected with the
magnetic sensor 53.
[0038] The magnetic sensor 53 has high magnetic sensitivity and is,
therefore, capable of detecting the displacement of the magnet 52
positioned at a distance of several ten millimeters therefrom. It
is, therefore, possible to directly detect the load applied to the
vehicle seat 1 from the amount of bending of the springs 24 without
using any special displacement amount converting member or the
like.
[0039] Thus, the vehicle seat load detection device 5 according to
this illustrative aspect of the present invention can be designed
by reducing the number of component parts in comparison with the
conventional art and can be easily manufactured at a reduced
cost.
[0040] The magnetic sensor 53 is attached to the connecting member
22c, i.e., the fixed member. Therefore, the magnetic sensor 53 to
which the harness 55 is connected is not moved by seating, thus
ensuring an improvement in durability of the electrical connection
between the magnetic sensor 53 and the harness 55. Also, the
facility with which furnishing with the harness 55 connected to the
magnetic sensor 53 is performed is improved and the facility with
which the magnetic sensor 53 is attached to the vehicle seat 1 is
also improved.
[0041] When a vehicle occupant or the like sits on the vehicle seat
1, the magnetism generator supporting member 51 is downwardly bent
together with the plurality of springs 24 to bring the magnet 52
closer to the magnetic sensor 53. Since at this time the distance
between the magnet 52 and the magnetic sensor 53 is changed with
the bending of the plurality of springs 24, the load applied to the
vehicle seat 1 can be detected with the magnetic sensor 53 with
high accuracy.
<Modification of the Device in the Illustrative Aspect>
[0042] An example of modification of the device in the illustrative
aspect 1 of the present invention will be described with reference
to FIGS. 8 and 9.
[0043] As shown in FIG. 8, the magnetism sensing direction of the
magnetic sensor 53 may be set perpendicular to the direction of
bending of the magnetism generator supporting member 51 and the
springs 24.
[0044] As shown in FIG. 9, the orientation of the magnetic poles of
the magnet 52 may be set perpendicular to the direction of bending
of the magnetism generator supporting member 51 and the springs
24.
<Other Illustrative Aspects>
[0045] The present invention is not limited to the illustrative
aspect described above with reference to the drawings. Technical
scope of the present invention also includes, for example,
illustrative aspects such as shown below. Further, various changes
other than those described below may be made and implemented
without departing from the gist of the invention.
[0046] (1) The magnetism generator may be attached to the fixed
member of the vehicle seat, while the magnetic sensor is attached
to the springs.
[0047] (2) An electromagnet may be used as a magnetism generator
instead of the permanent magnet. The magnetic may be selected
regardless of the existence/nonexistence of the yoke.
[0048] (3) A magnetism generator and a magnetic sensor may be
attached to the frame and spring members of the seat back and to
detect a load applied from the back of an occupant to the seat
back. Also, the load detection device may be attached to each of
the seat cushion and the seat back to perform load detection with
higher accuracy.
[0049] (4) The south pole of the magnet may be placed on the
magnetic impedance element side.
[0050] (5) A plurality of magnetism generators and a plurality of
magnetic sensors may be attached to perform load detection with
higher further improved accuracy.
[0051] (6) The magnetism generator and the magnetic sensor may be
arranged so that the magnetism generator and the magnetic sensor
are close to each other when no occupant is sitting on the seat,
and are moved away from each other by bending of the seat cushion
springs when an occupant sits on the seat.
[0052] (7) The magnetism generator may be directly attached to the
spring(s) without using the magnetism generator supporting
member.
* * * * *