U.S. patent application number 11/759443 was filed with the patent office on 2007-10-04 for seat belt force sensor system.
This patent application is currently assigned to Siemens Automotive Corporation. Invention is credited to Brian M. Curtis, Robert Graf, Harald Lichtinger.
Application Number | 20070228707 11/759443 |
Document ID | / |
Family ID | 26898893 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070228707 |
Kind Code |
A1 |
Curtis; Brian M. ; et
al. |
October 4, 2007 |
SEAT BELT FORCE SENSOR SYSTEM
Abstract
A system for measuring seat belt forces is used to control
deployment of vehicle airbags. The system includes a rigid plate
member having one end attached to a portion of the seat belt and an
opposite end mounted to a vehicle structure. The seat belt is used
to secure passengers or an infant car seat to the vehicle seat. A
sensor including a strain gage is mounted on the rigid plate
between the ends and is used to measure the magnitude of forces
exerted on the seat belt by the passenger or car seat. The strain
gage generates a signal representative of the tension in the seat
belt, which is used to control deployment of the airbag. The airbag
is not deployed if the tension in the seat belt exceeds a
predetermined limit.
Inventors: |
Curtis; Brian M.; (Orion,
MI) ; Lichtinger; Harald; (Auburn Hills, MI) ;
Graf; Robert; (Pichl/Gsies, IT) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY LAW DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Assignee: |
Siemens Automotive
Corporation
Auburn Hills
MI
|
Family ID: |
26898893 |
Appl. No.: |
11/759443 |
Filed: |
June 7, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10987462 |
Nov 12, 2004 |
7234729 |
|
|
11759443 |
Jun 7, 2007 |
|
|
|
10603632 |
Jun 25, 2003 |
6860160 |
|
|
10987462 |
Nov 12, 2004 |
|
|
|
09853338 |
May 11, 2001 |
6595545 |
|
|
10603632 |
Jun 25, 2003 |
|
|
|
60203778 |
May 12, 2000 |
|
|
|
60207503 |
May 26, 2000 |
|
|
|
Current U.S.
Class: |
280/735 |
Current CPC
Class: |
B60R 21/0155 20141001;
B60R 21/33 20130101; B60R 22/18 20130101; B60R 21/01516 20141001;
B60R 2022/1806 20130101; B60R 21/01556 20141001; G01L 5/103
20130101; B60R 22/16 20130101 |
Class at
Publication: |
280/735 |
International
Class: |
B60R 21/02 20060101
B60R021/02 |
Claims
1. A sensor system for controlling airbag deployment comprising: a
rigid plate having a first end adapted to support a portion of a
seat belt and a second end adapted for attachment to a vehicle
structure; a strain gage mounted on said rigid plate between said
first and second ends for measuring the strain exerted on said
rigid plate by a tension force applied to the seat belt; and an
electrical connector mounted to said rigid plate adjacent to said
strain gage for receiving strain measurements from said strain gage
and transmitting said measurements to a processor to determine the
magnitude of the tension force wherein the processor generates a
force signal representative of the magnitude of said tension force
and wherein airbag deployment is controlled based on said force
signal.
2. The sensor system according to claim 1 including an airbag
adapted for mounting adjacent to a vehicle seat.
3. The sensor system according to claim 2 wherein said airbag does
not deploy when said force signal exceeds a predetermined
limit.
4. The sensor system according to claim 1 wherein said rigid plate
includes a neck portion positioned between said first and second
ends, said neck portion having a width that is less than a width of
said first and second ends and wherein said strain gage is mounted
on said neck portion.
5. The sensor system according to claim 1 including a printed
circuit board supported by said electrical connector.
6. The sensor system according to claim 1 including an electronic
control unit incorporated into said electrical connector.
7. The sensor system according to claim 1 wherein attachment of
said second end to the vehicle structure comprises a rigid
attachment.
8. The sensor system according to claim 7 wherein said second end
of said rigid plate is directly securable to a rigid structure with
at least one fastening element.
9. The sensor system according to claim 8 wherein said at least one
fastening element comprises a pin.
10. The sensor system according to claim 8 wherein said at least
one fastening element comprises a mechanical fastener.
11. The sensor system according to claim 1 wherein the portion of
the seat belt is solely supported by said first end.
12. A method for controlling airbag deployment comprising the steps
of: (a) providing a sensor assembly including a rigid plate having
a first end adapted to support a seatbelt portion and a second end
adapted for securement to a vehicle structure; (b) mounting a
strain gage to the rigid plate between the first and second ends;
(c) mounting an electrical connector to the rigid plate adjacent to
the strain gage; (d) measuring strain on the rigid plate due to
seatbelt tension force with the strain gage; and (e) controlling
airbag deployment based on strain measured in step (d).
13. The method according to claim 12 including the step of mounting
a printed circuit board to the electrical connector.
14. The method according to claim 12 including forming the rigid
plate as a single rigid plate and wherein step (b) includes
mounting the strain gage directly to the single rigid plate.
15. The method according to claim 12 including solely supporting
the seatbelt portion with the first end.
16. The method according to claim 12 including fastening the second
end directly to a rigid structure with at least one fastening
element.
17. The method according to claim 12 including not deploying an
airbag when the strain exceeds a predetermined limit.
18. The method according to claim 12 including forming the rigid
plate as a single rigid plate and wherein step (b) includes
mounting the strain gage directly to the single rigid plate.
19. The method according to claim 12 including solely supporting
the seatbelt portion with the first end.
20. The method according to claim 12 including fastening the second
end directly to a rigid structure with at least one fastening
element.
Description
RELATED APPLICATION
[0001] This application is a continuation of U.S. Ser. No.
10/987,462 filed on Nov. 12, 2004, which is a divisional of U.S.
Ser. No. 10/603,632 filed Jun. 25, 2003 which is a divisional of
U.S. Ser. No. 09/853,338 filed on May 11, 2001, now U.S. Pat. No.
6,595,545, which claims priority to provisional applications
60/203,778 filed on May 12, 2000, and 60/207,503 filed on May 26,
2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a method and apparatus for
measuring the force applied to a seat belt. Specifically, a sensor
arrangement is mounted on a rigid plate secured between a seat belt
portion and a vehicle structure to provide accurate seatbelt force
measurements.
[0004] 2. Related Art
[0005] Most vehicles include airbags and seatbelt restraint systems
that work together to protect the driver and passengers from
experiencing serious injuries due to high-speed collisions. It is
important to control the deployment force of the airbags based on
the size of the driver or the passenger. When an adult is seated on
the vehicle seat, the airbag should be deployed in a normal manner.
If there is an infant seat secured to the vehicle seat then the
airbag should not be deployed or should be deployed at a
significantly lower deployment force. One way to control the airbag
deployment is to monitor the weight of the seat occupant.
[0006] Current systems for measuring the weight of a seat occupant
are complex and expensive. One type of system uses pressure
sensitive foil mats mounted within the seat bottom foam. Another
system uses sensors placed at a plurality of locations within the
seat bottom. The combined output from the mats or the sensors is
used to determine the weight of the seat occupant. If the sensors
become damaged or fail to operate for some reason, the system will
not provide accurate seat weight measurements and airbag deployment
could occur under undesirable conditions.
[0007] Also mounting sensor systems within the seat can be
difficult and time consuming.
[0008] It is difficult to find mounting locations for each the
sensors that will accommodate all of the various positions of a
seated occupant while still providing accurate measurements.
Further, shifting of the occupant on the seat can dislodge or move
the sensors out of their proper location. Because the sensors are
mounted within the seat bottom, it is difficult to reposition the
sensors after the seat is installed in the vehicle.
[0009] Current sensor systems also can have difficulty determining
whether an adult is belted to the seat or whether a child car seat
is belted to the seat. When a child seat is secured to a seat with
a seat belt, an excess force acts on the sensors mounted within the
rear portion of the seat bottom, which interferes with accurate
weight sensing. Over tightening of the seatbelt to securely hold
the child seat in place, pulls the child seat down against the rear
part of the seat bottom, causing the excessive force measured by
the sensors. Due to this effect, the current weight sensing systems
have difficulty in discerning between an adult belted to a seat and
a child seat secured to the seat with a seat belt.
[0010] Thus, it is desirable to have a system for determining
whether conditions are proper for deploying an airbag by
determining whether a child seat or an adult is secured to the seat
with a seat belt. The system should further work with traditional
seat occupant weight sensing systems and should provide accurate
measurements, be easy to install, and overcome the above referenced
deficiencies with prior art systems.
SUMMARY OF THE INVENTION
[0011] A seat belt sensor system includes a load cell with a strain
gage that is integrated into a seat belt mechanism that is used to
secure an occupant to a vehicle seat. When the seat belt is
tightened, the sensor is pulled into tension and this is measured
by the strain gage. The strain gage measurements and signals are
send to an electronics unit that processes the signals and feeds
the signal back to an occupant sensing control unit. Occupant
sensing control unit uses the information to determine whether a
child seat or an adult is belted to the vehicle seat an ultimately
controls the deployment of an airbag mechanism.
[0012] In a disclosed embodiment of this invention, the sensor
assembly includes rigid member with a first end for supporting a
seat belt portion and a second end for attachment to a vehicle
structure, such as a B-pillar or seat mount, for example. The
strain gage is mounted on the rigid member between the first and
second ends and is used to measure the strain exerted on the rigid
member by tension forces applied to the seat belt portion. An
electrical connector is also mounted to the rigid member next to
the strain gage. The electrical connector receives the strain
measurements and transmits the measurements to a central processor
to determine the magnitude of the tension force.
[0013] Preferably the rigid member is formed as a metallic plate
that is defined by a length, width, and thickness. The length is
greater than the width and the thickness is significantly less than
the length and the width. The rigid member includes a neck portion
positioned between the first and second ends with the width being
less than the width of the first and second ends. The strain gage
is mounted on the neck portion and measures the strain resulting
from tension forces exerted on the first end of the rigid member by
the seat belt.
[0014] In a preferred embodiment, the sensor assembly is
incorporated into an occupant sensing control system that controls
deployment of safety devices such as an airbag based on the tension
forces measured in the seat belt. The strain gage generates a
signal representative of the tension forces in the seat belt and
transmits the signal to an electronic controller or processor. The
airbag is prevented from deploying if the signal exceeds a
predetermined limit.
[0015] A method for controlling airbag deployment includes the
following steps. The seat belt assembly is provided with a buckle
strap attached to a male buckle member and a seat belt latch
mechanism with a female receptacle for receiving the male buckle
member to secure the occupant to the vehicle seat. The rigid plate
has one end secured to a portion of the seat belt and an opposite
end of the plate is secured to a vehicle structure with a strain
gage mounted to the rigid plate between the ends. The male buckle
member is latched to the female receptacle and a tension force is
generated on the seat belt assembly by tightening the buckle strap.
The strain is measured on the rigid plate due to the tension force
with the strain gage. A tension force signal is generated based on
strain measurement and deployment of an airbag is controlled based
on the tension force signal.
[0016] The airbag is not deployed if the tension in the seat belt
exceeds a predetermined limit. By measuring the tension in the seat
belt a differentiation can be made between an adult belted to a
seat and a child seat belted to the seat. Thus, deployment of the
airbag can be more effectively controlled and will not be deployed
when a child seat is belted in place.
[0017] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic view showing a vehicle with an airbag
system and an occupant sitting in a seat with the airbag in an
active state shown in dashed lines.
[0019] FIG. 2 is a schematic side view of a seat assembly with an
infant car seat secured to the vehicle seat.
[0020] FIG. 3 is a schematic front view of a seat and seat belt
assembly.
[0021] FIG. 4 is an overhead view of subject sensor assembly.
[0022] FIG. 5 is a side view of the sensor of FIG. 4.
[0023] FIG. 6 is schematic diagram of the control system.
[0024] FIG. 7 is a perspective view of an alternate embodiment of
the sensor assembly.
[0025] FIG. 8 is a side cross-sectional view of the sensor assembly
mounted to a B-pillar.
[0026] FIG. 9 is a perspective view of the sensor assembly of FIG.
8.
[0027] FIG. 10 is a perspective view, partially cut-away, of the
sensor assembly mounted in a seat latch mechanism.
DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT
[0028] A vehicle includes a vehicle seat assembly, shown generally
at 12 in FIG. 1, and an airbag system 14. The seat assembly 12 is
preferably a passenger seat and includes a seat back 16 and a seat
bottom 18. A vehicle occupant 20 is secured to the seat 12 with a
seatbelt 22. A tension force F.sub.T is exerted on the seat belt
22. The tension force F.sub.T represents the force is exerted
against the occupant as the belt is tightened.
[0029] The airbag system 14 deploys an airbag 24 under certain
collision conditions. The deployment force for the airbag 24, shown
as deployed in dashed lines in FIG. 1, varies depending upon the
type of occupant that is belted to the seat 12. When an adult 20 is
belted to the vehicle seat 12, the airbag 24 should be deployed in
a normal manner shown in FIG. 1. If there is an infant or child
seat 26 secured to the vehicle seat 12, see FIG. 2, then the airbag
24 should not be deployed. Thus, it is important to be able to
determine whether there is an adult 20 belted to the seat 12 or
whether an infant seat 26 is secured to the seat with a seat belt
22. One way to determine this is by monitoring the tension exerted
on the seat belt 22. When an adult 20 is belted to the seat, normal
seat belt forces are exerted against the seat belt 22. When an
infant or child seat 26 is belted to the seat 12, high tension
forces are exerted on the seat belt 22 because the seat belt 22 is
overtightened to securely hold the child seat 26 in place.
[0030] The seat belt 22, shown more clearly in FIG. 3, has a strap
portion 28 that includes a shoulder harness and/or lap belt that is
connected to a male buckle member 30. A seat belt latch mechanism
32 is hard mounted to the seat 12 and typically extends outwardly
from the seat 12 between the seat back 16 and the seat bottom 18.
The latch mechanism 32 includes a female receptacle 34 that
receives the male buckle member 30 to secure the occupant 20 or
child seat 26 to the seat 12. The strap portion 28 can be manually
or automatically tightened once the belt is buckled to a desired
tension.
[0031] A sensor assembly 40 for measuring the tension forces in the
seat belt 22 is shown in FIGS. 4 and 5. The sensor assembly 40
includes a rigid member that is preferably formed as a metallic
plate 42 from 4130Rc39 material, however, other similar materials
could also be used. The plate 42 includes a first end 44 that is
attached via a loop connection 46 to material that forms a portion
of the seat belt 22 and a second end 48 that is attached to a
vehicle structure. The vehicle structure attachment will be
discussed in greater detail below.
[0032] The plate 42 is defined by a length "l", a width "w", and a
thickness "t". In the preferred embodiment, the length l is greater
than the width w and the thickness t is significantly less than the
width w and the length l. The plate 42 includes a necked portion 50
positioned between the ends 44, 48 that is narrower than the ends
44, 48. A strain gage 52 is mounted on the necked portion 50. The
tightening of the seat belt 22 exerts a tension force F.sub.T on
the plate 42 via the looped connection 46, which results in strain
on the necked portion 50. The strain gage 52 measures this strain.
The strain gage 52 is preferably a full bridge strain gage with
four (4) grids.
[0033] The first end 44 of the plate 42 is preferably positioned at
an angle relative to the necked portion 50 and the second end 48.
This causes the tension force to be applied at an angle, which
creates a moment M.sub.T at one edge of the necked portion 50. The
second end 48 of the plate 42 is hard mounted to a vehicle
structure creating a reaction force F.sub.rea and moment M.sub.rea.
The strain gage 52 measures the strain resulting in the necked
portion 50 of the plate 42 as the tension force F.sub.T is applied
to the first end 44 of the plate 42.
[0034] An electrical connector 54 is also mounted on the plate 42
adjacent to the strain gage 52. The strain measurements are
generated as signals 56 that are sent from the gage 52 to the
connector 54 and then to an electronic control unit (ECU) or
microprocessor 58, see FIG. 6. The ECU 58 can be incorporated into
the connector 54 to include the necessary electronics and printed
circuit board (as shown in FIG. 5) or can be a separate component
at a remote location on the vehicle. The ECU 58 processes the
strain signals 56 to determine the magnitude of the tension forces
FT exerted on the seat belt 22 and sends a control signal 66 to a
central electronic control unit (ECU) or central microprocessor 60
to control deployment of the airbag 24. It should be understood
that the ECU 58 and the central ECU 60 could be separate units or
could be the same unit. An optional configuration for an electrical
connector 62 is shown in FIG. 7. This configuration includes a
simplified wire connection 64 to the ECU 58 and/or 60.
[0035] As discussed above, the plate 42 is hard mounted to a
vehicle structure. The vehicle structure can be a B-pillar 68 as
shown in FIGS. 8 and 9 or the seat latch mechanism 32 as shown in
FIG. 10. The B-pillar 68 extends vertically to one side of the
vehicle and is typically positioned adjacent to the seat 12 and
behind a front passenger door of the vehicle. The B-pillar mount
includes a secondary metal plate 70 that includes a circular boss
72 for receiving a pivot pin 74 at one end 76. The opposite end 78
of the secondary metal plate 70 is mounted to the rigid metal plate
42 with at least one fastener 80.
[0036] The seat latch mechanism mount is shown in FIG. 10. The
second end 48 of the plate 42 includes at least one aperture 82 for
receiving a fastener 84 to hard mount the plate 42 to the seat. The
opposite end 44 of the plate 42 has an elongated slot 86 for
connecting the plate 42 to the looped material, which extends to
the female receptacle 34 having a slot 88 for receiving the buckle
member 30.
[0037] In both configurations, the strain gage 52 measure the
strain caused by the tension force F.sub.T in the seat belt 22. The
airbag deployment is controlled based upon the strain measurements
and the airbag 24 is not deployed if the tension force F.sub.T
exceeds a predetermined limit. An adult can experience a tension
force in a seat belt up to approximately 30 pounds (lbs) and still
be comfortable. If the strain gage 52 measures a tension force
F.sub.T that exceeds 30 lbs than that would indicate that a child
seat 26 has been belted to the seat 12. Thus, the airbag 24 would
not be deployed during a collision under these conditions. It
should be understood that 30 lbs is an approximate value, which can
vary due to differing seat and seatbelt configurations. Thus, the
predetermined limit for comparison to the measured tension force
F.sub.T can also vary depending upon the seat configuration.
[0038] The subject sensing system provides simplified and efficient
apparatus and method for determining whether conditions are proper
for deploying an airbag 24 by measuring seatbelt forces to discern
whether a child in a child seat 26 or an adult is belted to the
seat 12. The system provides accurate measurements and is easy to
install.
[0039] Although a preferred embodiment of this invention has been
disclosed, it should be understood that a worker of ordinary skill
in the art would recognize many modifications come within the scope
of this invention. For that reason, the following claims should be
studied to determine the true scope and content of this
invention.
* * * * *