U.S. patent application number 09/742591 was filed with the patent office on 2001-07-19 for belt retractor force limiter.
This patent application is currently assigned to TRW Occupant Restraint Systems GmbH & Co. KG. Invention is credited to Huber, Andreas.
Application Number | 20010008262 09/742591 |
Document ID | / |
Family ID | 8083382 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008262 |
Kind Code |
A1 |
Huber, Andreas |
July 19, 2001 |
Belt retractor force limiter
Abstract
The invention relates to a force limiter for a seat belt
retractor comprising a frame, a belt reel rotatably mounted in the
frame and a drum which may be coupled with the belt reel for joint
rotation. The force limiter further comprises a plastically
deformable metal band that may be wound on the drum with
dissipation of energy. The metal band runs through a plurality of
deflection elements arranged on the frame to be deformed thereby.
At least one of the deflection elements is supported on a
supporting structure fixed to the frame and is arranged on the
frame so as to be movable transversely to the metal band. The
deflection element is provided with a stepped contact surface area
for a correspondingly stepped abutment surface area on the
supporting structure, whereby, when the supporting structure
engages a step of the contact surface area, a retraction movement
of the deflection element relative to the metal band is
permitted.
Inventors: |
Huber, Andreas; (Durlangen,
DE) |
Correspondence
Address: |
TAROLLI, SUNDHEIM, COVELL, TUMMINO & SZABO L.L.P.
1111 LEADER BLDG.
526 SUPERIOR AVENUE
CLEVELAND
OH
44114-1400
US
|
Assignee: |
TRW Occupant Restraint Systems GmbH
& Co. KG
|
Family ID: |
8083382 |
Appl. No.: |
09/742591 |
Filed: |
December 21, 2000 |
Current U.S.
Class: |
242/379.1 |
Current CPC
Class: |
B60R 22/3413 20130101;
B60R 2022/288 20130101 |
Class at
Publication: |
242/379.1 |
International
Class: |
B60R 022/28 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 1999 |
DE |
299 22 561.5 |
Claims
1. A force limiter for a seat belt retractor comprising a frame, a
belt reel rotatably mounted in said frame and a drum which may be
coupled with said belt reel for joint rotation, and a plastically
deformable metal band that may be wound on said drum with
dissipation of energy, said metal band running through a plurality
of deflection elements arranged on said frame to be deformed
thereby, wherein at least one of said deflection elements is
supported on a supporting structure fixed to said frame and is
arranged on said frame so as to be movable transversely to said
metal band, said deflection element being provided with a stepped
contact surface area for a correspondingly stepped abutment surface
area on said supporting structure, whereby, when said supporting
structure engages a step of said contact surface area, a retraction
movement of said deflection element relative to said metal band is
permitted.
2. The force limiter as set forth in claim 1, wherein said
deflection element is movable in a constrained fashion by an
actuator substantially parallel to said abutment surface area.
3. A force limiter for a seat belt retractor comprising a frame, a
belt reel rotatably mounted in said frame and a drum which may be
coupled with said belt reel for joint rotation, and a plastically
deformable metal band that may be wound on said drum with
dissipation of energy, said metal band running through a plurality
of deflection elements arranged on said frame to be deformed
thereby, wherein at least one of said deflection elements is
supported on a supporting structure which has an abutment surface
area and is arranged on said frame so as to be movable
substantially parallel to said abutment surface area, said
deflection element comprising a stepped contact surface area for
said correspondingly stepped abutment surface area, whereby, when
said supporting structure engages a step of said contact surface
area, a retraction movement of said deflection element relative to
said metal band is permitted.
4. The force limiter as set forth in claim 3, wherein said
supporting structure is movable in a constrained fashion by an
actuator substantially parallel to said abutment surface area.
5. The force limiter as set forth in claim 2, wherein said actuator
is formed by a pyrotechnic piston/cylinder linear drive.
6. The force limiter as set forth in claim 4, wherein said actuator
is formed by a pyrotechnic piston/cylinder linear drive.
7. The force limiter as set forth in claim 2, wherein said actuator
is formed by a solenoid.
8. The force limiter as set forth in claim 4, wherein said actuator
is formed by a solenoid.
9. The force limiter as set forth in claim 2, wherein said actuator
comprises a preloaded spring.
10. The force limiter as set forth in claim 4, wherein said
actuator comprises a preloaded spring.
Description
TECHNICAL FIELD
[0001] The invention relates to a force limiter for a seat belt
retractor.
BACKGROUND OF THE INVENTION
[0002] Force limiters are typically used in a seat belt retractor
comprising a frame, a belt reel rotatably mounted in the frame and
a drum which may be coupled with the belt reel for joint rotation,
and a plastically deformable metal band that may be wound on the
drum with dissipation of energy, the metal band running through a
plurality of deflection elements arranged on the frame to be
deformed thereby. The mode of operation of such a force limiter is
based on the fact that a limited rotation of the belt reel in the
unreeling direction is permitted in a vehicle crash situation when
the belt is loaded beyond a predetermined critical value, the metal
band being drawn through the deflection elements and thereby being
plastically deformed. The force limiting level is dictated, on the
one hand, by the stiffness of the metal band and, on the other, by
the geometry of the arrangement of the deflection elements. Prior
art proposed defining the force limiting level selectively between
at least two values for adapting to the stature data of the
occupant. Selection may be done by movement of at least one of the
deflection elements. Since this movement of the deflection element
occurs against the metal band high positioning forces are
needed.
BRIEF SUMMARY OF THE INVENTION
[0003] The invention provides a force limiter for belt retractors
in which making the selection from a higher to a lower force level
requires less driving energy.
[0004] In accordance with a first embodiment of the invention this
is achieved in a force limiter for a seat belt retractor comprising
a frame, a belt reel rotatably mounted in the frame and a drum
which may be coupled with the belt reel for joint rotation. The
force limiter further comprises a plastically deformable metal band
that may be wound on the drum with dissipation of energy. The metal
band runs through a plurality of deflection elements arranged on
the frame to be deformed thereby. At least one of the deflection
elements is supported on a supporting structure fixed to the frame
and is arranged on the frame so as to be movable transversely to
the metal band. The deflection element is provided with a stepped
contact surface area for a correspondingly stepped abutment surface
area on the supporting structure, whereby, when the supporting
structure engages a step of the contact surface area, a retraction
movement of the deflection element relative to the metal band is
permitted. The movement of the deflection element occurs initially
only transversely to the direction of the supporting force,
requiring only friction forces to be overcome, thus a low driving
force being sufficient for the movement of the deflection element.
As soon as the supporting structure then engages a step of the
contact surface area of the deflection element, the deflection
element is urged by the effect of the supporting force into its
selected position corresponding to the lower force level until it
is stopped by the abutment surface area of the supporting structure
where it is safely locked in place.
[0005] In accordance with a second embodiment of the invention the
above object is achieved in a force limiter in which at least one
of the deflection elements is supported on a supporting structure
which has an abutment surface area and is arranged on the frame so
as to be movable substantially parallel to the abutment surface
area, the deflection element comprising a stepped contact surface
area for the correspondingly stepped abutment surface area,
whereby, when the supporting structure engages a step of the
contact surface area, a retraction movement of the deflection
element relative to the metal band is permitted. In this embodiment
of the invention the supporting structure is first moved
transversely to the direction of the supporting force or, in other
words, substantially parallel to the abutment surface area. Here
again only friction forces need to be overcome so that a
correspondingly low driving force is sufficient to move the
supporting structure. When subsequently the stepped abutment
surface area of the supporting structure engages a step of the
contact surface area of the deflection element, the deflection
element is able to give way under the effect of the supporting
force and to move into its selected position corresponding to the
lower force level until it is stopped by the abutment surface area
of the supporting structure where it is safely locked in place.
[0006] The movement of the deflection element in the first
embodiment or of the supporting structure in the second embodiment
transversely to the direction of the supporting force is
implemented preferably by an actuator. Such an actuator may be
formed by a pyrotechnic piston/cylinder linear drive, by a solenoid
or also by a preloaded spring.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic side view to assist in explaining how
the force limiter on a belt retractor is configured and works;
[0008] FIG. 2 is a detail taken from FIG. 1 illustrated
magnified;
[0009] FIG. 3 is a schematic section view through an actuator for a
deflection element in a starting position;
[0010] FIG. 4 is a view corresponding to that of FIG. 3 in the
switch-over condition;
[0011] FIG. 5 is a view analogous to that of FIG. 3 but showing a
second embodiment; and
[0012] FIG. 6 is a view corresponding to that of FIG. 5 in the
switch-over condition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] Referring now to FIG. 1 there is illustrated a belt
retractor including a frame 10 in which a belt reel 12 is rotatably
mounted. Wound on the belt reel 12 is the belt webbing 14. The belt
reel 12 may be coupled non-rotatably to a drum 16 on which a metal
band 18 is wound. The free end of the metal band 18 is guided
through several baffle-type deflection elements 20 fixedly arranged
on the frame 10 and one deflection element 22 movably arranged on
the frame 10. The baffle-type deflection elements 20, 22 form with
the metal band 18 and the drum 16, which may be coupled to the belt
reel 12, a force limiter. In the course of a vehicle impact the
drum 16 is coupled non-rotatably to the belt reel 12. Once the
traction in the belt webbing 14 exceeds a predetermined critical
value the metal band 18 is pulled through the deflection elements
20, 22, it thereby being plastically deformed and dissipating
energy spikes. The force limiting level is dictated by the
stiffness of the metal band 18 and the geometry of the baffles
formed by the deflection elements 20, 22. In Fig, 1 the deflection
element 22 is shown in a starting position corresponding to a
higher force limiting level, whereas in FIG. 2 the deflection
element 22 is shown in a selected position corresponding to a lower
force limiting level in which the deflection element 22 has stepped
back from the metal band 18 and distanced itself from the starting
position by a spacing S2. Since the metal band 18 now undergoes no
plastic deformation at the deflection element 22, less traction is
sufficient to pull the metal band 18 through the remaining
deflection elements 20.
[0014] Referring now to FIG. 3 there is illustrated an embodiment
in which the deflection element 22 is integrally coupled to a
piston 24. The piston 24 is accommodated in a cylinder 26, at the
closed bottom of which a pyrotechnic charge 28 is arranged. The
piston 24 forms with the cylinder 26 and the pyrotechnic charge 28
a pyrotechnic piston/cylinder linear drive. At its surface area
facing away from the metal band 18 the deflection element 22
comprises a stepped contact surface area having two recesses 30. A
supporting structure fixedly arranged on the frame including two
supporting elements 32 forms an abutment surface area against which
the deflection element 22 abuts with its contact surface area. In
the starting position as shown in FIG. 3, the same as shown in FIG.
1, the deflection element 22 abuts against the supporting elements
32 with the steps adjoining the recesses 30. In this position the
piston 24 is accommodated in the cylinder 26. By activating an
electric igniter the pyrotechnic charge 28 is activated and
produces a force F1 which propels the piston 24 from the cylinder
26 to thereby advance the deflection element 22 in the direction of
the force F1 perpendicular to the direction of the supporting force
F2 with which the metal band 18 is supported by the deflection
element 22. The force F1 merely needs to overcome friction forces
between the metal band 18 and the deflection element 22 so that a
relatively low driving force is sufficient. Due to this advance
movement the deflection element 22 attains the selected position as
shown in FIG. 4, corresponding to the lower force level to be seen
from the situation as shown in FIG. 2. The supporting elements 32
of the supporting structure fixedly arranged on the frame now
engage the recesses 30 in the stepped contact surface area of the
deflection element 22 so that the latter is able to step back from
the metal band 18 and move in the direction of the supporting force
F2 until its stepped abutment surface area contacts the abutment
surface area of the supporting elements 32. In this position the
deflection element 22 is arrested in the recesses 30 due to they
being engaged by the supporting elements 32.
[0015] Referring now to FIGS. 5 and 6 there is illustrated an
embodiment based on the same principle as that of the embodiment as
shown in FIGS. 3 and 4, except that in this embodiment the
supporting elements 32 are not fixedly arranged on the frame but on
a supporting structure 34 movably mounted on the frame. The
supporting structure 34 is controlled by an actuator, more
particularly by a pyrotechnic piston/cylinder linear drive as
evident from FIGS. 3 and 4. The deflection element 22 is movably
guided only in the direction of the supporting force F2 in the
frame 10 of the belt retractor. In this embodiment too, the
actuator merely needs to overcome friction forces to move the
supporting structure 34 since the movement of the supporting
elements 32 is perpendicular to the direction of the supporting
force F2.
[0016] Activation of the actuator, which in the case of the FIGS. 3
and 4 drives the deflection element 22, and in the case of FIGS. 5
and 6 moves the supporting structure 34, is caused by a sensing
system which analyzes individual stature data of the vehicle
occupant, more particularly the body weight.
[0017] Since only friction forces need to be overcome in moving the
deflection element 22 from its starting position into its advanced
position, and the movement occurs in a constrained fashion in the
direction of the supporting force F2 across the distance S2 through
this supporting force F2, only a low actuating force is needed to
switch over the force limiter from a higher force level to a lower
force level. This thus enables many different variants to be taken
into account as the actuator, i.e. in addition to the pyrotechnic
version already described, also a solenoid, a preloaded spring as
energy storing means, a hydraulic or also a pneumatic actuator.
* * * * *