U.S. patent application number 11/136987 was filed with the patent office on 2005-12-29 for method for operating a belt retractor and a belt retractor for a safety belt.
This patent application is currently assigned to TRW Automotive GmbH. Invention is credited to Holbein, Wolfgang, Prokscha, Martin.
Application Number | 20050284976 11/136987 |
Document ID | / |
Family ID | 35433210 |
Filed Date | 2005-12-29 |
United States Patent
Application |
20050284976 |
Kind Code |
A1 |
Holbein, Wolfgang ; et
al. |
December 29, 2005 |
Method for operating a belt retractor and a belt retractor for a
safety belt
Abstract
In a method for operating a belt retractor, the belt retractor
comprising a belt tensioner drive and with a pre-tensioner drive
which can both exert a torque onto a belt spool in a direction for
winding a safety belt, the pre-tensioner drive is prevented from
exerting a torque onto the belt spool through the activation of the
belt tensioner drive. In a belt retractor for a safety belt, having
a belt spool, a pre-tensioner drive with a drive motor, which can
turn the belt spool in the winding direction for the purpose of
pre-tensioning the safety belt, and with a belt tensioner drive
which can drive the belt spool for the purpose of a belt
tensioning, a safety mechanism is provided, which through an
activation of the belt tensioner drive prevents the pre-tensioner
drive from driving the belt spool in the winding direction.
Inventors: |
Holbein, Wolfgang; (Alfdorf,
DE) ; Prokscha, Martin; (Gmuend, DE) |
Correspondence
Address: |
TAROLLI, SUNDHEIM, COVELL, & TUMMINO L.L.P.
1111 LEADER BLDG.
526 SUPERIOR AVENUE
CLEVELAND
OH
44114-1400
US
|
Assignee: |
TRW Automotive GmbH
|
Family ID: |
35433210 |
Appl. No.: |
11/136987 |
Filed: |
May 25, 2005 |
Current U.S.
Class: |
242/374 ;
474/101 |
Current CPC
Class: |
B60R 22/4676 20130101;
B60R 2022/4666 20130101; B60R 2022/468 20130101; B60R 22/4628
20130101 |
Class at
Publication: |
242/374 ;
474/101 |
International
Class: |
B65H 075/48 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 3, 2004 |
DE |
10 2004 027 135.6 |
Claims
1. A method for operating a belt retractor, said belt retractor
being provided with a belt tensioner drive and with a pre-tensioner
drive, both said belt tensioner drive and said pre-tensioner drive
being adapted to exert a torque onto a belt spool in a direction
for winding a safety belt, the method containing the following
steps: activating said belt tensioner drive, preventing said
pre-tensioner drive from exerting a torque on said belt spool as a
consequence of said activation of said belt tensioner drive.
2. The method according to claim 1, characterized in that a flux of
force from said pre-tensioenr drive to said belt spool is
interrupted as a consequence of said activation of said belt
tensioner drive.
3. The method according to claim 1, characterized in that the belt
tensioner drive has a pyrotechnic gas generator which is actuated
when said belt tensioner drive is actuated and which prevents said
pre-tensioner drive from exerting a torque on said belt spool.
4. The method according to claim 3, characterized in that
activation of said pyrotechnic gas generator displaces a separating
element from an initial position, in which said pre-tensioner drive
is drivingly connected to said belt spool in a direction for
winding said safety belt onto the belt spool and hence for
pre-tensioning said safety belt, into a separating position in
which said pre-tensioner drive is disconnected from said belt
spool.
5. The method according to claim 3, characterized in that
activation of said pyrotechnic gas generator displaces a connecting
element from an initial position, in which said pre-tensioner drive
is drivingly connected to said belt spool in a direction for
winding said safety belt onto said belt spool and hence for
pre-tensioning said safety belt, into a separating position in
which said pre-tensioner drive is disconnected from said belt
spool.
6. The method according to claim 1, characterized in that said
pre-tensioner drive has an electric motor and in that activation of
said belt tensioner drive interrupts a current supply of said
electric motor.
7. The method according to claim 1, characterized in that said
pre-tensioner drive has an electric motor and in that activation of
said belt-tensioner drive results in operation of said electric
motor in a direction for unwinding said safety belt.
8. The method according to claim 1, characterized in that both said
pre-tensioner drive and also said belt-tensioner drive are
uncoupled from said belt spool by a rotation of said belt spool in
an unwinding direction of said safety belt.
9. A belt retractor for a safety belt, having a belt spool, a
pre-tensioner drive with a drive motor which can rotate said belt
spool in a winding direction so as to pre-tension a safety belt,
and having a belt tensioner drive which can drive said belt spool
so as to tension a safety belt, characterized in that a safety
mechanism is provided which through an activation of said belt
tensioner drive prevents said pre-tensioner drive from driving said
belt spool in said winding direction.
10. The belt retractor according to claim 9, characterized in that
said safety mechanism has a separating element.
11. The belt retractor according to claim 10, characterized in that
said separating element is adapted for mechanically separating a
connection from said pre-tensioner drive to said belt spool.
12. The belt retractor according to claim 11, characterized in that
said separating element separates a shaft.
13. The belt retractor according to claim 11, characterized in that
said pre-tensioner drive has one f a belt drive and a chain drive
and that said separating element is adapted to destroy said belt or
said chain.
14. The belt retractor according to claim 11, characterized in that
said pre-tensioner drive has a planetary gear and that said
separating element can destroy a support which is fixed to said
housing.
15. The belt retractor according to claim 11, characterized in that
said pre-tensioner drive has a toothed wheel gear and that said
separating element can make a bearing of said gear inoperative.
16. The belt retractor according to claim 11, characterized in that
said pre-tensioner drive has a toothed wheel gear and that said
separating element can transfer a connecting pin from an initial
position, in which it can transfer a torque from one component of
said gear to another, into a separating position.
17. The belt retractor according to claim 11, characterized in that
said pre-tensioner drive has a coupling and that said separating
element brings said coupling into an uncoupled state or holds it in
said uncoupled state.
18. The belt retractor according to claim 9, characterized in that
said separating element interrupts a supply of a drive motor.
19. The belt retractor according to claim 18, characterized in that
said separating element is a switch.
20. The belt retractor according to claim 18, characterized in that
said separating element destroys at least one supply line for said
drive motor.
21. The belt retractor according to claim 18, characterized in that
said separating element is part of a buckle- or end fitting
tensioner.
22. The belt retractor according to claim 18, characterized in that
said separating element short-circuits supply lines of said drive
motor.
23. The belt retractor according to claim 1 (, characterized in
that said separating element reverses a direction of rotation of
said drive motor.
24. The belt retractor according to claim 9, characterized in that
said belt tensioner drive has a pyrotechnic gas generator and that
said separating element is driven by a gas pressure which is
generated upon activation of said belt tensioner drive.
Description
[0001] The invention relates to a method for operating a belt
retractor.
BACKGROUND OF THE INVENTION
[0002] The invention in particular relates to a belt retractor
which is provided with a belt tensioner drive and with a
pre-tensioner drive, which can both exert a torque onto a belt
spool in a direction for winding the safety belt. The invention
additionally relates to a belt retractor for a safety belt, with a
belt spool, a pre-tensioner drive with a drive motor which can
rotate the belt spool for the purpose of pre-tensioning the safety
belt in the winding direction, and with a belt tensioner drive
which can drive the belt spool for the purpose of a belt
tensioning.
[0003] Both the pre-tensioner drive and also the belt tensioner
drive basically serve to drive the belt spool in the winding
direction when a vehicle state exists which is classified as
critical, so that the so-called belt slack of the safety belt is
eliminated and the safety belt lies taut against the body of a
vehicle occupant who is to be restrained. The pre-tensioner drive
differs from the belt tensioner drive firstly in that the
pre-tensioner drive operates reversibly. When, after the
pre-tensioning of the safety belt, the vehicle situation which was
classified as critical is no longer present, the belt spool is
returned into its initial position in the unwinding direction, so
that the tension in the safety belt drops again. A belt tensioner
drive, on the other hand, can only act on the belt spool in one
direction, namely turn it in the winding direction. A returning is
basically not possible. Generally, it is also not possible because
the belt tensioner drive is only triggered in those situations
which subsequently require the exchange at least of the belt
retractor together with the belt tensioner drive. Secondly, the
pre-tensioner drive differs from the belt tensioner drive with
regard to the forces applied onto the safety belt. The
pre-tensioner drive applies traction forces in the order of
magnitude of 100 N onto the safety belt. These forces, when they
occur during the travel operation, are generally not felt to be
unpleasant by the vehicle occupant. A belt tensioner drive, on the
other hand, tensions a safety belt with a much higher force
(distinctly above 1000 N); when the safety belt lies with this
force against the body of the vehicle occupant, this would be felt
to be unpleasant in the normal travel state. Owing to the
differences mentioned with regard to the mode of operation of the
pre-tensioner drive on the one hand and the belt tensioner drive on
the other hand, also structural differences result. A pre-tensioner
drive generally has an electric motor as drive element. A belt
tensioner drive, on the other hand, usually operates with a
pyrotechnic gas generator and a piston which converts the generated
gas pressure into a movement.
[0004] In addition to the pre-tensioner drive and the belt
tensioner drive, modern belt retractors have a force limiter system
by which the forces are limited which are present at a maximum in
the safety belt and therefore also act on the body of the vehicle
occupant. Usually, the force limiter systems make it possible that
despite the blocking of the belt spool, a particular length of the
safety belt can be withdrawn from the belt retractor against a
high, defined force. The force-limiter systems are coordinated here
with the airbag systems, likewise used in the vehicle, in order to
exert as uniform a restraining effect as possible together with a
gas bag unfolding in front of the vehicle occupant.
[0005] If, after the tensioning of the safety belt, the
force-limiting system responds, i.e. for example in the case of a
vehicle accident, it cannot be reliably predetermined whether the
pre-tensioner drive has been activated previously or is still
active. If the pre-tensioner drive is still coupled with the belt
spool, this leads to the traction force in the safety belt, which
is necessary for withdrawal of the safety belt from the belt
retractor, not only resulting from the resistance provided by the
force-limiter system, but also from the resistance which is
necessary to rotate the pre-tensioner drive in the unwinding
direction of the safety belt, i.e. in a direction contrary to the
current direction of action of the pre-tensioner drive. In other
words, higher forces occur in the safety belt when the
pre-tensioner drive is active than is actually provided (on the
basis of the design of the force-limiter system).
[0006] The object of the invention consists in providing a method
for operating a belt retractor, and also a belt retractor, in which
the force which is necessary with a belt spool which is blocked per
se for withdrawal of the safety belt and which is defined by the
force limiter system, is not altered by the respective operating
state of the pre-tensioner drive.
BRIEF DESCRIPTION OF THE INVENTION
[0007] In order to solve this problem, the invention provides a
method in which, when the belt tensioner drive is activated,
through the activation of the belt tensioner drive the
pre-tensioner drive is prevented from exerting a torque on the belt
spool. A belt retractor according to the invention is distinguished
in that a safety mechanism is provided, which with an activation of
the belt tensioner drive prevents the pre-tensioner drive from
driving the belt spool in the winding direction. In this way, it is
ensured that the force level provided by the force-limiter system
is not "falsified" by the pre-tensioner drive; irrespective of
whether the pre-tensioner drive has been activated or not, the
pre-tensioner drive does not have to be carried along in the
unwinding direction of the safety belt, when after activation of
the belt tensioner drive a high force is acting in the safety belt,
which leads to the response of the force-limiter system.
[0008] According to a preferred embodiment of the invention,
through the activation of the belt tensioner drive the flux of
force from the pre-tensioner drive to the belt spool is
interrupted. In this way, the belt spool can turn freely from the
pre-tensioner drive in the unwinding direction when the
force-limiter system responds. The pre-tensioner drive does not
need to be carried along.
[0009] According to a further preferred embodiment of the
invention, provision is made that the pre-tensioner drive has an
electric motor and that through the activation of the belt
tensioner drive the current supply of the electric motor is
interrupted. This prevents the electric motor from acting on the
belt spool in the winding direction if the belt spool were to in
fact rotate in the opposite direction under the action of the force
effective in the safety belt, i.e. in the unwinding direction, in
order to realize a force-limiting function. Then only the electric
motor has to be carried along; the torque occurring here is,
however, comparatively small, so that the force defined by the
force-limiter system in the safety belt is not substantially
increased.
[0010] According to a further embodiment of the invention,
provision is made that the pre-tensioner drive has an electric
motor and that through the activation of the belt tensioner drive,
the electric motor is operated in a direction for unwinding of the
safety belt. In this state, the electric motor therefore assists
the unwinding of the safety belt from the belt spool and hence the
response of the force-limiter system. As the torque provided by the
electric motor is comparatively small, a negligible effect is
produced on the force level provided by the force-limiter system,
from which the force-limiting function is realized.
[0011] According to the invention, provision is made that the belt
tensioner drive has a pyrotechnic gas generator which through its
activation prevents the pre-tensioner drive from exerting a torque
on the belt spool. This has the advantage that no external
additional control is necessary in order to uncouple the
pre-tensioner drive from the belt spool or to reverse its direction
of rotation; the uncoupling or reversal of the direction of
rotation of the pre-tensioner drive can be achieved with the gas
pressure which is provided by the belt tensioner drive for the
purpose of the belt tensioning.
[0012] Advantageous embodiments of the invention will be apparent
from the sub-claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention is described below with the aid of preferred
embodiments which are illustrated in the enclosed drawings. In
these:
[0014] FIG. 1 shows a diagrammatic view of a belt retractor
according to the invention with pre-tensioner drive and belt
tensioner drive;
[0015] FIG. 2 shows a diagrammatic view of a safety mechanism used
in the belt retractor of FIG. 1 in the initial state;
[0016] FIG. 3 shows the safety mechanism of FIG. 2 in the activated
state;
[0017] FIG. 4 shows a diagrammatic section through a belt retractor
according to a second embodiment of the invention;
[0018] FIG. 5 shows a diagrammatic section through a belt retractor
according to a third embodiment of the invention;
[0019] FIG. 6 shows diagrammatically a cut-out of the pre-tensioner
drive of a belt retractor according to a fourth embodiment of the
invention in the initial state;
[0020] FIG. 7 shows the cut-out of FIG. 6 with activated safety
mechanism;
[0021] FIG. 8 shows diagrammatically a part of the pre-tensioner
drive of a belt retractor according to a fifth embodiment of the
invention, the safety mechanism being situated in its initial
position;
[0022] FIG. 9 shows diagrammatically the cut-out of FIG. 8, the
safety mechanism having been activated;
[0023] FIG. 10 shows diagrammatically a cut-out of a pre-tensioner
drive of a belt retractor according to a sixth embodiment of the
invention, the safety mechanism being situated in its initial
state;
[0024] FIG. 11 shows the cut-out of FIG. 10, the safety mechanism
having been activated;
[0025] FIG. 12 shows diagrammatically a switching diagram for a
belt retractor according to a seventh embodiment of the
invention;
[0026] FIG. 13 shows diagrammatically a switching diagram of a belt
retractor according to an eighth embodiment of the invention, the
safety mechanism being in its initial position; and
[0027] FIG. 14 shows the switching diagram of FIG. 13, the safety
mechanism being in its activated state.
DETAILED DESCRIPTION OF THE INVENTION
[0028] In FIG. 1, a belt retractor 10 is shown diagrammatically,
which has a frame 12 and a belt spool 14 mounted in the frame 12. A
safety belt 16 is held on the belt spool 14. A blocking system 18
is provided, indicated diagrammatically, with which the belt spool
can be blocked in a belt band--sensitive and/or vehicle-sensitive
way. In addition, a spring cassette 20 is provided, which surrounds
a winding spring (not shown), which exerts a torque onto the belt
spool 14 in a direction which leads to the winding of the safety
belt 16. In addition, a force-limiter system 22 is provided, which
is illustrated here as a torsion rod 22 arranged inside the belt
spool 14. The precise construction and mode of operation of the
blocking system 18 and of the force limiter system 22 are of no
importance for the invention, so they are not explained further
here.
[0029] The belt retractor 10 is provided with a belt tensioner
drive 24 which has a pyrotechnic gas generator 26. The latter can
generate a gas, which is under pressure, on activation, which acts
on a piston (not illustrated), which in turn drives the belt spool
14 in the winding direction of the safety belt 16. In addition, a
pre-tensioner drive 28 is provided, which has an electric motor 30
as drive motor. This can be coupled via a gear and/or a coupling
with the belt spool 14 so that it can drive the latter both in the
winding direction and also in the unwinding direction of the safety
belt 16.
[0030] The pre-tensioner drive 28 has a safety mechanism 32, which
is formed here by a separating element 34 and an actor 36. The
actor 36 is formed here as a piston/cylinder drive, the cylinder
beam being coupled with the pyrotechnic gas generator 26 and the
piston being coupled with the separating element 34. The separating
element 34 is arranged so that it can engage on a belt drive 38
between the electric motor 30 and the belt spool 14.
[0031] In the initial position (see FIG. 2), the belt drive 38 is
intact. The electric motor 30 can therefore drive the belt spool 14
in the winding direction and in the unwinding direction of the
safety belt 16. When the belt tensioner drive is activated, i.e.
the pyrotechnic gas generator 26 is ignited, the latter firstly
drives the belt spool 14 in the winding direction of the safety
belt 16. At the same time, a portion of the generated compressed
gas is branched off for the safety mechanism 32, so that the actor
36 moves the separating element 34 from the initial position shown
in FIG. 2 into a separating position shown in FIG. 3. In this, the
separating element 34 has destroyed the belt drive 38 mechanically,
in particular has cut the belt of the belt drive, so that a
mechanical connection no longer exists between the electric motor
30 and the belt spool 14. If then, after completion of the belt
tensioning, such a force is acting in the safety belt 16 that the
force limiting system 22 responds and the belt spool 14 is turned
by the safety belt 16 in the unwinding direction, this takes place
entirely without impairment by the pre-tensioner drive 28, because
a mechanical connection no longer exists between the electric motor
30 of the pre-tensioner drive 28 and the belt spool 14.
[0032] In FIG. 4 a second embodiment is shown. The safety mechanism
32 also has an actor 36 here, which can move a separating element
34. In the same manner as in the embodiment according to FIGS. 2
and 3, the separating element is constructed as a sharp blade. This
blade acts here on a shaft 40 which connects the pre-tensioner
drive 28 with the belt spool 14. Through activation of the
pyrotechnic gas generator 26, the actor 36 moves the separating
element 34 in the direction of the arrow P, whereby the shaft 40 is
separated, sheared off or otherwise broken. Provision can be made
that the shaft 40 is provided with a nominal fracture site.
[0033] In FIG. 5 a third embodiment is shown. Instead of the shaft
40, here a connecting pin 42 leads between the pre-tensioner drive
28 (symbolized here by a pinion) and the belt tensioner drive 24
(symbolized here by a pinion coupled with the belt spool 14). The
connecting pin can be transferred by the actor 36 (formed here by a
pressure chamber which is closed of from one end side of the
connecting pin 42 and can be acted upon by the pressure of the
compressed gas generated by the gas generator 26) in the direction
of the arrow from the initial position shown in FIG. 5, in which
the pre-tensioner drive 28 is coupled with the belt spool 14, into
a separating position in which the connecting pin 42 no longer
engages into the pinion of the belt tensioner drive 24 and thereby
the connection to the belt spool 14 is interrupted.
[0034] In FIGS. 6 and 7 a fourth embodiment is shown. Here, also, a
connecting pin 42 is used, which can be transferred from an initial
position (see FIG. 6) into a separating position (see FIG. 7). In
the initial position, the connecting pin 42 connects two toothed
wheels 50, 52 which are part of a gear 54 between the electric
motor 30 of the pre-tensioner drive and the belt spool 14. In the
initial state, the connecting pin 42 provides a torque-transferring
connection between the two toothed wheels 50, 52. At the same time,
it serves for mounting. A slider 56 engages on the connecting pin
42, which slider can be acted upon by the actor 36 so that it draws
the connecting pin 7 in the direction of the arrow P into the
separating position. In the latter, the torque-transferring
connection between the two toothed wheels 50, 52 is interrupted, so
that the belt spool can turn in the unwinding direction without the
electric motor 30 having to be entrained.
[0035] According to a further development of the invention,
provision can be made that the safety mechanism 32 acts on a
coupling 60 which is provided between the electric motor 30 of the
pre-tensioner drive and the belt spool 14. This coupling is
indicated diagrammatically in FIG. 6. The safety mechanism 32 can
be constructed so that it prevents a transfer of force via the
coupling. For this purpose, for example the catches of the coupling
can be brought out of engagement and be blocked so that a renewed
guiding in is not possible. It is also possible to uncouple the
region of the force transfer catches from the rest of the housing.
Finally, the teeth on the axis into which the force transfer
catches engage can be closed or covered, so that a torque transfer
is not possible and the catches slip through.
[0036] In FIGS. 8 and 9 a fifth embodiment is shown. Here, also, a
gear 54 is used between the electric motor 30 of the pre-tensioner
drive and the belt spool 14. The gear 54 is constructed as a
planetary gearing, in which the sun wheel is coupled with the drive
motor and the hollow wheel is coupled with the belt spool. The
planetary wheels are mounted in a diagrammatically illustrated
planetary wheel carrier 70 which is supported so as to be fixed to
the frame. The safety mechanism here has a separating element 34
again, which can be moved by an actor from the initial position
shown in FIG. 8 into the separating position shown in FIG. 9, in
which the support of the planetary wheel carrier 70 on the frame 12
of the belt retractor is interrupted. In this way, a torque
transfer via the gear 54 is no longer possible, so that the
force-limiting function can act unimpaired by the pre-tensioner
drive.
[0037] In FIGS. 10 and 11, a sixth embodiment is shown. Here, also,
a gear 54 is used between the electric motor 30 of the
pre-tensioner drive and the belt spool 14. The gear 54 is
constructed here as a worm gear. The worm shaft is supported at one
end via a support element 80 on the frame 12. The actor 36 can
transfer the support element 80 from the initial position shown in
FIG. 10 into the separating position shown in FIG. 11, in which the
end of the worm shaft associated with the support element 80 is
freed. If a torque is to be transferred between the electric motor
30 and the belt spool 14, this can be deflected upwards in the
direction of the arrow P so that a torque transmission is
prevented.
[0038] According to a further development (not illustrated) of the
invention, provision can be made that after the pyrotechnic
tensioning by the belt tensioner drive 24, both the belt tensioner
drive 24 and also the pre-tensioner drive 28 are uncoupled from the
belt spool 14 by the reverse rotation of the belt spool 14 being
used for the uncoupling. For this purpose, for example catches of
the couplings, which are used to couple the pre-tensioner drive 28
and the belt tensioner drive 24 with the belt spool 14, can be
brought out of engagement through an axial displacement.
[0039] In FIG. 12 a seventh embodiment is shown. In this, the
ignition current for the pyrotechnic gas generator 26 controls an
electronic circuit or a relay in the control apparatus for the
reversible tension unit, i.e. for the pre-tensioner drive 28, which
exchanges the polarity of the supply voltage of the electric motor
30. Thereby, the electric motor 30 attempts to drive the belt spool
14 in the unwinding direction, whereby the coupling used to couple
the electric motor 30 with the belt spool 14 opens, so that the
electric motor is uncoupled from the belt spool 14.
[0040] In FIGS. 13 and 14, an eighth embodiment of the invention is
shown. In this embodiment also the polarity of the supply lines of
the electric motor 30 is exchanged through the ignition current of
the pyrotechnic gas generator 26. This takes place here through a
switch 90 which is activated by the ignition current of the gas
generator and switches a switch unit 92 from the initial state
shown in FIG. 13 into the state shown in FIG. 14 with reversed
polarity.
[0041] According to a further development of the invention, not
illustrated, provision can be made that through ignition of the
pyrotechnic gas generator 26, at least one supply line of the
electric motor 30 is interrupted. This can be realized for example
through actuation of a switch which is either actuated by the
ignition current for the pyrotechnic gas generator 26 or by the
compressed gas generated thereby. It is also possible to lay at
least one supply line of the electric motor 30 so that on ignition
of the pyrotechnic gas generator 26 it is separated through the
action of the pressure thus generated. Thereby, the electric motor
30 together with the gear can be turned backwards with little
effort of force. In addition, it is possible to lay at least one
supply line of the electric motor 30 so that it is separated
mechanically by a belt buckle or an end fitting when this is moved
by a belt buckle tensioner or an end fitting tensioner. Finally, it
is possible to mechanically short-circuit the two supply lines of
the electric motor 30 through the activation of the pyrotechnic gas
generator 26, so that the securing of the current supply of the
electric motor is activated, whereupon the latter becomes
currentless.
* * * * *