U.S. patent application number 11/052390 was filed with the patent office on 2005-08-25 for friction coupling.
This patent application is currently assigned to TRW Automotive GmbH. Invention is credited to Holbein, Wolfgang, Prokscha, Martin.
Application Number | 20050184185 11/052390 |
Document ID | / |
Family ID | 34853529 |
Filed Date | 2005-08-25 |
United States Patent
Application |
20050184185 |
Kind Code |
A1 |
Holbein, Wolfgang ; et
al. |
August 25, 2005 |
Friction coupling
Abstract
A friction coupling has a drive part, an output part, and a
friction element which can transfer a friction moment between the
drive part and the output part. A release element is provided which
after a predetermined rotation angle of the friction coupling can
act on the friction element so that a reduction of the friction
moment occurs.
Inventors: |
Holbein, Wolfgang; (Alfdorf,
DE) ; Prokscha, Martin; (Schwaebisch Gmuend,
DE) |
Correspondence
Address: |
TAROLLI, SUNDHEIM, COVELL & TUMMINO L.L.P.
526 SUPERIOR AVENUE, SUITE 1111
CLEVEVLAND
OH
44114
US
|
Assignee: |
TRW Automotive GmbH
|
Family ID: |
34853529 |
Appl. No.: |
11/052390 |
Filed: |
February 7, 2005 |
Current U.S.
Class: |
242/374 |
Current CPC
Class: |
B60R 2022/468 20130101;
B60R 2022/4666 20130101; F16D 7/022 20130101; F16D 41/12 20130101;
B60R 22/46 20130101 |
Class at
Publication: |
242/374 |
International
Class: |
B60R 022/46 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 19, 2004 |
DE |
10 2004 008 173.5 |
Claims
1. A friction coupling with a drive part, an output part, and a
friction element which can transfer a friction moment between said
drive part and said output part, characterized in that a release
element is provided which after a predetermined rotation angle of
said friction coupling can act on said friction element so that a
reduction of said friction moment occurs.
2. The friction coupling according to claim 1, characterized in
that said release element is a stop.
3. The friction coupling according to claim 2, characterized in
that said release element is adjustable.
4. The friction coupling according to claim 1, characterized in
that said friction element is a friction spring.
5. The friction coupling according to claim 4, characterized in
that said friction spring is a loop spring.
6. The friction coupling according to claim 4, characterized in
that said friction spring is an annular spring.
7. The friction coupling according to claim 4, characterized in
that said friction spring has an opening arm which can come into
abutment against said release element.
8. The friction coupling according to claim 4, characterized in
that said friction spring has a closure arm which can cooperate
with a support element.
9. The friction coupling according to claim 8, characterized in
that said support element is adjustable.
10. The friction coupling according to claim 8, characterized in
that a spring is arranged between said closure arm and said support
element.
11. The friction coupling according to claim 10, characterized in
that said spring is constructed as a separate component.
12. The friction coupling according to claim 10, characterized in
that said spring is formed by an extension of said opening arm.
13. The friction coupling according to claim 1, characterized in
that it is part of a system for setting at rest a sensor of a belt
retractor.
14. The friction coupling according to claim 1, characterized in
that it is part of a return brake of a belt retractor.
15. The friction coupling according to claim 1, characterized in
that it is part of a locking system of a belt retractor.
16. The friction coupling according to claim 1, characterized in
that it is part of a belt buckle.
17. The friction coupling according to claim 1, characterized in
that it is part of a safety belt deflection fitting.
18. The friction coupling according to claim 1, characterized in
that it is part of a reversible belt tensioner.
19. The friction coupling according to claim 1, characterized in
that it is part of a belt extender system.
20. The friction coupling according to claim 1, characterized in
that it is part of a belt buckle extender system.
Description
[0001] The invention relates to a friction coupling with a drive
part, an output part and a friction element which can transfer a
friction moment between the drive part and the output part. The
invention relates in particular to such a friction coupling which
can be used in a vehicle occupant restraint system.
BACKGROUND OF THE INVENTION
[0002] Friction couplings can be used in various ways in vehicle
occupant restraint systems. Examples of these are an arrangement
for putting at rest for sensors, the drive of reversible belt
tensioners, loop brakes, motion dampers in movable buckle
extenders, rotation speed limiters in belt locking systems or the
like. All friction couplings have in common here the fact that a
defined prestressing of the friction element, a defined looping
angle and a particular friction factor are required. The friction
moment provided by the friction coupling increases exponentially
with an increasing looping angle and increasing friction value
between the friction element and the component, on which the
friction element engages.
[0003] Owing to the exponential course of the friction moment, the
minimum friction moment transferred from the friction coupling can
be adjusted comparatively simply within desired tolerances. This is
more problematic with the maximum friction moment which can be
transferred from the friction coupling. Deviations of the looping
force of the friction moment from a nominal value upwards have a
very much stronger effect on the friction moment than deviations
downwards.
[0004] The object of the invention consists in further developing a
friction coupling of the type initially mentioned to the effect
that the friction moment transferred to a maximum from the friction
coupling is limited.
BRIEF DESCRIPTION OF THE INVENTION
[0005] For this purpose, in accordance with the invention a release
element is provided, which acts on the friction element after a
predetermined rotation angle of the friction coupling so that a
reduction of the friction moment is brought about. The invention is
based on the basic idea of allowing the friction moment generated
by the friction element to act at the start of the rotation moment
transfer from drive part to output part in each case. Even if this
friction moment is very much higher than is actually desired, this
has a positive effect sooner on the operation of the friction
coupling; it is therefore guaranteed under all circumstances that
firstly a moment of rotation is transferred from drive part to
output part. Only after the friction coupling has undertaken a
predetermined rotation angle is the friction element acted upon via
the release element, in order to delimit the friction moment which
is able to be transferred at a maximum from the friction coupling.
This ensures that in an operation phase of the friction coupling,
after the predetermined rotation angle has been run through and a
function associated with the corresponding rotation has been
carried out, a precisely defined maximum friction moment is not
exceeded. This ensures that in this operation phase, in which in
particular a slipping through of the friction coupling occurs, no
undesirably high friction moment is in action.
[0006] According to an embodiment of the invention, the release
element is a stop at which an arm of the friction element comes to
abut after the predetermined rotation angle has been run through.
In this way, an opening force is exerted onto the friction element,
which leads to a reduction of the friction force of the friction
element and hence to a reduction of the friction moment transferred
between the drive part and the output part.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The invention is described below with the aid of a preferred
embodiment which is illustrated in the enclosed drawings. In
these:
[0008] FIG. 1 shows a diagrammatic exploded drawing of a belt
retractor with a friction coupling;
[0009] FIG. 2 shows a section through the components of FIG. 1 in
installed state;
[0010] FIG. 3 shows a side view of a shifting coupling, used in a
belt retractor, in an initial position;
[0011] FIG. 4 shows a side view of the shifting coupling in coupled
state;
[0012] FIG. 5 shows a diagrammatic side view of a friction
coupling, used in the belt retractor of FIG. 1, in a first
operating phase;
[0013] FIG. 6 shows the friction coupling in a second operating
phase;
[0014] FIG. 7 shows an alternative development of the friction
coupling in the first operating phase;
[0015] FIG. 8 shows the friction coupling of FIG. 7 in a second
operating phase; and
[0016] FIG. 9 shows a diagram of the friction moment transferred
under various operating states from the friction coupling.
DETAILED DESCRIPTION OF THE INVENTION
[0017] In FIG. 1 a belt retractor for a vehicle safety belt is
shown in an exploded view, which has a frame 5, in which a belt
spool 10 is rotatably mounted. Coupled with the belt spool so as to
be secure with respect to rotation is a belt spool drive part 12,
which has outer teeth 20. The outer teeth are part of a shifting
coupling by means of which a drive moment can be transferred from a
wheel 24 to the belt spool. The wheel 24 is connected with an
electromotor (not illustrated) (see for example DE 201 15 316).
[0018] The wheel 24 has an insert part 24a in which several pockets
25 are formed, in which a catch 26 is arranged respectively, on
which a restoring spring 28 acts. Each catch is arranged together
with its restoring spring in one of the pockets 25, and the insert
part 24a is arranged, for example arrested, on the wheel 24. The
catches 26 are then held swivellably in the respective pocket.
[0019] Axially adjacent to the wheel 24, a coupling disc 34 is
arranged, which is provided with control tongues 36 which project
through recesses in the insert part 24a into the wheel 24, so that
they can cooperate with the catches 26. The coupling disc 34,
together with the wheel 24, the insert part 24a, the catches 26 and
the outer teeth 20, forms a shifting coupling.
[0020] The coupling disc 34 is supported on the frame 5 by means of
a friction coupling. The friction coupling has a friction element
which is constructed here as a friction spring 52. The friction
spring 52 is arranged in a groove 50 which is formed on the side of
the coupling disc 34 facing away form the wheel 24. The internal
diameter of the friction spring 52 is smaller in the initial state
than the external diameter of the groove 50, so that the friction
spring 52 sits in the groove 50 with a certain pre-stressing. The
friction spring 52 is constructed as an annular spring which has a
bent arm 54 at one end which acts as a closure arm and is supported
on the frame 5 of the belt retractor so as to be secure with regard
to rotation. For this purpose, a support element 55 is provided
(see FIG. 5). The friction spring 52 has at its other end a bent
arm 56 which acts as an opening arm and can cooperate with a
release element 58 (see likewise FIG. 5), which is arranged on the
frame 5. The friction spring 52 forms together with the coupling
disc 34 and the support element 55 a friction coupling which makes
possible a slipping through of the coupling disc 34 as soon as the
friction moment between the friction spring and the groove 50 of
the coupling disc 34 is overcome. Depending on the direction of
rotation of the coupling disc 34, either the coupling disc 34 or
the support element 55 acts as drive part; the other of the two
acts as output part.
[0021] The operation of the shifting coupling (see FIGS. 3 and 4)
and of the friction coupling (see FIGS. 5 and 6) is described
below. In the initial position of the shifting coupling (see FIG.
3), the catches 26 are held back by the restoring springs 28 so
that they are not in engagement with the outer teeth 20 of the belt
spool drive part 12. In this case, the belt spool 10 can freely
rotate and belt band can be withdrawn from the belt spool.
[0022] If the wheel 24 is set in rotation by the electromotor (not
illustrated), the catches are entrained. As the coupling disc 34 is
secured by means of the friction spring 52, the catches 26 run onto
the control tongues 36, whereby they are guided into the outer
teeth 20 (see FIG. 4). Now the wheel 24 is coupled with the belt
spool 10, so that the electromotor (not illustrated) can drive the
belt spool in the winding direction of the safety belt, whereby a
pre-tensioning is carried out. In so doing, the coupling disc 34 is
entrained via the control tongues 36 (see arrow P in FIG. 5), which
is possible without difficulty, because of the friction coupling
between the coupling disc and the frame 5 of the belt
retractor.
[0023] The friction coupling is set so that the friction moment
exerted by the support element 55 via the closure arm 54 and the
friction spring 52 onto the coupling disc 34 is in every case so
great that the catches of the shifting coupling can be guided in.
To increase the minimum friction moment of the friction coupling, a
spring 60 can be provided, which is arranged between the support
element 55 and the closure arm 54 of the friction spring 52 and
pre-stresses the closure arm 54 in the direction of closure of the
friction spring 52.
[0024] During the rotation of the coupling disc 34 in the direction
of the arrow P, a differentiation is to be made between two
different cases. In a first case, the friction moment which is
provided is higher than the required minimum friction moment, but
not greater than a permissible maximum friction moment. In this
case, the coupling disc 34 rotates inside the friction spring 52,
which remains approximately stationary in its position shown in
FIG. 5. In a second case, the friction moment provided by the
friction coupling is greater than a permissible maximum friction
moment (and hence, of course, also greater than the required
minimum friction moment). In this state, the coupling disc 34, when
it is rotated in the direction of the arrow P, entrains the
friction spring 52 in an anticlockwise direction, which is
permitted by the spring 60. After a predetermined rotation angle,
the opening arm 56 abuts onto the release element 58, whereby the
two arms 54, 56 of the friction spring 52 are moved apart. Thereby,
the looping force of the friction spring 52 decreases and thereby
also the friction moment provided by the friction coupling. In this
way, it is reliably prevented that an undesirably high friction
moment is in action. In FIGS. 7 and 8, an alternative embodiment is
shown. This differs from the friction coupling shown in FIGS. 5 and
6 in that the spring 60 is integrated into the closure arm 54. The
closure arm 54 is in fact constructed with a bent end which is
elastically flexible.
[0025] The path of the friction moment M, transferred from the
friction coupling, over a rotation angle .alpha. is illustrated for
various operating states with the aid of FIG. 9. "Min" designates
the moment of rotation which is necessary for guiding in the
catches. "N" designates the moment of rotation which is provided as
a minimum by the friction coupling. "H" designates the moment of
rotation which is provided as a maximum by the friction
coupling.
[0026] At the start of the rotation of the wheel 24, the moment
necessary for guiding in the catches 26 acts in the friction
coupling. As soon as the catches are guided in (rotation angle 1),
the acting moment of rotation increases, because the coupling disc
34 now has to be entrained. Assuming that the friction coupling
provides a comparatively low friction moment, the acting moment of
rotation rises for example up to the level N and remains at this
level over the further rotation angle (Path 1). If, on the other
hand, the friction coupling provides a high moment of rotation,
then starting from the complete guiding in of the catches 26, the
acting moment of rotation would rise to the level H and then remain
at this level over the further rotation angle. This would be
undesirable and is prevented. Owing to the spring 60, the friction
spring 52 in fact co-rotates as soon as a force F0 acts on it.
Thereby, the rise in the moment of rotation is limited and the
friction spring 52 can be rotated contrary to a rising moment of
rotation; the increase in this range (Path 2) is determined by the
elastic rigidity of the spring 60. At point 2 of the rotation of
the friction coupling, the opening arm 56 arrives in abutment
against the release element 58, and at point 3 the inherent
elasticity of the opening arm 56 is "used up", so that the friction
spring 52 is now opened. Therefore, the acting moment of rotation
remains over the further rotation angle at a level which lies
considerably below the maximum friction moment H (Path 3).
[0027] The path of the friction moment of the friction coupling can
be set through the construction of the spring 60 and also the
positioning of the support element 55 and of the release element
58. It is also possible to arrange the support element 55 and/or
the release element 58 displaceably on the frame 5 of the belt
retractor, so that for example different states can be connected in
depending on external parameters. These states can be connected for
example through a belt winding scanning, a control via a gear
similar to a chid's safety mechanism, by the linear adjustment of a
vertical adjuster, by the movement of the belt buckle, by a
relative movement in a locking system between coupling disc and
retractor axis or a movement of an end fitting of the safety belt.
The adjustment of the support element and/or of the release element
can also be controlled actively via an a actor, for example a
holding magnet, a lifting magnet, an electromotor or the like.
[0028] The friction coupling according to the invention was
described here as part of a reversible belt tensioner. However, a
variety of other possibilities of application are conceivable. For
example, the friction coupling can be used for putting the sensor
at rest with limitation of the friction force. It is also possible
to use the friction coupling as part of a recoil brake of a belt
retractor, which prevents an abrupt braking of the belt spool with
a rapid belt band return (and thereby triggers a blocking of the
belt spool) by braking of the belt spool in line with a specific
objective. It is also possible to use the friction coupling for
damping lock movements. It is also possible to use the friction
coupling for a damped deflection fitting on the vertical adjuster
as a function of the deflection angle and of the position of the
vertical adjuster. The friction coupling can also be used in
reversible tensioning processes, the force level acting on the belt
band being kept by a loop spring and thereby a guiding in of the
locking system being prevented. A reduction of the belt band force
can be realized here by means of a movement of the housing mounting
without an intrusive release impulse. The friction coupling can
also be used in lock extender systems to limit the elastic force in
swivel movements. The friction coupling can also be used in locking
systems in order to vary the elastic force for catch guiding
depending on the movement of rotation and hence to favourably
influence the dynamics, restoring behaviour, belt locking and
de-rattling. For example, with a return movement a higher force can
act on the inertia disc, in order to actuate a return unblocking by
means of different force levels and hence to achieve a minimum
return rotation angle.
* * * * *