U.S. patent application number 10/522608 was filed with the patent office on 2005-08-11 for safety belt retractor having a pretensioning device.
Invention is credited to Gross, Peer, Lucht, Andreas, Matzen, Frank, Patel, Yogel, Wittenberg, Geert-Helge, Ziel, Erik.
Application Number | 20050173580 10/522608 |
Document ID | / |
Family ID | 29557445 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050173580 |
Kind Code |
A1 |
Lucht, Andreas ; et
al. |
August 11, 2005 |
Safety belt retractor having a pretensioning device
Abstract
A safety belt retractor, especially for use in motor vehicles,
is provided, and has a blocking system and a tensioning device,
which acts on a belt shaft, for carrying out a reversible
pretensioning of an occupant. A spiral toothing meshes with an
external toothing of the belt shaft, and is supported against a
fixed counter-bearing such that upon an axial loading of the spiral
toothing directed against the counter-bearing due to load acting on
the belt shaft in a belt withdrawal direction, rotation of the
spiral toothing, for receiving torque applied by the belt shaft, is
prevented via a support force. An electric motor is coupled to the
belt shaft via the spiral toothing.
Inventors: |
Lucht, Andreas; (Horst,
DE) ; Wittenberg, Geert-Helge; (Norderstedt, DE)
; Matzen, Frank; (Hamburg, DE) ; Ziel, Erik;
(Quickborn, DE) ; Gross, Peer; (Hamburg, DE)
; Patel, Yogel; (Alingsas, SE) |
Correspondence
Address: |
Robert W Becker & Associates
707 Highway 66 East
Suite B
Tijeras
NM
87059
US
|
Family ID: |
29557445 |
Appl. No.: |
10/522608 |
Filed: |
March 2, 2005 |
PCT Filed: |
May 27, 2003 |
PCT NO: |
PCT/EP03/05545 |
Current U.S.
Class: |
242/374 ;
280/807 |
Current CPC
Class: |
B60R 22/46 20130101;
B60R 2022/4666 20130101 |
Class at
Publication: |
242/374 ;
280/807 |
International
Class: |
B65H 075/48 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 2002 |
DE |
102242364 |
Claims
1-16. (canceled)
17. A belt shaft retractor having a blocking system that is
controlled in a vehicle sensitive and/or belt strap sensitive
manner, and also having a tensioning device, which acts on the belt
shaft (12), for carrying out a reversible pretensioning of a
vehicle occupant, comprising: a spiral toothing (19) that meshes
with an external toothing (20) of the belt shaft (12); a fixed
counter-bearing (23) wherein said spiral toothing (19) is supported
against said counter-bearing such that upon an occurrence of an
axial loading of said spiral toothing (19) directed against said
counter-bearing (23) due to a load acting upon said belt shaft (12)
in a belt withdrawal direction, a rotation of said spiral toothing,
for receiving a torque applied by said belt shaft (12) is prevented
via a support force; and an electric motor (16) as a tensioner
drive, wherein said electric motor is adapted to be coupled to said
belt shaft (12) via said spiral toothing (19).
18. A safety belt retractor according to claim 17, wherein said
spiral toothing (19) is coupled to a drive shaft (34) of said
electric motor (16) via a miter-wheel gearing (17).
19. A safety belt retractor according to claim 18, wherein said
miter-wheel gearing (17) is embodied as a crown wheel gear
mechanism (17).
20. A safety belt retractor according to claim 18, wherein said
spiral toothing (19) is formed on a carrier shaft (18), and wherein
said carrier shaft (18) is connected to the miter-wheel gearing
(17).
21. A safety belt retractor according to claim 17, wherein a
friction-increasing component (25, 26, 28, 30) is disposed between
said counter-bearing (23) and a first thread of said spiral
toothing (19).
22. A safety belt retractor according to claim 21, wherein a spacer
disk (25) of a material having a non-linear coefficient of friction
is provided.
23. A safety belt retractor according to claim 21, a bearing disk
(26) is provided that deforms axially and elastically as load
increases.
24. A safety belt retractor according to claim 21, wherein a
surface of said counter-bearing (23) that faces said spiral
toothing (19) is provided with a conical recess (27), and wherein
disposed on said carrier shaft (18) is a conical friction body (28)
that has a corresponding shape and is made of an elastic
material.
25. A safety belt retractor according to claim 21, wherein a
compress spring (30) is disposed between said counter-bearing (23)
and said spiral toothing (19), and wherein said carrier shaft (18)
and said counter-bearing (23) are provided with latching structures
(31) that interlock during an axial displacement of said carrier
shaft (18).
26. A safety belt retractor according to claim 17, wherein said
spiral toothing (19) is formed on a carrier shaft (18), and wherein
an end face of said carrier shaft is supported against a shank (33)
of a drive shaft (34) of said electric motor (16).
27. A safety belt retractor according to claim 17, wherein a crown
wheel toothing of a crown wheel gear mechanism (17) that is
effective between a drive shaft (34) of said electric motor (16)
and a carrier shaft (18) on which is formed said spiral toothing
(19) has a multi-stage configuration such that during an axial
loading of said carrier shaft (18), a transmission of said crown
wheel gear mechanism (17) changes.
28. A safety belt retractor according to claim 17, wherein said
electric motor (16) is designed with a further performance range
for applying a holding moment to aids in prevention of rotation of
said spiral toothing (19).
29. A safety belt retractor according to claim 28, wherein said
holding moment of said electric motor (16) is adjustable via a
motor control as a function of load acting on said belt shaft (12)
in a belt withdrawal direction.
30. A safety belt retractor according claim 20, wherein said
carrier shaft (18), which carries said spiral toothing (19), on an
end thereof opposite said miter-wheel gearing is held in a first
bearing (21), and wherein in a region between said spiral toothing
(19) and said miter-wheel gearing (17) said carrier shaft (18) is
mounted in an additional thrust bearing (22) that is surrounded by
a bearing housing (23).
31. A safety belt retractor according to claim 30, wherein said
thrust bearing is embodied as a cup-shaped bearing (22).
32. A safety belt retractor according to claim 30, wherein said
bearing housing (23) forms said counter-bearing forms said spiral
toothing (19).
Description
[0001] The invention relates to a safety belt: retractor,
especially for use in motor vehicles, having a blocking system that
is controlled in a vehicle sensitive and/or belt strap sensitive
manner, and also having a tensioning device, which acts on the belt
shaft, for carrying out a reversible pretensioning of the
occupants, whereby the belt shaft can be coupled with an electric
motor, as a tensioner drive, via an interposed gear mechanism.
[0002] A safety belt retractor having the aforementioned features
is known from EP 0 893 313 A2. An electric motor, which is
rotatable not only in the belt unwinding direction but also in the
belt winding direction, can be coupled to the belt shaft of the
belt retractor; from the electric motor, via an interposed gear
mechanism and as a function of certain driving situations,
adjustable torques can be made to act upon the belt shaft. In this
connection, in a predetermined shift position of the gear
mechanism, the torque delivered by the electric motor can be
transferred for tensioning the belt strap on the belt shaft. With
regard to such a tensioning, with the known safety belt retractor a
distinction is made between a so-called pretensioning and a
performance tensioning. Within the scope of the so-call
pretensioning, the strapped-in occupant, upon the occurrence of
speed changes or deceleration values below the threshold for the
triggering of the performance tensioning during an accident, is
pulled via a reduced torque of the electric motor into his normal
sitting position, and belt slack is removed from the safety belt.
Since upon cessation of the change in speed the pretensioning is
concluded, and as a reversible process can again be introduced upon
the occurrence of a further appropriate driving situation, the
strapped-in vehicle occupant has imparted to him a feeling of
active security. If the triggering threshold for the performance
tensioning is exceeded during an accident, the electric motor
operates with an appropriately high torque.
[0003] In conjunction with the pretensioning of the safety belt,
the disadvantageous situation of a self-blocking of the safety belt
can occur in that via the pretensioning all belt slack is taken out
of the safety belt system and the safety belt rests taughtly
against the body of the strapped-in person, whereby depending upon
the driving situation, at the end of the pretensioning process one
cannot preclude that via a slight forward displacement of the body
of the strapped-in occupant, the blocking disk of the blocking
system on the side of the belt retractor will be brought into a
load-transmitting engagement with a housing component. To the
extent that in this blocking position of the blocking disk a return
rotation of the belt shaft in the belt winding direction is
permitted in order to bring the blocking disk out of its
load-transmitting position, there must be effected in a
disadvantageous manner, after conclusion of each reversible
pretensioning, an additional post tensioning with a somewhat
greater force than during the pretensioning, which leads to an
undesired stressing of the system and/or reduction of the wear
comfort for the vehicle occupant.
[0004] It is therefore an object of the invention, with a safety
belt retractor having the aforementioned features, to prevent a
premature activation of the blocking system and to thereby preclude
a self-blocking.
[0005] The realization of this object, including advantageous
embodiments and further developments of the invention, result from
the content of the patent claims that follow this description.
[0006] The basic concept of the invention is that as a gear
mechanism for the connection of the belt shaft to the electric
motor, a worm or spiral toothing is provided that meshes with an
external toothing of the belt shaft, whereby the spiral toothing is
supported against a fixed counter-bearing such that upon the
occurrence of an axial loading of the spiral toothing directed
against the counter-bearing due to a load acting upon the belt
shaft in the belt withdrawal direction, a rotation of the spiral,
for receiving a torque applied by the belt shaft, is prevented via
a support force.
[0007] To the extent that the invention proposes a spiral toothing
as a transmission step for the transfer of the drive movement of
the electric motor to the belt shaft, the inventive concept also
involves, by means of a suitable design of the spiral toothing or
by means of other measures at the conclusion of the tensioning
movement via a rotation of the belt shaft in the belt winding
direction, the prevention of a reversal of the belt shaft, due to a
load acting upon the belt shaft in the belt withdrawal direction,
by preventing the rotation of the spiral toothing in the
appropriate direction of rotation to such an extent that the torque
applied by the belt shaft is absorbed without permitting a reversal
of the belt shaft. This prevents an activation of the blocking
system in an advantageous manner. In this connection, the spiral
toothing is configured in such a way that in the one direction of
rotation of the spiral toothing, namely in the tensioning direction
in conformity with the belt winding direction, the efficiency of
the gear mechanism can be fully utilized, whereas in the opposite
direction of rotation, in other words in conformity with the belt
withdrawal direction, preventing rotation of the spiral is brought
about in that the spiral toothing is supported against a fixed
counter-bearing in such a way that with an axial loading of the
spiral toothing directed against the counter-bearing due to the
belt shaft, the prevention of the rotation of the spiral is brought
about by the support force. To the extent that at the conclusion of
pretensioning of the belt shaft a torque acts upon the spiral
toothing, this leads to an axial loading of the spiral toothing
that can be converted into an appropriately acting support
force.
[0008] To the extent that pursuant to EP 0 893 313 A2 a performance
tensioning is also provided in the event of a crash, the use of an
electric motor having a gear mechanism embodied as a spiral
toothing is also not precluded for the performance tensioning to
the extent that the electric motor is designed to apply an
appropriate torque. However, the performance tensioning can also be
effected via another tensioner drive that acts upon the belt shaft,
or via a tensioner, for example a buckle tensioner, that is
disposed in some other region of the safety belt system.
[0009] Pursuant to one embodiment of the invention, the spiral
toothing is coupled via a miter-wheel gearing to a drive shaft of
the electric motor. This involves an especially space-saving manner
of construction of the safety belt retractor, because the electric
motor can be disposed directly over the shaft portion of the safety
belt retractor.
[0010] To the extent that pursuant to one embodiment of the
invention a crown wheel gear mechanism is provided as a miter-wheel
gearing, this results in production advantages. Alternatively,
however, the arrangement of a bevel gearing is also conceivable,
whereby the tolerance zone positions of a bevel gearing can be
controlled only at great expense during mass production. In so far,
however, the use of a bevel gearing to realize the invention is not
precluded.
[0011] Pursuant to an embodiment of the invention, the spiral
toothing is formed on a carrier shaft, and the carrier shaft is
connected to the miter-wheel gearing.
[0012] The prevention of the spiral rotation can be carried out
pursuant to an embodiment of the invention in that disposed between
the counter-bearing and the first land or thread of the spiral
toothing is a component that increases friction. The
friction-increasing component can, pursuant to an embodiment of the
invention, be embodied as an intermediate or spacer disk of a
material having a non-linear coefficient of friction; for example
elastomers are in particular available that as the effect of force
increases, an exponentially increasing frictional force occurs.
[0013] Alternatively, a bearing disk can be provided that deforms
axially and elastically as the load increases, so that the first
thread of the spiral toothing, under the effect of the support
force, runs on a larger diameter in the bearing than without the,
effect of the support force.
[0014] Pursuant to a further embodiment of the invention, the
surface of the gear mechanism that faces the spiral toothing is
provided with a conical recess, and disposed on the carrier shaft
is the conical friction body that is made of an elastic material
and has a corresponding shape; in this embodiment, the increase of
the friction force is effected by the conical shape of the recess
and of the friction body, as well as by the elastic
deformation.
[0015] Pursuant to a further alternative, a compression spring can
be disposed between gear mechanism housing and spiral toothing, and
carrier shaft and gear mechanism housing are provided with latching
structures that interengage upon axial displacement of the carrier
shaft; instead of the compression spring, a tension spring can also
be disposed at the appropriate end of the carrier shaft.
[0016] Pursuant to an embodiment of the invention, to achieve the
prevention of the spiral rotation, the end face of the carrier
shaft is supported against a shank of the drive shaft of the
electric motor, so that in this way an appropriate braking moment
is produced.
[0017] Alternatively, the crown wheel toothing of the crown wheel
gear mechanism, which is effective between drive shaft of the
electric motor and the carrier shaft for the spiral toothing, can
have a multi-stage configuration such that with an axial loading of
the carrier shaft, the transmission of the crown wheel gear
mechanism changes, thus producing a braking moment for the rotation
of the carrier shaft with the spiral toothing.
[0018] To the extent that the structural measures for preventing
the spiral rotation are not yet adequate, to further absorb the
torque emitted from the belt shaft, the electric motor can be
designed with a further performance range for applying a holding
moment that serves to aid in the prevention of the spiral rotation,
so that in additional to the prevention of the spiral rotation by
the electric motor, a blocking of the reversal of the spiral
toothing in conformity with the withdrawal direction of the belt
strap is applied via an appropriate holding moment.
[0019] Since, however, with the measures for the prevention of the
reversal of the spiral toothing already adequate moments can be
absorbed, the design of the electric motor with a performance range
that serves for producing a holding moment additionally presents
the possibility, during a force-limiting phase that is,
additionally provided with the aforementioned safety belt
retractor, of establishing a controlled holding moment and hence of
realizing an adaptive force limitation, for example together with a
single stage or also multi-stage torsion rod. For this purpose, the
holding moment of the electric motor can be adjustable by the motor
control as a function of the load that acts on the belt shaft in
the belt withdrawal direction.
[0020] With regard to the arrangement of the spiral toothing,
pursuant to an embodiment of the invention the carrier shaft that
carries the spiral toothing is held in a bearing at its end::.that
is opposite the miter-wheel gearing, is mounted in an additional
axial or thrust bearing that is surrounded by a bearing
housing.
[0021] Expedient in this connection is the embodiment of the thrust
bearing as a cup-shaped bearing because in so doing a deflection of
the carrier shaft out of the axial starting position by a small
angle is made possible, whereby again an increase of the gear
mechanism friction in the context of the invention can be
established.
[0022] To the extent that the mounting of the carrier shaft in an
additional bearing housing is realized, it is expediently provided
pursuant to an embodiment of the invention that the bearing housing
form the counter-bearing for the spiral toothing.
[0023] Illustrated in the drawing are embodiments of the invention,
which will be described subsequently. The drawing shows:
[0024] FIG. 1 an overall view of a safety belt retractor having a
pretensioning device,
[0025] FIG. 2 the safety belt retractor of FIG. 1 in a side view of
its tensioner side with pretensioning device,
[0026] FIG. 3 a side view of the pretensioning device of FIGS. 1
and 2 in a detailed illustration,
[0027] FIG. 4 a first embodiment of the prevention of the spiral
rotation by support of the spiral toothing against the bearing
housing in a diagrammatic illustration,
[0028] FIG. 5 the subject matter of FIG. 4 in a further
embodiment,
[0029] FIG. 6 the subject matter of FIG. 4 in a further
embodiment,
[0030] FIG. 7 the subject matter of FIG. 4 in a further
embodiment,
[0031] FIG. 8 the subject matter of FIG. 4 in a further
embodiment,
[0032] FIG. 9 a diagrammatic illustration of the prevention of the
spiral rotation by utilization of the radial forces in the bearings
of the carrier shaft,
[0033] FIG. 10 the prevention of the spiral rotation by support of
the carrier shaft relative to the drive shaft of the electric
motor,
[0034] FIG. 11 the prevention of the spiral rotation by support of
the carrier shaft in the crown wheel gear mechanism.
[0035] The safety belt retractor 10 seen in FIG. 1 has a U-shaped
housing 11, in the U-legs of which a belt shaft 12 is mounted in a
known manner. The belt shaft 12 is influenced by the action of a
winding spring that is disposed in a spring cartridge 13 and which,
after unwinding of the non-illustrated belt strap from the belt
shaft 12, sees to it that the belt strap is rewound onto the belt
shaft 12 when the safety belt is taken off. On the system side of
the housing 11, which is not further illustrated in FIG. 1 and
which is opposite the mounting of the spring cartridge 13, there is
disposed, below the protective cover 14, the blocking system of the
belt retractor that is not illustrated in detail and to this extent
is presumed to be known; the function of the blocking system is to
be controlled by control systems that act in a belt strap sensitive
and/or vehicle sensitive manner.
[0036] On that side of the housing that is provided with the spring
cartridge 13 a pretensioner housing is additionally indicated by
the reference numeral 15; an electric motor 16, as a tensioner
drive, is associated with the pretensioner housing.
[0037] As can be seen in greater detail from FIGS. 2 and 3, the
drive shaft 34 of the electric motor 16 acts via a crown wheel gear
mechanism 17 upon a carrier shaft 18 that is disposed in a
tangential orientation relative to the belt shaft 12; disposed on
the carrier shaft is a worm or spiral toothing 19 that meshes with
an external toothing 20 disposed on the belt shaft 12. The carrier
shaft 18 is mounted in an end bearing 21 as well as in a cup-shaped
bearing 22 that is disposed between the spiral toothing 19 and the
crown wheel gear mechanism 17, whereby the cup-shaped bearing 22 is
disposed in a bearing housing 23 that is not further illustrated in
FIGS. 2 and 3, yet can be seen from FIGS. 4 to 8.
[0038] In the illustrated embodiment, the spiral toothing 19 is not
embodied as a self-blocking spiral gear, so that by means of
additional structural measures care is taken that with a load that
at the conclusion of a pretensioning acts upon the belt shaft 12,
in the belt withdrawal direction (arrow 42) the axial force (arrow
40) that is applied by the belt shaft 12 onto the spiral toothing
19, and hence onto the carrier shaft 18, is converted into a
friction-increasing support force, so that in this way an arresting
or preventing of the rotational movement of the spiral toothing 19
is brought about.
[0039] Embodiments for effecting the increase of the frictional
force are primarily illustrated in FIGS. 4 to 8, whereby with the
embodiment illustrated in FIG. 4 an intermediate or spacer disk 25,
which is made of a material having a non-linear frictional
coefficient, is disposed between the first land or thread of the
spiral toothing 19 and the bearing housing 23 of the cup-shaped
bearing 22. This material can be a suitable elastomer with which,
as the axial force increases, the frictional force increases
exponentially.
[0040] The bearing disk 26 that pursuant to FIG. 5 is disposed
between the spiral toothing 19 and the bearing housing 23 acts in a
similar manner, according to which under the effect of the axial
force (arrow 40) the spiral toothing runs on a larger diameter in
the bearing than under normal load.
[0041] With the embodiment illustrated in FIG. 6, the bearing
housing 23 is provided with a conical recess 27 into which engages
a conical friction body 28 that has a corresponding shape and is
made of an elastic material, so that due to the conical shape, as
well as the elastic deformation of the friction body 28, the
frictional force between the spiral toothing 19 and the bearing
housing 23 is increased.
[0042] In the same manner, in the embodiment illustrated in FIG. 7,
there is disposed between the spiral toothing 19 and the bearing
housing 23 a sheet-like disk 29 that under the effect of force is
elastically deformed, so that the frictional surface is increased
and the frictional resistance increases. Alternatively, it would
also be possible to realize a so-called "Knackfrosch" approach.
[0043] With the embodiment illustrated in FIG. 8, there is disposed
between the bearing housing 23 and the spiral toothing 19 a
compression spring 30, whereby in addition a positive connection
means 31 is provided between the bearing housing 23 and the first
land or thread of the spiral toothing 19, so that upon the
influence of force (arrow 40) the spring 30 is compressed until the
positive connection means 31 interlock.
[0044] FIG. 9 illustrates the possibility of increasing the
frictional force between the spiral toothing 19 and the external
toothing 20 of the belt shaft 12 in that with the influence of an
axial force upon the carrier shaft 18, the latter tilts by a small
angle 32 in the cup-shaped bearing 22.
[0045] FIG. 10 illustrates the possibility that the end face of the
carrier shaft 18 is supported upon a shank 33 of the drive shaft 34
of the electric motor 16, thereby producing an appropriate braking
moment.
[0046] FIG. 11 indicates that the crown wheel toothing of the crown
wheel gear mechanism 17 that is effective between the drive shaft
34 of the electric motor 16 and the carrier shaft 18 has a
multi-stage configuration such that with an axial loading of the
carrier shaft (arrow 40), the transmission of the crown wheel gear
mechanism 17 changes from rapid to slow, whereby alternatively or
in addition an impairment of the toothing efficiency in the stages
of the crown wheel gear mechanism 17 can be provided.
[0047] The features of the subject matter of these documents
disclosed in the preceding description, the patent claims, the
abstract and the drawing can be important individually as well as
in any combination with one another for realizing the various
embodiments of the invention.
* * * * *