Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2000-12-05
2004-07-13
Walsh, Donald P. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
Reexamination Certificate
active
06761328
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a seat belt retractor for a webbing that permits the webbing to be retracted and withdrawn. More particularly, the present invention relates to a seat belt retractor with a torsion bar for absorbing load exerted on a webbing when an occupant puts on the webbing and the webbing is stopped from being withdrawn in the event of emergency such as a vehicle collision at which large deceleration is exerted on the vehicle.
Conventionally, a seat belt device installed in a vehicle such as an automobile prevents an occupant from being thrown out of a vehicle seat by restraining the occupant with a webbing. The seat belt protects the occupant in the event of emergency such as mentioned above.
A typical seat belt device is provided with a seat belt retractor for accommodating a webbing. When not used, the webbing is fully wound on a reel of the retractor. When an occupant puts on the webbing, the seat belt is withdrawn to extend across the occupant. The seat belt retractor includes a locking mechanism that is activated in the event of emergency as mentioned above to stop the rotation of the reel in an unwinding direction, thereby preventing the webbing from being withdrawn. Therefore, the seat belt webbing can securely restrain and protect the occupant.
However, conventional seat belt retractors being used in seat belt devices have a drawback or problem. That is, when the webbing restrains and protects the occupant, a large deceleration is exerted on the vehicle so that the occupant tends to move forward due to a large inertia force. Accordingly, a large load is exerted on the webbing and the occupant receives a large impact load from the webbing. Thus, there remains a need to absorb the impact load to reduce the discomfort for the occupant. Though this impact load is not so severe for the occupant, it is better to absorb the impact load.
FIG. 8
is a vertical sectional view showing an example of a conventional seat belt retractor
1
including a torsion bar. As shown in the drawing, the seat belt retractor, includes a U-like frame
2
, a webbing
3
, a reel
4
which is rotatably supported between side walls of the U-like frame
2
and on which the webbing
3
is wound, a deceleration sensing means
5
which detects a large deceleration of the vehicle occurred in case of emergency mentioned above, a locking mechanism
6
which is activated by the deceleration sensing means
5
to prevent the reel from rotating in the webbing unwinding direction, a torsion bar
7
loosely fitted and inserted in the axial direction in the center of the reel
4
and which rotatably connects the reel
4
and the locking mechanism
6
, a spring means
8
for always biasing the reel
4
in the webbing winding direction through a bush
10
by the spring force of a spiral spring
9
, a pretensioner
11
which is activated in the case of emergency mentioned above for producing webbing winding torque, and a bush
12
for transmitting the webbing winding torque of the pretensioner
11
to the reel
4
.
The locking mechanism
6
include a pawl holder
14
which rotates together with a first torque transmitting portion
17
of the torsion bar
7
. The holder
14
pivotally holds the pawl
13
and also includes a lock gear
6
a
which rotates together with the torsion bar
7
during normal operation. The lock gear
6
a
stops in an emergency corresponding to the activation of the deceleration sensing means
5
to produce rotation relative to the torsion bar
7
and engages the pawl
13
with one of internal teeth
19
of the side wall of the frame
2
, thereby stopping the rotation of the pawl holder
14
and the rotation of the reel
4
in the webbing unwinding direction. The pawl holder
14
has an external thread portion
15
that includes a nut-like stopper member
16
which rotates together with the reel
4
and is screwed into the thread portion
15
.
The torsion bar
7
includes the first torque transmitting portion
17
which is fitted to the pawl holder
14
not allowing relative rotation therebetween, and a second torque transmitting portion
18
which is fitted to the reel
4
not allowing relative rotation therebetween.
The reel
4
is always biased by the spring force of the spring means
8
in the webbing winding direction through the bush
10
, the torsion bar
7
, the second torque transmitting portion
18
of the torsion bar
7
, and the bush
12
. The webbing winding torque produced by the pretensioner
11
is transmitted to the reel
4
through the bush
12
whereby the reel
4
winds up the webbing
3
a predetermined amount.
In the conventional seat belt retractor
1
having the aforementioned structure, the webbing
3
is fully wound up by the biasing force of the spring means
8
when not being used by a vehicle passenger. As the webbing
3
is withdrawn at a normal speed for putting on, the reel
4
rotates in the webbing unwinding direction so that the webbing
3
is smoothly withdrawn. After a tongue (not shown) slidably fitted to the webbing
3
is inserted into and engaged with a buckle fixed to a vehicle body, the excess amount of the webbing
3
is wound back onto the reel
4
by the biasing force of the spring means
8
until the webbing
3
is fitted to the occupant's body without excess stress.
In an emergency, such as mentioned above, the webbing winding torque produced by the pretensioner
11
is transmitted to the reel
4
so that the reel
4
winds up the webbing
3
for a predetermined amount, in order to strongly restrain the occupant. The deceleration sensing means
5
is activated by a large deceleration produced by the emergency condition to activate the locking mechanism
6
. The activation of the deceleration sensing means
5
prevents the rotation of the lock gear
6
a
in the webbing unwinding direction. In addition, the pawl
13
of the locking mechanism
6
pivots and engages one of the internal teeth
19
of the side wall of the frame
2
so as to stop the rotation of the pawl holder
14
. As a result of this, the reel
4
rotates in the webbing unwinding direction relative to the pawl holder
14
while the torsion bar
7
is twisted. By this twisting of the torsion bar
7
, the load applied to the webbing
3
is limited, thus absorbing the impact on the occupant.
Since the reel
4
rotates relative to the paw holder
14
, the stopper member
16
rotates relative to the external thread portion
15
which is screwed into the stopper member
16
, whereby the stopper member
16
moves toward the pawl holder
14
. When stopper member
16
comes into contact with the pawl holder
14
, the stopper member
16
is prevented from further rotation. As a result, the reel
4
is also prevented from rotating and the torsion bar
7
is prevented from being twisted. In this manner, the webbing
3
is stopped from being withdrawn whereby the occupant is restrained by the webbing
3
. Thus, the movement of the stopper member
16
defines the maximum allowable twisting deformation of the torsion bar
7
. Through adjustment the EA (“Energy Absorbing”) stroke as a rotatable stroke of the reel
4
relative to the pawl holder
14
can be freely set.
In addition, in the conventional seat belt retractor
1
, the pawl holder
14
of the locking mechanism
6
rotates in the webbing unwinding direction relative to the lock gear
6
a
when the webbing is rapidly withdrawn. Also in this case, the pawl
13
of the locking mechanism
6
engages one of the internal teeth
19
of the side wall of the frame
2
so as to stop the rotation of the pawl holder
14
in the same manner as mentioned above. Therefore, the reel
4
is prevented from rotating in the unwinding direction through the torsion bar
7
, thus stopping the withdrawal of the webbing.
In the conventional seat belt retractor
1
, the torsion bar
7
extends to penetrate the bush
12
. The bush
12
is sandwiched between the second torque transmitting portion
18
of the torsion bar
7
and an E-ring
20
fitted to a groove of the torsion bar
7
whereby the movement of the t
Kanamori Yasushi
Mishina Joji
Shiotani Masahiro
Rodriguez Joseph C
Takata Corporation
Walsh Donald P.
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