Webbing retractor

Details Webbing retractor Webbing retractor

2001-07-09

2003-02-25

Matecki, Kathy (Department: 3654)

Winding, tensioning, or guiding

Reeling device

With spring motor

C242S383500, C242S384600, C280S806000, C297S479000

Reexamination Certificate

active

06523771

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a webbing retractor which can impede pulling-out of a webbing at a time when a vehicle rapidly decelerates or the like, and in particular, to a webbing retractor which, after impeding pulling-out of a webbing, enables the webbing to be pulled out again.
2. Description of the Related Art
Generally, in a webbing retractor, a webbing is wound in a roll form on a hollow cylindrical spool supported at a frame which is formed in a substantial U-shape as seen in plan view and which is fixed to a vehicle. Usually, the webbing can be freely taken-up or pulled-out due to the spool rotating freely. Further, in the webbing retractor, a WSIR (webbing sensitive inertia reel) or a VSIR (vehicle sensitive inertia reel) is utilized in order to impede pulling-out of the webbing when a rapid deceleration of the vehicle or a rapid pulling-out of the webbing is sensed.
Hereinafter, a conventional webbing retractor equipped with a WSIR and a VSIR will be described on the basis of
FIGS. 10A and 10B
.
In
FIGS. 10A and 10B
, a webbing retractor
100
is shown in a side view seen from a rotational axis direction of a spool
102
. The webbing retractor
100
is formed to include the spool
102
; a lock plate
104
which is supported at the spool
102
so as to be freely swingable and which can mesh with ratchet teeth
106
provided at a frame (not shown); a V gear
108
which is provided coaxially with the spool
102
, and when relative rotation with respect to the spool
102
arises, the V gear
108
guides the lock plate
104
to a position at which engagement with the ratchet teeth
106
is possible; a W sensor portion
110
which forms the WSIR; and a V sensor portion
120
which forms the VSIR.
In this webbing retractor
100
, usually, the spool
102
and the V gear
108
rotate integrally. Thus, the webbing can be freely taken-up and pulled-out (the state shown in
FIG. 10A
) without the lock plate
104
engaging the ratchet teeth
106
.
On the other hand, when the webbing is pulled-out rapidly, an inertia plate
116
of the W sensor portion
110
cannot follow the rotation of the V gear
108
(the spool
102
) in the webbing pull-out direction (direction A in FIGS.
10
A and
10
B), and an inertial delay arises. As a result, relative rotation in the webbing take-up direction arises between the inertia plate
116
and the V gear
108
. A pawl
112
which abuts the inertia plate
116
is swung in the webbing take-up direction and engages with internal teeth
118
fixed to the frame, and rotation of the V gear
108
in the webbing pull-out direction is impeded (the state shown in FIG.
10
B).
Here, an engagement surface
118
a
of the internal tooth
118
, which engagement surface
118
a
engages with the pawl
112
, stands substantially perpendicular with respect to direction A. As a result, the tooth tip of the pawl
112
which engages with the engagement surface
118
a
is reliably guided to the tooth bottom of the internal tooth
118
. A phase offset by which the pawl
112
is guided to the next internal tooth
118
and which is due to deficient engagement, and damage to the W sensor portion
110
accompanying such phase offset, are prevented.
When the rotation of the V gear
108
in the webbing pull-out direction is impeded, relative rotation is generated between the V gear
108
and the spool
102
which continues to rotate along with the pulling-out of the webbing. As a result, the lock plate
104
, which has a guide pin
104
a
which is inserted into a guide hole
108
a
formed in the V gear
108
, does not follow the rotation of the spool
102
, and is guided by the guide hole
108
a
via the guide pin
104
a
, and reaches a position at which engagement with the ratchet tooth
106
is possible (a position at which the lock plate
104
and the tooth tip of the ratchet tooth
106
engage). The lock plate
104
, which has been guided to the position at which engagement with the ratchet tooth
106
is possible, is guided to the tooth bottom of the ratchet tooth
106
by the configuration of the ratchet tooth
106
, and is set in a locked state. In other words, the lock plate
104
is self-locked, and rotation of the spool
102
in the webbing pull-out direction is impeded.
At the time of this self-locking, the lock plate
104
moves toward the tooth bottom of the ratchet tooth
106
(i.e., toward the left in FIGS.
10
A and
10
B). Accompanying this movement of the lock plate
104
, the guide pin
104
a
pushes the guide hole
108
a
side wall of the V gear
108
toward the left in
FIG. 10
, and due to this pushing moment, the V gear
108
rotates in the webbing take-up direction (direction B in FIGS.
10
A and
10
B). When the V gear
108
rotates by a predetermined amount in direction B, the engagement of the pawl
112
and the internal tooth
118
is cancelled. The pawl
112
, which is urged to swing in direction A by being connected to one end of a spring
114
whose other end is fixed to the V gear
108
, returns to its original position. In other words, the operation of the W sensor portion
110
is cancelled.
In this way, in the process in which the pulling-out of the webbing is impeded, operation of the W sensor portion
110
is cancelled. As a result, thereafter, pulling-out of the webbing is again possible.
In order to cancel the operation of the W sensor portion
110
, a W sensor cancel angle &agr; shown in
FIG. 10B
must be smaller than the angle of rotation in direction B of the V gear
108
(hereinafter called the V gear reverse rotation angle). The W sensor cancel angle &agr; is an angle necessary for a peak portion C of the internal tooth
118
, with which the pawl
112
is engaged, to move relatively with respect to the V gear
108
(the pawl
102
) to an intersection point D of a swinging locus a of the tooth tip of the pawl
112
and a moving locus b of the peak portion of the internal tooth
118
(i.e., an angle necessary for the peak portion C to move relatively to a position at which no internal tooth
118
exists on the locus of swinging of the tooth tip of the pawl
112
). Further, although not illustrated, after the V sensor portion
120
operates, even at the time when engagement of a sensor lever
122
and an external tooth
108
b
formed at the outer peripheral surface of the V gear
108
is released, the V sensor cancel angle must be smaller than the V gear reverse rotation angle.
However, at the conventional webbing retractor
100
such as described above, in order to prevent a phase offset at the time of operation of the W sensor portion
110
, the engagement surface
118
a
of the internal tooth
118
must stand substantially perpendicular with respect to direction A, and the sensor cancel angle &agr; cannot be made smaller by any more than a predetermined value. Further, there is dispersion in the dimensions of the internal teeth
118
within the predetermined range of dimensional accuracy, and due to this dispersion in dimensions, the values of the W sensor cancel angles &agr; are not constant (the values of the W sensor cancel angles &agr; vary depending on which internal tooth
118
the pawl
12
is engaged with). Further, the value of the W sensor cancel angle &agr; also depends on the accuracy of assembly of the respective parts.
Thus, depending on the position of the internal tooth
118
with which the pawl
112
is engaged, there are cases in which the sensor cancel angle &agr; is greater than the V gear reverse rotation angle and the operation of the W sensor portion
110
cannot be cancelled. Further, in order to make the maximum value of the W sensor cancel angle &agr; always smaller than the V gear reverse rotation angle, excessive dimensional precision and assembly precision are required. Thus, a problem arises in that machinability and assemblability are poor, and costs increase. Further, there are of course similar problems with the V sensor portion
120
as well.
SUMMARY OF THE INVENTION
In view of the aforementioned, an object of the present invention is t

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