Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2002-07-09
2004-03-02
Walsh, Donald P. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
C242S379100, C280S806000, C280S805000, C297S478000
Reexamination Certificate
active
06698678
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a webbing retractor. In particular, the present invention relates to a webbing retractor which, when pulling-out of a webbing is to be impeded, allows the webbing to be pulled out to a certain extent such that energy of an inertial force can be absorbed.
2. Description of the Related Art
In a webbing retractor, when the vehicle rapidly decelerates, rotation of a spool (a take-up shaft) in a direction of pulling-out a webbing is locked, such that pulling-out of the webbing is impeded. An example of the lock mechanism is a structure in which a lock device is disposed in a vicinity of a device frame at one end side of the spool. Due to the lock device operating when the vehicle rapidly decelerates, rotation of the spool in the webbing pull-out direction is impeded.
Further, in such a webbing retractor, at the time when pulling-out of the webbing is to be impeded, pulling-out of a predetermined amount of the webbing is allowed so as to absorb the energy of the inertial force of the vehicle occupant. An example of such an energy absorbing mechanism is a structure provided with, for example, a spool and a torsion bar which is coaxial with the spool. Generally, the torsion bar is connected to a shaft sensor, whose one end portion is connected to the spool and whose other end portion is connected to a lock device, such that the torsion bar, the shaft sensor, and the spool do not rotate relative to one another. Usually, the spool and the shaft sensor rotate integrally via the torsion bar. However, in a state in which rotation of the shaft sensor in the webbing pull-out direction is impeded when the vehicle rapidly decelerates, the spool rotates in the webbing pull-out direction with respect to the shaft sensor, due to the tensile force of the webbing. At this time, the torsion bar is twisted, the energy applied to the webbing is absorbed, and a predetermined amount of rotation of the spool is permitted. The absorbed energy is determined by the product of the load applied to the webbing (the force limiter load) and the webbing pull-out amount (the amount of rotation of the spool). In the webbing retractor, the force limiter load and the allowable amount of rotation of the spool (the twisting limit of the torsion bar) are given.
However, in such a conventional webbing retractor, the force limiter load at the time of energy absorption is a value which is determined exclusively by the values of the properties of the material of the torsion bar, and the dimensions and configuration of the torsion bar and the like. Only a value which is constant from the start of operation to the end thereof has been able to be used as the value of the force limiter load at the time of energy absorption.
SUMMARY OF THE INVENTION
In view of the aforementioned, an object of the present invention is to provide a webbing retractor in which, with a simple structure, a force limiter load can be changed at a predetermined timing, and the inertial energy of a vehicle occupant can be absorbed better.
The webbing retractor of the present invention comprises: a spool which is tubular and onto which a webbing is taken-up and from which a webbing is pulled-out; a shaft sensor provided at one end side of the spool, coaxially with the spool and so as to be able to rotate relative to the spool; a lock device connected to the shaft sensor, and when a predetermined acceleration is sensed, the lock device engages with a frame so as to impede rotation of the shaft sensor in a webbing pull-out direction; a torsion bar provided within the spool and coaxially with the spool, and one end of the torsion bar is connected to the spool and another end of the torsion bar is connected to the shaft sensor, and the torsion bar is usually rotated integrally with the shaft sensor, and in a state in which rotation of the shaft sensor in the webbing pull-out direction is impeded by the lock device, the torsion bar rotates the spool in the webbing pull-out direction relative to the shaft sensor, while being twisted due to a webbing tensile force; and a wire spanning between the shaft sensor and the spool and inserted movably within the spool, and in the state in which rotation of the shaft sensor in the webbing pull-out direction is impeded by the lock device, as the spool rotates until relative rotation of the spool with respect to the shaft sensor has reached a predetermined amount, the wire is rubbed at exit portion of the spool and imparts a rubbing force which offers resistance to the relative rotation, wherein the webbing retractor includes a force limiting device which, when pulling-out of the wire from the spool is being completed while the wire is being rubbed, limits the rubbing force at the time the pulling-out of the wire is being completed such that the rubbing force does not exceed rubbing force therebefore.
The wire encompasses, for example, rod-shaped members which do not easily deform, i.e., do not deform due to their own weight or by human force.
In the webbing retractor of the present invention, the spool and the shaft sensor are connected via the torsion bar. Usually, the spool, the shaft sensor and the torsion bar rotate integrally, and the webbing can be freely taken-up or pulled-out.
Here, when a predetermined acceleration (or deceleration) is sensed at the time when the vehicle rapidly decelerates such as, for example, the time of a vehicle collision or the like, the lock device operates such that rotation of the shaft sensor in the webbing pull-out direction is impeded. At this time, the webbing tensile force acts as torque, in the webbing pull-out direction, on the torsion bar via the spool. Thus, the torsion bar is twisted, and while the load applied to (the vehicle occupant via) the webbing is maintained constant (i.e., while a constant force limiter load is applied), the spool is rotated with respect to the shaft sensor in the webbing pull-out direction, and the webbing is pulled-out. The absorption of energy by the torsion bar is achieved.
When the torsion bar is twisted and the spool rotates relatively with respect to the shaft sensor, as the spool rotates, the wire is rubbed at the exit portion of the spool, and while being taken-up onto the side surface of the spool, imparts a load which offers resistance to this relative rotation, during the period of time until the relative rotation of the spool reaches a predetermined amount. Accordingly, in addition to the twisting load of the torsion bar, the rubbing force of the wire is applied to (the vehicle occupant via) the webbing as force limiter load. Namely, a force limiter load, which is greater than the force limiter load obtained only by the twisting load of the torsion bar, is obtained. The webbing pull-out speed (i.e., the rotational speed of the spool) can be kept low, and appropriate energy absorption can be achieved.
Further, when the spool rotates by a predetermined amount with respect to the shaft sensor, the entire wire, which spans between the shaft sensor and the spool, is pulled-out completely from the spool (i.e., the entire length of the wire is taken-up), and the imparting of load due to the rubbing of the wire is cancelled. Thus, only the twisting load of the torsion bar is applied to (the vehicle occupant via) the webbing as force limiter load. Namely, the force limiter load becomes lower than the initial force limiter load at the time when the energy absorption started.
In this way, in the webbing retractor of the present invention, the force limiter load can be changed at a predetermined timing. Namely, in the initial stages of rapid deceleration of a vehicle, the rubbing force due to the wire is added such that the energy absorption amount per unit time becomes large, and the pulled-out amount of the webbing (the amount of movement of the vehicle occupant) is suppressed. After a predetermined absorption of energy, by decreasing the energy absorption amount per unit time, the load applied to the vehicle occupant can be decreased. This is a desirable characte
Hori Seiji
Nagata Tomonori
Kabushiki Kaisha Tokai-Rika-Denki-Seisakusho
Miller Jonathan R
Nixon & Peabody LLP
Walsh Donald P.
LandOfFree
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