Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2000-02-14
2002-03-12
Walsh, Donald P. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
C242S379100, C242S383200, C242S383500
Reexamination Certificate
active
06354528
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a webbing retractor in a seat belt system for restraining an occupant in a vehicle with a webbing belt.
2. Description of the Related Art
A webbing retractor constituting a main part of a so-called seat belt system for restraining an occupant in a vehicle with an elongated belt-shaped webbing belt basically comprises: a take-up shaft with which one end of the webbing belt is engaged; a frame for supporting the take-up shaft; and urging means such as a spiral coil spring or the like, for urging the take-up shaft in the direction of winding the webbing belt.
In addition to the above structure, an ordinary webbing retractor is provided with a lock device for locking the take-up shaft when a vehicle enters an abrupt deceleration state, to thereby resist a force of an occupant's body, which moves toward the front of the vehicle due to inertia in the abrupt deceleration state, acting to pull out the webbing belt, and for improving the restraining force of the webbing belt; and a pretensioner for forcibly imparting rotation force in the take-up direction to the take-up shaft in the abrupt deceleration state of the vehicle.
Since the above-described conventional webbing retractor has a large number of parts to be used, the apparatus becomes large as a whole. Below is a detailed description of the above-described lock device and pretensioner.
The lock device ordinarily comprises a substantially circular V gear having ratchet teeth formed on the outer peripheral portion thereof. The V gear is mechanically connected to the take-up shaft via a torsion spring or the like, and follows the take-up shaft for rotation. A pair of lock plates are held by engagement on the side along the V gear and the take-up shaft, and when relative rotation is caused between the take-up shaft and the V gear, each lock plate moves outward in the radial direction of rotation of the take-up shaft. Each lock plate is formed with ratchet teeth, and when moved outward in the radial direction of rotation of the take-up shaft, meshes with the internal teeth of the ratchet hole formed in one of a pair of leg plates constituting a frame. Moreover, an acceleration sensor having an inertia ball is disposed in the direction that is outward in the radial direction with respect to the V gear (ordinarily, on the lower side). Due to the inertia ball rolling at the time of abrupt deceleration of the vehicle, an engagement pawl of the acceleration sensor engages with the ratchet teeth to restrict the rotation of the V gear. That is, during the abrupt deceleration state of the vehicle, the occupant's body tends to move in the direction the vehicle is travelling due to inertia. At this time, the occupant's body pulls out the webbing belt to rotate the take-up shaft. But since the V gear is locked by the engagement paw, a relative rotation is caused between the take-up shaft and the V gear, and each lock plate moves outward in the radial direction of rotation of the take-up shaft, and the ratchet teeth of each lock plate meshes with the internal teeth of the ratchet hole to restrict the rotation of the take-up shaft.
With such a conventional lock device, two (a pair of) lock plates are used to obtain mechanical strength sufficient for corresponding to rotation of the take-up shaft in the abrupt deceleration state of the vehicle, which is one factor leading to an increase in the number of parts.
On the other hand, the pretensioner comprises a pinion connected to one end of the take-up shaft via a one-way clutch, and a rack bar meshable with the pinion. The rack bar is formed integrally with a piston housed in a cylinder, moves with increase in the internal pressure of the cylinder to thereby mesh with the pinion and forcibly rotates the take-up shaft in the take-up direction via the one-way clutch. A gas generator is attached to the cylinder, which ignites a gas generating agent in the gas generator when an acceleration sensor other than the acceleration sensor of the above-described lock device detects the abrupt deceleration state of the vehicle to thereby generate gas instantaneously, and to move the piston by gas pressure.
The take-up shaft-side shaft portion of the above-described pinion or the pinion-side shaft portion of the one-way clutch is ordinarily rotatably supported by means of a bearing portion provided in the housing formed by a metal plate or the like, the bearing portion being brought into face contact with the outer peripheral face along the outer peripheral direction of the shaft portion. Therefore, for example, when the rack bar meshes with the pinion, the take-up shaft becomes eccentric, and in this state, when the take-up shaft is made to rotate, the take-up shaft rotates in the state of being pressed against the inner peripheral portion of the bearing. Hence, the friction resistance becomes large. By this friction resistance, the force by which the pretensioner forcibly rotates the take-up shaft via the rack bar and the pinion is converted into heat energy, hence the portion of the force actually leading to rotation of the take-up shaft decreases. Particularly, when synthetic resin material having a lower rigidity than the metal material forming the take-up shaft is used for the bearing portion so as to decrease the weight, an inner peripheral portion of the bearing portion is plastically deformed due to the above-described friction resistance. Hence, the inner peripheral face of the bearing portion becomes rough, to thereby further increase the friction resistance.
As described above, with the webbing retractor provided with a conventional pretensioner, the decrease of force rotating the take-up shaft of the pretensioner due to the friction resistance must be taken into consideration in advance, and the quantity of the gas to be generated should be increased for that amount. Therefore, the pretensioner is made large, and the webbing retractor increases in size accordingly.
In view of the above circumstances, it is an object of the present invention to obtain an inexpensive webbing retractor by making the pretensioner and the lock device small and reducing the number of parts.
SUMMARY OF THE INVENTION
To attain the above object, a first aspect of the present invention is a webbing retractor for use with a webbing belt having opposite ends, the webbing retractor comprising a cylindrical take-up shaft at which one end of a webbing belt is retained a lock device for restricting rotation of the take-up shaft in a direction for pulling out the webbing belt, during abrupt deceleration of a vehicle and a pretensioner for forcibly rotating the take-up shaft in the take-up direction opposite to the pulling-out direction during abrupt deceleration of the vehicle wherein the lock device includes a frame having a pair of leg plates opposite to each other along an axial direction of the take-up shaft, one of the pair of leg plates being formed with a ratchet hole whose inner peripheral portion serves as internal ratchet teeth, the leg plates having sides, a lock base provided coaxially and relatively rotatable with respect to the take-up shaft, in a vicinity of the one of the pair of leg plates a lock plate having external teeth meshable with the ratchet teeth, which is substantially integrally held by the lock base, and which restricts rotation of the lock base in the pulling-out direction by meshing of the external teeth with the ratchet teeth a torsion shaft having opposite ends, provided in the take-up shaft coaxially with the take-up shaft, one end of the torsion shaft being coupled to the take-up shaft, the other end being coupled to the lock base, for integrally rotating the take-up shaft and the lock base, and allowing rotation of the take-up shaft relative to the lock base due to torsion deformation of the torsion shaft, and a lock cover formed with a push nut portion with which a distal end portion of the torsion shaft is engaged, a hook portion with which the lock base is engaged, and an outer peripheral flang
Asagiri Katsuki
Hori Seiji
Nagata Tomonori
Sumiyashiki Akira
Cole Thomas W.
Kabushiki Kaisha Tokai-Rika-Denki-Seisakusho
Nixon & Peabody LLP
Schlak Daniel K
Walsh Donald P.
LandOfFree
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