Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
1999-11-01
2001-11-20
Jillions, John M. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
Reexamination Certificate
active
06318662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a webbing winding device having a pre-tensioner which tenses a passenger restraining webbing of a seat belt apparatus in a passenger restraining direction during an emergency deceleration of a vehicle cause by a vehicle collision or the like.
2. Description of the Related Art
Some types of webbing winding device for use in a vehicle seat belt unit have a pre-tensioner for removing play in the webbing by retracting the webbing so that it becomes tense during an emergency deceleration of a vehicle caused by a collision or the like. This type of webbing winding device has been described in, for example, Japanese Patent No. 2500192. The belt retractor which is a webbing winding device described in Japanese Patent No. 2500192 comprises a belt drum around which a belt web (webbing) is wound, a pinion connected to this belt drum via a free wheel connecting apparatus and gear transmitting means for transmitting rotation in one direction only, a rack which meshes with this pinion and a piston driving apparatus in which a piston is connected to this rack. When a vehicle is in a collision, the piston driving apparatus is actuated by gas generated by a gas generator so as to move the rack. The pinion is then rotated in a direction for winding up the belt web and the gear transmitting means increases the angular velocity of the rotation of the pinion and transmits it to the belt drum.
Further, even if the pre-tensioner is not actuated, the above described webbing winding device is continually urging the webbing winding shaft so as to reduce play in the webbing. However, the winding force for the webbing from the winding shaft cannot be made very strong in order to avoid imparting a feeling of strong pressure to a passenger from the webbing. AS a result, sometimes there is a slight play in the webbing and the amount of winding until the webbing becomes tense during an emergency such as a vehicle collision varies depending on the magnitude of this play. Therefore, in a conventional webbing winding device, in order to ensure that the webbing remains tense during an emergency such as a vehicle collision, the play in the webbing is assumed to be substantially at the maximum so that the webbing winding amount, which is the amount the webbing can be wound up by the pre-tensioner, is set as a large amount.
To increase the winding amount of the webbing by the pre-tensioner in the above described webbing winding device, it is necessary to increase the travelling stroke of the rack by the piston driving apparatus or increase the acceleration ratio from the gear transmission means so as to increase the distance rotated by the belt drum with respect to the distance traveled by the rack. However, if the movement stroke of the rack by the piston apparatus is increased, the lengths of the piston driving apparatus and rack are extended so that the size of the apparatus increases. Further, because the stages of the gears constituting the gear transmitting means need to be multiplied in order to increase the acceleration ratio of the gear transmission means, the size of the apparatus is enlarged.
SUMMARY OF THE INVENTION
Accordingly, in view of the above problems, an object of the present invention is to provide a small webbing winding device capable of reliably winding the webbing onto a winding shaft until the webbing becomes tense when the pre-tensioner is actuated, even if play in the webbing is large.
According to a first aspect of the present invention, there is provided a webbing winding device having a pre-tensioner for tensioning a webbing for restraining a passenger in a passenger restraining direction in an emergency deceleration of a vehicle, the webbing winding device comprising: a winding shaft to which an end of the webbing is fixed; and a gear train mechanism comprising a plurality of gears arranged in such a manner that adjacent gears mesh with each other, wherein a driving gear which receives an external driving force when the pre-tensioner is actuated is driven from a starting end position to a terminating position, which are set in advance, so as to rotate the winding shaft in a direction for retracting the webbing, and when a driving of the driving gear is completed, at least a pair of adjacent gears are separated so as to enable the winding shaft to be rotated in the direction for retracting the webbing by inertial force.
In the gear train mechanism of the webbing winding device having the above structure, when the pre-tensioner is actuated, a driving gear is driven from a starting end position set in advance to a terminating end position set in advance so as to rotate the winding shaft in the webbing winding direction. When the driving of the driving gear is completed, at least a pair of adjacent gears are separated so as to enable the winding shaft to rotate in the webbing retracting direction due to an inertial force. As a result, when the pre-tensioner is actuated, the winding shaft is rotated by torque transmitted from the gear train mechanism enabling the webbing to be wound around the winding shaft. When the driving of the driving gear is completed, at least a pair of adjacent gears are separated so that a rotation of the winding shaft in the webbing retracting direction is not blocked. Thus, if there is play in the webbing after the driving of the driving gear is completed, the tension of the webbing to be applied to the winding shaft as a rotation load decreases. As a result, the winding shaft rotates in the webbing retracting direction due to inertial force. Thus, even if the driving gear arrives at the terminal end position before the webbing becomes tense, the winding shaft continues to rotate in the webbing retracting direction until a tension balancing the inertial force of the winding shaft is generated in the webbing.
Therefore, if the inertial force generated in the winding shaft when the driving of the driving gear is completed is set large enough, even if the play in the webbing is large, the winding shaft can be rotated in the webbing retracting direction until the play in the webbing fitted around a passenger is removed.
The term rotation of the winding shaft due to inertial force used here means a rotating motion of the winding shaft generated by inertial force applied to the winding shaft. The inertial force to be applied to the winding shaft includes inertial force based on the mass of a gear or the like rotating through a link with the winding shaft as well as inertial force based on the mass of the winding shaft itself.
In the first aspect of the webbing winding device of the present invention, the gear train mechanism is preferably provided at a position at least corresponding to the terminal end position of one gear and along a pitch line, and has a toothless portion forming a gap between the driving gear and another adjacent gear when the driving of the driving gear is completed.
In the webbing winding device having the above structure, when the driving of the driving gear is completed, a gap is formed between at least one gear and a gear adjacent to this gear by the toothless portion. Thus, when the driving of the driving gear is completed, at least one pair of adjacent gears in the gear train mechanism can be separated. Therefore, blocking of the rotation of the winding shaft by the gear train mechanism can be prevented so that the winding shaft can be rotated in the webbing retracting direction by the inertial force.
According to a second aspect of the present invention, there is provided a webbing winding device having a pre-tensioner for tensioning a webbing for restraining a passenger in a passenger restraining direction in an emergency deceleration of a vehicle, the webbing winding device comprising: a winding shaft to which an end of the webbing is fixed; a gear train mechanism comprising a plurality of gears arranged in such a manner that adjacent gears mesh with each other, wherein a driving gear which receives an driving force when the pre-tensioner is actuated
Hori Seiji
Imai Keisuke
Katoh Keiichi
Nagata Tomonori
Yamashita Tatsuo
Cole Thomas W.
Jillions John M.
Kabushiki Kaisha Tokai-Rika-Denki-Seisakusho
Nixon & Peabody LLP
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