Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2001-11-21
2003-05-27
Matecki, Kathy (Department: 3654)
Winding, tensioning, or guiding
Reeling device
With spring motor
C280S806000
Reexamination Certificate
active
06568621
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a seat belt retractor including an energy mechanism (that is, an absorbing belt load limiting mechanism, which is also hereinafter referred to as the “EA mechanism”) which, at a normal time, winds up a webbing so that it can be retracted and extracted, and which, during an emergency, such as collision of a vehicle, prevents the webbing from being extracted or withdrawn, and which, when the drawing out of the webbing is prevented, limits the load exerted on the webbing by twisting and deformation of a torsion bar, so that an impact energy is absorbed. More particularly, the present invention relates to a seat belt retractor in which a limited load (hereinafter referred to as the “EA load”) which limits the load exerted on the webbing is set so that it can be varied.
In this type of a conventional seat belt retractor, when a webbing is restrained to protect an occupant of a vehicle in an emergency, such as collision of the vehicle, the vehicle is considerably decelerated, so that the occupant tries to move forward due to a large amount of inertia. Therefore, a large load is exerted on the webbing, so that the occupant receives a large impact force from the webbing. Although this impact force with respect to the occupant does not particularly cause any problems, it is desirable that this impact force be limited if possible.
To achieve this, conventionally, an EA mechanism including a torsion bar has been provided. In an emergency, such as that mentioned above, the torsion bar is twisted and deformed, and absorbs impact energy produced by impact force in order to limit the load exerted on the webbing. In order to effectively absorb the impact energy, various proposals have been made to variably set the EA load.
One example of this type of a conventional seat belt retractor including such an EA mechanism that variably sets the EA load is disclosed in, for example, Japanese Unexamined Patent Publication (KOKAI) Nos. 2000-16243 and 2000-25567. The seat belt retractors disclosed in these documents are each constructed so that a second torsion bar is disposed inside a cylindrical first torsion bar, and the two torsion bars are linked at corresponding end portions to rotate in at least a direction of rotation. In an emergency, when the torsion bars are twisted and deformed, at first, the first and second torsion bars are both twisted and absorb a large amount of impact energy. When the first torsion bar ruptures, the impact energy is absorbed by twisting the second torsion bar alone. Accordingly, the EA load is varied in two stages.
Another example of this type of a conventional seat belt retractor including such an EA mechanism that variably sets the EA load is disclosed in, for example, Japanese Unexamined Patent Publication (KOKAI) No. 10-258702. In the seat belt retractor disclosed in this document, a shaft is disposed at the inner portion of a cylindrical spool that winds up a webbing, and an EA plate which is disposed inside a space formed between the spool and the shaft, and has a double-curvature shape and a control structural portion, is provided. One end of the EA plate receives a rotational force of the spool in a direction in which the webbing is extracted. The other end of the EA plate is connected and secured to the shaft. During the relative rotation of the spool with respect to the shaft in the direction in which the webbing is extracted in an emergency, a rotational force of the spool in the direction in which the webbing is extracted acts on the one end of the EA plate, so that the EA plate undergoes plastic deformation. This causes impact energy to be absorbed, and deformation force to be changed by the control structural portion, that is, energy absorption to be changed. In this way, the EA load is made variable.
Still another example of this type of the conventional seat belt retractor including such an EA mechanism that variably sets the EA load is disclosed in, for example, Japanese Unexamined Patent Publication No. 2000-43677. The seat belt retractor disclosed in this document comprises a torsion bar, which is provided in a spool, and a stopper ring, which is provided at a side surface of the spool. During the relative rotation of the spool with respect to a pawl holder in a direction in which the webbing is extracted at the time of an emergency, at first, the torsion bar is twisted and an engaging stepped portion of the pawl holder cuts an inner peripheral side of the stopper ring in order to absorb a large amount of impact energy. When the cutting of the inner peripheral side of the stopper ring is completed, the impact energy is absorbed by twisting the torsion bar alone. In this way, the EA load is made variable in two stages.
The EA load may be made variable by using the following structure instead of the structure that makes it variable by cutting the inner peripheral side of the stopper ring. This structure comprises a shear pin or a shear protrusion at a side surface of the spool. In this structure, at first, the torsion bar is twisted and a shear load is exerted onto the shear pin or the shear protrusion in order to absorb a large amount of impact energy. After the shear pin or the shear protrusion has been ruptured by shearing, impact energy is absorbed by twisting the torsion bar alone. This causes the EA load to be made variable.
However, in the above-described EA mechanism using two torsion bars, since the axial length of the first torsion bar to be ruptured is set equal to the main axial length of the second torsion bar, the EA load depends upon the axial length of the second torsion bar. Therefore, the EA load can not be set freely, and it is difficult to arbitrarily set the EA load regardless of the axial length of the second torsion bar.
In the above-described EA mechanism using the EA plate having the control structural portion, not only does the EA plate have a complicated double-curvature form, but also the EA mechanism has a complicated structure. Moreover, since the form of the EA plate and the structure of the EA mechanism are complicated, and the control structural portion is formed by local work hardening, it is difficult to stably set the EA load.
In the EA mechanism in which the inner peripheral side of the stopper ring is cut, it is difficult to always stably set the EA load by cutting the inner peripheral side of the stopper ring.
In view of the above-described situations, it is an object of the present invention to provide a seat belt retractor which, by a relatively simple structure, makes it possible to set an EA load more freely and to more stably set the EA load.
Further objects and advantages of the invention will be apparent from the following description of the invention.
SUMMARY OF THE INVENTION
To overcome the above-described problems, in a first aspect of the invention, a seat belt retractor comprises at least: a spool which winds up a seat belt; a lock mechanism including a locking member whose rotation in a direction in which the seat belt is extracted or withdrawn is prevented in an emergency; and a seat belt load limit mechanism including a torsion bar disposed in the spool. The torsion bar rotatably connects the spool and the locking member and is twistable and deformable. When the rotation of the locking member in the direction in which the seat belt is extracted is prevented in order for the spool to rotate relative to the locking member in the direction in which the seat belt is extracted, the load limit mechanism limits a load that is exerted on the seat belt by the twisting and deformation of the torsion bar. The seat belt load limit mechanism further includes a torsion pipe disposed inside an annular space between the spool and the torsion bar. One end side of the torsion pipe is connected and secured to the spool and the other end side of the torsion pipe is provided so as to be engageable with and disengageable from the locking member, or the one end side of the torsion pipe is provided so as to be engageable with and diseng
Hiramatsu Koji
Yamanishi Takahiro
Kanesaka & Takeuchi
Kim Sang
Matecki Kathy
Takata Corporation
LandOfFree
Seat belt retractor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Seat belt retractor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Seat belt retractor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3014837