Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2001-02-14
2002-11-05
Rivera, William A. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
C280S805000
Reexamination Certificate
active
06474587
ABSTRACT:
BACKGROUND
The present invention relates to seat belt retractors for spooling seat belts (webbings) for retaining passengers in seats of vehicles and the like. More specifically, it relates to a seat belt retractor which can transmit large torque and is provided with a torsion bar which can be easily formed by forging.
A seat belt device provided in a vehicle, such as an automobile, restrains a passenger from an abrupt movement caused by acceleration due to collision of the vehicle, thereby ensuring safety of the passenger. The seat belt device generally includes a webbing or belt, a retractor, a buckle, and the like. The retractor retracts the webbing by winding the webbing about a spool using a spring force. The retractor then locks the webbing from being pulled out from the spool when applied with an impact, thereby restraining the passenger. The buckle serves for making the webbing to fit the passenger's body, and is generally disposed at a side of the seat.
Conventionally, in the seat belt device, the webbing has been locked from being pulled out from the retractor in a collision, and the passenger's body has been restrained from moving forward by the locked webbing. However, a load would be applied to the passenger at the breast, etc., via the webbing, when the passenger is rapidly restrained from moving forward. It has been confirmed that the load applied to the passenger can be effectively reduced by drawing out the webbing by a given length while applying a predetermined resistance to the draw-out movement. That is, when restraining the passenger from moving, the webbing is preferably drawn out by a given length while being applied with a predetermined load in the opposite direction, thereby absorbing energy of collision applied to the passenger.
The structure for absorbing energy applied to the passenger is called an energy absorption “EA” structure.
A seat belt retractor which uses a torsion bar as the EA structure is known. In this type of seat belt retractor, a spool for spooling a webbing is non-rotatably connected to a relatively fine torsion bar at one end of the torsion bar. A locking structure to prevent the webbing from pulling out is connected to the other end of the torsion bar. Whereby, the rotation of the spool may be locked via the torsion bar. The force required to restrain the passenger from moving forward by inertia (i.e, a tensile force applied to the webbing) is transmitted to the torsion bar via the spool as a twisting force. When the twisting force exceeds a given value, twisting plastic-deformation occurs in the torsion bar. As a result, the locked spool gradually rotates, and the webbing is drawn out while being applied with a predetermined tensile force.
When the torsion bar twists to deform, a torque is applied to the connection part of the spool and the torsion bar in the twisting direction (peripheral direction). A conventional torsion bar used for transmitting the torque is shown in FIG.
7
.
FIG.
7
(A) is a perspective view of the torsion bar used in the known seat belt retractor. FIG.
7
(B) is an expanded front view of a connection part of the torsion bar shown in FIG.
7
(A).
In FIG.
7
(A), a torsion bar
100
includes a cylindrical bar
102
. Connection parts
104
and
106
individually having hexagonal peripheries are formed toward the ends of the bar
102
. As shown in the drawing, the left connection part
104
is connected with a reel, and the right connection part
106
is connected with a reel-rotation locking structure. The torsion bar
100
is generally made of a steel wire (according to, for example, JIS Standard S
15
C) by forging. In this case, the diameters of a base material and a twisting part of the torsion bar
100
(shown by symbol X in FIG.
7
(B)) are made the same so that the strength of the torsion bar equals the strength of the base material.
However, since the connection parts
104
and
106
of the torsion bar
100
are hexagonal, apexes
104
a
and
106
a
are in line contact along a line parallel to the longitudinal axis of the bar
100
with the reel and parts of the reel-rotation locking structure, respectively. Therefore, when a large twisting force is applied to the torsion bar
100
, the apexes
104
a
and
106
a
in line contact are likely to be scraped away and to become smooth. Particularly, when the reel, a locking base, or the like, which are members at the concavity side to be coupled (i.e. the side configured to match connection part) with the connection parts, are made of a soft material, such as aluminum. In these situations the concavities of the reel and the like are likely to be scraped away by the twist of the torsion bar.
Another seat belt retractor is disclosed in, for example, Japanese Patent No. 2816332, in which the connection part of the torsion bar is formed in spline so that each convex part of the spline portion is in plane contact. Torsion bars having the spline portions are also disclosed in, for example, Japanese Patent No. 2887120, U.S. Pat. No. 5,899,402, and UK Patent No. GB2314535A. With these arrangements, the connection parts of the torsion bars are not likely to be scraped away and become smooth at the convexities even when the torsion bar twists to deform.
However, most suitable particular spline shapes are not described at all in the above publications.
On the other hand, JIS Standard (B1603) specifies a spline shape, as shown in FIG.
8
. According to JIS Standard, the shape shown in the drawing is formed so that a ratio D
1
/D
2
of a tip-circle diameter D
1
to a root-circle diameter D
2
exceeds 1.3.
However, the ratio D
1
/D
2
according to JIS Standard is excessively large; therefore, the convexities become sharp. The convexities having that sharpness are difficult to form by forging in a simplified process.
Accordingly, an object of the present invention is to provide a seat belt retractor with a torsion bar which can receive a large torque transmitted and can be easily formed by forging.
SUMMARY OF THE INVENTION
In order to overcome the aforementioned disadvantages, a seat belt retractor according to the present invention comprises a reel for spooling a seat belt (webbing); a locking mechanism or structure for locking the rotation of the reel; and a torsion bar non-rotatably connected to the reel at one end of the torsion bar and non-rotatably connected to the structure for locking the rotation of the reel at the other end of the torsion bar. The ends (connection parts) of the torsion bar are torx-shaped having a plurality of concavities and convexities formed in a wave shape, and concavities formed in the reel and the structure for locking the rotation of the reel with which the reel and the structure for locking the rotation of the reel are coupled, respectively. A ratio R
1
/R
2
of the distance between the tops of the convexities formed in the wave-shape and the axial center of the torsion bar (radius R
1
) to the distance between the bottoms of the concavities and the axial center of the torsion bar (radius R
2
) is set to 1.2 to 1.3.
Since the concavities of the connection parts of the torsion bar and the structure for locking the rotation of the reel are formed in a torx-shape, a torque twisting the torsion bar is transmitted via a plane contact. Therefore, the transmissible torque can be increased compared with the known seat belt retractor having connection parts formed in a hexagon. Moreover, the connection parts can be formed by forging more easily than those having the torx or spline shape specified according to JIS Standard by setting the value R
1
/R
2
to 1.2 to 1.3.
The above forming by forging includes irregular-shape forming by applying a pressure to a bar at the ends thereof. In the torx-shape shown in
FIG. 5
, the difference in diameter from the bar (see thickness &agr; shown in
FIG. 5
) can be set larger than in a hexagonal shape. Therefore, the ends of the torsion bar can be reliably and easily formed.
In the seat belt retractor according to the present invention, it is particularly advantageous to make a material (such as a
Kanamori Yasushi
Mishina Joji
Shiotani Masahiro
Foley & Lardner
Rivera William A.
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-2977261