U.S. patent application number 11/503965 was filed with the patent office on 2006-12-07 for webbing retractor.
This patent application is currently assigned to KABUSHIKI KAISHA TOKAI-RIKA-DENKI-SEISAKUSHO. Invention is credited to Teruhiko Koide, Fuminori Komiya, Shinji Mori.
Application Number | 20060273212 11/503965 |
Document ID | / |
Family ID | 29774566 |
Filed Date | 2006-12-07 |
United States Patent
Application |
20060273212 |
Kind Code |
A1 |
Mori; Shinji ; et
al. |
December 7, 2006 |
Webbing retractor
Abstract
A webbing retractor which, by causing relative rotation between
a prime mover rotating body and a rotating disc, connects the prime
mover rotating body and a driven shaft which is connected to a
take-up shaft of a webbing belt. A planet gear is pivotally
supported at a plate having a braking piece and meshes with a sun
gear. The plate is supported so as to be swingable around the sun
gear. When the sun gear is driven to rotate at greater than a
predetermined speed, the planet gear begins to circle around the
sun gear against urging force of a spring attached to the plate,
and makes the plate rotate such that the braking piece slidingly
contacts the friction ring. Due to this braking, the rotating disc
connected to the friction ring rotates relative to the prime mover
rotating body.
Inventors: |
Mori; Shinji; (Aichi-ken,
JP) ; Komiya; Fuminori; (Aichi-ken, JP) ;
Koide; Teruhiko; (Aichi-ken, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
401 9TH STREET, NW
SUITE 900
WASHINGTON
DC
20004-2128
US
|
Assignee: |
KABUSHIKI KAISHA
TOKAI-RIKA-DENKI-SEISAKUSHO
Aichi-ken
JP
|
Family ID: |
29774566 |
Appl. No.: |
11/503965 |
Filed: |
August 15, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10615388 |
Jul 9, 2003 |
7108284 |
|
|
11503965 |
Aug 15, 2006 |
|
|
|
Current U.S.
Class: |
242/390.8 ;
242/375.3; 280/807 |
Current CPC
Class: |
B60R 2022/468 20130101;
B60R 2022/4666 20130101; B60R 22/46 20130101 |
Class at
Publication: |
242/390.8 ;
280/807; 242/375.3 |
International
Class: |
B65H 75/48 20060101
B65H075/48; B60R 22/34 20060101 B60R022/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2002 |
JP |
2002-202970 |
Claims
1. A webbing retractor for an elongated, strip-shaped webbing belt
used for application to a body of a vehicle occupant, the webbing
retractor comprising: a take-up shaft for taking the webbing belt
up around itself, which take-up shaft is rotatably held, and to
which one end of the webbing belt is anchored; a driven shaft
connected to the take-up shaft; a prime mover rotating body
rotatably supported relative to and coaxially with the driven
shaft; a rotating member supported coaxially with both the prime
mover rotating body and the driven shaft, and rotatable relative to
both the prime mover rotating body and the driven shaft; connecting
members for connecting the prime mover rotating body and the driven
shaft, by interlocking with relative rotation of the rotating
member with respect to the prime mover rotating body, so as to
transmit rotation of the prime mover rotating body to the driven
shaft; a driving mechanism, including a drive source, for driving
rotation of the prime mover rotating body in a predetermined
direction; a braking mechanism for braking rotation of the rotating
member such that relative rotation of the rotating member with
respect to the prime mover rotating body arises; wherein the driven
shaft has a peripheral surface, and the connecting members are held
at the prime mover rotating body so as to be able to approach and
move away from the driven shaft, and when the prime mover rotating
body is rotated, the connecting members contact the peripheral
surface of the driven shaft due to the relative rotation, and
connect the prime mover rotating body and the driven shaft; and
wherein a plurality of teeth are formed at the peripheral surface
of the driven shaft, and the connecting members have pawl shapes
which can engage with any of the teeth, and at least one of the
connecting members contacts the tooth of the driven shaft so as to
engage with the tooth, and connects the prime mover rotating body
and the driven shaft.
2-8. (canceled)
9. A webbing retractor for an elongated, strip-shaped webbing belt
used for application to a body of a vehicle occupant, the webbing
retractor comprising: a take-up shaft for taking the webbing belt
up around itself, which take-up shaft is rotatably held, and to
which one end of the webbing belt is anchored; a driven shaft
connected to the take-up shaft; a prime mover rotating body
rotatably supported relative to and coaxially with the driven
shaft; a rotating member supported coaxially with both the prime
mover rotating body and the driven shaft, and rotatable relative to
both the prime mover rotating body and the driven shaft; connecting
members for connecting the prime mover rotating body and the driven
shaft, by interlocking with relative rotation of the rotating
member with respect to the prime mover rotating body, so as to
transmit rotation of the prime mover rotating body to the driven
shaft; a driving mechanism, including a drive source, for driving
rotation of the prime mover rotating body in a predetermined
direction; a braking mechanism for braking rotation of the rotating
member such that relative rotation of the rotating member with
respect to the prime mover rotating body arises; wherein the
braking mechanism brakes the rotating member when the prime mover
rotating body is driven to rotate at greater than a predetermined
speed.
10. A webbing retractor for an elongated, strip-shaped webbing belt
used for application to a body of a vehicle occupant, the webbing
retractor comprising: a take-up shaft for taking the webbing belt
up around itself, which take-up shaft is rotatably held, and to
which one end of the webbing belt is anchored; a driven shaft
connected to the take-up shaft; a prime mover rotating body
rotatable supported relative to and coaxially with the driven
shaft; a rotating member supported coaxially with both the prime
mover rotating body and the driven shaft, and rotatable relative to
both the prime mover rotating body and the driven shaft; connecting
members for connecting the prime mover rotating body and the driven
shaft, by interlocking with relative rotation of the rotating
member with respect to the prime mover rotating body, so as to
transmit rotation of the prime mover rotating body to the driven
shaft; a driving mechanism, including a drive source, for driving
rotation of the prime mover rotating body in a predetermined
direction; a braking mechanism for braking rotation of the rotating
member such that relative rotation of the rotating member with
respect to the prime mover rotating body arises; wherein the
braking mechanism connects the driving mechanism such that motion
of the braking mechanism for braking can be transmitted from the
driving mechanism.
11. A webbing retractor for an elongated, strip-shaped webbing belt
used for application to a body of a vehicle occupant, the webbing
retractor comprising: a take-up shaft for taking the webbing belt
up around itself, which take-up shaft is rotatable held, and to
which one end of the webbing belt is anchored; a driven shaft
connected to the take-up shaft; a prime mover rotating body
rotatable supported relative to and coaxially with the driven
shaft; a rotating member supported coaxially with both the prime
mover rotating body and the driven shaft, and rotatable relative to
both the prime mover rotating body and the driven shaft; connecting
members for connecting the prime mover rotating body and the driven
shaft, by interlocking with relative rotation of the rotating
member with respect to the prime mover rotating body, so as to
transmit rotation of the prime mover rotating body to the driven
shaft; a driving mechanism, including a drive source, for driving
rotation of the prime mover rotating body in a predetermined
direction; a braking mechanism for braking rotation of the rotating
member such that relative rotation of the rotating member with
respect to the prime mover rotating body arises; wherein the
braking mechanism brakes the rotating member interlockingly with
driving rotation of the prime mover rotating body by the driving
mechanism.
12-14. (canceled)
15. A webbing retractor for an elongated, strip-shaped webbing belt
used for application to a body of a vehicle occupant, the webbing
retractor comprising: a take-up shaft for taking the webbing belt
up around itself, which take-up shaft is rotatable held, and to
which one end of the webbing belt is anchored; a driven shaft
connected to the take-up shaft; a prime mover rotating body
rotatable supported relative to and coaxially with the driven
shaft; a rotating member supported coaxially with both the prime
mover rotating body and the driven shaft, and rotatable relative to
both the prime mover rotating body and the driven shaft; connecting
members for connecting the prime mover rotating body and the driven
shaft, by interlocking with relative rotation of the rotating
member with respect to the prime mover rotating body, so as to
transmit rotation of the prime mover rotating body to the driven
shaft; a driving mechanism, including a drive source, for driving
rotation of the prime mover rotating body in a predetermined
direction; a braking mechanism for braking rotation of the rotating
member such that relative rotation of the rotating member with
respect to the prime mover rotating body arises; wherein the prime
mover rotating body has an external gear which is ring shaped and
has external teeth for connection to the driving mechanism such
that the external gear can be driven and rotated; a base portion
having a holding portion for holding the plurality of connecting
members, the base portion being pivotally supported coaxially with
the rotating member; and at least one torque limiter provided
between the external gear and the base portion, so as to be able to
transmit torque in a predetermined range to the base portion from
the external gear.
16. A webbing retractor for an elongated, strip-shaped webbing belt
used for application to a body of a vehicle occupant, the webbing
retractor comprising: a take-up shaft for taking the webbing belt
up around itself, which take-up shaft is rotatable held, and to
which one end of the webbing belt is anchored; a driven shaft
connected to the take-up shaft; a prime mover rotating body
rotatable supported relative to and coaxially with the driven
shaft; a rotating member supported coaxially with both the prime
mover rotating body and the driven shaft, and rotatable relative to
both the prime mover rotating body and the driven shaft; connecting
members for connecting the prime mover rotating body and the driven
shaft, by interlocking with relative rotation of the rotating
member with respect to the prime mover rotating body, so as to
transmit rotation of the prime mover rotating body to the driven
shaft; a driving mechanism, including a drive source, for driving
rotation of the prime mover rotating body in a predetermined
direction; a braking mechanism for braking rotation of the rotating
member such that relative rotation of the rotating member with
respect to the prime mover rotating body arises; further comprising
a control unit for controlling operation of the driving mechanism,
wherein the control unit effects control so as to cause the driving
mechanism to operate when a rate of change in deceleration at a
time when the vehicle decelerates is greater than or equal to a
predetermined value.
17-20. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 USC 119 from
Japanese patent Application No. 2002-202970, the disclosure of
which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a webbing retractor which
structures a seat belt device for restraining, by an elongated,
strip-shaped webbing belt, the body of a vehicle occupant who is
seated in a seat of a vehicle or the like.
[0004] 2. Description of the Related Art
[0005] A seat belt device which restrains, by an elongated,
strip-shaped webbing belt, the body of a vehicle occupant who is
seated in a seat of a vehicle, is equipped with a webbing retractor
which is fixed to the vehicle body at the side of the seat. The
webbing retractor has a spool (take-up shaft) whose axial direction
runs, for example, substantially along the longitudinal direction
of the vehicle. The proximal end side, in the longitudinal
direction, of the webbing belt is anchored at the spool. The spool
can take the webbing belt up in the form of a roll around the outer
peripheral portion of the spool. When the seat belt device is not
being used, the webbing belt can be accommodated in a state of
being taken-up on the outer peripheral portion of the spool.
[0006] An urging member, such as a spiral spring or the like which
urges the spool in a take-up direction in which the spool takes up
the webbing belt, is provided at the webbing retractor. Due to the
urging force of this urging member, the webbing belt is taken up
and accommodated. In the state in which the webbing belt is applied
to the body of a vehicle occupant, slack or the like of the webbing
belt is eliminated by the urging force of the urging member.
[0007] On the other hand, a mechanism has been conceived in which,
by taking-up a predetermined amount of the webbing belt onto the
take-up shaft in a state of rapid deceleration of the vehicle or
the like, the slight looseness known as "slack" or the like can be
eliminated, and the force for restraining the body of the vehicle
occupant by the webbing belt is increased such that the body of the
vehicle occupant is held even more reliably. In such a mechanism,
generally, the state of a rapid deceleration of the vehicle is
sensed by an acceleration sensor, and the take-up shaft is forcibly
rotated in the take-up direction on the basis of an electric signal
from the acceleration sensor.
[0008] In contrast, a structure has been thought of in which the
distance to another vehicle or an obstacle which is ahead is
detected by a distance sensor or the like. When the distance to the
vehicle or the obstacle which is ahead is less than a given value,
a motor is operated, and the take-up shaft is rotated in the
take-up direction by the torque of the motor.
[0009] Even in such a structure in which the take-up shaft is
rotated in the take-up direction by the torque of a motor when the
distance to a vehicle or an obstacle which is ahead is less than a
given value, usually, the spool is rotated in the take-up direction
by the urging force of the aforementioned urging member such as a
spiral spring or the like. When the webbing belt is pulled out, the
spool is rotated against the urging force of the urging member such
as a spiral spring or the like. Thus, a clutch is provided between
the motor and the spool so that the rotation of the spool at the
time of usual taking-up and pulling-out of the webbing belt is not
transmitted to the output shaft of the motor. Only in cases in
which the motor is operated is the output shaft of the motor
mechanically connected to the spool.
[0010] As a clutch mechanism used in such a structure, there is a
structure in which an inertial mass body called an inertial plate
is provided so as to be freely rotatable around the axis of the
spool. In such a clutch mechanism, the inertial plate is provided
so as to be able to rotate relative to both a driven shaft which is
integral with the spool and a rotating body of a prime mover which
rotates by receiving the rotation of the output shaft of the
motor.
[0011] However, the other end of an urging member, such as a
compression coil spring or the like whose one end is directly or
indirectly engaged with the rotating body of the prime mover, is
engaged with the inertial plate. When the rotating body of the
prime mover rotates due to the torque of the motor, and,
accompanying this rotation, the compression coil spring attempts to
rotate, the urging force of the compression coil spring rotates the
inertial plate.
[0012] However, the inertial plate attempts to maintain a stopped
state by the inertia thereof. Thus, for example, when the rotating
body of the prime mover suddenly rotates, relative rotation arises
between the rotating body of the prime mover and the inertial plate
which is attempting to maintain the stopped state by inertia.
Interlockingly with this relative rotation, a connecting member,
such as a pawl or the like which rotates together with the rotating
body of the prime mover, is moved, and the connecting member is
made to engage with the driven shaft. The torque of the motor is
transmitted to the driven shaft, and consequently, to the
spool.
[0013] However, in a structure using such an inertial plate, there
is the condition that the rotating body of the prime mover must be
rotated suddenly by the torque of the motor.
[0014] In order to satisfy such a condition, the rotating body of
the prime mover and the output shaft of the motor must be directly
connected without the torque of the motor being decelerated by a
reduction gear or the like.
[0015] However, in the case of such a structure, if the clutch
mechanism does not have a reduction mechanism, the rotation of the
rotating body of the prime mover is transmitted to the driven shaft
as well without being decelerated. Thus, the taking-up and the like
of the webbing belt are carried out excessively rapidly.
SUMMARY OF THE INVENTION
[0016] In view of the aforementioned, an object of the present
invention is to provide a webbing retractor which generates
relative rotation between a prime mover rotating body and a
rotating body such as an inertial plate or the like so as to
reliably transmit rotation of the prime mover rotating body to a
driven shaft, such that taking-up of a webbing belt by the driving
force of a driving mechanism can be carried out.
[0017] A first aspect of the present invention is a webbing
retractor for an elongated, strip-shaped webbing belt used for
application to a body of a vehicle occupant, the webbing retractor
comprising: a take-up shaft for taking the webbing belt up around
itself, which take-up shaft is rotatably held, and to which one end
of the webbing belt is anchored; a driven shaft connected to the
take-up shaft; a prime mover rotating body rotatably supported
relative to and coaxially with the driven shaft; a rotating member
supported coaxially with both the prime mover rotating body and the
driven shaft, and rotatable relative to both the prime mover
rotating body and the driven shaft; an urging member, attached to
the prime mover rotating body, for urging the rotating member in a
direction of rotation of the prime mover rotating body when the
prime mover rotating body is rotated; connecting members for
connecting the prime mover rotating body and the driven shaft, by
interlocking with relative rotation of the rotating member with
respect to the prime mover rotating body, so as to transmit
rotation of the prime mover rotating body to the driven shaft; a
driving mechanism, including a drive source, for driving rotation
of the prime mover rotating body in a predetermined direction; and
a braking mechanism for braking rotation of the rotating member
such that relative rotation of the rotating member with respect to
the prime mover rotating body arises.
[0018] A second aspect of the present invention is a webbing
retractor for a webbing belt, the webbing retractor having a
take-up shaft, and by rotating the take-up shaft in one direction,
the webbing retractor takes-up and accommodates, on the take-up
shaft and from a proximal end side, a webbing belt which is
elongated and strip-shaped and which is applied to a body of a
vehicle occupant so as to restrain the body and which has a distal
end and a proximal end, and due to the webbing belt being pulled
toward a distal end side, the webbing retractor rotates the take-up
shaft in another direction, and the webbing belt, which is taken-up
on the take-up shaft, is pulled out, the webbing retractor
comprising: a driven shaft connected to the take-up shaft coaxially
and integrally; a prime mover rotating body which is substantially
ring shaped and which is provided coaxially with the driven shaft
so as to be able to rotate relative to the driven shaft; a rotating
member which is able to rotate relative to and coaxially with both
the prime mover rotating body and the driven shaft; an urging
member which is attached to the prime mover rotating body and
rotates together with the prime mover rotating body, and which
urges the rotating member in a direction of rotation of the prime
mover rotating body; connecting members which, interlockingly with
relative rotation of the rotating member with respect to the prime
mover rotating body, mechanically connect the prime mover rotating
body and the driven shaft, and transmit rotation of the prime mover
rotating body to the driven shaft; a driving mechanism having an
output shaft which is connected one of directly and indirectly to
the prime mover rotating body, and the driving mechanism rotates
the output shaft by driving force of the driving mechanism; and a
braking mechanism which, interlockingly with rotation of the output
shaft, applies frictional force to the rotating member and impedes
rotation of the rotating member.
[0019] The webbing retractor of the above-described aspect may
further comprise a rotation transmitting mechanism which is
provided between the output shaft and the prime mover rotating
body, and which receives rotation from the output shaft and
rotates, and which transmits rotation of the rotation transmitting
mechanism to the prime mover rotating body.
[0020] In the webbing retractor having the above-described
structure, the webbing belt, which is taken up onto the take-up
shaft from the proximal end side thereof, is pulled from the distal
end side thereof. The webbing belt is pulled-out while the take-up
shaft is rotated in the pull-out direction, which is one direction
around the axis thereof. By applying the pulled-out webbing belt to
the body of a vehicle occupant, the body of the vehicle occupant is
restrained by the webbing belt.
[0021] Further, when the state in which the pulled-out webbing belt
restrains the body of the vehicle occupant is cancelled, and
further, the take-up shaft is rotated in the take-up direction
which is opposite to the aforementioned pull-out direction, the
webbing belt is taken-up and accommodated in the form of a roll on
the outer peripheral portion of the take-up shaft.
[0022] On the other hand, in the present webbing retractor, when
the driving mechanism drives and the output shaft of the driving
mechanism rotates and the rotation of the output shaft is
transmitted to the prime mover rotating body and the prime mover
rotating body, which is connected directly or indirectly to the
output shaft, rotates. When the prime mover rotating body rotates,
the urging member, which is attached to the prime mover rotating
body, rotates in the direction of rotation of the prime mover
rotating body.
[0023] The urging member urges the rotating member in the direction
of rotation of the prime mover rotating body. Accordingly,
basically, the rotating member can rotate coaxially with and
relative to the prime mover rotating body and the driven shaft.
However, when the urging member rotates accompanying the rotation
of the prime mover rotating body, the urging member pushes the
rotating member in the direction of rotation of the prime mover
rotating body, and thereby attempts to rotate the rotating member
in the direction of rotation of the prime mover rotating body.
[0024] Here, in the present webbing retractor, when the driving
mechanism drives and the output shaft of the driving mechanism
rotates, the braking mechanism operates, and the braking mechanism
applies frictional force to the rotating member. This frictional
force works to impede rotation of the rotating member. Thus, as
described above, even if the urging member attempts to rotate the
rotating member in the direction of rotation of the prime mover
rotating body by the urging force of the urging member, the
rotation of the rotating member is restricted by the frictional
force which the braking mechanism applies to the rotating member.
In this way, relative rotation arises between the prime mover
rotating body and the rotating member.
[0025] When relative rotation arises between the prime mover
rotating body and the rotating member, the connecting members
mechanically connect the prime mover rotating body and the driven
shaft. In this way, the rotation of the prime mover moving body is
transmitted to the driven shaft, and the driven shaft, and
accordingly, the take-up shaft, rotate. In this way, if the driven
shaft rotates in the take-up direction for example, the webbing
belt is taken up onto the take-up shaft by the driving force of the
driving mechanism. If the driven shaft rotates in the pull-out
direction, slack arises in the webbing belt which is wound on the
take-up shaft, and the force by which the webbing belt restrains
the body of the vehicle occupant decreases.
[0026] In this way, in the present webbing retractor, when the
driving mechanism drives, relative rotation of the rotating member
with respect to the prime mover rotating body can be reliably
generated by the braking mechanism. In this way, the driving force
(torque) of the driving mechanism can be reliably transmitted to
the take-up shaft.
[0027] Further, in the webbing retractor of the above-described
aspect, the braking mechanism may be structured so as to include a
friction member which is substantially ring shaped and which is
exposed to an exterior of the prime mover rotating body in a state
in which the friction member is mechanically connected to the
rotating member; and a braking member which is attached to one of
the output shaft and the rotation transmitting member, and which,
interlockingly with rotation of the one of the output shaft and the
rotation transmitting member, moves so as to approach the friction
member and slidingly contacts the friction member.
[0028] In the webbing retractor having the above-described
structure, the friction member, which is exposed to the exterior of
the prime mover rotating body, is mechanically connected to the
rotating member. When the rotating member attempts to rotate, the
friction member also attempts to rotate together therewith.
[0029] Here, when the driving mechanism drives and the output shaft
rotates, the braking member, which is provided at the output shaft
or is provided at the rotation transmitting mechanism disposed
between the output shaft and the prime mover rotating body, moves
so as to approach the friction member, interlockingly with the
rotation of the output shaft or the rotating transmitting
mechanism. In this way, the braking member slidingly contacts the
friction member.
[0030] When the rotation of the friction member is restricted due
to the frictional force which is applied from the braking member
which slidingly contacts the friction member, rotation of the
rotating member, to which the friction member is connected, is
restricted indirectly. In this way, relative rotation arises
between the prime mover rotating body and the rotating member.
[0031] Namely, in the present webbing retractor, in a way, braking
force with respect to the rotating member, which is caused by the
frictional force from the braking member, is applied indirectly to
the rotating member via the friction member.
[0032] In the webbing retractor of the second aspect of the present
invention, the braking mechanism can be structured so as to include
a friction member which is provided at the exterior of the prime
mover rotating body, and which is mechanically connected to the
rotating member; a brake spring which is formed in a substantial
ring shape in which a take-up direction side end portion and a
pull-out direction side end portion around an axis of the driven
shaft are apart from one another, and the brake spring has a spring
property (elasticity), and an inner peripheral portion of the brake
spring slidingly contacts the friction member; and a diameter
forcibly reducing mechanism at which is anchored an end portion of
the brake spring at one of the take-up direction side and the
pull-out direction side, and which, interlockingly with rotation of
the output shaft for rotating the take-up shaft in the other of the
take-up direction and the pull-out direction, rotates the brake
spring in the one direction with respect to the friction member,
and reduces the diameter of the brake spring due to friction
between the friction member and the brake spring.
[0033] In the webbing retractor having the above-described
structure, the friction member, which is exposed at the exterior of
the prime mover rotating body, is mechanically connected to the
rotating member. When the rotating member attempts to rotate, the
friction member also attempts to rotate together therewith.
[0034] The inner peripheral portion of the ring-shaped brake spring
slidingly contacts the friction member. The end portion of the
brake spring at one of the take-up direction side and the pull-out
direction side is anchored at the diameter forcibly reducing
mechanism. Here, in order to explain the present invention such
that it can be understood more easily, explanation will be given
with "the one" of the take-up direction and the pull-out direction
being the "pull-out direction", and "the other" being the "take-up
direction".
[0035] When, in order to rotate the take-up shaft in the take-up
direction, the driving mechanism is operated and the output shaft
rotates, interlockingly with the rotation of the output shaft, the
diameter forcibly reducing mechanism makes the brake spring rotate
in the pull-out direction relative to the friction member.
[0036] When relative rotation arises in this way, frictional force
arises between the brake spring and the friction member. The
frictional force works to impede rotation of the brake spring.
Thus, in a case in which the pull-out direction side end portion is
forcibly rotated in the pull-out direction with respect to the
friction member, or in a case in which the pull-out direction side
end portion of the brake spring does not attempt to rotate
regardless of the fact that the take-up direction side end portion
of the brake spring is rotated in the take-up direction due to the
friction member attempting to rotate in the take-up direction, the
brake spring reduces the gap which is formed between the pull-out
direction side end portion and the take-up direction side end
portion. The diameter of the entire brake spring is thereby reduced
against the elasticity of the brake spring.
[0037] Due to the diameter of the brake spring being reduced, the
brake spring tightens around the friction member. In this way, the
frictional force between the friction member and the brake spring
increases.
[0038] The frictional force, which has increased in this way, works
to restrict rotation of the friction member in the take-up
direction. Due to rotation of the friction member in the take-up
direction being restricted by the frictional force, rotation in the
take-up direction of the rotating member, to which the friction
member is connected, is restricted. In this way, relative rotation
arises between the prime mover rotating body and the rotating
member.
[0039] The braking mechanism may be structured so as to include a
lever. The end portion of the brake spring at one of the take-up
direction side and the pull-out direction side is anchored at the
distal end side of the lever. The proximal end side of the lever is
indirectly connected to the driving mechanism. The lever may be
rotated by the driving force of the driving mechanism, and may pull
the brake spring toward the other of the take-up direction side and
the pull-out direction side.
[0040] In the webbing retractor having the above-described
structure, for example, when the prime mover rotating body rotates
in the take-up direction (which is the other of the take-up
direction and the pull-out direction) due to the driving force of
the driving mechanism, and the rotating member thereby attempts to
rotate in the take-up direction, accompanying this, the friction
member connected to the rotating member attempts to rotate in the
take-up direction. Moreover, the friction member attempts to rotate
the brake spring in the take-up direction due to the friction
between the friction member and the brake spring.
[0041] On the other hand, as described above, when the driving
mechanism drives and the output shaft rotates, the lever rotates in
the pull-out direction due to the rotation of the output shaft. Due
to the rotation of the lever in the pull-out direction, the
pull-out direction side end portion of the brake spring which is
anchored at the distal end side of the lever, is pulled in the
pull-out direction, and the brake spring attempts to rotate in the
pull-out direction.
[0042] In this way, due to the brake spring and the friction member
attempting to rotate in mutually opposite directions, the
frictional force between the brake spring and the friction member
suddenly increases. The frictional force, which has increased in
this way, works to restrict rotation of the friction member in the
take-up direction. Due to the rotation of the friction member in
the take-up direction being restricted by this frictional force,
the rotation in the take-up direction of the rotating member, to
which the friction member is connected, is restricted. In this way,
relative rotation arises between the prime mover rotating body and
the rotating member.
[0043] Or, the webbing retractor may have a frame which directly or
indirectly supports the take-up shaft, and the diameter forcibly
reducing mechanism may be structured such that the one side end
portion of the brake spring is anchored at the frame.
[0044] In the webbing retractor having the above-described
structure, for example, when the prime mover rotating body rotates
in the take-up direction (which is the other of the take-up
direction and the pull-out direction) due to the driving force of
the driving mechanism, and the rotating member thereby attempts to
rotate in the take-up direction, accompanying this, the friction
member connected to the rotating member attempts to rotate in the
take-up direction. Moreover, the friction member attempts to rotate
the brake spring in the take-up direction due to the friction
between the friction member and the brake spring.
[0045] Here, in the present webbing retractor, the end portion of
the brake spring at the pull-out direction (the one of the take-up
direction and the pull-out direction) side is anchored at the frame
which directly or indirectly supports the take-up shaft. Thus, even
if the brake spring attempts to rotate in the take-up direction,
the end portion of the brake spring at the pull-out direction side
cannot rotate following this rotation.
[0046] Accordingly, due to the brake spring attempting to rotate in
the take-up direction in the state in which the pull-out direction
side end portion thereof is anchored, the gap formed between the
pull-out direction side end portion and the take-up direction side
end portion of the brake spring narrows. The diameter of the entire
brake spring is thereby reduced in opposition to the elasticity of
the brake spring.
[0047] Due to the diameter of the brake spring being reduced, the
brake spring tightens around the friction member. In this way, the
frictional force between the friction member and the brake spring
increases.
[0048] The frictional force, which has increased in this way, works
to restrict rotation of the friction member in the take-up
direction. Due to rotation of the friction member in the take-up
direction being restricted by this frictional force, rotation in
the take-up direction of the rotating member, to which the friction
member is connected, is restricted. In this way, relative rotation
arises between the prime mover rotating body and the rotating
member.
[0049] In this way, in the above-described webbing retractor, the
frame can be included in the diameter forcibly reducing mechanism,
and the brake spring can be anchored at the frame, and the rotating
member can be made to rotate relative to the prime mover rotating
body. Moreover, due to the frame being included in the diameter
forcibly reducing mechanism, there is no need to provide a
separate, special member for forming the diameter forcibly reducing
mechanism, and the webbing retractor can be made compact and
lightweight.
[0050] Note that, in the above description, for convenience of
explanation, "the one" of the take-up direction and the pull-out
direction was the "pull-out direction", and "the other" was the
"take-up direction". However, the present invention is established
even if, conversely, "the one" is the "take-up direction" and "the
other" is the "pull-out direction". In this case, the phrases of
"pull-out direction" and "take-up direction" in the above
explanation are merely reversed, and detailed description of such a
case will therefore be omitted.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 is a front view showing the basics of the structure
of a webbing retractor relating to a first embodiment of the
present invention.
[0052] FIG. 2 is a perspective view showing the basics of a braking
mechanism of the webbing retractor relating to the first embodiment
of the present invention.
[0053] FIGS. 3A and 3B are side views showing the basics of the
structure of the braking mechanism, where FIG. 3A shows a usual
state and FIG. 3B shows a sliding-contact state.
[0054] FIG. 4 is an exploded perspective view of a clutch mechanism
of the webbing retractor relating to the first embodiment of the
present invention.
[0055] FIG. 5 is a side view showing the structure of the clutch
mechanism.
[0056] FIG. 6 is a side view of the clutch mechanism of FIG. 5, and
shows a state in which connecting members are engaged with a driven
shaft.
[0057] FIG. 7 is a side view of the clutch mechanism of FIG. 5, and
shows a state in which one connecting member has ridden up on an
addendum of an external tooth of the driven shaft.
[0058] FIG. 8 is a front view showing the basics of the structure
of a webbing retractor relating to a second embodiment of the
present invention.
[0059] FIG. 9 is an exploded perspective view of a clutch mechanism
of the webbing retractor relating to the second embodiment of the
present invention.
[0060] FIG. 10 is a side view showing the basics of a braking
mechanism of the webbing retractor relating to the second
embodiment of the present invention.
[0061] FIG. 11 is an exploded perspective view of the clutch
mechanism of the webbing retractor relating to the second
embodiment of the present invention.
[0062] FIG. 12 is a side view showing the structure of the clutch
mechanism.
[0063] FIG. 13 is a side view of the clutch mechanism of FIG. 12,
and shows a state in which a connecting mechanism engages a driven
shaft.
[0064] FIG. 14 is a front view showing the basics of the structure
of a webbing retractor relating to a third embodiment of the
present invention.
[0065] FIG. 15 is an exploded perspective view showing the basics
of the structure of a braking mechanism of the webbing retractor
relating to the third embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0066] The embodiments of the present invention may have the
following features.
[0067] In the webbing retractor of one embodiment, the driven shaft
is rotatably connected integrally with the take-up shaft. The
urging member has one end and another end and is elastically
deformable, and the one end is attached to the prime mover rotating
body, and the other end is held at the rotating member so as to be
able to push the rotating member. The urging member has a coil
spring.
[0068] The driven shaft has a peripheral surface, and the
connecting members are held at the prime mover rotating body so as
to be able to approach and move away from the driven shaft, and
when the prime mover rotating body is rotated, the connecting
members contact the peripheral surface of the driven shaft due to
the relative rotation, and connect the prime mover rotating body
and the driven shaft. The following structure is possible: a
plurality of teeth are formed at the peripheral surface of the
driven shaft, and the connecting members have pawl shapes which can
engage with any of the teeth, and at least one of the connecting
members contacts the tooth of the driven shaft so as to engage with
the tooth, and connects the prime mover rotating body and the
driven shaft.
[0069] In the webbing retractor of another embodiment, the
connecting members are roller-shaped, and due to the relative
rotation, the connecting members are pressed by the peripheral
surface of the driven shaft and connect the prime mover rotating
body and the driven shaft, and rotation of the prime mover rotating
body is thereby transmitted to the driven shaft.
[0070] In the webbing retractor of one embodiment, due to the
braking mechanism applying frictional force to the rotating member,
rotation of the rotating member is braked. The braking mechanism
may brake the rotating member when the prime mover rotating body is
driven to rotate at greater than a predetermined speed. The braking
mechanism may connect such that power can be transmitted from the
driving mechanism, i.e., motion of the braking mechanism for
braking operation is transmitted from the driving mechanism. The
braking mechanism may brake the rotating member interlockingly with
driving and rotating of the prime mover rotating body by the
driving mechanism.
[0071] In the webbing retractor of one embodiment, the rotating
member has a friction member which is attached to the rotating
member and rotates integrally with the rotating member, and the
braking mechanism has a braking member which slidingly contacts the
friction member, and the braking mechanism brakes due to the
braking member slidingly contacting the friction member. The
following structure is possible: the friction member is
substantially ring shaped, and the braking member is substantially
shaped as a ring having one end and another end, and the braking
member is disposed so as to surround one portion of an outer
peripheral surface of the friction member, and in a state in which
the one end of the braking member is held at the outer peripheral
surface of the friction member, the other end of the braking member
is connected to the driving mechanism and is pulled in a direction
of decreasing a diameter of the braking member when the driving
mechanism operates.
[0072] The webbing retractor of another embodiment further
comprises a frame which is fixed, and the friction member is
substantially ring shaped, and the braking member is substantially
shaped as a ring having one end and another end, and the braking
member is disposed so as to surround one portion of an outer
peripheral surface of the friction member, and in a state in which
the one end of the braking member is held at the outer peripheral
surface of the friction member, the other end of the braking member
is anchored at the frame so as to be pulled in a direction of
decreasing a diameter of the braking member when the friction
member is rotated.
[0073] In the webbing retractor of one embodiment, the prime mover
rotating body has an external gear which is ring shaped and has
external teeth for connection to the driving mechanism such that
the external gear can be driven and rotated; a base portion having
a holding portion for holding the plurality of connecting members,
the base portion being pivotally supported coaxially with the
rotating member; and at least one torque limiter provided between
the external gear and the base portion, so as to be able to
transmit torque in a predetermined range to the base portion from
the external gear.
[0074] The webbing retractor of one embodiment further comprises a
control unit controlling operation of the driving mechanism, and
when a rate of change in deceleration at a time when the vehicle
decelerates is greater than or equal to a predetermined value, the
control unit effects control so as to cause the driving mechanism
to operate. Further, when a distance to an obstacle which is
positioned ahead of the vehicle is less than a predetermined value,
the control unit effects control so as to cause the driving
mechanism to operate.
[0075] Hereinafter, embodiments of the present invention will be
described in detail with reference to the drawings.
STRUCTURE OF FIRST EMBODIMENT
(Overall Structure of Webbing Retractor 10)
[0076] A front sectional view showing the overall structure of a
webbing retractor 10 relating to a first embodiment of the present
invention is shown in FIG. 1. As shown in FIG. 1, the webbing
retractor 10 has a frame 12. The frame 12 has a back plate 14 which
is substantially plate-shaped. The webbing retractor 10 is mounted
to a vehicle body by the back plate 14 being fixed to the vehicle
body by unillustrated fasteners such as bolts or the like. A pair
of leg plates 16, 18 extend parallel to one another from the
transverse direction ends of the back plate 14. A spool 20, which
serves as a take-up shaft and is manufactured by die casting or the
like, is disposed rotatably between the leg plates 16, 18.
[0077] The spool 20 is structured by a spool main body 22 and a
pair of flange portions 24, 26, and is formed in a drum-shape on
the whole. The spool main body 22 is substantially hollow
cylindrical. The pair of flanges 24, 26 are formed in substantial
disc shapes at the end portions of the spool main body 22.
[0078] The proximal end portion of a webbing belt 28, which is
formed in the shape of an elongated strip, is fixed to the spool
main body 22 between the flange portions 24, 26. When the spool 20
is rotated in one direction around the axis thereof, the webbing
belt 28 is taken-up in the form of a roll on the outer peripheral
portion of the spool main body 22 from the proximal end side of the
webbing belt 28. Further, if the webbing belt 28 is pulled from the
distal end side thereof, the webbing belt 28, which is taken-up on
the outer peripheral portion of the spool main body 22, is
pulled-out. Accompanying this, the spool 20 rotates opposite to the
direction of rotation at the time of taking-up the webbing belt 28.
(Hereinafter, for convenience of explanation, the direction of
rotation at the time of taking-up the webbing belt 28 will be
called the "take-up direction", and is denoted by arrow A in the
related drawings. The direction of rotation of the spool 20 at the
time when the webbing belt 28 is pulled out will be called the
"pull-out" direction for convenience of explanation, and is denoted
by arrow B in the related drawings.)
[0079] The flange portion 24 one end side of the spool 20, which is
at the side opposite the flange portion 26 side of the spool 20,
passes substantially coaxially through a circular hole 30, which is
formed in the leg plate 16, and projects to the exterior of the
frame 12. A case 32 is disposed at the outer side of the frame 12
at the leg plate 16 side. The case 32 is disposed so as to oppose
the leg plate 16 along the axial direction of the spool 20, and is
fixed to the leg plate 16. The case 32 is, on the whole, open
toward the leg plate 16 side. The one end side of the spool 20
which passes through the circular hole 30 enters into the inner
side of the case 32, and is rotatably supported by the case 32.
[0080] Moreover, a spiral spring 34 is disposed at the interior of
the case 32. The end portion, at the outer side in the direction of
the spiral, of the spiral spring 34 is anchored on the case 32. The
end portion, at the inner side in the direction of the spiral, of
the spiral spring 34 is anchored on the spool 20. When the spoo 20
is rotated in the pull-out direction from a neutral state in which
no particular load is applied, urging force in the take-up
direction arises, and the spiral spring 34 urges the spool 20 in
the take-up direction. Accordingly, basically, when the tensile
force applied to the webbing belt 28 for pulling the webbing belt
28 out from the spool 20 is released, the urging force of the
spiral spring 34 rotates the spool 20 in the take-up direction, and
the webbing belt 28 is taken-up onto the spool 20.
[0081] On the other hand, the flange portion 26 side other end side
of the spool 20, which is opposite the flange portion 24 side
thereof, passes substantially coaxially through an internal teeth
ratchet hole 36 formed in the leg plate 18, and projects at the
exterior of the frame 12. A lock mechanism 38 is provided at the
outer side of the frame 12 at the leg plate 18 side. The lock
mechanism 38 has a case 40. The case 40 is disposed so as to oppose
the leg plate 18 along the axial direction of the spool 20, and is
fixed to the leg plate 18. Respective members forming the lock
mechanism 38, such as an inertial plate or an external gear, an
acceleration sensor, and the like (all of which are unillustrated),
are accommodated at the inner side of the case 40. Due to the spool
20 rotating suddenly in the take-up direction, the inertial plate
within the case 40 rotates relative to the spool 20, or the
acceleration sensor detects a state of rapid deceleration of the
vehicle and the inertial plate is forcibly rotated within the case
40 relative to the spool 20.
[0082] A pair of lock plates 42 are provided at the inner side of
the ratchet hole 36. The lock plates 42 are supported by a lock
base which is provided within the case 40 and rotates integrally
with the spool 20. When the inertial plate within the case 40
rotates in the pull-out direction relative to the lock base, the
inertial plate is guided by guide portions formed at the lock base,
and approaches the inner peripheral portion of the ratchet hole 36.
External teeth formed at the lock plates 42 mesh with the internal
teeth formed at the inner peripheral portion of the ratchet hole
36. Due to the external teeth formed at the lock plates 42 meshing
with the internal teeth formed at the inner peripheral portion of
the ratchet hole 36 in this way, rotation of the lock base in the
pull-out direction is restricted, and accordingly, rotation of the
spool 20 is restricted.
[0083] On the other hand, a motor 44 serving as a drive source is
disposed beneath the spool 20 between the leg plate 16 and the leg
plate 18. The motor 44 is electrically connected via a driver 46 to
a battery 48 mounted in the vehicle. Due to current from the
battery 48 flowing to the motor 44 via the driver 46, the motor 44
rotates an output shaft 50 in the forward direction or the reverse
direction. The driver 46 is connected to an ECU 52 formed by a
microcomputer or the like. The ECU 52 is connected to a forward
observation sensor 54.
[0084] The forward observation sensor 54 is provided in a vicinity
of the front end portion of the vehicle, and emits infrared rays
toward the region in front of the vehicle, and receives the
infrared rays which have been reflected by another vehicle or an
obstacle which has stopped or is traveling in front of the vehicle.
(Hereinafter, such objects, including vehicles which are traveling
or have stopped, will be called "obstacles" for convenience of
explanation.) The ECU 52 computes the distance to the obstacle
ahead on the basis of the time required for the forward observation
sensor 54 to receive light from the time the forward observation
sensor 54 emitted the infrared rays.
[0085] On the basis of an electrical signal outputted from the
forward observation sensor 54, the ECU 52 operates the driver 46
and controls the motor 44.
(Structure of Braking Mechanism 60)
[0086] On the other hand, a gear 56 is provided coaxially and
integrally with the distal end portion of the output shaft 50 of
the motor 44. The gear 56 meshes with a gear 62 which has external
teeth and which forms a braking mechanism 60. As shown in FIGS. 2,
3A and 3B, the braking mechanism 60 has a frame 64. The frame 64
has a pair of side walls 66 which are parallel to and oppose the
leg plates 16, 18 of the frame 12. The side walls 66 are connected
integrally to the rear surface side of the frame 12 by a back wall
68. On the whole, the frame 64 is formed, in plan view, in a
substantially concave shape which opens toward the front surface
side of the frame 12.
[0087] The gear 62 is provided such that the center of rotation
thereof is positioned between the side walls 66, and is rotatably
supported by a shaft 70 which passes through the side walls 66 and
is supported at the leg plate 16 of the frame 12. The gear 62 has a
larger diameter than and more teeth than the gear 56. Accordingly,
the rotation of the gear 56 is decelerated by being transmitted to
the gear 62. Moreover, a gear 72 is disposed at the side of the
gear 62 opposite the side at which the back wall 68 of the frame 64
is provided.
[0088] The gear 72 meshes with the gear 62 in a state in which the
gear 72 is pivotally supported by a shaft 74 whose both ends are
supported at the side walls 66. Accordingly, the gear 72 can rotate
around the gear 62 due to the rotation of the gear 62 being
transmitted thereto. Moreover, the shaft 74 which pivotally
supports the gear 72 extends to the interior of the frame 12. A
weight 76, which is formed in the shape of a solid cylinder and
which is substantially coaxial with the shaft 74, is fixed
integrally to this distal end portion of the shaft 74. The weight
76 is integral with the gear 72 via the shaft 74. The self-weight
of the gear 72 and the weight of the weight 76 are applied to the
gear 72.
[0089] On the other hand, one end of a tension coil spring 78 is
anchored on the back plate 68 of the frame 64. The other end of the
tension coil spring 78 is fixed to the leg plate 16 at a position
which is lower than the one end of the tension coil spring 78. The
urging force of the tension coil spring 78 is greater than the
gravity based on the weight of the weight 76 and the self-weight of
the gear 72 which are applied to the gear 72. The urging force is
applied such that the rear wall 68 side of the frame 64 is pulled
downward against the gravity applied to the gear 72.
[0090] Further, a braking piece 80, which is shaped as a plate
having a narrow width and which serves as a braking member, extends
from the top end portion of the rear wall 68. The braking piece 80
structures a clutch 90 which serves as a clutch mechanism and will
be described later. The braking piece 80 restricts rotation of a
friction ring 170 due to friction at the time when the braking
piece 80 abuts the outer peripheral portion of the friction ring
170 which structures the clutch mechanism and serves as a friction
member.
(Structure of Clutch 90)
[0091] On the other hand, as shown in FIG. 1, the clutch 90 is
provided at the radial direction side of the gear 62. Hereinafter,
the clutch 90 will be described with reference to FIGS. 4 through
7.
[0092] As shown in FIG. 4, the clutch 90 has a base plate 92
serving as an intermediate rotating body. The base plate 92 is
formed in the shape of a hollow cylinder which has a bottom and
whose axial direction dimension is extremely short (or in the shape
of a shallow tray). A substantially ring-shaped peripheral wall 96,
which serves as an intermediate peripheral wall, is formed along
the outer peripheral portion of a disc-shaped base portion 94 of
the base plate 92. A cover 98, which is shaped as a thin disc, is
attached to the open end at one axial direction end side of the
base plate 92 (the arrow C direction side in FIG. 4), such that the
open end of the base plate 92 is basically closed.
[0093] Engaging recesses 100 are formed at uniform intervals along
the peripheral direction in the outer peripheral portion of the
peripheral wall 96. An external gear 102 serving as a prime mover
rotating body is provided at the outer side of the peripheral wall
96. The external gear 102 is formed in a substantial ring shape
whose number of teeth is sufficiently larger than that of the gear
62, and is disposed coaxially with respect to the base plate 92.
The inner diameter dimension of the external gear 102 is
sufficiently larger than the outer diameter dimension of the
peripheral wall 96. An annular gap is formed between the inner
peripheral portion of the external gear 102 and the outer
peripheral portion of the peripheral wall 96. As shown in FIGS. 5
through 7, a plurality of torque limiters 104 are disposed
intermittently in the peripheral direction in this annular gap.
[0094] As shown in FIGS. 4 through 7, the torque limiters 104 are
plate-shaped metal pieces having thin widths and having a spring
property, and the widths thereof are smaller than the axial
direction dimension of the external gear 102. Engaging portions
106, which can enter into the aforementioned engaging recesses 100,
are formed at the both longitudinal direction end portions of each
of the torque limiters 104. Further, an engaging projection 108,
which is bent as if to project out in a direction substantially
opposite to the projecting direction of the engaging portions 106,
is formed substantially at the longitudinal direction center of
each of the torque limiters 104.
[0095] Engaging recesses 110 are formed at the inner peripheral
portion of the external gear 102 in correspondence with the
engaging projections 108. Due to the engaging portions 106 entering
into the engaging recesses 100 in the state in which the engaging
projections 108 are in the engaging recesses 110, the base plate 92
and the external gear 102 are connected substantially integrally
via the torque limiters 104. In this way, when the external gear
102 attempts to rotate relative to the base plate 92 around the
axis of the base plate 92, the torque limiters 104 also of course
attempt to rotate integrally together with the external gear
102.
[0096] However, due to the engaging portions 106 of the torque
limiters 104 being in the engaging recesses 100, when the engaging
portions 106 attempt to rotate along the peripheral direction of
the peripheral wall 96, the engaging recesses 100 interfere with
the engaging portions 106 such that rotation of the engaging
portions 106 is restricted. In this way, relative rotation of the
external gear 102 with respect to the base plate 92 is restricted,
and basically, the external gear 102 and the base plate 92 are
connected integrally.
[0097] However, as described above, because the torque limiters 104
are metal pieces having a spring property, if the torque generated
by the relative rotation of the external gear 102 with respect to
the base plate 92 is large enough to pull the engaging portions 106
out from the engaging recesses 100 against the spring force (urging
force) of the torque limiters 104, the interference of the engaging
recesses 100 with the engaging portions 106 is released. Therefore,
relative rotation of the external gear 102 with respect to the base
plate 92 becomes possible.
[0098] On the other hand, an adapter 112, which is substantially
hollow cylindrical and serves as a driven shaft, is disposed
substantially coaxially with the base plate 92 at the inner side of
the base plate 92. On the whole, the axial direction one end (the
arrow D direction side in FIG. 4) of the adapter 112 is pivotally
supported at a circular hole 115 formed in the center of the base
portion 94 (the base plate 92). A tubular portion 114, which is
hollow cylindrical and is formed coaxially at the other end of the
adapter 112, is pivotally supported at a circular hole 116 formed
in the cover 98.
[0099] A spacer 118, which is formed in a ring shape and of a
synthetic resin material, is disposed between the adapter 112 and
the base portion 94 of the base plate 92. The spacer 118 is
pivotally supported by the tubular portion 114 of the adapter 112.
One axial direction end surface of the spacer 118 abuts the base
portion 94, whereas the other axial direction end surface abuts the
end surface of the connecting portion where the main body portion
of the adapter 112 is connected to the tubular portion 114.
[0100] A fit-together hole 120, which passes through along the
axial direction of the adapter 112, is formed in the adapter 112.
The other axial direction end of the spool 20 is fit into the
fit-together hole 120, such that the adapter 112 and the spool 20
are connected together coaxially and integrally. Further, a
plurality of external teeth 122, which is an odd number of teeth,
are formed at uniform intervals at the outer peripheral portion of
the adapter 112.
[0101] Moreover, a pair of bosses 124 are formed at the base
portion 94 of the base plate 92 at the radial direction outer side
of the adapter 112. Each boss 124 is formed as a substantially
hollow cylinder, and stands erect from the base portion 94 toward
one side in the axial direction thereof. These bosses 124 are
formed so as to oppose one another across the circular hole 115. A
pawl 130 serving as a connecting member is provided at each boss
124.
[0102] The pawl 130 has a main body 132. The main body 132 is
formed in the shape of a ring whose inner diameter dimension is
extremely slightly larger than the outer diameter dimension of the
boss 124. Due to the main body 132 being fit together with the boss
124 such that the boss 124 passes through the main body 132, the
pawl 130 is pivotally supported so as to be freely rotatable around
the boss 124.
[0103] A connecting piece 134 is formed at a portion of the outer
periphery of the main body 132. The connecting piece 134 is formed
so as to extend, with respect to the main body 132, toward the
spool 20 take-up direction side, in the state in which the main
body 132 is pivotally supported at the boss 124. Moreover, the
connecting piece 134 is formed such that, due to the main body 132
rotating over a predetermined angle in the take-up direction around
the boss 124, the corner portion of a distal end 134A abuts the
outer peripheral portion of the adapter 112 between the external
tooth 122 and the external tooth 122 of the adapter 112.
[0104] The distal end 134A of the connecting piece 134 is formed as
an inclined surface which is inclined so as to correspond to the
pull-out direction side surfaces of the teeth of the adapter 112.
Due to the distal end 134A abutting and interfering with the
external tooth 122, rotation of the adapter 112 in the pull-out
direction is restricted.
[0105] Here, as described above, the bosses 124 are formed so as to
oppose one another across the circular hole 115. Therefore, in a
state in which the corner portions of the distal ends 134A of the
pawls 130 which have basically the same configurations contact the
outer peripheral surface of the adapter 112, the distal end 134A of
one of the pawls 130 is positioned, across the axial center of the
adapter 112, at the opposite side of the distal end 134A of the
other of the pawls 130. Accordingly, if the total number of
external teeth 122 formed at the outer peripheral portion of the
adapter 112 is an even number and the external tooth 122 is formed
at the opposite side, across the axial center of the adapter 112,
of any one of the external teeth 122, the distal ends 134A of the
both pawls 130 both abut the external teeth 122.
[0106] However, in the present embodiment, as mentioned above, the
total number of the external teeth 122 formed at the outer
peripheral portion of the adapter 112 is an odd number. Thus, in
the state in which the distal end 134A of the one pawl 130 is
abutting the external tooth 122, the distal end 134A of the other
pawl 130 has moved apart from the external tooth 122 along the
peripheral direction of the adapter 112 (i.e., the distal end 134A
of the other connecting piece 134 is not contacting the external
tooth 122).
[0107] On the other hand, a releasing piece 136 extends from the
outer peripheral portion of the main body 132. The releasing piece
136 is formed at the side of the main body 132 approximately
opposite the side at which the connecting piece 134 is formed. The
outer side surface of the releasing piece 136 is an inclined
surface which is directed toward the outer side in the radial
direction of the base plate 92 with respect to the pull-out
direction. By rotating the releasing piece 136 in the pull-out
direction, the connecting piece 134 rotates in the direction of
moving away from the outer peripheral portion of the adapter
112.
[0108] Further, the clutch 90 is provided with a rotating disc 140
serving as a rotating member. The rotating disc 140 has a
substantially plate-shaped base portion 142 whose direction of
thickness runs along the axial directions of the base plate 92 and
the adapter 112. A circular hole 144 is formed in the base portion
142. The inner diameter dimension of the circular hole 144 is
formed to be extremely slightly larger than the outer diameter
dimension of the tubular portion 114 formed coaxially with respect
to the outer peripheral portion of the adapter 112 at the axial
direction other end side of the adapter 112. By carrying out
assembly by making the tubular portion 114 pass through the
circular hole 144, the base portion 142, and thus, the rotating
disc 140 are pivotally supported at the adapter 112 so as to freely
rotate around the adapter 112.
[0109] Further, a pair of blocks 146 serving as a forcibly
connecting mechanism are formed at the base portion 94 side surface
of the base portion 142. The blocks 146 are formed so as to oppose
one another across the circular hole 144. Among the two portions
running along the outer periphery of the outer side of the circular
hole 144 between the pair of blocks 146, one of the bosses 124 is
positioned at one portion, and the other boss 124 is positioned at
the other portion which is at the opposite side of this one portion
across the circular hole 144.
[0110] A spring accommodating portion 148 is formed at the outer
peripheral portion of one of the pair of blocks 146 (the outer
peripheral surface of the block 146 which outer peripheral surface
runs along the radial direction of the circular hole 144). A
compression coil spring 150 serving as an urging member is
accommodated in the spring accommodating portion 148.
[0111] The compression coil spring 150 is accommodated in the
spring accommodating portion 148 in a state in which the
compression coil spring 150 bends around the center of the circular
hole 144. The take-up direction side end portion of the compression
coil spring 150 abuts a wall portion 148A of the spring
accommodating portion 148. The pull-out direction side end portion
of the compression coil spring 150 abuts an abutment wall 152 which
extends from the inner peripheral portion of the peripheral wall 96
of the base plate 92 and which enters into the spring accommodating
portion 148.
[0112] The rotating disc 140 is pivotally supported at the tubular
portion 114 of the adapter 112. Therefore, basically, the rotating
disc 140 freely rotates relative to not only the adapter 112 but to
the base plate 92 as well. However, as described above, the take-up
direction side end portion of the compression coil spring 150 abuts
the wall portion 148A of the spring accommodating portion 148, and
the pull-out direction side end portion of the compression coil
spring 150 abuts the abutment wall 152 of the base plate 92.
Therefore, when the base plate 92 attempts to rotate in the take-up
direction relative to the rotating disc 140, the abutment wall 152
pushes the rotating disc 140 in the take-up direction via the
compression coil spring 150, and makes the rotating disc 140 rotate
following the rotation of the base plate 92. Thus, provided that
torque, which is of a magnitude which can resist the urging force
of the compression coil spring 150, is not applied to the rotating
disc 140, rotation of the base plate 92 in the take-up direction
relative to the rotating disc 140 is limited.
[0113] Moreover, a pressing piece 154 is provided at the inner
peripheral portion of each block 146. These pressing pieces 154 are
disposed at the take-up direction sides of the pawls 130, and can
move relative to the blocks 146 (i.e., relative to the rotating
disc 140) along peripheral walls 156 formed at the blocks 146 so as
to curve coaxially with respect to the circular hole 144. Further,
compression coil springs 158 are provided at the sides of the
pressing pieces 154 opposite the sides at which the pawls 130 are
provided. The compression coil springs 158 are disposed in states
of being curved along the peripheral walls 156. One end of the
compression coil spring 158 is anchored at and connected to the end
portion of the pushing piece 154 at the side opposite the side
where the pawl 130 is provided. In contrast, the other end of the
compression coil spring 158 is, in a state of abutting an abutment
wall 160 which is formed at the rotating disc 140 at the side
opposite the pushing piece 154, anchored at and connected to a
projection (not illustrated) which is formed so as to project from
the abutment wall 160 toward the pushing piece 154.
[0114] Inclined surfaces 164 are formed at the transverse direction
outer ends of the connecting pieces 134 of the pawls 130, in
correspondence with the respective pushing pieces 154. The inclined
surface 164 is inclined outwardly in the radial direction of the
base plate 92 with respect to the take-up direction. In the state
in which the distal end 134A does not contact the outer peripheral
portion of the adapter 112, the inclined surface 164 opposes
(faces) the pushing piece 154 along the peripheral direction of the
base plate 92 and the rotating disc 140. The pushing piece 154 is
formed so as to abut the inclined surface 164 due to the base plate
92 rotating by a predetermined amount in the take-up direction
relative to the rotating disc 140. When, from this state of
abutment, the base plate 92 attempts to rotate even further in the
take-up direction relative to the rotating disc 140, the inclined
surface 164 is pushed in the pull-out direction by the pushing
piece 154. Due to this pushing force, the pawl 130 rotates in the
take-up direction around the boss 124.
[0115] At the take-up direction side end portion of each block 146
which runs along the peripheral direction of the rotating disc 140,
a pushing portion 166 is formed, and a releasing piece
accommodating portion 168 is formed further toward the axial center
of the rotating disc 140 than the pushing portion 166. The pushing
portion 166 is formed so as to correspond to the releasing piece
136 of the pawl 130 along the peripheral direction of the rotating
disc 140. The releasing piece 136 gradually curves toward the axial
center of the base plate 92 from the portion thereof connected to
the main body 132 (the proximal end portion thereof toward the
distal end side thereof. The (transverse direction) outer side
surface of the releasing piece 136 as well is curved in a similar
way.
[0116] Accordingly, when the base plate 92 rotates by a
predetermined amount in the pull-out direction relative to the
rotating plate 140, the pushing portions 166 abut the (transverse
direction) outer side surfaces of the releasing pieces 136. In this
state of abutment, when the base plate 92 is rotated further in the
pull-out direction relative to the rotating disc 140, the pushing
portions 166 push the distal end portions of the releasing pieces
136 in the take-up direction. Here, the distal ends of the
releasing pieces 136 are inclined surfaces which are inclined
toward the outer side in the radial direction of the rotating disc
140, with respect to the pull-out direction. Thus, due to the
pushing portions 166 pushing the distal ends of the releasing
pieces 136, the pushing portions 166 rotate the pawls 130 in the
pull-out direction around the bosses 124 and guide them to the
releasing piece accommodating portions 168.
[0117] Moreover, the friction ring 170 is disposed coaxially
between the cover 98 and the base portion 142 of the rotating disc
140. The friction ring 170 is formed in a ring shape on the whole.
A pair of tongue-shaped attachment pieces 172 extend from the inner
peripheral portion of the friction ring 170 so as to oppose one
another across the center of the friction ring 170. The attachment
pieces 172 are integrally connected to the base portion 142 of the
rotating disc 140 by fasteners such as screws or the like. In this
way, the rotating disc 140 and the friction ring 170 are integral.
The outer peripheral portion of the friction ring 170 corresponds
to the distal end of the aforementioned braking piece 80. Due to
the frame 64 rotating in the pull-out direction around the shaft
70, the distal end of the braking piece 80 slidingly contacts the
outer peripheral portion of the friction ring 170.
[0118] The external gear 102 of the clutch 90 having the
above-described structure meshes together with the gear 62.
OPERATION AND EFFECTS OF PRESENT EMBODIMENT
[0119] Next, the operation and effects of the present embodiment
will be described by way of explaining the operation of the present
webbing retractor 10.
(Basic Operation of Webbing Retractor 10)
[0120] First, the basic operation of the webbing retractor 10 will
be described.
[0121] In the present webbing retractor 10, in the state in which
the webbing belt 28 is taken-up and accommodated in the form of a
roll on the spool 20, when the webbing belt 28 is pulled while an
unillustrated tongue plate is pulled, the webbing belt 28 is pulled
out while the spool 20 is rotated in the pull-out direction against
the urging force of the spiral spring 34 which urges the spool 20
in the take-up direction. In this way, in the state in which the
webbing belt 28 is pulled out, the vehicle occupant seated in a
seat inserts the tongue plate in an unillustrated buckle device
while pulling the webbing belt 28 around the front of his/her body,
such that the tongue plate is held in the buckle device. The
webbing belt 28 is thereby set in a state of being applied to the
body of the vehicle occupant (hereinafter, this state will be
referred to simply as the "applied state").
[0122] When the webbing belt 28 is pulled out and the spool 20 is
rotated in the pull-out direction in order to apply the webbing
belt 28 to the body of a vehicle occupant, the spiral spring 34 is
wound tighter, such that the urging force of the spiral spring 34
which urges the spool 20 in the take-up direction increases.
Accordingly, in the aforementioned applied state, the urging force
of the spiral spring 34 works to make the webbing belt 28 be taken
up on the spool 20. Thus, basically, the webbing belt 28 is fit to
the body of the vehicle occupant due to this urging force, and the
webbing belt 28 restrains and holds the body of the vehicle
occupant by a force corresponding to the urging force at this
time.
[0123] On the other hand, when holding of the tongue plate by the
buckle device is released and the tongue plate comes out of the
buckle device, the force for maintaining the webbing belt 28 in the
state of being pulled-out against the urging force of the spiral
spring 34 is cancelled. Thus, the spool 20 is rotated in the
take-up direction by the urging force of the spiral spring 34. The
webbing belt 28 which has been pulled out is taken-up in the form
of a roll onto the outer peripheral portion of the spool 20 due to
the rotation of the spool 20 in the take-up direction. In this way,
the webbing belt 28 is accommodated.
[0124] Here, because the spool 20 is fit together with the adapter
112 of the clutch 90, when the spool 20 is rotated in order to
pull-out or take-up the webbing belt 28, the adapter 112 rotates.
However, in this state, if the adapter 112 merely rotates, the base
plate 92 and the rotating disc 140 do not rotate. Therefore, the
pawls 130 do not rotate. Accordingly, the external gear 102 does
not rotate. Accordingly, the rotation of the spool 20 is not
transmitted to the output shaft 50 of the motor 44 via the external
gear 102 and the gears 62, 56.
(Operation of Webbing Retractor 10 when Approaching an Obstacle
Ahead)
[0125] On the other hand, while the vehicle is traveling, the
forward observation sensor 54 detects the distance to an obstacle
which is in front of the vehicle. An electric signal having a
signal level corresponding to the distance to the obstacle is
outputted from the forward observation sensor 54. The electric
signal outputted from the forward observation sensor 54 is inputted
to the ECU 52. At the ECU 52, on the basis of the electric signal
from the forward observation sensor 54, it is judged whether or not
the distance to the obstacle is less than a predetermined
value.
[0126] Next, if it is judged at the ECU 52 that the distance to the
obstacle is less than the predetermined value, the ECU 52 outputs a
control signal to the driver 46, and makes current flow to the
motor 44 via the driver 46. In this way, the motor 44 is driven to
rotate forward at a speed of a predetermined value or more, and
rotates the output shaft 50 forward.
[0127] The rotation of the output shaft 50 is, while being
decelerated via the gears 56, 62, transmitted to the external gear
102 of the clutch 90, and rotates the external gear 102 in the
take-up direction at a rotational speed of a predetermined value or
more. The external gear 102 is mechanically connected to the base
plate 92 via the torque limiters 104. Thus, due to the external
gear 102 rotating in the take-up direction, the base plate 92
rotates integrally in the take-up direction.
[0128] When the base plate 92 rotates in the take-up direction, the
abutment wall 152 pushes the take-up direction side end portion of
the compression coil spring 150, and the compression coil spring
150 pushes the wall portion 148A of the spring accommodating
portion 148 by urging force. The rotating disc 140 thereby attempts
to rotate so as to follow rotation of the base plate 92.
[0129] On the other hand, as described above, when the rotation of
the output shaft 50 is transmitted to the gear 62 via the gear 56,
rotation is transmitted from the gear 62 to the gear 72, and the
gear 72 attempts to rotate downward around the gear 62 while
rotating around the shaft 74. However, the urging force of the
tension coil spring 78 is applied to the frame 64 at which the
shaft 74, which pivotally supports the gear 72, is supported. Thus,
the gear 72 cannot rotate downward around the gear 62. However, as
described above, the output shaft 50 rotates at a rotational speed
of a predetermined value or more, and this rotation is transmitted
to the gear 72. In this way, the resultant force of the force
applied to the gear 72 around the gear 62 and the gravity based on
the self-weight of the gear 72 and the weight of the weight 76,
exceeds the urging force of the tension coil spring 78. The gear
72, and consequently, the frame 64, are rotated around the shaft
70.
[0130] In this way, the braking piece 80 slidingly contacts the
outer peripheral portion of the friction ring 170. The friction,
which is generated between the braking piece 80 and the outer
peripheral portion of the friction ring 170, restricts rotation of
the friction ring 170, and accordingly, of the rotating disc 140
which is integral with the friction ring 170. In this way, relative
rotation arises between the base plate 92 and the rotating disc
140, and the base plate 92 can be rotated reliably in the take-up
direction with respect to the rotating disc 140.
[0131] In this way, when the base plate 92 rotates by a
predetermined amount or more in the take-up direction relative to
the rotating disc 140, the pushing pieces 154 provided at the
blocks 146 of the rotating disc 140 abut the connecting pieces 134
of the pawls 130. In this state, when the base plate 92 attempts to
rotate further in the take-up direction relative to the rotating
disc 140, the pushing pieces 154 push the inclined surfaces 164 of
the connecting pieces 134 in the pull-out direction. The pushing
forces applied to the inclined surfaces 164 act in the pull-out
direction and toward the inner side in the radial direction of the
rotating disc 140 and the base plate 92. The portions of the
forces, which portions act toward the radial direction inner sides,
rotate the pawls 130 in the take-up direction around the bosses
124. As shown in FIG. 6, due to the pawls 130 rotating in the
take-up direction around the bosses 124, the corner portions of the
distal ends 134A abut the outer peripheral portion of the adapter
112. In this state, the pawls 130 rotate together with the base
plate 92 in the take-up direction around the center of the base
plate 92, until the pawls 130 abut the external teeth 122 which are
adjacent at the take-up direction sides.
[0132] Then, in this state, the distal ends 134A abut the external
teeth 122. When the base plate 92 rotates further in the take-up
direction, the distal ends 134A of the pawls 130 push the external
teeth 122 in the take-up direction, and rotate the adapter 112, and
accordingly, the spool 20, in the take-up direction. Due to this
rotation of the spool 20, the webbing belt 28 is taken-up onto the
spool 20. In this way, looseness or so-called "slack" in the
webbing belt 28 is eliminated, and the force by which the webbing
belt 28 restrains the body of the vehicle occupant is improved.
Even if the vehicle occupant thereafter carries out the operation
of suddenly braking the vehicle such that a state of rapid
deceleration of the vehicle arises, the webbing belt 28 reliably
holds the body of the vehicle occupant.
[0133] In this way, when the motor 44 stops in the state in which
slack has been eliminated, rotation of the base plate 92 in the
take-up direction stops. When rotation of the base plate 92 stops,
the compression coil spring 150 pushes the rotating disc 140 in the
take-up direction by urging force, and rotates the rotating disc
140 in the take-up direction. When the rotating disc 140 rotates,
the pushing portions 166 abut the releasing pieces 136 of the pawls
130 and push the releasing pieces 136 in the take-up direction. Due
to the releasing pieces 136 receiving this pushing force, the pawls
130 rotate in the pull-out direction around the bosses 124, and as
shown in FIG. 5, the distal ends 134A of the connecting pieces 134
move away from the outer peripheral portion of the adapter 112. In
this way, the mechanical connection between the base plate 92 and
the adapter 112, i.e., the mechanical connection between the output
shaft 50 of the motor 44 and the compression coil spring 150, is
cancelled.
[0134] Here, in the present embodiment, as described above, the
total number of the external teeth 122 of the adapter 112 is an odd
number. In the state in which the distal end 134A of one of the
pawls 130 is abutting the external tooth 122, the distal end 134A
of the other pawl 130 is apart from the external tooth 122 along
the peripheral direction of the adapter 112, and is positioned at
an intermediate portion between the external tooth 122, which is
adjacent in the take-up direction along the peripheral direction of
the adapter 112, and the external tooth 122 which is adjacent in
the pull-out direction.
[0135] Namely, in the present embodiment, in the state in which the
distal ends 134A of the both pawls 130 abut the outer peripheral
portion of the adapter 112, the interval from the distal end 134A
of one of the pawls 130 to the distal end 134A of the other of the
pawls 130 is not an integer multiple of the pitch of the external
teeth 122. Thus, as shown in FIG. 7, even if the distal end 134A of
one of the pawls 130 abuts the addendum of the external tooth 122
at the time when the both pawls 130 are rotating around the bosses
124, the distal end of the other of the pawls 130 does not abut the
addendum of the external tooth 122, and abuts the outer peripheral
portion of the adapter 112 between the external teeth 122 which are
adjacent in the peripheral direction.
[0136] Accordingly, even if the distal end 134A of one of the pawls
130 abuts the addendum of the external tooth 122 and cannot mesh
with the external tooth 122, the distal end 134A of the other of
the pawls 130 reliably meshes with the external tooth 122 if the
base plate 92 rotates by substantially one-half of the pitch of the
external teeth 122. Thus, the rotation of the base plate 92 can
reliably and swiftly be transmitted to the adapter 112, and the
torque of the motor 44 can be transmitted to the spool 20.
[0137] Moreover, in the state in which the distal end 134A of one
of the pawls 130 abuts the addendum of the external tooth 122, the
connecting piece 134 abuts the pushing piece 154 in this state as
is. Here, even if the pushing piece 154 is integral with the
rotating disc 140, further rotation of the base plate 92 in the
take-up direction relative to the rotating disc 140 is restricted.
In this state, because the interference of the pushing piece 154
with the distal end of the other of the pawls 130 is insufficient,
the pushing piece 154 cannot rotate the other pawl 130 sufficiently
in the take-up direction. As a result, there is the possibility
that the distal end of the other of the pawls 130 cannot abut the
external tooth 122.
[0138] Here, in the present embodiment, as described above, the
connecting piece 134 abuts the pushing piece 154 with the distal
end 134A of the one pawl 130 abutting the addendum of the external
tooth 122. In this state, when the base plate 92 attempts to rotate
further in the take-up direction relative to the rotating disc 140,
as shown in FIG. 7, the distal end 134A of the pawl 130 pushes the
pushing piece 154 and displaces the pushing piece 154 in the
take-up direction, against the urging force of the compression coil
spring 158. In this way, the base plate 92 rotates in the take-up
direction relative to the rotating disc 140.
[0139] Thus, the pushing piece 154 corresponding to the other pawl
130 interferes with the distal end 134A of the other pawl 130, and
rotates the pawl 130 in the take-up direction. In this way, even if
the connecting piece 134 abuts the pushing piece 154 in a state in
which the distal end 134A of the one pawl 130 abuts the addendum of
the external tooth 122, the other pawl 130 can be made to mesh with
the external tooth 122 of the adapter 112, and the rotation of the
base plate 92 can be reliably transmitted to the adapter 112.
[0140] On the other hand, as described above, by rotating the spool
20 in the take-up direction by the torque of the motor 44, the
force by which the webbing belt 28 restrains the body of the
vehicle occupant is improved. However, until the slack is
eliminated, in the state in which the webbing belt 28 is wound on
the spool 20, the body of the vehicle occupant is an obstruction,
and basically, the webbing belt 28 cannot be taken-up any further
on the spool 20. In this state, if the spool 20 attempts to rotate
further in the take-up direction and take-up the webbing belt 28,
the webbing belt 28 is tightened against the body of the vehicle
occupant by a force which is greater than needed, which is not
preferable.
[0141] Here, as described above, if the spool 20 attempts to
take-up the webbing belt 28 any more than needed, the body of the
vehicle occupant is an obstruction to the taking-up of the webbing
belt 28. Tensile force of a magnitude corresponding to the take-up
force for the spool 20 to take the webbing belt 28 up is applied to
the webbing belt 28 from the body of the vehicle occupant. This
tensile force acts opposite to the direction in which the spool 20
takes up the webbing belt 28. Thus, the spool 20 is stopped due to
this tensile force being applied to the webbing belt 28.
[0142] In this state, the torque of the motor 44 is applied to the
spool 20 via the external gear 102, the base plate 92, the pawls
130 and the adapter 112. Thus, in the state in which the spool 20
is stopped, the external teeth 122 of the adapter 112 restrict
rotation of the pawls 130 around the center of the base plate 92,
and the pawls 130 restrict rotation of the base plate 92 in the
take-up direction. Moreover, via the torque limiters 104, the base
plate 92 restricts rotation of the external gear 102 in the take-up
direction.
[0143] Here, in this state in which the rotation of the external
gear 102 is limited by the base plate 92 via the torque limiters
104, if the external gear 102 attempts to rotate further in the
take-up direction and the torque at this time exceeds the spring
force of the torque limiters 104, the engaging portions 106 of the
torque limiters 104 come out from the engaging recesses 100. In
this way, the connection between the base plate 92 and the external
gear 102 is temporarily cancelled, and only the external gear 102
rotates in the take-up direction until the engaging portions 106
enter into the other, adjacent engaging recesses 100. In this way,
due to the connection between the base plate 92 and the external
gear 102 being cancelled, the transmission of the torque of the
external gear 102 to the base plate 92, i.e., the transmission of
the torque of the motor 44 to the spool 20, is cut-off. Thus, an
increase in the restraining force applied by the webbing belt 28
can be suppressed.
[0144] As described above, the clutch 90 used in the present
webbing retractor 10 not only has the function of transmitting
torque, but also can cut-off the transmission of torque by the
torque limiters 104 when an excessive torque is applied. Regardless
of the fact that the above-described effects can be obtained, the
widthwise dimension of the torque limiters 104 (the dimension
thereof along the axial direction of the external gear 102) is less
than the axial direction dimension of the external gear 102. The
rotating disc 140 and the torque limiters 104 are therefore all
disposed between the peripheral wall 96 of the base plate 92 and
the external gear 102 along the radial direction of the external
gear 102.
[0145] Moreover, members such as the pawl 130, the rotating disc
140 and the like as well are disposed between the peripheral wall
96 and the adapter 112. These members are accommodated at the inner
side of the external gear 102. Thus, the thickness dimension (the
axial direction dimension) of the clutch 90 is, in actuality, the
axial direction dimension of the external gear 102, and is
extremely thin.
[0146] In this way, because the clutch 90 having the torque
limiters 104 can be made thin, the present webbing retractor 10 can
be made compact.
STRUCTURE OF SECOND EMBODIMENT
[0147] Next, another embodiment of the present invention will be
described. Note that, in describing the respective embodiments
hereinafter, regions which are basically the same as those of the
previous embodiments (including the above-described first
embodiment) are denoted by the same reference numerals, and
detailed description thereof is omitted.
[0148] The structure of a webbing retractor 290 relating to a
second embodiment of the present invention is shown in schematic
front view in FIG. 8.
[0149] As shown in FIG. 8, the webbing retractor 290 relating to
the present embodiment differs from the webbing retractor 10
relating to the above-described first embodiment in that the
webbing retractor 290 does not have the braking mechanism 60 and
the clutch 90, and instead, is equipped with a braking mechanism
300 and a clutch 350 which serves as the clutch mechanism.
(Structure of Braking Mechanism 300)
[0150] As shown in FIGS. 8 and 9, a gear 56, which is provided
coaxially and integrally at the distal end portion of the output
shaft 50 of the motor 44, meshes with an external gear 302
structuring the braking mechanism 300. The number of teeth of the
gear 302 is sufficiently larger than that of the gear 56. The axial
direction ends of the gear 302 are pivotally supported at the leg
plate 16 of the frame 12 and a frame 301 of the braking mechanism
300.
[0151] At the leg plate 16 side of the gear 302, a gear 304, which
has a number of teeth which is sufficiently smaller than that of
the gear 302, is provided coaxially and integrally with respect to
the gear 302. Above the gear 304, a gear 306, which has more teeth
than the gear 304, is pivotally supported at the leg plate 16 and
the frame 301 in a state in which the gear 306 meshes with the gear
304. Moreover, above the gear 306, the external gear 102, which
serves as a prime mover rotating body forming the clutch 350 which
will be described later, meshes with the gear 306. The rotation of
the output shaft 50 is decelerated and transmitted to the external
gear 102 via the gears 56, 302, 304, 306.
[0152] On the other hand, an arm 308 is provided at the leg plate
16 side of the gear 304. The arm 308 is a plate-shaped member whose
longitudinal direction runs along the rotation radial direction of
the gear 302 and whose direction of thickness runs along the axial
direction of the gear 302. A substantially circular spring
accommodating portion 310 is formed at the proximal end side, in
the longitudinal direction, of the arm 308 (see FIG. 10).
[0153] A friction spring 312 is accommodated in the spring
accommodating portion 310. The friction spring 312 is formed on the
whole in a substantial ring shape. The inner peripheral portion of
the friction spring 312 slidingly contacts a shaft portion 314
which is integral with the gear 304. Further, the both peripheral
direction ends of the friction spring 312 bend outwardly in the
radial direction.
[0154] A wall portion 316 is formed in the spring accommodating
portion 310 in correspondence with the region between the bent both
ends of the friction spring 312. When the friction spring 312
attempts to rotate around the shaft portion 314 with respect to the
arm 308, one of the both ends of the friction spring 312 interferes
with the wall portion 316, such that the friction spring 312 pushes
the wall portion 316 in the direction of rotation thereof.
[0155] On the other hand, a shaft portion 318 is formed to project
from the distal end side of the arm 308 toward the gear 302. The
proximal end portion of a lever 320 is pivotally supported at the
shaft portion 318 so as to be freely rotatable around the shaft
portion 318. The lever 320 is a plate-shaped member whose
longitudinal direction runs along the radial direction of the shaft
portion 318, and whose direction of thickness is along the axial
direction of the gear 302. A through hole 322, which passes through
in the direction of thickness, is formed at the longitudinal
direction distal end side of the lever 320. The pull-out direction
side end portion of a brake spring 324, which is formed in a
substantial ring shape, is fit into the through hole 322.
(Structure of Clutch 350)
[0156] On the other hand, as shown in FIG. 11, the clutch 350,
which has the external gear 102 which structures the clutch 350, is
equipped with the base plate 92. The base plate 92 is formed in the
shape of a hollow cylinder which has a bottom and whose axial
direction dimension is extremely short (or in the shape of a
shallow tray). The substantially ring-shaped peripheral wall 96 is
formed along the outer peripheral portion of the disc-shaped base
portion 94 of the base plate 92. The cover 98, which is shaped as a
thin disc, is attached to the open end at one axial direction end
side of the base plate 92 (the arrow C direction side in FIG. 11),
such that the open end of the base plate 92 is basically
closed.
[0157] The engaging recesses 100 are formed at uniform intervals
along the peripheral direction in the outer peripheral portion of
the peripheral wall 96. The external gear 102, which is
substantially ring-shaped and which has a number of teeth which is
sufficiently larger than that of the gear 302, is disposed
coaxially with the base plate 92 at the outer side of the
peripheral wall 96. The inner diameter dimension of the external
gear 102 is sufficiently larger than the outer diameter dimension
of the peripheral wall 96. An annular gap is formed between the
inner peripheral portion of the external gear 102 and the outer
peripheral portion of the peripheral wall 96. The plurality of
torque limiters 104 are disposed intermittently in the peripheral
direction in this annular gap.
[0158] The torque limiters 104 are plate-shaped metal pieces having
thin widths and having a spring property. The engaging portions
106, which can enter into the aforementioned engaging recesses 100,
are formed at the both longitudinal direction end portions of each
of the torque limiters 104. Further, the engaging projection 108,
which is bent as if to project out in a direction substantially
opposite to the projecting direction of the engaging portions 106,
is formed substantially at the longitudinal direction center of
each of the torque limiters 104.
[0159] The engaging recesses 110 are formed at the inner peripheral
portion of the external gear 102 in correspondence with the
engaging projections 108. Due to the engaging portions 106 entering
into the engaging recesses 100 in the state in which the engaging
projections 108 are in the engaging recesses 110, the base plate 92
and the external gear 102 are connected substantially integrally
via the torque limiters 104.
[0160] In this way, when the external gear 102 attempts to rotate
relative to the base plate 92 around the axis of the base plate 92,
the torque limiters 104 also of course attempt to rotate integrally
together with the external gear 102. However, due to the engaging
portions 106 of the torque limiters 104 being in the engaging
recesses 100, when the engaging portions 106 attempt to rotate
along the peripheral direction of the peripheral wall 96, the
engaging recesses 100 interfere with (engage) the engaging portions
106 such that rotation of the engaging portions 106 is
restricted.
[0161] In this way, relative rotation of the external gear 102 with
respect to the base plate 92 is restricted, and basically, the
external gear 102 and the base plate 92 are connected
integrally.
[0162] However, as described above, because the torque limiters 104
are metal pieces having a spring property, if the torque generated
by the relative rotation of the external gear 102 with respect to
the base plate 92 is large enough to pull the engaging portions 106
out from the engaging recesses 100 against the spring force (urging
force) of the torque limiters 104, the interference (engagement) of
the engaging recesses 100 with the engaging portions 106 is
released, and relative rotation of the external gear 102 with
respect to the base plate 92 becomes possible.
[0163] On the other hand, an adapter 352, which is substantially
hollow cylindrical and serves as a driven shaft and an inner side
rotating body, is disposed substantially coaxially with respect to
the base plate 92 at the inner side of the base plate 92. The
adapter 352 is formed, on the whole, in the shape of a thick ring
whose direction of thickness (axial direction) runs along the axial
direction of the base plate 92. The above-described spool 20 is fit
integrally and coaxially into the adapter 352. The spacer 118,
which is formed in a ring shape and of a synthetic resin material,
is fit into the base portion 94 side end portion of the adapter
352. One axial direction end surface of the spacer 118 (the side in
the direction opposite to the direction of arrow C in FIG. 11)
abuts the base portion 94.
[0164] A plurality (three in the present embodiment) of connecting
rollers 354, each of which serves as a connecting member, are
disposed at the radial direction outer side of the adapter 352. The
connecting roller 354 is formed, on the whole, substantially in the
shape of a solid cylinder. The axial direction of the connecting
roller 354 is the axial direction of the adapter 352, i.e.,
substantially the same direction as the axial direction of the
spool 20. Moreover, a lock piece 356 serving as a guiding member is
provided between the connecting roller 354 and the peripheral wall
96 of the base plate 92.
[0165] The lock pieces 356 are formed of a material which has
relatively high strength (e.g., a material which has mechanical
strength which is sufficiently higher than that of the material
forming the base plate 92). The lock pieces 356 are fixed
integrally with the peripheral wall 96 in a state in which the lock
pieces 356 are fit in piece mounting portions 358 which are formed
at the inner peripheral portion of the peripheral wall 96.
[0166] A guide surface 360 is formed at the surface of the lock
piece 356 at the side thereof which faces the connecting roller 354
along the radial direction of the adapter 352 and the base plate
92. The guide surface 360 is formed as an inclined surface or a
curved surface whose distance from the outer peripheral surface of
the adapter 352 gradually becomes shorter along the pull-out
direction around the axial center of the adapter 352. Due to the
connecting rollers 354 rotating or moving in the pull-out direction
so as to follow along the guide surfaces 360, the connecting
rollers 354 are forcibly made to approach the outer peripheral
surface of the adapter 352.
[0167] Moreover, in a vicinity of the pull-out direction side end
portion of the guide surface 360, the interval (distance) from the
outer peripheral surface of the adapter 352 is set to be the same
as or extremely slightly shorter than the outer diameter dimension
of the connecting roller 354. Thus, when the connecting roller 354
moves to a vicinity of the pull-out direction side end portion of
the guide surface 360, the connecting roller 354 contacts the outer
peripheral portion of the adapter 352.
[0168] Moreover, a rotating disc 362 serving as a forcibly
connecting member is provided at the side of the connecting rollers
354 opposite the side at which the base portion 94 of the base
plate 92 is provided. The rotating plate 362 has a plate-shaped
base portion 366 in which is formed a circular hole 364 through
which the spool 20 passes. Basically, the rotating plate 362
rotates freely around the axial center of the spool 20 relative to
the spool 20 and the base plate 92.
[0169] A plurality of peripheral walls 368 are formed at the
periphery of the circular hole 364 of the base portion 366. The
peripheral walls 368 are formed at uniform intervals on an
imaginary circumference which is concentric with the circular hole
364. The number of the peripheral walls 368 which are formed is the
same as the number of the connecting rollers 354. The connecting
rollers 354 are disposed between the peripheral walls 368. A
restricting wall 370, which serves as a forcibly connecting
mechanism, is formed at the pull-out direction side end portion
(the end portion in the direction of arrow B in FIGS. 11 and 12) of
the peripheral wall 368 around the axial center of the adapter 352.
When the connecting roller 354 attempts to move by a predetermined
amount or more in the take-up direction around the axial center of
the adapter 352, the restricting wall 370 interferes with the outer
peripheral portion of the connecting roller 354 so as to limit
movement of the connecting roller 354.
[0170] In contrast, a wedge-shaped portion 372 serving as a
forcibly releasing mechanism is formed at the take-up direction
side end portion (the end portion in the direction of arrow A in
FIGS. 11 and 12) of the peripheral wall 368 around the axial center
of the adapter 352. The wedge-shaped portion 372 is formed in a
taper shape whose thickness gradually decreases in the take-up
direction. Due to the rotating plate 362 rotating in the take-up
direction with respect to the connecting rollers 354, the
wedge-shaped portions 372 interfere with the outer peripheral
portions of the connecting rollers 354 in a vicinity of the outer
peripheral portion of the adapter 352, and push the connecting
rollers 354 in a direction of moving away from the outer peripheral
portion of the adapter 352.
[0171] A spring attaching portion 374 is formed at one of the
plurality of the peripheral walls 368. The compression coil spring
150 serving as an urging member is attached to the spring attaching
portion 374. The compression coil spring 150 is curved such that
the axial direction thereof approximately runs alone the inner
peripheral configuration of the peripheral wall 96. The take-up
direction side end portion of the compression coil spring 150 abuts
a wall portion 374A of the spring attaching portion 374, whereas
the pull-out direction side end portion of the compression coil
spring 150 abuts an abutment wall 376 formed at the inner
peripheral portion of the peripheral wall 96.
[0172] In this way, the rotating disc 362 basically is freely
rotatable around the axial center of the adapter 352 relative to
the adapter 352 and the base plate 92. However, when the base plate
92 attempts to rotate in the take-up direction relative to the
rotating disc 362, the abutment wall 376 presses the other end
portion of the compression coil spring 150 in the take-up
direction. In this way, the increased urging force of the
compression coil spring 150 pushes the wall portion 374A in the
take-up direction, and rotates the rotating disc 362 in the take-up
direction.
[0173] Accordingly, when the base plate 92 attempts to rotate in
the take-up direction relative to the rotating disc 362, the
rotating disc 362 attempts to follow the rotation of the base plate
92 due to the urging force of the compression coil spring 150.
[0174] On the other hand, at the side of the cover 98 opposite the
side at which the rotating disc 362 is disposed (i.e., at the outer
side of the cover 98), a friction ring 378 serving as a friction
member is disposed coaxially with respect to the adapter 352. The
friction ring 378 is formed in a substantial ring shape on the
whole. An annular accommodating groove 380, which accommodates the
aforementioned brake spring 324, is formed in the outer peripheral
portion of the friction ring 378. The outer diameter dimension of
the accommodating groove 380 at the floor portion of the
accommodating groove 380 is substantially equal to the inner
diameter dimension of the brake spring 324. The inner peripheral
portion of the brake spring 324 slidingly contacts the floor
portion of the accommodating groove 380.
[0175] A plurality (three in the present embodiment) of
tongue-shaped attachment pieces 382 extend from the inner
peripheral portion of the friction ring 378. The attachment pieces
382 are integrally connected to the base portion 366 of the
rotating disc 362 by fasteners such as screws or the like which
pass through openings 384 formed in the cover 98. In this way, the
rotating disc 362 and the friction ring 378 are integral.
[0176] The external gear 102 of the clutch 350 having the
above-described structure meshes with the gear 306.
OPERATION AND EFFECTS OF SECOND EMBODIMENT
[0177] Next, the operation and effects of the present embodiment
will be described by way of explaining the operation of the present
webbing retractor 290.
(Operation of Webbing Retractor 290 when Approaching an Obstacle
Ahead)
[0178] In the present embodiment, when the vehicle is traveling,
the forward observation sensor 54 detects the distance to an
obstacle ahead of the vehicle. An electric signal, which has a
signal level corresponding to the distance to the obstacle, is
outputted from the forward observation sensor 54.
[0179] The electric signal outputted from the forward observation
sensor 54 is inputted to the ECU 52. At the ECU 52, on the basis of
the electric signal from the forward observation sensor 54, it is
judged whether or not the distance to the obstacle is less than a
predetermined value.
[0180] Next, when it is judged at the ECU 52 that the distance to
the obstacle is less than a predetermined value, the ECU 52 outputs
a control signal to the driver 46, and makes current flow to the
motor 44 via the driver 46. In this way, the motor 44 is driven to
rotate forward at a speed which is greater than or equal to a
predetermined value, and the output shaft 50 is rotated forward.
The rotation of the output shaft 50 is transmitted to the external
gear 102 of the clutch 350 while being decelerated via the gears
56, 302, 304, 306, and rotates the external gear 102 in the take-up
direction at a rotational speed of a predetermined value or
more.
[0181] The external gear 102 is mechanically connected to the base
plate 92 via the torque limiters 104. Thus, due to the external
gear 102 rotating in the take-up direction, the base plate 92
rotates integrally in the take-up direction.
[0182] When the base plate 92 rotates in the take-up direction, the
abutment wall 376 presses the pull-out direction side end portion
of the compression coil spring 150, and further, the compression
coil spring 150 presses the wall portion 148A of the spring
accommodating portion 148 by urging force. The rotating disc 362
thereby attempts to rotate so as to follow the base plate 92.
[0183] On the other hand, as described above, when the rotation of
the output shaft 50 is transmitted to the gear 302 via the gear 56
and the gear 302 rotates, the shaft portion 314 rotates. Due to the
shaft portion 314 rotating, the frictional force generated between
the shaft portion 314 and the inner peripheral portion of the
friction spring 312 attempts to rotate the friction spring 312. Due
to the transmitted torque, the friction spring 312 pushes the wall
portion 316, and rotates the arm 308 around the shaft portion 314
(see FIG. 10).
[0184] Due to the arm 308 rotating, the proximal end portion of the
lever 320 rotates around the shaft portion 314. In this way, the
lever 320 rotates one end of the brake spring 324 (the end portion
at the side engaged with the distal end of the lever 320) in the
pull-out direction (the direction of arrow B in FIGS. 10, 11 and
12).
[0185] As described above, the inner peripheral portion of the
brake spring 324 slidingly contacts the floor portion of the
accommodating groove 380 of the friction ring 378. Thus, due to the
brake spring 324 rotating, frictional force is generated between
the brake spring 324 and the floor portion of the accommodating
groove 380.
[0186] This frictional force works to restrict rotation of the
brake spring 324. Thus, the other end side of the brake spring 324
does not follow the rotation of the one end side. In this way, the
brake spring 324 tightens against the floor portion of the
accommodating groove 380. The brake spring 324 attempts to rotate
the friction ring 378, and consequently, the rotating disc 362
which is integral with the friction ring 378, in the pull-out
direction. The base plate 92 rotates in the take-up direction
relative to the rotating disc 362 due to this rotation of the
rotating disc 362 itself in the pull-out direction and due to the
torque received at the external gear 102.
[0187] In this way, when the base plate 92 rotates in the take-up
direction relative to the rotating disc 362, the guide surfaces 360
of the lock pieces 356 fixed to the base portion 94 of the base
plate 92 push the connecting rollers 354 and rotate the connecting
rollers 354 in the take-up direction around the axial center of the
adapter 352. When the connecting rollers 354 rotate by a
predetemmined amount, the restricting walls 370 interfere with the
outer peripheral portions of the connecting rollers 354, such that
the rotation of the connecting rollers 354 is restricted.
[0188] Due to the guide surfaces 360 further pushing the connecting
rollers 354 in this state, the connecting rollers 354 are moved so
as to approach the outer peripheral portion of the adapter 352. Due
to the guide surfaces 360 pushing the connecting rollers 354 until
the connecting rollers 354 contact the outer peripheral portion of
the adapter 352, the connecting rollers 354 are sandwiched between
the outer peripheral portion of the adapter 352 and the guide
surfaces 360. The connecting rollers 354 press-contact both the
outer peripheral portion of the adapter 352 and the guide surfaces
360 (see FIG. 13).
[0189] In this way, the rotation of the base plate 92 is
transmitted to the adapter 352 via the lock pieces 356 and the
connecting rollers 354. The adapter 352, and accordingly, the spool
20 which is integral with the adapter 352, are rotated in the
take-up direction.
[0190] The webbing belt 28 is taken-up onto the spool 20 due to the
rotation of the spool 20. In this way, looseness or so-called
"slack" in the webbing belt 28 is eliminated, and the force by
which the webbing belt 28 restrains the body of the vehicle
occupant is improved. Even if the vehicle occupant thereafter
carries out the operation of suddenly braking the vehicle such that
a state of rapid deceleration of the vehicle arises, the webbing
belt 28 reliably holds the body of the vehicle occupant.
[0191] In this way, when the motor 44 stops in the state in which
slack has been eliminated, rotation of the base plate 92 in the
take-up direction stops. When rotation of the base plate 92 stops,
the compression coil spring 150 pushes the rotating disc 362 in the
take-up direction by urging force, and rotates the rotating disc
362 in the take-up direction.
[0192] When the rotating disc 362 rotates, the wedge-shaped
portions 372 push the outer peripheral portions of the connecting
rollers 354, and move the connecting rollers 354 away from the
outer peripheral portion of the adapter 352. In this way, the
mechanical connection between the base plate 92 and the adapter
352, i.e., the mechanical connection between the output shaft 50 of
the motor 44 and the compression coil spring 150, is cancelled (see
FIG. 12).
[0193] In this way, in the present embodiment, the wedge-shaped
portions 372 forcibly move the connecting rollers 354 away from the
outer peripheral portion of the adapter 352. Thus, the state of
press-contact between the connecting rollers 354 and the outer
peripheral portion of the adapter 352 is not unnecessarily
maintained due to frictional force or the like which arises between
the connecting rollers 354 and the outer peripheral portion of the
adapter 352.
[0194] As described above, the connecting rollers 354 move by being
pressed by the guide surfaces 360 of the lock pieces 356, and
press-contact the outer peripheral portion of the adapter 352.
However, when the connecting rollers 354 press-contact the outer
peripheral portion of the adapter 352 due to sudden rotation of the
base plate 92, a great load is applied to the lock pieces 356 as
well.
[0195] Here, in the present embodiment, the lock pieces 356 are
basically structured as members which are separate from the base
plate 92. Thus, it is possible to improve the mechanical strength
of only the lock pieces 356. Therefore, even if the weight
increases by forming the lock pieces 356 of a material having
strength which can sufficiently withstand the aforementioned load,
the increase in weight is limited to the lock pieces 356 alone.
[0196] Moreover, by improving the mechanical strength of the lock
pieces 356, the mechanical strength of the base plate 92 overall is
not increased more than needed. Thus, a relatively light-weight
material can be used for the entire base plate 92, except for the
lock pieces 356. Thus, the entire clutch 350 can be made to be
lighter weight.
[0197] Moreover, as described above, the connecting rollers 354
move by being pressed by the guide surfaces 360. Thus, the period
of time from the start of rotation of the base plate 92 to the time
when the connecting rollers 354 press-contact the outer peripheral
surface of the adapter 352, differs slightly in accordance with the
angle of inclination or the radius of curvature of the guide
surfaces 360.
[0198] Here, in the present embodiment, as described above, the
lock pieces 356 are formed as separate members independent of the
base plate 92. Thus, plural types of lock pieces 356, at which the
angles of inclination or the radii of curvature of the guide
surfaces 360 are different, are prepared and the type to be used is
appropriately selected in accordance with the specifications or the
requirements of the vehicle or the like. In this way, the setting
of the period of time until the connecting rollers 354
press-contact the outer peripheral surface of the adapter 352 can
be changed easily without changing the parts other than the lock
pieces 356, such as the base plate 92 or the like.
[0199] On the other hand, in the present embodiment, as described
above, the rotation of the rotating disc 362 following the rotation
of the base plate 92 is forcibly restricted by the braking
mechanism 300, and further, the rotating disc 362 is forcibly
relatively rotated in the pull-out direction. In this way, relative
rotation in the take-up direction of the base plate 92 with respect
to the rotating disc 362 can be generated quickly and reliably.
Thus, the mechanical connection between the base plate 92 and the
adapter 352 due to the above-described movement of the connecting
rollers 354 can be carried out quickly and reliably.
[0200] As described above, by rotating the spool 20 in the take-up
direction by the torque of the motor 44, the force by which the
webbing belt 28 restrains the body of the vehicle occupant is
improved. However, until the slack is eliminated, in the state in
which the webbing belt 28 is wound on the spool 20, the body of the
vehicle occupant is an obstruction, and basically, the webbing belt
28 cannot be taken-up any further onto the spool 20.
[0201] In this state, if the spool 20 attempts to rotate further in
the take-up direction and take-up the webbing belt 28, the webbing
belt 28 tightens against the body of the vehicle occupant by a
force which is greater than needed, which is not preferable.
[0202] Here, as described above, if the spool 20 attempts to
take-up the webbing belt 28 any more than needed, the body of the
vehicle occupant is an obstacle to the taking-up of the webbing
belt 28. Tensile force of a magnitude corresponding to the take-up
force for the spool 20 to take the webbing belt 28 up is applied to
the webbing belt 28 from the body of the vehicle occupant. This
tensile force acts opposite to the direction in which the spool 20
takes up the webbing belt 28. Thus, the spool 20 is stopped due to
this tensile force being applied to the webbing belt 28.
[0203] In this state, the torque of the motor 44 is applied to the
spool 20 via the external gear 102, the base plate 92, the
connecting rollers 354 and the adapter 352. Thus, in the state in
which the spool 20 is stopped, the connecting rollers 354, which
are nipped between the adapter 352 and the guide surfaces 360,
restrict rotation of the base plate 92 in the take-up direction via
the lock pieces 356. Moreover, via the torque limiters 104, the
base plate 92 restricts rotation of the external gear 102 in the
take-up direction.
[0204] Here, in this state in which the rotation of the external
gear 102 is limited by the base plate 92 via the torque limiters
104, if the external gear 102 attempts to rotate further in the
take-up direction and the torque at this time exceeds the spring
force of the torque limiters 104, the engaging portions 106 of the
torque limiters 104 come out from the engaging recesses 100. In
this way, the connection between the base plate 92 and the external
gear 102 is temporarily cancelled, and only the external gear 102
rotates in the take-up direction until the engaging portions 106
enter into the other, adjacent engaging recesses 100.
[0205] In this way, due to the connection between the base plate 92
and the external gear 102 being cancelled, the transmission of the
torque of the external gear 102 to the base plate 92, i.e., the
transmission of the torque of the motor 44 to the spool 20, is
cut-off. Thus, an increase in the restraining force applied by the
webbing belt 28 can be suppressed.
[0206] Moreover, at the clutch 350, the torque limiters 104 are
disposed between the external gear 102 and the peripheral wall 96,
and the connecting rollers 354 and the rotating disc 362 are
disposed between the peripheral wall 96 and the adapter 352. Thus,
the entire thickness dimension of the clutch 350 can be made to be
about the axial direction dimension of the external gear 102. In
this way, the clutch 350 can be made thin, and the webbing
retractor 290 can be made compact.
[0207] In the present embodiment, the ECU 52 drives the motor 44
via the driver 46 on the basis of the signal from the forward
observation sensor 54 when the distance to an obstacle ahead is
less than or equal to a given value. However, a structure is
possible in which the motor 44 is driven in a case in which, for
example, a state of rapid deceleration of the vehicle is detected
by an acceleration sensor.
STRUCTURE OF THIRD EMBODIMENT
[0208] Next, a third embodiment of the present invention will be
described.
[0209] The basics of the structure of a webbing retractor 390
relating to the present embodiment are shown in front view in FIG.
14. The basics of the structure of the webbing retractor 390 are
shown in exploded perspective view in FIG. 15. As shown in these
figures, in the same way as the webbing retractor 290 relating to
the above-described second embodiment, the webbing retractor 390
has the gears 302, 304, 306.
[0210] However, the present webbing retractor 390 does not have the
arm 308 and the lever 320. Accordingly, in the present embodiment,
the gears 302, 304, 306 do not structure the braking mechanism, and
are merely a reduction gear train for decelerating the rotation of
the output shaft 50 of the motor 44 and transmitting it to the
external gear 102.
[0211] In this way, the present webbing retractor 390 differs from
the webbing retractor 290 relating to the second embodiment in that
the webbing retractor 390 does not have the braking mechanism 300.
However, the present webbing retractor 390 does have the clutch
mechanism 350. Further, the webbing retractor 390 also has the
friction ring 378. As shown in FIGS. 14 and 15, a brake spring 392,
which forms the braking mechanism in the present embodiment, is
accommodated in the accommodating groove 380 of the friction spring
378 instead of the brake spring 324. The brake spring 392 is
basically the same as the brake spring 324. However, the pull-out
direction side end portion of the brake spring 392 is directed in
the direction opposite that of the brake spring 324, and enters
into a hole portion 394 formed in the leg plate 16.
[0212] Namely, in the present embodiment, when the rotation of the
output shaft 50 of the motor 44 is transmitted to the external gear
102 via the gears 56, 302, 304, 306 and the external gear 102
rotates in the take-up direction, the abutment wall 376 attempts to
rotate the compression coil spring 150 in the take-up direction.
Moreover, the compression coil spring 150 presses the wall portion
374A of the spring attaching portion 374, and attempts to rotate
the rotating disc 362 in the take-up direction. In this way, the
friction ring 378, which is integral with the rotating disc 362,
attempts to rotate in the take-up direction while following the
brake spring 392 due to the frictional resistance.
[0213] However, the pull-out direction side end portion of the
brake spring 392 is in the hole portion 394 formed in the leg plate
16. Thus, rotation of the brake spring 392 itself is restricted. In
this state, the brake spring 392 attempts, by friction, to restrict
rotation of the friction ring 378 against the urging force of the
compression coil spring 150. Thus, relative rotation arises between
the rotating disc 362 and the external gear 102.
[0214] Due to relative rotation arising between the rotating disc
362 and the external gear 102 in this way, as explained in the
second embodiment as well, the connecting rollers 354 are moved so
as to approach the outer peripheral portion of the adapter 352, and
are nipped between the outer peripheral portion of the adapter 352
and the guide surfaces 360. The connecting rollers 354
press-contact both the outer peripheral portion of the adapter 352
and the guide surfaces 360 (see FIG. 13).
[0215] In this way, the rotation of the base plate 92 is
transmitted to the adapter 352 via the lock pieces 356 and the
connecting rollers 354. The adapter 352, and accordingly, the spool
20 which is integral with the adapter 352, are rotated in the
take-up direction.
[0216] Due to this rotation of the spool 20, the webbing belt 28 is
taken-up onto the spool 20. In this way, looseness or so-called
"slack" in the webbing belt 28 is eliminated, and the force by
which the webbing belt 28 restrains the body of the vehicle
occupant is improved. Even if the vehicle occupant thereafter
carries out the operation of suddenly braking the vehicle such that
a state of rapid deceleration of the vehicle arises, the webbing
belt 28 reliably holds the body of the vehicle occupant.
[0217] In this way, in the present embodiment, the pull-out
direction side end portion of the brake spring 392 is merely
disposed in the hole portion 394 which is formed in the leg plate
16. However, the brake spring 392, by frictional resistance,
restricts rotation of the friction ring 378 which is integral with
the rotating disc 362. Thus, effects which are similar to those of
the braking mechanism 60 of the previously-described first
embodiment and the braking mechanism 300 of the
previously-described second embodiment can be obtained.
[0218] Moreover, in the present embodiment, in order to structure
the braking mechanism, members other than the brake spring 392,
e.g., the arm 308, the lever 320, and the like, are not needed.
Therefore, the webbing retractor 390 can be realized at a low cost,
and can be made more compact and lighter weight.
[0219] As described above, in accordance with the present
invention, at the time of driving of a driving mechanism, a braking
mechanism forcibly restricts rotation of a rotating member which
follows a prime mover rotating body, and relative rotation is
forcibly generated between the prime mover rotating body and the
rotating member. Thus, the prime mover rotating body and a driven
shaft are reliably connected by connecting members which are
interlocked with this relative rotation. The driving force of the
driving mechanism can be reliably transmitted to a take-up shaft
and can reliably rotate the take-up shaft.
* * * * *