Abstract: Provided is a pretensioner for a seat belt retractor. The pretensioner for a seat belt retractor of a vehicle includes a torsion bar on which a webbing is wound; a gear member connected to the torsion bar; a base member with which the gear member is meshed and through which the torsion bar passes; a cylinder having a movement guide hole formed therein to supply a gas upon rapid deceleration of the vehicle; a piston having a rack formed at a side surface thereof in a longitudinal direction to be meshed with the gear member and moved along the movement guide hole upon supply of a gas, and; a cylindrical sealing operation part integrally formed with a bottom of the piston and projecting therefrom; and a sealing part coupled to an outer periphery of the sealing operation part to seal between the piston and an inner wall of the cylinder, wherein the base member has a hooking means for hooking the piston to a rack.

Abstract: A clutch 100 of the present webbing retractor has a gear wheel 116 and spring claws 182, and has peripheral direction load receiving portions 120 at the gear wheel 116, and load from the spring claws 182 is applied along a peripheral direction via the peripheral direction load receiving portions 120. Therefore, compactness and weight reduction of the clutch 100 can be aimed for. Further, the clutch 100 has a ring 176, and the ring 176 integrally has a cover portion 178 holding respective clutch structural members at predetermined assembly positions, and the spring claws 182, and is held integrally with a rotor 124 by elastic forces of the spring claws 182. In this way, the respective clutch structural members can be temporarily held (sub-assembled) integrally.

Abstract: A seat belt retractor, which is capable of winding and unwinding a seat belt for occupant restraint by an electric motor, warns a vehicle occupant. A seat belt retractor of a seat belt apparatus to be installed in a vehicle is structured such that a motor is controlled to repeat an action of increasing and decreasing the tension acting on a seat belt a plurality of times according to a setting that the seat belt tension at the initial stage of each action overshoots a predetermined target tension, for the purpose of warning a vehicle occupant who wears the seat belt.

Abstract: A pretensioner for restraining an occupant with a seat belt by withdrawing a seat belt buckle upon occurrence of an impact on a vehicle. The pretensioner includes a wire. One end portion of the wire is connected to the seat belt buckle and the other end portion of the wire is connected to a piston. The pretensioner further includes a cylinder slidably accommodating the piston and a gas generator supplying gas into the cylinder. The pretentioner further includes a guiding member, having a bent passage portion, that bends the wire toward the direction of the cylinder. On an inner wall surface of the bent passage portion of the guiding member, convex portions are formed in a direction orthogonal to the sliding direction of the wire. The convex portions prevent the wire from being pushed in along the direction of the cylinder.

Abstract: A seat belt retractor includes a spring for rotating a reel in a belt winding direction to wind up a seat belt, and a motor for generating rotational power capable of rotating the reel in the belt winding direction to wind up the seat belt. A motor control unit controls the motor to generate the rotational power to wind up the seat belt with a desired winding force.

Abstract: A motorized retractor which includes a spool with a webbing wound therearound, a reversible motor, a forward and a reverse driving force transmission mechanisms. The forward and the reverse driving force transmission mechanisms are provided between the spool and an output shaft of the motor, respectively. The forward driving force transmission mechanism reduces forward rotation of the output shaft by a predetermined reduction ratio and transmits this rotation to the spool for rotating the spool in a winding direction. The reverse driving force transmission mechanism reduces reverse direction rotation of the output shaft by a reduction ratio which is lower than the predetermined reduction ratio of the forward driving force transmission mechanism, and transmits this rotation to the spool for rotating the spool in the winding direction. The forward and the reverse driving force transmission mechanisms both block transmission to the output shaft of rotations generated at the spool side.

Abstract: A seat belt device has a gas generator for generating a high pressure gas when the vehicle is in emergency, a cylinder for conducting the high pressure gas from the gas generator, a piston received movably within the cylinder and pressed and moved by the high pressure gas, and a drive unit for rotating a winding shaft of a seat belt retractor in a direction of removing the slack of a belt, using the movement of the piston, wherein the pretensioner is employed with the energy absorbing mechanism, for reversely rotating the winding shaft if a tension acting on the belt exceeds a predetermined value after removing the slack of the belt.

Abstract: A webbing retractor for an elongated, strip-shaped webbing belt used for application to a body of a vehicle occupant riding in a vehicle. The webbing retractor has: a frame in which a pair of leg plates, which are disposed so as to face one another, are connected by a back plate so as to be integral; a spool which is disposed between the pair of leg plates, one end of the webbing belt being anchored to the spool; a driving mechanism which is disposed between the pair of leg plates and has an output shaft and which is for rotating the spool in at least a take-up direction; and a clutch disposed between the pair of leg plates, transmitting rotation of the output shaft to the spool. Because a motor and gears can be disposed between the leg plates of the frame, the webbing retractor can be made compact.

Abstract: The invention relates to a seat belt apparatus for motor vehicles comprising a seat belt, a belt retractor and a drive, which preferably comprises an electric motor, for the retractor, wherein a unidirectionally effective blocking member is integrated into the powertrain between the drive and the retractor which, starting from a normal blocking state, amplifies the blocking effect with a force transmission starting from the belt and reverses it into a release state with a force transmission starting from the drive.

Abstract: At least one function of a seat belt retractor by is controlled by an electric motor. Torque of which is transmitted from the electric motor via a coupling to at least one component of the seat belt retractor. After the application of the seat belt with the transmitted torque, the seat belt retractor is adjusted to a starting position for adjustable functions in normal driving conditions and in dangerous driving conditions.

Abstract: A retractor of a seatbelt apparatus to be installed in a vehicle is structured such that a motor is accommodated in a hollow cylinder portion of a spool and such that the correlation among the volume V1 of the motor housing of the motor, the volume of the cylinder portion of the spool, and the storage volume within the seatbelt retractor housing is set to achieve the equation V3<V1+V2.

Abstract: A pretensioner coupling for a seat belt retractor for a motor vehicle of a type having a belt shaft and a pretensioner drive for winding the belt shaft. The pretensioner coupling having a coupling latch movably arranged between a release position and an engagement position. The coupling latch produces a load-transmitting rotational connection between the belt shaft and the pretensioner drive when in the engagement position and movable out of the engagement position and into the release position to permit relative rotation between the belt shaft and the pretensioner drive.

Abstract: An electromechanical seat belt retractor has a seat belt retractor assembly having a spool rotationally moveable about an axis of rotation for winding and unwinding a seat belt; a motor for selectively rotating the spool; a clutch including an over-clutch driven by the motor through one or more gears; the clutch being coaxially aligned with the axis of rotation of the spool and linearly spaced from the spool; and wherein upon a forward actuation of the motor a clutch plate of the clutch linearly moves to engage the spool coupling to the spool and thereafter rotating the spool about the axis to initiate a winding of the seat belt. After the clutch plate engages the spool a reversal of the motor linearly moves the clutch plate away from the spool disengaging the spool. Preferably the clutch means is a Bendix type clutch assembly. In a preferred embodiment, the clutch plate first engages an over-clutch is fixed in a locking engagement to the spool.

Abstract: A seat belt retractor device has a gas generator for generating a high pressure gas when a vehicle is in emergency; a chamber cylinder for conducting the high pressure gas from the gas generator; a piston received movably within the chamber cylinder and pressed and moved by the high pressure gas, the piston having an O ring sealed end portion engaging walls of the chamber cylinder and a rack portion extending into the chamber cylinder; and a drive unit for rotating a winding shaft or spool of a seat belt retractor in a direction of removing a slack of a belt, using the movement of the piston and driven by said rack teeth portions; a pretensioner employed with an energy absorbing mechanism, for reversely rotating the winding spool when a tension acting on the belt exceeds a predetermined value after removing the slack of the belt; and a venting mechanism having a gas passageway for exhausting the high pressure gas from a space filled with the high pressure gas to the outside of the space, the gas passageway ex

Abstract: A self stopping seat belt retractor is provided with a belt shaft for winding a seat belt thereonto and unwinding a wound seat belt therefrom and a housing rotatably supporting the belt shaft and having a locking device that includes a locking means for the belt shaft that can be controlled in a vehicle sensitive and/or belt sensitive manner into engagement with a toothed gearing system on that side of the housing. A tightening device operating on the belt shaft includes a drive wheel, which is, prior to the release of the tightening device, secured in a force-transmitting manner on the housing, is connectable upon release of the tightening device with the belt shaft, whereby the drive wheel of the tightening device is connectable via the locking device with the belt shaft for the transmission of force to the belt shaft.

Abstract: A rotary drive for a belt tensioner includes a housing, a pinion rotatably mounted therein, and at least one driving gear coupled to the pinion, the driving gear being mounted in the housing and being adapted to be driven by pressurized gas introduced into a pressure chamber. Formed in the driving gear is a cavity having a substantially radially extending wall which, in the installed state, is opposite to a protrusion which projects into the cavity and is rigidly connected to the housing, the wall of the cavity and the protrusion forming part of a wall of the pressure chamber.

Abstract: In the webbing retractor, a lock plate is supported by a circular axis so as to be circularly movable freely by a resin support portion of a gear case by insertion of the circular axis of the lock plate in a support hole of the gear case. Even at times when great load acts on the lock plate at the support portion side, deformation of the support portion caused by movement towards the support portion side of the lock plate is prevented due to the tip of the circular axis of the lock plate contacting the metal blocking portion of the cover plate. Due to this, release of the support of the lock plate by the support portion is prevented.

Abstract: A seatbelt pretensioner mechanism (10) for use with a seatbelt retractor (11). The retractor (11) has a spool (16) configured for winding a seatbelt webbing thereon. The pretensioner mechanism (10) includes a movable actuator member (22) slidably coupled to the spool (16), a stationary member (20) secured to the retractor (11), and a base member (50) slidably coupled to the actuator (22) and to the stationary member (20). Helical splines (23) extend along a portion of the spool (16), and one or more complementary pins (25) extend along a first portion of the movable member (22) for slidingly engaging the splines (23) on the spool (16). Pins (28) also extend along a second portion of the movable member (22), and complementary helical splines (29) extend along a portion of the base member (50) for slidingly engaging the pins (28) on the second portion of the movable member (22).

Abstract: Disclosed is a self-locking safety belt retractor comprising a blocking element which can be triggered in a belt band-sensitive and/or vehicle-sensitive manner and blocks the rotation of the belt shaft in the unwinding direction of the belt, and a tensioning drive which acts upon the belt shaft and rotates said belt shaft in the winding direction of the safety belt when being triggered. The inventive safety belt retractor is characterized by the fact that the tensioning drive which is provided with two parts (14, 15; 26, 32) that move relative to each other when said tensioning drive is triggered, is disposed on the belt shaft without being connected to the housing (10) of the belt retractor and rotates along with the belt shaft before being triggered. Furthermore, one part of the tensioning drive is fixed by means of the blocking element (17) as an abutment for the tensioning movement of the second part of the tensioning drive when the tensioning drive is triggered.

Abstract: A seatbelt pretensioner mechanism (10) for use with a seatbelt retractor (11). The retractor (11) has a spool (16) configured for winding a seatbelt webbing thereon. The pretensioner mechanism (10) is housed inside the retractor spool (16). The pretensioner mechanism (10) includes a movable actuator member (22) slidably coupled to the retractor spool (16), and a stationary member (20) secured to the retractor (11) along a path of slidable movement of the movable member (22). Helical splines (23) extend along a portion of the spool (16), and complementary helical splines (25) extend along a first portion of the movable member (22) for slidingly engaging the splines (23) on the spool (16). Helical splines (29) also extend along a second portion of the movable member (22), and complementary helical splines (28) extend along a portion of the stationary member (20) for slidingly engaging the splines (29) on the second portion of the movable member (22).

Abstract: A belt tensioner for a safety belt retractor has a housing, a piston which is displaceable in the housing, and teeth, which are arranged separated and spaced from the piston.

Abstract: In a webbing take-up device, when the release of a webbing belt is detected from the signal of a buckle switch, a motor starts driving, the webbing belt is taken up, and a computing circuit increases a voltage Eb in accordance with an integrated time after the signal is switched. In this state, a lock current flows due to an output shaft of the motor being stopped, and when the power to the motor is cut off by increasing the lock current, the values of voltages El and Ed respectively corresponding to the integrated time in which the lock current is powered and the integrated time in which the power to the motor is cut off are subtracted from the value of the voltage Eb, and the motor is driven until the computing result reaches a predetermined value.

Abstract: A dual spool retractor for a motor vehicle seat belt system. The dual spool retractor includes shoulder belt and lap belt spool assemblies engaging with the shoulder belt and lap belt portions of the seat belt webbing. The dual spool retractor incorporates a gas driven pretensioner system incorporating a common gas generator connection for both the shoulder belt spool assembly and the lap belt spool assembly. Both spool assemblies are caused to undergo pretensioning retraction energized by a single gas generator.

Abstract: A belt retractor for a safety belt has a brake surface (38), a blocking mechanism (18), a brake element (24) which can prevent a steering in of the blocking mechanism (18), and a magnetic actuator (28). The brake element (24) is pressed against the brake surface (38) by means of the magnetic actuator (28).

Abstract: A seat belt retractor is provided in which two winding performances are achieved while reduced power consumption of a motor and simplified control of the motor are also achieved. A clutch gear is meshed with a carrier gear by rotation of a motor in the normal direction. Accordingly, a low reduction ratio power transmission mode is set so that a seat belt is wound up at a high speed and with low torque. As slack of the seat belt is removed and the belt load increases, the clutch pawl becomes possible to be engaged with the internal gear. As the motor current increases and exceeds a preset value, the motor rotates reversely so that the clutch gear separates from the carrier gear. Therefore, a high reduction ratio power transmission mode is set so that the belt is wound up at a low speed and with high torque.

Abstract: A rotary drive device for a winding shaft of a seat belt retractor has preformed drive bodies arranged one behind the other, which are guided and can be driven in a guide path. Each drive body has engagement parts that can be brought into engagement in an essentially interlocking manner with engagement points located at the periphery of the drive wheel.

Abstract: In a webbing retractor (10), a gear case (70), which rotatably supports another end of a shaft (162) of a lock pawl (160), is fixed to a frame (12) via engaging pins (182, 184). Namely, the engaging pin (182) is fit-together with an engaging hole (186) of a leg plate (16), and the engaging pin (184) is fit-together with an engaging hole (188) at a side of a sliding locus of a rack bar (68) which side is opposite a side at which the engaging pin (182) is located, and at a position which is displaced further in a sliding direction of the rack bar (68) than the engaging pin (182). In accordance with the webbing retractor (10), even if the gear case (70) attempts to be displaced with respect to the leg plate (16), the engaging pins (182, 184) resist this, and displacement of the gear case (70) can be prevented. Namely, changes in a supporting position of a specific member, which is provided in a vicinity of a sliding locus of a sliding member of a pretensioner, can be suppressed or prevented.

Abstract: A retractor of a seatbelt apparatus to be installed in a vehicle is structured such that a Hall sensor and a magnetic disc as a mechanism configured to detect the position of a rotor in a motor are also used as mechanisms for detecting the amount of winding or unwinding a seatbelt.

Abstract: An anchorage device for a motor vehicle is provided, including a pretensioning wheel, a pulley connected to the pretensioning wheel via a torsion bar first portion, a seat belt connecting member connected to the pulley, and a locking device coupled with the pulley via a torsion bar second portion. The torsion bar first portion provides resistance to rotation of the pulley during outward locking travel of the seat belt connecting member.

Abstract: In a webbing retractor, due to operation of a pretensioner mechanism, a stopper wire is moved, and second lock pawls of a second lock base mesh-together with an inner ratchet of a lock ring. In this way, a limit load by a torsion shaft can be switched to a high load. Therefore, immediately after operation of the pretensioner mechanism, the limit load by the torsion shaft can be made to be to the high load, and the limit load can be made to be the high load at an early stage.

Abstract: A seat belt retractor includes a spool for winding a seat belt; a lock mechanism having a locking member for rotation with the spool in a normal state and for stop-rotation in a seat belt withdrawal direction in an emergency state; a torsion bar disposed between the spool and the locking member for absorbing energy of a passenger when the spool rotates in the seat belt withdrawal direction relative to the locking member in the emergency state; a stopper screwed in a shaft of the locking member to be movable in an axial direction along the shaft of the locking member when the spool rotates relative to the locking member; and an energy-absorption member disposed on one of the stopper and the locking member for deforming in a shear mode when the stopper moves in the axial direction along the shaft of the locking member.

Abstract: An in-line seat belt pretensioner is provided that includes a frame containing a first guide member and a second guide member for tensioning of seat belt webbing upon pretensioner activation. As the pretensioner is activated, the seat belt is tensioned by activation of an actuator operably coupled to the second guide. The second guide is then routed over a vertically stationary first guide that is slidably engaged within a slot within the frame, thereby contributing to reducing the load on the occupant. A low-friction material employed in the manufacture of the guide member(s), contributes to a smoother and less abrupt tensioning of the seat belt upon activation of the pretensioner.

Abstract: A belt tensioner for a safety belt comprises a housing in which a piston is displaceable, and an exit port, wherein the exit port is arranged in the wall of the housing.

Abstract: A seat belt retractor has a winding shaft to wind a seat belt. A motive spring pretensions the winding shaft in the winding direction of the seat belt. An electric motor provides a torque that can be transmitted to the motive spring to change the spring force. A switch coupling transmits the torque of the electric motor drive to the winding shaft to retract the seat belt. To transmit the torque, a drive wheel, which is rotatably mounted on a shaft non-rotatably and coaxially connected to the winding shaft and which is non-rotatably connected to an outer spring end of the motive spring by a rigid rotational connection. A first active surface of the coupling is movably mounted against a restoring force to a component that is securely connected to the rigid rotational connection and rotatable around the shaft. A second active surface of the coupling is non-rotatably connected to the shaft.

Abstract: A dual spool retractor device for seat belts in a motor vehicle including a frame, a motor, and two spools rotatably mounted to the frame. The spools are each attached to one end of a seat belt and configured to retract the belt upon rotation. The motor is mechanically coupled to both of the spools via a differential drive arrangement configured to impart rotation to both of the spools, while allowing the spools to rotate independently if one spool is stalled. The differential drive arrangement may include a differential gear set.

Abstract: A retractor includes a pretensioner whereby load limitation disturbances are minimized or eliminated to provide a synchronized and smooth transition between the different structures resisting the rotation of the spool.

Abstract: A webbing retracting device that may prevent entering of an end-lock state when a spool rotates in the pull out direction on rebound just after completion of taking up of the webbing belt. A restriction weight is provided on a V gear. The restriction weight moves in the pull out direction relative to the V gear by acceleration when the V gear is rotated in the take up direction, and furthermore, the restriction weight pivots about a support pin under centrifugal force due to rotation of the V gear and attains a contact position. In such a state, even if the inertial mass attempts to displace toward the lock activation direction, the restriction weight interferes with the inertial mass and restricts displacement of the inertial mass toward the lock activation direction.

Abstract: Vehicle seat belt apparatus includes an electric-type pretensioner that includes a motor for rotationally driving a belt reel to take up a belt. The apparatus also includes: a take-up position detection section for detecting a take-up position of the reel; a traveling condition determination section for determining that a traveling condition of the vehicle has varied to a predetermined condition; and a control section for controlling power supply to the motor, on the basis of a signal output from the determination section, to thereby control a driving amount of the motor but also for controlling the reel, in accordance with a detection signal output by the take-up position detection section, so that the reel is kept at a predetermined take-up position, to thereby hold a vehicle occupant in a seat with the belt.

Abstract: A seatbelt retractor includes a spool formed into a hollow cylindrical shape and capable of winding a seatbelt onto a spool outer periphery or unwinding the seatbelt from the spool outer periphery. The retractor includes a motor accommodated in a cylindrical space of the spool and a motor speed-reduction mechanism configured to reduce the rotational speed of the motor via a plurality of gears. A controller is provided to control the operation of the motor.

Abstract: A seat belt device is provided where a pretensioner moves a ball train to the distal end side of a ball guide pipe by means of gas discharged from a gas generating device, and the movement rotates the spool for winding the seat belt in a belt winding direction so as to eliminate slack of the seat belt, while imparting necessary tension to the seat belt by loading rotational resistance on the spool in a belt withdrawing direction with gas pressure exerted on the ball train. The ball stopper stops movement of the ball train before all the balls in the ball train are ejected from the ball guide pipe in a state where the ball train functions to rotate the spool in the belt winding direction.

Abstract: A pinion of a pretensioner is provided at a side of a torsion shaft, which side is opposite a side connected integrally to a spool via a sleeve. A base lock of a lock mechanism is connected to the pinion. Due to the lock mechanism operating, a leg plate side end portion of the torsion shaft is locked. In this way, due to operation of the pretensioner, the pinion, which is connected to a rotating portion of a sleeve, also is locked by the locking mechanism. Therefore, a piston of the pretensioner is not lowered, and internal pressure of a cylinder does not affect deformation of the torsion shaft.

Abstract: A seat belt retractor (100) having a rotationally mounted spool (120) with a seat belt windable thereon and a pretensioner (300) for winding the spool in a belt winding direction to rewind the seat belt upon the spool; the pretensioner comprising a rack and pinion mechanism (350) activated by a pyrotechnic element (400) for causing a clutch assembly (200) to change state from a disengaged mode to an engaged mode in which the clutch assembly drivingly engages the spool.

Abstract: A seat belt retractor includes a spool for winding up a seat belt; a motor for generating rotational torque to rotate the spool; and a power transmission mechanism for transmitting the rotational torque of the motor to the spool. The seat belt retractor winds the seat belt on the spool with the rotational torque of the motor. The power transmission mechanism has a low reduction ratio transmission mode in which the rotational torque of the motor is transmitted to the spool through a low reduction ratio mechanism, and a high reduction ratio transmission mode in which the rotational torque of the motor is transmitted to the spool through a high reduction ratio mechanism. The seat belt retractor further includes a power transmission mode switching mechanism for selecting between the low reduction ratio transmission mode and the high reduction ratio transmission mode.

Abstract: A motor retractor, comprising: a winding shaft which winds up a webbing for restraining a vehicle passenger; a motor which rotates the winding shaft in a webbing winding-up direction; and a control portion which, after release of the webbing wearing state of the passenger: drives the motor to cause the webbing to be wound up around the winding shaft; stops the motor when an overload on the motor is detected during the winding-up; redrives the motor after a predetermined time having elapsed after the motor is stopped due to detection of the overland, and adjusts, at the time of the redriving, a driving state of the motor according to the time of driving the motor that has elapsed before the overload detection, is provided.

Abstract: A rotary drive device for a winding shaft of a seat belt retractor has preformed drive bodies arranged one behind the other, which are guided and can be driven in a guide path. Each drive body has engagement parts that can be brought into engagement in an essentially interlocking manner with engagement points located at the periphery of the drive wheel.

Abstract: An apparatus comprises vehicle seat belt webbing (18), a cylinder (50), and a piston (60) movable in the cylinder to effect pretensioning of the seat belt webbing. The apparatus also comprises a fluid source (10) for providing fluid under pressure to move the piston (60) in the cylinder (50). The fluid source (10) comprises a propellant container (122) defining a propellant chamber (123) and a propellant (82) in the propellant chamber. The propellant (82) is ignitable to produce fluid under pressure. The propellant container (122) comprises a first portion (124) made from plastic and a second portion (126) made from metal. The metal portion (126) is secured to the plastic portion (124) to effect a hermetic seal of the propellant container (122).

Abstract: The invention relates to a drive unit for a safety belt tensioner which has a drive which can be triggered on the response of an acceleration sensor and which can be rotationally fixedly coupled to the belt winding reel. The drive is located in a drive chamber which is formed by two plates, which extend parallel to one another and which are provided with a coating material, and which has a drive band of which at least one end is fastened to a drive shaft.

Abstract: The belt retractor has a belt spool (12) mounted rotatably in a frame (10) and a drive motor (28) coupled to the belt spool (12) via a belt drive (14, 24, 22). This drive motor (28) is a brushless direct current motor with an internal rotor that has a starting torque of at least 2 Nm.

Abstract: A seat belt retractor which achieves stable performance of a pretensioner. The seat belt retractor includes a spool for winding up a belt thereon. The spool has a shaft portion, a spool gear, and a spring-biased shaft projection which are disposed to project from a face of the spool. A spool bearing (or ring-like collar) is fitted around the shaft portion of the spool. The spool bearing is made of a material having high hardness and high rigidity such as SUS or SC. By this spool bearing, the spool is prevented from being directly subjected to load, like a bearing.

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.