A power transmission device has a back torque transmission cam that brings driving clutch plates 6 and driven clutch plates 7 into press contact with each other. This occurs by moving a second clutch member 4b when a rotational force is input to a first clutch member 4a, via the output shaft 3. A pressure member 5 is located at a non-actuation position. A back torque transmission cam can hold abutment between an interlocking member 9 and weight member 8 by moving the second clutch member 4b in a direction of being brought into proximity to the interlocking member 9.

A clutch assembly includes an output shaft extending along an axis and output teeth. A movable component is disposed adjacent to the output component. The movable component includes drive teeth and an annular engagement weight track including a groove circumscribing the axis. The movable component is movable between an engaged position, wherein the drive teeth are drivingly engaged with the output teeth, and a disengaged position, wherein the drive teeth are not engaged with the output teeth. An input component is disposed adjacent to the movable component. The input component includes engagement weight pockets. Spherical engagement weights are disposed in each engagement weight pocket. The groove has a generally uniform radial cross section across its circumference.

Provided is a centrifugal clutch having a simple configuration and configured so that a clutch capacity can be increased. A centrifugal clutch (200) includes a drive plate (210) to be directly rotatably driven by drive force of an engine. The drive plate (210) includes swing support pins (214) and protrusions (218). The swing support pin (214) is fitted in a pin slide hole (231) formed at a clutch weight (230), and swingably supports the clutch weight (230). The protrusion (218) includes a cylindrical roller, and contacts a driven portion (235) of the clutch weight (230). The pin slide hole (231) is formed in a long hole shape allowing the clutch weight (230) to displace backward in a rotary drive direction of the drive plate (210). The driven portion (235) is formed to extend inclined outward to a rear side in the rotary drive direction of the drive plate (210).

Provided is a centrifugal clutch having a simple configuration and configured so that a clutch capacity can be increased. A centrifugal clutch (200) includes a drive plate (210) to be directly rotatably driven by drive force of an engine. The drive plate (210) includes swing support pins (214) and protrusions (218). The swing support pin (214) is fitted in a pin slide hole (231) formed at a clutch weight (230), and swingably supports the clutch weight (230). The protrusion (218) includes a cylindrical roller, and contacts a driven portion (235) of the clutch weight (230). The pin slide hole (231) is formed in a long hole shape allowing the clutch weight (230) to displace backward in a rotary drive direction of the drive plate (210). The driven portion (235) is formed to extend inclined outward to a rear side in the rotary drive direction of the drive plate (210).

A clutch assembly includes an output shaft extending along an axis and output teeth. A movable component is disposed adjacent to the output component. The movable component includes drive teeth and an annular engagement weight track including a groove circumscribing the axis. The movable component is movable between an engaged position, wherein the drive teeth are drivingly engaged with the output teeth, and a disengaged position, wherein the drive teeth are not engaged with the output teeth. An input component is disposed adjacent to the movable component. The input component includes engagement weight pockets. Spherical engagement weights are disposed in each engagement weight pocket. The groove has a generally uniform radial cross section across its circumference.

An apparatus for connecting a rotational drive member to a rotational driven member brakes rotation when either the torque transmitted between the members exceeds a predetermined torque limit or the rotational speed of the drive member exceeds a predetermined rotational speed limit. The apparatus includes a torque limiter configured to actuate a braking mechanism or disconnect transmission when the torque limit is exceeded, and an over-speed governor configured to trigger the torque limiter when the rotational speed of the input element exceeds the rotational speed limit. The over-speed governor may trigger the torque limiter by reducing the torque limit of the torque limiter, or by introducing rotational drag in the apparatus to increase transmitted torque.

An apparatus for connecting a rotational drive member to a rotational driven member brakes rotation when either the torque transmitted between the members exceeds a predetermined torque limit or the rotational speed of the drive member exceeds a predetermined rotational speed limit. The apparatus includes a torque limiter configured to actuate a braking mechanism or disconnect transmission when the torque limit is exceeded, and an over-speed governor configured to trigger the torque limiter when the rotational speed of the input element exceeds the rotational speed limit. The over-speed governor may trigger the torque limiter by reducing the torque limit of the torque limiter, or by introducing rotational drag in the apparatus to increase transmitted torque.

Provided is a centrifugal clutch having a simple configuration and configured so that a clutch capacity can be increased. A centrifugal clutch (200) includes a drive plate (210) to be directly rotatably driven by drive force of an engine. The drive plate (210) includes swing support pins (214) and protrusions (218). The swing support pin (214) is fitted in a pin slide hole (231) formed at a clutch weight (230), and swingably supports the clutch weight (230). The protrusion (218) includes a cylindrical roller, and contacts a driven portion (235) of the clutch weight (230). The pin slide hole (231) is formed in a long hole shape allowing the clutch weight (230) to displace backward in a rotary drive direction of the drive plate (210). The driven portion (235) is formed to extend inclined outward to a rear side in the rotary drive direction of the drive plate (210).

Provided is a centrifugal clutch having a simple configuration and configured so that a clutch capacity can be increased. A centrifugal clutch (200) includes a drive plate (210) to be directly rotatably driven by drive force of an engine. The drive plate (210) includes swing support pins (214) and protrusions (218). The swing support pin (214) is fitted in a pin slide hole (231) formed at a clutch weight (230), and swingably supports the clutch weight (230). The protrusion (218) includes a cylindrical roller, and contacts a driven portion (235) of the clutch weight (230). The pin slide hole (231) is formed in a long hole shape allowing the clutch weight (230) to displace backward in a rotary drive direction of the drive plate (210). The driven portion (235) is formed to extend inclined outward to a rear side in the rotary drive direction of the drive plate (210).

A composite flywheel (13), comprising a primary flywheel (15) integral with an input shaft (31) and a secondary flywheel (17) coaxial with the primary flywheel (15). The secondary flywheel (17) and the primary flywheel (15) are constrained so that they can rotate freely with respect to each other. A coupling device (61) is further provided, adapted selectively to: transmit power from the input shaft (31) to the secondary flywheel (17); and disengage the secondary flywheel (17) from the input shaft (31).