Clutch and motor including such clutch

A clutch comprising:

• a housing that is non-rotatably secured and has an inner circumferential surface;
• a driving-side rotator that is connected to a drive source and is rotatably received within said housing, wherein said driving-side rotator includes a first engaging portion;
• a driven-side rotator that is connected to a load and is rotatably received within said housing, wherein said driven-side rotator includes a second engaging portion, which engages said first engaging portion in a rotational direction to limit relative rotation of said driving-side rotator within a predetermined range and which has a control surface opposing said inner circumferential surface of said housing;
• and
• a clampable element that is arranged between said inner circumferential surface of said housing and said control surface and that has an outer size smaller than a distance between a circumferential center portion of said control surface and said inner circumferential surface of said housing but larger than a distance between each of opposing circumferential end portions of said control surface and said inner circumferential surface of said housing,
• said clutch being characterized in that:
• when said driving-side rotator is rotated by a rotational force transmitted from said drive source, rotation of said driving-side rotator causes said clampable element to be substantially positioned at said center portion and also to be revolved therewith, and at the same time said first engaging portion engages said second engaging portion in a rotational direction to transmit a rotational force of said driving-side rotator to said driven-side rotator;
• and
• when said driven-side rotator is rotated by a rotational force transmitted from said load, said clampable element is clamped between said control surface and said inner circumferential surface of said housing, and at the same time said driven-side rotator is allowed to rotate while generating a desired frictional force between said clampable element and said inner circumferential surface of said housing.

A motor comprising:

• a clutch including a driving-side rotator and a driven-side rotator that is engageable with said driving-side rotator, wherein rotation of said driving-side rotator is transmitted to said driven-side rotator when said driving-side rotator is rotated, and wherein said driven-side rotator is allowed to rotate while exerting a desired rotational load on said driving-side rotator when said driven-side rotator is rotated;
• a motor main body having a rotatable shaft connected to said driving-side rotator;
• an output unit including a worm shaft connected to said driven-side rotator, a worm wheel meshed with said worm shaft, and an output shaft drivably connected to said worm wheel,
• wherein a rotational force of said rotatable shaft is transmitted to said output shaft through said clutch, said worm shaft and said worm wheel, and
• transmission of a rotational force of said output shaft to said rotatable shaft is prevented at least by a meshing load between said worm wheel and said worm shaft as well as by a rotational load of said clutch.

A motor comprising:

• a clutch including a driving-side rotator and a driven-side rotator that is engageable with said driving-side rotator, wherein rotation of said driving-side rotator is transmitted to said driven-side rotator when said driving-side rotator is rotated, and wherein said driven-side rotator is allowed to rotate while exerting a desired rotational load on said driving-side rotator when said driven-side rotator is rotated;
• a motor main body having a rotatable shaft connected to said driving-side rotator;
• and
• an output unit including a worm shaft connected to said driven-side rotator and rotatably supported by bearings, a worm wheel meshed with said worm shaft, and an output shaft drivably connected to said worm wheel,
• wherein a rotational force of said rotatable shaft is transmitted to said output shaft through said clutch, said worm shaft and said worm wheel, and
• wherein transmission of a rotational force of said output shaft to said rotatable shaft is prevented at least by a meshing load between said worm wheel and said worm shaft, by a frictional load between said worm shaft and said bearings and by a rotational load of said clutch.