Rotary driving device and image forming apparatus

1. A rotary driving device comprising:

a rotary shaft supported rotatably about an axis thereof on a predetermined supporting member;

a rotary load body mounted on the rotary shaft to project radially outward from the rotary shaft in such a manner that the rotary load body can rotate integrally with the rotary shaft about the axis thereof;

a driver for rotating the rotary shaft about the axis thereof;

a disk mounted on the rotary shaft coaxially therewith for integral rotation with the rotary shaft, the disk having a stationary disk element fixedly mounted on the rotary shaft and a moveable disk element slidably mounted on the rotary shaft, first and second mounting holes formed respectively in the stationary and moveable disk elements, the first and second mounting holes being aligned along a central axis set parallel to the axis of the rotary shaft;

a spherical pendulum having a diameter larger than minimum diameters of the first and second mounting holes, the pendulum being loosely fitted in the mounting holes while being sandwiched between the stationary disk element and the movable disk element, the pendulum being caused to move radially outward within the mounting holes due to a centrifugal force produced by rotary motion of the disk on the rotary shaft; and

an adjustment mechanism for adjusting a relative position relationship between a central axis position of the mounting hole and a center of gravity position of the pendulum under conditions where the disk is rotating, the adjustment mechanism including the movable disk element sliding on the rotary shaft and into contact with the pendulum through the second mounting hole and a locking member for keeping the movable disk element from moving, wherein

the adjustment mechanism adjusts the relative position relationship between the central axis position of the mounting holes and the center of gravity position of the pendulum under conditions where the pendulum is moved radially most outward in the mounting holes, and

the adjustment mechanism goes into contact with the pendulum to regulate the amount of radially outward movement of the pendulum within the mounting holes, thereby adjusting the relative position relationship between the central axis position of the mounting holes and the center of gravity position of the pendulum.

2. The rotary driving device according to claim 1 , wherein the movable disk element includes a facing surface facing the stationary disk element, an opposite surface opposite to the facing surface and a protrusion part protruding from the opposite surface in a direction in which the rotary shaft extends, the projecting part having a slot so formed as to extend in the direction in which the rotary shaft extends,

wherein the rotary shaft has a peripheral surface formed with a threaded hole corresponding to the slot, and

wherein the locking member is a screw screwed into the threaded hole through the slot.

wherein the adjustment mechanism includes a positioning disk arranged in face to face relation with the second surface and slidably and coaxially fitted on the rotary shaft and a locking member keeping the positioning disk from moving.

3. An image forming apparatus comprising:

a photosensitive drum driven to rotate about a drum axis and having a peripheral surface on which an electrostatic latent image is formed based on image information and then a toner image having the same pattern as the electrostatic latent image is formed, the photosensitive drum transferring the toner image to an image carrying medium while rotating about the drum axis; and

a rotary driving device for driving the photosensitive drum to rotate, the rotary driving device including:

a rotary shaft supported rotatably about an axis thereof on a predetermined supporting member and supporting rotatably the photosensitive drum for integrally rotation;

a driver for rotating the rotary shaft about the axis thereof;

a disk mounted on the rotary shaft coaxially therewith for integral rotation with the rotary shaft, the disk having a stationary disk element fixedly mounted on the rotary shaft, a moveable disk element slidably mounted on the rotary shaft, first and second mounting holes formed respectively in the stationary and moveable disk elements, the first and second mounting holes being aligned along a central axis set parallel to the axis of the rotary shaft;

a spherical pendulum having a diameter larger than minimum diameters of the first and second mounting holes, the pendulum being loosely fitted in the mounting holes while being sandwiched between the stationary disk element and the movable disk element, the pendulum being caused to move radially outward within the mounting hole due to a centrifugal force produced by rotary motion of the disk on the rotary shaft; and

an adjustment mechanism for adjusting a relative position relationship between a central axis position of the mounting hole and a center of gravity position of the pendulum under conditions where the disk is rotating, the adjustment mechanism including the movable disk element sliding on the rotary shaft to go into contact with the pendulum through the second mounting hole and a locking member for keeping the movable disk element from moving, wherein

the adjustment mechanism adjusts the relative position relationship between the central axis position of the mounting holes and the center of gravity position of the pendulum under conditions where the pendulum is moved radially most outward in the mounting holes, and

the adjustment mechanism contacts the pendulum to regulate the amount of radially outward movement of the pendulum within the mounting holes, thereby adjusting the relative position relationship between the central axis position of the mounting holes and the center of gravity position of the pendulum.

4. The image forming apparatus according to claim 3 , wherein the movable disk element includes a facing surface facing the stationary disk element, an opposite surface opposite to the facing surface and a protrusion part protruding from the opposite surface in a direction in which the rotary shaft extends, the projecting part having a slot so formed as to extend in the direction in which the rotary shaft extends,

wherein the rotary shaft has a peripheral surface formed with a threaded hole corresponding to the slot, and

wherein the locking member is a screw screwed into the threaded hole through the slot.