Lens driving device and image forming apparatus

A lens driving device, comprising:

• a plurality of lens groups;
• a plurality of lens frames configured to support the plurality of lens groups;
• a drive mechanism configured to cause the plurality of lens frames to move upon an optical axis;
• and
• a fixed member configured to support the drive mechanism,
• wherein:
• the drive mechanism is configured to include:
• a rotational cylinder configured to be capable of moving upon the optical axis while being positioned upon an interior side of the fixed member and rotating;
• a cam part configured to be placed upon an interior radial side of the fixed member;
• and
• a cam follower of the rotational cylinder, configured to fit with the cam part;
• wherein:
• the plurality of lens groups are in a collapsed state, when a photograph is not being taken, such that an interval between the plurality of lens groups is narrowed, whereas when a photograph is being taken, the plurality of lens groups is extended upon the optical axis;
• the cam part includes
• a first cam portion formed such that the rotational cylinder extends in the optical axis upon a range whereupon the rotational cylinder moves from the collapsed state to a photography state and
• a second cam portion formed such that the rotational cylinder does not move upon the optical axis upon the photography range, even if the rotational cylinder rotates;
• the first cam portion has a cam groove of a tapering cross section in a vertical direction with respect to the optical axis of the fixed cylinder;
• the second cam portion has a cam groove of a tapering cross section in a vertical direction with respect to the optical axis of the fixed cylinder and a vertical planar surface with respect to the optical axis of the fixed cylinder;
• the cam follower is further configured to protrude in a radial direction of the rotational cylinder, and to further include a conical portion and a cylindrical portion;
• the conical portion of the cam follower fits with the taper shaped cam groove of the first cam portion upon at least a portion of the range whereupon the rotational cylinder moves upon the optical axis;
• and
• the conical portion of the cam follower is distanced from the taper shaped cam groove of the second cam portion and the cylindrical portion of the cam follower fits with the planar surface of the second cam portion upon the range whereupon the rotational cylinder does not move upon the optical axis.