Patent ID: 9223131
Filing Date: 2015-12-29
Classification: B41J,G02B,G03G

Abstract:
1. An image forming apparatus comprising: an optical scanning device including a rotating polygon mirror for deflecting and scanning beam light from a light source unit, a first driving motor for rotating the rotating polygon mirror, a lens for forming an image of the beam light deflected by the rotating polygon mirror on a surface to be scanned, a folding mirror for returning the beam light having passed through the lens so as to be led to an image carrying member, and a housing to which the rotating polygon mirror, the lens, and the folding mirror are fixed; and one or more second driving motors that drive an element other than the optical scanning device, wherein the housing is provided with an opening for allowing the beam light from the folding mirror to reach the surface to be scanned by passing therethrough and a plurality of support portions disposed in the vicinity of the opening to support a reflective surface of the folding mirror, the plurality of support portions have a first support portion and a second support portion for supporting both end portions of the reflective surface in a longitudinal direction and a third support portion for supporting a part of the reflective surface between the first support portion and the second support portion in the longitudinal direction, when a distance between the first support portion and the second support portion in the longitudinal direction is set to L, the third support portion is disposed at a side of the first support portion from a position of L/4 in a direction of the second support portion from the first support portion, when a natural frequency of the folding mirror when the folding mirror has been supported at an interval of the distance L is set to A1 Hz and driving frequencies of the first driving motor and the second driving motor are respectively set to B1 Hz and B2 Hz, the folding mirror and at least one second driving motor satisfy a relation of |A1−B2|<20 Hz, and when the third support portion is disposed at a side of the second support portion from the first support portion and a natural frequency of the folding mirror when the folding mirror has been supported by the first support portion, the second support portion, and the third support portion is set to A2 Hz, the folding mirror and all the second driving motors satisfy a relation of |A2−B2|≧20 Hz, and the folding mirror and the first driving motor satisfy a relation of |A2−B1|≧20 Hz.