Image forming apparatus

Abstract

The image forming apparatus has a chassis, a feed roller rotatably supported by the chassis to convey paper in a paper supply direction with a first load, a press roller rotatably supported by the chassis to press on the feed roller with a predetermined pressing force, and feed roller bearings coupled to the chassis for rotatably supporting the feed roller. The feed roller bearing has an arc shaped feed roller support surface that supports the feed roller. The inner diameter of the feed roller support surface is substantially equal to an outer diameter of the feed roller. A paper ejection direction end of the feed roller support surface is positioned such that a moment on the paper ejection direction end generated by the pressing force of the press roller is no less than a moment on the paper ejection direction end generated by the first load of the paper.

1 . An image forming apparatus, comprising: 
 a chassis;    a feed roller rotatably supported by the chassis and configured to convey paper in a first direction with a first load;    a press roller rotatably supported by the chassis and configured to press on the feed roller with a predetermined pressing force; and    feed roller bearings coupled to the chassis for rotatably supporting the feed roller,    wherein    at least one of the feed roller bearings has a feed roller support surface that is at least partially formed into an arc shape for supporting an outer peripheral surface of the feed roller, an inner diameter of the arc-shaped portion of the feed roller support surface being substantially equal to an outer diameter of a portion of the feed roller that is supported by the feed roller support surface, and    a first direction end of the feed roller support surface is configured to be positioned such that a moment on the first direction end generated by the pressing force of the press roller is equal to or greater than a moment on the first direction end generated by the first load of the paper.    
   
   
       2 . The image forming apparatus according to  claim 1 , wherein 
 the first direction end is positioned so as to satisfy:        W×a≦P×b      where W is the first load of the paper, a is a perpendicular distance from the first side end to the first load of the paper, P is the pressing force from the press roller, and b is a perpendicular distance from the first direction end to the pressing force.    
   
   
       3 . The image forming apparatus according to  claim 1 , wherein 
 the chassis has an opening through which the feed roller is inserted, and    a width of the opening of the chassis is set to be equal to or less than a width of one of the feed roller bearings.    
   
   
       4 . The image forming apparatus according to  claim 1 , wherein 
 the arc-shaped portion of the feed roller support surface is formed on an inner side of the feed roller bearing extending along an angle range of 180° or less.    
   
   
       5 . The image forming apparatus according to  claim 1 , wherein 
 the feed roller is configured to convey paper in a second direction with a second load, and    a second direction end of the feed roller support surface is positioned above a lowest position of the feed roller support surface.    
   
   
       6 . The image forming apparatus according to  claim 5 , wherein 
 the second direction end is positioned so as to satisfy:        W′×a′≦P×b′     where W′ is the second load of the paper, a′ is a perpendicular distance from the second side end to the second load of the paper, P is the pressing force from the press roller, and b′ is a perpendicular distance from the second direction end to the pressing force.    
   
   
       7 . An image forming apparatus, comprising 
 a chassis;    a platen roller rotatably supported by the chassis;    a printer head supported by the chassis so as to pivotable toward and away from the platen roller;    a feed roller rotatably supported by the chassis and configured to convey paper in a first direction toward the platen roller with a first load;    a press roller rotatably supported by the chassis and configured to press on the feed roller with a predetermined pressing force; and    feed roller bearings coupled to the chassis for rotatably supporting the feed roller,    wherein    at least one of the feed roller bearings has a feed roller support surface that is at least partially formed into an arc shape for supporting an outer peripheral surface of the feed roller, an inner diameter of the arc-shaped portion of the feed roller support surface being substantially equal to an outer diameter of a portion of the feed roller that is supported by the feed roller support surface,    a first direction end of the feed roller support surface is configured to be positioned such that a moment on the first direction end generated by the pressing force of the press roller is equal to or greater than a moment on the first direction end generated by the first load of the paper,    the chassis has an opening through which the feed roller is inserted, and    a width of the opening of the chassis is set to be equal to or less than a width of one of the feed roller bearings, and    the arc-shaped portion of the feed roller support surface is formed on an inner side of the feed roller bearing extending along an angle range of  1800  or less.