Image forming apparatus including main ribs respectively corresponding to sheets of plural sizes and sub-rib lower than main rib

Abstract

An image forming apparatus includes a fixing device, an ejection device and a conveyance guide. The fixing device is configured to fix a toner image onto a sheet. The ejection device is configured to eject the sheet having fixed toner image by the fixing device. The conveyance guide is configured to guide the sheet along a conveyance path from the fixing device to the ejection device. The conveyance guide is provided with a plurality of main ribs formed along a sheet conveyance direction so as to be located inwardly by a predetermined length from both side edges of sheets of a plurality of sizes in a sheet width direction intersecting with the sheet conveyance direction. The conveyance guide is provided with a sub-rib formed to be lower than the main ribs arranged at a space where the interval between the main ribs is wider than a predetermined interval.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 a fixing device configured to fix a toner image onto a sheet; 
 an ejection device configured to eject the sheet having fixed toner image by the fixing device; and 
 a conveyance guide configured to guide the sheet along a conveyance path from the fixing device to the ejection device, 
 wherein the conveyance guide is provided with a plurality of main ribs formed along a sheet conveyance direction, the plurality of main ribs including pairs of main ribs respectively corresponding to sheets of a plurality of sizes, and the pairs of main ribs being located inwardly by a predetermined length from both side edges of the respective sheets of the plurality of sizes in a sheet width direction intersecting with the sheet conveyance direction, 
 the conveyance guide is provided with at least one sub-rib, the at least one sub-rib is arranged at a space between adjacent ribs of the plurality of main ribs, the at least one sub-rib is formed to be have a lower height than the adjacent ribs of the plurality of main ribs arranged at a space where an interval between and is formed to be shorter that the adjacent ribs of the plurality of main ribs is wider than a predetermined interval along the sheet conveyance direction and to have a downstream end position at an upstream side from a downstream end of the adjacent ribs of the plurality of main ribs in the sheet conveyance direction, 
 the conveyance guide is further provided with an edge at a downstream side in the sheet conveyance direction, and 
 a main rib, which is adjacent to the at least one sub-rib, of the plurality of main ribs has a downstream end protruded at a downstream side from the edge in the sheet conveyance direction. 
 
     
     
       2. The image forming apparatus according to  claim 1 , wherein
 the pairs of main ribs are arranged symmetrically with respect to a center in the sheet width direction, 
 the at least one sub-rib includes a plurality of sub-ribs, 
 the plurality of sub-ribs are arranged symmetrically with respect to a center in the sheet width direction so as to be inclined to the outside in the sheet width direction toward a downstream side in the sheet conveyance direction. 
 
     
     
       3. The image forming apparatus according to  claim 2 , wherein
 the sub-rib is formed at an inclination angle of 45 degrees or less with respect to the sheet conveyance direction. 
 
     
     
       4. The image forming apparatus according to  claim 1 , wherein
 the conveyance guide is configured so that a plurality of the sub-ribs are provided in each of spaces between the main ribs and the plurality of sub-ribs are formed so that the closer the main ribs at both sides of these sub-ribs are to the center in the sheet width direction, the narrower the interval between the adjacent sub-ribs in the space between the main ribs is. 
 
     
     
       5. The image forming apparatus according to  claim 1 , wherein
 theeach main rib of the plurality of main ribs is formed on an inner guide plate along the conveyance path in the conveyance guide and is formed to continue to an outer guide plate formed along a duplex printing path in the conveyance guide. 
 
     
     
       6. The image forming apparatus according to  claim 1 , wherein
 the conveyance guide includes a shaft support hole rotatably supporting a conveyance roller conveying the sheet from the fixing device. 
 
     
     
       7. The image forming apparatus according to  claim 1 , wherein
 the conveyance guide is supported by an upper part of a pressuring roller housing rotatably supporting a pressuring roller in the fixing device. 
 
     
     
       8. The image forming apparatus according to  claim 1 , wherein
 the conveyance guide is supported by a fixing housing at the downstream side in the convevance direction from the fixing housing supporting a heating roller and a pressuring roller in the fixing device.    
     
     
       9. The image forming apparatus according to  claim 1 , wherein
 the conveyance guide is provided with an inner guide plate, and   the edge is positioned at a downstream end of the inner guide plate in the sheet conveyance direction.    
     
     
       10. The image forming apparatus according to  claim 1 , wherein the edge is formed to cross the sheet convevance direction.  
     
     
       11. An image forming apparatus comprising:
 a fixing device configured to fix a toner image onto a sheet;   an ejection device configured to eject the sheet having fixed toner image by the fixing device; and   a conveyance guide configured to guide the sheet along a conveyance path from the fixing device to the ejection device,   wherein the conveyance guide is provided with a plurality of main ribs formed along a sheet conveyance direction, the plurality of main ribs including pairs of main ribs respectively corresponding to sheets of a plurality of sizes, and the pairs of main ribs being located inwardly by a predetermined length from both side edges of the respective sheets of the plurality of sizes in a sheet width direction intersecting with the sheet conveyance direction,   the convevance guide is provided with at least one sub-rib, the at least one sub-rib is arranged at a space between adjacent ribs of the plurality of main ribs, the at least one sub-rib is formed to have a lower height than the adjacent ribs of the plurality of main ribs and is formed to be shorter than the adjacent ribs of the plurality of main ribs along the sheet conveyance direction and to have a downstream end position at an upstream side from a downstream end of the adjacent ribs of the plurality of main ribs in the sheet conveyance direction,   a main rib, which is adjacent to the at least one sub-rib, of the plurality of main ribs has a downstream end protruded at a downstream side from an inner guide plate or an outer guide plate of the conveyance guide in the sheet conveyance direction.