Conveyance control of recording medium in image forming apparatus

1. An image forming apparatus, comprising:

a first feeding unit configured to feed a sheet having a first surface and a second surface on which no image has been formed;

a second feeding unit configured to feed a sheet having a first surface on which an image has been formed;

a feeding control unit configured to control the first feeding unit and the second feeding unit;

an image forming unit configured to form an image on the first surface of the sheet fed by the first feeding unit and to form an image on a second surface of the sheet fed by the second feeding unit;

a reversal unit configured to reverse a conveyance direction of a sheet that was fed by the first feeding unit and has a first surface on which an image has been formed, and to convey the sheet with the first surface on which the image has been formed to the second feeding unit;

a post-processing unit configured to apply post-processing to a sheet; and

a post-processing control unit configured to control the post-processing unit,

wherein based on a post-processing time amount notified from the post-processing control unit, the feeding control unit adjusts a feed time of a sheet fed from the first feeding unit so that the sheet fed from the first feeding unit does not contact with a sheet waiting in the second feeding unit in a state where the sheet fed from the first feeding unit cannot wait at the reversal unit, and

wherein the first feeding unit continuously feeds a plurality of sheets until a number of sheets waiting on a sub conveyance path reaches a maximum wait number, and when the number of sheets waiting on the sub conveyance path reaches the maximum wait number, the first feeding unit feeds a sheet alternatingly with the second feeding unit.

2. The image forming apparatus according to claim 1 , comprising:

a main conveyance path through which sheets fed by the first feeding unit and the second feeding unit are conveyed to the image forming unit;

a post-processing conveyance path that branches from the main conveyance path downstream of the image forming unit in a sheet conveyance direction, and through which the sheets are conveyed to the post-processing unit; and

a sub conveyance path, which is a conveyance path on which the second feeding unit is provided, the sub conveyance path branching from the main conveyance path downstream of the image forming unit in the conveyance direction, and being connected to the main conveyance path upstream of the image forming unit in the conveyance direction so that sheets are fed by the second feeding unit once again to the image forming unit,

wherein the reversal unit reverses the conveyance direction of the sheet on the sub conveyance path.

3. The image forming apparatus according to claim 2 , wherein

the post-processing unit applies post-processing to a sheet group composed of a plurality of sheets with images formed on both the first surfaces and second surfaces thereof, and

when the image forming unit forms an image on a second surface of a final sheet in a first sheet group composed of multiple sheets to which post-processing is to be applied by the post-processing unit, if a time at which a successive sheet, which has been fed from the first feeding unit after the final sheet, has a first surface on which an image has been formed, and is waiting on the sub conveyance path, is to be fed once again to the image forming unit is to be delayed according to a post-processing time amount for post-processing to be applied to the first sheet group, the feeding control unit adjusts the feed time of a new sheet to be fed from the first feeding unit based on the post-processing time amount notified from the post-processing control unit, so that the new sheet to be fed from the first feeding unit does not come into contact with the successive sheet waiting on the sub conveyance path.

4. The image forming apparatus according to claim 2 , wherein

based on the post-processing time amount notified from the post-processing control unit and on a maximum value of a number of sheets that can wait on the sub conveyance path, the feeding control unit adjusts a feed time of a sheet to be fed from the first feeding unit so that the sheet to be fed from the first feeding unit does not come into contact with a sheet waiting on the sub conveyance path.

5. The image forming apparatus according to claim 4 , wherein

the maximum value of the number of sheets that can wait on the conveyance path is determined according to a length in the conveyance direction of the sheets and a length of the conveyance path.

6. The image forming apparatus according to claim 4 , wherein

when the maximum value of the number of sheets that can wait on the sub conveyance path is zero, the feeding control unit does not allow sheets to wait on the sub conveyance path, and adjusts the feed time of the sheet to be fed from the first feeding unit based on the post-processing time amount notified from the post-processing control unit.

7. The image forming apparatus according to claim 4 , wherein

when the maximum value of the number of sheets that can wait on the sub conveyance path is one or more, the feeding control unit allows a sheet to wait on the sub conveyance path, and adjusts the feed time of a sheet to be fed from the first feeding unit based on the post-processing time amount notified from the post-processing control unit, so that the sheet to be fed from the first feeding unit does not come into contact with the sheet waiting on the sub conveyance path.

8. The image forming apparatus according to claim 1 , wherein

the feeding control unit delays the feed time of a second sheet to be fed by the second feeding unit so that an interval from a trailing edge of a first sheet with a second surface on which an image has been formed to a leading edge of the second sheet with a second surface on which an image is to be formed is an interval corresponding to the post-processing time amount, and the feeding control unit delays the feed time of a third sheet to be fed by the first feeding unit so that an interval from a trailing edge of the third sheet fed by the first feeding unit to a leading edge of the second sheet fed by the second feeding unit is a predetermined sheet interval that is set for continuous image formation.

9. The image forming apparatus according to claim 1 , wherein

the image forming unit alternatingly executes image formation on a first surface of a sheet and image formation on a second surface of another sheet.

10. The image forming apparatus according to claim 1 , wherein

the image forming unit has a fixing unit configured to fix a toner image to a sheet, and

the fixing unit and the reversal unit are driven by the same driving source, and while the fixing unit operates, the reversal unit also continues operation.