Image forming apparatus

An image forming apparatus comprising:

• a printing portion that conveys a sheet fed into a conveyance passage and that prints an image on the sheet being conveyed;
• a post-processing portion that performs post-processing on the sheet brought in from the printing portion;
• and
• a control portion,
• wherein
• the printing portion has an image forming portion that forms an image to be printed on the sheet,
• the image forming portion includes:
• an image carrying member that is rotatably supported and that has an outer circumferential surface on which an electrostatic latent image is formed;
• and
• a developing device that has a developer carrying member which rotates while carrying developer containing toner, the developing device performing a development process to form an image by supplying toner from the rotating developer carrying member to, and thereby developing, the electrostatic latent image on the image carrying member,
• when performing printing involving the post-processing for a plurality of copies in succession, the control portion stops driving the developer carrying member at an end of the development process for a preceding image to be printed on a last sheet of a preceding copy, and starts driving the developer carrying member when performing the development process for a subsequent image to be printed on a first sheet of a subsequent copy, and
• the control portion sets, as a development driving suspension period, a period from a time when driving of the developer carrier is stopped following completion of the development process for the preceding image to a time when the driving of the developer carrying member is started to perform the development process for the subsequent image, and maintains suspension of the driving of the developer carrying member during the development driving suspension period regardless of a length of the development driving suspension period, and
• when
• T0 represents a time from a start of feeding the last sheet of the preceding copy to the conveyance passage to a start of feeding the first sheet of the subsequent copy to the conveyance passage,
• te represents a time from an end of the development process for the preceding image to suspension of driving the developer carrying member,
• ts represents a time from a start of driving the developer carrying member to perform the development process for the subseguent image to a start of the development process for the subsequent image,
• S represents a linear velocity of the image carrying member
• L1 represents a length, in a conveyance direction, of the sheet conveyed along the conveyance passage, and
• L2 represents a length, in the conveyance direction, between a trailing end of the preceding sheet and a leading end of the subseguent sheet within a same copy,
• then
• a length T1 of the development driving suspension period when an image is printed on only one side of the sheet is determined by Formula (1) below, and
• a length T2 of the development driving suspension period when images are printed on both sides of the sheet is determined by Formula (2) below.
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