Color image forming apparatus

A color image forming apparatus comprising:

• a plurality of photoconductors arranged in a line so that their rotary center shafts become parallel with one another and rotating in the peripheral direction, on which toner images of each color are formed respectively;
• an endless intermediate transfer member arranged in a contactable state with said photoconductors to run;
• a plurality of first bias transfer rollers which are respectively arranged in a loop of said intermediate transfer member correspondingly to each photoconductor, and bring said intermediate transfer member into pressure contact with said photoconductors thereby to transfer the toner images of each color on said photoconductors onto said intermediate transfer member;
• guide grooves into which rotary shafts of said first bias transfer rollers are fitted, which can move said first bias transfer roller to two positions comprising a contact position where said intermediate transfer member is brought into pressure contact with said photoconductors and a separation position where said intermediate transfer member is separated from said photoconductors;
• and
• a lift drive section which is provided so that it can reciprocate linearly in the arrangement direction of the plural first bias transfer rollers and which has cam noses supporting said rotary shafts of said first bias transfer rollers, and raising and letting down said first bias transfer rollers along said guide grooves thereby to move the first bias transfer roller to said contact position or said separation position.

An image forming apparatus comprising:

• a photoconductor on which a toner image is formed;
• a loop-like intermediate transfer member which is arranged in a contactable state with said photoreceptor to run;
• a first bias transfer roller which brings said intermediate transfer member into pressure contact with said photoconductor and transfers the toner image formed on said photoconductor onto said intermediate transfer member thereby to perform first bias transfer;
• and
• a separation mechanism which separates said intermediate transfer member and said photoconductor from each other immediately after first bias transfer on the last recording medium in a first print job has been completed.

A color image forming apparatus comprising:

• a plurality of photoconductors arranged in a line so that their rotary center shafts become parallel with one another and rotating in the peripheral direction, on which toner images of each color are formed respectively;
• an endless intermediate transfer member arranged in a contactable state with said photoconductors to run;
• a plurality of first bias transfer rollers which are respectively arranged in a loop of said intermediate transfer member correspondingly to each photoconductor, and bring said intermediate transfer member into pressure contact with said photoconductors thereby to transfer the toner images of each color on said photoconductors onto said intermediate transfer member;
• guide grooves into which rotary shafts of said first bias transfer rollers are fitted, which can move said first bias transfer roller to two positions comprising a contact position where said intermediate transfer member is brought into pressure contact with said photoconductors and a separation position where said intermediate transfer member is separated from said photoconductors;
• and
• a lift drive section which is provided so that it can reciprocate linearly in the arrangement direction of the plural first bias transfer rollers and which has cam noses supporting said rotary shafts of said first bias transfer rollers, and raising and letting down said first bias transfer rollers along said guide grooves thereby to move the first bias transfer roller to said contact position or said separation position
• wherein said lift drive section separates said intermediate transfer member and said photoconductor from each other immediately after first bias transfer on the last recording medium in a first print job has been completed.

An image forming method in an image forming apparatus comprising:

• a plurality of photoconductors on which a toner image is formed;
• a loop-like intermediate transfer member which is arranged in a contactable state with said photoreceptor to run;
• a plurality of first bias transfer rollers which bring said intermediate transfer member into pressure contact with said photoconductor and transfers the toner image formed on said photoconductor onto said intermediate transfer member thereby to perform first bias transfer;
• and a second bias transfer roller which transfers said toner image formed on said intermediate transfer member onto a recording medium, that is, performs second bias transfer, wherein said intermediate transfer member and said photoconductor are separated from each other after second bias transfer onto a recording medium immediately before said last recording medium has been completed and after said first bias transfer on said last recording medium has been completed, the image forming method comprising the steps of:
• separating said intermediate transfer member and said photoconductor from each other after second bias transfer onto a recording medium immediately before the last recording medium has been completed and after said first bias transfer on said last recording medium has been completed.