Control method of image forming apparatus to determine cleaning portion performance, and image forming apparatus

A control method of an image forming apparatus,

• the image forming apparatus including
• an image forming portion which includes a photoconductor that rotates, and is capable of forming a toner image on a surface of the photoconductor,
• a transfer portion which includes an intermediate transfer member that rotates, and is capable of executing primary transfer processing for transferring the toner image formed on the surface of the photoconductor onto a surface of the intermediate transfer member at a primary transfer position and secondary transfer processing for transferring the toner image formed on the surface of the intermediate transfer member onto a sheet at a secondary transfer position,
• a cleaning portion capable of executing toner recovery processing for recovering toner present at a portion of the surface of the photoconductor that has passed through the primary transfer position and toner release processing for releasing recovered toner to the surface of the photoconductor, and
• a concentration detection portion which detects a concentration of the toner image on the intermediate transfer member,
• the cleaning portion including
• a recovery member which rotates while being in contact with the surface of the photoconductor and is capable of retaining the toner, and
• a recovery voltage output portion which applies a recovery bias voltage having a polarity different from a charging polarity of the toner to the recovery member in the toner recovery processing, and applies a release bias voltage having a polarity that is the same as the charging polarity of the toner to the recovery member in the toner release processing,
• the control method comprising:
• causing, by a processor, the image forming portion to execute first image output processing for forming a first toner image on the surface of the photoconductor;
• causing, by the processor, the transfer portion to execute the primary transfer processing for the first toner image;
• acquiring, by the processor, an output image concentration that is a detection concentration of the concentration detection portion for the first toner image;
• causing, by the processor, the image forming portion to execute second image output processing for forming a second toner image that is the same as the first toner image on the surface of the photoconductor;
• causing, by the processor, the transfer portion to execute non-transfer processing in which the second toner image is not transferred onto the intermediate transfer member;
• causing, by the processor, the cleaning portion to execute the toner recovery processing when the second toner image passes through the recovery member;
• causing, by the processor, the cleaning portion to execute the toner release processing after the toner recovery processing corresponding to the second toner image is executed;
• causing, by the processor, the transfer portion to execute the primary transfer processing for release toner that has been released to the surface of the photoconductor by the toner release processing;
• acquiring, by the processor, a release toner concentration that is a detection concentration of the concentration detection portion for the release toner that has been transferred onto the surface of the intermediate transfer member;
• and
• comparing, by the processor, the output image concentration and the release toner concentration to derive an index value of toner release performance of the recovery member.