Control device, image forming apparatus, image forming method, and storage medium

An image forming method for an image forming apparatus, the method comprising:

• forming toner images on a plurality of rotatable image bearers corresponding to different colors respectively with a plurality of forming devices of the image forming apparatus;
• receiving a density of a toner image formed on each of the plurality of image bearers, the density detected by a toner density sensor;
• receiving a rotation phase of each of the plurality of image bearers relative to a rotation origin of the each of the plurality of the image bearers, the rotation phase detected by a rotation-phase detector;
• determining a first density unevenness of the toner image occurring according to a rotation of a first image bearer for a first color among the plurality of image bearers, based on the rotation phase of the first image bearer relative to the rotation origin and a variation in the density of the toner image formed on the first image bearer;
• determining a second density unevenness of the toner image occurring according to a rotation of a second image bearer for a second color among the plurality of image bearers, based on the rotation phase of the second image bearer relative to the rotation origin and a variation in the density of the toner image formed on the second image bearer;
• correcting the rotation phase of the first image bearer based on the first density unevenness and a rotation speed of the first image bearer;
• correcting the rotation phase of the second image bearer based on the second density unevenness and a rotation speed of the second image bearer;
• controlling the rotation speeds of the first image bearer and the second image bearer to be a specified rotation speed;
• and
• starting detecting the rotation phase of each of the plurality of image bearers after a difference between each of the rotation speeds of the first image bearer and the second image bearer and the specified rotation speed falls within a specified range.

A non-transitory storage medium storing a plurality of instructions which, when executed by one or more processors, cause the processors to execute a method, comprising:

• forming toner images on a plurality of rotatable image bearers corresponding to different colors respectively with a plurality of forming devices of an image forming apparatus;
• receiving a density of a toner image formed on each of the plurality of image bearers, the density detected by a toner density sensor;
• receiving a rotation phase of each of the plurality of image bearers relative to a rotation origin of the each of the plurality of the image bearers, the rotation phase detected by a rotation-phase detector;
• determining a first density unevenness of the toner image occurring according to a rotation of a first image bearer for a first color among the plurality of image bearers, based on the rotation phase of the first image bearer relative to the rotation origin and a variation in the density of the toner image formed on the first image bearer;
• determining a second density unevenness of the toner image occurring according to a rotation of a second image bearer for a second color among the plurality of image bearers, based on the rotation phase of the second image bearer relative to the rotation origin and a variation in the density of the toner image formed on the second image bearer;
• correcting the rotation phase of the second image bearer based on the second density unevenness and a rotation speed of the second image bearer;
• controlling the rotation speeds of the first image bearer and the second image bearer to be a specified rotation speed;
• and
• starting detecting the rotation phase of each of the plurality of image bearers after a difference between each of the rotation speeds of the first image bearer and the second image bearer and the specified rotation speed falls within a specified range.