Image forming apparatus

An image forming apparatus comprising:

• a first photoconductor group constituted of one or more photoconductors which is/are used for forming a mono-color image;
• a second photoconductor group constituted of one or more photoconductors which is/are used for forming a full-color image with the first photoconductor group;
• a first drive section for driving the first photoconductor group to rotate the photoconductor(s) thereof;
• a second drive section for driving second photoconductor group to rotate the photoconductor(s) thereof;
• a first drive control section for controlling of the first drive section;
• and
• a second drive control section for controlling of the second drive section, wherein
• each photoconductor constituting the first and the second photoconductor groups is engaged to the corresponding drive section thereto with rotational phases being matched with one another;
• the rotational phases of the first photoconductor group and the second photoconductor group are adjusted to be matched therebetween;
• and
• the first and the second drive control sections control so that the first and the second photoconductor groups are driven simultaneously with an equal target speed during the formation of a full-color image, wherein
• an initial drive speed which is the target speed upon starting is set at a speed which is lower than a predetermined speed for image-formation, and after the speed of the first and the second photoconductor groups reaches the initial drive speed, the target speed is changed from the initial drive speed to the speed for image-formation.