Patent ID: 7391996

Claim:
An image forming apparatus comprising: a rotatable image bearing member for bearing an electrostatic image; development means for developing the electrostatic image at a development position using a developer, the development means including: a plurality of development devices; a rotary, which is rotatable while retaining the plurality of development devices, the rotary including a first gear portion, which receives a driving force for rotation; and driving device for selectively moving the plurality of development devices to the development position, the driving device including a second gear portion, which engages the first gear portion at a drive transmitting position to transmit the driving force to the first gear portion; and transfer device for transferring a developer image on the image bearing member to a transfer medium at a transfer position, wherein an angle θt (°) formed by a straight line connecting a rotation center of the rotary and the drive transmitting position and a tangent line at the transfer position of the image bearing member satisfies the following relationship with the premise that a pressure angle of the first gear portion and second gear portion is α(°) and the image bearing member rotating direction is positive: −α≦θ t ≦α, in which 14°≦α≦20°.