Patent ID: 6049690
Filing Date: 2000-04-11
Classification: G03G,H02P

Abstract:
A printing apparatus comprising:a belt conveying mechanism including a belt for conveying recording paper at a certain speed;a plurality of electrostatic recording units arranged in a direction in which said recording paper is conveyed by said belt, for forming latent images in conformity with image data through optical scanning of a plurality of rotating photosensitive drums, to develop the latent images with toner components having different colors prior to the transfer onto the recording paper lying on said belt;a plurality of drum position sensors for detecting rotational positions of said plurality of photosensitive drums; anda drum phase correction unit for correcting rotational phases of said photosensitive drums to predetermined phases in a manner such that transfer positions on circumferential surfaces of said photosensitive drums relative to said belt have a specific relationship on said recording paper when employing, as respective references, the rotational positions detected by said plurality of drum position sensors,wherein said drum phase correction unit comprises:a resist mark transfer unit for causing said plurality of electrostatic recording units to act simultaneously on said belt, to transfer of resist marks having different colors thereonto;a phase detection unit for detecting transfer resist marks on said belt by a sensor to determine transfer intervals relative to adjacent said electrostatic recording units, thereby calculating differences in rotational phases between specific one of said photosensitive drums as a reference and the other photosensitive drums; anda phase control unit for phase controlling drum motors so that said the other photosensitive drums keep the rotational phases detected by said phase detection unit relative to the reference phase of said reference photosensitive drum.