1. Field of the Invention
The present invention relates to a photosensitive drum, a process cartridge, an image forming apparatus and an image forming system. The image forming apparatus may be embodied, for example, as an electrophotographic copying machine, a laser beam printer, an LED printer, a facsimile apparatus or the like.
2. Description of the Related Art
In such an image forming apparatus, a latent image is formed by selectively exposing a photosensitive drum which has been uniformly charged, and the latent image is visualized by developing the latent image with toner as a toner image. The toner image formed on the photosensitive drum is transferred onto a recording medium, thereby performing the recording of an image.
In such an image forming apparatus, the photosensitive drum must be rotated with high accuracy in order to enhance the image quality. To this end, there has been proposed a technique in which a gear on the photosensitive drum was meshed with a gear in the image forming apparatus so that a driving force from the image forming apparatus was surely transmitted to the photosensitive drum, thereby rotating the photosensitive drum with high accuracy.
Incidentally, the inventors of this application have proposed techniques as disclosed in the following patents.
First of all, U.S. Pat. No. 4,829,335 (issued on May 9, 1989) discloses a technique in which a driving force of an image forming apparatus is transmitted to a photosensitive member by utilizing a helical gear. According to that patent, it is possible to position the photosensitive drum in a thrust direction and to rotate the photosensitive member with high accuracy.
Further, U.S. Pat. No. 5,126,800 (issued on Jun. 30, 1992) discloses a technique in which first and second drive transmitting portions are provided on an image bearing member and a third drive transmitting portion is provided on a developer carrying member so that the third drive transmitting portion can be selectively engaged by either of the first and second drive transmitting portions. According to that patent, it is possible to easily change the rotational speed of the developer carrying member, depending upon the kind of the developer used.
Both of the two above-mentioned patents teach the fact that a gear of the photosensitive member is meshed with a gear of the image forming apparatus to surely transmit a driving force of the image forming apparatus to the photosensitive member. The present invention represents further improvement such techniques.