In an image forming apparatus using an electrophotographic printing method, image-forming is performed such that an electrostatic latent image is formed on a photoconductive drum, toner is then adhered to this latent image, thereby to form a toner image therefrom, and the toner image is transferred to a printing medium and is fixed thereto.
In promoting the speeding-up and further high image quality, the development of an image forming apparatus of a two component development has been implemented for such image forming apparatus, in which a two component developer including toner and carrier is used.
A development device equipped in the image forming apparatus of a two component development generally includes a developing tank and a toner supply device. The developing tank contains a two component developer and has a development section such as a development roller or the like. The developing tank supplies the toner included in the two component developer to the photoconductive drum. The toner supply device is used to supply the toner to the developing tank.
The toner included in the two component developer of the developing tank is consumed for forming an image as above, therefore the development device can be used for a long term by supplying the toner from the toner supply device to the developing tank according to the amount of consumption of the toner.
On the other hand, the carrier included in the two component developer in the developing tank will not be consumed for forming an image. However, the carrier deteriorates by being used, therefore after a certain period passes from the start of use, maintenance to replace the two component developer in the development tank with a new two component developer is conducted.
Additionally, the conventional image forming apparatus is designed such that the developing tank storing the two component developer can be detached singularly from the image forming apparatus, in order to increase the effectiveness of this maintenance.
In the image forming apparatus with the developing tank provided detachable, it is necessary to prevent the dirtying within the apparatus (within the image forming apparatus). The dirtying would be caused by scattering or dropping the toner from the toner supply opening section of the toner supply device or an receiving opening of the developing tank, when attaching or detaching the developing tank.
Conventionally, there have been various proposals as a technique to prevent or restrain the dirtying within the apparatus caused by the detachability of the developing tank. One of these proposals is, for example, Patent Document 1. Patent Document 1 discloses a mechanism such that an opening provided on the toner supply section of the toner supply device opens and shuts by a shutter of a sheet form, in conjunction with the attaching and detaching operation of the developing tank.
Patent Document 1: Japanese Unexamined Patent Publication, Tokukaihei, No. 8-152784 (published on Jun. 11, 1996)
However, with a door-type structure opening and shutting the opening with one side of the sheet-formed shutter as the turning shaft as in the structure disclosed in the aforementioned Patent Document 1, the toner will adhere around the opening while using the apparatus.
If the adhered toner hardens, the toner becomes sandwiched between the shutter and the wall surface where the opening is formed, and the shutter will not shut completely. In addition, even if the shutter is completely shut, there is the problem that the toner adhered on the periphery of the shutter would drop or scatter due to vibration or the like, thereby causing dirtying.