1. Field of the Invention
The present general inventive concept relates to a developing device and an image forming apparatus using a two-component developing method.
2. Description of the Related Art
In general, an auger, which is a shaft with a spiral wing, is used as a developer agitating and conveying member. However, as developing units have become smaller in recent years, the developer mixing and agitating performance has decreased. In order to solve this problem, the developer mixing and agitating performance is maintained in relation to the auger in three ways.
First, the developer mixing and agitating performance is maintained by lengthening a mixing and agitation path. In detail, the developer mixing and agitating performance is maintained by increasing a mixing and agitation space or lengthening a shaft of an auger in an axial direction.
Second, the developer mixing and agitating performance is maintained by installing a previous agitation chamber for previously agitating a developer, agitating the developer in the previous agitation chamber, and supplying the developer to a mixing and agitation path.
Third, the developer mixing and agitating performance is improved by adding a wing member, such as a paddle, to a shaft of an auger.
Most recent printers or copy machines are inexpensive and small. Many general developing systems include two augers for mixing and agitating a developer.
However, if the number of augers is increased in order to lengthen the mixing and agitation path, the number of parts, such as a housing for storing the augers, a bearing for the augers, and a sealing member, is increased, thereby increasing manufacturing costs. Also, as the number of parts is increased, the size of a developing unit is increased. When an auger path is increased by lengthening shafts of the augers in the axial direction, the size of an M/C is increased in order to cover the auger path in the axial direction, and the amount of developer is increased due to the increase in the size of the developing unit.
Also, even when the developer is supplied to the mixing and agitation path after the developer is agitated in the previous agitation chamber, a space for the previous agitation chamber is needed and parts, such as an agitating member, is additionally needed. Also, since excessive stress is applied to the developer in the previous agitation chamber, the developer deteriorates.
Also, a protruding agitating member may protrude in a spiral shape around a shaft of an auger. However, although the developer agitating performance at an early stage is good, if the protruding agitating member is used for a long time, fiber-like foreign materials may be wound around the protruding agitating member, thereby degrading the developer agitating performance. Also, when the protruding agitating member, which is easily deformed, is used, the protruding agitating member may be deformed, thereby easily coagulating the developer.
When the developer agitating performance is improved by missing some spiral blades of an auger, although costs are reduced and the developer agitating performance is improved, the developer conveying performance may be drastically reduced. Also, in this case, since an excessive amount of developer remains, a large space for the remaining developer is needed, thereby increasing the size of a device.