1. Field of the Invention
The present invention relates to a method of feeding a developer to a developing zone in electrophotography. More particularly it relates to a method of feeding a developer capable of forming an image with a high density and less fog.
2. Description of the Prior Art
Magnetic brush development widely used in electrophotography is a process in which a two-component or one-component magnetic developer is electrostatically charged, the charged developer is fed onto a developer carrying member (a sleeve) provided with a magnet in its inside, and the developer is fed to a developing zone in the form of a magnetic brush. In the developing zone, an electrostatic image formed on the surface of a given photosensitive member is brushed with the magnetic brush to undergo development.
In this instance, the sleeve is provided above its surface with an ear-cutting member (an ear cutter) such as a doctor blade at a given interval. This ear cutter controls the ear length of the magnetic brush so that the developer may not be excessively fed and thus fog or density non-uniformity can be prevented from occurring.
However, the ear length of the magnetic brush is controlled only by a physical means wherein the magnetic brush is passed through the space between the ear cutter and the sleeve so that the magnetic brush is ear-cut.
Hence, in the case when the magnetic brush being ear-cut has a density or concentration unevenness of the developer, a corresponding density or concentration unevenness is necessarily brought to the magnetic brush being fed to the developing zone. For this reason, there is the problem that the image quality of an image obtained as result of development tends to become non-uniform.
In the magnetic brush being ear-cut, it is also possible that the developer is charged in an uneven state or a developer charged to a reverse polarity (the same polarity as the electrostatic image to be developed) is contained. In such instances, a problem arises in the density, image quality, etc. of the image obtained as result of development. The ear-cutting means described above can not evade such disadvantages.
Since the length of the magnetic brush is controlled only by the physical means between the ear cutter and the sleeve as stated above, there is another problem that the ear cutter must be provided in a highly precise and strict manner.
The above various problems are not limited to the magnetic brush development and are also seen in development processes in which a non-magnetic developer is used and the developer is transported only by an electrostatic force.