Method of regulating the thickness of a developer layer containing magnetic carrier and toner particles

#The present invention relates to a developing means to develop a latent image on an image forming member, especially, the similar member employed in electrophotography, and more specifically relates to an improved method of forming a developer layer whereby the thickness of developer being carried and transported on a developer transporting member is regulated.

#In the electrophotography in which an electrostatic latent image on an image forming member is visualized through development to obtain final image, the current developing methods are roughly categorized into two developing methods, one of which is a method of using one-component developer and the other is a method of using two-component developer comprising magnetic carrier and non-magnetic toner.

#Among the developing methods to use one-component developer, a developing method using one-component non-magnetic developer has difficulty in forming a stable and uniform developer layer, because the force to carry the developer on a developer transporting member solely comprises Coulomb force and van der Waals force derived from electrical charge the developer has. Additionally, with a developing method using one-component magnetic developer, it is difficult to obtain vividly colored toners other than black one, because the toner generally contains black colored magnetite powder as magnetic material. On the other hand, the developing method to use two-component developer has, when compared with other methods, an advantage capable of forming a stable developer layer and using vivid color toners.

#FIG. 1 is a side view of an example according to the invention.

#FIG. 2 is an enlarged fragmentary view of FIG. 1.

#FIG. 3 is a schematic diagram of FIG. 1.

#FIG. 1 illustrates one example of a developer layer thickness regulating means according to the invention.

#A resilient plate member is pressed upon the surface of a developer transporting member in such a manner that the tip of the resilient plate member faces the upstream side of the developer transporting member. Accordingly, as shown in the figure, a nonmagnetic cylinder is employed for the developer transporting member 103, and the resilient plate member 105 having a flat-shape is pressed upon the surface of the developer transporting member 103, then a wedge-shaped gap 110 is formed between the tip of the resilient plate member 105 and the point of contact where it is pressed upon. When the developer transporting member 103 is rotated toward a specific direction, developer D carried on the developer transporting member 103 with magnetic field of magnets is separated into two portions: one of which enters the wedge-shaped gap 110; other one of which fails to enter the wedge-shaped gap 110 and is sent to one side of the resilient plate member 105 opposite to the developer transporting member 103. Among these portions, only the portion of developer D which enters the wedge-shaped gap 110 is passed through between the developer transporting member 103 and the resilient plate member 105 by the frictional force exerted by the developer transporting member 105 and then is transported to the developing area. In this case, the amount of developer passing through between the developer transporting member 103 and the resilient plate member 105 is determined by the entrance height of the wedge-shaped gap 110 as well as the pressing force with which the resilient plate member 105 is pressed upon the developer transporting member 103. Naturally, this is applicable only when the conditions including the previously mentioned properties of developer, agitating method, field and force of magnets and others are kept constant.

#In other words, if the entrance of the wedge-shaped gap 110 is smaller, the amount of developer entering the wedge-shaped gap 110 is smaller, and the amount of developer passing through between the developer transporting member 103 and the resilient plate member 105 is also smaller. Additionally, if greater force is applied to press the resilient plate member 105 upon the developer transporting member 103, the amount of developer passing through becomes smaller, because greater counter force is needed to lift the resilient plate member 105 while developer passes through between the developer transporting member 103 and the resilient plate member 105.