JPH0486773A - Developing device - Google Patents

Abstract

PURPOSE:To keep the concentration of toner constant by providing a roller-like toner supply means which is brought into contact with a developer layer on a roller-like developing means, which supplies the toner to a carrier particle and which is formed of an electrical conductive member. CONSTITUTION:Developer 144 is attached on the outside circumference of a developing roller 142 and moved by the rotation of the roller 142. Then, a developer layer 144a is formed. Besides, a toner supply roller 148 is provided at the connection part of a toner hopper 147 and a casing 141. The toner concentration of the developer becomes constant when Coulomb power between toner and carrier and image-force that the toner is attracted by the supply roller 148 become equal. Therefore, when the quantity of the toner 146 attached on the carrier particle 150 is sufficient, the toner 146 is not supplied to the particle 150 on the developing roller 142. When the quantity of the toner 146 is small, the toner is supplied. Thus, the concentration of the toner is always kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a two-component developing device provided in, for example, an electrophotographic image forming apparatus.

(Prior Art) For example, an electrophotographic image forming apparatus is provided with a developing device for visualizing an electrostatic latent image formed on a photoreceptor. This developing device is classified into a two-component type and a one-component type. In the former method, toner is attached to carrier particles and transported to the outer periphery of a developing roller, which is a developing means, to form a developer layer and brought into contact with the surface of a photoreceptor, and the coulomb of the electrostatic latent image formed on the photoreceptor is The toner is separated from the carrier particles by force and attached to the latent image area. In the latter method, a developer layer is formed on the outer periphery of the developing roller using toner alone, and the toner is similarly attached to the latent image area. In any of the above cases, it is necessary to keep the toner concentration in the developer layer constant, and in the former two-component developing device, an optical toner concentration sensor or the like has conventionally been used. Further, the latter one-component type developing device is provided with means for making the thickness of the toner layer formed around the outer periphery of the developing roller constant.

(Problems to be Solved by the Invention) In the above-mentioned conventional two-component developing device, a toner concentration detection device is provided in order to keep the toner concentration constant.
There is a need for a toner supply device that can adjust the amount of toner supplied in accordance with the toner concentration detected by this detection device. Further, the toner concentration detection device is provided with an optical or magnetic sensor, and a system is required to control the toner supply device in accordance with changes in the output of this sensor. For this reason, there was a problem that the structure of the developing device became complicated and the cost increased.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a developing device that can maintain a constant toner concentration with a simple configuration.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a roller-shaped developing means on the surface of which a developer layer made of toner and carrier particles is formed, and a roller-like developer that comes into contact with the developer layer. and a roller-shaped toner supply means formed of a conductive member for supplying the toner to the carrier particles.

(Function) According to the above configuration, the toner and carrier constituting the developer are attracted to each other by Coulomb force due to frictional electrification. The toner concentration of the developer becomes constant when this Coulomb force and the mirror image force that attracts the toner to the toner supply means become equal.

When the toner is uniformly attached to the carrier, even if the developer comes into contact with the toner supply means, no force is generated to attract the toner from the toner supply means to the developer side. Conversely, in areas where there is no toner on the carrier, the carrier and the toner on the toner supply means come into contact, and the toner is attracted to the carrier by frictional charging. As a result, the toner concentration is always kept constant.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of a developing device according to the present invention, FIG. 2 is an explanatory diagram showing the overall configuration of an image forming apparatus to which this embodiment is applied, and FIG. 3 is a perspective view of the external appearance. be.

The image forming apparatus shown in FIG. 2 and FIG.
A document cover 3 whose one end is rotatably supported on the top surface and covers the top surface of the document table 2; and upper and lower paper feed cassettes which are removably loaded vertically on one side of the main body 1 and protrude from the negative side. 4
．． 5, and a tray 6 protruding from the paper discharge end of the other side of the main body 1.

Inside the main body 1, there is an exposure lamp 7 and a mirror 8,9,10 that reciprocates in the direction of arrow a along the lower surface of the document table 2.
a photoreceptor drum 13 that forms an image using the reflected light from the exposure scanning of the optical system through a variable magnification lens block 11 and a mirror 12; and an electrostatic latent image formed on the surface of the photoreceptor drum 13. A developing device 14 that attaches toner to create a visible image, and copy paper P stored in a cassette 4 or 5 in synchronization with the rotation of the photosensitive drum 13 as shown by arrow C.
is sent to the transfer charger 2° and the peeling charger 21 through the delivery roller mechanism 15 or 16 and the guide path 17 or 18, and the registration roller pair 22 and the transfer charger 20 are brought into close contact with the surface of the photoreceptor drum 13. A conveyor belt 23 is provided at the end of the conveyor belt 23 to which the toner image is transferred, and which conveys the copy paper P separated from the drum 13 by the peeling charger 21. A pair of fixing rollers 24 and a pair of discharge rollers 25 provided adjacent to the pair of fixing rollers 24 are provided, and the copy paper P is discharged onto the tray 6 via the pair of rollers 25.

Further, on the peripheral edge of the photoreceptor drum 13, a charger 26 for removing electricity is provided along the rotational direction to remove electricity from the drum 13 after transfer.
A cleaner 27 removes the toner adhering to the surface of the drum 13 after static electricity has been removed, a static elimination lamp 28 erases the residual image on the drum 13, and the surface of the photosensitive drum 13 is charged to form an electrostatic latent image during exposure. Charger 2 for imaging
9 is placed.

Furthermore, there is a cooling fan 30 in the main body 1 to prevent temperature rise, and a cooling fan 30 located at the insertion tip of the cassette 4.5.
A cassette size detector 31, 32 consisting of a plurality of microswitch groups for detecting the cassette size is provided.

Next, the structure of the developing device 14 will be explained with reference to FIG.

In the casing 141 of the developing device 14, a developing roller 142 and an agitation roller 143, which are developing means, are provided with their axial directions parallel to each other, and each is rotationally driven by a drive system (not shown). Further, the developing roller 142 and the photosensitive drum 13 are disposed close to each other so that their axial directions are parallel to each other.

Further, the casing 141 is filled with a developer 144 consisting of carrier particles and toner.

The developer 14 stirred by the stirring roller 143
4 adheres to the outer periphery of the developing roller 142 and moves as the developing roller 142 rotates in the direction indicated by arrow A, thereby forming a developer layer 144a. At this time, the thickness of the developer layer 144a is determined by the thickness of the blade 14 provided on the inner wall of the casing 141.
5, and remains approximately constant.

On the other hand, a toner hopper 147 filled with toner 146 is provided in the upper part of the casing 141, and a toner supply means that is rotationally driven in the direction of arrow B by a drive system (not shown) is provided at the connection part between the toner hopper 147 and the casing 141. A toner supply roller 148 is provided. This toner supply roller 148 faces the developing roller 142, and its axial direction is parallel to the developing roller 142. Further, the base end of a toner regulation plate 149 made of urethane or the like is fixed to the inner wall of the toner hopper 147, and the tip of the toner regulation plate 149 abuts the outer periphery of the toner supply roller 148 in the normal direction. Furthermore, predetermined voltages are applied to the developing roller 142 and the toner supply roller 148, respectively.

Next, the operation of this embodiment will be explained. As shown in FIG. 4, toner 146 constituting developer 144 is attracted to carrier particles 150 by Coulomb force due to triboelectric charging.

Developer layer 144a formed on the outer periphery of the developing roller 142
The toner 146 is separated from the carrier particles 150 by the Coulomb force of the electrostatic latent image formed on the photoreceptor drum 13 at the portion where the toner 146 is in contact with the photoreceptor drum 13 . Then, toner 146 adheres to the latent image area and is visualized.

On the other hand, on the toner supply roller 148, the toner 1 is charged to some extent due to friction with the toner regulation blade 149.
46 forms a certain amount of toner layer on its outer periphery due to the mirror image force between the roller 148 and the roller 148 .

Of the developer layer 144a in contact with the photoreceptor drum 13,
The toner 146 is separated from the carrier particles 150 at the portions in contact with the latent image portion and adheres to the photoreceptor drum 13 for development. As a result, this portion of the developer layer 144a
When the amount of toner 146 on the carrier particles 150 is small, the toner supply roller 1 rotates as the developing roller 142 rotates.
Reach 48. On the other hand, the toner 146 on the carrier particles 150 that does not come into contact with the latent image portion remains as it is on the carrier particles 150.
The toner supply roller 148 is reached in a state where the toner is attached to the toner supply roller 50 .

Toner 14 on carrier particles 150 as shown in FIG.
6 has not decreased and is attached in a negative manner, even if the developer layer 144a contacts the toner supply roller 148,
The force that attracts the toner 146 attached to the toner supply roller 148 to the developer layer 144a does not work, and toner supply is not performed. However, as shown in FIG. 5, when the amount of toner 146 on the carrier particles 150 is small, the toner 146 on the toner supply roller 148 and the carrier particles 150 of the developer layer 144a come into contact and frictional charging occurs, and the coulomb The force attracts the toner 146 to the carrier particles 150, supplying the toner 146 to the developer layer 144a.

According to this embodiment, if the amount of toner 146 adhering to the carrier particles 150 constituting the developer layer 144a is sufficient, the toner 146 is not supplied from the toner supply roller 148 to the carrier particles 150 on the developing roller 142. If the amount of toner 146 is not supplied and the amount of toner 146 is small, supply is performed, so that the toner concentration of developer layer 144a can always be kept constant.

〔Effect of the invention〕

As explained above, according to the present invention, if the amount of toner adhering to the carrier particles constituting the developer layer is sufficient, toner is not supplied from the toner supply roller;
When there is less toner, the toner is supplied to the carrier particles, so that the toner concentration can always be kept constant using a simple and inexpensive developing device.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a developing device according to the present invention, FIG. 2 is an explanatory diagram showing the overall configuration of an image forming apparatus to which this embodiment is applied, and FIG. 3 is an external perspective view, FIGS. 4 and 5 are explanatory views showing the state of adhesion of toner on carrier particles. 13...Photoreceptor 14...Developing device 142...Developing means (developing roller) 144a...Developer layer 146...Toner 148...Toner supply means (toner supply roller) 15
0...Carrier particles

Claims (1)

[Claims] A roller-shaped toner formed of a roller-shaped developing means on the surface of which a developer layer consisting of toner and carrier particles is formed, and a conductive member that contacts the developer layer and supplies the toner to the carrier particles. A developing device comprising a supply means.