JPH04211285A - Developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in electrophotographic copying machines, laser printers, etc., and more particularly to a developing device using a non-magnetic one-component developer.

0002

2. Description of the Related Art Generally, a one-component developer or a two-component developer is used as a developer for developing an electrostatic latent image formed on an image carrier. Among these, the two-component developer is composed of a toner that contributes to development and a carrier that supports the toner. In such a two-component developer, it is necessary to maintain a constant mixing ratio of toner and carrier, in other words, it is necessary to maintain a constant toner concentration, but it is extremely difficult to maintain a constant toner concentration. Have difficulty. On the other hand, since a one-component developer consists only of toner, it is effective in that it does not require such density adjustment.

Furthermore, this one-component developer is classified into a magnetic type and a non-magnetic type. A one-component magnetic developer is one in which particles of a non-magnetic developer contain a magnetic material. In a developing device using such a magnetic developer, a magnetic member having a plurality of magnetic poles is disposed inside the developing roller that supplies the developer to the image carrier, and the developer is attracted onto the developing roller by magnetic force. and is configured to transport it. However, when using a magnetic developer, the following problems arise. (2) Since the magnetic member must be incorporated into the developing roller, the developing roller becomes complicated and large, and in addition, becomes expensive. (2) Magnetic developers containing magnetic particles are more expensive than non-magnetic developers. (2) Magnetic developers contain magnetic particles that do not contribute to development, so color reproducibility is not sufficient. Therefore, it is difficult to perform color development using magnetic developers.

Therefore, in order to solve these problems, many developing devices using a one-component non-magnetic developer have been proposed. The important points are how to charge the developer to a predetermined amount of charge and to thin the developer to a predetermined thickness on the surface of the developing roll.

In many developing devices using one-component non-magnetic developer, such as US Pat. No. 4,232,628,
A thin layer of toner is pressed and formed on the surface of the developing roller using a single elastic blade that is in pressure contact with the developing roller, and this is triboelectrically charged, and this thin layer of toner is transferred to a photoreceptor on which an electrostatic latent image has been formed. A configuration is used that supplies

[0006]

[Problems to be Solved by the Invention] However, in this structure in which the elastic blade is brought into pressure contact with the developing roll, elastic fatigue and deformation occur in the blade over time.
As the number of prints reaches several thousand, a problem arises in that it becomes impossible to obtain the desired toner charge amount or thin toner layer.

The present invention was made in view of the above problems, and its purpose is to form a thin layer of toner on a developing roll without using the above-mentioned elastic blade. The object of the present invention is to provide a developing device that can maintain its performance over a long period of time.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the developing device of the present invention includes a housing containing toner, a part of the outer circumferential surface of which is in contact with the toner, and a roughening process is applied to the surface. A conveyance roller that rotates to carry out the toner from inside the housing; a doctor blade that is disposed with a predetermined gap from the conveyance roller and regulates the thickness of the toner layer adhering to the conveyance roller; a developing roller that is arranged in parallel at a predetermined interval and rotates at a different circumferential speed than the conveyance roller;
a voltage applying means for applying a DC bias voltage between the conveying roller and the developing roller, the toner conveyed by the conveying roller is attached to the image bearing member via the developing roller, and the surface of the image bearing member is The electrostatic latent image formed on the image is developed to form a visible image.

[0009]

[Operation] According to the above technical means, the toner is tribo-electrified by rotating the rough-surfaced conveying roller within the toner accumulated in the housing, and the charged toner is heated to a predetermined thickness by a doctor blade. Since there is a potential difference between the transport roller and the developing roller, the toner thin layer formed on the transport roller is attached to the developing roller at a point close to both rollers. The toner is transferred to form a thin layer of toner on the developing roller.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 schematically shows an electrophotographic copying machine to which the developing device of the present invention can be applied. Reference numeral 1 is the housing of the copying machine, which includes an image carrier (hereinafter referred to as a photosensitive drum) having a photosensitive film made of selenium on its outer peripheral surface.
2 is rotatably fixed in the center. In this device, an original placed on an original platen 3 that moves relative to a housing 1 is optically scanned by an image carrier lamp 4, and an image drawn on the original is exposed to light by a photoconductive member 5. By forming an image on the drum 2, the photosensitive drum 2
An electrostatic latent image is formed on the surface. Around the photosensitive drum 2, there is a charge removal lamp 6 that removes the electric charge on the outer circumferential surface of the photosensitive drum 2 before forming an image on the original, and a charger that uniformly charges the outer circumferential surface of the photosensitive drum 2 after the charge is removed. 7, and a toner supply device 8 that selectively supplies a developer to the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 2 to visualize the latent image according to the present invention. ing. Note that the surface potential of the photosensitive drum in this example is 600 V during image formation.

A paper feed section is provided at the lower part of the housing 1, and a paper feed cassette 11 is removably inserted into the housing 1 from one side, while the top sheet P in the paper feed cassette 11 is brought into rotational contact with the paper feed section. A paper feed roller 12 is provided to feed the paper into the housing 1. Then, the sheet P conveyed from the paper feeding section is positioned by the register roller 15 and then conveyed to the transfer section of the photosensitive drum 2. Note that reference numeral 13 is a guide for manual paper feeding.

Further, a transfer charger 16 for transferring a toner image (visible image) onto the conveyed sheet P is disposed in the transfer portion of the photosensitive drum 2, and the sheet P is transferred to the transfer charger 16. 16 and the photosensitive drum 2. The sheet P carrying the toner image is conveyed to a fixing device 20 by a conveyor belt 19. Then, the toner image on the sheet P is fixed by being pressurized and heated by a pair of heat rollers 21 constituting the fixing device 20. The sheet P with the image fixed thereon is discharged onto a tray 23 by a pair of discharge rollers 22 . Toner remaining on the photosensitive drum 2 after the transfer process can be removed by a cleaning unit 18.

Next, the toner supply device 8 of this embodiment will be explained. As shown in FIG. 2, the toner supply device 8 has a housing 30 consisting of a rear frame 24, a lower frame 26, and an upper frame 28. This housing 30 is divided into two chambers by a partition wall 37, and non-magnetic toner T is accumulated in the rear chamber. Inside the housing 30, a developing roller 32 that conveys the toner T toward the photosensitive drum 2 is disposed between the lower frame 26 and the front frame 28, and the conveying roller 3
4 is connected to the developing roller 3 while maintaining a gap of about 25 μm.
It is arranged parallel to 2.

The developing roller 32 has a metallic shaft 36 and a volume resistivity of 107 to 109 Ωc covering the shaft 36.
m conductive rubber members, which are disposed close to the photosensitive drum 2 and rotate in the opposite direction to the photosensitive drum 2. On the other hand, the conveyance roller 34 is formed of a cylindrical sleeve made of aluminum, and its outer peripheral surface is nickel plated after sandblasting. The surface roughness of the outer peripheral surface after plating is approximately 1 μm, but in order to obtain a toner layer of a constant thickness, it is preferable to maintain the surface roughness at 0.5 to 2 μm.

The doctor blade 52 is placed opposite the conveyance roller 34 with a gap of approximately 25 μm maintained therebetween. Thereby, the thickness of the toner layer on the outer circumferential surface of the transport roller 34 is controlled by the doctor blade 52. If the gap between the conveyance roller 34 and the doctor blade 52 were made wider, the density of the toner image on the sheet P would be higher, but the clarity of the toner image would be further reduced. This gap is approximately equal to the gap between the developing roller 32 and the conveying roller 34.

Furthermore, an agitator 31 for stirring the toner T is provided in a rear chamber of the housing 30 where the toner T is stored. This allows the toner T to adhere to the transport roller 34 more smoothly.

Further, the photosensitive drum 2, the developing roller 32, and the conveying roller 34 are each connected to a bias power source 51, and a developing bias potential is applied between the developing roller 32 and the photosensitive drum 2. The toner T is transported between the transport roller 3 and the transport roller 34.
4 to the developing roller 32 is given a potential difference for electrostatic attraction. Incidentally, the developing bias potential in this example is -200V DC.

In the developing device of this embodiment configured as described above, a thin toner layer is formed on the developing roller 32 in the following manner. The conveying roller 34 is the developing roller 32
The roller 32 rotates at twice the circumferential speed of the roller 32, and its roughened outer circumferential surface rubs against the toner T accumulated in the housing 30, causing the toner T to be frictionally charged. do. In this case, the toner T is charged to a positive potential. The conveyance roller 34 has a negative potential, for example -100
When V is applied, the toner T adheres to the transport roller 34 due to electrostatic attraction and moves as the roller 34 rotates. Therefore, a relative movement occurs between the toner attached to the conveyance roller 34 and other toners, so that the attached toner and the surrounding toner can be sufficiently frictionally charged.

The thin toner layer formed on the transport roller 34 is transported to an area sandwiched between the developing roller 32 and the transport roller 34. At this time, by applying a negative potential to the developing roller 32 from the conveying roller 34, the thin toner layer on the conveying roller 34 is transferred to the developing roller 32 by electrostatic attraction. Incidentally, at this time, the developing roller 32
By changing the potential difference between the developing roller 32 and the conveying roller 34, the amount of toner transferred to the developing roller 32 is increased or decreased, so that the density of the toner image transferred to the sheet P can be adjusted as desired.

The developing roller 32 rotates in the direction of the arrow and conveys the thin toner layer to a position facing the photosensitive drum 2. The photosensitive drum rotates at half the circumferential speed of the developing roller. A developing bias potential is supplied from the power source 51 to the developing roller 3.
2 and the photosensitive drum 2, toner particles adhering to the developing roller 32 fly to the photosensitive drum 2, thereby developing the latent image formed on the drum 2. Further, the charged toner T is constantly transferred from the conveying roller 34 to the developing roller 32, and the developing roller 3
Re-form a thin layer of toner on 2.

It should be noted that the present invention is not limited to this embodiment, and various modifications can be made. For example, the relationship between the circumferential speeds of the developing roller, conveying roller, and photosensitive drum may be changed depending on the difference in the amount of charge on the toner, and the potential difference applied between the developing roller and the conveying roller may also be changed depending on the required amount of toner conveying. You may change it as appropriate. The transport roller can also be made of a conductive foam material, and its surface roughness can be modified by changing the thickness of the toner thin layer.

[0022]

[Effects of the Invention] As explained above, according to the developing device of the present invention, toner can be formed into a thin layer on the developing roller without using parts that tend to deteriorate over time, such as an elastic blade. This makes it possible to maintain good development conditions over a long period of time.

Furthermore, by adjusting the potential difference applied between the developing roller and the conveying roller, the amount of toner adhering to the developing roller can be arbitrarily adjusted, making it possible to easily adjust the image density.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an embodiment of an electrophotographic copying machine to which a developing device of the present invention can be applied.

FIG. 2 is a schematic cross-sectional view showing an embodiment of a toner supply device.

[Explanation of symbols]

2 Image carrier (photosensitive drum) 30 Housing 32 Developing roller 34 Conveyance roller 52 Doctor Blade T Toner

Claims (3)

[Claims] 1. A housing that accommodates toner, a transport roller whose outer peripheral surface is partially in contact with the toner and has a roughened surface and rotates to carry out the toner from inside the housing, and the transport roller. a doctor blade disposed with a predetermined gap therebetween to regulate the thickness of the toner layer adhering to the conveyance roller; and a doctor blade disposed parallel to the conveyance roller with a predetermined interval therebetween and at a peripheral speed different from that of the conveyance roller. and a voltage applying means for applying a DC bias voltage between the conveying roller and the developing roller, and the toner conveyed by the conveying roller is attached to the image carrier via the developing roller. A developing device that develops an electrostatic latent image formed on the surface of an image carrier to form a visible image. 2. The developing device according to claim 1, further comprising a toner stirring means provided within the housing. 3. The developing device according to claim 1, wherein the developing roller comprises a metal shaft and a conductive rubber member covering the shaft.