JPH07271185A - Developing device - Google Patents

Abstract

PURPOSE:To prevent a deterioration in image quality by using a specific blade. CONSTITUTION:Toner charged by the friction by a supply roller 26 is supplied to a developing roller 24 and the thickness of the toner 14 stuck to the developing roller 24 is regulated by a blade 30. The contact surface of the blade 30 with the developing roller 24 is coated with an electrically conductive member 42 having a large coefficient of friction, so that pressurizing force for pressurizing the blade 30 against the developing roller 24 can be made small and further, the charge of the overcharged toner 14 can be discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, and more particularly to a developing device for developing an electrostatic latent image formed on the surface of a photosensitive member by using, for example, a one-component developer.

[0002]

2. Description of the Related Art Referring to FIG. 8, in a conventional developing device 1, one end of a metal blade 2 is fixed to a housing 3,
The abdomen near the other end is elastically pressed against the surface of the developing roller 4 so that the thickness of the one-component developer 5 attached to the surface of the developing roller 4 is regulated.

[0003]

Since the conventional developing device 1 uses the metal blade 2, the frictional force between the blade 2 and the developer 5 decreases in a high humidity environment, and the developer layer of the developer layer is reduced. There is a problem that the thickness is uneven and the image quality is deteriorated. As one means for solving this problem, it is conceivable to increase the pressing force of the blade 2 on the developing roller 4, but if the pressing force of the blade 2 is increased,
If the developing device 1 is left unused for a long period of time, the developing roller 4 may be permanently distorted. It is also conceivable to form the blade 2 by using rubber or resin having a large friction coefficient with the developer 5 as another means, but in this case, the blade 2 is deformed and pushed during long-term use. There is a problem that the pressure is lowered and the image quality is lowered.

On the other hand, as another conventional technique, there is known a developing device in which the blade 2 is formed by using an insulating material that promotes the charging of the developer 5. In this conventional technique, excessively charged development is performed. There is a problem in that the agent 5 aggregates between the developing roller 4 and the blade 2 to impair the transport stability of the developer on the developing roller 4, thus degrading the image quality. Therefore, a main object of the present invention is to provide a developing device capable of preventing deterioration of image quality.

[0005]

SUMMARY OF THE INVENTION A first invention is to develop an electrostatic latent image formed on a surface of a photoconductor with a toner using a one-component developer, and the inside of the one-component developer. , A developer tank that stores the one-component developer to the photoconductor, a supply member that supplies the one-component developer to the developer carrier, and a one-component developer attached to the developer carrier. In a developing device, which comprises a blade that regulates the thickness of the agent,
The blade has a main body and a conductive member that is coated on the main body and has a friction coefficient with the one-component developer that is larger than the friction coefficient between the main body and the one-component developer. A developing device, which is brought into pressure contact with an agent carrier.

A second aspect of the present invention is for developing an electrostatic latent image formed on the surface of a photoreceptor with toner by a one-component developer, and a developing tank containing the one-component developer therein. And a developer carrier for supplying a one-component developer to the photoreceptor,
In a developing device, a blade having a free end, in which a blade that regulates the thickness of the one-component developer adhering to the developer carrier is provided The plate-like elastic member including the member is bent along a line extending in a direction orthogonal to the displacement direction of the developer carrier in the vicinity of the free end, and the bent corner portion is pressed against the developer carrier. The developing device is characterized.

[0007]

In the first aspect of the invention, since the conductive member having a large friction coefficient with the developer is pressed against the developer carrying member to regulate the thickness of the developer, a metal plate or the like is used as the blade body. However, the pressing force of the blade on the developer carrying member may be relatively small. Therefore, a stable image can be obtained without causing distortion of the developer carrying member or deformation of the blade. Further, since the charge of the excessively charged developer can be discharged by the conductive member, it is possible to prevent the developer from aggregating between the developer carrier and the blade and prevent the image from being disturbed.

In the second aspect of the invention, since the corners of the plate-like elastic member constituting the blade are brought into pressure contact with the developer carrying member, the abdomen of the blade is brought into pressure contact with the developer carrying member. The pressing force of the blade on the developer carrying member can be reduced as compared with the technology. Therefore, a stable image can be obtained without causing distortion of the developer carrier. Further, if a reservoir space for excessively storing the developer is formed by the plate-like elastic member, the developer carrier and the supply member, the pressure of the developer supplied between the blade and the developer carrier is kept constant. Therefore, it is possible to prevent the image from being disturbed due to the pressure fluctuation.

[0009]

According to the present invention, deterioration of image quality can be prevented. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A developing device 10 of this embodiment shown in FIG. 1 has a one-component non-magnetic developer (toner) 14 for an electrostatic latent image formed on the surface of a photosensitive drum 12 which is an electrostatic latent image carrier. Is attached to form a visible image, and includes a housing 16. However, a photosensitive plate, a photosensitive belt, or the like may be used as the electrostatic latent image carrier.

An accommodating container 18 for accommodating the toner 14 is disposed above the housing 16, and a developing tank 22 having an opening 20 on its side surface is formed inside the housing 16 and below the accommodating container 18. It A developing roller 24, which serves as a developer carrying member that contacts the photosensitive drum 12 and supplies the toner 14 to the photosensitive drum 12, is disposed in the opening 20, and the developing roller 24 contacts the developing roller 24 inside the developing tank 22. The supply roller 26 for supplying the toner 14 thereto and the toner 14 attached to the surface of the supply roller 26 in contact with the toner
A wire net 28 is provided to remove impurities. Further, a blade 30 for regulating the thickness of the toner 14 attached to the developing roller 24 is provided above the opening 20.

The developing roller 24 includes a metal shaft 32, and a conductive rubber 34 having a thickness of about 1 to 5 mm is formed on the outer peripheral surface of the metal shaft 32. As the material of the metal shaft 32, a material having as high rigidity as possible is used in order to minimize the bending due to the pressing force from the pressing device 36 described later. On the other hand, as the material of the conductive rubber 34,
Resistance value is about 10 ⁴ to 10 ⁸ Ω and hardness is 30 to 50 °
Silicon rubber, urethane rubber, EPDM, or the like of about (JIA standard) is suitable.

The blade 30 includes a main body 38 made of a highly rigid material such as glass or metal, and an elastic member 40 elastically supporting the main body 38 above the opening 20. The surface of the main body 38 facing the developing roller 24 is smoothly ground, and the ground surface is coated with a conductive member 42 such as a cationic polymer material, as can be seen from FIG. The conductive member 42 is pressed against the surface of the developing roller 24 by the elastic member 40.

The developing device 10 as described above is installed in an image forming apparatus such as a copying machine, a printer or a facsimile.
The pressing device 36 causes the developing roller 24 to be about 1 kgf to 2 kg.
It is pressed against the photosensitive drum 12 with a force of about f. Thereby, in the developing area 44, a suitable developing nip (1-2
mm) is retained. A charging device 46, a cleaning device 48, and the like are arranged around the photosensitive drum 12.

The developing device 10 can be applied to both the reversal development process in a printer or the like and the normal rotation development process in a copying machine or the like.
The reversal development process using the developing device 10 will be described. Here, a negatively charged organic photosensitive drum is used as the photosensitive drum 12, and a negatively charged non-magnetic toner containing styrene-acrylic resin as a main component is used as the toner 14.

Referring to FIG. 1, when the developing roller 24 and the supply roller 26 are rotated in the arrow direction by a motor (not shown), the toner 14 is supplied to the developing roller 24 by the supply roller 26. At this time, the toner 14 is negatively charged by the supply roller 26. Here, if a conductive roller such as a conductive urethane foam laminated on a metal shaft is used as the supply roller 26, it is possible to prevent deterioration of the charging performance of the toner 14 due to overcharge. The thickness of the toner 14 supplied to the developing roller 24 is regulated by the blade 30 to form a thin layer. Further, the electric charges of the overcharged toner 14 are discharged in the air through the conductive member 42, thereby preventing the aggregation of the toner 14 between the developing roller 24 and the blade 30. Then, the toner 14 thinned on the surface of the developing roller 24 is conveyed to the developing area 44.

On the other hand, the charging device 46 charges the surface potential of the photosensitive drum 12 to about -700V. Then, the surface of the photosensitive drum 12 is exposed by an optical writer (not shown), and an electrostatic latent image is formed on the exposed portion. This electrostatic latent image is toner-developed in the developing area 44. According to this embodiment, since the electric charge of the toner 14 that is overcharged by the conductive member 42 can be discharged, the aggregation of the toner 14 due to overcharge can be prevented and the deterioration of the image quality can be prevented.

Further, since the toner 14 is made thin by using the conductive member 42 (FIG. 2) having a large friction coefficient with the toner 14, the pressing force of the blade 30 against the developing roller 24 can be reduced. . Therefore, even when it is not used for a long period of time, the problem that the developing roller 24 is deformed by the pressing force of the blade 30 does not occur. Further, since the main body 38 of the blade 30 is formed of a high-rigidity material such as glass or metal, the contact surface of the blade 30 with the developing roller 24 can be formed smoothly, so that a good image can be obtained. You can

3 and 4 are graphs showing the relationship between the static friction coefficient and the surface roughness of the blade 30 (conductive member 42) and the image quality. From these graphs, the static friction coefficient is about 0.5 and the surface is shown. It can be seen that the best image quality is obtained when the roughness is about 5 μm. Instead of the blade 30 in the above embodiment, a blade 50 as shown in FIG. 5 may be used, for example. This blade 5
0 includes a plate-shaped elastic member 52 such as a stainless plate or a phosphor bronze plate. The tip end of the plate-like elastic member 52 is bent along a line extending in a direction (axial direction) orthogonal to the displacement direction of the developing roller 24, and the bent portion 54 and its vicinity are coated with the conductive member 42. To be done. Then, the bent portion 54 is elastically pressed against the surface of the developing roller 24.

When such a blade 50 is used, the contact area between the blade 50 and the developing roller 24 can be reduced, so that the pressing force of the blade 50 on the developing roller 24 can be reduced. The bent portion 54
The configuration in which the developing roller 24 is pressed against the developing roller 24 can be directly applied to a metal blade or the like on which the conductive member 42 is not formed.

In the developing device 56 of another embodiment shown in FIG. 6, a part of the housing 16 made of synthetic resin has an opening 20.
In, the toner is extended to the vicinity of the surface of the developing roller 24, and this extended portion is used as the blade 58. Blade 58
The surface of the developing roller 24 facing the developing roller 24 is coated with a conductive member 42.
Is pressed against the surface of. Further, in this embodiment, the metallic supply roller 26 is used, and a gap having a predetermined interval is provided between the developing roller 24 and the supply roller 26. Then, a potential gradient is applied to the developing roller 24 and the supplying roller 26 by a voltage applying unit (not shown), and thereby the toner 14 is supplied from the supplying roller 26 to the developing roller 24.

According to this embodiment, the blade 58 can be molded simultaneously with the housing 16, so that the manufacturing process can be simplified. In the developing device 60 of another embodiment shown in FIG. 7, the blade 50 shown in FIG. 5 is used, and the free end side is extended from the bent portion 54 toward the upper side of the supply roller 26 (about 10 mm), and this extension is performed. Output section 62 and developing roller 24
And the supply roller 26 form a storage space 64 for storing the toner 14 excessively. In addition, the developing roller 24
A voltage applying device 70 is connected to the via a protective resistor 66 and a developing current detecting device 68. Protection resistor 66
Is for preventing the deterioration of the image quality due to the decrease of the resistance value of the developing roller 24 under the high humidity environment, and the resistance value is set to about 10 ⁶ to 10 ⁸ Ω. The current detection device 68 detects a current that flows when the developing roller 24 rotates after the image is output. When the detected current value exceeds a certain set level, the current detection device 68 sends a signal to a control unit (not shown), and the toner 14 Notify that there is no. In response to the signal, the control unit displays on the display unit that there is no toner. The protection resistor 66 may be turned on / off according to the output of the current detection device 68.

In the operation of the developing device 60, when the developing roller 24, the supply roller 26 and the like are rotated by a motor (not shown), the toner 14 in the developing tank 22 is excessively stored in the storage space 64 by the supply roller 26. When the pressure in the reservoir space 64 exceeds a predetermined value, the toner 14 is pushed out of the reservoir space 64 into the developing tank 22, whereby the pressure in the reservoir space 64 is kept constant. Therefore, the pressure of the toner 14 between the developing roller 24 and the blade 50 can be prevented from fluctuating depending on the remaining amount of toner in the toner tank 22, and a more stable toner thin layer can be formed.

[Brief description of drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention.

FIG. 2 is an illustrative view showing a blade in the embodiment in FIG.

FIG. 3 is a graph showing a relationship between a coefficient of static friction of a blade and image quality.

FIG. 4 is a graph showing the relationship between blade surface roughness and image quality.

5 is an illustrative view showing another blade applied to the embodiment in FIG. 1; FIG.

FIG. 6 is an illustrative view showing another embodiment of the present invention.

FIG. 7 is an illustrative view showing another embodiment of the present invention.

FIG. 8 is an illustrative view showing a conventional technique.

[Explanation of symbols]

 10 ... Developing device 12 ... Photosensitive drum 14 ... One-component developer 16 ... Housing 20 ... Opening 22 ... Developing tank 24 ... Developing roller 26 ... Supply roller 28 ... Wire mesh 30, 50, 58 ... Blade 42 ... Conductive member

Claims (7)

[Claims] 1. A developer tank for developing an electrostatic latent image formed on a surface of a photoreceptor with a one-component developer, the developing tank containing the one-component developer therein, A developer carrier for supplying the one-component developer to the photoconductor, a supply member for supplying the one-component developer to the developer carrier, and a thickness of the one-component developer attached to the developer carrier. In a developing device comprising a blade for regulating the main body, the blade is coated on the main body, and the friction coefficient between the main body and the one-component developer is greater than the friction coefficient between the main body and the one-component developer. And a large conductive member, and the conductive member is pressed against the developer carrying member by the main body. 2. The developing device according to claim 1, wherein the main body includes a high-rigidity member that is urged toward the developer carrying member by an elastic member. 3. The developing device according to claim 1, wherein the main body includes a plate-shaped elastic member whose free end is biased toward the developer carrying member. 4. The developing device according to claim 1, wherein the conductive member contains a cationic polymer material. 5. A developing tank for developing an electrostatic latent image formed on a surface of a photoconductor with a one-component developer, the developing tank containing the one-component developer therein, A developer carrier for supplying the one-component developer to the photoconductor, a supply member for supplying the one-component developer to the developer carrier, and a thickness of the one-component developer attached to the developer carrier. In the developing device, the blade includes a plate-like elastic member having a free end, and the plate-like elastic member is in a direction orthogonal to the displacement direction of the developer carrier in the vicinity of the free end. A developing device, characterized in that it is bent along a line extending in the direction of, and the bent corner portion is pressed against the developer carrying member. 6. The free end of the plate-shaped elastic member extends to above the supply member, and the plate-shaped elastic member, the developer carrying member, and the supply member make the one-component developer excessive. The developing device according to claim 5, wherein a storage space for storing is formed. 7. A conductive member having a friction coefficient with the one-component developer larger than a friction coefficient between the plate-shaped elastic member and the one-component developer is coated on at least the corner portion to form the plate-shaped elastic member. The developing device according to claim 5, wherein the conductive member is pressed against the developer carrying member by a member.