JPH0594082A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] The size and weight of the device can be reduced, and the price can be reduced. Also, it is not necessary to replenish the toner and to dispose of the collected toner. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus of the cleaning and developing simultaneous cleaning system. [Structure] The conditions for transferring the toner 28 from the developing roller 21 to the photosensitive member exposure portion 27a by bringing the developing roller 21 and the photosensitive member 27 into contact are: development potential ≧ 150 V, residual toner 34 on the photosensitive member end exposure portion 27a. Developing roller 21
The condition for shifting to is cleaning potential ≧ 300V
Further, after the exposure device is activated and the latent image is formed on the photoconductor 27 during the time when the bias is applied to the developing roller 21, the transfer charger 13 transfers the toner image on the photoconductor 27 to the transfer paper 12. Until the end, the cleaning property is remarkably improved by operating only the charging device 30 during the rotation of the photoconductor 27 and the developing roller 21 other than that.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for a non-magnetic one-component developer which develops an electrostatic latent image using a one-component developer, such as an electrophotographic copying machine and a printer.

[0002]

2. Description of the Related Art Conventionally, as in Japanese Patent Application No. 58-32429 and Japanese Patent Application No. 58-7726, there has been developed a single developing apparatus for simultaneously performing a developing process and a cleaning process. This device develops and cleans using a two-component developer having a toner and a carrier as a developer, and the developing device itself is large and heavy, and further, it requires high cost such as auto toner. There is a problem that occurs. Furthermore, if the potential difference between the unexposed portion of the photoconductor and the developing roller is increased in order to reliably collect the residual toner, the carrier has a polarity opposite to that of the toner, and the carrier from the developing roller to the photoconductor side. In addition, since the carrier has a lower resistance than the toner and a high electric field easily injects an electric charge having a polarity opposite to that of the toner to the carrier, the carrier adheres to the side of the photoconductor, degrading the photoconductor and reducing the image quality. There is also a problem such as a decrease in

Next, referring to FIG. 5, there is shown an image forming apparatus for simultaneously carrying out a developing step and a cleaning step of a photosensitive member in a non-contact manner with a developing roller by using a one-component developer described in Japanese Patent Application No. 62-203182. explain. In FIG. 5, a charging device 10 for charging the surface of the photoconductor 7 to about -900V and an exposure device (not shown) are provided around the photoconductor 7 as an image carrier in the main body of the image forming apparatus (not shown). The exposure unit 7a to which the laser beam 11 according to the image information is applied, and the developing device 4 which is a developing unit that simultaneously develops and cleans the photoconductor 7 are housed in the unit, and the toner in the housing of the developing device 4 is stored. Toner 8 which is a non-magnetic one-component developer is supplied to the developing roller 1 from the hopper 4a. The developing roller 1 is subjected to sound blasting to increase the surface strength, is electroless plated with nickel, and has a surface roughness of 0.1 to 5 μm.
It is made of aluminum sleeve of m.
They are opposed to each other at intervals of about 0 μm. Also the developing roller 1
A coating blade 5 for coating the toner and an agitating roller 2 for scraping off the old toner are slidably contacted with each other. Further, the developing roller 1 has a power source 6 of -50.
0V is applied. 12 is a transfer paper.

First, when copying is started, the photosensitive member 7 is rotated in the direction shown by the arrow S in order to copy the first sheet, and the surface of the photosensitive member 7 is evenly changed to -9 by the charging device 10.
It is charged to 00V. When it reaches the exposure portion, it is exposed according to the image information and the surface potential of the exposure portion 7a of the photoconductor 7 is about −
Reduced to 60V. After that, the developing roller 1 reaches the developing device 4, but at this time, the developing roller 1 rotates in the direction of the arrow T, and the surface of the developing roller 1 is coated with the toner 8 by sliding contact with the coating blade 5. At that time, the toner 8 is negatively charged, which has the same polarity as the photoconductor 7. A DC voltage of −500 V is applied to the developing roller 1 as a bias voltage, and the toner flies from the developing roller 1 to the exposed portion of the photoconductor 7 due to the potential difference between the developing roller 1 and the exposed portion of the photoconductor 7, and Development is performed. Then, the toner image on the photoconductor 7 is transferred by the transfer charger 13. After this, transfer paper 1
2 is discharged to the outside of the main body through a fixing device (not shown) 1
The image forming process for the first copy is completed, and the second copy is started. At this time, the toner still remains on the photoconductor 7, but when the second copy is made, the photoconductor 7 holds the residual toner 14 again by −90 by the charging device.
It is charged to 0 V and exposed by the exposure device in the same manner as the first sheet. When the photosensitive member 7 reaches the developing device 4 in such a state, the toner on the developing roller 1 flies to the photosensitive member exposed portion due to the potential difference between the developing roller 1 and the exposed portion of the photosensitive member 7, and the photosensitive member 7 is developed. Done. Even if the residual toner 14 is present in the exposed portion, the residual toner 14 is buried in the toner 8 by new development. On the other hand, at this time, due to the potential difference between the unexposed portion of the photoconductor 7 and the bias voltage of the developing roller 1, the residual toner 14 in the unexposed portion of the photoconductor 7 flies to the developing roller 1 side, and the unexposed portion of the photoconductor 7 is exposed. Residual toner 1
4 is cleaned.

[0005]

However, in the above configuration, the developing bias potential is always applied when the developing roller 1 and the photoconductor 7 are rotationally driven, and the developing roller 1 and the photoconductor 7 are about 250 μm. Since the toner 8 flies from the developing roller 1 to the exposed portion of the photoconductor 7 because they face each other at an interval, a developing potential (| developing bias potential | − | photoconductor exposed portion potential |) ≧ 500 V Body 7
In order to fly the residual toner in the unexposed area to the developing roller, effective development and cleaning cannot be obtained unless the cleaning potential (| photoconductor unexposed area potential | − | developing bias potential |) ≧ 700V is satisfied. .. When attempting to satisfy such a condition, the potential on the exposed portion of the photoconductor is -50V, so it is necessary to set the potential on the unexposed portion of the photoconductor to -1250V and the development bias potential to -550V. There is a problem that the deterioration of the photoconductor becomes remarkable and the voltage application circuit becomes large. In addition, the condition setting described in the above-mentioned conventional example, that is, the photosensitive member unexposed portion potential -900
V, development bias potential −500 V, cleaning potential (| photoconductor unexposed portion potential | − | development bias potential |)
= 400V, the residual toner on the unexposed portion of the photoconductor is insufficiently cleaned, which causes fog on the copy, deterioration of the photoconductor 7, and downsizing of the voltage application circuit.

Therefore, the present invention is to solve the above-mentioned problems. A non-magnetic one-component developer is used to bring the developing roller into contact with the photoconductor at an appropriate pressure, and the developing step and the cleaning step are simultaneously performed by the same developing roller. It is an object of the present invention to provide an image forming apparatus having a developing device for performing.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, the present invention makes a toner contact with a photoconductor and causes the toner to fly to a latent image on the photoconductor and removes residual toner from the charged surface of the photoconductor. A developing roller for flying is provided, and the developing bias device operates only when a toner image is formed on the photoconductor, and only the charging device operates when the other photoconductor and the developing roller are driven.

[0008]

According to the above means, the distance between the developing roller and the photosensitive member is such that the toner layer thickness on the developing roller is 10 to 15 μm.
As shown in FIGS. 3 and 4, at such intervals, in order to transfer the toner from the developing roller to the photosensitive member exposed portion, the developing potential (| developing bias potential | − | photosensitive member exposed portion potential |) ≧ 150 V, in order to transfer the residual toner in the unexposed portion of the photoconductor to the developing roller, the cleaning potential (| photoconductor unexposed portion potential | − | developing bias potential |)
The condition is ≧ 300V. Here, the cleaning potential ≧ 300 V is suppressed to a considerably low level because the residual toner on the photoconductor collides with the toner on the developing roller, so that the adhesive force between the residual toner and the photoconductor is reduced and cleaning is performed. This is because it has become easier. Accordingly, the potential setting condition for satisfying the development and cleaning effects at the time of development can be set to -500V for the unexposed portion of the photosensitive member and -200V for the developing bias potential because the exposed portion potential of the photosensitive member is -50V. Further, since the developing bias potential is turned off except when the toner image is formed on the photoconductor, the cleaning potential (| photoconductor unexposed portion potential | − | development bias potential |) = 500 V. The residual toner can be sufficiently cleaned.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a cross-sectional view of the image forming apparatus of this embodiment, and 27 is an electrostatic latent image carrier (hereinafter referred to as a photoconductor) that holds an electrostatic latent image, and is brought into contact with the development. Roller 21
Is provided and is rotating in the direction indicated by arrow T.
The developing roller 21 has a carbon content of 10 3 to 10
It is made of elastic material such as silicone rubber and polyurethane rubber, which has a conductivity of 9 Ωcm. The casing 24a of the developing device 24 has a volume resistance value of 10 14 Ω · cm or more.
The non-magnetic one-component toner 28 of 016 cm or less is stored,
The agitator 23 prevents the toner 28 from blocking and conveys the toner to the toner supply roller 22.
The toner supply roller 22 is made of sponge such as urethane foam resin, and the toner 2 is provided at the contact portion with the developing roller 21.
8 is attached to the developing roller 21, and is rotated in a direction indicated by an arrow U while having a relative speed difference with the developing roller 21 so as to scrape off the residual toner on the developing roller 21 after the development is completed. Reference numeral 29 is a toner layer restriction member, and in order to form a uniform thin layer of the toner 28 on the developing roller 21 and to charge the toner, a material separated from the toner 28 in the triboelectric charging order is selected. The main component is a resin material such as Teflon rubber, polyimide rubber, and polyester rubber. The toner 28 supplied to the developing roller 21 by the toner supply roller 22 regulates the amount of the toner 28 on the developing roller 21 by the toner layer thickness regulating member 29 and charges the toner 28 to the same polarity as the electrostatic latent image. .. The surface of the photoconductor 27 is about −5 around the photoconductor 27.
Charging device 30 charged to 00V, exposure device (not shown)
The developing bias applying device 26 applies the exposing portion 27a and the developing roller 21 to which the laser beam 11 according to the image information is applied.
Is in contact with the rotating shaft. 12 is a transfer paper.

First, when copying is started, the photosensitive member 27 rotates in the direction indicated by the arrow S to copy the first sheet, and the surface of the photosensitive member 27 is uniformly charged by the charging device 30.
It is charged to 500V. Next, when it reaches the exposure section 27a, it is exposed according to the image information and the surface potential of the exposure section 27a of the photoconductor 27 is reduced to about -50V. After that, although reaching the developing device 24, a DC voltage of −200 V is applied to the developing roller 21 as a bias voltage, and the toner 28 is discharged due to the potential difference between the developing roller 21 and the exposed portion 27 a of the photoconductor 27.
Is transferred from the developing roller 21 to the photoconductor exposure section, and the photoconductor 27
Development is performed. Then, the toner image on the photoconductor 27 is transferred onto the transfer paper 12 by the transfer charger 13. Then, after this, the transfer paper 12 is discharged to the outside of the main body through a fixing device (not shown), and the image forming process of the first copy is completed, and the second copy is started. At this time, the toner 28 still remains on the photoconductor 27, but the residual toner 34 is only about 10% of the toner 28 at the time of development, and even during the copying of the second sheet, the charging process and the exposure are performed. There is no adverse effect on the process. Therefore, according to the rotation of the photoconductor 27, the charging device 30 is the same as when the first copy is made.
As a result, the photoconductor 27 including the residual toner 34 is -500V.
The surface potential of the unexposed portion is reduced to −50V regardless of the presence or absence of the residual toner 34. This is because the laser light 11 fully circulates below the residual toner 34 during exposure. When the photoconductor 27 reaches the developing device 24 in such a state, the potential difference between the developing roller 21 and the exposed portion of the photoconductor 27 becomes 150 V, and the toner 28 on the developing roller 21 becomes.
Is transferred to the exposure section of the photoconductor 27 and the photoconductor 27 is developed. Even if the residual toner 34 is present in the exposed portion, the residual toner 34 is buried in the toner 28 by new development. On the other hand, at this time, the potential difference between the unexposed portion of the photoconductor 27 and the bias voltage of the developing roller 21 is 300 V, but the distance between the photoconductor 27 and the developing roller 21 is the toner layer thickness (10 to 15 μm) on the developing roller. I have no idea, and
When the residual toner 34 on the photoconductor 27 collides with the toner on the developing roller 21, the residual toner 34 and the photoconductor 2
The adhesive force with the toner 7 is reduced, cleaning is facilitated, and the residual toner 34 on the unexposed portion of the photoconductor 27 is removed by the developing roller 21.
The residual toner 34 on the unexposed portion of the photoconductor 27 is cleaned and the second copy image is not fogged. Then, the development and 1 for the second copy
The photosensitive member 27, to which the developing device 24 has simultaneously performed cleaning for the first copy, starts the next copy again. Further, as shown in FIG. 2, in order to enhance the cleaning effect, the exposure device 24 is operated for a time to apply a bias to the developing roller 21 and the transfer charger 13 starts to form a latent image on the photoconductor 27. 12 until the transfer of the toner image on the photoconductor 27 is completed, and at the time of initialization until the temperature of the fixing device (not shown) rises to a predetermined temperature after starting the operation of the other image forming apparatus, 1 Until the data for the page is formed as a toner image on the photoconductor 27 and the data for the next page is formed as a toner image on the photoconductor 27, and
The data of the final page is formed as a toner image on the photoconductor 27, and after the transfer onto the transfer paper 12 is completed, the photoconductor 27 is finished.
At the end of printing for several rotations of the developing roller 21, the developing bias potential is turned off, and only the charging device 30 is turned on, so that the cleaning potential (| photoconductor unexposed portion potential | −
| Development bias potential |) is the limit cleaning potential (30
Since the voltage can be set to 500 V exceeding 0 V), cleaning of the residual toner on the unexposed portion of the photoconductor is further improved.

[0012]

As described above, according to the present invention, when the developing roller and the photoconductor are brought into contact with each other, the distance between them corresponds to the layer thickness (10 to 15 μm) of the toner on the developing roller.
At such intervals, in order to transfer the toner from the developing roller to the exposed portion of the photoconductor, the developing potential (| developing bias potential | − | potential of exposed portion of the photoconductor |) ≧ 150 V, the residual toner in the unexposed portion of the photoconductor is developed. In order to transfer the toner to the roller, the cleaning potential (| photoconductor unexposed portion potential | − | developing bias potential |) ≧ 300 V is satisfied, and the developing bias potential is turned off except when a toner image is formed on the photoconductor. Cleaning potential (| photoconductor unexposed area potential |-|
Development bias potential |) is set to the limit cleaning potential (300
Since the voltage can be set to 500 V which exceeds V), the cleaning effect of the residual toner on the unexposed portion of the photoreceptor is further improved. Therefore, fogging does not occur in the copy, and the deterioration of the photoconductor, the size reduction and weight reduction of the large device of the voltage application circuit, and the reduction of the price can be realized. Further, since it is not necessary to replenish the collected toner only by replenishing the toner, the maintainability is greatly improved.

[Brief description of drawings]

FIG. 1 is a side sectional view of an image forming apparatus according to an embodiment of the present invention.

[FIG. 2] Same timing chart

FIG. 3 is a graph showing developing characteristics of the developing device.

FIG. 4 is a graph showing cleaning characteristics of the developing device.

FIG. 5 is a side sectional view of a conventional image forming apparatus.

[Explanation of symbols]

 21 developing roller 26 bias applying device (developing bias device) 27 photoconductor 28 toner (non-magnetic one-component developer) 30 charging device 34 residual toner (residual developer)

Claims (1)

[Claims] 1. A photoconductor holding a non-magnetic one-component developer,
A charging device that charges the photoconductor to the same polarity as the non-magnetic one-component developer, and a non-magnetic one-component developer that moves to the exposed portion of the photoconductor and a residual developer on the unexposed portion of the photoconductor. A developing roller for collecting and a developing bias device for applying a voltage having the same polarity as that of the non-magnetic one-component developer to the developing roller are provided, and the developing bias device operates only when forming a developer image on the photoconductor. However, the image forming apparatus is characterized in that only the charging device operates when the photosensitive member and the developing roller other than the above are driven.