JPH09244495A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to improve the recovering capacity of the residual toners on a photosensitive drum by providing the developing device with a cleaning member for cleaning a residual developer and a bias impressing device for impressing a bias on this cleaning member and using a belt-like soft member for this cleaning member. SOLUTION: The photosensitive drum 10 consists of polyimide dispersed with carbon nearer the downstream side in the rotating direction than the position where the drum comes into contact with a transfer roller 18. The drum comes into contact with an endless cleaning belt 20 (cleaning member). This cleaning belt 20 is flexible and is conductive. The bias impressing device 22 is connected to the roller 21 for pressing the cleaning belt 20 to the photosensitive drum 10. The residual toners remaining on the photosensitive drum 10 without being transferred onto a recording paper 19 are recovered onto the cleaning belt 20 composed to have the much surface area at the time of development by the electric field generated by the bias to be impressed.

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 an electrophotographic recording apparatus, and more particularly, to a developing device using a non-magnetic one-component toner as a developer.

[0002]

2. Description of the Related Art Conventionally, in a developing device using a non-magnetic one-component toner as a developer, as shown in FIG. 5, an electrostatic latent image carrier (hereinafter referred to as a photosensitive drum 1) is formed according to image information. An elastic roller (hereinafter, referred to as a developing roller 2) or the like is used as a developer carrier in order to attach charged toner to the latent image and develop the latent image. Toner is attached to the surface of the developing roller 2 and is conveyed to the photosensitive drum 1. By applying a predetermined voltage (hereinafter referred to as a developing bias) to the developing roller 2, an electric field is formed between the developing roller 2 and the photosensitive drum 1, so that toner is attached to the latent image on the photosensitive drum 1. Development with toner is performed. Further, the feeding roller 3 is used to convey and attach the toner to the developing roller 2, and the feeding roller 3 rotates while contacting the developing roller 2 to attach the toner to the developing roller 2.

The photosensitive drum 1 contacts the transfer roller 4 to which a bias is applied, on the downstream side of the contact position with the developing roller 2 in the rotational direction, and the recording paper 5 as a recording medium between them.
Is passed. The toner is transferred from the photosensitive drum 1 to the recording paper 5 by the potential difference between the photosensitive drum 1 and the transfer roller 4. A roller (hereinafter referred to as a cleaning roller 6) for cleaning the photosensitive drum 1 is installed on the downstream side of the contact position between the photosensitive drum 1 and the transfer roller 5 in the rotation direction of the photosensitive drum 1. Cleaning roller 6
A bias applying device 7 is connected to the axis of.

The operation of the cleaning roller 6 will be described below by taking the case where the toner used is positively charged toner as an example.

At the time of development, the toner is adhered to the developing roller 2 by the rotation of the supply roller 3, the adhered toner is thinned by the layer regulating blade 8, and the toner is conveyed to the position where it contacts the photosensitive drum 1. The surface of the photosensitive drum 1 is uniformly charged by the corona discharger 9, and electric charges are discharged at the portion irradiated with the laser beam by the scanner unit 10 to form an electrostatic latent image on the surface of the photosensitive drum 1. . The exposed portion of the surface of the photosensitive drum 1 has a lower potential than the unexposed portion, and the potential of the developing roller 2 is
Since the potential of the exposed portion of the photosensitive drum 1 and the potential of the unexposed portion are set to be intermediate, positively charged toner is developed from the developing roller 2 to only the exposed portion of the photosensitive drum 1. Than the potential of the exposed part of the photosensitive drum 1
Since the potential of the transfer roller 4 is set low, the toner on the photosensitive drum 1 is transferred to the recording paper 5, and this toner is heated and fixed by a fixing roller (not shown).

Here, it is sufficient that all the toner on the photosensitive drum 1 is transferred to the recording paper 5, but some toner remains on the photosensitive drum 1 without being transferred. If left, the residual toner reaches the transfer roller 4 again and is transferred to the recording paper 5. Therefore, the cleaning roller 6 is provided to prevent this. Since a bias lower than the potential of the exposed portion of the photosensitive drum 1 is applied to the cleaning roller 6, the residual toner is electrostatically attached to the cleaning roller 6.

At the time of non-development, a bias higher than the surface potential of the unexposed portion of the photosensitive drum 1 is applied to the cleaning roller 6, and the toner collected by the cleaning roller 6 is discharged onto the photosensitive drum 1. Further, since the developing bias applied to the developing roller 2 is set to a potential lower than the potential of the photosensitive drum 1, the toner discharged from the cleaning roller 6 onto the photosensitive drum 1 electrostatically adheres to the developing roller 2. To be done. The toner attached to the developing roller 2 was conveyed to the supply roller 3 and reused.

As described above, when the positively charged toner is used, the property that the toner moves from the higher potential to the lower potential is utilized. When using negatively charged toner,
Since the toner moves to the higher potential, the relationship between the potential differences between the above-described members may be reversed.

[0009]

However, in the developing device adopting the above-mentioned cleaning method, the surface area of the cleaning roller is not sufficient, so that the ability of collecting the residual toner is limited and the cleaning effect is insufficient. . Therefore, the uncleaned toner remains on the photosensitive drum. This so-called cleaning residue is
Since the developing roller 2 does not have an electrostatic recovery capability during development, there is a problem in that a printing history of a so-called photosensitive drum cycle, which is periodically transferred to recording paper, occurs.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a developing device which improves the ability to collect the residual toner on the photosensitive drum.

[0011]

In order to achieve this object, a developing device according to a first aspect of the present invention comprises a developer, an electrostatic latent image carrier on which a latent image is formed according to image information, and the electrostatic latent image carrier. A developer carrier for adhering the developer to the latent image carrier, and a developer supply member for supplying the developer to the developer carrier,
In a developing device including a cleaning member that is in sliding contact with the electrostatic latent image carrier to clean residual developer, and a bias applying device that applies a bias to the cleaning member, a belt-shaped flexible member is provided on the cleaning member. Is used.

Therefore, by using the belt-shaped flexible member as the cleaning member, the surface area of the cleaning member can be sufficiently secured, and a sufficient cleaning effect can be obtained.

According to a second aspect of the present invention, the belt-shaped flexible member is made of a conductive member.
Since the charges can be easily moved, the effect that the residual toner can be more easily attached and discharged by the electric field is produced.

According to a third aspect of the present invention, in order to bring the belt-shaped flexible member into sliding contact with the electrostatic latent image carrier, the belt-shaped flexible member contacts the electrostatic latent image carrier. By providing a plurality of pressing portions to be brought into contact with each other, it is possible to secure a large contact area of the belt-shaped flexible member with the electrostatic latent image carrier, and it is possible to further improve the cleaning effect. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a laser printer will be described below with reference to the drawings. FIG.
1 is a schematic configuration diagram illustrating a laser printer using a developing device of the present embodiment. In the present embodiment, a laser printer will be described as an example. However, the same developing device as in the present embodiment can be used in other image forming apparatuses such as a copying machine and a facsimile machine.

The laser printer includes a photosensitive drum 10 as an electrostatic latent image carrier, a corona discharger 11 for charging the surface of the photosensitive drum 10 to a uniform potential, and a photosensitive drum based on image data input from the outside. And a scanner unit 12 for irradiating a laser beam. In the portion of the surface of the photosensitive drum 10 which is irradiated with the laser beam, the electric charge charged by the corona discharger 11 is discharged, and an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 10.

In the laser printer, a non-magnetic one-component positively charged toner (hereinafter simply referred to as toner) as a developer is used.
And a supply roller 14 as a developing mechanism for transporting the toner to the surface of the photosensitive drum 10
(Developer supply member) and developing roller (developer carrier) 1
5 and an agitator 16 are provided. Developing roller 1
A layer regulating blade 17 is installed around the roller 5, and serves to make the toner layer on the developing roller 15 uniform.

The toner is supplied to the supply roller 14 and the developing roller 1.
In the area where the respective surfaces of 5 are pressed against each other by friction, the electrostatic latent image formed on the photosensitive drum 10 after being positively charged by friction, further thinned by the layer regulating blade 17 and sufficiently charged It is transported and developed.

Further, the photosensitive drum 10 contacts a roller 18 for transferring a toner image (hereinafter referred to as a transfer roller) downstream of the contact position with the developing roller 15 in the rotation direction, and a bias is applied to the transfer roller 18. ing. For this reason, the photosensitive drum 10 and the transfer roller 1 are transported by a transport mechanism (not shown).
When the recording paper 19 as a recording medium is conveyed between the recording medium and the recording medium 8, the toner attached to the electrostatic latent image is transferred onto the recording paper. In a general image forming apparatus, a so-called reversal developing method is used.
The charge polarity of the photosensitive drum 10 is the same.

The photosensitive drum 10 is in contact with an endless cleaning belt 20 (cleaning member) made of polyimide in which carbon is dispersed, on the downstream side of the contact position with the transfer roller 18 in the rotation direction. The cleaning belt 20 is flexible and conductive. Further, the rotation directions of the cleaning belt 20 are set to face each other at the contact position with the photosensitive drum 10. This rotation direction can be set to the same direction at the contact position, but at this time, it is necessary to make a speed difference (peripheral speed difference) in order to make sliding contact with each other.

The cleaning belt 20 is connected to the photosensitive drum 10.
A bias applying device 22 is connected to the roller 21 to be brought into contact with. Further, the developing bias applying device 22
Is also connected to the developing roller 15 and is configured to change the developing bias during development and during non-development.
Similar to the action of the cleaning roller 6 in FIG. 5, the residual toner left on the photosensitive drum 1 without being transferred to the recording paper 19 is collected by the cleaning belt 20 during development due to the electric field generated by the applied bias. It At the time of non-development, the bias is changed and the collected toner is discharged onto the photosensitive drum 1.

The discharged toner is collected by the developing roller 15 and reused by the change of the developing bias applied to the developing roller 15.

Next, the operation of the laser printer thus constructed will be described. The toner stored in the toner tank 13 is stirred by the rotation of the agitator 16 and is conveyed to the developing roller 15 by the rotation of the supply roller 14. The conveyed toner is rubbed against the developing roller 15 rotating in the same direction as the supply roller 14 while being charged by friction, and further charged by friction with the layer regulating blade 17, and forms a uniform carrying layer. The formed toner carrying layer is conveyed to the photosensitive drum 10 which rotates in the same direction as the developing drum 15, and forms a visible image on the electrostatic latent image portion on the photosensitive drum 10.

A bias applying device 22 is attached to the developing roller 15.
Is applied, the polarity of the developing bias is the same as the charging polarity of the toner, and the voltage is such that the absolute value of the potential of the developing roller 15 is lower than the absolute value of the surface potential of the charged photosensitive drum 10. Are set so as to be higher than the absolute value of the surface potential of the portion exposed by the scanner unit 12. For example, when a positively charged toner is used, the surface potential of the charged photosensitive drum 10 is set to +700 V,
The surface potential of the portion exposed by the scanner unit 12 is set to + 200V and the developing bias is set to + 450V (FIG. 2). Therefore, the force exerted on the charged toner by the electric field generated between the developing roller 15 and the surface of the photosensitive drum 10 is
The portion exposed by the scanner unit 12 acts as an attractive force on the photosensitive drum, and the unexposed portion acts as a repulsive force on the photosensitive drum 10.

The developing roller 15 includes the developing roller 1
Since a metal shaft longer than the width of 5 is used, a stable electric field can be formed in the developing region by the output of the bias applying device 22. In particular, a strong electric field is formed at the contact portion of the developing roller 15, and the charged toner obtains a strong adhesive force on the exposed portion of the photosensitive drum 10. Therefore, the toner adhered to the exposed portion of the photosensitive drum 10 is transferred to the developing roller 15 by the developing roller 15.
A visible image is formed by the toner on the surface of the photosensitive drum 10 on the downstream side in the rotation direction from the position where the photosensitive drum 10 is pressed to 0, and the development is completed.

The developed toner is transferred to the recording paper 19 conveyed between the photosensitive drum 10 and the transfer roller 18.

When the transfer is incomplete, the untransferred toner remains on the photosensitive drum 10 as residual toner.
A bias is applied to the roller 21 by the bias applying device 22, and the voltage is applied to the photosensitive drum 1 during development.
The bias is set to 0, which is lower than the potential of the portion exposed by the scanner unit 12, for example, 0 V, and is set to the bias, which is higher than the surface potential of the unexposed portion of the photosensitive drum 10 when not developing, for example, +900 V ( (Figure 3). Therefore, the cleaning belt 20 and the photosensitive drum 1
The force exerted on the residual toner by the electric field generated between the 0 surface acts as an attractive force on the cleaning belt 20 side during development,
At the time of non-development, it acts as an attractive force on the photosensitive drum 10 side. Therefore, at the time of development, the residual toner remains on the cleaning belt 20.
The toner adhered to the cleaning belt 20 adheres to the photosensitive drum 10 again at the time of non-development.

The toner adhering to the photosensitive drum 10 from the cleaning belt 20 at the time of non-developing is conveyed to the pressing portion of the photosensitive drum 10 and the developing roller 15 by the rotation of the photosensitive drum 10. The developing bias is set to a voltage lower than the surface potential of the photosensitive drum 10 at the time of non-developing, for example, 0 V (FIG. 2). Therefore, the force exerted on the toner by the electric field generated between the photosensitive drum 10 and the surface of the developing roller 15 acts as an attractive force on the developing roller 15 side and adheres to the developing roller 15.

The toner attached to the developing roller 15 is conveyed to the supply roller 14 by the rotation of the developing roller 15,
The toner is mechanically peeled off by the supply roller 14 and conveyed to the inside of the toner tank 13 for reuse.

The above operation is performed as a consistent flow during development and non-development.

In this way, the toner cleaning operation is performed, but the cleaning belt 20
Can be configured to have a large surface area as shown in FIG. 1, so that a sufficient cleaning effect can be exhibited.

FIG. 4 is a schematic configuration diagram of a pressing portion of the cleaning belt 20 and the photosensitive drum 10 of an apparatus having two rollers 21 for bringing the cleaning belt 20 into contact with the photosensitive drum 10 as a second embodiment. However, the grounding area of the cleaning belt 20 and the photosensitive drum 10 can be made wider than in the case where there is one roller 21. Therefore, the cleaning effect of the photosensitive drum 10 can be further enhanced. The roller 21 is the third embodiment.
It corresponds to the pressing portion of.

The present invention is not limited to the above embodiment, and can be implemented in various modes without departing from the scope of the present invention. For example, the material of the cleaning belt 20 is not limited to polyimide in which carbon is dispersed as in the present embodiment, but may be formed of another belt-shaped flexible member.

Further, in the above-mentioned embodiment, the non-magnetic one-component positively charged toner is used as the developer, but it is also applicable to the development using the magnetic toner or the negatively charged toner.

[0035]

As is apparent from the above description, in the developing device according to the first aspect, since the belt-shaped flexible member is used as the cleaning member, the surface area of the cleaning member can be sufficiently secured. Thus, it is possible to provide a developing device that exhibits a sufficient cleaning effect.

In the developing device according to the second aspect of the invention, since the belt-shaped flexible member is made of a conductive member, the transfer of electric charges is facilitated, so that the residual toner is further attached and discharged by the electric field. The effect is that it can be easily performed.

According to a third aspect of the present invention, in order to make the belt-shaped flexible member slidably contact the electrostatic latent image carrying belt, the belt-shaped flexible member is attached to the electrostatic latent image carrier. By providing a plurality of pressing portions to be brought into contact with each other, it is possible to secure a large area in which the belt-shaped flexible member is in contact with the electrostatic latent image carrier, and it is possible to further improve the cleaning effect. Occurs.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a developing device according to an embodiment of the present invention.

FIG. 2 is a timing chart of a developing bias according to the embodiment of the present invention.

FIG. 3 is a timing chart of a cleaning bias according to the embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a main part of a developing device according to a second embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a conventional developing device.

[Explanation of symbols]

 10 Photosensitive Drum 14 Supply Roller 15 Developing Roller 20 Cleaning Belt 21 Roller 22 Bias Applying Device

Claims (3)

[Claims] 1. A developer, an electrostatic latent image carrier on which a latent image is formed according to image information, a developer carrier for adhering a developer to the electrostatic latent image carrier to develop the latent image, A developer supply member for supplying the developer to the developer carrier, a cleaning member for slidingly contacting the electrostatic latent image carrier to clean the residual developer, and a bias applying device for applying a bias to the cleaning member, A developing device including: a developing device, wherein a belt-shaped flexible member is used as the cleaning member. 2. The developing device according to claim 1, wherein a conductive member is used as the belt-shaped flexible member. 3. A plurality of pressing portions for bringing the belt-shaped flexible member into contact with the electrostatic latent image carrier in order to bring the belt-shaped flexible member into sliding contact with the electrostatic latent image carrier. The developing device according to claim 1, wherein the developing device is a developing device.