JP2000321868A - One-component developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge and recover reverse polarity toner in a toner layer by using an endless belt (endless member) as a toner layer thickness regulation means, increasing its contact area with a developing roller (toner carrier), and impressing a voltage to the toner layer thickness regulation means. SOLUTION: A toner layer thickness regulation belt 13 for regulating the thickness of a toner layer on a developing roller 11 is provided. In contact with a developing roller, the toner layer thickness regulation belt 13 is stretched between a drive roller 14a and a follower roller 14b. Also, power sources 15 and 16, which impress voltages for attracting reverse polarity toner on the developing roller 11 to the toner layer thickness regulation belt 13, are provided.

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 for an image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly to a developing device using a one-component developer.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic system, an electrostatic latent image formed on a photosensitive drum as an electrostatic latent image carrier is visualized as a toner image by a developing device. . As this developing device, miniaturization,
A developing device using a one-component developer has been advantageous from the viewpoint of cost reduction and high reliability.

Conventionally, various developing devices using a one-component developer (hereinafter, referred to as toner) have been proposed and put into practical use. For example, as a mechanism for applying electric charge to the toner, a doctor blade, which is a toner layer thickness regulating unit that applies a voltage, is brought into contact with a developing roller, which is a toner carrier, when the toner passes between the developing roller and the doctor blade. There was one that was configured to charge (JP-B 63-63)
No. 16736).

However, it is difficult to form a thin layer of toner on the developing roller, and only a relatively thick toner layer has been formed. In such a thin toner layer forming method, the application of charge to the toner and the uniform formation of the toner layer are determined by the contact state between the doctor blade and the developing roller, and the doctor blade and the developing roller come into contact with each other. By increasing the pressure, a thin layer of toner can be formed.

[0005] However, when the pressure at which the doctor blade and the developing roller contact each other is increased, excessive pressure is applied to the toner at the contact portion, and the toner is fused on the doctor blade and streaks are formed on the toner layer. There was a problem that it deteriorated.

Therefore, in Japanese Patent Application Laid-Open No. 2-109070, in order to give a uniform and high charge without applying excessive pressure to the toner, the contact time with the toner must be long and the pressure applied to the toner must not be too large. A configuration in which a developer is applied on a developing roller using an endless belt as a toner layer thickness regulating unit has been disclosed.

Japanese Patent Application Laid-Open No. 10-123823 discloses an image formed by applying a charge to a developer by using a rotating belt member that is in surface contact with the surface of a photosensitive drum to reduce stress applied to a toner. There is disclosed a configuration in which the quality is stabilized for a long time.

However, the charge of the toner due to the frictional charge is such that the toner having the opposite polarity to the desired polarity is mixed in the thin toner layer. The toner charged in the opposite polarity adheres to the non-image portion on the photosensitive drum, and is transferred together with a regular image at the time of transfer and appears as an image fog, thus causing a problem of deterioration in image quality.

As a method of removing the toner of the opposite polarity, Japanese Patent Application Laid-Open No. 5-61299 discloses an ion flow applied to a thin toner layer formed on a toner carrier to invert the charge of the toner. An image forming method in which only the toner whose charge has been inverted is transferred to a transfer material is disclosed in which a voltage having the same polarity as the toner is applied to the toner layer thickness forming means.

[0010]

However, in the above-mentioned Japanese Patent Application Laid-Open No. 5-61299, since the contact area between the toner layer thickness forming means and the toner carrier is small, the opposite polarity toner is completely removed. Could not.

In recent years, the use of external additives has been increasing in order to improve various toner characteristics such as charging characteristics and fluidity of the toner. However, external additives (for example, silica and titania) have been used. It has been known that toner containing a large amount of toner passes through the toner layer thickness regulating means. JP-A-2-10
In the methods disclosed in Japanese Patent Application Laid-Open No. 9070 and Japanese Patent Application Laid-Open No. 10-123823, there is a possibility that a uniform image is obtained by reducing the stress applied to the toner and a stable image is formed. There is a possibility that image quality may be degraded due to toner slippage.

For this reason, it is important to reduce the amount of toner charged to the opposite polarity, to uniformly charge the toner, to prevent the toner from slipping through, and to stably charge the toner to the same polarity.

According to the present invention, an endless belt (endless member) is used as a toner layer thickness regulating means, a contact area with a developing roller (toner carrier) is increased, and a voltage is applied to the toner layer thickness regulating means. The purpose of this is to discharge and collect the opposite polarity toner in the toner layer. As a result, by preventing toner of opposite polarity from being carried into the developing area with the photosensitive drum (electrostatic latent image carrier), image fog is reduced, image quality deterioration is reduced, and An object of the present invention is to provide a high-quality image by preventing the toner from passing through by forming the layer thickness regulating means in a belt shape, and by appropriately charging the toner.

[0014]

SUMMARY OF THE INVENTION The present invention is directed to a rotatable toner carrier for conveying toner charged to a predetermined polarity, supply means for supplying toner to the toner carrier, and a toner carrier on the toner carrier. Developing means for developing the electrostatic latent image on the electrostatic latent image carrier by bringing the toner on the toner carrier into contact with the electrostatic latent image carrier. In the one-component developing device, the toner layer thickness regulating means comprises a rotatable endless member abutting on the toner carrier, and a plurality of support members stretching the endless member. The regulating means is provided with a voltage applying means for applying a voltage for adsorbing the poorly charged toner on the toner carrier.

Accordingly, the contact area between the toner layer thickness regulating means and the toner carrier is increased, and the thickness of the toner layer on the toner carrier can be made uniform without applying stress to the toner. Slip-through can be prevented. Further, the poorly charged toner on the toner carrier is adsorbed by the toner layer thickness regulating means, so that the poorly charged toner can be efficiently removed from the toner carrier.

Further, a toner removing means for removing the toner on the toner layer thickness regulating means is provided.

Therefore, the poorly charged toner adsorbed on the toner layer thickness regulating means can be removed, and the irregularity of the toner layer thickness regulation on the toner carrier due to the poorly charged toner adsorbed on the toner layer thickness regulating means can be reduced. This can be prevented.

The voltage applying means applies a voltage so that the electric field strength formed between the toner carrier and the toner layer thickness regulating means becomes different from the electric field strength in the toner conveying direction. ing.

Further, a voltage is applied so that the electric field strength is higher on the downstream side than on the upstream side in the toner conveying direction.

Therefore, by changing the state of formation of the toner layer on the toner carrier, it is possible to more efficiently remove the poorly charged toner.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus to which the one-component developing device of the present invention is applied will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an image forming apparatus to which a one-component developing apparatus of the present invention is applied. In this image forming apparatus, a metal drum such as aluminum is used as a base material 1a, and selenium (S) is formed on the outer peripheral surface thereof. Se) or organic photoconductor (OP)
A photosensitive drum (electrostatic latent image carrier) 1 on which a photosensitive receiving layer 1b such as C) is applied in the form of a thin film is disposed, and a charging device (for example, a tungsten wire or the like) is provided around the photosensitive drum 1. Charging wire, metal shield plate, corona charger consisting of grit plate, charging roller, charging brush, etc.) 2
And lasers and LEDs (Light Emitting
Exposure device 3 composed of a diode (Dode) and one-component developing device 4
And a transfer device (for example, a corona charger, a transfer roller, a transfer brush, etc.) 5, a cleaning device (for example, a cleaning blade) 6, and a static eliminator (for example, a static elimination lamp) 7.

The photosensitive drum 1 is first uniformly charged by the charging device 2 and then exposed in accordance with the image information.
Thus, light is irradiated on the photosensitive drum 1 to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 1 is
The toner in the one-component developing device 4 is moved by a developing electric field formed between the photosensitive drum 1 and the one-component developing device 4 and is visualized as a toner image.

This toner image is transferred onto a recording paper P as a recording medium by a transfer device 5, and the recording paper P on which the toner image has been transferred is conveyed to a fixing device 8 composed of a pair of rollers. The toner image is fixed on the recording paper P.

After the toner image is transferred onto the recording paper P, the toner remaining on the photosensitive drum 1 is removed by the cleaning device 6, and the electric charge on the photosensitive drum 1 is removed by the charge removing device 7.
To eliminate the charge.

Next, a first embodiment of the one-component developing device 4 will be described with reference to FIG.

FIG. 2 is a schematic configuration diagram of the first embodiment of the one-component developing device 4. The non-magnetic one-component developer (toner) in the device is rotated by a rotation of a toner supply roller (toner supply means) 11 (direction a). Rotation) to the developing roller (toner carrier)
12 is supplied. The toner supplied to the developing roller 12 becomes a multilayer toner layer by an electric field between the toner supply roller 11 and the developing roller 12, and is electrostatically attracted and held on the developing roller 12.

The multi-layered toner layer on the developing roller 12 is conveyed in the direction b by the rotation of the developing roller 12, and is brought into contact with the developing roller 12 in contact with the toner layer thickness regulating means 13.
, The predetermined charge is applied by the toner layer thickness regulating means 13 and the layer thickness is regulated uniformly. The toner layer is conveyed to a developing area facing the photosensitive drum 1, and the electrostatic latent image on the photosensitive drum 1 is Is developed.

As a method of developing the electrostatic latent image on the photosensitive drum 1, contact development in which the developing roller 12 and the photosensitive drum 1 are brought into contact, or non-contact development in which development is carried out in a non-contact manner, may be employed. Good.

The toner which has not been involved in the development in the developing area is carried to the toner supply roller 11 and is
Is scraped off by the toner supply roller 11 rotating in the opposite direction. Thus, the developing roller 12 is initialized.

The developing roller 12 is made of, for example, a metal material such as aluminum, urethane, silicone, EPDM.
A rubber material such as (ethylene propylene) or a material obtained by adding a conductive agent such as carbon black or ions to the rubber material is used, and its surface has irregularities of several μm to several tens μm.

The toner supply roller 11 is, for example,
Metal materials such as aluminum, urethane, silicone, E
Rubber materials such as PDM (ethylene propylene), and
A material obtained by adding a conductive agent such as carbon black or ion to the rubber material is used, and a foamed rubber material may be used.

A power supply 9 for applying a voltage to the developing roller 12 and the toner supply roller 11 is provided.

At the contact portion A, the driving roller 14a
A driven roller 14b and a toner layer thickness regulating member (hereinafter, referred to as a toner layer thickness regulating belt) 13 composed of an endless belt stretched between the two rollers are provided. And at least three points (the contact points A1 and A2 where the driving roller 14a and the driven roller 14b contact the developing roller 12 and the contact point A3 where the toner layer thickness regulating belt 13 contacts the developing roller 12). It is arranged and rotated in the direction of arrow c.

The driving roller 14a and the driven roller 1a are driven to apply a voltage to the toner layer thickness regulating belt 13.
A first power supply 15 and a second power supply 16 are connected to 4b, respectively. The voltage is applied to the toner layer thickness regulating belt 13 as shown in FIG.
A common power supply 18 may be provided for b.

The contact pressure between the toner layer thickness regulating belt 13 and the developing roller is set to an appropriate value according to the pressing force of the driving roller 14a and the driven roller 14b, the material used, and the shape (thickness).

The drive roller 14a and the driven roller 1
As the material of 4b, a material obtained by adding a conductive agent such as carbon black or ions to a metal material such as aluminum or stainless steel, or a rubber material such as urethane, silicone, or EPDM is used. As a material of the toner layer thickness regulation belt 13, a thin metal sheet such as stainless steel, PTFE (polytetrafluoroeletin), ETFE (eletine-tetrafluoroeletin copolymer), polyimide, polyvinylidene fluoride, or the like is used. A conductive agent such as carbon black is added to the above-mentioned material in order to prevent charges from accumulating on the toner layer thickness regulating belt 13, and the volume resistivity is 10 ⁹ Ω ·
It is preferable to use one having a size of about cm or less.

When a voltage is applied to the toner layer thickness regulating belt 13 when passing through the contact portion A (regions A1 to A3), toner charged to a desired polarity is developed from the toner layer thickness regulating belt 13 side. As the toner moves on the roller 12, the opposite polarity toner on the toner layer surface is attracted to the toner layer thickness regulating belt 13 side.

The opposite polarity toner adsorbed on the toner layer thickness regulating belt 13 is conveyed in the rotation direction of the toner layer thickness regulating belt 13 and discharged from the contact portion A. For example, the toner is removed by the blade-shaped toner removing means 17. It is removed from the thickness regulation belt 13.

This is because the opposite polarity toner adhered to the toner layer thickness regulating belt 13 is not removed, and when the toner is transported to the contact portion A again, the toner between the toner adhered to the toner layer thickness regulating belt 13 and the developing roller 12 is removed. This is to prevent further occurrence of frictional charging, which causes problems when charging the toner to a desired polarity, and also prevents the toner from being fused to the toner layer thickness regulating belt 13.

As described above, the reverse polarity toner collected on the toner layer thickness regulating belt 13 is scraped off by the toner removing means 17 and returned into the developing device.

In the first embodiment, as described above, the voltage is applied to each of the driving roller 14a and the driven roller 14b which stretches the toner layer thickness regulating belt 13 (in this case, the toner layer thickness is adjusted). Regulation belt 13
Is a semiconductive material).

To remove the toner of the opposite polarity, the same voltage (a voltage having the same polarity as the desired charging polarity) is applied to the driving roller 14a and the driven roller 14b, so that the developing roller 12 and the toner layer thickness regulating belt 13 A method of extending the time of exposure to the electric field formed therebetween can be considered. However, by changing the electric field intensity between the developing roller 12 and the toner layer thickness regulating belt 13, it is possible to more efficiently remove the toner. is there.

Developing roller 12 and toner layer thickness regulating belt 1
As the different electric field formed between the first and third toner cells, it is preferable that the electric field on the downstream side is stronger than the electric field on the upstream side in the toner conveying direction.

In this case, the pressing force of the driving roller 14a and the driven roller 14b in contact with the developing roller 12 is set to be substantially the same, and the driven roller 14b is
May be increased.

The developing roller 12 and the toner layer thickness regulating belt 1
The toner transported between the contact portions 3 is gradually charged while passing through the contact portion A, and the charge amount increases. However, when the electric field formed in the contact portion A is uniform, the state of the toner layer hardly changes. . On the other hand, by changing the electric field intensity in the contact portion A, the state of the toner layer changes.

That is, as described above, if the electric field strength on the downstream side of the upstream side with respect to the toner conveying direction is increased, as the toner is conveyed, the toner of the desired charging polarity moves to the developing roller side, The opposite polarity toner is drawn to the toner layer thickness regulation belt 13 side.

Although this reduction occurs even when the electric field intensity in the contact portion A is uniform, the change in the state inside the toner layer is small, and the movement of the opposite polarity toner to the toner layer thickness regulating belt 13 side is reduced.

As a method of changing the electric field intensity in the contact portion A, it is conceivable to make the electric field intensity higher on the upstream side than on the downstream side in the toner conveying direction, but the toner is still not sufficient on the upstream side. Since it is not charged and the electric field strength becomes weaker toward the downstream side, the change in the state of the toner layer is small, and the effect of removing the opposite polarity toner is reduced.

In the first embodiment of the one-component developing apparatus, it is described that the toner layer thickness regulating belt 13 is stretched around the driving roller 14a and the driven roller 14b and is brought into contact with the developing roller 12 at three points. However, the toner layer thickness regulating belt 13 is substantially in surface contact with the contact portions A1 to A2, and the contact portion A with the developing roller 12 is brought into contact with the developing roller 12 in a long direction in the rotation direction of the developing roller 12 to have a large area. ing.

Further, a voltage having the same polarity as that of the toner having the desired charging polarity is applied to the toner layer thickness regulating belt 13 to change the intensity of the electric field in the toner layer thickness regulating belt 13 so as to be upstream in the toner conveying direction. The electric field on the downstream side from the side is made stronger.

With this configuration, since the opposite polarity toner is attached to the toner layer thickness regulating belt 13 and returned into the developing device by the toner removing means 17, the movement of the opposite polarity toner to the developing area is suppressed. be able to. Therefore, a clear image can be formed on the photosensitive drum 1, and a high-quality image with less fog can be formed. Further, it is possible to prevent the toner from slipping through the toner in which the amount of the external additive added to improve various properties of the toner is increased.

In the above description, two rollers, the driving roller 14a and the driven roller 14b, are provided. However, rollers are provided at the contact portion A3 and other portions, and different voltages are applied to the respective rollers. It may be configured to change the electric field intensity in the contact portion A by applying the electric field.

In order to change the electric field strength in the contact portion A, as shown in FIG. 3, the same voltage is applied to the drive roller 14a and the driven roller 14b from the common power source 18 to drive the drive roller 14a and the driven roller 14b. The pressing force may be set such that the driving roller 14a has a higher pressure at which the driving roller 14a contacts the developing roller 12;
a, driven roller 14b and toner layer thickness regulating belt 13
, A material having a low volume resistivity is used.

As the toner removing means 17, a blade-shaped member can be used. However, as shown in FIG. 4, a roller 19 may be arranged in contact with the toner layer thickness regulating belt 13. .

In this case, by applying a voltage having a polarity opposite to that of the opposite polarity toner to the roller 19 from the fourth power supply 20, the opposite polarity toner is once collected from the toner layer thickness regulating belt 13 by suction, and the roller 19 The opposite polarity toner attracted to the roller 19 is removed by a blade 21 which is a scraping member provided in contact with the roller 21.

In such a configuration, the blade 21
Is not directly in contact with the toner layer thickness regulating belt 13, so that the toner layer thickness regulating belt 13 is not damaged and the life of the toner layer thickness regulating belt 13 can be extended.

When the blade-shaped toner removing means is used, the toner may pass through the blade, but the roller 19 is disposed in contact with the toner layer thickness regulating belt 13 and the voltage is applied to the roller 19. Is applied, it is possible to efficiently collect the opposite polarity toner from the toner layer thickness regulating belt 13.

Accordingly, it is possible to prevent the toner that has not been completely removed from the toner layer thickness regulating belt 13 from being re-conveyed to the contact portion A and adversely affecting the charging of the toner.

The developing roller 1 is used as the roller 19.
2 and the same material as the toner supply roller 11 are used.

Further, the roller 19 does not need to be arranged in contact with the toner layer thickness regulating belt 13, but is arranged in close proximity, applies an AC voltage superimposed on a DC voltage and applies it in a non-contact manner. It may be configured to collect the polar toner.

[0062]

According to the present invention, there is provided a rotatable toner carrier for conveying toner charged to a predetermined polarity, supply means for supplying toner to the toner carrier, and a toner layer thickness on the toner carrier. One-component development for developing an electrostatic latent image on the electrostatic latent image carrier by bringing the toner on the toner carrier into contact with the electrostatic latent image carrier by providing a toner layer thickness regulating means for regulating the toner layer thickness In the apparatus, the toner layer thickness regulating means includes a rotatable endless member that comes into contact with the toner carrier, and a plurality of support members that stretch the endless member.
Since the toner layer thickness regulating means is provided with voltage applying means for applying a voltage for adsorbing the poorly charged toner on the toner carrier, the contact area between the toner layer thickness regulating means and the toner carrier becomes large. In addition, the thickness of the toner layer on the toner carrier can be made uniform without applying stress to the toner, and the toner can be prevented from slipping through. Further, the poorly charged toner on the toner carrier is adsorbed to the toner layer thickness regulating means, so that the poorly charged toner can be efficiently removed from the toner carrier.

Further, since the toner removing means for removing the toner on the toner layer thickness regulating means is provided, it is possible to remove the poorly charged toner adsorbed on the toner layer thickness regulating means, and to adsorb the toner on the toner layer thickness regulating means. It is possible to prevent the regulation of the thickness of the toner layer on the toner carrier from becoming uneven due to the poorly charged toner.

The voltage applying means applies a voltage so that the electric field strength formed between the toner carrier and the toner layer thickness regulating means becomes different from the electric field strength in the toner conveying direction. Therefore, by changing the state of formation of the toner layer on the toner carrier, it is possible to more efficiently remove the poorly charged toner.

Further, since the voltage is applied so that the electric field strength is higher on the downstream side than on the upstream side in the toner conveying direction, the change in the formation state of the toner layer on the toner carrier becomes more remarkable. In addition, it is possible to more efficiently remove poorly charged toner.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus to which a one-component developing device of the present invention is applied.

FIG. 2 is a schematic sectional view of Embodiment 1 of the one-component developing device of the present invention.

FIG. 3 is a schematic sectional view of Embodiment 1 of the one-component developing device of the present invention.

FIG. 4 is a schematic sectional view of Embodiment 3 of the one-component developing device of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 4 one-component developing device 11 toner supply roller 12 developing roller 13 toner layer thickness regulating belt 14 a drive roller 14 b driven roller 15 first power supply 16 second power supply 17 toner removing means

Claims (4)

[Claims] 1. A rotatable toner carrier for conveying toner charged to a predetermined polarity, a supply unit for supplying toner to the toner carrier, and a toner for regulating a toner layer thickness on the toner carrier. A one-component developing device that includes a layer thickness regulating unit and develops an electrostatic latent image on the electrostatic latent image carrier by bringing the toner on the toner carrier into contact with the electrostatic latent image carrier; The toner layer thickness regulating means comprises a rotatable endless member abutting on the toner carrier, and a plurality of support members which stretch the endless member. The toner layer thickness regulating means is provided on the toner carrier. A voltage application means for applying a voltage for adsorbing the poorly charged toner. 2. The one-component developing apparatus according to claim 1, further comprising a toner removing unit for removing the toner on the toner layer thickness regulating unit. 3. The voltage applying means applies a voltage so that the electric field strength formed between the toner carrier and the toner layer thickness regulating means is different from the electric field strength in the toner conveying direction. The one-component developing device according to claim 1, wherein: 4. The one-component developing apparatus according to claim 3, wherein said voltage applying means applies a voltage such that an electric field intensity is higher on the downstream side than on the upstream side in the toner conveying direction.