JP2000112219A - Developing device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one-component non-magnetic developing device for an image forming device capable of preventing lowering of the image density or the like by occasionally refreshing a developing roller. SOLUTION: In this developing device for the image forming device provided with the developing roller 10 for developing an electrostatic latent image thereon by transporting the developer of non-magnetic one-component to the developing position on the image carrier 1, a feeding roller 11 being held in contact with and rotated by the developing roller 10, for feeding the developer on the developing roller, a blade 12 for controlling the developer quantity on the developing roller, and a developer removing member 16 being held in contact with the developing roller allowed to pass through the developing position for removing the residual developer on the surface thereof, the device is provided with controlling means for making the developer removing member 16 attachable to and detachable from the developing roller 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device provided in an electrophotographic image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly to a developing device using a non-magnetic one-component developer.

[0002]

2. Description of the Related Art Dry development is widely used as development in electrophotographic copying techniques such as copying machines, and there are two-component development and one-component development in dry development. Among them, the one-component developing method does not use a magnetic material (carrier), which is advantageous for miniaturization and cost reduction of the apparatus. Recently, the one-component developing method is mainly used for small printers and small copying machines.

Further, the developing device has, for example, little wear of the image carrier and the developing roller, has a long life, and enables superposition development, so that a gap is provided between the developing roller and the surface of the image carrier. A non-contact developing method is adopted which is arranged so as to have the same. In a color image forming apparatus, a plurality of developing devices use a non-magnetic toner that is advantageous for colorization.

FIG. 3 is a schematic view showing an example of the configuration of the conventional developing device. Generally, a developing device of a non-magnetic one-component developing system includes a developing hopper as a housing of a developing unit,
It comprises a developing roller 10, a supply roller 11, a doctor blade 12, and the like. The developing roller 10 is disposed in contact with or in close proximity to the developing position on the drum photoreceptor 1, and is rotatably supported in the unit main body together with the supply roller 11 that is in rotational contact with the developing roller 10.

A toner as a developer is contained in a developing hopper, and the toner is fluidized by rotation of the agitator 13 and is conveyed toward the supply roller 11. The toner on the supply roller 11 adheres to the developing roller 10 and is subsequently thinned by a doctor blade 12. The thinned toner selectively adheres to the electrostatic latent image on the photoreceptor 1 and visualizes this.

In the above-described conventional apparatus, the toner remaining on the developing roller 10 without being consumed for development is supplied to the supply roller 1 again.
1, and passes under the doctor blade 12.
In addition, the toner chargeability and transportability of the toner of 0 are deteriorated. For example, in an image formation with a small image (printing) area ratio, the toner on the developing roller 10 remains on the developing roller 10 without being transferred to the photoreceptor 1, so that this toner layer is formed on the supply roller 11 and the doctor blade. 12, the toner agglomeration degree increases and the chargeability deteriorates. This happens when,
This makes it difficult for the toner to be conveyed onto the photoreceptor 1, and causes problems such as uneven image density and image dust.

For the purpose of solving such a problem, for example, Japanese Patent Application Laid-Open No. Hei 10-39631 discloses that a developing roller 10 is disposed in contact with the surface of a developing roller 10 after development.
A non-magnetic one-component developing device provided with a toner collecting member for collecting the remaining toner on the surface is disclosed.

[0008]

However, a non-magnetic one-component developing device provided with the above-mentioned toner collecting member (Japanese Patent Laid-Open No.
No. 39631), since the toner removing member is always in contact with the developing roller 10, the toner on the developing roller 10 is scraped off, and the amount of toner required for development becomes insufficient. There is a problem that the concentration decreases.

In particular, as the developing roller 10, a roller in which a conductor portion and a dielectric portion are regularly distributed in a small area on the surface thereof may be used, but a minute closed electric field for forming such a small electric field may be used. In an apparatus adopting the system, the shortage of the toner amount on the developing roller 10 becomes a more serious problem because the conveying force of the multilayer toner is weak.

Therefore, an object of the present invention is to provide a developing roller 10
To provide a developing device of an image forming apparatus capable of removing and collecting toner as required from above, returning the developer transportability by the developing roller 10 to a normal timely, and preventing a decrease in image density and the like. It is in.

[0011]

A developing device of an image forming apparatus according to the present invention, which achieves the above object, transports a non-magnetic one-component developer carried on a surface to a developing position on an image carrier by rotation thereof. A developing roller that reversely develops the electrostatic latent image with the developing roller, a supply roller that rotates in contact with the developing roller and supplies the developer onto the developing roller, and a developer amount on the developing roller that is conveyed to the developing position. And a developer removing member that removes the developer remaining on the developing roller by coming into contact with the surface of the developing roller that has passed through the developing position. The image forming apparatus is characterized in that control means is provided for allowing the removing member to approach and separate from the developing roller.

The image forming apparatus further comprises a developer amount detecting means capable of detecting an amount of developer used for developing the electrostatic latent image on the image carrier, and performs the control based on a detection result of the developer amount detecting means. The drive of the developer removing member can be controlled by means. Further, it is preferable that the image forming apparatus further includes a removing bias unit for applying a bias voltage to the developer removing member, and the removing bias unit applies a bias voltage including an AC component.

Further, the apparatus further comprises a supply bias means for applying a bias voltage to the supply roller, and after the removal operation by the developer removing member, the control means causes the supply bias means to apply a bias voltage to the supply roller. Good. In this case, after the removing operation by the developer removing member, the supply bias unit may apply a bias voltage higher than that in a normal developing operation by the control unit.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as one embodiment of the present invention,
A two-color digital image forming apparatus will be described with reference to the drawings.
FIG. 1 schematically illustrates a schematic configuration of a two-color digital image forming apparatus according to the present embodiment.

The photosensitive member 1 is uniformly charged by the first charger 2, and an electrostatic image is formed on the surface of the photosensitive member 1 by the first exposure L1 (for example, exposure for a black image). This electrostatic image is thereafter developed by a first developing device 3 (for example, a black developing device for black image exposure), and is developed into a one-color toner image. Next, the surface of the photoreceptor 1 on which the first color toner image is formed is uniformly charged again by the second charger 4, and the second surface is overlapped with the first color toner image at the same position.
An electrostatic image is formed by exposure L2 (for example, red image exposure), and an electrostatic image is formed by a second developing device 5 (for example, a red developing device).
The image is visualized by the color toner, and a two-color superimposed toner image is formed on the photoconductor 1. As a light source for the first exposure L1 and the second exposure L2, a laser diode, an LSD, or the like can be used.

On the downstream side of the second developing unit 5, a density sensor 6 as a developer amount detecting means capable of detecting a detection pattern formed on the photoreceptor 1 or a toner adhesion amount at a specific portion in an image. Is provided. From the output of the density sensor 6, the toner adhesion amount on the photoconductor 1 is obtained. The data of the toner adhesion amount corresponds to the amount of the developer consumed in the development of the electrostatic latent image. When the output is small, it indicates that unnecessary toner remains on the developing roller. I have. As will be described later in detail, in the present embodiment, the amount of the developer consumed for the development is determined, and if it is necessary to remove the residual toner, the developing roller of the second developing device 5 is refreshed.

The transfer belt serving as the transfer unit 7 includes the photosensitive member 1
To form a transfer portion. The toner image on the photoreceptor 1 is transferred onto a transfer sheet by a transfer bias of a transfer unit 7, and the transfer sheet is simultaneously conveyed on a belt of the transfer unit 7 toward a fixing unit (not shown). The toner is fixed. A cleaning blade 9 of a cleaning unit 8 is in contact with the photoreceptor 1 on the downstream side of the transfer unit, and the transfer residual toner remaining on the surface is removed and cleaned.

FIG. 2 shows a schematic configuration of the second developing device 5 of FIG. In this figure, reference numeral 10 denotes a developing roller,
Reference numeral 11 denotes a supply roller, and reference numeral 12 denotes a doctor blade 1.
2 is shown. The supply roller 11 for supplying the toner as the developer has a sponge-shaped surface layer, and sends the toner conveyed by the rotation of the agitator 13 to a nip portion between the supply roller 11 and the development roller 10. The toner charged by friction at the nip portion is carried on the developing roller 10, and the amount of passage is regulated by the doctor blade 12 which is in contact with the surface of the developing roller 10 in the direction in which the toner is rotated. It is sent to a developing position on the photoconductor 1.

Generally, a non-magnetic one-component developing apparatus uses a conductive member for the supply roller 11, the developing roller 10, and the like, and is connected to a power source for applying a predetermined bias voltage. The bias voltage applied to each portion forms an electric field in the toner transport direction, and enables stable transport of non-magnetic one-component toner having no carrier. That is, each bias voltage is controlled together with the rotation of each member so that the amount of toner carried / conveyed on the developing roller 10 does not fall below the amount of toner required for development and the image (print) density does not decrease. Have been.

Also in the second developing device 5 of this embodiment, a developing bias power supply 14 as a developing bias means is connected to the developing roller 10 and a supply bias power supply 15 as a supply bias means is connected to the supply roller 11. A predetermined bias voltage can be applied. The developing roller 1
Numeral 0 is arranged so as to maintain a predetermined gap with the photoconductor 1 via a spacer roller (not shown) so as to perform non-contact type development.

Toner removing member 1 as developer removing member
For 6, a conductive member having a fur brush structure or the like can be used. The toner removing member 16 is rotatably supported in contact with the longitudinal direction of the developing roller 10 and
It is arranged so as to be able to freely move toward and away from zero. This contact position is a position on the outer periphery of the developing roller 10 downstream of the developing position and upstream of the nip portion with the supply roller 11. By the toner removing member 16 maintained in such a contact state, the toner on the developing roller 10 remaining without being transferred onto the photoconductor 1 during development is removed and collected.

The toner removing member 16 is driven and controlled by a contacting / separating mechanism (not shown) so that the toner removing member 16 can come into contact with and separate from the surface of the developing roller 10. Such a contact / separation mechanism can be configured by, for example, providing a solenoid that allows the support portions at both ends of the toner removing member 16 to move toward and away from the developing roller 10. Further, the toner removing member 16 is provided with a toner scraping member 17 (bias roller) that is in rotational contact with an outer peripheral portion different from the contact position with the developing roller 10.

To the toner removing member 16 and the toner scraping member 17 in contact therewith, bias power supplies 18 and 19 as removing bias means are connected, respectively.
These bias power supplies 18 and 19 can apply a removing bias having a polarity opposite to that of the toner, so that the residual toner on the developing roller 10 is transferred to the toner removing member 16 and further from the toner removing member 16 to the toner scraping member 17. To form an electric field.

The developing device of this embodiment refreshes the developing roller 10 (cleans the undeveloped toner) after the developing operation with low toner consumption (image area ratio).
The drive of the contact / separation mechanism of the toner removing member 16 is controlled at a predetermined timing.

More specifically, the density sensor 6 periodically detects a detection pattern or the amount of toner adhering to a specific portion in an image, and uses the data as control means for a mechanism for moving the toner removing member 16 into and out of contact. The data is sent to the control device and compared with the specified value. Here, when it is determined that the toner adhesion amount is smaller than the specified amount, the toner removing member 16 is rotationally driven, a bias voltage is applied thereto, and the toner removing member 16 is moved in the direction to contact the developing roller 10.

In the present embodiment, the control is performed in accordance with the amount of toner adhered to the photosensitive member 1. However, the present invention is not limited to such control. Whether or not to perform the toner removing operation may be determined by comparing the specified value in advance. In this case, the removal operation is performed when the image area ratio is smaller than the specified value.

The toner adhering to the toner removing member 16 is removed by a toner scraping member 17 to which a bias voltage is applied.
The toner removing member 16
When a bias voltage including an AC component (AC component) is used as the bias voltage applied to the, it is possible to reliably remove, for example, a weakly charged toner and a reversely charged toner.
Aggregated toner having changed in chargeability and the like on the developing roller 10 can be efficiently removed.

Then, after a sufficient density is detected in the developed image or after a predetermined time, the toner removing member 16 is separated from the developing roller 10 to terminate the toner removing operation. As described above, the toner removing operation is performed as needed. However, when the developing roller 10 is refreshed, the amount of toner carried on the surface thereof is temporarily reduced. It's easy to do.

Therefore, in order to prevent the density from dropping after the above-described removing operation, a bias voltage is applied to the supply roller 11 immediately after the above-described toner removing operation is performed, and the toner is transferred from the supply roller 11 to the developing roller 10. It is good to make up for toner shortage. If the lowering of the density still does not disappear, by performing variable control of the bias voltage for applying a higher bias voltage to the supply roller 11 than during normal image formation, it is possible to reliably prevent a temporary reduction in the image density. .

[0030]

As described above, the developing device of the image forming apparatus of the present invention transports the non-magnetic one-component developer carried on the surface to the developing position on the image carrier by rotating the developer. A developing roller that reversely develops the latent image, a supply roller that rotates in contact with the developing roller and supplies the developer onto the developing roller, and regulates the amount of the developer on the developing roller that is transported to the developing position. A developing device for an image forming apparatus, comprising: a blade; and a developer removing member that contacts a surface of the developing roller that has passed the developing position and removes a developer remaining on the developing roller. Since the control unit is provided with a control means capable of coming in contact with and separating from the developing roller, the toner on the developing roller can be removed as needed by the developer removing member, and the image in the non-magnetic one-component developing device can be removed. Every decrease in the abnormal images such as image dust can be prevented.

There is provided a removing bias means for applying a bias voltage to the developer removing member, and the removing bias means comprises:
According to the configuration for applying a bias voltage including an AC component,
By the developer removing member to which the AC bias is applied, it is possible to reliably remove the developer on the developing roller including the weakly charged developer and the developers having different polarities.

Further, the apparatus has a supply bias means for applying a bias voltage to the supply roller, and after the removal operation by the developer removing member, the control means causes the supply bias means to apply a bias voltage to the supply roller. According to the configuration, the supply bias applied after the developer removing operation can eliminate the temporary shortage of the developer.

In addition, according to the configuration in which the supply bias means applies a bias voltage higher than that during the normal developing operation by the control means after the developer removing operation by the developer removing member, Temporary shortage of developer and lowering of density can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment.

FIG. 2 is an enlarged view of a second developing device of FIG.

FIG. 3 is a schematic diagram illustrating a configuration of a conventional developing device.

DESCRIPTION OF SYMBOLS 1 Image carrier 3, 5 Developing device 6 Developer amount detecting means (density sensor) 10 Developing roller 11 Supply roller 12 Blade (doctor blade) 15 Supply bias means 16 Developer removing member (Toner removing member) 18 Removal bias means

Claims (5)

[Claims] A developing roller that reversely develops an electrostatic latent image by transporting a non-magnetic one-component developer carried on a surface thereof to a developing position on an image carrier by rotation thereof; A supply roller that rotates and supplies the developer onto the developing roller, a blade that regulates the amount of the developer on the developing roller conveyed to the developing position, and a blade that contacts the surface of the developing roller that has passed the developing position. A developer removing member for removing the developer remaining on the developing roller; and a control device capable of moving the developer removing member toward and away from the developing roller. A developing device for an image forming apparatus, comprising: 2. An image forming apparatus comprising: a developer amount detecting unit configured to detect a developer amount used for developing an electrostatic latent image on the image carrier;
2. The developing device for an image forming apparatus according to claim 1, wherein the control unit controls the driving of the developer removing member based on a detection result of the developer amount detecting unit. 3. The method according to claim 1, further comprising removing bias means for applying a bias voltage to the developer removing member, wherein the removing bias means applies a bias voltage containing an AC component. Of the image forming apparatus. And a supply bias means for applying a bias voltage to the supply roller. After the developer is removed by the developer removing member, the control means controls the supply bias means to apply a bias voltage to the supply roller. 4. The developing device for an image forming apparatus according to claim 1, wherein the voltage is applied. 5. The image forming apparatus according to claim 4, wherein, after the removing operation by the developer removing member, the supply bias unit applies a bias voltage larger than that in a normal developing operation by the control unit. Equipment development device.