JP2000147872A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate toner even when toner is stuck to magnetic particles forming a magnetic brush of an electrifying device. SOLUTION: In this image forming device, a magnetic particles cleaning device 20 eliminating the toner stuck to the magnetic particles 11 of the magnetic brush 10 by impressing voltage from a power source 13 is provided adjacent to the magnetic brush 10 of the electrifying device 2. Furthermore, a sensor 15 detecting the concentration of toner in the area of the magnetic brush 10 and a control device 50 to vary the voltage impressed from the power source 13 to the magnetic particles cleaning device 20 according to the concentration of the toner detected by the sensor 15 are provided.

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 provided with a magnetic brush in a charging device for charging an uncharged body.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile has a charging device for charging a non-charged photosensitive member. Such a charging device is generally disposed downstream of the cleaning device for removing the toner on the photoconductor in the moving direction of the photoconductor. The charging device includes a contact-type charging device that performs charging in a state where a charging member such as a charging roller, a charging blade, or a charging brush is directly in contact with the surface of the photoconductor, and a charging member that contacts the surface of the photoconductor. On the other hand, there is a non-contact type charging device that performs charging in a non-contact state. On the other hand, some charging devices use a magnetic brush to charge the photosensitive member (see, for example, JP-A-9-305509 and JP-A-10-48921).

[0003]

However, in such a contact type or non-contact type charging device, if the toner remaining on the surface of the photoreceptor adheres to the charging member, the charging performance is deteriorated. was there. Therefore, in order to solve such a problem, a conventional charging device is provided with a cleaning mechanism for the charging device.

Further, even in a charging device using a magnetic brush, if residual toner adheres to the photoreceptor, the toner adheres to the magnetic particles forming the magnetic brush, which also lowers the charging performance. There was that. However, in a conventional charging device using such a magnetic brush, that is, for example, those described in JP-A-9-305509 and JP-A-10-48921, the toner attached to the magnetic brush is removed. No effective equipment was provided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is directed to a charging device using a magnetic brush, wherein toner adheres to magnetic particles forming the magnetic brush.
An object of the present invention is to make it possible to remove the toner.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention applies a charging bias to a magnetic brush in which a magnetic brush having a brush portion formed by magnetic particles is in contact with an object to be charged. In an image forming apparatus provided with a charging device for charging an object to be charged, a magnetic particle cleaning device is disposed adjacent to the magnetic brush and removes toner attached to the magnetic particles when a voltage is applied. A device is provided.

Further, the image forming apparatus is provided with toner density detecting means for detecting the density of toner present in the magnetic brush portion, and the magnetic particle cleaning apparatus is provided in accordance with the toner density detected by the toner density detecting means. It is preferable to provide an applied voltage changing means for changing the voltage applied to the device.
Then, the applied voltage changing means changes the voltage applied to the magnetic particle cleaning device according to the toner concentration detected by the toner density detecting means, and also changes the charging bias applied to the magnetic brush. Good to do.

Further, in any one of the above image forming apparatuses, a mode for selecting a mode in which a voltage is applied to the magnetic particle cleaning device to perform a magnetic particle cleaning operation for removing toner attached to the magnetic particles even during non-image formation. Mode selection means may be provided. In the magnetic particle cleaning device, the cleaning member may be formed in a roller shape. Further, in any of the above image forming apparatuses, a toner recirculation conveyance path for recirculating the toner collected by the magnetic particle cleaning device to the developing device may be provided.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an image forming unit of an image forming apparatus according to an embodiment of the present invention. In this image forming apparatus, a drum-shaped photoreceptor 1 which is a charged object is provided in an image forming unit, a charging device 2 is provided around the photoreceptor 1, and a rotation direction of the photoreceptor 1 with respect to the charging device 2 (arrow). A) A developing device 6 and a transfer roller 7 constituting a transfer device are provided on the downstream side, respectively. The surface of the photoconductor 1 is irradiated with light for writing an image (laser light or the like) from the exposure device 9.

The photoconductor 1 is, for example, an organic photoconductor (OPC)
The photoreceptor 1 is formed by coating a photoreceptor layer on the outside of a cylindrical aluminum body, and is rotated in the direction of arrow A by a motor (not shown).

In this image forming apparatus, the surface of the photoreceptor 1 is uniformly charged by the charging device 2 and irradiated with light by the exposure device 9 at a predetermined timing to form a latent image. The latent image moves in the same direction as the photoconductor 1 rotates in the direction indicated by the arrow A. When the latent image moves to the position of the developing sleeve 6a of the developing device 6, toner is adhered to the latent image and a latent image is formed. Image).

When the developed image moves to a transfer position where the transfer roller 7 is located, the transfer image is transferred to the transfer paper P by the transfer roller 7. The transfer paper P is fed from a paper feed unit and is conveyed toward the transfer position by a registration roller (not shown) at an accurate timing coincident with a visible image on the photoconductor 1. The transfer paper P on which the developed image has been transferred is separated from the photoreceptor 1 and conveyed to a fixing device (not shown), where the toner is fixed, and then discharged to a discharge tray or the like outside the device.

The residual toner remaining on the photoreceptor 1 after the transfer is removed by the charging device 2 also serving as a cleaning device and the magnetic particle cleaning device 20, and the remaining toner on the photoreceptor 1 will be described in detail later. The remaining potential is removed by a neutralizing lamp (not shown) to prepare for the next charging by the charging device 2.

The charging device 2 applies a charging bias from a power supply 12 to the magnetic brush 10 in a state where the magnetic brush 10 in which a brush portion is formed by the magnetic particles 11 is in contact with the photosensitive member 1. Magnetic brush 1
A minute discharge is caused by a potential difference generated between 0 and the photoconductor 1, thereby charging the photoconductor 1. The photoreceptor 1 is also charged by injecting electric charge into the photoreceptor 1 when a current flows from the magnetic brush 10 to the photoreceptor 1.

The charging device 2 is provided with a magnet roller 17 inside a non-magnetic sleeve 16 which carries the magnetic particles 11 by rotating in the direction of arrow C, and the magnet roller 17 displaces the magnetic particles 11 by a magnetic force. It is held on the surface of the magnetic sleeve 16. Then, in this embodiment, a charging bias (voltage) in which AC and DC components for charging the photoconductor 1 are superimposed on the non-magnetic sleeve 16.
Is applied from the power supply 12. The photosensitive member 1 can be charged even if only the DC component excluding the AC component is applied to the non-magnetic sleeve 16, and it is necessary to apply a charging bias in which the AC and DC components are superimposed. There is no.

At a position adjacent to the magnetic brush 10 of the charging device 2, a voltage (bias) is applied to a cleaning member 21 from a power source 13 to remove a toner attached to the magnetic particles 11 by a magnetic particle cleaning device 20.
Is provided. In this embodiment, the cleaning member 21 is formed in a roller shape and is rotatable in the direction of arrow B, and the surface of the cleaning member 21 is brought into contact with the toner collecting blade 22 so that the cleaning member 21 The toner attached to the surface is scraped off.

In this embodiment, the toner adhered to the magnetic particles 11 of the magnetic brush 10 is cleaned by the cleaning member 2.
In the normal mode, a voltage obtained by superimposing AC and DC components on the cleaning member 21 is applied from the power supply 13 in order to attract the cleaning member 21.

Since the toner attached to the magnetic particles 11 of the magnetic brush 10 is not only one polarity, the power source 1
The polarity of the voltage applied to the cleaning member 21 from 3 is
The switch 14 can be switched between plus and minus. The application of the voltage to the cleaning member 21 does not always need to be applied during image formation.

In order to most efficiently attract and collect the toner adhering to the magnetic particles 11 to the cleaning member 21, a voltage is fixed to one of the polarities during image formation, and a voltage is applied during non-image formation. It is advisable to apply the voltage sequentially in both directions only at times. That is, at the time of non-image formation, a voltage applied from the power supply 13 to the cleaning member 21 is first applied by superimposing an AC voltage on a positive DC voltage for about several tens of seconds, and then a negative voltage for about several tens seconds. A voltage obtained by superimposing an AC voltage on a DC voltage is applied.

The charging device 2 is provided with a sensor 15 serving as a toner concentration detecting means for detecting the concentration of the toner present on the magnetic brush 10. The image forming apparatus includes a cleaning member 21 of the magnetic particle cleaning apparatus 20 according to the toner concentration detected by the sensor 15.
A control device 50 which functions as an applied voltage changing means for changing the voltage applied to the power supply 13 by controlling the power supply 13 is provided. The control device 50 also functions as means for changing the charging bias applied to the magnetic brush 10 by controlling the power supply 12.

The sensor 15 may be any sensor as long as it can detect the density of the toner existing in the magnetic brush 10 portion. A device that detects the density or detects a change in the resistance value of the magnetic brush 10 from the charging current and thereby detects the toner concentration is used.

The image forming apparatus also has a mode for selecting a mode in which a magnetic particle cleaning operation for applying a voltage to the magnetic particle cleaning device 20 to remove toner adhered to the magnetic brush 10 is performed even during non-image formation. A mode selection key 25 as selection means is provided on an operation panel (not shown). The control device 50 includes a central processing unit (CPU) having various judgment and processing functions, a ROM storing each processing program and fixed data, a RAM serving as a data memory for storing processing data, and an input / output circuit (I / O).
O).

The control device 50 inputs various sensor signals and the like from the sensor 15 and other sensors provided in each part of the image forming apparatus at a predetermined timing. The signal output when is pressed is input. The control device 50
Outputs a signal for applying a voltage (bias) to the power supplies 12 and 13 at a predetermined timing.
Further, signals for driving various loads provided in each section of the image forming apparatus are output at predetermined timings.

In this embodiment, as described above, the rotation direction C of the non-magnetic sleeve 16 of the charging device 2 is used.
And the rotation direction A of the photoconductor 1 are set to the same direction (the direction of relative movement at the contact portions). The reason is shown in Figure 1.
In the embodiment shown in FIG. 2, a cleaning device for cleaning residual toner remaining on the surface of the photoconductor 1 after image transfer is provided like the cleaning device 8 included in the image forming apparatus of the embodiment shown in FIG. This is because the magnetic particles 11 are contaminated with the residual toner and a uniform charging potential cannot be obtained.

That is, when the rotation directions of the non-magnetic sleeve 16 and the photosensitive member 1 are changed, the magnetic brush 1
Before the magnetic particles 11 on the photoconductor 1 charge the photoconductor 1, a large amount of toner remaining on the surface of the photoconductor 1 adheres to the magnetic particles 11. 16 and the rotation direction of the photoconductor 1 must be the same. Incidentally, in the image forming apparatus provided with the cleaning device 8 as shown in FIG. No problem.

As described above, since the image forming apparatus shown in FIG. 1 is provided with the magnetic particle cleaning device 20 for removing the toner attached to the magnetic particles 11 of the magnetic brush 10, the toner attached to the magnetic particles 11 is removed. Can be removed by the magnetic particle cleaning device 20. Therefore, the charging potential of the photoconductor 1 can be stabilized, and the image formed thereby can be stabilized.

Further, the magnetic particle cleaning device 20 comprises:
As shown in FIG. 2, the magnetic brush 10 has both a function of removing the toner attached to the magnetic particles 11 and a function of collecting the residual toner on the photoconductor 1 via the magnetic brush 10. The number of parts can be reduced as much as the cleaning device 8 need not be provided.

FIG. 3 is a diagram similar to FIG. 1 showing an embodiment of an image forming apparatus provided with a toner recirculation conveyance path for recirculating the toner collected by the magnetic particle cleaning device to the developing device. Parts are given the same reference numerals. This image forming apparatus includes a magnetic particle cleaning device 2
A toner recirculation conveyance path 31 for recirculating the toner collected at 0 to the developing device 6 is provided. According to this image forming apparatus, the toner collected by the magnetic particle cleaning device 20 can be reused in the developing device 6, so that it is economical.

FIG. 4 is a view similar to FIG. 1 showing an embodiment of an image forming apparatus in which a magnetic particle cleaning device is arranged above a magnetic brush, and portions corresponding to FIG. 1 have the same reference numerals. Is attached. This image forming apparatus includes:
With respect to the image forming apparatus shown in FIG.
The only difference is that the sensor 15 is arranged on the left side of the magnetic brush 10 in FIG. Even in this case, the same operation and effect as those of the image forming apparatus in FIG. 1 can be obtained.

FIG. 5 is a view similar to FIG. 1 showing an embodiment of an image forming apparatus in which the magnetic particle cleaning device is arranged on the right side of the magnetic brush, and portions corresponding to FIG. The code is attached. This image forming apparatus includes:
In the image forming apparatus shown in FIG. 1, the magnetic particle cleaning device 20 is disposed on the right side of the magnetic brush 10 in FIG. 5 and the sensor 15 is disposed on the left side of the magnetic brush 10 in FIG. Replace with fur brush 33
The only difference is the use of. Even in this case, the same operation and effect as those of the image forming apparatus in FIG. 1 can be obtained.

A member for collecting the toner adhered to the surface of the cleaning member 21, such as the toner collecting blade 22 and the fur brush 33 shown in FIGS.
The cleaning member 21 is not limited to a blade or a fur brush, but may have any shape as long as it can scrape off toner adhered to the surface of the cleaning member 21.

[0032]

As described above, according to the present invention, the following effects can be obtained. According to the image forming apparatus of the first aspect, since the magnetic particle cleaning device for removing the toner attached to the magnetic particles is provided, the toner attached to the magnetic particles can be removed by the magnetic particle cleaning device. Therefore, since the magnetic particles can be kept in a clean state, the charging potential of the photoconductor can be stabilized. Thereby, a stable image can be obtained.

A magnetic particle cleaning device for removing toner attached to the magnetic particles of the magnetic brush;
Since the magnetic brush also serves to collect the residual toner on the photoconductor, the number of components can be reduced by eliminating the need for a dedicated cleaning device for removing the residual toner on the photoconductor. it can.

According to the image forming apparatus of the present invention, the voltage applied to the magnetic particle cleaning device can be changed according to the concentration of the toner present in the magnetic brush portion. The density of the toner existing in the toner can be kept low while keeping the density stable.

According to the image forming apparatus of the present invention, the charging bias applied to the magnetic brush can be changed. Therefore, even when the charging ability is reduced due to the effect of the toner attached to the magnetic particles, the charging is performed. By changing the bias, the charging potential of the photoconductor can be stabilized.

According to the image forming apparatus of the present invention, the magnetic particle cleaning operation for removing the toner attached to the magnetic particles can be performed not only during normal image formation but also during non-image formation. Even if the density of the toner in the inside becomes high, the density can be kept low by performing the magnetic particle cleaning operation during non-image formation. Thereby, the charging potential of the photoconductor can be stabilized.

According to the image forming apparatus of the present invention, since the cleaning member of the magnetic particle cleaning device is in the form of a roller, the cleaning member can be simply brought into sliding contact with the surface of the rotating roller by the blade-shaped toner collecting member. The toner attached to the surface of the toner can be easily collected.

According to the image forming apparatus of the sixth aspect, the toner collected by the magnetic particle cleaning device can be reused in the developing device, which is economical.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an image forming unit of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram similar to FIG. 1 showing an embodiment of an image forming apparatus provided with a cleaning device for cleaning residual toner remaining on the surface of a photoconductor after image transfer.

FIG. 3 is a configuration diagram similar to FIG. 1 showing an embodiment of an image forming apparatus provided with a toner recirculation conveyance path for recirculating toner collected by a magnetic particle cleaning device to a developing device.

FIG. 4 is a configuration diagram similar to FIG. 1, illustrating an embodiment of an image forming apparatus in which a magnetic particle cleaning device is disposed above a magnetic brush.

FIG. 5 is a configuration diagram similar to FIG. 1 showing an embodiment of an image forming apparatus in which a magnetic particle cleaning device is arranged on the right side of a magnetic brush.

[Explanation of symbols]

 1: Photoconductor (object to be charged) 2: Charging device 6: Developing device 10: Magnetic brush 11: Magnetic particles 15: Sensor (toner density detecting means) 20: Magnetic particle cleaning device 21: Cleaning member 25: Mode selection key ( Mode selection means) 31: toner recirculation conveyance path 50: control device

Claims (6)

[Claims] 1. A charging device for charging a body to be charged by applying a charging bias to the magnetic brush in a state where the magnetic brush having a brush portion formed by magnetic particles is in contact with the body to be charged. The image forming apparatus according to claim 1, further comprising a magnetic particle cleaning device disposed adjacent to the magnetic brush and configured to remove toner attached to the magnetic particles by applying a voltage. 2. A toner density detecting means for detecting the density of toner present in a portion of the magnetic brush,
2. The image forming apparatus according to claim 1, further comprising an applied voltage changing unit configured to change a voltage applied to the magnetic particle cleaning device according to a toner concentration detected by the toner concentration detecting unit. 3. The applied voltage changing means changes a voltage applied to the magnetic particle cleaning device according to a toner concentration detected by the toner density detecting means, and also changes a charging bias applied to the magnetic brush. 3. An image forming apparatus according to claim 2, wherein the image forming apparatus is a means for causing the image forming apparatus to execute the operation. 4. The image forming apparatus according to claim 1, wherein a voltage is applied to the magnetic particle cleaning device to remove a toner attached to the magnetic particles. An image forming apparatus, comprising: a mode selection unit for selecting a mode to be performed also during image formation. 5. The image forming apparatus according to claim 1, wherein the cleaning member of the magnetic particle cleaning device has a roller shape. 6. The image forming apparatus according to claim 1, further comprising a toner recirculation conveyance path for recirculating the toner collected by the magnetic particle cleaning device to a developing device. Image forming device.