JP2003076243A - Image forming apparatus and cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which toner is restrained from being discharged every time one cycle of image formation is carried out without changing a structure of the conventional image forming apparatus drastically and to provide a cleaning method. SOLUTION: This image forming apparatus is provided with a photoreceptor, an electrifying means for electrifying the photoreceptor, an exposing means for exposing the electrified photoreceptor to form a latent image on the surface of the electrified photoreceptor, a developing means for sticking toner to the formed latent image to form a toner image on the surface of the photoreceptor, a transferring means for transferring the toner image formed on the photoreceptor to a transfer medium and a cleaning unit for removing the toner remaining on the surface of the photoreceptor after the toner image is transferred. The cleaning unit is provided with an electrically conductive brush rotating while being in contact with the surface of the photoreceptor for removing the toner and an electrical potential keeping means for keeping the electrical potential of the electrically conductive brush higher than that of the surface of the photoreceptor.

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 and a cleaning method, and in particular, in an image forming apparatus to which an electrophotographic technique is applied, even if the process speed is high, the residual toner transferred onto a transfer medium is completely removed. The present invention relates to an image recording apparatus that does not cause poor cleaning that remains on the surface of a photoconductor without being removed, and a cleaning method that can be suitably used in the image forming apparatus.

[0002]

2. Description of the Related Art Electrophotographic copying machines, laser printers,
In an image forming apparatus such as a copying machine such as a facsimile and an electrostatic recording device, a rotating photosensitive member is charged by a charger and then exposed by a writing unit to form an electrostatic latent image. Is developed by developing means to form a toner image. Then, the toner image is transferred to a transfer medium such as recording paper directly or through an intermediate transfer member, and the transferred toner image is fixed by a fixing device to form an image. On the other hand, the so-called transfer residual toner remaining on the photoconductor without being transferred is removed by the cleaning device, and the process proceeds to a new image forming process.

The cleaning device for removing the residual toner after transfer includes a blade cleaning device for mechanically removing the toner by a blade which is a plate-like member formed of elastic rubber, and a cleaning fur brush constructed in a roll shape. An electrostatic brush (ES that electrostatically scrapes the transfer residual toner on the photoconductor with this fur brush by applying a voltage
B) There is a cleaning device, etc. (Japanese Patent Laid-Open No. 60-101)
575, JP-A-63-249183).

The blade cleaning device is very simple in construction, low in cost, and does not require a large space. However, there is a problem that the cleaning performance is insufficient in a color machine or a medium speed machine or the like having a high image density.

On the other hand, the ESB cleaning device has a very high initial cleaning performance, but since the cleaning performance is rapidly lowered when the brush is contaminated with toner or the like, in order to properly remove the toner or the like from the brush,
Auxiliary means such as a metal roll (detoning roll) installed in contact with the brush is required. Further, since a bias voltage must be applied to the brush and the detoning roll, a plurality of power supplies are required, resulting in high cost and many devices required, which is not suitable for downsizing (Japanese Patent Publication No. -60148).

Therefore, the ESB cleaning device is
In reality, except for some high-speed machines, it is rarely used.

Therefore, in the most versatile medium speed machine having a process speed of 150 to 250 mm / sec, a blade / brush cleaning device using a blade as a main cleaning means and a brush as an auxiliary means is often adopted. .

In the above-mentioned blade / brush cleaning device, the brush is usually of an insulating or semi-insulating type. The brush is used as a member that simply disturbs the toner without applying a bias voltage to weaken the adhesion between the photoconductor and the toner, or an auxiliary member that conveys the collected toner to the collecting path.

Therefore, in the above-mentioned system, the brush actually does not function as a cleaner for removing toner, so that a high speed machine having a process speed higher than a certain level or a spherical shape having poor blade cleaning property. The device using the toner is still insufficient in cleaning property and is apt to cause poor cleaning.

Therefore, as a method of enhancing the toner cleaning effect without applying a bias voltage to the brush, a method of using a conductive material for the brush and installing one end thereof has been adopted.

According to this method, the same effect as that of the above-mentioned ESB cleaning device can be obtained, and the toner can be electrostatically collected to some extent by the brush.

FIG. 5 and FIG. 6 show an example of an image forming apparatus using the cleaning device.

As shown in FIGS. 5 and 6, the photosensitive drum A, which is a drum-shaped photosensitive member, is rotationally driven around the axis by the motor and uniformly charged to minus several hundred volts by the corotron B. , Is exposed by the exposure optical system C to form an electrostatic latent image. The latent image is the developing device D.
To develop a toner image.

The toner image on the photosensitive drum A is transferred to the intermediate transfer body G and finally transferred to the transfer paper P by being given a positive charge by the transfer roller F to which a positive voltage is applied. The transfer paper P on which the toner image is transferred passes through the fixing device J, or the second transfer means H and then the fixing device J, whereby the toner image is fixed on the fixing paper P. To do.

On the other hand, the photosensitive drum A, after transferring the toner image to the intermediate transfer member G, passes near the pre-cleaning corotron K and then passes through the cleaning device E. The cleaning device E includes a conductive brush E1 whose one end is grounded and a cleaning blade E2.

The photosensitive drum A is destaticized by the precleaning corotron K. When the photosensitive drum A passes through the cleaning device E, a part of the transfer residual toner that has not been transferred to the intermediate transfer body G is electrostatically collected by the conductive brush E1 and the rest is transferred by the blade E2 to the photosensitive drum A. Are removed from the surface of.

[0017]

In the above image forming apparatus, the image forming operation of forming a latent image on the surface of the photosensitive drum A and then developing the latent image with toner to form a toner image is completed. After that, when the photosensitive drum A idles (cycles out) until a series of operations for transferring the image to the intermediate transfer member 7 and then transferring and fixing the image on the transfer paper P is completed, the conductive brush E1 is placed in the conductive brush E1. In some cases, the toner that has been trapped is instantaneously discharged onto the photosensitive drum A, and toner is ejected.

The toner ejection is performed by transferring the toner image,
When the photosensitive drum A is discharged and the potential becomes near zero, the electric field generated between the conductive brush E1 and the photosensitive drum A, which are slightly negatively charged, causes the toner in the conductive brush to be transferred onto the photosensitive drum A. It is considered to be caused by electrostatically moving all at once.

Therefore, it is considered that the toner discharge can be reduced by appropriately returning or removing the toner accumulated on the conductive brush E1 onto the photosensitive drum A even during image formation on the photosensitive drum A.

However, since the toner in the conductive brush E1 is electrostatically attached to the conductive brush E1, it is difficult to remove the toner by a mechanical means such as a flicker bar.

Therefore, in order to remove the toner from the conductive brush E1, it is necessary to use a new device such as the detoning roll used in the ESB cleaning device.

In consideration of the above problems, the present invention effectively utilizes the cleaning effect of the conductive brush without making a large change to the conventional image forming apparatus to increase the cost and space, and further, the toner at the time of cycle out. An object of the present invention is to provide an image forming apparatus and a cleaning method capable of suppressing the occurrence of poor cleaning due to ejection.

[0023]

According to a first aspect of the present invention, there is provided a photoconductor, a charging unit for charging the photoconductor, and an exposing unit for exposing the charged photoconductor to form a latent image on the surface. Developing means for forming a toner image on the surface of the photoconductor by attaching toner to the latent image, transfer means for transferring the toner image formed on the photoconductor to a transfer medium, and transfer of the toner image An image forming apparatus comprising: a cleaning device for removing toner remaining on the surface of the photoconductor later, wherein the cleaning device has conductivity and is in contact with the surface of the photoconductor. The present invention relates to an image forming apparatus comprising: a conductive brush that rotates while rotating to remove the toner; and a potential holding unit that holds the conductive brush at a potential higher than the surface of the photoconductor.

In the image forming apparatus, at the time of removing the toner, in other words, at the time of cleaning, the potential of the conductive brush is held at a higher potential than the surface of the photoconductor by the potential holding means. To be done.

As described above, in the image forming apparatus, the transfer residual toner is negatively charged and then removed by the cleaning device. Therefore, the transfer residual toner is sucked by the conductive brush. It

Therefore, since the toner discharge during the cleaning is effectively prevented, the poor cleaning in which the surface of the photosensitive member is re-contaminated by the toner discharge is effectively prevented.

Examples of the image forming apparatus include image recording apparatuses to which electrostatic photography technology is applied, such as electrophotographic copying machines, laser printers, and electrostatic recording apparatuses.

The conductive brush has 10 brush bristles.
A roller-shaped brush having an electric resistance of about ² to 10 ⁴ Ω can be mentioned. Specifically, from a blended product of conductive fibers such as carbon fibers described later and non-conductive fibers such as synthetic fibers such as polyamide fibers Or a roller-like brush in which brush bristles made of a conductive resin obtained by kneading conductive particles such as carbon black in a synthetic resin such as the above polyamide are planted on a metal shaft.

When the brush bristles have a thickness of about 1 to 100 denier, a sufficient cleaning effect can be obtained, and
It is preferable because the surface of the photoreceptor is not damaged.

The potential holding means may be, for example, a ground circuit in which a resistor described later is inserted. Other examples include a voltage application circuit that applies a predetermined voltage higher than the surface of the photoconductor to the conductive brush.

According to a second aspect of the present invention, the cleaning device is located on the downstream side of the conductive brush along the rotation direction of the photoconductor, and the tip of the cleaning device is in the shape of a plate. The present invention relates to an image forming apparatus including a cleaning blade that is an elastic member.

In the image forming apparatus, the transfer residual toner not removed by the conductive brush is scraped off from the surface of the photoconductor by the cleaning blade.

Therefore, the image forming apparatus has a feature that the transfer residual toner can be removed more reliably.

The cleaning blade can be formed of an elastomer, a conductive elastomer in which conductive particles such as carbon black are mixed with the elastomer, or a metal.

According to a third aspect of the present invention, the potential holding means is a ground circuit in which one end is connected to the conductive brush, the other end is grounded, and a resistor is interposed. Regarding

In the image forming apparatus, the shape factor SF1 is 1 in spite of the simple structure of the potential holding means.
It has a feature that a high poor cleaning prevention effect can be obtained even when a toner having a sphericity close to 00 is used.

The fifth aspect of the present invention relates to an image forming apparatus in which the resistor provided in the ground circuit has a resistance value of 10 ⁷ to 10 ⁹ Ω.

In the image forming apparatus, a higher poor cleaning prevention effect can be achieved.

The invention according to claim 5 relates to an image forming apparatus, wherein the conductive brush comprises a metal shaft and brush bristles embedded in the metal shaft.

In the image forming apparatus, one end of the ground circuit according to claim 3 is connected to the metal shaft provided in the conductive brush, so that the potential of the conductive brush is kept higher than that of the photoconductor. it can.

The invention according to claim 6 relates to an image forming apparatus, wherein the brush bristles provided in the conductive brush are conductive fiber-blended brush bristles mixed with conductive fibers.

Since the brush bristles have an appropriate electric resistance of 10 ² to 10 ⁴ Ω, according to the image forming apparatus, a particularly high poor cleaning preventing effect can be obtained.

The seventh aspect of the present invention relates to an image forming apparatus, wherein the conductive fiber is carbon fiber.

The cleaning device is an example in which carbon fibers are mixed-spun as the conductive fiber-blended brush bristles planted in the conductive brush in the cleaning device according to the sixth aspect.

Since the conductive fiber-blended brush bristles in which carbon fibers are mixed-spun as the conductive fibers have high flexibility, the surface of the photoreceptor is not particularly damaged.

The invention described in claim 8 relates to an image forming apparatus in which the cleaning blade is formed of an elastomer.

The cleaning blade is soft,
Moreover, since it has elasticity, in the image forming apparatus, a high toner scraping effect is obtained, and the surface of the photoconductor is not damaged.

As the elastomer, various thermoplastic or thermosetting elastomers such as urethane type elastomer, polyester type elastomer, polyolefin type elastomer, polyamide type elastomer and epoxy type elastomer can be used, but the hardness can be easily adjusted. The urethane elastomer is preferable from the viewpoint that a wide range of physical properties can be obtained.

Other examples of the elastomer include conductive elastomers obtained by blending the thermoplastic or thermosetting elastomer with conductive particles such as carbon black to give conductivity.

The invention according to claim 9 relates to an image forming apparatus in which the shape factor SF1 of the toner is 100 to 140.

Since the toner having a shape factor SF1 of 100 to 140 used in the image forming apparatus has a high sphericity, it has a particularly high sharpness, and an image faithfully reproducing the gradation of the original can be obtained. Further, in the case of a color image, the vividness of colors is also excellent.

The invention described in claim 10 relates to an image forming apparatus, wherein a process speed, which is a speed at which the transfer means transfers the toner image onto the recording paper, is 150 to 250 mm / sec.

The process speed of the image forming apparatus is a general one as a medium speed machine.

According to an eleventh aspect of the present invention, a photoconductor, a charging unit that charges the photoconductor, an exposing unit that exposes the photoconductor after charging to form a latent image on the surface, and Image formation including a developing unit that adheres toner to the latent image formed on the surface to form a toner image on the surface of the photoconductor, and a transfer unit that transfers the toner image formed on the photoconductor to a transfer medium. In the apparatus, a cleaning method for removing toner remaining on the surface of the photoreceptor after the transfer of the toner image, wherein a conductive brush having conductivity,
The present invention relates to a cleaning method, wherein the toner is removed by bringing the toner into contact with the surface of the photoconductor and rotating the photoconductor while maintaining the potential higher than that of the surface of the photoconductor.

In the cleaning method as well, for the same reason as described in claim 1, toner discharge from the conductive brush does not occur during cleaning. Therefore, the occurrence of poor cleaning in the image forming apparatus is effective. Can be prevented.

[0056]

BEST MODE FOR CARRYING OUT THE INVENTION 1. First Embodiment FIG. 1 shows a schematic configuration of an image forming unit which is an example of an image forming apparatus according to the present invention. The image forming unit is used in electrophotographic copying machines, laser printers, electrostatic recording devices, and the like.

As shown in FIG. 1, the image forming unit 100 according to the first embodiment includes a photosensitive drum 1 which rotates clockwise in FIG. 1 as indicated by an arrow a in FIG.
And a corotron 2 provided diagonally above the photosensitive drum 1 and facing the photosensitive drum 1 to negatively charge the surface of the photosensitive drum 1, and the photosensitive drum 1 charged by the corotron 2.
Write the image to be formed with toner on the surface of the
An exposure device 3 that forms a latent image, and a developing device 4 that is provided downstream of the exposure device 3 and that attaches toner to the latent image formed by the exposure device 3 to form a toner image on the surface of the photosensitive drum 1. , While contacting the photosensitive drum 1, the arrow b in FIG.
While running in the direction indicated by, the surface of the photosensitive drum 1 is erased by removing the endless belt-shaped transfer belt 7 that transfers the toner image formed on the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1 after the toner image is transferred to the transfer belt 7. And pre-cleaning corotron 1 that facilitates removal of transfer residual toner remaining on the surface
0, and a cleaning device 5 for cleaning the surface of the photosensitive drum 1 to remove the transfer residual toner.

Corotron 2, exposure device 3, developing device 4,
The transfer belt 7, the pre-cleaning corotron 10, and the cleaning device 5 are arranged in a clockwise direction in FIG. 1 on the circumference surrounding the photosensitive drum 1. The corotron 2, the exposure device 3, the developing device 4, and the transfer belt 7 correspond to a charging unit, an exposing unit, a developing unit, and a transferring unit in the image forming apparatus according to the present invention, and in particular, the transfer belt 7 is It corresponds to an intermediate transfer member in the image forming apparatus.

In the developing device 4, as shown in FIG. 1, yellow (Y) toner is attached to the surface of the photosensitive drum 1 to form a yellow toner image (hereinafter referred to as "Y image").
And a Y image forming unit 4Y for forming a magenta color toner image (hereinafter, referred to as “M”).
Image. ), A C image forming section 4C for forming a cyan toner image (hereinafter referred to as “C image”) by adhering cyan (C) toner, and a black toner. And a Bk image forming unit 4B that forms a black toner image (hereinafter, referred to as “Bk image”) by being attached to each other in a circumferential direction along the counterclockwise direction in FIG.

The transfer belt 7 is formed from the inside by the conveying roller 1.
Tensioned and held by 3A, 13B, 13C and 13D and driven in the direction of arrow b.
A primary transfer roller 6 for charging the transfer belt 7 positively and adsorbing the toner on the photosensitive drum 1 to the outer surface of the transfer belt 7 is provided at a position inside the transfer belt 7 facing the photosensitive drum 1. ing. The recording paper P is positively charged outside the transfer belt 7 below the transfer belt 7
A secondary transfer roller 9 is provided that transfers the toner image formed on the transfer belt 7 onto the recording paper P by pressing it to.

Below the transfer belt 7, a recording paper supply device 12 for supplying the recording paper P to the secondary transfer roller 9 is further provided.
And a fixing device 8 for fixing the toner image while conveying the recording paper P on which the toner image is formed on the secondary transfer roller 9.

The recording paper supply device 12 includes a pair of conveying rollers 12A and two recording papers P conveyed by the conveying rollers 12A.
Induction slope 12B that guides toward the next transfer roller 9
With. On the other hand, the fixing device 8 heats and presses the recording paper P on which the toner image is transferred by the secondary transfer roller 9 to fix the toner image, and a fixing roller 8A, which is a pair of heat rollers, and a fixing roller. It has a conveyor 8B for conveying the recording paper P toward the roller 8A.

The recording paper P is indicated by an arrow c in FIG. 1 by the recording paper supply device 12, the secondary transfer roller 9 and the fixing device 8.
It is conveyed in the direction indicated by.

In the vicinity of the transfer belt 7, there is further provided an intermediate transfer member cleaning device 11 for removing the toner remaining on the transfer belt 7 after the toner image is transferred onto the recording paper P by the secondary transfer roller 9. .

The details of the structure of the cleaning device 5 are shown in FIG.

As shown in FIGS. 1 and 3, the cleaning device 5 has brush densities having a thickness of 10 denier and made of a blended product of carbon fiber and polyamide. The brush bristles contact the surface of the photosensitive drum 1. 1 and 3, the conductive brush 52 that rotates in the direction indicated by the arrow d in FIG. 1 and FIG. 3 to remove the transfer residual toner on the photosensitive drum 1 and the photosensitive drum 1
The cleaning blade 51 made of urethane elastomer, which is adjacent to the upstream side of the conductive brush 52 with respect to the rotation direction a, removes transfer residual toner that could not be completely removed by the conductive brush 52 from the surface of the photosensitive drum 1 by scraping. A flicker bar 53 that repels the brush bristles of the conductive brush 52 to remove transfer residual toner that has entered between the brush bristles from the brush bristles; and a housing 55 that houses the conductive brush 52 and the flicker bar 53. Prepare The housing 55 is
The cleaning blade 51 has an opening that opens toward the photosensitive drum 1, and forms the upper edge of the opening.

An auger 54 is provided at the bottom of the housing 55 in the horizontal direction and guides the transfer residual toner removed by the cleaning blade 51 and the conductive brush to the outside of the housing 55.

The conductive brush 52 is connected to a ground circuit 56 whose other end is grounded. A resistor R is interposed in the ground circuit 56. The resistance value of the resistor R is preferably about 10 ⁷ to 10 ⁹ Ω as described later.

The operation of the image forming unit 100 will be described below by taking the case of forming a color image as an example.

The photosensitive drum 1 rotates in the direction indicated by the arrow a, and at the same time, is negatively charged by the corotron 2.

The photosensitive drum 1 whose surface is negatively charged by the corotron 2 is exposed by the exposure device 3 to form a latent image on the surface.

When the portion of the photosensitive drum 1 on which the latent image is formed approaches the electrographic device 4, the electrographic device 4 moves to the position shown in FIG.
As shown in, the Y image forming unit 4Y rotates to a position where it abuts on the photosensitive drum 1. Therefore, when the photosensitive drum 1 rotates and the portion of the photosensitive drum 1 faces the developing unit 4, yellow toner adheres to the latent image and a Y image is formed.

When the photosensitive drum 1 on which the Y image is formed is further rotated 1/4 in the direction of arrow a, the Y image is
The image is transferred to the outer surface of the transfer belt 7.

After the transfer, the photosensitive drum 1 is destaticized by the precleaning corotron 10, and the cleaning device 5 removes the yellow toner remaining on the surface.

The photosensitive drum 1 from which the yellow toner remaining after transfer is removed by the cleaning device 5 is again negatively charged by the corotron 2 and is exposed by the exposure device 3 to form a latent image.

After the latent image is formed, when the portion of the photosensitive drum 1 on which the latent image is formed approaches the electrographic device 4,
This time, the image device 4 makes a quarter turn in the clockwise direction from the state shown in FIG. 1, and the M image forming portion 4M comes to a position where it abuts on the photosensitive drum 1. Therefore, when the photosensitive drum 1 rotates and the portion of the photosensitive drum 1 faces the developing unit 4, magenta toner adheres to the latent image, and an M image is formed.

When the photosensitive drum 1 on which the M image has been formed is further rotated a quarter turn in the direction of arrow a, the toner image is transferred to the outer surface of the transfer belt 7.

Therefore, since the M image on the photosensitive drum is located on the Y image on the transfer belt 7, the M image in the previous period is transferred onto the Y image.

After the magenta toner on the surface of the photosensitive drum 1 is transferred to the transfer belt 7, the precleaning corotron 10 removes the charge, and the cleaning device 5 removes the magenta toner remaining on the surface.

Next, a C image is formed on the surface of the photosensitive drum 1, and the Y image and the M image on the transfer belt 7 are formed.
The Bk image is transferred over the image, and the Bk image is also transferred over the C image on the transfer belt 7 formed on the surface of the photosensitive drum 1.

The Y image, M image, C image, and Bk
When the image is transferred to the transfer belt 7, the recording paper feeding device 1
2, the recording paper P is supplied to the secondary transfer roller 9, and the Y image, the M image, and the C image which are transferred and superposed on the transfer belt 7 are transferred.
The image and the Bk image are transferred onto the recording paper P by the secondary transfer roller 9. As a result, a color image is formed on the recording paper P.

The color image is fixed on the recording paper P on which the color image is formed by the fixing device 8.

In the image forming unit 100, the relative potentials of the rotating shaft of the conductive brush 52, the resistor 57, the conductive brush 52, and the surface of the photosensitive drum 1 are shown in FIG. In FIG. 4, (A) shows a relative relationship of the potentials of the respective portions when the Y image, the M image, the C image, and the Bk image are formed on the surface of the photosensitive drum 1,
(B) shows the relative relationship of the electric potentials after the Y image, the M image, the C image, and the Bk image are transferred to the transfer belt 7, that is, at the time of cycle out.

As shown in FIG. 4A, the Y
During image formation in which an image or the like is formed on the surface of the photosensitive drum 1, the potential of the conductive brush 52 is higher than the potential of the surface of the photosensitive drum 1.

As shown in FIG. 4B, the potential of the conductive brush 52 is kept higher than the potential of the surface of the photosensitive drum 1 by the resistor R even at the time of cycle out.

Since the toner is negatively charged and therefore tries to move to a higher potential, the toner is not attracted to the conductive brush 52 and the toner is not discharged from the conductive brush 52.

In the image forming unit according to the first embodiment, even when an image is formed on the recording paper P at a high process speed by using toner having a high sphericity, the toner is not ejected from the conductive brush 52. .

Therefore, poor cleaning does not occur on the surface of the photosensitive drum 1, and the surface on the downstream side of the cleaning device 5 is sufficiently cleaned, so that the surface of the recording paper P is soiled by the transfer residual toner. Never. Even when a color image is formed, a clear image can be obtained because the transfer residual toner does not cause color mixing.

2. Embodiment 2 FIG. 2 shows a schematic configuration of another example of the image forming unit included in the image forming apparatus according to the present invention. The image forming unit is also used in electrophotographic copying machines, laser printers, electrostatic recording devices and the like. 2, the same reference numerals as those in FIG. 1 denote the same elements as those shown in FIG.

As shown in FIG. 2, in the image forming unit according to the second embodiment, the transfer drum 14 is provided below the photosensitive drum 1 so as to be separable from and in contact with it.

The transfer drum 14 electrostatically adsorbs the recording paper on its outer surface and rotates in the counterclockwise direction as indicated by an arrow e in FIG. It has a function of transferring the toner image formed on the surface of the recording paper to the recording paper.

On the upstream side of the photosensitive drum 1 along the rotation direction e, there is provided a recording paper supply device 22 including a group of rollers for supplying the recording paper to the outer surface of the transfer drum 14.

On the other hand, a recording paper peeling device 24 for peeling the recording paper from the outer surface of the transfer drum 14 is provided downstream of the photosensitive drum 1 in the rotation direction e in the vicinity of the transfer drum 14. .

The recording paper peeling device 24 is provided downstream of the charge eliminating corotron 24A along the rotation direction e with respect to the charge eliminating corotron 24A, which makes it easier to remove the charge from the surface of the transfer drum 14 by removing the charge from the recording paper. A peeling claw 24B for peeling the recording paper from the surface of 14 and a pair of heat rollers 24C for heating the recording paper peeled by the peeling claw 24B to thermally fix the toner image.

A charging corotron 16 for charging the transfer drum 14 positively and adsorbing the recording paper is provided inside the transfer drum 14 at a position facing the recording paper supply device 22. Then, at a position inside the transfer drum 14 facing the photosensitive drum 1, the recording paper adsorbed on the surface of the transfer drum 14 is further positively charged, and the toner image on the surface of the photosensitive drum 1 is transferred to the recording paper. A transfer corotron 18 is provided. Further, a transfer drum charge-removing corotron 20 for removing charge from the transfer drum 14 is provided inside and outside the transfer drum 14 on the downstream side of the recording paper peeling device 24 along the rotation direction e.

The image forming unit 102 has the same structure as the image forming unit 100 according to the embodiment except for the above points.

The operation of the image forming unit 102 will be described below by taking the case of forming a color image as an example.

Image forming unit 100 according to the first embodiment
Similarly, in the image forming unit 102, the photosensitive drum 1 whose surface is negatively charged by the corotron 2 is exposed by the exposure device 3 to form a latent image on the surface of the photosensitive drum 1.

When the portion of the photosensitive drum 1 on which the latent image corresponding to the Y image is formed approaches the electronic image device 4, the electronic image device 4 causes the Y image forming portion 4Y to move to the photosensitive drum 1 as shown in FIG. To the position where it abuts against the surface of the photosensitive drum 1. As a result, yellow toner adheres to the latent image on the surface of the photosensitive drum 1 to form a Y image.

When the photosensitive drum 1 on which the Y image is formed rotates along the direction of arrow a, and the portion of the photosensitive drum 1 on which the Y image is formed approaches the transfer corotron 18, the transfer drum 14 becomes While contacting the photosensitive drum 1, the photosensitive drum 1 rotates at the same peripheral speed as the photosensitive drum 1.

At the same time, the transfer drum 14 is positively charged by the charging corotron 16 and electrostatically attracts the recording paper supplied by the recording paper supply device 22.

The recording paper is conveyed toward the photosensitive drum 1 by the transfer drum 14 and is sandwiched between the photosensitive drum 1 and the transfer drum 14, and at the same time, is strongly positively charged by the transfer corotron 18. . Therefore, the negatively charged toner on the surface of the photosensitive drum 1 is transferred to the recording paper by the mechanical pressure and the electrostatic attraction. This allows
The Y image on the surface of the photosensitive drum 1 is transferred to the recording paper.

After the Y image is transferred onto the recording paper, the transfer drum 14 is separated from the photosensitive drum 1 and continues to rotate at the same angular velocity as the photosensitive drum.

The photosensitive drum 1 after transfer of the toner image is
As in the case of the image forming unit 100 according to the first embodiment, static electricity is removed by the precleaning corotron 10.
In the cleaning device 5, the yellow toner remaining on the surface is removed.

The photosensitive drum 1 from which the yellow toner remaining after transfer has been removed in the cleaning device 5 is again negatively charged by the corotron 2, and in the exposure device 3 in the future, a new latent image corresponding to the M image is formed. Is formed.

The M image transferred to the surface is transferred to the recording paper in the same manner as described for the Y image.

Here, since the transfer drum 14 makes exactly one rotation while the recording paper on which the Y image is formed is adsorbed on the surface, the M image is transferred onto the Y image.

Similarly, a C image and a Bk image are formed on the surface of the photosensitive drum 1, and the Y image transferred onto the recording paper is obtained.
Transferred onto image and M image.

The transfer drum 14 rotates four times, and the Y image,
When all of the M image, the C image, and the Bk image are transferred to the recording paper, the recording paper is discharged by the discharging corotron 24A, and as shown by the arrow e in FIG.
By B, it is separated from the surface of the transfer drum 14 and passes between the fixing rollers 24C. Thereby, the Y image,
The M image, C image, and Bk image are fixed on the recording paper.

In the image forming unit 102, the relative potentials of the rotating shaft of the conductive brush 52, the resistor 57, the conductive brush 52, and the surface of the photosensitive drum 1 are the same as those in the image forming unit 100 according to the first embodiment. Similarly, it is as shown in FIG.

Therefore, even at the time of cycle out, the potential of the conductive brush 52 is kept higher than the potential of the surface of the photosensitive drum 1 by the resistor R, so that the toner is not discharged from the conductive brush 52. .

Image forming unit 102 according to the second embodiment
In addition to the same features as the image forming unit according to the first embodiment, the transfer drum 14 is more compact than the transfer belt 7 according to the first embodiment, and thus is more compact than the image forming unit according to the first embodiment. It has the feature that it can be configured into.

[0113]

EXAMPLES (Example 1, Comparative Example 1) In the image forming unit shown in FIG. 1, the photosensitive drum 1 has a diameter of 84 mm.
The columnar base is made of aluminum, contains a polymer resin / triphenylamine type charge transfer agent on the surface of a columnar base, contains polycarbonate as a binder, and is an organic material having sensitivity in the infrared region. The thing which formed the photosensitive layer which consists of a photoreceptor was used.

In the scorotron 2, the wire is -5
A DC voltage of kV was applied and a DC voltage of -750v was applied to the grid to charge the surface of the photosensitive drum 1 to -700V.

A latent image was formed on the charged surface of the photosensitive drum 1 by the exposure device 3, and then a negatively charged toner was attached to the latent image in the developing device 4 to form a toner image.

The toner image is transferred onto the surface of the transfer belt 7 by the primary transfer roller 6, and then the toner image is transferred onto the recording paper P by the secondary transfer roller 9 and fixed by the fixing device 8. .

The color image is formed at a process speed of 220 mm / s in the image forming unit 100.
It was fixed at ec.

In the cleaning device 5, the cleaning blade 51 made of urethane elastomer is
With a contact angle of 1.5 g / mm at an installation angle of 1 degree.
It was attached to the housing 55 so as to abut the surface of the.

Also in the intermediate transfer member cleaning device 11, the blade is made of urethane elastomer, the installation angle is 17 degrees, and the contact pressure on the transfer belt 7 is 2.2 g /
It was provided so as to be mm.

Conductive brush 5 in cleaning device 5
As No. 2, a brush shaft made of a blended product of carbon fiber and nylon was planted on a metal shaft. The electric resistance of the conductive brush 52 was 10 ² to 10 ⁴ Ω, and the thickness of the brush bristles was 10 denier.

A ground circuit 56 was connected to the metal shaft of the conductive brush 52.

When the resistor R is not inserted in the ground circuit 56 (Comparative Example 1), and the resistor R is inserted in the ground circuit 56, the resistance value thereof is in the range of 10 ³ to 10 ¹² Ω. In the case of changing (Example 1), the toner cleaning property, the presence / absence of toner discharge, the size, and the presence / absence of poor cleaning were evaluated.

As the toner, a toner having a shape factor SF1 = 120 manufactured by a polymerization method was used.

Here, the shape factor SF1 was obtained as follows.

First, the toner for which the shape factor SF1 is to be measured was photographed with a microscope or an electron microscope.

From the micrograph of the obtained toner, 100 toner images were randomly extracted. Next, the absolute maximum length MXLNG is calculated for the toner image, and the following formula is used: SF1 = (MXLNG) ² / AREA × (4 / π) × 1
00, the shape factor SF1 was obtained.

Here, "AREA" is the projected area of the toner in the micrograph of the toner.

As the shape factor SF1 is closer to 100, the toner is closer to a sphere, and if it is larger than 100, the shape of the toner is oblong or irregular. .

The toner cleaning properties, the presence / absence of ejection, the size, and the presence / absence of poor cleaning were evaluated by the following procedures.

YMCK 4 colors 70% for each halftone (2 in total)
80% of the untransferred image is A3 for 2 sheets cleaning device 5
To shut down the electrophotographic copying machine at the time of cycle out. The amount of toner rushing into the conductive brush 52 at this time was about 800 mg, and most of it was once electrostatically adsorbed to the conductive brush 52.

Then, the presence or absence of the adsorption was visually evaluated to evaluate the toner cleaning property.

Next, at the time of cycle-out, the amount of toner adsorbed by the conductive brush 52 on the surface of the photosensitive drum 1 was visually evaluated to evaluate the presence / absence of toner ejection and the size thereof.

Finally, the amount of toner that had slipped through the cleaning blade 51 and remained on the surface of the photosensitive drum 1 was visually evaluated to determine whether poor cleaning occurred.

The following Table 1 shows the toner cleaning property, the presence / absence of ejection, the size, and the presence / absence of poor cleaning.

[0135]

[Table 1] As shown in Table 1, it was found that the discharge amount decreased as the resistance value of the resistor R increased. On the other hand, under the conditions of Example 1 and Comparative Example 1, when the resistance value of the resistor R is 10 ¹⁰ Ω or more, the conductive brush 52 approaches the float state and the toner collecting force decreases, so that the cleaning function may be lost. all right.

The resistance value of the resistance value R is 10 ⁷ Ω
It was found that 10 ⁹ Ω was the optimum range.

Next, in the first embodiment, the resistance value of the resistor R is fixed at 10 ⁸ Ω, and the shape factor SF1 of the toner used is 120, 130. Then, the presence or absence of poor cleaning was evaluated when the temperature was changed to three levels of 145 and 145. The results are shown in Table 2.

[0138]

[Table 2] Furthermore, the process speed is 100 mm / sec to 320 m
The presence / absence of poor cleaning when changed in the range of / sec was evaluated. The results are shown in Table 3.

[0139]

[Table 3] As shown in Table 3, Comparative Example 1 in which the resistor R was not used
In the above, when the process speed was 150 mm / sec or more, poor cleaning occurred.

On the other hand, in the first embodiment, the resistor R
When the resistance value was set to 10 ⁸ Ω, no poor cleaning was observed even when the process speed was 320 mm / sec.

[0141]

As described above, according to the present invention,
A cleaning device capable of effectively utilizing the cleaning effect of the conductive brush without significantly changing the conventional image forming apparatus to increase the cost or the space, and further suppressing the occurrence of poor cleaning due to toner discharge at the time of cycle-out. An image forming apparatus including a cleaning device is provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of a configuration of an image forming unit which is an example of an image forming apparatus according to the present invention.

FIG. 2 is a schematic view showing the outline of the configuration of another example of the image forming unit.

FIG. 3 is an enlarged view showing details of a configuration of a cleaning device 5 included in the image forming unit shown in FIGS. 1 and 2.

4 is a graph showing relative potentials at the time of forming a toner image and at the time of cycle out for each part of the image forming unit shown in FIG.

FIG. 5 is a schematic diagram showing a schematic configuration of an example of a conventional image forming apparatus.

FIG. 6 shows another example of a conventional image forming apparatus,
It is the schematic which shows the outline of a structure.

7 is a graph showing relative potentials at the time of forming a toner image and at the time of cycle out for each part of the image forming apparatus shown in FIG.

[Explanation of symbols]

1 photosensitive drum 2 Corotron 3 exposure equipment 4 Developing device 5 Cleaning device 51 cleaning blade 52 Conductive brush 6 Primary transfer roller 7 Transfer belt 8 fixing device 9 Secondary transfer roller 12 Recording paper feeding device 14 Transfer roller 16 charged corotron 18 Transfer Corotron, 20 Static elimination corotron 22 Recording paper feeding device 24 Recording paper peeling device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akihisa Maruyama             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             Co., Ltd. Ebina Office (72) Inventor Noritaka Kuroda             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             Co., Ltd. Ebina Office (72) Inventor Masakazu Takahashi             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             Co., Ltd. Ebina Office (72) Inventor Osamu Handa             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             Co., Ltd. Ebina Office (72) Inventor Yoshiya Manashi             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             Co., Ltd. Ebina Office F-term (reference) 2H005 AA15 DA07                 2H134 GA01 GB02 HB01 HB03 HB13                       HB15 HB18 HB19 HD00 HD05                       KB02 KC10 KD03 KG07 KH01

Claims (11)

[Claims] 1. A photosensitive member, a charging unit for charging the photosensitive member, an exposing unit for exposing the charged photosensitive member to form a latent image on the surface, and a toner for adhering toner to the latent image to form the photosensitive member. Developing means for forming a toner image on the surface of the body, transfer means for transferring the toner image formed on the photoconductor to a transfer medium, and toner remaining on the surface of the photoconductor after the toner image is transferred. An image forming apparatus comprising a cleaning device for removing the toner, wherein the cleaning device has conductivity, and a conductive brush that rotates while contacting the surface of the photoconductor to remove the toner, An image forming apparatus comprising: a potential holding unit that holds the conductive brush at a potential higher than that of the surface of the photoconductor. 2. The cleaning device is located downstream of the conductive brush in a rotation direction of the photoconductor,
The image forming apparatus according to claim 1, further comprising a cleaning blade, which is a plate-shaped elastic member and has a tip portion that abuts on a surface of the photoconductor. 3. The grounding circuit according to claim 1, wherein the potential holding means is a grounding circuit having one end connected to the conductive brush, the other end grounded, and a resistor interposed. The image forming apparatus according to item 1. 4. A resistor provided in the ground circuit has a resistance value of 10 ⁷ to 10 ⁹ Ω.
The image forming apparatus according to claim 1. 5. The image forming apparatus according to claim 1, wherein the conductive brush includes a metal shaft and brush bristles embedded in the metal shaft. 6. The image forming apparatus according to claim 1, wherein the brush bristles provided in the conductive brush are conductive fiber-blended brush bristles obtained by mixing conductive fibers. 7. The image forming apparatus according to claim 6, wherein the conductive fiber is carbon fiber. 8. The image forming apparatus according to claim 1, wherein the cleaning blade is formed of an elastomer. 9. The shape factor SF1 of the toner is 100.
The image forming apparatus according to any one of claims 1 to 8, wherein the image forming apparatus is from 140 to 140. 10. A process speed of 150 to 250 mm /
The image forming apparatus according to claim 1, wherein the image forming apparatus is sec. 11. A photoconductor, a charging unit that charges the photoconductor, an exposing unit that exposes the charged photoconductor to form a latent image on the surface, and a latent image formed on the surface of the photoconductor. In the image forming apparatus, a toner image is formed on the surface of the photoconductor by applying toner to the image forming apparatus, and a transfer unit that transfers the toner image formed on the photoconductor to a transfer medium. A cleaning method for removing toner remaining on the surface of the photoconductor after transfer, comprising: holding a conductive brush having conductivity at a higher potential than the surface of the photoconductor, A cleaning method comprising contacting and rotating to remove the toner.