JP2003241530A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which surely prevents getting dirty of the rear side of a transfer material accompanying the lowering of cleaning ability caused by wrap-around of waste toner to the rear side of a belt cleaning member and prevents the color mixture of a secondary transfer residual toner in an intermediate transfer system. <P>SOLUTION: The image forming apparatus having: a photoreceptor having a toner image formed on its surface; a transportation belt to which the toner image formed on the surface of the photoreceptor is transferred, or which transports a recording medium on which the toner image formed on the surface of the photoreceptor is transferred; and a belt cleaning blade for cleaning the surface of the transporting belt is provided with: a driving means for driving the rotating direction of the transporting belt forward and backward and a control means for controlling driving of the transporting belt. When starting or finishing image formation, the transporting belt is rotated in a direction opposite to that during image formation for a prescribed period. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a toner image on a photoconductor while a conveyor belt is running and transfers the toner image to the conveyor belt or a recording material carried on the conveyor belt to form an image. The obtained image forming apparatus further comprises a cleaning means for cleaning the surface of the conveyor belt.

[0002]

2. Description of the Related Art Conventionally, a plurality of image forming sections are provided, toner images of different colors are formed in the respective image forming sections, and the toner images are sequentially superimposed and transferred onto the same recording material to form a color image. Various image forming apparatuses have been proposed, and among them, a multicolor electrophotographic color copying machine using an endless transfer belt is used for high speed recording.

Various image forming apparatuses of the intermediate transfer type have also been proposed in which a toner image is once transferred onto an intermediate transfer belt and then transferred onto a transfer material to form a color image.

Among these image forming apparatuses, there is used a transfer belt or an intermediate transfer belt in which both ends of a sheet of polycarbonate or the like are joined together, or recently, a seamless (seamless) transfer belt is used. Some of them do, and the life expectancy is increasing.

On such a belt, the fog toner developed on the photosensitive member is transferred onto the belt at a portion between the transfer materials (paper interval), and the fogging toner is rotated along the surface of the belt and finally the belt surface is rotated. Since the back surface of the transfer material may be soiled, and the transfer residue of the secondary transfer for transferring the toner image to the transfer material on the intermediate transfer belt may remain on the intermediate transfer belt, resulting in color mixing at the time of forming the next image. The image forming apparatus includes a belt cleaning device. As one of them, there is known a blade type cleaner that performs cleaning using a rubber blade.

[0006]

However, the above-mentioned conventional image forming apparatus has the following problems.

When waste toner such as fog toner or secondary transfer residual toner accumulates at the edge of the rubber blade in a belt cleaning device that is constantly in contact with the transport belt, the rubber blade removes the waste toner from the surface of the transport belt. It will not be completely cut off, will enter between the rubber blade and the conveyor belt, will wrap around to the backside of the edge of the rubber blade, and adhere to the backside of the blade. When the amount of waste toner adhering to the back of the blade increases, the cleaning toner of the rubber blade is remarkably deteriorated because the waste toner on the back side serves as a spacer between the rubber blade and the conveyor belt, and the waste toner sent to the rubber blade thereafter. Toner sometimes slips through the cleaning section, causing problems such as back stains and color mixing.

Further, with the extension of the life of the conveyor belt, the change of the surface condition of the conveyor belt due to long-term use has become remarkable. Examples of this cause include a filming phenomenon in which toner adheres to the surface of the conveyor belt, and the surface of the conveyor belt is worn due to contact between the conveyor belt and the cleaning member. Due to such a change in the surface condition, the coefficient of friction on the surface of the conveyor belt changes, the load on the surface of the conveyor belt and the member in contact with the conveyor belt increases, and the traveling speed of the conveyor belt becomes unstable during traveling. In some cases, color misregistration or the driving capability of the drive motor may be exceeded, making it impossible to carry.

Further, a cleaning blade or the like for cleaning the surface of the conveyor belt has a problem that when the coefficient of friction of the surface of the conveyor belt increases, the frictional force increases and the roller is rolled up. Therefore, it has been proposed to polish the surface of the conveyor belt and refresh it to keep the surface state of the conveyor belt in the initial state.

In such a case, the surface roughness of the belt is increased by polishing the surface of the conveyor belt.
Further, cleaning of the conveyor belt is strict, and the cleaning blade is easily slid through, the amount of toner that wraps around the back of the cleaning blade is increased, and problems such as back stain are more likely to occur.

Further, in the case of the following constitution, the cleaning blade needs to be attached and detached. For example, in the case where the transfer belt has a seam, the transfer belt cleaning blade edge is caught at the seam, the blade edge is chipped, or chattering occurs, and the cleaning ability is deteriorated. Alternatively, in the case of a one-photoreceptor intermediate transfer system in which a plurality of developing means are provided around one photoconductor, a plurality of toner images are superposed on the intermediate transfer belt and are collectively transferred to a transfer material, the intermediate transfer belt 1 Since the toner images are successively placed on the intermediate transfer belt for each circumference, the intermediate transfer belt cleaning blade cannot be always brought into contact.

When the cleaning blade needs to be attached and detached as described above, if the cleaning blade is repeatedly separated and abutted, waste toner and the like blocked by the blade edge when the cleaning blade is separated from the belt remain. There is a problem that the objects are separated from each other while being attached to the blade edge, and are sandwiched between the cleaning blade and the belt when they come into contact with the belt, which deteriorates the cleaning ability.

The present invention has been made in view of the above problems, and an object of the present invention is to stain the back of a transfer material or an intermediate transfer system due to a decrease in cleaning ability caused by waste toner flowing around the back of a belt cleaning member. An object of the present invention is to provide an image forming apparatus capable of reliably preventing the secondary transfer residual toner from being mixed with each other.

[0014]

In order to achieve the above object, the present invention comprises a photoreceptor having a toner image formed on its surface,
A conveyance belt that conveys a recording material on which the toner image formed on the surface of the photoconductor is transferred or the toner image formed on the surface of the photoconductor is transferred, and a surface of the conveyance belt. An image forming apparatus having a belt cleaning blade for cleaning includes drive means for driving the conveyor belt in the forward and reverse directions of rotation, and control means for controlling the drive of the conveyor belt, at the start or end of image formation. Sometimes, the rotation direction of the conveyor belt is rotated in a direction opposite to that during image formation for a predetermined time.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus according to the present invention, and FIG. 2 is a schematic configuration showing a periphery of a conveyor belt of the image forming apparatus according to the present invention. It is a figure.

In FIGS. 1 and 2, the image forming apparatus according to the present embodiment is a color multiplex transfer apparatus, and the first, second, third and fourth image forming sections Pa, Pb, and P
c, Pd are provided side by side, and cyan, magenta, yellow, and black toner images are sequentially formed through the processes of latent image, development, and transfer.

The image forming portions Pa, Pb, Pc and Pd are respectively dedicated image carriers, in this example, the electrophotographic photosensitive drum 3.
a, 3b, 3c, 3d, and each photosensitive drum 3a, 3
Toner images of respective colors are formed on b, 3c, and 3d. A recording material carrier 130 (hereinafter referred to as a transfer belt 130) is installed adjacent to each of the photosensitive drums 3a, 3b, 3c, 3d, and a toner image of each color formed on each of the photosensitive drums 3a, 3b, 3c, 3d. Are transferred onto the transfer material P carried on the transfer belt 130 and conveyed.

Further, the transfer material P on which the toner images of the respective colors have been transferred is separated from the transfer belt 130 by the separation charging device 32, and the toner images are fixed by heating and pressurizing at the fixing section 9, and then the recording image is formed as an apparatus. It is discharged outside.

Drum chargers 2a, 2b, 2c, 2d are provided on the outer circumferences of the photosensitive drums 3a, 3b, 3c, 3d, respectively.
Exposure devices 113a, 113b, 113c, 113d, developing devices 1a, 1b, 1c, 1d, transfer chargers 24a, 24
b, 24c, 24d and cleaners 4a, 4b, 4c,
4d is provided, and a light source device and a polygon mirror 117 (not shown) are further installed above the device.

The polygon mirror 117 is rotated to scan the laser light emitted from the light source device, the light flux of the scanning light is deflected by the reflection mirror, and the fθ lens is used to form a bus on the photosensitive drums 3a, 3b, 3c, 3d. By condensing and exposing, latent images corresponding to image signals are formed on the photosensitive drums 3a, 3b, 3c, 3d.

The developing devices 1a, 1b, 1c and 1d are filled with a predetermined amount of cyan, magenta, yellow and black toners as a developer by a supply device (not shown). The developing units 1a, 1b, 1c and 1d develop the latent images on the photosensitive drums 3a, 3b, 3c and 3d to visualize them as cyan toner images, magenta toner images, yellow toner images and black toner images. .

The transfer material P is accommodated in the transfer material cassette 10, and from there, a plurality of conveying rollers and registration rollers 12 are provided.
Is supplied to the transfer belt 130 via the
With the transport of 0, the toner is sequentially sent to the transfer portion facing the photosensitive drums 3a, 3b, 3c, 3d.

The transfer belt 130 is made of a sheet of dielectric resin such as a polyethylene terephthalate resin sheet (PET resin), a polyvinylidene fluoride resin sheet, a polyurethane resin sheet, and the like. Either endless or seamless (seamless) belts are used. The transfer roller 13 is driven by the driving roller 13.
0 rotates, the transfer material P is sent out from the registration roller 12 to the transfer belt 130, and the transfer material P is transferred to the first image forming portion P.
It is conveyed toward the transfer portion a. At the same time, the image writing signal is turned on, and an image is formed on the photosensitive drum 3a of the first image forming portion Pa at a certain timing based on the signal.

Then, the transfer charger 24a applies an electric field or an electric charge at the transfer section below the photosensitive drum 3a, so that the toner image of the first color formed on the photosensitive drum 3a is transferred onto the transfer material P. To be done. By this transfer, the transfer material P is firmly held on the transfer belt 130 by the electrostatic attraction force, and is conveyed to the second image forming portion Pb and thereafter.

As the transfer charger 24, a contact charger using a transfer charging member such as a blade, a roller or a brush is used.
The contact charger is ozone-free and resistant to changes in temperature and humidity,
There are advantages such as high image quality.

Image formation and transfer in the second to fourth image forming portions Pb to Pd are performed in the same manner as in the first image forming portion Pa. Next, the transfer material P to which the four color toner images have been transferred is removed from the end of the transfer belt 130 by removing the charge by the separation charger 32 at the downstream portion of the transfer belt 130 in the transport direction to attenuate the electrostatic attraction force. . In particular, in a low humidity environment, the transfer material also dries and its electric resistance increases, so that the electrostatic attraction force with the transfer belt increases and the effect of the separation charging device increases. Normally, the separation charging device charges the transfer material P in a state where the toner image is not fixed, and therefore a non-contact charging device is used.

Further, the transfer belt 13 is located downstream from the position where the transfer material P is separated from the transfer belt 130 in the transfer belt traveling direction.
A transfer belt cleaning blade 20 for cleaning fog toner, scattered toner, etc. adhering to the surface 0 is always in contact with the transfer belt, and a transfer belt cleaning web 19 is provided downstream thereof. Further, a polishing roller 71 is provided downstream thereof to prevent the transfer cleaning blade from curling and the transfer belt filming.
The transfer belt 130 is regularly polished.

Then, the separated transfer material P is conveyed to the fixing device 9, where the toner images are mixed and fixed on the transfer material P by fixing, and a full-color copy image is formed and discharged to the paper discharge tray 63. It

Here, the transfer belt cleaning and sequence according to the present invention will be further described.

The transfer belt cleaning blade 20 is
The transfer belt 130 is sandwiched between the drive roller 13 and the drive roller 13. In the present embodiment, the transfer cleaning blade 20 has a metal base 201 as shown in FIG.
A urethane rubber blade 201 having a thickness t = 2.0 mm was adhered with a free length L = 8 mm, and a nylon coat 203 having a width of 3 mm was applied to the blade edge to prevent the cleaning blade from curling. Also, FIG.
As shown in FIG. 5, the transfer belt cleaning blade 20 is brought into contact with the transfer belt 130 at a contact angle of 20 degrees and a contact pressure of 800 g at the position of the driving roller 6 o'clock, and residuals such as fog toner adhered to the surface of the transfer belt. It is configured to scrape off.

Next, the sequence will be described with reference to FIGS. 4 and 5.
It will be described based on.

When the image forming operation is started, the drive roller 13 of the transfer belt is rotated by the drive motor 131 and the drive motor control means 132 for a predetermined time in the direction b opposite to that at the time of image formation. The rotation time in the rotation direction b is from 6 o'clock (A) to 8 o'clock (B) when the transfer belt cleaning blade contact position of the transfer belt at the start of image formation.
It is time to move to the position. Rotation direction of transfer belt b
When rotating, the transfer belt 130 and the photoconductor 2 are separated from each other. This is to prevent scratches due to the difference in peripheral speed between the transfer belt and the photoconductor.

When the transfer belt rotates in the b direction, the residue that enters between the transfer belt cleaning blade 20 and the transfer belt 130 and wraps around the back side of the transfer belt cleaning blade forms an image from the edge of the transfer belt cleaning blade. At this time, the toner is carried out while being attached to the transfer belt at the upstream portion in the transfer belt rotation direction a. This is due to static friction force and electrostatic force.

After that, the transfer belt 130 rotates in the rotation direction a, and the image forming operation is performed. At this time, since the waste toner that has wrapped around to the back side of the transfer belt cleaning blade 20 and has been the spacer between the transfer belt cleaning blade 20 and the transfer belt 130 is gone, the transfer belt cleaning blade recovers a good cleaning ability. There is. Then, the residue carried out from the back side of the transfer belt cleaning blade is removed at the edge portion of the transfer belt cleaning.

When the transfer belt was cleaned in the sequence as described above, the cleaning blade entered between the cleaning blade and the transfer belt, and the residue such as fog toner and scattered toner that got around the back of the cleaning blade was removed. Since the edge part of the can be kept clean, a good cleaning effect could be maintained for a long time.

As another sequence, as shown in FIG. 6, the reverse rotation of the transfer belt 130 in the rotational direction is not performed before the image forming operation is started, but the transfer belt is rotated at the post rotation after the image forming operation. Is rotated in the reverse direction to discharge the residue that has wrapped around the back of the transfer belt cleaning blade, and cleans the residue discharged upstream of the transfer belt cleaning blade in the transfer belt rotation direction during the next image forming operation. There is also such a method. Even in this case, the same effect can be obtained, and the time until the transfer material is first imaged and emerges is faster than when the transfer belt is rotated in the reverse direction before the image forming operation. There is also.

<Second Embodiment> Next, a second embodiment of the present invention will be described.

The present embodiment has a sequence similar to that of the first embodiment, except that the belt cleaning blade is separated from the belt. For example, in the case where the transfer belt has a seam, the transfer belt cleaning blade edge is caught at the seam, the blade edge is chipped, or chattering occurs, and the cleaning ability is deteriorated.

Further, as shown in FIG. 7, a plurality of developing means 1a, 1b, 1c and 1d are provided around one photosensitive member 3, a plurality of toner images are superposed on the intermediate transfer belt 330, and a transfer material P is formed. In the case of the one-photoreceptor intermediate transfer method in which the batch transfer is performed on the intermediate transfer belt, the intermediate transfer belt 30
Since the toner images are sequentially placed on the first transfer belt 1, the intermediate transfer belt cleaning blade 320 cannot always be in contact with the toner image. Therefore, such an image forming apparatus requires a mechanism for separating the belt cleaning blade from the belt.

However, when the separation and contact of the intermediate transfer cleaning blade 320 is repeated in the above-mentioned structure, when the intermediate transfer cleaning blade 320 is separated from the intermediate transfer belt 301, it is blocked by the blade edge. There is a problem in that the residual material such as the residual toner after the next transfer is separated from the blade edge while being adhered to the blade edge, and is pinched between the cleaning blade and the belt when coming into contact with the belt, which deteriorates the cleaning ability.

Therefore, in the present embodiment, in the above-mentioned structure, the intermediate transfer belt 301 is driven and cleaned in the sequence as shown in FIG. The image forming operation is performed as usual, and the intermediate transfer belt cleaning blade 320 contacts the intermediate transfer belt 310 at the same time when the image formation is completed. Simultaneously with the contact of the intermediate transfer belt cleaning blade, the rotation direction of the intermediate transfer belt rotates in the direction d opposite to that during image formation for a predetermined time. And
After that, the intermediate transfer belt again rotates in the direction c of the image forming operation, and belt cleaning and post-rotation operation are performed.

When the intermediate transfer belt is cleaned in this sequence, as in the first embodiment,
Since it is possible to remove the residue such as waste toner that has entered between the cleaning blade and the intermediate transfer belt and keep the edge portion of the cleaning blade clean, a good cleaning effect can be maintained for a long period of time.

[0044]

As is apparent from the above description, according to the present invention, the rotation direction of the transfer belt or the intermediate transfer belt is rotated at the start or end of image formation in the opposite direction to the direction during image formation for a predetermined time. By doing so, it is possible to remove the residue such as fog toner or scattered toner that has entered between the cleaning blade and the belt and wraps around the back of the cleaning blade, and to keep the edge part of the cleaning blade clean, thus providing a good cleaning effect for a long time. It is possible to obtain the effect of being able to last for a long time.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram showing the periphery of a transfer belt of the image forming apparatus of FIG.

FIG. 3 is a schematic configuration diagram of a transfer belt cleaning blade.

FIG. 4 is a schematic diagram showing the operation of the transfer belt in the vicinity of the transfer belt cleaning blade according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between an image forming operation and a rotation direction of a transfer belt according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between an image forming operation and a rotation direction of a transfer belt according to the first embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between an image forming operation of an image forming apparatus according to a second embodiment of the present invention, a rotation direction of an intermediate transfer belt, and a contact / separation of an intermediate transfer belt cleaning blade.

[Explanation of symbols]

13 Drive roller 20 Transfer belt cleaning blade 71 polishing roller 130 transfer belt 131 drive motor 132 Drive motor control means 301 Intermediate transfer belt 320 Intermediate transfer belt cleaning blade

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H200 FA04 FA08 GA12 GA23 GA34                       GA44 GA47 GB12 GB25 HA12                       HB11 HB12 HB28 JA02 JB07                       JB25 JB39 JB49 JC19 KA03                       KA07 LA22 LA24 LA27 LB09                       LB13 LB39 MA03 MA20 PA10                       PA11 PA13

Claims (3)

[Claims] 1. A photoconductor on which a toner image is formed,
A conveyance belt that conveys a recording material on which the toner image formed on the surface of the photoconductor is transferred or the toner image formed on the surface of the photoconductor is transferred, and a surface of the conveyance belt. An image forming apparatus having a belt cleaning blade for cleaning, comprising drive means for driving the rotation direction of the conveyor belt in forward and reverse directions, and control means for controlling the drive of the conveyor belt, at the start or end of image formation. An image forming apparatus, wherein the rotation direction of the conveyor belt is rotated in a direction opposite to that for image formation for a predetermined time. 2. The image forming apparatus according to claim 1, wherein the conveyor belt cleaning blade is always in contact with the conveyor belt. 3. The image forming apparatus according to claim 1, further comprising a mechanism for allowing a belt cleaning blade to come into contact with and separate from the conveyor belt, and a control unit for controlling the contact and separation of the belt cleaning blade.