JP2001305872A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To forestall degradation of image quality by removing filming layer adhering on a surface of an image holding body without adding a new filming layer removing member and a new transfer driving source in an image forming device including the transfer body. SOLUTION: An intermediate transfer belt 6 comes in forced contact with a photoreceptor drum 1 only by pressing force of a first transfer roller 7 when a pressing roller 5 is moved away from the intermediate transfer belt 6 during cleaning process. Consequently, the surface velocity Vs' of the part of the intermediate transfer belt 6 coming in contact with the photoreceptor drum 1 becomes higher than central velocity Vc. As a result, the intermediate transfer belt 6 scrubs the filming layer on the surface of the photoreceptor drum 1 using difference of the velocity between the intermediate transfer belt 6 and the photoreceptor drum 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction peripheral thereof.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, an electrostatic latent image is formed by exposing a surface of an image carrier uniformly charged by a charging device by an exposure device, and the electrostatic latent image is formed by a developer. The image is visualized and transferred to a transfer body. Then, the developer (residual developer) remaining on the surface of the image carrier after the transfer step is re-cleaned by cleaning means such as a dedicated cleaning blade.

However, the residual developer after the transfer process and fine particles added to the developer pass through the cleaning blade without being wiped off during cleaning.
A phenomenon of adhering to the surface of the image carrier, a so-called filming phenomenon, may occur. If the film-like layer adhered in this way, so-called filming, is present on the surface of the image carrier, the density of the formed image is reduced, the flow of the image is generated, and the image quality is reduced.

Various measures have been proposed to solve this filming problem. For example, a filming removing member composed of a brush roll, a magnetic brush or the like is provided, and the member is rubbed against the surface of the image bearing member. Methods have been proposed to remove the mining. Recently, with the downsizing and cost reduction of the image forming apparatus, the charging device, the developing device, the transfer device, etc., which are arranged around the image carrier without providing the filming removing member as described above. A method of providing a filming removal function to an image forming element has also been proposed. At this time, of these image forming elements, those arranged in contact with the image carrier have a filming removing function.

For example, Japanese Patent Application Laid-Open No. 10-20684 proposes a method in which the transfer belt driving means has a speed changing means, and increases the speed of the transfer belt after the transfer is completed. That is, filming on the surface of the image carrier can be removed on the surface of the transfer belt by making the moving speeds of the surface of the image carrier and the surface of the transfer belt different. Filming may also occur in the transfer body in the same manner.

[0006]

However, in the above-described image forming apparatus, the filming on the surface of the image carrier is removed by the transfer body by making the moving speed of the surface of the image carrier different from that of the surface of the transfer body. If a speed difference occurs between the image carrier and the transfer member during image formation, image noise such as color shift will occur, so a speed difference between the transfer member and the photoconductor will occur only when image formation is not performed. Need to be done.

For this purpose, it is necessary to drive the image carrier and the transfer body by different drive sources, and in this case, the number of parts increases and the cost increases as compared with the case where the image carrier and the transfer body are driven by the same drive source. The problem of bulkiness arises.

According to the image forming apparatus of the present invention, there is provided an image forming apparatus having a transfer member in contact with an image carrier, without adding a new filming removing member or a new transfer member driving source. It is an object of the present invention to remove filming adhered to a device and to prevent a decrease in image quality beforehand, and to further reduce the manufacturing cost without increasing the number of parts for the purpose.

[0009]

According to a first aspect of the present invention, there is provided a rotatable image carrier having an image formed on a surface thereof, and an image carrier formed on the surface of the image carrier. An image forming means for forming an image, a transfer body on which an image formed on the image carrier is transferred, and a surface contact of the transfer body with the image carrier having an image formed on the surface by the image forming means. A transfer unit for transferring an image formed on the surface of the image carrier to the surface of the transfer body while contacting in a state, wherein the transfer body and the image carrier are Is provided with switching means for changing the contact state.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the switching means forms a part of the transfer means.

According to a third aspect, in the image forming apparatus according to the first or second aspect, a plurality of each of the image carrier, the image forming means, the transfer means, and the switching means are provided. .

According to a fourth aspect, in the image forming apparatus of the third aspect, a plurality of the switching means are independently controlled.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the switching means comprises:
At a predetermined time, the contact state of the transfer body with the image carrier,
It is controlled to change from the surface contact state to the substantial line contact state.

According to the present invention, in the image forming apparatus having the transfer member, a new transfer member is separated by separating the pressing roller located on the opposite side of the image carrier from the transfer member during the filming removing operation. Without adding a driving source, a speed difference can be provided between the surface of the transfer body and the surface of the image carrier, whereby filming on the surface of the image carrier can be removed by the transfer body, and the image quality can be improved. Can be prevented beforehand. Also, there is no need to add a new filming removing member.

[0015]

FIG. 1 is a sectional view for explaining a schematic configuration of a four-cycle system full-color image forming apparatus embodying the present invention.

In this image forming apparatus, full-color image data of cyan (C), magenta (M), yellow (Y) and black (K) is applied to the photosensitive drum 1 uniformly charged by the charging device 2. The exposure of the first color out of the four color separations is performed by the exposure device 3 to form an electrostatic latent image of the first color on the photosensitive drum 1. The developing device 4 has a developing device for developing each of the toners of cyan, magenta, yellow, and black, which are arranged in a rotary shape and are rotatable.

With respect to the electrostatic latent image, the developing device 4
The first color toner image is formed on the photosensitive drum 1 by developing the color toner. Then, the toner image is formed in a nip portion formed by the primary transfer roller 7 and a pressing roller 5 located near the primary transfer roller 7 and forming a nip between the photosensitive drum 1 and the intermediate transfer belt 6. Is transferred to the intermediate transfer belt 6 by a transfer electric field generated by applying a voltage to the primary transfer roller 7.

The intermediate transfer belt 6 rotates while holding the transferred image, and returns to the position of the primary transfer roller 7 again. At this time, the secondary transfer roller 9 is
Away from

While the intermediate transfer belt 6 makes one rotation, the developing device 4 rotates approximately 90 degrees with respect to the rotation center for developing the next color, and holds the developing device for the next color at the developing position. come. Then, the development of the second color is performed in the same manner as the development of the first color, and the primary transfer roller 7 transfers the second color toner image onto the intermediate transfer belt 6 so as to overlap the first color toner image.

This operation is repeated for the third color and the fourth color, and a full-color image is formed on the intermediate transfer belt 6. Thereafter, the secondary transfer roller 9 is pressed against the transfer roller, and the full-color image formed on the intermediate transfer belt 6 is transferred onto the transferred material 8 such as paper that has been conveyed.

The transfer material 8 onto which the full-color image has been transferred passes through a fixing device (not shown) and is transported outside the apparatus. Also,
The photoreceptor cleaning device 10 for the photoreceptor drum 1 always performs a cleaning operation by pressing against the photoreceptor drum 1 to clean the surface of the photoreceptor drum 1 after transfer.

On the other hand, the transfer body cleaning device 11 for the intermediate transfer belt 6 does not perform the cleaning operation until the images are superimposed on the intermediate transfer belt 6 in four colors and are collectively transferred to the transfer material 8. Therefore, a pressure contact release mechanism is provided, and the pressure contact / separation operation is performed.

Here, as the material of the intermediate transfer belt 6, a semiconductive material in which carbon is dispersed using polycarbonate, PTFE, or polyimide as a main raw material is used, and the thickness is 75 μm to 150 μm.

The photoconductor cleaning device 10 uses a photoconductor cleaning blade 10a in which polyurethane rubber is cut into a sheet and fixed to a support member. The transfer member cleaning device 11 includes a transfer member cleaning blade 11a and a cleaning brush 11b in which conductive fibers are arranged in a roll.

In this apparatus, an operation of removing filming adhering to the surface of the photosensitive drum 1 when image formation is not performed is performed. When the photosensitive drum 1 and the intermediate transfer belt 6 are rotating before or after the image forming operation, the pressing roller 5 is separated from the intermediate transfer belt 6 by a solenoid (not shown). As a result, the nip portion formed by the pressing roller 5 is eliminated, and the intermediate transfer belt 6 is brought into substantially linear contact with the photosensitive drum 1 by the primary transfer roller 7 in the axial direction.

At this time, for the reason described later, the surface of the intermediate transfer belt 6 moves faster than the surface of the photosensitive drum 1, and the speed difference generated causes the photosensitive drum 1 to move.
The filming adhering to the surface is scraped off by the intermediate transfer belt 6.

The filming material scraped off by the intermediate transfer belt 6 is cleaned by the transfer member cleaning device 11 of the intermediate transfer belt 6. Note that the switching unit may be provided both as the transfer unit and a separate unit.

The above operation will be described in detail with reference to FIGS. FIG. 2 is an enlarged view of the vicinity of the primary transfer portion during image formation. During image formation, a nip is formed between the photosensitive drum 1 and the intermediate transfer belt 6 to improve transfer efficiency and prevent image noise such as scattering. At this time, the roller supporting member 5a moves around the fulcrum in the direction approaching the intermediate transfer belt 6 by the action of a solenoid or a cam (not shown), and the pressing roller 5 supported by the roller supporting member 5a thereby moves the intermediate transfer unit ( (Not shown), the photosensitive drum 1 and the intermediate transfer roller 6 move to a predetermined position (the position shown in FIG.
Form a nip in surface contact. Then, the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 6 by a transfer electric field generated by applying a voltage to the primary transfer roller 7.

At this time, in order to prevent image noise such as color misregistration from occurring, the surface speed Vs of the portion of the intermediate transfer belt 6 in contact with the photosensitive drum 1 is equal to the surface speed Vp of the photosensitive drum 1. There is a need. However, since a portion of the intermediate transfer belt 6 that contacts the photosensitive drum 1 in the nip portion is bent along the surface of the photosensitive drum 1 and contracts, a virtual portion connecting the central portion of the intermediate transfer belt 6 in the thickness direction is formed. Assuming that the speed of the center line is the center speed Vc, Vs = V
In order to achieve p, it is necessary to satisfy Vc> Vp, and the rotation speed of the belt is set to this center speed Vc.

FIG. 3 is an enlarged view near the primary transfer portion during the filming removing operation. Even during the filming removal operation, the center speed Vc at the virtual center line connecting the surface speed Vp of the photosensitive drum 1 and the center in the thickness direction of the intermediate transfer belt 6 remains the same as that at the time of image formation.

At this time, the roller supporting member 5a moves away from the intermediate transfer belt 6 around the fulcrum by the action of the solenoid or the cam, whereby the pressing roller 5 supported by the roller supporting member 5a is moved to the guide hole 5b. Along to the predetermined position (the position shown in FIG. 3),
It is separated from the intermediate transfer belt 6.

Then, the intermediate transfer belt 6 is brought into pressure contact with the photosensitive drum 1 only by pressing by the primary transfer roller 7.
In other words, the photosensitive drum 1 and the intermediate transfer belt 6 come into a substantially linear contact state, and the portion of the intermediate transfer belt 6 that comes into contact with the photosensitive drum 1 is stretched in a direction opposite to that during image formation. Therefore, the surface speed Vs 'of the portion of the intermediate transfer belt 6 that comes into contact with the photosensitive drum 1 is higher than the center speed Vc, and therefore, Vs'>Vc> Vp. As a result, a speed difference occurs between the intermediate transfer belt 6 and the photosensitive drum 1, and filming on the surface of the photosensitive drum 1 can be scraped off by the intermediate transfer belt 6.

That is, a change in the state of contact between the photosensitive drum 1 and the intermediate transfer belt 6 causes a speed difference between these contact surfaces, so that the filming material on the photosensitive drum 1 is reduced by this speed difference. Is scraped off. The scraped filming material is cleaned by the transfer body cleaning device 11 of the intermediate transfer belt 6. Further, even when the image carrier is in a belt shape, both the image carrier and the transfer body are in a belt shape, that is, a combination of a belt-shaped transfer body and a drum-shaped image carrier, and a drum-shaped transfer body. Obviously, a combination of a belt-shaped image carrier and a combination of a belt-shaped transfer member and a belt-shaped image carrier may be used.

Although the embodiment has been described by taking a four-cycle full-color image forming apparatus as an example, the present invention can be applied to all image forming apparatuses using a belt-shaped transfer member. For example, the present invention can be applied to a tandem-type full-color image forming apparatus having an image carrier for each color or a monochrome image forming apparatus. The belt-shaped transfer member may be an intermediate transfer belt or a transfer conveyance belt, and the image forming method may be an electrophotographic method or an electrostatic recording method.

FIG. 4 is another embodiment of the present invention and is a cross-sectional view for explaining a schematic configuration of a tandem type full-color image forming apparatus. Note that the reference numerals used in the above description are used as they are.

In the four-cycle full-color image forming apparatus, only one photosensitive drum 1 is provided. In the tandem full-color image forming apparatus, cyan (C), magenta (M), and yellow (Y) are used. Photoreceptor drums 1 for each of four colors, black (K)
Is provided.

With the four photosensitive drums 1, the charging device 2, the exposing device 3, the developing device 4, the pressing roller 5, the primary transfer roller 7, and the photosensitive member cleaning device 1
0, and a photoconductor cleaning blade 10a is provided for each photoconductor drum 1 respectively.

Each photosensitive drum 1 is arranged along the intermediate transfer belt 6, and the developed toner image of each color formed on the photosensitive drum 1 is moved from the left to the right. 6 is transferred so as to be superimposed on 6. Note that the processes of latent image formation and development are as described above, and description thereof will be omitted.

A nip portion is formed between the photosensitive drum 1 and the intermediate transfer belt 6 by the primary transfer roller 7 and the pressing roller 5 located near the primary transfer roller 7, and a voltage is applied to the primary transfer roller 7. The transfer to the intermediate transfer belt 6 is performed by the transfer electric field generated thereby.

After the transfer of each color is sequentially performed to form a full-color image on the intermediate transfer belt 6, the transfer material 8 such as paper that has been conveyed is transferred between the secondary transfer rollers 9 on the right side in the figure. The full-color image is transferred onto the transfer material 8 by being pressed. The transfer material 8 to which the full-color image has been transferred is sent to a fixing device (not shown) and fixed.

Each photosensitive roller 1 is cleaned by changing the position of each pressing roller 5 by a pressure releasing mechanism and separating it from the intermediate transfer belt. The principle of cleaning has already been described with reference to FIGS.
This is the same as the description given using.

[0042]

As described above, by using the image forming apparatus of the present invention, in an image forming apparatus having a transfer member in contact with an image carrier, a new member for removing filming and a new transfer member are provided. Filming adhered to the surface of the image carrier can be removed without adding a driving source, and the image quality can be prevented from deteriorating.Furthermore, the manufacturing can be performed without increasing the number of parts. This has the effect of keeping costs low.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a four-cycle type full-color image forming apparatus embodying the present invention.

FIG. 2 is an enlarged view of the vicinity of a primary transfer portion during image formation.

FIG. 3 is an enlarged view of the vicinity of a primary transfer portion during a filming removing operation.

FIG. 4 is another example in which the present invention is implemented, and is a cross-sectional view illustrating a schematic configuration of a tandem-type full-color image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging device 3 exposure device 4 developing device 5 pressing roller 5 a roller support member 5 b guide hole 6 intermediate transfer belt 7 primary transfer roller 8 transfer material 9 secondary transfer roller 10 photosensitive member cleaning device 10 a photosensitive member cleaning Blade 11 Transfer member cleaning device 11a Transfer member cleaning blade 11b Cleaning brush Vc Center speed Vs, Vp Surface speed

Claims (5)

[Claims] A rotatable image carrier on which an image is formed; an image forming means for forming an image on the surface of the image carrier; and an image formed on the image carrier. The image formed on the surface of the image carrier is transferred while the transfer body is brought into surface contact with the image carrier on which the image is formed by the image forming means. Transfer means for transferring to the surface of the body, the image forming apparatus further comprises at least one of the transfer body and the image carrier is a belt-like, An image forming apparatus comprising a switching unit for changing a contact state with the image carrier. 2. The image forming apparatus according to claim 1, wherein the switching unit forms a part of the transfer unit. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus includes a plurality of each of the image carrier, the image forming unit, the transfer unit, and the switching unit. An image forming apparatus comprising: 4. An image forming apparatus according to claim 3, wherein a plurality of said switching means are independently controlled. 5. The image forming apparatus according to claim 1, wherein the switching unit changes a contact state of the transfer body to the image carrier at a predetermined time. An image forming apparatus characterized in that the image forming apparatus is controlled to change from a line contact state to a substantial line contact state.