JPH05303310A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the scattering of toner and the occurrence of the contamination of the toner inside a device by adding a conductive member capable of applying a bias voltage, to a cleaning means removing the toner remaining on a first carrier. CONSTITUTION:When a color image is formed out an intermediate transfer belt 19 as a second carrier, a blade 22-2 as the cleaning means requires releasing from the belt 19. In other words, after a transfer is performed on a transfer paper, the toner remaining on the belt 19 is scratched by the blade 22-2, but the scratched toner is floated in a space inside a cleaning unit. When the blade 22-2 is released, and the floated toner is scattered to the downstream side of the blade 22-2, and stuck on the belt 19, again, the floated toner appears as soiling on a copied image. Then, the switch of a power supply means 50 is changed over, and the bias voltage having the polarity reverse to the electrifying polarity of the toner, is applied to a conductive blade holder 39 as a blade supporting member, to collect the scattered toner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic method such as a facsimile, and more specifically to an image forming apparatus having a carrier that carries a toner image and conveys toner to the next step.

[0002]

2. Description of the Related Art In a color image forming apparatus, a subtractive color mixture
It is necessary to form the primary color toner images on the transfer paper in an overlapping manner. Conventionally, as shown in, for example, Japanese Patent Application Laid-Open No. 52-73738, toner images of respective color components are formed on a photoreceptor several times, and the toner images of respective color components are formed once. There is an image forming apparatus that forms a color image by sequentially transferring onto a transfer paper.

For example, there is provided a first carrier, a second carrier, and means for transferring the toner image on the first carrier onto the second carrier, and the second carrier. An example is an image forming apparatus in which a body carries a toner image transferred from the first carrier and is rotationally driven to convey the toner image to a process unit for transferring the toner image to a transfer sheet.

In such a color image forming apparatus, the first
In order to bring the transfer paper into close contact with the photoconductor as the carrier of the apparatus several times, a clamp mechanism for clamping the end of the transfer paper is provided, but the mechanism is very complicated and
Images cannot be transferred to the clamp area of the transfer paper.

Therefore, the toner image for each color component is formed on the photoconductor several times, and the toner image for each color component is formed on the intermediate transfer body as the second carrier which is rotationally driven. There is a technique in which the full color toner images are created by sequentially superimposing them on each other, and the full color toner images are collectively transferred onto the transfer paper.

In this technique, the toner remaining on the intermediate transfer member after the image formation is cleaned by a cleaning device. By the way, this cleaning device is provided with, for example, a cleaning blade as a cleaning means, and the cleaning blade is brought into contact with the intermediate transfer member to scrape and remove the residual toner.

[0007]

However, in the above technique, there is a problem that after the residual toner is scraped off by the cleaning blade, the toner is scattered when the blade is released and the inside of the apparatus is soiled.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image forming apparatus which prevents toner from scattering and does not cause toner stain in the apparatus for a long time.

[0009]

In order to achieve the above object, the present invention has any one of the following configurations.

(1). Cleaning means for removing the toner remaining on the second carrier is provided, and a conductive member capable of applying a bias voltage is attached to the cleaning means (claim 1).

(2). In (1), the cleaning means can be brought into and out of contact with the second carrier (claim 2).

(3). In (1), in claim 2, the cleaning means is a blade made of an elastic body, and the conductive member is a supporting member of the blade (claim 3).

(4). In (1) or (2), the second
Immediately before the cleaning means is released from the carrier of
A bias voltage having a polarity opposite to the charging polarity of the toner is applied to the conductive member, and the application of the bias voltage is stopped after the contact.

(5). In (3), the surface of the supporting member of the blade is roughened (claim 5).

(6). In (1) or (2), the second
Immediately before the cleaning means is released from the carrier, a bias voltage having a polarity opposite to the toner charge polarity is applied to the conductive member, and a bias voltage having the same polarity as the toner charge polarity is applied by switching immediately before the contact. The application is stopped after the contact (claim 6).

[0016]

The toner scattered when the blade is released is attracted to the conductive member by the bias voltage.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an image forming apparatus having a second carrier that carries a toner image and conveys the toner image to the next step. Specifically, the second carrier carries the toner image transferred from the photosensitive member, which is the first image carrier, and is rotationally driven until the step of transferring the toner image to the transfer target such as transfer paper. Is also an intermediate transfer member that conveys a carrier, and also includes a carrier that carries and conveys another carrier electrostatically.

Hereinafter, description will be given based on an example in which the second carrier is an intermediate transfer belt. FIG. 2 shows a schematic configuration diagram of the color copying apparatus according to the present invention, and FIG. 3 shows an enlarged configuration around the photosensitive member and the intermediate transfer belt.

In FIG. 2, a color image reading device (hereinafter referred to as a color scanner) 1 receives an image of an original 3 via an illumination lamp 4, mirror groups 5-1, 5-2, 5-3 and a lens 6. An image is formed on the color sensor 7 by a photoelectric conversion element, for example, a CCD. Then, the color image information of the document is read for each color separation light of blue (hereinafter referred to as B), green (hereinafter referred to as G), and red (hereinafter referred to as R), and converted into electrical image information. ..

Based on the B, G, and R color-separated image signal intensity levels obtained by the color scanner 1,
Color conversion processing is performed by an image processing unit (not shown) to obtain color image data of black (hereinafter referred to as BK), cyan (hereinafter referred to as C), magenta (hereinafter referred to as M), and yellow (hereinafter referred to as Y). obtain.

The color image recording device (hereinafter referred to as a color printer) 2 described below is used to
Visualization of C, M, and Y is performed, and these are superposed to form a four-color full-color image.

Next, the outline of the color printer 2 will be described with reference to FIG. The writing optical unit 8 converts the color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the original image, and electrostatically charges the photosensitive drum 9 as the first latent image carrier. Form a latent image.

The photoconductor drum 9 rotates counterclockwise as shown by the arrow, around which a photoconductor cleaning unit (including a pre-cleaning static eliminator) 10, a static erasing lamp 11, a charger 12, and a potential. Sensor 13, BK developing device 14, C developing device 15, M developing device 16, Y developing device 17,
A development density pattern detector 18, an intermediate transfer belt 19 as a second carrier, and the like are arranged.

Each developing device rotates a developing sleeve (14-1, 15-1, 16-1, 17-1) so that the developer is opposed to the photosensitive drum 9 in order to develop the electrostatic latent image.
And a developing paddle that rotates to pump up and stir the developer, and a toner concentration detection sensor for the developer.

Development operation sequence (color image formation sequence)
Will be described below with an example of BK, C, M and Y. However, the image forming order is not limited to this.

When the copying operation is started, the color scanner 1 starts reading BK image data at a predetermined timing, and based on the image data, optical writing and latent image formation by laser light is started (hereinafter, BK image). The electrostatic latent image based on the data is called a BK latent image. The same applies to C, M, and Y).

In order to enable development from the front end of the BK latent image, the developing sleeve 14-1 is started to rotate before the front end of the latent image reaches the developing position of the BK developing device 14, and the BK latent image is transferred to the B side.
Develop with K toner. Then, after that, the developing operation of the BK latent image region is continued, but when the rear end portion of the BK latent image passes the BK developing position, the developing operation is disabled. This is completed at least before the leading edge of the C latent image by the next C image data arrives.

Next, the BK toner image thus formed on the photosensitive drum 9 is transferred onto the surface of the intermediate transfer belt 19 which is driven at the same speed as the photosensitive drum 9 (hereinafter, the photosensitive member is transferred to the intermediate transfer belt). The toner image transfer is called the belt transfer).

The belt transfer is performed by applying a predetermined bias voltage to the transfer bias roller 20 while the photosensitive drum 9 and the intermediate transfer belt 19 are in contact with each other.

On the intermediate transfer belt 19, the photosensitive drum 9 is attached.
The toner images of BK, C, M, and Y that are sequentially formed on the same surface are sequentially aligned on the same surface to form a belt transfer image of four-color superimposition, and then are collectively transferred to a transfer paper. The configuration and operation of this intermediate transfer belt unit will be described later.

By the way, on the photosensitive drum 9 side, the C step is performed after the BK step, but at a predetermined timing, the C image data reading by the color scanner 1 is started,
A C latent image is carried by writing a laser beam using the image data.

The C developing device 15 is
After the trailing edge of the previous BK latent image has passed and before the leading edge of the C latent image has reached, the developing sleeve 15-1 is started to rotate and C
Develop the latent image with C toner.

Thereafter, the development of the C latent image area is continued, but when the trailing edge of the latent image passes, the development is inoperable as in the case of the previous BK developing device. This is also completed before the leading edge of the next M latent image arrives.

Regarding each step of M and Y,
The operations of reading image data, forming a latent image, and developing are the same as those of the steps BK and C, and thus the description thereof will be omitted.

Next, the intermediate transfer belt unit will be described. The intermediate transfer belt unit 19 includes the drive roller 2
1, the transfer bias roller 20, and a group of driven rollers are stretched around, and are driven and controlled by a drive motor (not shown) as described later.

As shown in FIG. 3, the belt cleaning unit 22 includes a brush roller 22-1, a blade 22-2 as a cleaning means, and a contact / separation mechanism 22- for contacting and separating the outer blade with the intermediate transfer belt. 3 and the like, and is separated from the belt surface by the contact / separation mechanism 22-3 during the belt transfer of the second, third, and fourth colors after the belt transfer of the BK image of the first color. ..

The paper transfer unit 23 includes a paper transfer bias roller 23-1 and a roller cleaning blade 23-.
2 and a belt contact / separation mechanism 23-3 and the like.

The bias roller 23-1 is usually
Although separated from the surface of the intermediate transfer belt 19, when the four-color superimposed image formed on the surface of the intermediate transfer belt 19 is collectively transferred to the transfer paper, it is pressed by the contact / separation mechanism 23-3 at a timing, A predetermined bias voltage is applied to the roller 23-1 to transfer the paper.

The transfer paper 24 is fed by the paper feed roller 25 and the registration roller 26 at the timing when the leading edge of the four-color superimposed image on the intermediate transfer belt surface reaches the paper transfer position.

The movement of the intermediate transfer belt 19 is 1
There are three possible operation methods after the belt transfer of the BK toner image of the color has been completed up to the rear end. One of them can be used, or depending on the copy size, in terms of copy speed, etc. , Operate by a combination of efficient methods.

(1). Constant speed forward method. Even after the BK toner image is transferred onto the belt, it continues to move forward at a constant speed.

.. Then, B on the surface of the intermediate transfer belt 19
When the K image front end position reaches the belt transfer position at the contact portion with the photosensitive drum 9 again,
Make sure that the tip of the next C toner image is exactly at that position.
An image is formed with a timing.

.. After that, by the same operation, M, Y
Proceeding to the image process, a belt transfer image of four colors is obtained.

.. Subsequent to the fourth color Y toner image belt transfer step, the four color superimposed toner images on the belt surface are collectively transferred onto the transfer paper 24 as described above while moving forward.

(2). Skip forward method. When the belt transfer of the BK toner image is completed, the intermediate transfer belt 19 is separated from the surface of the photosensitive drum 9 and is skipped at high speed in the forward direction as it is. After moving a predetermined amount, the initial forward speed is restored. After that, the intermediate transfer belt 19 is brought into contact with the photosensitive drum 9 again.

.. Then, B on the surface of the intermediate transfer belt 19
When the front end position of the K image reaches the transfer position of the intermediate transfer belt again, the image is formed on the photosensitive drum 9 side with a timing so that the front end part of the next C toner image comes to that position. .. As a result, the C image is accurately aligned with the BK image and transferred onto the belt in a superimposed manner.

.. After that, by the same operation, M, Y
Proceeding to the image process, a belt transfer image of four colors is obtained.

.. Following the belt transfer process for the Y toner image of the fourth color, the 4
The color-superposed toner images are collectively transferred onto the transfer paper 24.

(3). Reciprocating (quick return) method. When the belt transfer of the BK toner image is completed, the intermediate transfer belt 19 is separated from the surface of the photosensitive drum 9, and
At the same time as stopping the forward movement, it makes a high speed return in the opposite direction.

Return is B on the surface of the intermediate transfer belt 19.
The front end position of the K image passes the position corresponding to the belt transfer in the opposite direction, and after moving for a preset distance, it is stopped and put in the standby state.

.. Next, when the front end portion of the C toner image on the photosensitive drum 9 side reaches a predetermined position before the belt transfer position, the intermediate transfer belt 19 is restarted in the forward direction. Further, the intermediate transfer belt 19 is started again in the forward movement direction.

Further, the intermediate transfer belt 19 is brought into contact with the surface of the photosensitive drum 9 again. Also in this case, the C image is transferred to the intermediate transfer belt 19 under the condition that it is accurately overlapped with the BK image on the surface of the intermediate transfer belt 19.

.. After that, by the same operation, M, Y
Proceeding to the image process, a belt transfer image of four colors is obtained.

.. Subsequent to the belt transfer process for the Y toner image of the fourth color, the four-color superimposed toner image on the surface of the intermediate transfer belt 19 is collectively transferred onto the transfer paper 24 by moving forward at the same speed without returning.

The transfer paper 24 to which the four-color superposed toner images are collectively transferred from the surface of the intermediate transfer belt is the paper transport unit 2
7, the toner image is conveyed to the fixing device 28, and the toner image is melted and fixed by the fixing roller 28-1 and the pressure roller 28-2, which are controlled to a predetermined temperature, and is discharged to the copy tray 29.
Get a full color copy.

The photosensitive drum 9 after the belt transfer is
The surface is cleaned by the photoconductor cleaning unit 10, and the charge is uniformly discharged by the charge removing lamp 11. The intermediate transfer belt 19 after the toner image is transferred onto the transfer paper 24 is pressed by the belt cleaning unit 22 again by the contact / separation mechanism 22-3, and the surface is cleaned.

At the time of repeat copying, the operation of the color scanner 1 and the image formation on the photosensitive drum 9 are continued from the Y (fourth color) image process of the first sheet, and then the BK of the second sheet at a predetermined timing. (First color) Go to the image process.

Further, in the case of the intermediate transfer belt 19, after the batch transfer process of the first four-color superimposed image onto the transfer paper,
The BK toner image of the second sheet is belt-transferred to the area whose surface is cleaned by the belt cleaning unit 22. After that, the same operation as the first sheet is performed.

The transfer paper cassettes 30, 31, 32,
Transfer sheets of various sizes are stored in the sheet 33, and the sheet is fed and conveyed in the direction of the registration roller 26 at a timing from a storage cassette of the sheet of size designated by the operation panel (not shown). When manually feeding paper for overhead projectors, thick paper, etc., the manual feed tray 34 is used.

Up to this point, the description has been given of the copy mode in the case of obtaining four full colors.
In the color copy mode, the same operation as described above is performed for the designated color and the number of times.

In the single-color copy mode, until the predetermined number of sheets are finished, only the developing device for that color is in the developing state, and the intermediate transfer belt 19 remains in contact with the surface of the photosensitive drum 9. Drive at a constant speed in the forward direction,
The belt cleaning unit 22 is also the intermediate transfer belt 19
The copy operation is performed while keeping the contact with.

When forming a color image on the intermediate transfer belt 19, it is necessary to release the blade 22-2 as the cleaning means from the intermediate transfer belt 19. The toner remaining on the belt after being transferred to the transfer paper is scraped off by the blade, but the scraped toner is floating in the space inside the cleaning unit.

Here, when the blade 22-2 is released,
The floating toner is scattered outside the unit, especially on the downstream side of the blade 22-2. If the scattered toner adheres to the transfer belt again, it appears as stains on the copy image.

Therefore, as shown in FIG. 1, by switching the switch of the power supply means 50, a conductive material which is a blade supporting member for collecting the toner scattered when the blade 22-2 is released from the intermediate transfer belt 19. A bias voltage having a polarity opposite to the charging polarity of the toner is applied to the blade holder 39.

The bias voltage may be always applied, but from the viewpoint of power consumption, it is preferable to stop the application at the time of contact with the blade and start the application immediately before the blade is released (FIG. 4 (A)).

By roughening the surface of the blade holder 39, the toner captured on the surface of the holder can be made hard to drop.

As another example of the present invention, it is possible to apply a bias voltage having a polarity opposite to that of the toner immediately before the blade is released, and a bias voltage having the same polarity as that of the toner immediately before the contact (FIG. 4). (B)).

Therefore, when the amount of toner captured on the blade holder becomes excessive, the electrostatic repulsion force between the holder and the toner and the impact force at the time of contact cause the toner to flow to the downstream side of the contact portion of the blade. It falls and adheres to the belt.

In this case, as shown in FIG. 5, the next image forming area starts after the blade starts contacting, and the peripheral length of the intermediate transfer belt is larger than the maximum peripheral length of the transfer sheet that can be used. The formed toner T adheres to the non-image area when the next image is generated, that is, before the leading edge of the next image area and after the trailing edge of the image area.

Therefore, the dirt caused by the toner falling on the copy image does not occur. The toner attached to the belt is removed by the next cleaning operation.

[0071]

According to the present invention, it is possible to provide an image forming apparatus which prevents toner from scattering and does not cause toner stain in the apparatus for a long time.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a cleaning unit according to the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of a color copying machine according to the present invention.

FIG. 3 is an enlarged view of the photosensitive member of FIG. 2 and an area around an intermediate transfer belt.

FIG. 4 is a diagram illustrating the relationship between the contact / separation of the blade and the bias voltage application timing.

FIG. 5 is an explanatory diagram of an intermediate transfer belt.

[Explanation of symbols]

 19 Intermediate transfer belt 22-2 (as an intermediate transfer member) Blade (as a cleaning means) 39 Blade holder (as a conductive member)

Claims (6)

[Claims] 1. A first carrier, a second carrier, and means for transferring a toner image on the first carrier to the second carrier, and the second carrier. In the image forming apparatus, the body carries the transferred toner image from the first carrier and is driven to rotate to convey the toner image to a recording paper transfer step. An image forming apparatus comprising: a cleaning unit for removing the toner remaining on the carrier, and a conductive member capable of applying a bias voltage attached to the cleaning unit. 2. An image forming apparatus according to claim 1, wherein the cleaning means can be brought into and out of contact with the second carrier. 3. The image forming apparatus according to claim 1, wherein the cleaning means is a blade made of an elastic body, and the conductive member is a supporting member for the blade. 4. The method according to claim 1 or 2, wherein a bias voltage having a polarity opposite to a charging polarity of toner is applied to the conductive member immediately before the cleaning means is released from the second carrier, and after abutting. An image forming apparatus, characterized in that the application of the bias voltage is stopped. 5. The image forming apparatus according to claim 3, wherein the surface of the supporting member of the blade is roughened. 6. The method according to claim 1 or 2, wherein a bias voltage having a polarity opposite to the charging polarity of the toner is applied to the conductive member immediately before the cleaning means is released from the second carrier, and immediately before the contact. An image forming apparatus characterized in that a bias voltage having the same polarity as the toner charging polarity is switched and applied, and the application is stopped after contact.