JPH05313525A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the back of a transfer sheet from being soiled by providing a sheet transfer bias roller and a roller cleaning blade, which cleans the sheet transfer bias roller, on the same member so that their positional relationship is constant. CONSTITUTION:The sheet transfer bias roller 23-1 and the roller cleaning blade 50-4 both are provided on the upper bracket 23-4, and their positional relationship is invariable irrespective of a change in position of the upper bracket 23-4. Therefore, even when the upper bracket 23-4 and the lower bracket 23-5 shake because of the rotation of an eccentric cam 51-1, this relationship does not change and the roller cleaning blade 50-4 is always in contact with the sheet transfer bias roller 23-1 under the satisfactory conditions, and since the sheet transfer bias roller 23-1 is rotated all the time, toner on the roller is satisfactorily removed. Thus, the surface of the sheet transfer bias roller 23-1 is always cleaned and soiling of the back of a transfer sheet is eliminated.

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 An intermediate transfer member as a toner carrier for electrostatically primary transferring a toner image formed on an image carrier,
The intermediate transfer member is provided on a swingable bracket so as to come into contact with and separate from the intermediate transfer member, and the intermediate member is used when the image on the intermediate transfer member is transferred onto a transfer sheet. A paper transfer bias roller that can be in a state of being pressed by the intermediate transfer member so as to perform a secondary transfer by passing a transfer paper between the transfer member and the transfer member. There is an image forming apparatus that has a blade that scrapes off the toner adhering to a roller.

In FIGS. 5 to 7, reference numeral 19 denotes an intermediate transfer member as a toner carrier for electrostatically primary transferring a toner image formed on an image carrier (not shown), which is composed of a belt. ing.

The intermediate transfer belt 19 has a driving roller 21.
The paper transfer bias roller 23-1 is provided at a position facing the drive roller. The paper transfer bias roller 23-1 is rotationally driven by an independent driving means (not shown).

The paper transfer bias roller is kept away from the intermediate transfer belt 19 until a full-color toner image is formed on the intermediate transfer belt 19 and transferred to the transfer paper. In other words, it is necessary to keep pressure contact from just before the transfer paper arrives until immediately after it passes, but at other times,
Keep it apart.

Then, at the stage where the full-color toner image is formed and transferred onto the transfer paper, the belt is pressed against the transfer paper to pass the transfer paper between them.

Therefore, the paper transfer bias roller 23-1 is required to be brought into contact with and separated from the intermediate transfer belt 19 and, moreover, at the time of press contact, it is necessary to press it with a predetermined press contact force.

Therefore, the paper transfer bias roller 23-1
Is provided on the bracket 50 whose one end is pivotally supported by the support shaft 23-8. The other end of the bracket 50 is the eccentric cam 5
The eccentric cam is oscillated in accordance with the rotation of the eccentric cam to bring the paper transfer bias roller into contact with and separate from the intermediate transfer belt.

Since it is necessary to bring the paper transfer bias roller 23-1 into contact with the intermediate transfer belt with a predetermined pressure contact force,
As shown in FIG. 7, the roller is axially supported by a bearing member 50-3 that slides in a slit 50-1 formed in a bracket 50, and an extensible spring 50-2 mounted in the slit is used. It is urged by a force that always pushes it up.

Moreover, the rotation of the eccentric cam 51 causes the eccentric cam 51 to rotate as shown in FIG.
As the bracket 50 is lowered, the bearing reaches the stroke end of the slit 50-1 and the movement of the paper transfer bias roller 23-1 by the spring is stopped. Are adjusted to be separated from the intermediate transfer belt 19.

On the other hand, in the state where the other end of the bracket 50 is pushed up by the rotation of the eccentric cam 51, as shown in FIG. 5, the paper transfer bias roller 2 via the bearing 50-3.
3-1 is also pushed up to the range where the spring works, and finally the paper transfer bias roller 23-1 is pressed against the intermediate transfer belt 19 by the elastic force of the spring 50-2.

In this state, the transfer paper enters between the intermediate transfer belt and the paper transfer bias roller, and the toner image on the belt is transferred onto the surface of the paper.

By the way, the paper transfer bias roller 23-1
Is biased in the reverse direction of the toner on the intermediate transfer belt, so that the toner easily adheres. For this reason, the scattered toner adheres, and the toner adhered when the transfer paper is jammed remains without being cleaned. Further, toner and the like in the area protruding from the transfer paper adheres.

If this is left unattended, it may cause the backside of the next transfer paper to be soiled. Therefore, in order to remove the toner from the paper transfer bias roller 23-1, the blade 50 is attached to the bracket 50.
-3 is provided. The blade 50-3 is provided on the bracket 50.

[0015]

In the above technique, the paper transfer bias roller 23-1 moves on the bracket 50 according to the swing of the bracket 50. Therefore, the blade 50
-3 is brought into contact with and separated from the paper transfer bias roller 23-1 according to the movement of the paper transfer bias roller 23-1.

Therefore, the blade 50-3 may be separated from the paper transfer bias roller 23-1.
Under this condition, the toner is not removed from the roller,
Since the toner is insufficiently removed, the transfer paper still causes back stains.

Therefore, an object of the present invention is to provide an image forming apparatus capable of eliminating stains on the back of transfer paper.

[0018]

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

(1). The paper transfer bias roller and the roller cleaning blade for cleaning the paper transfer bias roller are provided on the same member so that the positional relationship between them may be kept constant (claim 1).

(2). In (1), the paper transfer bias roller is provided on a swingable bracket with its movements other than rotation restricted.

[0021]

The roller cleaning blade is always in contact with the paper transfer bias roller while maintaining a predetermined related position.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 9 indicates a photosensitive drum as an image bearing member. The toner image on the photosensitive drum 9 is transferred to the intermediate transfer belt 1 by the belt transfer bias roller 20.
9 is primarily transcribed.

By repeating the primary transfer, the paper transfer bias roller 23-1 is separated from the driving roller 21 until just before the full-color image is formed on the intermediate transfer belt 19 and the transfer paper is fed. Then, at least during the passage of the paper, the state of being pressed against the intermediate transfer belt 19 is maintained. After passing the paper, the paper transfer bias roller 23-1 is separated from the intermediate transfer belt 19.

Such an operation is the same as that described in the above-mentioned prior art. In order to perform this operation, in this example,
One side of each of the upper bracket 23-4 and the lower bracket 23-5 is commonly supported by the immovable member by a support shaft 23-8, and each of them can operate independently in a substantially vertical direction.

Furthermore, an extensible spring 23-6 is interposed between these other sides, and an eccentric cam 51-1 is attached to the other side of the lower bracket 23-5 in accordance with the above-mentioned prior art. It is provided so as to swing around the support shaft 23-8.

The paper transfer bias roller 23-1 is rotatably supported on the bracket 23-4. As shown in FIG. 2, the shaft support is mounted on the bracket upper portion 23-4 by the bearing 60, and the operation other than rotation is restricted. It is not configured to move in the slit provided.

A roller cleaning blade 50-4 is provided on the bracket 23-2, and the paper transfer bias roller 23-1 is provided with conditions such as a position and an angle which are most suitable for cleaning, which are obtained by experiments. It is adjusted and fixed.

This roller cleaning blade 50-4
A toner recovery container 23-7 is detachably provided below the bracket and below the bracket 23-5.

In such a configuration, the paper transfer bias roller 23-1 and the roller cleaning blade 50-4 are commonly provided on the bracket 23-4, and the relative positions of them are the same as those of the bracket upper 23-4. It remains unchanged regardless of changes.

Therefore, by the rotation of the eccentric cam 51-1,
This relationship does not change even when the upper bracket 23-4 and the lower bracket 23-5 swing, and the paper transfer bias roller 23-
1 always, roller cleaning blade 50-4
However, since the paper transfer bias roller 23-1 is constantly rotating, the toner on the roller can be removed very well.

As a result, the paper transfer bias roller 23-1
Since the upper part is constantly cleaned, the problem of back stain on the transfer paper is solved.

The toner T thus scraped off is
Since it falls into the toner collecting container 23-7, it may be collected appropriately.

The pressing force of the paper transfer bias roller 23-1 against the intermediate transfer belt 19 is the spring 23-6.
This makes it possible to maintain a substantially constant predetermined value required for transfer.

An outline of a color copying machine will be described below as an example of an image forming apparatus suitable for carrying out the present invention.

In FIG. 3, a color image reading device (hereinafter referred to as a color scanner) 1 transfers an image of an original 3 through 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 apparatus (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 copy operation is started, the color scanner 1 starts reading BK image data at a predetermined timing, and based on this image data, optical writing and latent image formation by laser light is started (hereinafter referred to as 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 photoconductor drum 9 is transferred onto the surface of the intermediate transfer belt 19 which is driven at the same speed as the photoconductor drum 9 (hereinafter, from the photoconductor 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.

On the photosensitive drum 9 side, the C step is performed after the BK step, and the C image data reading by the color scanner 1 is started at a predetermined timing.
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 at the time when the trailing edge of the latent image passes, the development is inoperative 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 19 is stretched around a drive roller 21, a transfer bias roller 20, and a group of driven rollers, and is drive-controlled by a drive motor (not shown) as described later.

As shown in FIG. 4, the belt cleaning unit 22 includes a brush roller 22-1, a roller cleaning blade 22-2 as a cleaning means, and a contacting / separating mechanism for mounting the blade on the intermediate transfer belt and contacting / separating the blade. 22-3 and the like, and while the second, third, and fourth colors are being belt-transferred after the first-color BK image is belt-transferred, they are separated from the belt surface by the contact / separation mechanism 22-3. Keep it.

The structure of the paper transfer unit 23 conforms to the contents already described.

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.

Now, 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 to 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, following 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, only the developing device for that color is in the developing state until the predetermined number of sheets are finished, 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.

[0078]

According to the present invention, it is possible to provide an image forming apparatus capable of eliminating stains on the back of transfer paper.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a main part of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view illustrating a shaft support portion of a paper transfer bias roller.

FIG. 3 is a configuration diagram of an image forming apparatus suitable for implementing the present invention.

4 is a partially enlarged explanatory view of FIG.

FIG. 5 is an explanatory diagram of a conventional technique.

FIG. 6 is an explanatory diagram of a conventional technique.

FIG. 7 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 23-1 Paper Transfer Bias Roller 50-4 Roller Cleaning Blade

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshiaki Motohashi 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Hideki Ueyama 1-3-6 Nakamagome, Ota-ku, Tokyo・ In Ricoh Co., Ltd. (72) Inventor Takashi Misasai 1-3-6 Nakamagome, Ota-ku, Tokyo ・ In Ricoh Co., Ltd.

Claims (2)

[Claims] 1. An intermediate transfer member as a toner carrier that electrostatically primary-transfers a toner image formed on an image carrier, and a contacting member facing the intermediate transfer member. It is provided on a swingable bracket so that it can be separated, and when the image on the intermediate transfer body is transferred to the transfer paper, the transfer paper is passed between the intermediate transfer body and the secondary transfer. An image forming apparatus having a paper transfer bias roller that can be pressed against the intermediate transfer body to perform the above operation, and a blade that contacts the paper transfer bias roller and scrapes off the toner adhering to the paper transfer bias roller. In the image forming method described above, a paper transfer bias roller and a roller cleaning blade for cleaning the paper transfer bias roller are provided on the same member so that the positional relationship between them is kept constant. Equipment. 2. The image forming apparatus according to claim 1, wherein the paper transfer bias roller is provided on a swingable bracket with movements other than rotation restricted.