JPH05303291A - Transfer device for color copying machine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of an abnormal image by providing a pressurizing force adjusting means adjusting the pressurizing force of a paper transfer bias roller against an intermediate transfer body, to a prescribed value. CONSTITUTION:A taper roller 23-4 made of a material hardly deformed is freely rotatably fitted to the shaft part of the paper transfer bias roller 23-1 through a bearing, and an adjusting screw 23-5 is screwed in the side plate part of a paper transfer unit 23, so as to abut on the side part of the taper roller 23-4. When the taper roller 23-4 can be moved in an axial direction by the rotation of the adjusting screw 23-5, to obtain a position to the side of the center of a shaft, the pressing of the taper surface of the taper roller, to a belt driving roller 21, becomes strong, and a gap is reduced, to decrease the pressurizing force. When backward rotation is attained, the force of a spring more acts, to increase the pressurizing force. Therefore, the pressurizing force of the paper transfer bias roller 23-1 against the intermediate transfer body 19 can be adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for a color copying machine.

[0002]

2. Description of the Related Art In a color copying machine, a transfer device section in which full-color toner is formed on an intermediate transfer member, for example, an intermediate transfer belt, and the full-color toner image is in pressure contact with the intermediate transfer belt and a paper transfer bias roller. There is known a method of transferring to a transfer paper while applying a transfer bias.

In such a transfer device,

[0004]

However, in the above technique, if the pressure contact force of the paper transfer bias roller with respect to the intermediate transfer belt is too strong, the toner image once transferred onto the transfer paper is reversely transferred to the intermediate transfer belt again. The image returns to the transfer belt, resulting in so-called voids, reverse transfer, and other images. Alternatively, an abnormal image referred to as a so-called bug-eating print is generated in a portion where the toner adhesion amount is large.

Therefore, an object of the present invention is to provide a transfer device of a color copying machine which can prevent the occurrence of such an abnormal image.

[0006]

In order to achieve the above object, the present invention has any one of the following configurations. (1). A pressing force adjusting means for adjusting the pressing force of the paper transfer bias roller to the intermediate transfer member to a predetermined value is provided (Claim 1).

(2). In (1), the intermediate transfer member is a belt, and the belt drive roller supporting the belt is in pressure contact with the paper transfer bias roller via the belt, and the pressing force adjusting means is the paper transfer bias roller. A taper roller provided coaxially, a counter roller coaxial with the belt driving roller pressed by the taper surface of the taper roller, and a taper contact adjusting means for adjusting the degree of contact of the taper with the counter roller ( Claim 2).

(3). In (2), the taper roller is provided so as to be movable in the axial direction (claim 3).

(4). In (2), the opposing roller is a belt driving roller (claim 4).

[0010]

The pressure of the paper transfer bias roller on the intermediate transfer member can be adjusted to a predetermined value.

[0011]

The present invention can be applied to a copying machine using a drum-shaped intermediate transfer member, and can also be applied to a copying machine using a belt-shaped intermediate transfer member. In the following description, an example in which an intermediate transfer belt is used as the intermediate transfer member will be described.

In FIGS. 1 and 2, reference numeral 19 indicates an intermediate transfer belt, which is wound around a belt driving roller 21.

A paper transfer bias roller 23-1 is configured to come into contact with and separate from the belt driving roller 21. That is, the paper transfer bias roller 23-1 is configured as a part of the paper transfer unit 23, and its shaft portion 23-1
a is supported by a movable piece 51 which is slidable in the elongated hole 50.

The moving piece 51 is pressed by a stretchable spring 52. This paper transfer unit 23
Is rotatable about the fulcrum shaft 52, and the eccentric cam 23-3 is in contact with the lower surface of the member opposite to the fulcrum shaft 52.

As a result, the paper transfer unit 23 swings in response to the rotation of the eccentric cam 23-3, and the paper transfer bias roller 23-1 is controlled to come into contact with or separate from the belt drive roller 21 in accordance with the swing. It

In the contact / separation control, the paper transfer bias roller 23-1 is moved upward during transfer and is pressed against the belt drive roller 21 by the elastic force of the spring 52. Under this state, the transfer paper 24 is sent between the intermediate transfer belt 19 and the paper transfer bias roller 23-1, and the toner image 40 on the intermediate transfer belt 19 is conveyed together with the belt and is transferred onto the transfer paper. Transfer is performed.

Reference numeral 21-1 indicates an earth roller, and a transfer bias is applied to the intermediate transfer belt 19 by the paper transfer bias roller 23-1.

The belt driving roller 21 and the paper transfer unit 23 are collectively referred to as a transfer device.

The above is the basic structure of the transfer device. In the present invention, the following structure is added to the basic structure of the transfer device.

In FIGS. 1 and 2, a taper roller 23-4 made of a material which is difficult to deform is rotatably mounted on the shaft portion of the paper transfer bias roller 23-1 via a bearing. Further, the side plate portion of the paper transfer unit 23 is adjusted so as to be in contact with the side portion of the taper roller, and the adjusting screw 23-5.
Is screwed in.

When the paper transfer bias roller 23-1 is in contact with the belt driving roller 21 by the eccentric cam 23-3, the taper roller 23-4 has its inclined surface in contact with the end of the belt driving roller 21. ing.

The taper roller and the adjusting screw as described above are provided on both sides of the paper transfer bias roller 23-1 in the axial direction.

Here, by rotating the adjusting screw 23-5,
The taper roller 23-4 can be moved in the axial direction, and when the taper roller 23-4 is moved to a position closer to the center of the shaft, the taper surface of the taper roller presses the belt drive roller 21 to a greater extent, reducing the gap and pressing force. Can be reduced. If you rotate it in the opposite direction to the above, the spring 5
The force of 2 acts more and the pressing force increases.

Therefore, it becomes possible to adjust the pressing force of the paper transfer bias roller against the intermediate transfer member. Since this adjusting screw is a means for adjusting the contact of the taper, it is called a contact adjusting means. Also, taper roller 23-4
The hit adjusting means is means for adjusting the pressing force of the paper transfer bias roller with respect to the intermediate transfer belt, and is therefore referred to as pressing force adjusting means.

Specifically, as shown in FIG. 1, a taper roller 23-4 is provided with a gap scale, and the pressure is 50 g from the relationship between the gap scale and the pressure shown in FIG.
Make the following adjustments.

Next, regarding the pressing force before and after the axial direction,
In order to reduce the front-to-back difference to 5% or less, as shown in FIG. 4, the gap adjusting piece 23-6 is sandwiched between the front part and the rear part, and the load when the gap adjusting piece is removed by the load measuring device 23-7 is set. Adjust the adjustment screws so that they are equal.

An example in which an opposing roller that opposes the tapered roller is provided will be described with reference to FIG. In this example, as shown in FIG. 5, a counter roller 21-2 is provided on the shaft of the belt driving roller 21 and at a position facing the tapered roller 23-4. The counter roller 21-2 is configured to be rotatable about a shaft via a bearing, but its movement is restricted in the axial direction.

Also in the case of this example, the pressing force can be adjusted in the same manner as the above example in which the counter roller is not used. In the above example, due to the pressing force, the taper roller 23-4 also rotates together with the belt drive roller, the contact surfaces of the taper roller and the belt drive roller change, and the accuracy of these contact surfaces, etc. Pitch-like unevenness is created.

In this respect, in this example, the belt driving roller 2
Since the counter roller 21-2 rotates with respect to the axis of 1, the contact surface between the taper roller and the counter roller does not change, so that there is no uneven pitch on the image as in the above example.

Further, in this example, when the counter roller is worn out by use, only the counter roller can be replaced, which is more convenient than the above example.

The above is an embodiment of the main part of the present invention. Next, a schematic structure of a color copying machine to which the present invention can be applied and a structure around a photoconductor and an intermediate transfer belt will be outlined.

In FIG. 6, 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. And forms an image on the color sensor 7. 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 forms an electrostatic latent image on the photosensitive drum 9.

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 elimination lamp 11, a charger 12, and a potential are provided. Sensor 13, BK developing device 14, C developing device 15, M developing device 16, Y developing device 17,
A developing density pattern detector 18, an intermediate transfer belt 19 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 from a predetermined timing, and based on the image data, optical writing by a laser beam and latent image formation are 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 starts rotating 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.

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 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 unit 19 is stretched around a belt drive roller 21, a transfer bias roller 20, and a driven roller group, and is drive-controlled by a drive motor (not shown).

As shown in FIG. 7, the belt cleaning unit 22 includes a brush roller 22-1 and a rubber blade 2.
2-2, and a contact / separation mechanism 22-3 from the belt, etc., and while belt transfer of the second, third and fourth colors after the first color BK image is transferred by the belt, It is separated from the belt surface by the contact / separation mechanism 22-3.

The area around the paper transfer unit 23 has already been described and will not be described.

The movement of the intermediate transfer belt 19 is 1
There are three possible operation methods after the belt transfer of each color BK toner is completed to the rear end. One of them is possible, or in terms of copy speed or the like depending on the copy size. , 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, the process proceeds to the M, Y image process, and the 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. In the return, the front end position of the BK image on the surface of the intermediate transfer belt 19 passes through the position corresponding to the belt transfer in the opposite direction, and after moving a preset distance, it is stopped and put in a 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.

The intermediate transfer belt 19 is again brought into contact with the surface of the photosensitive drum 9. Also in this case, the C image is transferred onto the intermediate transfer belt 19 under the condition that it accurately overlaps 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 for the first sheet, and then the BK for 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, until the predetermined number of sheets are completed, 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.

[0072]

According to the present invention, it is possible to provide a transfer device of a color copying machine capable of preventing the occurrence of an abnormal image.

[Brief description of drawings]

FIG. 1 is a front view illustrating a main part of a transfer device according to the present invention.

FIG. 2 is a side view illustrating a main part of a transfer device according to the present invention.

FIG. 3 is a diagram illustrating a relationship between a gap and a pressing load.

FIG. 4 is a perspective view illustrating a means for adjusting a front and rear gap.

FIG. 5 is a front view illustrating a main part of a transfer device according to the present invention.

FIG. 6 is a schematic configuration diagram of a color copying machine suitable for carrying out the present invention.

FIG. 7 is an explanatory diagram showing an enlarged part of FIG. 6;

[Explanation of symbols]

 19 Intermediate transfer belt 23-1 (as an intermediate transfer member) Paper transfer bias roller 23-4 Tapered roller 23-5 (as a pressing force adjusting means) Adjustment screw (as a pressing force adjusting means)

Claims (4)

[Claims] 1. A transfer device of a color copying machine for transferring a toner image onto a transfer paper via an intermediate transfer body, comprising a pressing force adjusting means for adjusting a pressing force of a paper transfer bias roller against the intermediate transfer body to a predetermined value. A transfer device for a color copying machine characterized by being provided. 2. The intermediate transfer member according to claim 1, wherein the intermediate transfer member is a belt, and a belt driving roller that supports the belt is in pressure contact with the paper transfer bias roller via the belt, and the pressing force adjusting means comprises: A taper roller provided coaxially with the paper transfer bias roller, a counter roller coaxial with the belt drive roller that is pressed by the taper surface of the taper roller, and a taper contact that adjusts the degree of taper contact of the taper roller with the counter roller. A transfer device for a color copying machine, which comprises an adjusting means. 3. A transfer device of a color copying machine according to claim 2, wherein the taper roller is provided so as to be movable in the axial direction. 4. The transfer device for color copying paper according to claim 2, wherein the counter roller is a belt driving roller.