JP2002357938A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent paper powder from being mixed in recycled toner recovered by an image carrier cleaning device in a tandem type image forming device. SOLUTION: This color image forming device is equipped with an intermediate transfer belt 20 having a traveling surface arranged extending over all of four image carriers 2 in order to hold respective color toner images successively transferred from four image carriers 2, a primary transfer device 6 primarily transferring the respective toner images on the respective image carriers to the belt 20, a secondary transfer device 30 collectively transferring the respective toner images primarily transferred to the belt 20 to transfer material in non-contact with the image carriers, and cleaning devices 7 respectively provided for the respective image carriers in order to clean the respective image carriers after transfer. The device is equipped with a toner recycle mechanism 40 for recycling toner removed and recovered from the image carrier by the device 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electrophotographic color image forming apparatus such as a color copying machine, a color printer, and a color facsimile apparatus, and more particularly, to an image forming unit having the same number of color toners as the number of color toners to be used. The present invention relates to a tandem type color image forming apparatus.

[0002]

2. Description of the Related Art As an image forming apparatus for forming a full-color image by an electrophotographic process, an apparatus using four color toners of black, yellow, magenta and cyan is known, and FIG. 2 is disclosed in JP-A-2000-206755. 1 shows a type provided with four image forming units called a tandem type. In FIG.
B, 1Y, 1M, and 1C are image forming units dedicated to black, yellow, magenta, and cyan, respectively. Each image forming unit includes an image carrier (photosensitive drum) 2B,
2Y, 2M, 2C and charging units 3B, 3Y, 3M, 3C
And exposure units 4B, 4Y, 4M, and 4C, and development units 5B and 5B.
Y, 5M, 5C and transfer devices 6B, 6Y, 6M, 6C
And cleaning devices 7B, 7Y, 7M, 7C. Further, each image forming unit 1B, 1Y, 1
An intermediate transfer belt 10 composed of an endless belt is stretched by rollers 11 so as to straddle M and 1C. Further, a fixing device 13 is disposed downstream of the intermediate transfer belt 10 in the running direction via an intermediate conveyance belt 12. A registration roller 14 is disposed upstream of the intermediate transfer belt 10 in the traveling direction.

In each image forming unit, an electrostatic latent image is formed by irradiating optical image information such as reflected light of a document from an exposure unit onto a surface of an image carrier which has been uniformly charged in advance by a charging unit. Subsequently, in each image forming unit, any one of black, yellow, magenta, and cyan toners is supplied from the developing unit to the electrostatic latent image and developed to form a toner image. The transfer paper P as a transfer material is conveyed from a paper supply unit (not shown), and is fed by a registration roller 14 to the transfer device 6B of the black image forming unit 1B located at the most upstream portion at a predetermined timing. The transfer paper P is sequentially conveyed downstream by the running surface of the intermediate transfer belt 10,
Each transfer device 6B, 6Y, 6M, 6 that passes in the process of transport
C, the image carriers 2B, 2
The toner images of the respective colors on Y, 2M and 2Y are superimposed and transferred.
The transfer paper P having received the superimposed transfer of the toner image is transferred to a fixing device 13.
And is fixed. In this conventional example, the black image forming unit 1B is arranged at the most upstream position in the rotation direction of the intermediate transfer belt 10, and the toner collected by the cleaning device 7B is returned to the developing unit 5B for reuse. Each of the magenta and cyan image forming units 1Y, 1M, and 1Y is disposed at a downstream position, and the toner collected from each image carrier is discarded. Then, only when a double-sided copy is performed, after the superimposed toner image for the back surface is transferred onto the intermediate transfer belt 10, the superimposed toner image is collectively transferred to the back surface of the transfer paper at the back surface transfer position. The transfer method in this conventional image forming apparatus is basically a direct transfer to transfer paper, and is a paper transport path in which the transfer paper directly contacts the image carrier. In the above-described conventional color image forming apparatus, in the image forming unit located at the most upstream position in the rotation direction of the intermediate transfer belt, toner is recycled, and another image forming unit is disposed at the downstream position to collect toner. Disposal solves the problem of color mixing of recycled toner.However, when an image is formed on the surface of the transfer paper, the transfer paper becomes a transport path that directly contacts the image carrier. Further, there is a problem that the paper dust adheres to the image carrier and the paper dust is mixed in the recycled toner collected by the image carrier cleaning device.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and a secondary transfer device for collectively transferring a color image to transfer paper irrespective of single-sided copy or double-sided copy is provided with transfer paper. It is disposed at a position on the intermediate transfer body where the image carrier is not in direct contact, and the paper dust on the intermediate transfer body is removed by an intermediate transfer body cleaning device or a secondary transfer cleaning device. An object of the present invention is to provide a color image forming apparatus in which paper dust is prevented from being mixed into collected recycled toner. Another object of the present invention is to provide a color image forming apparatus,
In the image forming unit located at the most upstream position in the rotation direction of the intermediate transfer body, the toner is recycled, and another image forming unit is arranged at the downstream position to collect and discard the toner. Is to solve. Another object of the present invention is to provide a color image forming apparatus, wherein a black image forming unit is disposed at a most upstream position in a rotation direction of the intermediate transfer body to recycle toner, and to form yellow, magenta, and cyan images. An object of the present invention is to solve the problems of mixing of other colors and mixing of paper dust with respect to recycling of the most frequently used black toner by disposing the forming unit at a downstream position and collecting and discarding the toner.

[0005]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to yellow, magenta, cyan,
Four image carriers that respectively carry black toner images of each color and rotate, and are arranged across all the image carriers to hold the toner images of each color sequentially transferred from each image carrier. An intermediate transfer belt having a running surface, a primary transfer device that primarily transfers each toner image on each image carrier onto the intermediate transfer belt, and an image of each toner image primarily transferred onto the intermediate transfer belt. A secondary transfer device that collectively transfers to the transfer material in a non-contact manner with the carrier, a cleaning device provided for each image carrier to clean each image carrier after transfer,
And a toner recycling mechanism for recycling the toner removed and collected from the image carrier by the cleaning device. According to a second aspect of the present invention, toner removed and recovered by the cleaning device from the image carrier located at the most upstream part in the running direction of the intermediate transfer belt is recycled by the toner recycling mechanism, and each of the toners located on the other downstream side is removed. It is characterized in that the toner removed and recovered from the image carrier by each cleaning device is discarded. Claim 3
In the invention, the image carrier located at the most upstream part in the running direction of the intermediate transfer belt is an image carrier for black.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 is a schematic diagram illustrating a main configuration of a color image forming apparatus according to an embodiment of the present invention. As shown in the conventional example of FIG. 2, each of the image carriers 1B, 1Y, 1M, and 1 is provided in a tandem type electrophotographic image forming apparatus.
The transfer device 6B, 6Y, 6M, 6
1C, a direct transfer system in which images are directly transferred onto a transfer sheet P conveyed by an intermediate transfer member (transfer sheet conveying belt) 3 sequentially;
As shown in the embodiment, each of the image carriers 1B, 1Y, 1Y
The primary transfer devices 6B, 6Y, 6 transfer the toner images on M, 1C.
Intermediate transfer belt (intermediate transfer body) once by M and 6C
There is an indirect transfer type in which the superimposed toner images on the intermediate transfer belt 20 are collectively transferred onto the transfer paper P by the secondary transfer device 30 after being sequentially superimposed and transferred onto the transfer paper 20. The image forming apparatus of the indirect transfer type shown in FIG.
Magenta and cyan image forming units 1B, 1Y,
1M, 1C, and each image forming unit includes an image carrier (photoconductor drum) 2B, 2Y, 2M, 2C, a charging unit 3B, 3Y, 3M, 3C, an exposure unit 4B, 4Y, 4M,
4C, developing units 5B, 5Y, 5M, 5C, and transfer device 6
B, 6Y, 6M, 6C and image carrier cleaning device 7
B, 7Y, 7M, and 7C, and a toner recycling mechanism 40 provided in at least one image forming unit. The toner recycling mechanism 40 is provided, for example, in the most upstream image forming unit 1B, and
A transport mechanism is provided for returning the toner collected from B to the developing device 5B for recycling. Further, an intermediate transfer belt 20 composed of an endless belt extends across the image forming units 1B, 1Y, 1M, and 1C.
It is stretched by. A secondary transfer device 30 is disposed on a running surface of the intermediate transfer belt that does not contact any of the image carriers. A fixing device 32 is disposed downstream of the intermediate transfer belt 20 in the traveling direction with an intermediate conveyance belt 31 interposed therebetween. A registration roller 33 is disposed upstream of the intermediate transfer belt 20 in the traveling direction. Reference numeral 35 denotes an intermediate transfer belt cleaning device. The transfer paper P fed from a paper feeding device (not shown)
3, the toner is supplied to the secondary transfer device 30 at a predetermined timing, and the superimposed toner image on the intermediate transfer belt 20 is collectively transferred.

In each of the image forming units, an electrostatic latent image is formed by irradiating optical image information such as original reflected light from the exposure unit onto the surface of the image carrier which has been uniformly charged in advance by the charging unit. Subsequently, in each image forming unit, black, yellow, magenta,
A toner image of any one of cyan and cyan is supplied and developed to form a toner image. Each toner image on each image carrier is sequentially transferred onto the intermediate transfer belt 20 in a superimposed manner. The transfer paper P as a transfer material is conveyed from a paper feeding device (not shown), and is fed to the secondary transfer device 30 by a registration roller 33 at a predetermined timing. The transfer paper P to which the collective transfer of the superimposed toner image has been transferred is conveyed to the fixing device 32 to be fixed.

[0008] Comparing the direct transfer system shown in FIG. 2 with the indirect transfer system shown in FIG.
B, 1Y, 1M, and 1C, the paper feeder must be disposed upstream of the tandem image forming apparatus in which the fixing device 13 is disposed downstream, and the transfer paper transport direction becomes large in size. is there. On the other hand, in the latter case, the layout of the secondary transfer device 30 can be selected relatively freely. The paper feeding device and the fixing device 32 can be disposed so as to overlap with the tandem image forming device, and there is an advantage that the size can be reduced. In the former type, the fixing device 13 is disposed close to the tandem-type image forming apparatus in order not to increase the size in the transfer paper transport direction. Therefore, the transfer paper P
The fixing device 13 has a sufficient margin to bend.
Cannot be arranged, and the leading end of the transfer paper P is
3 due to an impact (particularly remarkable with thick transfer paper) when entering the transfer paper 3 and a speed difference between the transfer paper conveyance speed when passing through the fixing device 13 and the transfer paper conveyance speed by the transfer conveyance belt 13. 13 has a disadvantage that it easily affects the image forming quality on the upstream side. On the other hand, in the embodiment of the present invention shown in FIG. 1, the fixing device 32 is freely arranged with a sufficient margin for the transfer paper P to bend even if the size of the transfer paper P is prevented from being increased in the transport direction. Therefore, the fixing device 32 can hardly affect image formation.

From the above, recently, attention has been paid to a tandem-type image forming apparatus, particularly an indirect transfer type. In this type of color image forming apparatus, as shown in FIG. 1, transfer residual toner remaining on each of the image carriers 2B to 2C after each primary transfer by each of the transfer devices 6B to 6C is transferred to each image carrier. The surfaces are removed by the cleaning devices 7B to 7C to clean the surfaces of the respective image carriers, and the images are prepared for image formation again. Further, the transfer residual toner remaining on the intermediate transfer belt 20 after the secondary transfer is removed by the intermediate transfer body cleaning device 35 to clean the surface of the intermediate transfer belt 20 and prepare for the image formation again. Then, the black image forming unit 1B is disposed at the most upstream position in the rotation direction of the intermediate transfer belt 20, and the toner recovered by the black image carrier cleaning device 7B by the toner recycling mechanism 40 (recycling to the developing device). Collection), and the yellow, magenta, and cyan image forming units 1Y, 1M, and 1C are disposed at downstream positions to collect and collect toner.
By disposing, the image carrier cleaning device 7B
To prevent paper powder from being mixed in or mixed with the black recycled toner collected in step (1).

[0010]

As described above, the first aspect of the present invention relates to a secondary transfer device in a tandem type color image forming apparatus provided with the same number of image carriers (image forming units) as the number of toner colors to be used. Is disposed at a position where the transfer paper does not directly contact the image carrier, and the paper dust on the intermediate transfer body is removed by an intermediate transfer body cleaning device or a secondary transfer cleaning device. Paper powder can be prevented from being mixed into the recycled toner. According to the second aspect of the present invention, in the image forming unit located at the most upstream position in the rotation direction of the intermediate transfer body, the collected toner is recycled, and another image forming unit is disposed at the downstream position to collect the toner. In addition, color mixing of recycled toner can be prevented. According to a third aspect of the present invention, a black image forming unit using the most frequently used toner is disposed at the most upstream position in the rotation direction of the intermediate transfer body to recycle the toner, and to form yellow, magenta, and cyan images. By disposing the forming unit at the downstream position and collecting and discarding the toner, if the most frequently used black toner is collected for recycling, there is a problem of mixing of other color toners and mixing of paper dust. Can be solved

[Brief description of the drawings]

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

FIG. 2 is a configuration explanatory view of a conventional color image forming apparatus.

[Explanation of symbols]

 1B, 1Y, 1M, 1C Image forming unit 2B, 2Y, 2M, 2C Image carrier 3B, 3Y, 3M, 3C Charging unit 4B, 4Y, 4M, 4C Exposure unit 5B, 5Y, 5M, 5C Developing unit 6B, 6Y , 6M, 6C transfer device 7B, 7Y, 7M, 7C image carrier cleaning device 20 intermediate transfer belt 21 roller 30 secondary transfer device 31 transport belt 32 fixing device 33 registration roller 40 toner recycling mechanism

Claims (3)

[Claims] 1. An image forming apparatus comprising: four image carriers which respectively carry yellow, magenta, cyan, and black toner images and rotate; and a toner image of each color which is sequentially transferred from each image carrier. An intermediate transfer belt having a running surface disposed across all image carriers, a primary transfer device for primary-transferring each toner image on each image carrier onto the intermediate transfer belt, and the intermediate transfer belt A secondary transfer device that collectively transfers the toner images primary-transferred onto the transfer material in a non-contact manner with the image carrier, and an image carrier for cleaning the image carriers after the transfer, respectively. A color image forming apparatus, comprising: a cleaning device provided with a toner recycling mechanism that recycles toner removed and collected from an image carrier by the cleaning device. 2. The image forming apparatus according to claim 1, wherein the toner recycle mechanism recycles toner removed and recovered by the cleaning device from an image carrier positioned at the most upstream portion in the running direction of the intermediate transfer belt, and further includes other image carriers located downstream. 2. The color image forming apparatus according to claim 1, wherein the toner removed from the body by each cleaning device is discarded. 3. The color image forming apparatus according to claim 2, wherein the image carrier located at the most upstream part in the running direction of the intermediate transfer belt is a black image carrier.