JP2003029540A - Color image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce adverse effect of heat generated in each unit of an image forming section during image formation on both sides and decrease energy consumption in a fixing section during image formation on the back, in an electrophotographic color image forming apparatus having an intermediate transfer belt. SOLUTION: The color image forming apparatus has an intermediate transfer belt 5 which holds a toner image intermediately transferred from the surface of a photoreceptor 61, and a fixing section 8 which heat-fixes transfer paper with the toner image transferred from the surface of the intermediate transfer belt. The color image forming apparatus is provided with a fan 12 that is located near an intermediate transfer belt and downstream from the position of the paper transfer and that cools the surface of the intermediate transfer belt by sending air to the surface of the belt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature rise of an intermediate transfer belt equipped in a color image forming apparatus and a color image forming apparatus capable of solving various problems caused by the temperature rise.

[0002]

2. Description of the Related Art In recent years, in order to protect the environment and effectively use resources, in image forming apparatuses such as copying machines, printers, and printing machines, paper resources are saved by double-sided printing or the apparatus is in operation. It is required to save energy by reducing energy consumption. The electrophotographic color image forming apparatus has a configuration in which photoconductor drums for each color of yellow, cyan, magenta, and black are arranged adjacent to each other, and a dedicated charger, exposure unit,
A developing device, a cleaning device, etc. are arranged. Also,
As the transfer means, an endless intermediate transfer belt in which one running surface is closely arranged so as to straddle each photoconductor and a transfer bias applying means are used, and the toner image formed on each photoconductor is transferred to the intermediate transfer belt. After transferring on top of one another,
The superposed toner images are collectively transferred onto a transfer paper and then fixed. When performing double-sided printing in a color image forming apparatus having such a configuration, a step of performing image formation on one side of a transfer sheet and subsequently performing image formation on the back side thereof is performed. That is, after the transfer paper on which the toner image is transferred from the photoconductor is heated and pressed in the fixing device, the same process for forming an image on the back of the transfer paper is performed. When this double-sided image forming operation is continuously performed, the transfer paper once heated in the fixing device comes into contact with the intermediate transfer belt during the transfer operation in the back side image forming operation, so that heat is transferred from the transfer paper to the intermediate transfer belt. Temperature rises. When the temperature of the intermediate transfer belt rises above 50 ° C., the intermediate transfer belt expands, causing problems such as deformation of the toner image on the intermediate transfer belt. In addition, the temperature of the photosensitive member and the intermediate transfer belt cleaning section which are in contact with the intermediate transfer belt also rises.
Further, the temperature of the developing unit and the photoconductor cleaning unit in contact with the photoconductor also rises. When the temperatures of the developing unit, the photoconductor cleaning unit, and the intermediate transfer belt cleaning unit rise to 50 ° C. or higher, the toner may be blocked (toner is solidified). However, since the transfer paper is sufficiently heated by the fixing operation during image formation on the front surface, a large amount of heat is not required during the fixing operation during image formation on the back surface.

[0003]

In order to solve such a problem, there has been proposed a structure in which a heat pipe is provided in the downstream conveying path of the fixing section to cool the passing transfer paper. In this case, Since the transfer paper is cooled by the heat pipe immediately after the fixing on the front surface, the above-mentioned problems caused by the temperature rise of each portion at the time of image formation on the back surface can be reduced. However, since it is necessary to heat the transfer paper once cooled by the heat pipe after fixing on the front surface until the temperature (160 ° C. or higher) at which the transfer paper can be fixed again at the time of image formation on the rear surface,
A large amount of energy is required in the fixing unit even when the image is formed on the back surface. The present invention has been made in view of the above, and in an electrophotographic color image forming apparatus equipped with an intermediate transfer belt, when performing double-sided image formation, heat generated by each unit forming an image forming unit is reduced. An object of the invention is to reduce adverse effects and reduce energy consumption in a fixing unit during image formation on the back surface.

[0004]

In order to solve the above-mentioned problems, the invention of claim 1 is directed to an intermediate transfer belt carrying a toner image intermediately transferred from a photoconductor, and a toner image from the intermediate transfer belt. In a color image forming apparatus including a fixing unit that thermally fixes a transfer sheet that has undergone paper transfer, in the vicinity of the intermediate transfer belt, the intermediate transfer belt surface is provided on the downstream side of the position where the paper transfer is performed. It is characterized in that a fan is provided for cooling the air by blowing the air into. According to a second aspect of the present invention, there is provided an intermediate transfer belt carrying a toner image intermediately transferred from the photoconductor, and a fixing section for thermally fixing the transfer paper having the toner image transferred on the intermediate transfer belt. In the color image forming apparatus, in the vicinity of the intermediate transfer belt and on the downstream side of the position where the paper transfer is performed, a heat pipe that comes into contact with the belt surface of the intermediate transfer belt and heat radiated from the heat pipe are radiated. And a fan that blows air to the fins to cool the fins.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a schematic configuration diagram of an example of a color image forming apparatus to which the present invention is applied. An image forming unit 1 is arranged at substantially the center of the color image forming apparatus, and the image forming unit 1 is provided immediately below the image forming unit 1. The paper unit 2 is arranged. The sheet feeding unit 2 includes a sheet feeding cassette 21 in each stage. If necessary, another sheet feeding device 22 can be added. A reading unit (reading optical system) 3 for reading a document image is arranged above the image forming unit 1. A discharged paper storage unit 4 is arranged on the left side of the image forming unit 1, and the transfer paper on which an image is formed is discharged and stored therein. In the image forming unit 1, an intermediate transfer belt 5 as a belt-shaped intermediate transfer member is stretched endlessly along a predetermined traveling path, and is driven in the arrow direction by each support roller. Four image forming units 6 are arranged along the upper running surface of the intermediate transfer belt 5. In each of the image forming units 6, around the drum-shaped photosensitive member 61, a charging device 62 for charging the surface of the photosensitive member, an exposure device 7 for irradiating the surface of the photosensitive member with laser light for image information, and a photosensitive member. Two developing devices 63 for visualizing the electrostatic latent image formed by being exposed on the surface of the sheet, and a cleaning device 64 for removing and collecting the toner remaining on the photoconductor.
Are arranged, and as an image forming process, the intermediate transfer belt 5 rotates to form one color image.
First, the yellow (Y) image forming unit develops yellow (Y) toner and transfers it to the intermediate transfer belt. Next, the magenta (M) image forming unit develops the magenta toner,
Transfer to the intermediate transfer belt. Next, in the cyan (C) image forming unit, cyan toner is developed and transferred to the intermediate transfer belt, and finally, black (BK) toner is developed and transferred to the intermediate transfer belt. On the lower running surface of the intermediate transfer belt 5, which is different from the upper running surface of the intermediate transfer belt to which each image forming unit 6 is adjacent, the image is transferred to the intermediate transfer belt 4 overlaid.
A transfer device (paper transfer device) 51 for transferring a color toner image onto a transfer paper, and an intermediate transfer cleaning device 52 for removing and collecting the toner remaining on the surface of the intermediate transfer belt after the transfer are respectively arranged.

A fixing device (fixing section) 8 is provided for fixing the toner image by passing the transfer paper on which the superimposed toner image has been transferred by the transfer device 51. The transfer paper that has passed through the fixing device 8 is discharged and stored in the discharge storage unit 4 by the discharge roller 41. During double-sided printing, after the transfer paper having the image formed on the front surface side passes through the fixing device 8, the paper is not immediately ejected and the double-sided device 9 positioned at the lower side at the branch portion (branching claw) 91. Side, the transfer paper is inverted via this,
The skew of the transfer sheet is corrected by the registration roller 23, and the back side image forming operation is performed. In the paper feed unit 2, unused transfer paper is stored in the paper feed cassette 21, and the bottom plate rotatably supported rises to a position where the uppermost transfer paper can come into contact with the pickup roller. The uppermost sheet is sent out from the sheet feeding cassette by the rotation of the sheet feeding roller and is conveyed to the registration roller 23. The registration rollers 23 are controlled so as to temporarily stop the conveyance of the transfer paper and start the rotation at a timing so that the positional relationship between the toner image on the surface of the photoconductor and the front end of the transfer paper becomes a predetermined position. Reading unit 3
Then, in order to read and scan a document (not shown) placed on the contact glass 31, the reading traveling bodies 32 and 33 composed of a document illumination light source and a mirror reciprocate. The image information scanned by the reading carriages 32 and 33 is transferred to the CCD 3 installed behind the lens 34.
5 is read as an image signal. The read image signal is digitized and image-processed. Based on the image-processed signal, the laser diode LD (not shown) in the exposure device 7 emits light to form an electrostatic latent image on the surface of the photoconductor 61. The optical signal from the LD reaches the photoconductor through a known polygon mirror or lens. Above the reading unit 3, an automatic document feeder 36 that automatically conveys a document onto the contact glass is attached.

The color image forming apparatus according to the present embodiment has a function as a so-called digital color copying machine for scanning and reading an original, digitizing and copying it onto a transfer sheet as described above, and a control device (not shown). The multifunctional image forming apparatus has a facsimile function of transmitting and receiving image information of a document to a remote place and a so-called printer function of printing image information handled by a computer on a transfer paper. Images formed by any of the functions are all discharged and stored in one discharged sheet storage section 4. When the transfer paper is branched by the branching claw 91 and is reversed through the double-sided device 9 and is discharged from the discharge roller 41 through the reverse discharge roller, the transfer paper stacked in the discharge storage unit is the image surface. Even though the originals handled by copying, facsimile, and printer are printed from page 1 and printed, the first page is topmost when it is taken out from the paper output storage section. , You are freed from work such as aligning pages again.

Next, a characteristic constitution of the present invention is a constitution for preventing the trouble that the heat of the fixing device 8 is transferred to the image forming section 6 through the transfer paper and exerts a bad influence. First, the characteristic configuration of the present invention corresponding to claim 1 is that, in the color image forming apparatus shown in FIG. 1, a fan that sends cooling air of the intermediate transfer belt to the vicinity of the intermediate transfer belt 5 to cool it. 12 is provided. The cooling fan 12 is arranged so as to face the belt surface on the downstream side of the transfer device 51, and is configured to directly blow cooling air over the entire width direction of the intermediate transfer belt to cool it while the intermediate transfer belt is running. .
In particular, by operating the fan 12 when performing double-sided printing, the belt 5 is heated to 50 ° C. or more and expanded by heat from the transfer paper during image formation on the back surface, and other components contacting the belt 5 ( It is possible to solve the problem that the temperature of the developing unit, the photoconductor cleaning unit, the intermediate transfer belt cleaning unit) rises, and toner blocking occurs. Furthermore, since the transfer paper having the image fixed on the front surface is not excessively cooled after the fixing, it is not necessary to output a large fixing energy when fixing the image on the rear surface. In other words, since it is not a method of directly cooling the transfer paper,
It is possible to reduce the drop in the temperature of the transfer paper, and it is possible to reduce the energy consumption when fixing the back surface.

Next, in the embodiment corresponding to claim 2 shown in FIG. 2, in the vicinity of the intermediate transfer belt 5 and on the downstream side of the position 51 where the paper transfer is performed, the belt surface of the intermediate transfer belt is provided. The heat pipe 13 that comes into contact with the heat pipe 13
It is characterized in that a fin 14 for radiating heat from the fan 14 and a fan 15 for blowing air to the fin 14 to cool the fin 14 are provided. In the illustrated example, the heat pipe 13 is provided so as to come into contact with an appropriate place of the intermediate transfer belt 5, for example, the lower traveling surface which is the downstream side of the paper transfer position 51, and is provided behind the heat pipe 13 (outside the rear side plate). , Providing a fin 14 for heat dissipation,
The fins 14 are configured to be cooled by the fan 15. In this way, the heat pipe 13 is provided so as to come into contact with the intermediate transfer belt 5, and behind the heat pipe 13,
Since the fins 14 are provided and the fins 14 are cooled by the fan 15, the function of cooling the intermediate transfer belt 5 is further improved. The heat pipe 13 is a pipe in which the inside of the pipe is in a vacuum state, the working fluid is inserted therein, and the seal is completely sealed. When heat is transferred to the fluid, the heat pipe 13 is vaporized to become vapor,
Go to the end of the pipe and back into the fluid. At that time, the heat is discharged to the outside, and the repetition is repeated for a short time. When performing double-sided printing, by operating the fan 12 to cause the heat pipe 13 and the fins 14 to function, the belt 5 is heated to 50 ° C. or more by the heat from the transfer paper when the image is formed on the back surface, and the belt 5 expands. It is possible to solve the problem that the other components (the developing unit, the photoconductor cleaning unit, the intermediate transfer belt cleaning unit) that are in contact with No. 5 are heated and cause toner blocking or the like. Furthermore, since the transfer paper having the image fixed on the front surface is not excessively cooled after the fixing, it is not necessary to output a large fixing energy when fixing the image on the rear surface. That is, since the transfer paper is not directly cooled, it is possible to reduce the temperature drop of the transfer paper and reduce the energy consumption at the time of fixing the back surface.

[0010]

As described above, according to the present invention, in an electrophotographic color image forming apparatus equipped with an intermediate transfer belt, when double-sided image formation is performed, it occurs in each unit forming an image forming unit. It is possible to reduce adverse effects caused by heat and to reduce energy consumption in the fixing unit during image formation on the back surface. That is, in the invention of claim 1,
A fan is provided near the intermediate transfer belt to cool the intermediate transfer belt by blowing air directly, so it is possible to prevent temperature rise due to contact between the transfer paper and the intermediate transfer belt during double-sided image formation. Since the expansion of the transfer belt, the blocking of the toner in the developing portion and the cleaning portion can be prevented and the drop in the transfer paper temperature can be reduced, the energy consumption at the time of the back surface fixing can be reduced. In the invention of claim 2,
Since the heat pipe is provided so as to be in contact with the intermediate transfer belt, and the fin is provided at a proper position of the heat pipe, for example, the fin is cooled by the fan, the influence of heat can be further reduced as compared with the case of the first aspect.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a color image forming apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

1 image forming unit, 2 paper feeding unit, 3 reading unit, 5 intermediate transfer belt, 6 image forming unit, 8 fixing device, 9 double-sided device, 12 fan, 13 heat pipe, 14 fins, 15 fan, 51 transfer device ( Paper transfer device), 5
2 intermediate transfer cleaning device, 61 photoconductor, 62
Charging device, 63 developing device, 64 cleaning device.

Claims (2)

[Claims] 1. An intermediate transfer belt carrying a toner image intermediately transferred from a photoconductor, and a fixing unit for thermally fixing a transfer paper having a toner image paper transferred from the intermediate transfer belt.
In a color image forming apparatus provided with, a fan for blowing air to the surface of the intermediate transfer belt to cool the intermediate transfer belt is provided downstream of the position where the paper transfer is performed. And a color image forming apparatus. 2. A color comprising: an intermediate transfer belt carrying a toner image intermediately transferred from a photosensitive member; and a fixing unit for thermally fixing the transfer paper on which the toner image is transferred on the intermediate transfer belt. In the image forming apparatus, in the vicinity of the intermediate transfer belt, on the downstream side of the position where the paper transfer is performed, a heat pipe that contacts the belt surface of the intermediate transfer belt, and a fin that radiates heat from the heat pipe. And a fan that blows air to the fins to cool the fins.