JPH1115227A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the device small in size and installation area, short in transfer-paper carrying path, high in image output speed and improved in transfer-paper carry performance by specifying the length of the transfer-paper carrying path, from a registration roller to the first one of image carriers where transfer paper first comes. SOLUTION: Image forming units 21B, 21M, 21Y, and 21C for forming images in a plurality of separate colors, for example Bk, M, Y, and C, are arranged in a vertical direction T. The length of the transfer-paper carrying path, from the registration roller 31 to the first-color photoreceptor (the photoreceptor to which the transfer paper first comes) 22Bk, is made shorter than half the length of the passable smallest-side transfer-paper in the direction where the paper is passed. Therefore, because even when paper which is thin or small in size is passed as the transfer paper, the front end of the transfer paper is surely carried into a nip between the carrying transfer belt 26 and the first-color photoreceptor 22Bk, the transfer-paper carry performance improves, and a trouble, such a paper jam, and image-quality degradation due to rub of an unfixed image is not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image using a plurality of image carriers.

[0002]

2. Description of the Related Art Full-color images are formed by forming images of a plurality of colors, for example, yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), cyan (hereinafter referred to as C), and black (hereinafter referred to as Bk). As an image forming apparatus for forming an image, an image of each color of Y, M, C, and Bk is formed on a photoconductor, and Y, M, and C on these photoconductors are formed.
2. Description of the Related Art A tandem type image forming apparatus that forms a full-color image by sequentially superimposing and transferring images of respective colors of M, C, and Bk on transfer paper is known.

FIG. 5 shows an example of a tandem type image forming apparatus. Image forming units 1Y, 1M, 1C, and 1Bk for forming images of respective colors of Y, M, C, and Bk are horizontally arranged.
Bk denotes drum-shaped photoconductors 2Y, 2M, 2C,
2Bk, charging devices 3Y, 3M, 3C, 3Bk, developing devices 4Y, 4M, 4C, 4Bk, cleaning devices 5Y, 5Y
M, 5C, 5Bk, etc.

The photoconductors 2Y, 2M, 2C, and 2Bk are arranged in a horizontal direction facing the transfer belt 6, and are rotated by a motor. The photosensitive members 2Y, 2M, 2C, 2
Bk represents the charging devices 3Y, 3M, 3C, and 3Bk, respectively.
After being uniformly charged, the photosensitive member is exposed to light by an exposure means 7 comprising an optical writing device to form an electrostatic latent image.

The optical writing device 7 drives the semiconductor lasers 8Y, 8M, 8C and 8Bk with the semiconductor laser driving circuit based on image signals of respective colors of Y, M, C and Bk.
The laser beams from Y and 8Bk are deflected and scanned by the polygon mirror 9, and the laser beams from the semiconductor lasers 8M and 8C are deflected and scanned by the polygon mirror 10.
The respective laser beams from the polygon mirrors 9 and 10 are transmitted to the fθ lenses 11Y, 11M, 11C and 11Bk and the mirror 12
Y, 12M, 12C, 12Bk, 13Y, 13M, 13
By irradiating the photoconductors 2Y, 2M, 2C, and 2Bk via C, 13Bk, 14Y, 14M, 14C, and 14Bk, the photoconductors 2Y, 2M, 2C, and 2Bk are exposed to form electrostatic latent images.

The electrostatic latent images on the photoconductors 2Y, 2M, 2C, and 2Bk are developed by developing devices 4Y, 4M, 4C, and 4B, respectively.
The toner image of each color of Y, M, C and Bk is developed by k. On the other hand, transfer paper such as plain paper or an OHP sheet is fed from the paper feeding device 15 to the registration roller 16, and the registration roller 16 applies the transfer paper to the toner image on the photoconductor 2Y in the image forming unit 1Y for the first color and the leading end. At the same time, it is sent to the transfer belt 6.

The transfer paper sent from the registration rollers 16 is adsorbed and conveyed by the conveyance transfer belt 6, and
Y, M, C, Bk on photoconductors 2Y, 2M, 2C, 2Bk
Transfer means 17 for transferring toner images of each color by a corona discharger
Y, 17M, 17C, and 17Bk are sequentially superimposed and transferred to form a full-color image. The transfer paper is fixed with a full-color image by a fixing device 18, and is discharged to a discharge unit 20 by a discharge roller 19. Further, the photoconductors 2Y, 2M, 2C, and 2Bk are cleaned by the cleaning devices 5Y, 5M, 5C, and 5Bk after the transfer of the toner image, and are ready for the next image forming operation.

In such a tandem type image forming apparatus, in order to prevent image quality deterioration due to color misregistration at the time of outputting a full-color image, the transfer paper is firmly fixed to the transport transfer belt and the transfer paper and the transport transfer belt are fixed. It is necessary to make sure that they do not shift. Therefore, Japanese Patent Application Laid-Open No. H8-19435
As described in Japanese Patent Application Laid-Open No. H08-328395 and Japanese Patent Application Laid-Open No. H8-328395, a suction unit for suctioning a transfer paper to a transfer belt is provided upstream of a transfer unit for transferring a first color toner image onto the transfer paper in a transfer paper transfer direction. In some cases.

However, when a high-resistance transfer belt is used, the transfer paper is electrostatically attracted to the transfer belt by transferring the first color toner image onto the transfer paper. Good. An image forming apparatus (Ricoh PRETER 750) having a configuration that does not actually have a suction unit has been commercialized.

On the other hand, when a black-and-white image is output in a tandem-type image forming apparatus, the same operation as in the case of outputting a full-color image is performed. Since the deterioration of the agent and the photoreceptor is accelerated, the running cost increases, which is not economical.

In order to solve such a problem, Japanese Patent Application Laid-Open No. Hei 8-194351 discloses that Bk is used when outputting a black and white image.
A method for stopping a developing device other than the developing device is shown. This method can prevent the color developer from deteriorating due to agitation in the developing device, but because the photoreceptor is operating, friction and electrostatic fatigue between the photoreceptor and the transfer paper or contact charging device, etc. Deterioration of the photoreceptor cannot be prevented.

Japanese Patent Application Laid-Open No. Hei 5-341617 discloses a method of providing a bypass conveyance path dedicated to black and white image output. According to this method, a black-and-white image can be output without deteriorating the color image forming unit. However, the apparatus becomes complicated, and when a full-color image is output, the Bk image is converted into Y, M, and C images. It is difficult to accurately align the position on the transfer paper. JP-A-8-328395 discloses that
In a tandem type image forming apparatus in which a plurality of photoconductors are arranged in a horizontal direction, a method of separating a transfer belt from a photoconductor other than a Bk photoconductor among a plurality of photoconductors when outputting a black and white image is shown. .

[0013]

In recent years, in an image forming apparatus, not only the apparatus main body is reduced in size but also the space occupied by the machine is reduced so that a paper feed tray, a paper discharge tray, etc., do not protrude from the main body. A wingless type image forming apparatus is desired. In recent years, networking and colorization of offices and homes have been advanced, and demand for image forming apparatuses capable of high-speed full-color image output has been increasing.

The tandem type image forming apparatus can output a full-color image at a high speed. However, when a plurality of photosensitive members are arranged horizontally to form a wingless type as in the prior art, transfer of transfer paper is performed. Since the path is S-shaped as shown in FIG. 5, the transfer path of the transfer paper becomes long, and the first image output (first print) is delayed when performing image output. Also, if the paper feed tray and the paper discharge tray are attached to the side of the main body, the transfer path of the transfer paper can be shortened, but the installation area becomes large.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which is small in size, can reduce the installation area, can shorten the transfer paper transport path, can output high-speed images, and can stabilize the transfer paper transport performance.

[0016]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of image carriers arranged in a vertical direction and images of different colors are respectively provided on the plurality of image carriers. An image forming means for forming, a transfer belt arranged to face the plurality of image carriers, and a transfer belt for adsorbing and transferring the transfer paper sent from the registration roller; and a transfer paper transferred from the transfer belt. A fixing device for fixing the images of the plurality of images on the transfer paper conveyed by the transfer belt. The length of the transfer paper transport path length of the transfer paper to the first image carrier where the transfer paper first arrives is shorter than half the length of the transfer paper of the minimum size capable of passing the paper in the paper passing direction. Small, installation area Made small can be shortened transfer paper conveying path may transfer sheet conveyance performance stably be high-speed image output.

According to a second aspect of the present invention, there are provided a plurality of image carriers arranged vertically, image forming means for forming images of different colors on the plurality of image carriers, and the plurality of image carriers. And a fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, wherein the fixing device fixes the image on the transfer paper conveyed from the conveyance transfer belt. A color image is formed by superimposing and transferring the images on the plurality of image carriers on transfer paper conveyed by the transfer belt, and forming the color image on the transfer paper conveyed by the transfer belt. In an image forming apparatus that forms a single-color image by transferring an image on one of the image carriers, the transfer belt and the transfer transfer belt are formed depending on whether a single-color image is formed or a color image is formed. Comprising said one moving means for contacting and separating the image bearing member other than the image bearing member of the image bearing member having,
The length of the transfer paper of the minimum size that can pass through the length of the transfer paper transport path from the registration roller to the first image carrier from which the transfer paper first arrives is one of the length in the paper passing direction. / 2, which is small in size, the installation area can be reduced, the transfer paper transport path can be shortened, high-speed image output is possible, and the transfer paper transport performance can be stabilized.

According to a third aspect of the present invention, there are provided a plurality of image carriers arranged in a vertical direction, image forming means for forming images of different colors on the plurality of image carriers, and the plurality of image carriers. A transfer belt for adsorbing and transporting the transfer paper sent from the registration rollers, and a fixing device for fixing an image on the transfer paper transported from the transport transfer belt; and the plurality of images. Suction means provided on the transfer paper transport direction upstream side of the carrier to attract the transfer paper to the transport transfer belt, and the images on the plurality of image carriers are transferred onto the transfer paper transported by the transport transfer belt. In the image forming apparatus for transferring images in a superimposed manner, the length of the transfer paper transport path from the registration roller to the suction means is shorter than の of the minimum length of transfer paper capable of passing the paper in the paper passing direction, And it is possible to reduce the footprint mold can be shortened transfer paper conveying path may transfer sheet conveyance performance stably be high-speed image output.

According to a fourth aspect of the present invention, there are provided a plurality of image carriers arranged vertically, image forming means for forming images of different colors on the plurality of image carriers, and the plurality of image carriers. A transfer belt for adsorbing and transporting the transfer paper sent from the registration rollers, and a fixing device for fixing an image on the transfer paper transported from the transport transfer belt; and the plurality of images. Suction means provided on the transfer paper transport direction upstream side of the carrier to attract the transfer paper to the transport transfer belt, and the images on the plurality of image carriers are transferred onto the transfer paper transported by the transport transfer belt. A color image is formed by superimposing and transferring, and a single-color image is formed by transferring an image on one of the plurality of image carriers onto the transfer paper conveyed by the conveyance transfer belt. The transfer transfer belt and the image carrier other than the one image carrier out of the plurality of image carriers depending on whether a single-color image is formed or a color image is formed. The transfer paper transport path length from the registration roller to the suction means is shorter than half the length of the minimum size transfer paper in the paper passing direction. The installation area can be reduced, the transfer paper transport path can be shortened, high-speed image output is possible, and the transfer paper transport performance can be stabilized.

According to a fifth aspect of the present invention, there are provided a plurality of image carriers arranged vertically, image forming means for forming images of different colors on the plurality of image carriers, and the plurality of image carriers. And a fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, wherein the fixing device fixes the image on the transfer paper conveyed from the conveyance transfer belt. In an image forming apparatus for superimposing and transferring images on the plurality of image carriers on transfer paper conveyed by a conveyance transfer belt, the image forming apparatus transfers the images from the image carrier which finally arrives at the transfer paper among the plurality of image carriers. The length of the transfer paper transport path length to the apparatus is shorter than half the length of the transfer paper of the minimum size that can pass the paper in the paper passing direction,
The transfer paper conveyance path can be shortened due to its small size, the installation area can be made small, high-speed image output is possible, and the transfer paper conveyance performance can be stabilized.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the transfer from the image carrier to which the transfer paper arrives last from the plurality of image carriers to the fixing device is performed. The length of the paper transfer path is shorter than half the length in the paper passing direction of the minimum size transfer paper capable of passing the paper,
The transfer paper conveyance path can be shortened because of its small size and installation area, so that high-speed image output is possible and transfer paper conveyance performance can be made more stable.

[0022]

FIG. 1 schematically shows a first embodiment of the present invention. The first embodiment is an embodiment of the invention according to claim 1, and is an embodiment of a tandem type image forming apparatus. In the first embodiment, a plurality of image forming units 21Bk, 21M, 21Y, and 21C that form images of a plurality of colors, for example, Bk, M, Y, and C, respectively.
Are arranged in the vertical direction, and the image forming unit 21B
k, 21M, 21Y, and 21C are image carriers 22Bk, 22M, 22Y, and 22 made of a drum-shaped photoconductor, respectively.
C, charging device (for example, contact charging device) 23Bk, 23
M, 23Y, 23C, developing devices 24Bk, 24M, 24
Y, 24C, cleaning devices 25Bk, 25M, 25
Y, 25C and the like.

Photoconductors 22Bk, 22M, 22Y, 22C
Are arranged in the vertical direction so as to face the endless transfer belt 26, and are driven to rotate at the same peripheral speed by a rotation drive unit such as a motor. The photoconductors 22Bk, 22M, 22
Y and 22C are charging devices 23Bk and 23M, respectively.
After being uniformly charged by 23Y and 23C, exposure means 27Bk, 27M, 27Y, 2
Each is exposed by 7C to form an electrostatic latent image.

Optical writing devices 27Bk, 27M, 27
Y and 27C drive the semiconductor laser by the semiconductor laser driving circuit in accordance with the image signals of Y, M, C and Bk, and deflect and scan the laser beam from the semiconductor laser by the polygon mirrors 29Bk, 29M, 29Y and 29C. ,
This polygon mirror 29Bk, 29M, 29Y, 29C
Are formed on the photoconductors 22Bk, 22M, 22Y, and 22C via fθ lenses and mirrors (not shown) to form photoconductors 22Bk, 22M, 22Y, and 22C.
22C is exposed to form an electrostatic latent image.

The photosensitive members 22Bk, 22M, 22Y, 2
The electrostatic latent images on 2C are developed by developing devices 24Bk and 24Bk, respectively.
Bk, M, Y, C developed by M, 24Y, 24C
A toner image of each color is obtained. Therefore, the charging device 23B
k, 23M, 23Y, 23C, optical writing device 27B
k, 27M, 27Y, 27C and developing devices 24Bk, 2
4M, 24Y, and 24C are the photoconductors 22Bk, 22M,
The image forming unit forms images (toner images) of Bk, M, Y, and C colors on 2Y and 22C.

On the other hand, transfer paper such as plain paper and OHP sheet is transferred from a paper feeder 30 which is provided at the bottom of this embodiment using a paper feed cassette to a registration roller 31 along a transfer paper transport path. The registration rollers 31 feed the transfer paper in synchronism with the toner image on the photoconductor 22Bk in the first color image forming unit (the image forming unit that first transfers the image on the photoconductor onto the transfer paper) 21Bk. The sheet is sent to a transfer nip between the transfer belt 26 and the photoconductor 22Bk.

In this case, the length of the transfer paper of the minimum size that can pass through the length of the transfer paper transport path from the registration roller 31 to the first color photoconductor (photoconductor to which the transfer paper first arrives) 22Bk can be passed. Even when thin paper or small-size paper is passed as transfer paper,
The leading edge of the transfer paper is reliably fed to the nip between the transfer belt 26 and the first color photoconductor 22Bk.

The transport transfer belt 26 is stretched over a drive roller 32 and a driven roller 33 arranged in a vertical direction, and the drive roller 32 is driven to rotate by a drive unit (not shown) so that the transport transfer belt 26 is moved to the photosensitive members 22Bk, 22M, 22
It rotates at the same peripheral speed as Y and 22C. Registration roller 31
Is transferred by the transfer belt 26, and the toner images of the respective colors Bk, M, Y, and C on the photoconductors 22Bk, 22M, 22Y, and 22C are transferred by transfer means 34Bk, 34M, which are formed by corona dischargers. A full-color image is formed by successively transferring images by the action of an electric field formed by 34Y and 34C, and at the same time, the toner is electrostatically attracted to the transfer belt 26 and is surely conveyed.

The transfer paper is gradually charged by a separation means 36 comprising a separation charger, separated from the transfer belt 26, and then a full-color image is fixed by a fixing device 37. The paper is discharged to a paper discharge unit 39 provided. Also, the photoconductor 22B
After transfer of the toner images, k, 22M, 22Y, and 22C are cleaned by the cleaning devices 25Bk, 25M, 25Y, and 25C to prepare for the next image forming operation. Here, the transfer belt 26 and the transfer units 34Bk, 34
M, 34Y, and 34C transport the transfer paper and
A transfer device for transferring the toner images on k, 22M, 22Y, and 22C in an overlapping manner is configured.

In the first embodiment, high-speed image output is possible, and the photosensitive members 22Bk, 22M, 22Y,
By arranging 2C along the vertical direction, the installation area can be reduced, and the transfer paper transport path can be shortened. However, in the conventional tandem type image forming apparatus in which the photosensitive members are arranged along the horizontal direction, the gravity acting on the transfer paper acts in the direction in which the transfer paper approaches the transfer belt, so that the transfer paper transport performance is stabilized. However, in the tandem type image forming apparatus in which the photoconductors are arranged along the vertical direction as in the first embodiment, such an effect does not occur, and the leading edge of the transfer paper is likely to be unstable, resulting in a problem such as a paper jam. Is easy to occur.

In the first embodiment, the positional relationship between the paper feeding system for feeding the transfer paper and the transport transfer device is optimized, that is, the first color photoconductor (the transfer paper is (The arriving photoreceptor) The transfer paper transport path length up to 22 Bk is shorter than half the length of the minimum size transfer paper in the paper passing direction that allows the paper to pass through, so that thin paper or small-size paper can be used as the transfer paper. Even when paper is transferred, the leading edge of the transfer paper is securely transferred to the transfer belt 26 and the first-color photosensitive member 22B.
The transfer paper can be fed to the nip portion with the transfer roller k, and the transfer paper conveyance performance can be stabilized, and the deterioration of the image quality due to a problem such as a paper jam or the rubbing of an unfixed image can be prevented.

As described above, the first embodiment is an embodiment of the first aspect of the present invention, in which the photosensitive members 22Bk, 22M, 22 as a plurality of image carriers arranged in the vertical direction.
Y, 22C and the plurality of image carriers 22Bk, 22M,
Charging devices 23Bk, 23M, 23Y, 23C, optical writing devices 27Bk, 27M, 27Y, 27C, and a developing device 24B that form images of different colors on the respective 22Y and 22C.
k, 24M, 24Y, and 24C;
The plurality of image carriers 22Bk, 22M, 22Y, 22C
And a fixing device 37 that fixes the image on the transfer paper conveyed from the conveyance transfer belt 26 by adsorbing and conveying the transfer paper sent from the registration roller 31 and that is opposed to the transfer roller 26. An image forming apparatus for transferring the images on the plurality of image carriers 22 </ b> Bk, 22 </ b> M, 22 </ b> Y, and 22 </ b> C on transfer paper conveyed by the conveyance transfer belt 26.
1 to the plurality of image carriers 22Bk, 22M, 22Y,
First image carrier 2 from which transfer paper first arrives among 22C
The transfer paper transport path length up to 2Bk is shorter than half the length of the minimum size transfer paper that can pass the paper in the paper passing direction. Image output is possible and transfer paper transfer performance can be stabilized.

FIG. 2 schematically shows a second embodiment of the present invention. The second embodiment is an embodiment of the second aspect of the present invention, and performs a full-color image forming operation similarly to the first embodiment, but differs from the first embodiment in the following points. In the second embodiment, not only a full-color image forming operation but also a black-and-white image forming operation is performed, and a contact / separation unit (not shown) determines whether a full-color image output mode or a black-and-white image output mode is selected by a user using an operation unit. The transfer belt 26 is moved to the Bk image forming unit 21Bk
Image forming units 21M and 21 other than the photosensitive member 22Bk
The Y and 21C photoconductors 22M, 22Y and 22C are brought into contact with and separated from each other.

When the full-color image output mode is selected and the full-color image forming operation is performed, the contact / separation means presses the transport transfer belt 26 against all the photosensitive members 22Bk, 22M, 22Y, and 22C, and presses the black-and-white image. When a black and white image is output in which the output mode is selected and a black and white image forming operation is performed, the transfer belt 26 is rotated by a predetermined angle about the drive roller 32 so as to be separated from the photoconductors 22M, 22Y, and 22C so as to be separated. 2
Press only to 2Bk.

At the time of outputting a monochrome image, the Bk image forming unit 21Bk operates similarly to the photosensitive member 22 at the time of outputting a full-color image.
A Bk image is formed on Bk. The registration roller 31 transfers the transfer paper fed from the paper supply device 30 to the Bk toner image on the photoconductor 22Bk in synchronization with the transfer transfer belt 2.
6 and the photoconductor 22Bk to the transfer nip. In this case, the transfer paper transport path length from the registration roller 31 to the photoreceptor 22Bk is configured to be shorter than half the length in the paper passing direction of the minimum size transfer paper capable of passing the paper. Even when small paper is passed, the leading edge of the transfer paper is reliably transferred to the transfer belt 26 and the photosensitive member 2 of the first color.
It is sent to the nip with 2Bk.

The transfer paper is conveyed by the transfer belt 26, and the Bk toner images on the photoreceptor 22Bk are sequentially superimposed and transferred by the action of the electric field formed by the transfer means 34Bk, so that a Bk single-color image is formed. At the same time as the sheet is formed, the sheet is electrostatically attracted to the transfer belt 26 and transported reliably. Therefore, the conveyance transfer belt 26 is
Even when the transfer paper is separated from the transfer belts M, 22Y, and 22C, the transfer paper is reliably conveyed by the attraction force with the transfer belt 26.
The transfer paper is gradually charged by a separation unit 36 and separated from the transfer belt 26, and then a full-color image is fixed by a fixing device 37.
It is discharged to 9.

The second embodiment is an embodiment of the second aspect of the present invention, in which photosensitive members 22Bk, 22M, 22Y, 22 as a plurality of image carriers arranged in a vertical direction.
C and the plurality of image carriers 22Bk, 22M, 22Y,
Charging device 23B for forming images of different colors on 22C
k, 23M, 23Y, 23C, optical writing device 27B
k, 27M, 27Y, 27C and developing devices 24Bk, 2
An image forming unit including 4M, 24Y, and 24C, and a transfer belt that is disposed to face the plurality of image carriers 22Bk, 22M, 22Y, and 22C and that sucks and transfers transfer paper sent from registration rollers 31 26, and a fixing device 37 for fixing an image on transfer paper conveyed from the transfer belt 26.
6. The plurality of image carriers 22 on the transfer paper conveyed by
Bk, 22M, 22Y, and 22C, a color image is formed by superimposing and transferring the images, and the plurality of image carriers 2 are transferred onto a transfer sheet conveyed by the transfer belt 26.
In an image forming apparatus that forms a single-color image by transferring an image on one of the image carriers 22Bk of 2Bk, 22M, 22Y, and 22C, the image forming apparatus may be configured to form a single-color image or a color image. Conveyance transfer belt 26
And the plurality of image carriers 22Bk, 22M, 22Y, 22
C, a contact / separation unit for bringing the image carriers 22M, 22Y, and 22C other than the one image carrier 22Bk into and out of contact with each other.
The length of the transfer paper of the minimum size that can pass through the transfer paper transport path length to the first image carrier 22Bk where the transfer paper first arrives among the 2Bk, 22M, 22Y, and 22C is 1 of the length in the paper passing direction.
Since the length is shorter than / 2, the size is small, the installation area can be reduced, the transfer paper transport path can be shortened, high-speed image output is possible, and the transfer paper transport performance can be stabilized.

FIG. 3 schematically shows a third embodiment of the present invention. The third embodiment is an embodiment of the invention according to claim 3, and differs from the first embodiment in the following points. In the third embodiment, the suction means 40 for electrostatically attracting the transfer paper to the transfer belt 26 is provided by the photosensitive member 22B.
k, 22M, 22Y, and 22C are provided on the upstream side in the transfer paper transport direction. The suction unit 40 is configured using, for example, a suction roller that sandwiches the transfer belt 26, and a bias is applied from a power supply to the suction roller to form an electric field.

The registration rollers 31 transfer the transfer paper fed from the paper feeding device 30 to the transfer belt 26 and the suction means 40 in synchronization with the Bk toner image on the photoreceptor 22Bk.
To the nip. In this case, the registration roller 3
With a configuration in which the length of the transfer paper transport path length from 1 to the suction means 40 is shorter than の of the minimum length of the transfer paper that can pass through the paper in the paper passing direction, thin paper or small-size paper is used as the transfer paper. Even in this case, the leading end of the transfer paper is reliably fed into the nip between the transfer belt 26 and the suction means 40.
The transfer paper is electrostatically attracted to the transfer belt 26 by the action of the electric field formed by the suction means 40, and is reliably transported by the transfer belt 26.

The third embodiment is an embodiment of the third aspect of the present invention, in which photosensitive members 22Bk, 22M, 22Y, 22 as a plurality of image carriers arranged in a vertical direction.
C and the plurality of image carriers 22Bk, 22M, 22Y,
Charging device 23B for forming images of different colors on 22C
k, 23M, 23Y, 23C, optical writing device 27B
k, 27M, 27Y, 27C and developing devices 24Bk, 2
An image forming unit including 4M, 24Y, and 24C, and a transfer belt that is disposed to face the plurality of image carriers 22Bk, 22M, 22Y, and 22C and that sucks and transfers transfer paper sent from registration rollers 31 26, a fixing device 37 for fixing an image on transfer paper conveyed from the conveyance transfer belt 26, and the plurality of image carriers 22B.
k, 22M, 22Y, and 22C, provided at an upstream side in the transfer paper transport direction with respect to the transfer paper transport belt 26. The suction unit 40 attracts the transfer paper to the transport transfer belt 26. Image carrier 22Bk,
In the image forming apparatus for transferring the images on 22M, 22Y, and 22C in a superimposed manner, the length in the paper passing direction of the minimum size transfer paper capable of passing the length of the transfer paper transport path from the registration roller 31 to the suction unit 40 Since it is shorter than 紙, the transfer paper transport path can be shortened with a small size, the installation area can be shortened, high-speed image output is possible, and the transfer paper transport performance can be stabilized.

FIG. 4 schematically shows a fourth embodiment of the present invention. The fourth embodiment is an embodiment of the invention according to claim 4, and differs from the third embodiment in the following points. In the fourth embodiment, the image forming unit 21B
k, 21M, 21Y, and 21C are image forming units 21Y, 21M, 21C, and 21Bk along the transfer paper transport direction.
Are arranged in this order.

In the fourth embodiment, similarly to the second embodiment, not only a full-color image forming operation but also a black-and-white image forming operation is performed. The transfer belt 26 is set to B depending on whether the black and white image output mode is selected.
Photoconductor 22 of image forming units 21M, 21Y, 21C other than photoconductor 22Bk of k image forming unit 21Bk
M, 22Y and 22C.

When the full-color image output mode is selected and the full-color image forming operation is performed, the contact / separation means presses the transport transfer belt 26 against all of the photosensitive members 22Bk, 22M, 22Y, and 22C so that the black-and-white image is formed. At the time of outputting a monochrome image in which the output mode is selected and a monochrome image forming operation is performed, the transfer belt 26 is rotated by a predetermined angle around the driven roller 33 so as to be separated from the photosensitive members 22M, 22Y, and 22C so as to be separated. 2
Press only to 2Bk.

At the time of outputting a monochrome image, the Bk image forming unit 21Bk operates similarly to the case of outputting a full-color image.
A Bk image is formed on Bk. The registration roller 31 transfers the transfer paper fed from the paper supply device 30 to the Bk toner image on the photoconductor 22Bk in synchronization with the transfer transfer belt 2.
Send to 6. In this case, the registration roller 31 transfers the transfer paper fed from the paper feeding device 30 to the Bk on the photoconductor 22Bk.
The toner image is sent to the nip portion between the transfer belt 26 and the suction means 40 in synchronization with the timing of the toner image. In this case, the transfer paper transport path length from the registration roller 31 to the suction means 40 is one of the minimum transfer paper length in the paper passing direction that can pass the paper.
With a configuration shorter than / 2, even when thin paper or small-sized paper is passed as the transfer paper, the leading end of the transfer paper is reliably sent to the nip portion between the transfer belt 26 and the suction means 40. The transfer paper is electrostatically attracted to the transfer belt 26 by the action of the electric field formed by the suction means 40, and is reliably transported by the transfer belt 26.

The transfer paper is conveyed by the transfer belt 26, and the Bk toner images on the photoreceptor 22Bk are sequentially superimposed and transferred by the action of the electric field formed by the transfer means 34Bk, whereby a Bk single-color image is formed. It is formed. Therefore, the transfer belt 26 is moved to the photosensitive members 22M, 22Y, 22Y.
C, the transfer paper is transported by the transfer belt 26.
Is reliably transported by the attraction force. The transfer paper is gradually discharged by the separation means 36 and separated from the transfer belt 26, after which a full-color image is fixed by the fixing device 37, and is discharged to the discharge part 39 by the discharge roller 38.

The fourth embodiment is an embodiment of the fourth aspect of the present invention, and includes a plurality of photosensitive members 22Bk, 22M, 22Y, and 22 as a plurality of image carriers arranged in a vertical direction.
C and the plurality of image carriers 22Bk, 22M, 22Y,
Charging device 23B for forming images of different colors on 22C
k, 23M, 23Y, 23C, optical writing device 27B
k, 27M, 27Y, 27C and developing devices 24Bk, 2
An image forming unit including 4M, 24Y, and 24C, and a transfer belt that is disposed to face the plurality of image carriers 22Bk, 22M, 22Y, and 22C and that sucks and transfers transfer paper sent from registration rollers 31 26, a fixing device 37 for fixing an image on transfer paper conveyed from the conveyance transfer belt 26, and the plurality of image carriers 22B.
k, 22M, 22Y, and 22C, provided at an upstream side in the transfer paper transport direction with respect to the transfer paper transport belt 26. The suction unit 40 attracts the transfer paper to the transport transfer belt 26. Image carrier 22Bk,
A color image is formed by superimposing and transferring the images on 22M, 22Y, and 22C, and the plurality of image carriers 22B are formed on transfer paper conveyed by the conveyer transfer belt 26.
k, image carrier 2 of one of 22M, 22Y, and 22C
In an image forming apparatus that forms a single-color image by transferring an image on 2Bk, the transport transfer belt 26 and the plurality of image carriers 22Bk, 22M, depending on whether a single-color image is formed or a color image is formed. Image carrier 22 other than the one image carrier 22Bk of 22Y and 22C
M, 22Y, and 22C are provided. The transfer paper transport path length from the registration roller 31 to the suction unit 40 is the minimum size of transfer paper of the minimum size that can be passed. Since the length is shorter than / 2, the size is small, the installation area can be reduced, the transfer paper transport path can be shortened, high-speed image output is possible, and the transfer paper transport performance can be stabilized.

The fifth embodiment of the present invention is an embodiment of the fifth aspect of the present invention.
The positional relationship between the conveyance transfer device and the fixing device is optimized, that is, the transfer paper conveyance path length from the photoconductor 22C, to which the transfer paper arrives last among the photoconductors 22Bk, 22M, 22Y, and 22C, to the fixing device 37 passes. In this configuration, the length of the transfer paper of the minimum size that can be used is shorter than half the length in the paper passing direction. With this configuration, the transfer sheet can be reliably sent from the transfer belt 26 to the fixing device 37, and the unfixed image on the transfer sheet separated from the transfer belt 26 is transferred to the fixing device 3.
It is possible to prevent the image quality from deteriorating due to contact with the case 7 or the like.

As described above, the fifth embodiment is one embodiment of the invention according to claim 5, and includes a plurality of photosensitive members 22Bk, 22M, as image carriers arranged in a vertical direction.
22Y, 22C and the plurality of image carriers 22Bk, 22
Charging devices 23Bk, 23M, 23Y, 23C, optical writing devices 27Bk, 27M, 27Y, 27C, and a developing device 2 for forming images of different colors on M, 22Y, and 22C, respectively.
4Bk, 24M, 24Y, and 24C, and the plurality of image carriers 22Bk, 22M, 22Y, and 2B.
2C, a transfer belt 26 that adsorbs and transfers the transfer paper sent from the registration roller 31
And a fixing device 37 for fixing an image on the transfer sheet conveyed from the transfer belt 26. The plurality of image carriers 22Bk, 22M, 22Y are formed on the transfer sheet conveyed by the transfer belt 26. , 22C, the transfer paper from the image carrier 22C, from which the transfer paper arrives last, to the fixing device 37 among the plurality of image carriers 22Bk, 22M, 22Y, and 22C. Since the length of the transfer path is shorter than half the length of the transfer paper of the minimum size that can pass the paper in the paper passing direction, the transfer paper path can be shortened with a small size, the installation area can be shortened, and high-speed image output is possible. Transfer paper transfer performance can be stabilized.

The sixth embodiment of the present invention is an embodiment of the sixth aspect of the present invention.
The positional relationship between the transfer device and the fixing device is optimized, that is, the fixing device 37 starts from the photosensitive member 22Bk, from which the transfer paper arrives last among the photosensitive members 22Bk, 22M, 22Y, and 22C.
The length of the transfer paper transfer path up to the transfer paper is shorter than １ ／ of the minimum length of transfer paper that can be passed in the paper passing direction. With this configuration, the photoconductors 22Bk, 22M, 22
Y, 22C, predetermined photoconductors 22M, 22Y, 22C
In an image forming apparatus in which the transfer belt 26 is brought into contact with or separated from the transfer transfer belt 26 in accordance with the image output mode,
The transfer paper separated from the paper can be reliably sent to the fixing device 37.

As described above, the sixth embodiment is an embodiment of the invention according to claim 6, and in the image forming apparatus according to claim 1, 3 or 4, the plurality of image carriers 22Bk, Of the transfer papers 22M, 22Y, and 22C, the transfer paper transport path length from the image carrier 22Bk where the transfer paper arrives last to the fixing device 37 is の of the minimum length of the transfer paper in the paper passing direction. The transfer paper transfer path can be shortened because it is smaller and the installation area can be reduced, the transfer paper transfer path can be shortened, the transfer paper transfer performance can be more stable, and the transfer paper transfer performance can be stabilized. It is possible to prevent the image quality from deteriorating due to the image coming into contact with the case of the fixing device 37 or the like.

Another embodiment of the present invention is another embodiment of the present invention according to claim 6, and includes the first embodiment and the third embodiment.
In the embodiment, the photoconductors 22Bk, 22B
Of the M, 22Y, and 22C, the length of the transfer paper transport path from the photosensitive member 22C to which the transfer paper arrives last to the fixing device 37 is shorter than half the length in the paper passing direction of the minimum size transfer paper that can be passed. With this configuration, the transfer paper separated from the transfer belt 26 can be reliably sent to the fixing device 37.

[0052]

As described above, according to the first aspect of the present invention, a plurality of image carriers arranged vertically and image forming means for forming images of different colors on the plurality of image carriers, respectively. A transfer belt, which is arranged opposite to the plurality of image carriers and sucks and transfers the transfer paper sent from the registration roller, and fixes an image on the transfer paper transferred from the transfer belt. An image forming apparatus having a fixing device and transferring the images on the plurality of image carriers on the transfer paper conveyed by the conveyance transfer belt in a superimposed manner. Since the length of the transfer paper transport path length to the first image carrier where paper first arrives is shorter than half the length in the paper passing direction of the minimum size transfer paper capable of passing the paper, the size is small and the installation area is small. Transfer paper transfer The can be shortened, thereby the transfer sheet conveyance performance stably be high-speed image output.

According to the second aspect of the present invention, a plurality of image carriers arranged in the vertical direction, image forming means for forming images of different colors on the plurality of image carriers, and the plurality of image carriers are provided. A transfer belt that is arranged opposite to the carrier and that sucks and transfers the transfer paper sent from the registration roller;
A fixing device for fixing an image on the transfer paper conveyed from the transfer belt, and transferring the images on the plurality of image carriers on the transfer paper conveyed by the transfer belt in a superimposed manner. An image forming apparatus that forms a color image and transfers a single-color image by transferring an image on one of the plurality of image carriers onto a transfer sheet conveyed by the conveyance transfer belt. The transport transfer belt and the one of the plurality of image carriers according to whether an image is formed or a color image is formed.
Transfer means for contacting and separating an image carrier other than the two image carriers, and transferring the transfer paper from the registration roller to the first image carrier of which transfer paper first arrives among the plurality of image carriers. Since the path length is shorter than half the length of the minimum size of transfer paper that can pass the paper in the paper passing direction, it is compact, the installation area can be reduced, the transfer paper transport path can be shortened, and high-speed image output is possible. Paper transport performance can be stabilized.

According to the third aspect of the present invention, a plurality of image carriers arranged in the vertical direction, image forming means for forming images of different colors on the plurality of image carriers, and the plurality of image carriers are provided. A transfer belt that is arranged opposite to the carrier and that sucks and transfers the transfer paper sent from the registration roller;
A fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, and suction means provided upstream of the plurality of image carriers in the transfer paper conveyance direction to adsorb the transfer paper to the conveyance transfer belt. An image forming apparatus for transferring images on the plurality of image carriers superimposed on transfer paper conveyed by the conveyance transfer belt, wherein the transfer paper conveyance path length from the registration roller to the suction means is passed Since the length of transfer paper of the smallest possible size is shorter than half the length in the paper passing direction, it is compact and the installation area can be reduced, the transfer paper transport path can be shortened, high-speed image output is possible, and the transfer paper transport performance is stable. Can be.

According to the fourth aspect of the present invention, a plurality of image carriers arranged in the vertical direction, image forming means for forming images of different colors on the plurality of image carriers, and the plurality of image carriers are provided. A transfer belt that is arranged opposite to the carrier and that sucks and transfers the transfer paper sent from the registration roller;
A fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, and suction means provided upstream of the plurality of image carriers in the transfer paper conveyance direction to adsorb the transfer paper to the conveyance transfer belt. Forming a color image by superimposing and transferring the images on the plurality of image carriers on transfer paper conveyed by the conveyance transfer belt, and forming the color images on the transfer paper conveyed by the conveyance transfer belt. In an image forming apparatus for forming a monochromatic image by transferring an image on one of the image carriers,
And a contact / separation unit configured to contact / separate the transport transfer belt and an image carrier other than the one image carrier among the plurality of image carriers according to whether a single color image is formed or a color image is formed. Since the length of the transfer paper transport path length from the registration roller to the suction means is shorter than half the length of the transfer paper of the minimum size in which the transfer paper can pass, the transfer paper can be small and the installation area can be reduced. The transfer path can be shortened, high-speed image output is possible, and transfer paper transfer performance can be stabilized.

According to the fifth aspect of the present invention, a plurality of image carriers arranged in the vertical direction, image forming means for forming images of different colors on the plurality of image carriers, and the plurality of image carriers are provided. A transfer belt that is arranged opposite to the carrier and that sucks and transfers the transfer paper sent from the registration roller;
A fixing device for fixing an image on transfer paper conveyed from the transfer belt, and forming an image on the plurality of image carriers by transferring the images on the plurality of image carriers on the transfer paper conveyed by the transfer belt In the apparatus, the length of the transfer paper of the minimum size that can pass the transfer paper transport path length from the image carrier to which the transfer paper arrives last from the plurality of image carriers to the fixing device in the paper passing direction is 1 / 2 shorter than
The transfer paper conveyance path can be shortened due to its small size, the installation area can be made small, high-speed image output is possible, and the transfer paper conveyance performance can be stabilized.

According to the invention of claim 6, according to claim 1,
5. The image forming apparatus according to claim 3, wherein a transfer paper of a minimum size that allows a transfer paper transport path length from the image carrier to which the transfer paper arrives last among the plurality of image carriers to the fixing device to pass. Because it was shorter than half the length in the paper passing direction,
The transfer paper conveyance path can be shortened because of its small size and installation area, so that high-speed image output is possible and transfer paper conveyance performance can be made more stable.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a first embodiment of the present invention.

FIG. 2 is a sectional view schematically showing a second embodiment of the present invention.

FIG. 3 is a sectional view schematically showing a third embodiment of the present invention.

FIG. 4 is a sectional view schematically showing a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating an example of a tandem-type image forming apparatus.

[Explanation of symbols]

22Bk, 22M, 22Y, 22C Photoconductor 23Bk, 23M, 23Y, 23C Charging device 24Bk, 24M, 24Y, 24C Developing device 26 Transport transfer belt 27Bk, 27M, 27Y, 27C Optical writing device 37 Fixing device 40 Suction means

Claims (6)

[Claims] A plurality of image carriers arranged in a vertical direction;
An image forming means for forming images of different colors on the plurality of image carriers, and a transport transfer belt arranged to face the plurality of image carriers and adsorb and transport a transfer sheet sent from a registration roller And a fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, and superimposingly transferring the images on the plurality of image carriers onto the transfer paper conveyed by the conveyance transfer belt. In the image forming apparatus, the transfer of a transfer sheet of a minimum size capable of passing a transfer sheet conveyance path length from the registration roller to a first image carrier from which the transfer sheet first arrives among the plurality of image carriers. An image forming apparatus characterized in that the length is shorter than half the length in the direction. A plurality of image carriers arranged in a vertical direction;
An image forming means for forming images of different colors on the plurality of image carriers, and a transport transfer belt arranged to face the plurality of image carriers and adsorb and transport a transfer sheet sent from a registration roller And a fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, and superimposingly transferring the images on the plurality of image carriers onto the transfer paper conveyed by the conveyance transfer belt. An image forming apparatus that forms a color image by transferring an image on one of the plurality of image carriers onto a transfer sheet conveyed by the conveyance transfer belt, thereby forming a single-color image. Contacting / separating the transport transfer belt and an image carrier other than the one image carrier among the plurality of image carriers depending on whether a single-color image or a color image is formed; A sheet-passing direction of a transfer sheet of a minimum size that has a step and can pass a transfer sheet transport path length from the registration roller to a first image carrier from which the transfer sheet first arrives among the plurality of image carriers; An image forming apparatus characterized in that the length is shorter than half the length. 3. A plurality of image carriers arranged in a vertical direction;
An image forming means for forming images of different colors on the plurality of image carriers, and a transport transfer belt arranged to face the plurality of image carriers and adsorb and transport a transfer sheet sent from a registration roller A fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, and a suction unit provided on the upstream side of the plurality of image carriers in the transfer paper conveyance direction to adsorb the transfer paper to the conveyance transfer belt. And an image forming apparatus for superimposing and transferring images on the plurality of image carriers on transfer paper conveyed by the conveyance transfer belt, wherein a transfer paper conveyance path length from the registration roller to the suction unit is set to An image forming apparatus, wherein the length of the transfer paper of the minimum size that can be passed is made shorter than 1/2 of the length in the paper passing direction. 4. A plurality of image carriers arranged in a vertical direction;
An image forming means for forming images of different colors on the plurality of image carriers, and a transport transfer belt arranged to face the plurality of image carriers and adsorb and transport a transfer sheet sent from a registration roller A fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, and a suction unit provided on the upstream side of the plurality of image carriers in the transfer paper conveyance direction to adsorb the transfer paper to the conveyance transfer belt. A color image is formed by superimposing and transferring the images on the plurality of image carriers on transfer paper conveyed by the transfer belt, and forming the color image on the transfer paper conveyed by the transfer belt. In an image forming apparatus that forms a single-color image by transferring an image on one of the plurality of image carriers, a single-color image or a color image is formed. A transfer unit for moving the transfer belt and an image carrier other than the one image carrier out of the plurality of image carriers to and away from the registration roller; An image forming apparatus wherein the path length is shorter than half the length in the sheet passing direction of the minimum size transfer sheet capable of passing the sheet. 5. A plurality of image carriers arranged in a vertical direction,
An image forming means for forming images of different colors on the plurality of image carriers, and a transport transfer belt arranged to face the plurality of image carriers and adsorb and transport a transfer sheet sent from a registration roller And a fixing device for fixing an image on the transfer paper conveyed from the conveyance transfer belt, and superimposingly transferring the images on the plurality of image carriers onto the transfer paper conveyed by the conveyance transfer belt. In the image forming apparatus, a length of a transfer sheet of a minimum size capable of passing a transfer paper transport path length from the image carrier to which the transfer paper arrives last among the plurality of image carriers to the fixing device in a paper passing direction. An image forming apparatus characterized in that the image forming apparatus is shorter than 1/2 of the image forming apparatus. 6. The image forming apparatus according to claim 1, wherein the transfer paper of the plurality of image carriers has a transfer paper transport path length from the image carrier that arrives last to the fixing device. 1 of the minimum length of transfer paper that can be used in the paper passing direction
An image forming apparatus characterized in that the length is shorter than / 2.