JPH06102776A - Image forming device - Google Patents

Abstract

PURPOSE:To attain an image forming device for a full color copying machine, etc., capable of easily avoiding and resolving various kinds of problems caused by the effect that a transfer material comes in contact with photosensitive drums except the photosensitive drum which is used for a required color. CONSTITUTION:An elliptical cam 24 is mounted on the rotary shaft of the photosensitive drum 2Y (2M, 2C and 2BK), and a guide roller 30 is mounted on the rotary shaft of a transfer roller 28 for a transfer device 5Y (5M, 5C and 5BK) positioned on the rear side of a transfer material carrying belt 12, and the guide roller 30 is always press-contacted with the elliptical cam 24 by a spring 31. At a full color printing case, the elliptical cam 24 of the photosensitive drum 2Y (2M, 2C and 2BK) is controlled so that the minor axis position of the cam 24 may abut on the guide roller 30 of each transfer roller 28. At a monochronomatic printing case, the elliptical cam 24 of the selected photosensitive drum is controlled so as to abut on the guide roller 30 of the transfer roller 28 to which the minor axis position of the came 24 corresponds, and the elliptical cam 24 of the photosensitive drum other than the aforesaid drum is controlled so as to abut on the guide roller 30 of the transfer roller 28 to which the major axis position of the cam 24 corresponds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic color image forming apparatus such as a so-called full-color copying machine or a color laser printer, and more particularly to a color image formed on a sheet by using a plurality of photosensitive drums. The present invention relates to an image forming apparatus to be formed.

[0002]

2. Description of the Related Art In recent years, in response to the color orientation of offices,
Digital full-color copiers have been developed. One of the systems of this type of full-color copying machine is a so-called four-conductor drum tandem system using four photoconductor drums (image bearing members). In this 4-tandem tandem system, four photoconductor drums are arranged in parallel, and a toner image is formed on each photoconductor drum by using yellow, magenta, cyan, and black toners to form one transfer material. In this method, the toner images are sequentially transferred so that the colors are overlapped to obtain a full-color image.

In the four-tandem tandem system, the transfer material placed on the conveyor belt contacts the four photosensitive drums one after another to transfer the toner image. In addition, except when forming a full-color image, for example, when only a black image is formed, a toner image is not formed on the three photoconductor drums of yellow, magenta, and cyan, and a black photoconductor drum is formed. Only, the toner image is formed with the black toner. Therefore, only the toner image with the black toner is transferred to the transfer material, and a black only image is obtained.

[0004]

However, as described above, even when only a single-color image is required, the transfer material sequentially contacts the other three photoconductor drums, so that the photoconductor drums are contacted with each other. There is a problem that residual toner of unnecessary color adheres to the transfer material to deteriorate the quality of the image, and unnecessary contact shortens the life of the photosensitive drum.

On the other hand, the transfer material passes through the respective transfer positions while being placed on the conveyor belt. For example, when the conveyor belt meanders, the conveyed transfer material also meanders along the conveyor belt, and each transfer material is transferred. There is also a problem in that the position in the main scanning direction shifts, causing color shift.

Therefore, according to the present invention, various problems caused by contact of the transfer material with an image carrier other than the above-mentioned required image carrier can be easily avoided and solved. An object is to provide a forming device.
Another object of the present invention is to provide an image forming apparatus capable of solving the color misregistration of the image on the transfer material due to the meandering of the conveyor belt as described above.

[0007]

An image forming apparatus according to a first aspect of the present invention is provided corresponding to a plurality of image carriers that are sequentially arranged, and a plurality of images are formed on each image carrier. Image forming means, conveying means for sequentially conveying the transfer material to each of the image carriers to transfer the image formed on the image carrier by the image forming means to the transfer material, and the conveying means. And a transfer material contacting / separating unit for selectively contacting / separating the transfer material conveyed by the above-mentioned with respect to each of the image carriers.

The image forming apparatus according to the second invention is provided corresponding to each of a plurality of image carriers that are sequentially arranged,
A plurality of image forming means for respectively forming an image on each image carrier, a belt-shaped transport means for sequentially transporting the transfer material to each image carrier, and a transfer material transported by the transport means are described above. Transfer material contacting / separating means for selectively contacting / separating with respect to each image carrier, and running guide means for guiding the traveling of the belt-shaped conveying means when the transfer material contacting / separating means makes contact with / separating the transfer material. It is equipped with.

An image forming apparatus according to a third aspect of the invention is provided corresponding to each of a plurality of image carriers that are sequentially arranged,
A plurality of image forming means for forming an image by performing main scanning and sub-scanning on each image carrier, a conveying means for sequentially conveying a transfer material to each image carrier, and each image carrier On the upstream side of, a conveyance state detection unit that detects the conveyance state of the transfer material that is conveyed by the conveyance unit,
Scanning direction position control means for controlling the main scanning direction position and the sub scanning direction position of the image formed on the image carrier by each of the image forming means based on the detection result of the transport state detecting means. ing.

An image forming apparatus according to a fourth aspect of the present invention is provided with a plurality of image carriers which are sequentially arranged and corresponding to the respective image carriers, and the main scanning and the sub scanning are performed on the respective image carriers. A plurality of image forming means for respectively forming images by performing scanning, a conveying means for sequentially conveying the transfer material to the respective image carriers, and a conveying means for conveying the transfer material on the upstream side of the respective image carriers. Of the transfer state of the transfer material detected by the transfer state detection means, and an image formed on the image carrier of each of the image forming means based on the shift of the transfer state of the transfer material detected by the transfer state detection means. The difference between the scanning direction position correcting means for correcting the main scanning direction position and the sub-scanning direction position and the deviation of the transfer state of the transfer material detected by the transfer state detecting means is the maximum correction amount for image formation on the image carrier. Is over If, and a control means for controlling so as to discharge the transfer material.

[0011]

According to the first aspect of the invention, the transfer material contacting / separating means for selectively contacting / separating the conveyed transfer material to / from the image carrier is provided, so that the transfer material is brought into contact with only the required image carrier. Let me
It is not necessary to bring the transfer material into contact with an unnecessary image carrier.

According to the second invention, the same operation as that of the first invention is obtained, and further, when the transfer material is brought into contact with or separated from the transfer material by the transfer material contacting / separating means, the transfer material is conveyed in a belt shape. By having the travel guide means for guiding the travel of the means, there is no deformation stress applied to the transfer means or the like by the transport means.

According to the third aspect of the present invention, the transfer state of the transfer material is detected, and the positions of the image formed on the image carrier in the main scanning direction and the sub scanning direction are controlled, so that the meandering of the transfer means, etc. Color shift due to can be avoided.

According to the fourth aspect of the invention, the same effect as that of the third aspect of the invention can be obtained, and further, when the positions of the image formed on the image carrier in the main scanning direction and the sub scanning direction cannot be corrected. By ejecting the transfer material as it is, there is no waste of jam processing.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. First, the first embodiment will be described.

FIG. 1 schematically shows the structure of, for example, a 4-drum tandem type full-color copying machine according to the first embodiment. This full-color copying machine has four sets of recording units (a solid-state scanning head unit, an equal-magnification image-forming optical system, etc.) and four sets of image forming units (photoconductors) that combine an electrophotographic system capable of forming an image on a transfer material. Drum, charging device, developing device, transfer device, cleaning device, static eliminator, etc., which are sequentially arranged in a row.

That is, first, the yellow recording unit / image forming unit will be described. According to the yellow image data sent from the print control unit (not shown), the solid-state scanning head 1Y serves as a photoconductor drum as an image carrier of the yellow. The exposure light is output to 2Y. The solid-state scanning head 1Y has a structure in which minute light emitting portions are arranged at equal intervals on a line in the main scanning direction, and responds to an on-off signal sent from a print control portion according to a pattern to be printed. Then, by controlling the lighting of the individual light emitting portions of the line in the main scanning direction, the light is imaged on the photoconductor drum 2Y by an equal-magnification imaging optical system that images the light of the light emitting portions in a one-to-one manner. Perform exposure. Specifically, an LED head array with a resolution of 444 DPI was used for the solid-state scanning head 1Y, and a SELFOC lens array was used for the unity-magnification imaging optical system.

Around the photosensitive drum 2Y, a charging device 3Y for charging the surface of the photosensitive drum 2Y, a developing device 4Y,
A transfer device 5Y, a cleaning device 6Y, and a charge eliminating device 7Y are provided.

The photosensitive drum 2Y is rotationally driven at a peripheral speed of V0 by a drive motor (not shown). The surface of the photoconductor drum 2Y is charged by a charging device 3Y including a conductive charging roller provided in contact with the surface of the photoconductor drum 2Y. The charging roller is rotated by coming into contact with the surface of the photosensitive drum 2Y.

The surface of the photosensitive drum 2Y is formed of an organic photoconductor. This photoconductor usually has a high resistance, but has a property that the specific resistance of the light irradiation portion changes when light is irradiated. Therefore, by irradiating the surface of the charged yellow photoconductor drum 2Y with light corresponding to the yellow print pattern from the solid-state scanning head 1Y through an equal-magnification imaging optical system, an electrostatic latent image of the yellow print pattern is formed on the photoconductor. It is formed on the surface of the drum 2Y.

The electrostatic latent image is an image formed on the surface of the photosensitive drum 2Y by charging, and the solid scanning head 1Y.
By the light irradiation from, the specific resistance of the surface to be irradiated of the photoconductor decreases, and the charged charges on the surface of the photosensitive drum 2Y flow,
On the other hand, it is a so-called negative latent image which is formed by remaining electric charge in the portion not irradiated with light from the solid-state scanning head 1Y.

The photoconductor drum 2 thus charged.
The light from the solid-state scanning head 1Y is imaged at the exposure position on Y, and the photosensitive drum 2Y on which the latent image is formed is rotated at the speed V0 to the developing position. Then, at this developing position, the latent image on the photosensitive drum 2Y is converted into a visible toner image by the developing device 4Y.

In the developing device 4Y, a yellow toner made of resin containing a yellow dye is prepared.
The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y and has a charge of the same polarity as the electrostatic charge charged on the photosensitive drum 2Y. As the surface of the photoconductor drum 2Y passes through the developing device 4Y, the yellow toner electrostatically adheres only to the latent image portion where the charge is removed, and the latent image is developed by the yellow toner (reversal). developing).

The photoconductor drum 2Y on which the yellow toner image has been formed continues to rotate at the outer periphery V0, and at the position of the transfer position, the transfer device 5Y on the conveyor belt 12 is timely supplied by the paper feeding system. The toner image is transferred onto the transfer material (paper) 8.

The paper feeding system comprises a pickup roller 9, a feed roller 10, and a registration roller 11.
The transfer material 8 lifted from the paper feed cassette 39 by the pickup roller 9 is conveyed by the feed roller 10 to the registration roller 11 one by one. The registration rollers 11 feed the transfer material 8 onto the transfer material conveyance belt 12 after the transfer material 8 is repositioned. The peripheral speed of the registration roller 11 and the peripheral speed of the transfer material conveying belt 12 are the same as those of the photosensitive drum 2Y
The peripheral speed V0 is set to be constant. The transfer material 8 is sent to the transfer position of the photosensitive drum 2Y together with the transfer material conveying belt 12 at a speed V0 equal to that of the photosensitive drum 2Y while the transfer material 8 is partially held by the registration roller 11.

At the transfer position, the yellow toner image on the photoconductor drum 2Y which is in contact with the transfer material 8 is separated from the photoconductor drum 2Y and transferred onto the transfer material 8 by the transfer device 5Y, resulting in the yellow print. A yellow toner image having a print pattern based on the signal is formed on the transfer material 8.

The transfer device 5Y is composed of a transfer roller having semiconductivity. The transfer roller supplies an electric field having a polarity opposite to the potential of the yellow toner electrostatically attached to the photosensitive drum 2Y from the back side of the transfer material transport belt 12. This electric field is generated by the transfer material conveying belt 1.
2, and acts on the yellow toner image on the photoconductor drum 2Y through the transfer material 8, and as a result, the photoconductor drum 2Y
The toner image is transferred to the transfer material 8.

The transfer material 8 thus transferred with the yellow toner image is next transferred to the magenta recording portion / image forming portion, further to the cyan recording portion / image forming portion, and further to the black recording portion.
It is sequentially supplied to the image forming unit.

In the magenta recording unit / image forming unit, the cyan recording unit / image forming unit, the black recording unit / image forming unit, the yellow (Y) in the yellow recording unit / image forming unit described above is replaced with magenta (M). , Cyan (C), and black (BK) are replaced by the same constituent members and functions, and therefore description thereof will be omitted for simplification of description.

The transfer material 8 on which the color-superimposed image is formed is sent to the fixing device 13 by sequentially passing through the yellow transfer position, the magenta transfer position, the cyan transfer position, and the black transfer position.

The fixing device 13 is composed of a heat roller incorporating a heater, and heats only the toner image which is placed on the transfer material 8 by the charge force,
The color-superposed toner images are melted and permanently fixed to the transfer material 8. The transfer material 8 on which the fixing is completed is carried out to the paper discharge tray 15 by the sending roller 14.

On the other hand, the photosensitive drums 2Y, 2M, 2C and 2BK of the respective colors that have passed the transfer position are kept at the outer peripheral speed V as they are.
The cleaning devices 6Y, 6M, 6 are driven to rotate at 0.
The residual toner and paper dust are cleaned by C and 6BK, and the surface potential is made constant by the static elimination lamps of the static eliminators 7Y, 7M, 7C and 7BK, and the charging devices 3Y, 3M, 3C and 3BK are again charged as necessary. Enter the series of processes from.

The transfer material carrying belt 12 carrying the transfer material 8 has an endless structure and has a fixing device 13.
Side driving roller 16 and driven roller 17 on the transfer material supply port side
Held by and. The driving force of the driving roller 16 is transmitted from a driving motor (not shown), and as described above, the driving roller 16 is driven so that the outer peripheral speed V0 of the photosensitive drum and the outer peripheral speed of the belt become constant.

On the other hand, the driven roller 17 has a mechanism capable of moving in a direction parallel to the transfer material conveying direction on shaft portions on both sides of the roller, and the transfer material conveying belt 12 is compressed by a compression spring 18 in a direction opposite to the transfer material conveying direction. Pressed to apply a tensile load to. A mechanism that allows the driven roller 17 to move in a direction parallel to the transfer material conveyance direction is a slotted hole (not shown) provided in the frame and a driven roller 17 that slides the slotted hole and allows the driven roller 17 to rotate. It is composed of a roller holding member 21.

After the transfer material 8 is sent to the fixing device 13, the transfer material conveying belt 12 is cleaned by the belt cleaning device 22 to remove the residual toner and paper dust attached to the surface of the belt. To transport.

Further, in the case of monochromatic printing, the above-mentioned arbitrary monochromatic recording portion and image forming portion perform image formation. At this time, the recording unit and the image forming unit other than the selected color do not operate.

Now, the photosensitive drums 2Y, 2M, 2 for each color
As shown in FIG. 2 and FIG. 3 (only the portion of the yellow photoconductor drum 2Y is shown), C and 2BK are provided with elliptical cams 24 at both ends of the rotary shaft sandwiching the photoconductor drum 2Y via bearings 23. Has been. The elliptical cam 24 is connected to an elliptic cam actuator 25, and the actuator 25 is driven by an actuator driving section 26. The actuator drive unit 26 is controlled by a main CPU (central processing unit) 27 that controls the entire apparatus. Main CPU
27 issues commands for various operations in accordance with preset programs.

Further, the transfer devices 5Y, 5M, 5C for the respective colors,
As shown in FIG. 2 and FIG. 3 (only the part of the yellow transfer device 5Y is shown), the 5BK is a transfer roller 28 that transfers a toner image onto the transfer material 8, and a rotation shaft 29 of the transfer roller 28. It is composed of a possible guide roller 30, an insulating pressing spring 31 that presses the transfer roller 28 against the photosensitive drum 2Y, and a transfer device base (not shown) that holds the pressing spring 31. In addition, the transfer devices 5Y, 5M, 5C, and 5BK for each color include a voltage supply unit (not shown) that supplies a transfer voltage to the transfer roller 28 from the rear side of the device.

The guide roller 30 of the transfer roller 28
Is caused by the action of the pressing spring 31.
The Y-shaped elliptical cam 24 is arranged so as to be constantly pressed and contacted.

With such a structure, when the normal full-color image is formed, the photoconductor drums 2Y, 2M, 2 for the respective colors are formed.
As shown in FIG. 2, the elliptic cam 24 of C, 2BK has the actuator 25 so that the actuator 25 can contact the guide roller 30 of the transfer roller 28 of the transfer device 5Y, 5M, 5C, 5BK at its short radius position. Via CP
The position is controlled by the signal from U27. The short radius of the elliptical cam 24, together with the radius of the guide roller 30 of the transfer roller 28 pressed by the elliptical cam 24, causes the transfer roller 28 to move the transfer material transport belt 12 to the photosensitive drums 2Y, 2 under optimum conditions.
The conditions for pressing M, 2C and 2BK are set.

Therefore, the photosensitive drums 2Y, 2 of each color are
M, 2C, 2BK and transfer device 5Y, 5M, 5C, 5BK
The relationship with is as shown in FIG. In this state, when the transfer material 8 is placed on the transfer material transfer belt 12 and is sequentially transferred to each transfer position, the photosensitive drums 2Y, 2M, 2C, 2BK.
The upper toner image is sequentially transferred onto the transfer material 8.

On the other hand, in the case of forming a monochromatic image, this is realized by the operation described below. That is, the elliptical cam 24 arranged on the photoconductor drum of the selected color is
As shown in FIG. 2, the short radius position is in contact with the guide roller 30 of the transfer roller 28 of the corresponding transfer device.
The position of the actuator 25 is controlled by a signal from the CPU 27 via the actuator drive unit 26.

Further, as shown in FIG. 3, the elliptical cam 24 arranged on the photosensitive drum other than the selected color is in contact with the guide roller 30 of the transfer roller 28 of the transfer device whose major radius position corresponds. As described above, the position of the actuator 25 is controlled by the signal from the CPU 27 via the actuator drive unit 26. The major radius of the elliptical cam 24 is
Along with the radius of the guide roller 30 of the transfer roller 28 that is pressed against this, the transfer roller 28 is moved by the transfer material conveying belt 12
Is separated from the photosensitive drum, and the condition is set such that it is located at a distance where it does not contact.

Therefore, the photosensitive drums 2Y, 2 of each color are
M, 2C, 2BK and transfer device 5Y, 5M, 5C, 5BK
The relationship with is as shown in FIG. In this state, even if the transfer material 8 is placed on the transfer material transport belt 12 and is transported to the transfer position of the photosensitive drum other than the selected color, the transfer material transport belt 12 does not contact the surface of the photosensitive drum. In addition,
FIG. 4 shows a case where black is selected.

Specifically, a DC solenoid and a spring are used as the actuator 25. When the photoconductor drums 2Y, 2M, 2C, 2BK and the transfer roller 28 are brought into contact with each other, the solenoid is off, and the elliptical cam 24 is rotated to the short radius position by the compression force of the spring and set. Conversely, the photosensitive drums 2Y, 2M,
When the 2C and 2BK are separated from the transfer roller 28, the solenoid is turned on and the spring extends, whereby the elliptical cam 24 is rotated to the major radius position and set in position.

That is, as shown in FIG. 3, in the transfer material conveying belt 12, the transfer roller 28 has the photosensitive drum 2Y (2
M, 2C, 2BK), it is arranged so as to be located away from the photoconductor drum 2Y (2M, 2C, 2BK) when it is not in the pressing position. Then, as shown in FIG. 2, the transfer roller 28 causes the photosensitive drum 2Y (2M, 2C,
2BK), the transfer material transport belt 12 is pulled up to the photosensitive drum 2Y (2M, 2C, 2BK). At this time, the transfer material transport belt 12 easily moves to the photosensitive drum 2Y (2M, 2C, 2).
The driven roller 17 of the transfer material transport belt 12 is structured so that its shaft portion 32 can move in a direction parallel to the transfer material transport direction so that it can be pulled up to (BK).

Thus, at the position of the short radius of the elliptical cam 24, the position of the long radius of the elliptical cam 24 at the position where the transfer roller 28 presses the transfer material transport belt 12 against the photosensitive drum 2Y (2M, 2C, 2BK). Then, the transfer roller 28 moves the transfer material conveying belt 12 to the photosensitive drum 2Y (2M, 2C, 2B).
By controlling the position so that the photosensitive drum is separated from K), the required photosensitive drum can be easily selected and brought into contact with the transfer material 8 only when necessary.

FIG. 6 shows an example of a control flow chart in the first embodiment. First, when the start key is pressed, it is determined whether or not full color printing (full color image formation) is performed. In the case of full-color printing, the yellow, magenta, cyan, and black actuators 25 are turned off, and the short radius position of the elliptical cam 24 is set to the transfer roller 2.
No. 8 guide roller 30 is set. Next, the transfer material 8 is conveyed and printing is performed. Then, it is determined whether or not a plurality of copies have been made, and according to this determination, the above processing is executed a necessary number of times. In the case of monochromatic printing (monochromatic image formation), position control for monochromatic is performed as shown in the flowchart.

As described above, according to the first embodiment, only a single color image is required due to the structure in which only one photosensitive drum and the transfer material transport belt 12 are selectively brought into contact with each other. In this case, transfer material 8 to the other three photosensitive drums.
Is conveyed in a non-contact state, unnecessary toner remaining on the photosensitive drum adheres to the transfer material 8 to deteriorate the image quality, and unnecessary contact shortens the life of the photosensitive drum. Can be avoided.

Further, as shown in FIG. 5, at the time of warming up, the photoconductor drums 2Y, 2M, 2C, 2B.
Since the K and the transfer material transport belt 12 can be held in a state where they do not come into contact with each other at all, the photosensitive drum 2 is not contacted by unnecessary contact.
The problem of shortening the life of Y, 2M, 2C, 2BK can be synergistically avoided. Next, a second embodiment will be described.

In the second embodiment, the four colors of yellow, magenta, cyan, and black described in the first embodiment are not formed as single color images, but in particular, full color image formation and black single color image formation are performed. The present invention is applied to an image forming apparatus that switches between the two types.

That is, as shown in FIG. 7, the yellow photoconductor drum 2Y and the cyan photoconductor drum 2C are elliptical with bearings 23Y and 23C at both ends sandwiching the photoconductor drums 2Y and 2C of their rotation shafts. Cam 24
Y and 24C are provided. Elliptical cam 24Y, 24C
Are connected to a yellow elliptic cam actuator 25Y and a cyan elliptic cam actuator 25C, respectively, and these actuators 25Y and 25C are driven by actuator driving units 26Y and 26C. The actuator drive units 26Y and 26C are the main CPU 27.
Controlled by. The main CPU 27 issues various operation commands according to preset programs.

The yellow, magenta, and cyan transfer devices 5Y, 5M, and 5C are arranged in one transfer holder 34, and transfer rollers 2 for transferring the toner images of the respective colors.
8Y, 28M, 28C, rotatable guide rollers 30Y, 30C provided on rotary shafts 29Y, 29C of yellow transfer roller 28Y and cyan transfer roller 28C, transfer rollers 28Y, 28M, 28C on photosensitive drum 2Y,
Insulating pressure spring 35Y that presses against 2M and 2C,
35C, a transfer device base (not shown) that holds the pressing springs 35Y and 35C. In addition,
Yellow, magenta, and cyan transfer rollers 28Y, 28
The axial positions of M and 28C are fixed to the transfer holder 34 in a rotatable state.

In addition, transfer devices 5Y, 5M, 5 for each color
Transfer rollers 28Y, 28M, 28C,
28BK includes a voltage supply unit (not shown) for supplying a transfer voltage from the rear side of the apparatus.

The guide rollers 30Y and 30C of the transfer rollers 28Y and 28C are the pressing springs 35Y and 35C.
By the action of C, the elliptic cam 2 of the photoconductor drums 2Y, 2C
It is arranged so as to be constantly pressed by 4Y and 24C so as to be in contact therewith.

With such a structure, during normal full-color image formation, the elliptic cams 24Y and 24C of the photoconductor drums 2Y and 2C have their short radius positions at the guide rollers of the transfer rollers 28Y and 28C, as shown in FIG. 30Y, 3
The actuators 25Y and 25C are connected to the CPU 2 via the actuator drive units 26Y and 26C so as to be in contact with 0C.
The position is controlled by the signal from 7. Oval cam 2
The short radius of 4Y, 24C is the same as the radius of the guide rollers 30Y, 30C of the transfer rollers 28Y, 28C pressed against it, and the transfer rollers 28Y, 28M, 28C set the transfer material conveying belt 12 to the photosensitive drum 2Y under optimum conditions. 2M, 2
The condition for pressing C is set.

Therefore, the photosensitive drums 2Y, 2 of each color are
M, 2C, 2BK and transfer device 5Y, 5M, 5C, 5BK
The relationship between and is as shown in FIG. In this state, when the transfer material 8 is placed on the transfer material transfer belt 12 and is sequentially transferred to each transfer position, the photosensitive drums 2Y, 2M, 2C, 2BK.
The upper toner image is transferred onto the transfer material 8.

On the other hand, in the case of black monochromatic image formation, this is realized by the operation described below. That is, as shown in FIG. 8, the elliptic cams 24Y and 24C arranged on the yellow and cyan photoconductor drums 2Y and 2C have guide rollers 30 of which the major radius positions are the transfer rollers 28Y and 28C.
Actuators 25Y, 2 so as to contact Y, 30C
5C is CC through the actuator drive units 26Y and 26
The position is controlled by a signal from the PU 27.

The major radii of the elliptical cams 24Y and 24C are the same as the radii of the guide rollers 30Y and 30C of the transfer rollers 28Y and 28C pressed by the transfer rollers 28Y and 2C.
8M and 28C connect the transfer material conveying belt 12 to the photosensitive drum 2
The condition is set such that the device is separated from Y, 2M, and 2C and is positioned at a distance where it does not contact.

Therefore, the photosensitive drums 2Y, 2 of each color are
M, 2C, 2BK and transfer device 5Y, 5M, 5C, 5BK
The relationship with is as shown in FIG. In this state, the transfer material 8 is placed on the transfer material conveying belt 12 and the photosensitive drum 2
The transfer material transport belt 12 does not contact the surface of the photoconductor drums 2Y, 2M, and 2C even if the transfer material transport belt 12 is transported to the transfer positions of Y, 2M, and 2C. In addition, the structure and operation method of the actuator is
Since it is similar to the first embodiment described above, the description thereof is omitted here.

That is, as shown in FIG. 8, when the transfer rollers 28Y, 28M and 28C are not in the pressing positions against the photosensitive drums 2Y, 2M and 2C, the transfer material conveying belt 12 has the photosensitive drums 2Y and 2M. , 2C are arranged so as to be apart from each other. Then, as shown in FIG.
The transfer rollers 28Y, 28M, and 28C are the photosensitive drums 2.
When it is in a position where it is pressed against Y, 2M and 2C, the transfer material transport belt 12 is pulled up to the photosensitive drums 2Y, 2M and 2C. At this time, the driven roller 17 of the transfer material transport belt 12 is arranged so that the transfer material transport belt 12 can be easily pulled up to the photoconductor drums 2Y, 2M, and 2C in a direction parallel to the transfer material transport direction.
It is structured so that 2 can move. The black transfer roller 28BK is in a fixed position as shown in FIG. 7, and is always in a position where the photosensitive drum 2BK and the transfer material 8 are in contact with each other.

Thus, at the positions of the short radiuses of the elliptical cams 24Y and 24C, the yellow, magenta and cyan transfer rollers 28Y, 28M and 28C press the transfer material conveying belt 12 against the photosensitive drums 2Y, 2M and 2C. At the long radius positions of the elliptical cams 24Y and 24C.
8M and 28C connect the transfer material conveying belt 12 to the photosensitive drum 2
By controlling the position so as to separate from Y, 2M, 2C, all the photosensitive drums 2Y, 2M, 2C, 2B can be easily formed only when full-color image formation is performed.
K can be brought into contact with the transfer material 8. Since the adjustment printing of the printing position is the same as that of the first embodiment, the duplicated description will be omitted here and the description will be omitted.

As described above, according to the second embodiment, only the black photosensitive drum 2BK or all the photosensitive drums 2Y, 2M, 2C and 2BK and the transfer material conveying belt 12 are selectively used. In the case where only the black monochromatic image is required due to the structure of contacting with, the transfer material 8 is conveyed to the other three photoconductor drums in a non-contact state, so that unnecessary toner remaining on the photoconductor drums is generated. Attached to the transfer material 8,
It is possible to avoid the problem that the image quality is degraded and the life of the photosensitive drum is shortened due to unnecessary contact. Next, a third embodiment will be described.

The third embodiment is the same as the first embodiment except that
By providing each of the transfer devices of each color with a travel guide roller that guides the travel of the transfer material transport belt, a deformation stress is not applied to the transfer roller.

That is, as shown in FIGS. 10 and 11, the transfer devices 5Y, 5M, 5C and 5BK for the respective colors (only the yellow transfer device 5Y is shown) are transfer rollers for transferring the toner image on the transfer material 8. 28, a rotatable guide roller 30 provided on a rotation shaft 29 of the transfer roller 28, and a rotation shaft parallel to the transfer roller 28, which are arranged in front of and behind the transfer roller 28, respectively.
2, a pair of running guide rollers (running guide means) 19 that are driven to rotate, a running guide bearing 20 that allows the running guide roller 19 to rotate, and a transfer holder 34 that holds the transfer roller 28 and the pair of running guide rollers 19. ,
The photosensitive drum 2Y includes a pressing spring 35 that presses the transfer roller 28, and a transfer device base (not shown) that holds the pressing spring 35.

The guide roller 30 of the transfer roller 28
Is arranged so as to be constantly pressed and contacted by the elliptic cam 24 of the photosensitive drum 2Y by the pressing spring 35 which presses the transfer holder 34.

With such a structure, at the time of forming a normal full-color image, the photosensitive drums 2Y, 2M, 2 of the respective colors are formed.
As shown in FIG. 10, the position of the elliptical cam 24 of C, 2BK is controlled by a signal from the CPU 27 via the actuator drive unit 26 by the actuator 25 so that its short radius position contacts the guide roller 30 of the transfer roller 28. Has been done. The short radius of the elliptical cam 24, together with the radius of the guide roller 30 of the transfer roller 28 pressed against it,
The transfer roller 28 is set under conditions that press the transfer material conveying belt 12 against the photosensitive drums 2Y, 2M, 2C, and 2BK under optimum conditions.

Therefore, the photosensitive drums 2Y, 2 of each color are
M, 2C, 2BK and transfer device 5Y, 5M, 5C, 5BK
The relationship between and is as shown in FIG. In this state, when the transfer material 8 is placed on the transfer material transfer belt 12 and is sequentially transferred to each transfer position, the photosensitive drums 2Y, 2M, 2C, 2BK.
The upper toner image is sequentially transferred onto the transfer material 8.

On the other hand, in the case of monochromatic image formation, this is realized by the operation described below. That is, the elliptical cam 24 arranged on the photoconductor drum of the selected color is
As shown in FIG. 10, the transfer roller 28 has a short radius position.
Actuator 2 so that it contacts the guide roller 30 of
5 is position-controlled by a signal from the CPU 27 via the actuator drive unit 26.

Further, as shown in FIG. 11, the elliptic cam 24 disposed on the photosensitive drum other than the selected color has an actuator 25 so that its major axis position is in contact with the guide roller 30 of the transfer roller 28. Is controlled by a signal from the CPU 27 via the actuator drive unit 26. The major axis of the elliptical cam 24 is located at a distance such that the transfer roller 28 separates the transfer material transport belt 12 from the photosensitive drum under the optimum conditions together with the radius of the guide roller 30 of the transfer roller 28 pressed by the elliptic cam 24. The condition is set.

Therefore, the photosensitive drums 2Y, 2 of each color are
M, 2C, 2BK and transfer device 5Y, 5M, 5C, 5BK
The relationship between and is as shown in FIG. In this state, even if the transfer material 8 is placed on the transfer material transport belt 12 and is transported to the transfer position of the photosensitive drum other than the selected color, the transfer material transport belt 12 does not contact the surface of the photosensitive drum. Note that FIG. 12 shows a case where black is selected.

Specifically, a DC solenoid and a spring are used as the actuator 25. When the photoconductor drums 2Y, 2M, 2C, 2BK and the transfer roller 28 are brought into contact with each other, the solenoid is off, and the elliptical cam 24 is rotated to the short radius position by the compression force of the spring and set. Conversely, the photosensitive drums 2Y, 2M,
When the 2C and 2BK are separated from the transfer roller 28, the solenoid is turned on and the spring extends, whereby the elliptical cam 24 is rotated to the major radius position and set in position.

That is, as shown in FIG. 11, in the transfer material conveying belt 12, the transfer roller 28 has the photosensitive drum 2Y.
When not in the pressing position to (2M, 2C, 2BK),
The photoconductor drums 2Y (2M, 2C, 2BK) are arranged apart from each other. Then, as shown in FIG. 10, the transfer roller 28 causes the photosensitive drum 2Y (2M, 2M
C, 2BK), the transfer roller 2
A pair of running guide rollers 19 on both sides of the transfer belt 8 pulls up the transfer material transport belt 12 to the photoconductor drums 2Y (2M, 2C, 2BK). At this time, the transfer material transport belt 12 is supported by the traveling guide rollers 19 and is transferred to the photosensitive drums 2Y (2M, 2C, 2B).
K). Therefore, the positional relationship between the transfer material conveyance belt 12 and the transfer roller 28 does not change during transfer or during standby (during non-transfer). Also,
Cyan, magenta, or black transfer roller 28
Also in the above, the positional relationship between the transfer roller 28 and the transfer material conveying belt 12 during the single color transfer can be kept common. Further, at this time, the driven roller 17 of the transfer material transport belt 12 is so set that the transfer material transport belt 12 can be easily pulled up to the photosensitive drum 2Y (2M, 2C, 2BK).
Has a structure in which the shaft portion 32 can move in a direction parallel to the transfer material conveyance direction.

In this way, at the position of the short radius of the elliptical cam 24, the pair of running guide rollers 1 on both sides of the transfer roller 28.
9 transfers the transfer material conveying belt 12 to the photosensitive drum 2Y (2M,
2C, 2BK) at the position of the long radius of the elliptical cam 24, the pair of running guide rollers 19 on both sides of the transfer roller 28 move the transfer material conveying belt 12 to the photosensitive drum 2Y.
(2M, 2C, 2BK) By controlling the position so that the transfer material 8 is separated from (2M, 2C, 2BK), the required photosensitive drum can be easily selected only when necessary, and the transfer roller 28 can be formed without deforming the transfer roller 28. Can be contacted.

FIG. 14 shows an example of a control flow chart in the third embodiment. First, when the start key is pressed, it is determined whether or not full color printing (full color image formation) is performed. For full color printing, yellow,
Each of the magenta, cyan, and black actuators 25 is turned off, and the short radius position of the elliptical cam 24 is set to be in contact with the guide roller 30 of the transfer roller 28.
Next, the transfer material 8 is conveyed and printing is performed. Then, it is determined whether or not a plurality of copies have been made, and the above processing is executed a necessary number of times according to this determination.

As described above, according to the third embodiment, when only one photosensitive drum and the transfer material carrying belt 12 are brought into contact with each other, only a single color image is required. Since the transfer material 8 is conveyed to the other three photoconductor drums in a non-contact state, unnecessary toner remaining on the photoconductor drums adheres to the transfer material 8 and deteriorates the image quality. It is also possible to avoid the problem that the life of the photosensitive drum is shortened due to unnecessary contact.

Further, as shown in FIG. 13, at the time of warming up, the photosensitive drums 2Y, 2M, 2C, 2
Since the BK and the transfer material transport belt 12 can be held in a state of not being in contact with each other at all, it is possible to synergistically avoid the problem that the life of the photoconductor drums 2Y, 2M, 2C and 2BK is shortened due to unnecessary contact. Further, by providing the traveling guide roller 19, it is possible to realize monochromatic image formation while maintaining all the transfer rollers 28 in the same state. Next, a fourth embodiment will be described.

The fourth embodiment is the same as the second embodiment except that
The transfer device is provided with a travel guide roller for guiding the travel of the transfer material transport belt so that no deformation stress is applied to the transfer roller.

That is, as shown in FIG. 15, the yellow, magenta, and cyan transfer devices 5Y, 5M, and 5C are
The transfer rollers 28Y, 28M, 28C arranged in one transfer holder 34 for transferring respective colors, the guide rollers 30Y, 30 provided on the rotation shafts 29Y, 29C of the yellow transfer roller 28Y and the cyan transfer roller 28C.
C, insulating pressure spring 3 for pressing the transfer rollers 28Y, 28M, 28C against the photoconductor drums 2Y, 2M, 2C
5Y, 35C, two rotatable running guide rollers 19 respectively arranged in front of the yellow transfer roller 28Y and after the cyan transfer roller 28C, and a pressing spring 35.
It is composed of a transfer device base (not shown) that holds Y and 35C.

Two running guide rollers 19 and three transfer rollers 28Y for yellow, magenta and cyan are used.
The shaft positions of 28M and 28C are fixed to the transfer holder 34 in a rotatable state.

With such a structure, during normal full-color image formation, the elliptic cams 24Y and 24C of the photoconductor drums 2Y and 2C have guide rollers of the transfer rollers 28Y and 28C whose short radius positions are as shown in FIG. 30Y,
Actuators 25Y and 25C so as to contact 30C
Via the actuator drive units 26Y and 26C
The position is controlled by a signal from 27. The short radius of the elliptical cams 24Y and 24C is the same as the radius of the guide rollers 30Y and 30C of the transfer rollers 28Y and 28C pressed by the elliptic cams 24Y and 28C. 2Y, 2M,
The condition is set to press 2C.

Therefore, the photosensitive drums 2Y, 2 of each color are
M, 2C, 2BK and transfer device 5Y, 5M, 5C, 5BK
The relationship between and is as shown in FIG. In this state, when the transfer material 8 is placed on the transfer material transfer belt 12 and sequentially transferred to each transfer position, the photoconductor drums 2Y, 2M, 2C, 2B.
The toner image on K is transferred onto the transfer material 8.

On the other hand, in the case of black monochromatic image formation, this is realized by the operation described below. That is, as shown in FIG. 16, the elliptic cams 24Y and 24C arranged on the yellow and cyan photoconductor drums 2Y and 2C have the major axis positions of the guide rollers 3 of the transfer rollers 28Y and 28C.
Actuators 25Y, 25Y, so as to contact 0Y, 30C
The position of 25C is controlled by a signal from the CPU 27 via the actuator drive units 26Y and 26C.

The major radii of the elliptical cams 24Y and 24C are the same as the radii of the guide rollers 30Y and 30C of the transfer rollers 28Y and 28C pressed against the transfer rollers 28Y and 2C.
8M and 28C connect the transfer material conveying belt 12 to the photosensitive drum 2
The condition is set such that the device is separated from Y, 2M, and 2C and is positioned at a distance where it does not contact.

Therefore, the photosensitive drums 2Y and 2Y of the respective colors are
M, 2C, 2BK and transfer device 5Y, 5M, 5C, 5BK
The relationship with is as shown in FIG. In this state, the transfer material 8 is placed on the transfer material conveying belt 12 and the photosensitive drum 2
The transfer material transport belt 12 does not contact the surface of the photoconductor drums 2Y, 2M, and 2C even if the transfer material transport belt 12 is transported to the transfer positions of Y, 2M, and 2C.

That is, as shown in FIG. 16, in the transfer material conveying belt 12, when the transfer rollers 28Y, 28M, 28C are not in the pressing positions against the photoconductor drums 2Y, 2M, 2C, the photoconductor drums 2Y, 2M. , 2C are arranged so as to be apart from each other. Then, as shown in FIG. 15, when the transfer rollers 28Y, 28M, 28C are at the pressing positions against the photoconductor drums 2Y, 2M, 2C, the traveling guide roller 19 causes the transfer material conveying belt 12 to move to the photoconductor drum 2
It is structured to pull up to Y, 2M and 2C.

In this way, at the short radius positions of the elliptical cams 24Y and 24C, positions at which the yellow, magenta and cyan transfer rollers 28Y, 28M and 28C press the transfer material conveying belt 12 against the photosensitive drums 2Y, 2M and 2C. At the long radius positions of the elliptical cams 24Y and 24C.
8M and 28C connect the transfer material conveying belt 12 to the photosensitive drum 2
By controlling the position so as to separate from Y, 2M, 2C, all the photosensitive drums 2Y, 2M, 2C, 2B can be easily formed only when full-color image formation is performed.
K can be brought into contact with the transfer material 8.

As described above, according to the fourth embodiment, only the black photosensitive drum 2BK or all the photosensitive drums 2Y, 2M, 2C and 2BK and the transfer material conveying belt 12 are selectively used. In the case where only the black monochromatic image is required due to the structure of contacting with, the transfer material 8 is conveyed to the other three photoconductor drums in a non-contact state, so that unnecessary toner remaining on the photoconductor drums is generated. Attached to the transfer material 8,
It is possible to avoid the problem that the image quality is degraded and the life of the photosensitive drum is shortened due to unnecessary contact. Further, by providing the traveling guide roller 19, it is possible to realize monochromatic image formation while maintaining the transfer rollers at all positions in the same state. Next, a fifth embodiment will be described.

In the fifth embodiment, the position (state) of the transfer material is detected, and the position of the electrostatic latent image formed on the photosensitive drum is controlled according to the detected position. , FIG. 17 to FIG. 19. Note that FIG. 17 is a schematic configuration diagram of the entire apparatus, FIG. 18 is a control flowchart, and FIG. 19 is a processing flowchart for determining whether correction is possible.

First, the control method will be briefly described with reference to FIG. When the start key is pressed, it is determined whether the selected printing (image formation) is full color printing or black monochromatic printing. For full-color printing, prepare all transfer material detectors for operation. Next, the process speed condition of the full color process mode is set. This is because, for example, the process speed is slowed down in order to sufficiently dissolve the color toners that are color-superimposed on one transfer material 8, or four sets of recording units
It is a setting for preparing the image forming unit to operate.

Next, the transfer material 8 is conveyed at the set full-color transfer material conveying speed. The position of the transferred transfer material 8 is detected by the transfer material detector 40Y. This detection result is sent to the transfer material position calculation unit 41Y, where the position of the transfer material 8 is calculated. The calculation result is sent to the Y print signal control unit 42Y. Here, the print position of the Y (yellow) print signal is adjusted according to the position of the transfer material 8.

Next, for magenta, cyan, and black, printing is performed with the same print position adjustment. Then, it is determined whether or not a plurality of copies have been made, and the above processing is executed a necessary number of times according to this determination.

Now, the adjustment of the print position will be specifically described with reference to FIG. First, the left edge corner position of the transfer material 8 is detected by the detector 40Y. The detector 40Y uses, for example, a CCD type area sensor. Detector 40Y
The main CPU so that when a part of the transfer material 8 reaches the center position of the detection width of the detector 40Y in the sub-scanning direction, the light / dark state of the entire detection area of the detector 40Y is sent to the calculation unit 41Y. Is controlled by.

The brightness of the entire detection area is determined by the detector 40.
The part where the transfer material 8 is present on Y appears as a dark state because light is blocked, and the part where the transfer material 8 is not present on the detector 40Y detects light and appears as a bright state. This data is sent to the calculation unit 41Y, but first, the inclination of the transfer material 8 is calculated from the information of the scanning direction bit.

That is, the angle is calculated by comparing the positions of the bright and dark states of the bits in the main scanning direction. The bit width of the detector 40Y (7 × 7 μm is used in this embodiment) is stored in advance, and the stored data is used for calculation. Specifically, for example, it is assumed that there is a boundary between light and dark information at the 800th bit in the main scanning direction and the 100th bit in the sub-scanning direction. On the other hand, the main scanning direction 40
If there is a boundary between light and dark information at the 0th bit and the 105th bit in the sub-scanning direction, the inclination of the transfer material 8 is θ = tan ⁻¹ {(105−100) × 7 / 800−400) × 7} =
It is calculated as 0.72 °.

The angle information calculated in this way is referred to for determining whether or not correction is possible. This is a certain value or more, the transfer material 8
If is tilted, the line buffer prepared for the correction cannot be used for the correction, so that the judgment is made in advance. Specifically, the resolution is now 40 at 0.72 °.
To correct 0DPI, A4 size, X = (210 × tan 0.72 °) /0.0635=41.5

That is, a line buffer for 42 lines is required. In this embodiment, it is possible to correct a maximum inclination of 1 °, and the minimum line buffer 5 for that purpose
A line buffer for 100 lines, which exceeds 8 lines, is prepared. Further, this inclination angle needs to be corrected in the sub-scanning direction as well, so Y '= (297 x tan 0.72 °) = 5.2 mm, that is, the minimum length of the line buffer in the main-scanning direction required for correction [ 210mm + 5.2 × 2 = 220.4m
m], which is 230 mm.

If the transfer material 8 is tilted by more than this maximum tilt angle, it is determined that correction is impossible and the image forming operation is interrupted.
The transfer material 8 is discharged to the discharge tray 15 as it is, and the next transfer material 8 is automatically conveyed.
Further, at this time, a message indicating that the transfer material 8 is not conveyed properly is displayed on an operation panel (not shown) (see FIG. 19).

As an application example, when the transfer material 8 is tilted by more than the maximum tilt angle, the correction may not be possible and the image forming operation may be interrupted and an error message may be displayed on the operation panel.

The position information is given by searching the transmitted light / dark information in the sub-scanning direction. That is, if there is dark information in the sub-scanning line of the 1st bit in the main scanning direction, or if there is no dark information in the sub-scanning line of the 2nd bit in the main scanning direction, or if there is dark information in the sub-scanning line of the 3rd bit in the main scanning direction. If there is dark information or no dark information in the sub-scan line of,
Then, the search is continued, and the position where the dark information is first found is the left corner of the transfer material 8. This position information is also subject to judgment as to whether correction is possible. This is to judge in advance when the positional deviation of the transfer material 8 in the sub-scanning direction exceeds a certain value because the line buffer prepared for the correction cannot complete the correction. Since this judgment is almost the same as the above judgment, the description will be omitted to avoid duplication.

Also here, if the transfer material 8 is tilted more than the maximum tilt angle, the image forming operation is interrupted because it cannot be corrected, and the transfer material 8 is discharged to the paper discharge tray 15 as it is and automatically. Then, the next transfer material 8 is conveyed. At this time, a message indicating that the transfer material 8 is not conveyed properly is displayed on the operation panel.

As an application example, when the transfer material 8 is tilted by more than the maximum tilt angle, the correction may not be possible, the image forming operation may be interrupted, and an error message may be displayed on the operation panel.

Next, correction of print data will be described. The image data sent to the Y print signal control unit 42Y is written in the line buffer 43Y by the Y print signal control unit 42Y based on the data from the calculation unit 41Y. Here, the image data is converted into a form according to the detected tilt angle of the transfer material 8 and the position information. And
The solid-state scanning head 1Y exposes the photosensitive drum 2Y according to the data in the line buffer 43Y. By the control method described above, even if the transfer material 8 is conveyed to the transfer position in an inclined state, it is possible to transfer an image according to the inclination of the transfer material 8.

On the other hand, in the case of black monochromatic printing, as shown in the flowchart of FIG. 18, first, only the transfer material detector 40BK arranged in front of the black photosensitive drum 2BK is prepared for operation. Next, the process speed condition of the black monochromatic process mode is set. In this case, since only the black toner is transferred onto one transfer material 8 in this case, reset the process speed so that the toner is sufficiently melted, and the other three sets of yellow, magenta and cyan recording parts This is a setting for preparing the image forming unit so that it does not operate.

Next, the transfer material 8 is conveyed at the set black monochromatic transfer material conveying speed. The transferred transfer material 8 is transferred to the black photosensitive drum 2BK, and the angular position of the left side portion of the transfer material 8 is detected by the detector 40Bk. This detection result is sent to the transfer material position calculation unit 41BK, where the position of the transfer material 8 is calculated. This calculation result is BK
It is sent to the print signal control unit 42BK. Here, the print position of the BK (black) print signal according to the position of the transfer material 8 is adjusted.

Next, printing is performed with the printing position adjusted. Then, it is determined whether or not a plurality of copies have been made, and the above processing is executed a necessary number of times according to this determination. Since the adjustment of the print position is the same as the above, the description is omitted here.

As described above, the tip of the transfer material 8 is detected, and the latent image formation is adjusted based on the detected corners.
The printing positions in the sub-scanning direction with respect to the delay or the advance can be made to match between the photoconductor drums. at the same time,
By detecting the tilt angle and determining the latent image formation based on the tilt angle, the printing position with respect to the meandering of the transfer material 8 can be made to match between the photoconductor drums.

As an application example, a plurality of detectors are used according to the size of the transfer material, or the detectors are installed only in front of the first transfer position (yellow photoconductor drum 2Y).
It is conceivable to adopt a method of adjusting the exposure adjustment to all the photoconductor drums.

As described above, according to the fifth embodiment, the position of the left corner of the leading edge of the transfer material 8 is detected, and the print position is adjusted according to the detected position, whereby the transfer material transport belt 12 is moved.
Problems such as color shift due to meandering can be solved easily and at low cost.

Further, by detecting the position of the transfer material 8 and adjusting the print position in accordance with the detected position, the transfer material conveying belt 1
The problem such as the color misregistration due to the meandering 2 can be solved easily at a low cost, and when the correction cannot be performed, the transfer material 8 is discharged as it is, so that the jam processing is not wasted.

The present invention is not limited to the above-described embodiment, for example, a printer using a laser optical system, a printer that is not a full-color printer, and can be variously modified and used without departing from the scope of the invention. You can

[0112]

As described in detail above, according to the present invention, various problems caused by contact of a transfer material with an image carrier other than the required image carrier can be easily avoided and solved. It is possible to provide an image forming apparatus that can do this.

Further, according to the present invention, it is possible to provide an image forming apparatus capable of solving color misregistration of an image on a transfer material due to meandering of a conveyor belt constituting a transfer material conveying means.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a four-tandem tandem full-color copying machine according to a first embodiment.

FIGS. 2A and 2B show in detail a state at the time of creating a yellow single-color image in the first embodiment. FIG. 2A is a side view and FIG.
The figure is a front view.

3A and 3B show in detail a state other than the yellow image creation in the first embodiment, where FIG. 3A is a side view and FIG.
The figure is a front view.

FIG. 4 is a schematic diagram showing a state during formation of a black monochromatic image in the first embodiment.

FIG. 5 is a schematic diagram showing a standby state in the first embodiment.

FIG. 6 is a diagram showing an example of a control flowchart in the first embodiment.

7A and 7B schematically show the configuration of a four-tandem tandem type full-color copying machine according to a second embodiment. FIG. 7A is a side view and FIG. 7B is a front view.

8A and 8B show a state during formation of a black monochromatic image in the second embodiment, wherein FIG. 8A is a side view and FIG. 8B is a front view.

FIG. 9 is a diagram showing a state at the time of creating a full-color image in the second embodiment.

FIG. 10 is a detailed view showing a state at the time of creating a yellow single-color image in the third embodiment, in which (a) is a side view,
(B) The figure is a front view.

FIG. 11 is a detailed view showing a state other than the yellow image creation in the third embodiment, in which (a) is a side view,
(B) The figure is a front view.

FIG. 12 is a schematic view showing a state during formation of a black monochromatic image in the third embodiment.

FIG. 13 is a schematic diagram showing a standby state in the third embodiment.

FIG. 14 is a diagram showing an example of a control flowchart in the third embodiment.

15A and 15B schematically show the configuration of a four-tandem tandem type full-color copying machine according to a fourth embodiment. FIG. 15A is a side view and FIG. 15B is a front view.

16A and 16B show a state during formation of a black monochromatic image in the fourth embodiment, wherein FIG. 16A is a side view and FIG. 16B is a front view.

FIG. 17 is a configuration diagram schematically showing a 4-drum tandem type full-color copying machine according to a fifth embodiment.

FIG. 18 is a diagram showing an example of a control flowchart in the fifth embodiment.

FIG. 19 is a diagram showing a main part of a control flowchart in the fifth embodiment.

[Explanation of symbols]

1Y, 1M, 1C, 1BK ... Solid-state scanning head, 2Y,
2M, 2C, 2BK ... Photosensitive drum (image carrier), 3
Y, 3M, 3C, 3BK ... Charging device, 4Y, 4M, 4
C, 4BK ... Developing device, 5Y, 5M, 5C, 5BK ...
... transfer device, 8 ... transfer material, 12 ... transfer material conveying belt, 13 ... fixing device, 16 ... driving roller, 17 ...
Driven roller, 18 ... compression spring, 19 ... running guide roller, 24 ... elliptical cam, 25 ... cam actuator, 26 ... actuator drive unit, 27 ... main CPU, 28 ... transfer roller, 30 ... ... guide roller, 31 ... insulating pressing spring, 33 ... cam spring, 34 ... transfer holder, 35 ... pressing spring, 40Y, 40M, 40C, 40BK ... transfer material detector, 41Y, 41M, 41C , 41BK ... Transfer material position calculation unit, 42Y, 42M, 42C, 42BK ... Print signal control unit, 43Y, 43M, 43C, 43BK ... Line buffer.

Claims (4)

[Claims] 1. A plurality of image forming units which are provided corresponding to a plurality of image carriers that are sequentially arranged and form images on the respective image carriers, and the image carrier by the image forming units. In order to transfer the image formed on the transfer material to the transfer material, a transporting means that sequentially transports the transfer material to each of the image carriers, and the transfer material transported by the transporting means to each of the image carriers. An image forming apparatus comprising: a transfer material contacting / separating unit for selectively contacting and separating. 2. A plurality of image forming means which are provided corresponding to a plurality of image carriers that are sequentially arranged, and which form images on the image carriers, respectively, and a plurality of image forming units for the image carriers. A belt-shaped conveying means for conveying the transfer material, a transfer material contacting / separating means for selectively contacting / separating the transfer material conveyed by the conveying means with respect to each of the image carriers, and the transfer material contacting / separating means. An image forming apparatus comprising: a travel guide unit that guides the travel of the belt-shaped transport unit when the transfer material comes in and out of contact. 3. A plurality of image forming means which are provided respectively corresponding to a plurality of image carriers that are sequentially arranged, and which form an image by performing main scanning and sub scanning on each image carrier, respectively. Transporting means for sequentially transporting the transfer material to each of the image carriers, and transporting state detecting means for detecting a transporting state of the transfer material transported by the transporting means on the upstream side of each of the image bearing bodies, Scanning direction position control means for controlling the main scanning direction position and the sub scanning direction position of the image formed on the image carrier by each of the image forming means based on the detection result of the conveyance state detecting means. An image forming apparatus characterized by. 4. A plurality of image carriers that are sequentially arranged and provided corresponding to each of the image carriers, and images are formed by performing main scanning and sub scanning on the respective image carriers. A plurality of image forming units, a transport unit that sequentially transports the transfer material to each image carrier, and a shift of the transport state of the transfer material that is transported by the transport unit on the upstream side of each image carrier. And a main scanning direction position of the image formed on the image carrier of each of the image forming units based on the deviation of the transfer state of the transfer material detected by the transport state detecting unit, and the sub-scanning. When the deviation between the scanning direction position correction means for correcting the respective directional positions and the conveyance state of the transfer material detected by the conveyance state detection means exceeds the maximum correction amount for image formation on the image carrier, the transfer material is detected. I will discharge An image forming apparatus characterized by including a control means for controlling.