JPH05346741A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a separation destaticizer from being influenced by the spring of a recording material in an advancing direction when the recording material rushes in a fixing device by providing a means for adjusting the position of a separation means with respect to the fixing device. CONSTITUTION:A separation charger is constituted to be moved between a 1st position 61 and a 2nd position 61' by a moving means consisting of a pressing spring and an electromagnet, etc. An image forming device main body fetches recording material size information from a recording material size detection member provided in a paper supply cassette to which paper is supplied. For example, in the case of laterally feeding the paper of A4 size, the separation charger is previously moved to the 2nd position 61'. When transfer is finished in such a state, the recording material is separated from a recording material carrying belt 8 while it is destaticized by the separation charger at the end on the paper ejection side of the belt 8. Then, it is carried to the fixing device 7 by a 2nd carrying belt 21, and a toner image on the recording material is fixed by the fixing device 7. Thus, the separation charger is deviated from a position influenced by the spring of the trailing edge of the recording material.

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 such as a copying machine, a facsimile or a printer, which obtains a hard copy by forming an image on a recording material by utilizing an electrophotographic system or an inkjet system.

[0002]

[Prior Art]

(1) Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a recording material in which an image is formed outside the apparatus after feeding the recording material to the recording material and fixing the image on the transferred recording material. It is usual to have a series of transportation paths such as discharging the. For example, in a color electrophotographic apparatus as shown in FIG. 5, a plurality of photosensitive drums 1 as image carriers are provided.
The toner images formed on a, 1b, 1c, and 1d are sequentially and multiple-transferred onto the recording material 9 by the action of the plurality of transfer chargers 5a, 5b, and 5d. Then, the toner image of the recording material 9 on which the multi-transfer is completed is heated and fixed by the fixing device 7, and is discharged to the outside of the device.

At this time, the recording material 9 is taken out from the paper feeding cassette 60, then sent through the registration rollers 13 and onto the conveyor belt 8 of the first recording material carrying means, and is recorded by an adsorption charger (not shown). The material 9 is attracted to the conveyor belt 8.
The recording material 9 is composed of the plurality of photosensitive drums 1a as described above.
After receiving the transfer of the toner image from 1d to 1d, the separation charger 6
The charging roller 7a receives a driving force and the pressing roller 7b is driven by the conveyor belt 21 of the second recording material carrying means, which is formed of a rubber belt or the like having a surface layer having a high friction coefficient, which is destaticized by 1 and separated from the conveyor belt 8. Is sent to the fixing device 7 that is being rotated.

By the way, the second conveyor belt 21 is provided for the following reason.

First, it is difficult to make the peripheral velocities of the first conveyor belt 8 and the heating roller 7a which receive the rotational driving force of the fixing device 7 completely coincide with each other due to the accuracy of each part. .. Therefore, the peripheral speed of either the transport belt 8 or the heating roller 7a driven by the fixing device 7 is increased. Here, when the peripheral speed of the heating roller 7a is faster, when the front end of the recording material 9 reaches the fixing device 7, a part of the rear end side of the recording material 9 is below the image forming portion. The problem that the recording material 9 being transferred is pulled by the roller pair of the heating roller 7a and the pressure roller 7b during transfer of the toner image on the photosensitive drum, resulting in transfer deviation and image disturbance. was there. Therefore, it is usual that the peripheral speed of the heating roller 7a is always set to be lower than the peripheral speed of the conveyor belt 8 even if there is some fluctuation.
In this way, the above problem of transfer deviation does not occur.

When the above-described transport belt 21 is not provided between the transport belt 8 and the fixing device 7 and only the guide plate is provided, the recording material 9 is separated from the transport belt 8. The distance between the position and the heating roller 7a of the fixing device 7 must be smaller than the length of the recording material 9 used in the conveying method. Since a recording material 9 up to a postcard size is often used in an ordinary image forming apparatus, the distance between the separation position of the recording material 9 and the heating roller 7a of the fixing device 7 is shorter than the length of the postcard in the longitudinal direction. There is a need.

However, with such a construction, inconvenience particularly occurs when a recording material 9 having a long length in the carrying direction, for example, A3 size paper of Japanese Industrial Standard paper is used. This is because there is always a difference between the peripheral speed of the conveyor belt 8 and the peripheral speed of the heating roller 7a as described above, so that the tip of the recording material 9 enters the nip portion between the heating roller 7a and the pressure roller 7b. The deviation of the peripheral speed causes slack on the recording material 9. The slack increases as the length of the recording material 9 in the transport direction increases.

When such slack occurs, the recording material 9
Causes the waist to generate a force in the direction to eliminate this slack. This force becomes large when the distance between the separation position of the recording material 9 and the heating roller 7a is small. Then, the force acts on the conveyor belt 8 in the direction opposite to the traveling direction, causing problems such as color misregistration.

In order to prevent this problem from occurring, it is necessary to increase the distance between the separation position of the recording material 9 and the heating roller 7a in order to weaken the reverse force. However, in this way, it is impossible to satisfactorily convey even the smallest size paper as described above.

Therefore, the second conveyor belt 21 is provided so as to constantly apply a conveying force to the recording material 9 so as to avoid any of these problems.

(2) In the color image forming apparatus as described above, a recording material such as paper taken out from a cassette or the like is supplied to the conveyor belt 8 and conveyed, and a plurality of image formations arranged close to the conveyor belt 8 are formed. In the case of forming a color image by sequentially transferring the toner images of the respective color toners by passing through the respective portions, the recording material must be in close contact with the conveyor belt, and the recording material must be conveyed from the cassette or the like.
When supplied to the conveyor belt through one or several pairs of conveyor rollers and registration rollers, if the rollers are not synchronized with the conveyor belt, transfer misregistration occurs, resulting in deterioration of image quality such as color misregistration and image distortion. To do.

As means for bringing the recording material into close contact with the conveyor belt, the conveyor belt has a volume resistivity of 10 ¹² to 10 ¹⁷ Ωc.
It has been practiced to use a semiconductor sheet having a size of about m and apply a charge to the semiconductor sheet to electrostatically adsorb the recording material.

However, the synchronization between the conveyor belt and the conveyor system for supplying the recording material to the conveyor belt causes various causes such as dimensional accuracy of each member constituting them, accuracy of the drive transmission system, and wear of each part. I had to say it was difficult because of.

(3) FIG. 17 is a vertical sectional view for explaining the configuration of a conventional image forming apparatus different from that of FIG. Explaining the parts different from FIG. 5, the scanner units 3a, 3b, 3c and 3d which are not shown in FIG. 5 are shown in FIG. Further, in FIG. 5, the conveyor belt 2 of the second recording material carrying means is shown.
17, the separation claw guide 21A is provided in the portion including 1 and the fixing device 7 and the separation charging device 61 are close to each other.

In FIG. 17, when the transfer process is completed, the recording material 9 moves toward the separating section S. Here, first, the separation charger 6
1, the conveyor belt 8 and the recording material 9 are simultaneously discharged to remove their electrostatic attraction. The recording material 9 deprived of the suction force begins to separate from the conveyor belt 8 due to the curvature of the roller 6,
It is sent to the fixing device 7 along the separation claw guide 21A, and the multicolors superposed there are collectively fixed to obtain a desired full-color image.

However, in such an image forming apparatus, since the transfer path can be constructed on a straight line, it is adaptable to recording materials of various thicknesses and materials such as thick paper and transparent recording paper, while the recording material is There are many problems to be described later regarding reliability when separating from the transfer belt.

(4) Conventionally, after the toner image after development formed on an image bearing member such as a photosensitive drum is transferred to a recording material, the residual toner remaining on the photosensitive drum is collected by a cleaning means and is a waste toner. Most were disposed of as.

Among these, in a normal monochromatic copying machine such as a black-and-white copying machine, there has been proposed a structure in which the toner collected by the cleaning means is reused.

[0019]

[Problems to be Solved by the Invention]

(1) In the above-mentioned conventional technique (1), is the length of the recording material 9 in the transport direction substantially equal to the distance between the position where the recording material 9 is separated from the transport belt 8 and the heating roller 7a of the fixing device 7? When the recording material 9 is long, the suction force does not work between the recording material 9 and the second conveyor belt 21, so that when the leading end of the recording material 9 rushes into the heating roller 7a having a slow peripheral speed (recording material 9).
To prevent damage to the leading edge of the unfixed image supported by
The recording material 9 of the conveyor belt 21 is first contacted with the heating roller 7a. ), The rush shock appears as a wave propagating on the recording material 9 as shown in FIG.

The tip of the recording material 9 is heated by the heating roller 7.
When the recording material 9 whose size is such that the rear end thereof is just below the separation static eliminator 61 when the recording material 9 is rushed into the a, the recording material 9 after the recording material 9 due to the wave motion transmitted through the recording material 9 due to the rush shock described above is used. The recording material 9 is largely flipped up at the end portion, and the rear end portion of the recording material 9 is struck by the separation charge eliminator 61, disturbing the unfixed toner image, causing image disturbance, and scattering to the separation charge eliminator 61. The deposited toner image adheres to the separation charge eliminator 61, which causes a separation failure due to dirt.

According to the present invention, in the image forming apparatus which is provided with the first and second conveyor belts and conveys the recording material from the transfer portion to the fixing device, the trailing end portion in the traveling direction when the recording material enters the fixing device is provided. An object of the present invention is to provide an image forming apparatus in which the influence of the rising on the separation charge eliminator is prevented.

(2) In the above conventional technique (2), the conveyor belt 8 and the upstream side thereof (as viewed in the running direction of the recording material).
Regarding the troubles when the transport systems in can not be synchronized,
A brief description is given below with reference to FIG. FIG. 13 shows that the recording material 9 that has passed through the registration rollers 13 is placed on the conveyor belt 8 and advances in the direction of the arrow shown. Reference numeral 29 in the drawing is an adsorption charger for adsorbing the recording material 9 on the conveyor belt 8.

In this case, when the peripheral speed of the registration roller 13 is lower than the speed of the conveyor belt, the recording material 9 is pulled backward (to the right in the drawing) as shown in FIG. The transfer position of the recording material 9 is deviated, the transfer belt 8 is deformed, and transfer failure occurs.
There is a risk of color misregistration with the toner image after the color. Further, when the trailing edge of the recording material 9 passes through the registration rollers 13, the transport belt 8 is immediately restored, so that the shock may cause transfer unevenness.

On the contrary, when the peripheral speed of the registration roller 13 on the conveying system side is higher than the speed of the conveying belt 8, the recording material 9 is supplied to the conveying belt 8 more than necessary. 14 ”, the recording material 9 temporarily rises from the conveyor belt 8 and then restores due to the stiffness of the recording material 9 itself, causing inconveniences such as transfer deviation.

When the size of the recording material 9 is large, such a problem becomes remarkable, and particularly in the case of a color image, the deterioration of the image quality when visually observed becomes obvious, which is a serious defect.

In order to avoid the above drawbacks, as shown in, for example, FIG. 15, one in which the registration roller 13 is opened immediately after the recording material 9 is adsorbed by the conveyor belt 8 has been proposed. Proposed. Something like this
It is preferable if the length of the recording material 9 in the traveling direction and the positional relationship between the registration rollers 13 are suitable. However, with a large-sized recording material 9, a pair of conveyance rollers further upstream of the registration rollers 13 simultaneously sandwich the recording material. In such a case, there is no effect. On the contrary, in the case where the upstream side roller pair nips and conveys the succeeding recording material 9 with a small-sized recording material, it may cause a jam due to conveyance failure, Satisfactory results cannot be obtained. There is also a proposal to reduce the tension in the case of a large-sized recording material by adding a bearing to the roller pair on the further upstream side, but when there is a paper feed roller or a separation roller at this position, It is difficult to take the above-mentioned measures to reduce the load, and it has not been a satisfactory solution.

The present invention has been made in order to cope with the above situation, and the recording material is supplied from a recording material storage portion such as a cassette to a conveyor belt which is close to a plurality of image forming portions. In the image forming apparatus, by appropriately setting the position at which the recording material supplied to the conveyor belt is forcibly adsorbed to this, and the position of the specific conveyor roller pair included in the conveyor system on the upstream side of the recording material. It is an object of the present invention to provide an image forming apparatus capable of obtaining a high-quality image by preventing the occurrence of transfer unevenness and transfer deviation.

(3) According to the prior art (3), the first
In addition, since the electrostatic attraction force on the conveyor belt 8 varies depending on the type of recording material and the environment in which the apparatus is placed, the attraction force deprived of the charge by the separation charger 61 may change and the attraction force may remain. Separation failure is likely to occur. However, although this can be solved by increasing the charge removal capability of the separation charger more than necessary, the problem is that the toner image is scattered.

Further, if the separation claw guide 21A is brought into contact with the transfer belt 8 and the recording material is scooped up, separation mistake can be prevented, but scratches and the like occur on the surface of the conveyor belt, and durability remains a problem.

Further, the driving roller 6 can be made a roller having a small curvature to be separated according to the curvature, but there is a problem that peeling discharge is generated between the recording material and the conveying belt to cause image disturbance.

Secondly, if a separation failure occurs here, the recording material moves while being held by the conveyor belt 8 and enters the conveyor belt cleaning device 25 for removing the toner image on the surface of the conveyor belt 8 in FIG. The device may be destroyed, or the cleaning device may cause an accordion-like paper jam, which may damage the conveyor belt.
Further, when the toner easily passes through the conveyor belt cleaning device 25 and reaches the periphery of the registration roller 13, the toner on the recording material contaminates the periphery and appears as an image stain on the next copy, or the recording material appears. It also causes a decrease in the reliability of feeding.

In the present invention, the recording material carrying means wound around a plurality of rollers is disposed close to the image forming section, and the separating means separates the recording material on the downstream side of the image forming section, and on the downstream side of the separating means. An image forming apparatus is provided which solves the above-mentioned problems in an image forming apparatus including a cleaning device for a recording material carrying means and which does not affect the cleaning device or the surroundings of registration rollers due to a separation failure. The purpose is to do.

(4) In the prior art (4) described above, let us consider reusing the toner after cleaning the residual toner on the photosensitive drum in an image forming apparatus, such as a full-color copying machine, in which multicolor toners are superposed and transferred. Upon transfer of the second color, the unfixed toner of the first color transferred onto the recording material is retransferred to the photosensitive drum of the second color, and the toners of the first and second colors are transferred to the photosensitive drum of the second color. Are mixed, the tint of the second color toner introduced to the cleaning device is lowered due to the mixing of the first color toner. In transferring the third color, similarly, the unfixed toners of the first and second colors on the recording material are retransferred onto the photosensitive drum to reduce the tint of the third color, and the transfer of the fourth color. Similarly, the unfixed toners of the first color, the second color, and the third color on the recording material are retransferred to the photosensitive drum to reduce the tint of the fourth color. However, with respect to toner reuse, the prior art does not provide a guideline for a decrease in tint due to toner color mixing that occurs due to transfer of multiple colors.

The present invention has a plurality of image forming portions and prevents re-transfer of toner to the image carrier in the image forming portions for the second and subsequent colors, thereby making it possible to reuse the residual toner without color mixing. The purpose is to provide a device.

[0035]

A first invention of the present invention is a first recording material carrying means for carrying and carrying a recording material, and the first recording material carrying means.
Means for electrostatically adsorbing the recording material on the recording material carrying means, image forming means for forming an image transferred to the recording material carried on the first recording material carrying means, and first recording material Separation means for electrostatically separating the recording material from the carrying means, fixing means for fixing the image formed on the recording material to the recording material using a pair of rollers, and between the separation means and the fixing means An image forming apparatus having a second recording material carrying means for carrying and carrying the provided recording material, characterized in that it has means for adjusting the position of the separating means with respect to the fixing means. It is a device.

In a second aspect of the present invention, the position of the separating means is adjusted according to the length of the recording material carried on the first recording material carrying means in the moving direction. The image forming apparatus according to the invention.

According to a third aspect of the present invention, there is provided a first recording material carrying means for carrying and carrying the recording material, a means for electrostatically adsorbing the recording material on the first recording material carrying means, and a first recording material carrying means. Image forming means for forming an image to be transferred onto the recording material carried on the recording material carrying means, separating means for electrostatically separating the recording material from the first recording material carrying means, and a pair of rollers. An image forming apparatus having a fixing means for fixing the image formed on the recording material to the recording material, and a second recording material holding means provided between the separating means and the fixing means for carrying and conveying the recording material. The separating means comprises a plurality of separating means for electrostatically separating the recording material from the first recording material holding means, and one of the plurality of separating means is selectively one of the first recording material holding means. And a plurality of separating means, each of which is a fixing means. The distance between is an image forming apparatus, wherein different.

According to a fourth aspect of the present invention, at least one image carrier, a recording material carrying means for carrying the recording material arranged in the vicinity of the image carrying means, and an upstream side of the recording material carrying body in the carrying direction of the recording material. A recording material suction means arranged near the edge, a transfer device for transferring the image on the image carrier to the recording material, and a recording material conveying roller arranged immediately upstream of the recording material carrying means,
In an image forming apparatus in which the conveying force is released immediately before the recording material reaches the image forming portion, the maximum distance between the transfer portion and the conveying roller arranged upstream of the recording material conveying roller is recorded. The image forming apparatus is made larger than the length of the material in the conveying direction.

A fifth invention of the present invention is the image forming apparatus according to the fourth invention, wherein the image carrier on the most upstream side in the recording material conveying direction also serves as the recording material attracting means.

A sixth aspect of the present invention is an endless belt which is wound around at least one image forming portion having an image forming means around an image carrier and a plurality of rollers to successively convey a recording material. A recording material carrying means, a first separating means for separating the recording material from the recording material carrying means, and a cleaning device downstream of the first separating means for cleaning the surface of the recording material carrying means. In the image forming apparatus having the above, the image forming apparatus is characterized in that it has a second separating means between the first separating means and the cleaning device.

In a seventh aspect of the present invention, the first separating means has a discharging means for applying a high voltage and a claw-shaped separating claw guide, and separates by utilizing the curvature of one of the rollers. The second separating means is a curvature separating means formed by a roller having a curvature larger than that of the roller of the first separating means, and the image forming apparatus according to the sixth aspect of the invention. ..

According to an eighth aspect of the present invention, there is provided a separating and conveying path downstream of the second separating means, and a detecting means for detecting a defective separation recording material separated by the second separating means in the conveying path. The image forming apparatus according to the sixth invention or the seventh invention is characterized in that it has.

A ninth aspect of the present invention is provided with a plurality of image forming portions each comprising a latent image forming means, a developing device and a cleaning device for forming an image on an image bearing member, and the image forming portions are formed by the image forming portions. In an image forming apparatus having a transfer unit that transfers toner images of different colors to each other on a recording material, a control unit that prevents color mixture of toner captured by a cleaning device is provided, and the toner of the cleaning unit by the cleaning device is removed. The image forming apparatus is characterized by being reused.

A tenth aspect of the present invention is characterized in that the control means for preventing color mixture of toner conveyed by the cleaning device is a control means for preventing retransfer of toner onto the image carrier. The image forming apparatus according to the invention.

In the eleventh aspect of the present invention, the control means for preventing color mixture of the toner captured by the cleaning device is means for controlling the charge of the toner on the image carrier, and the toner image on the image carrier is The image forming apparatus according to the ninth invention or the tenth invention is characterized in that it is located before entering the transfer means.

In the twelfth aspect of the present invention, the control means for preventing the retransfer of the toner onto the image carrier includes means for strengthening the transfer electric field of each image forming portion toward the downstream image forming portion. An image forming apparatus according to a tenth invention.

[0047]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Embodiment 1] In Embodiments 1 to 3, in the case where the second recording material carrying means (conveying belt) is provided, separation of the trailing edge of the recording material caused by the recording material rushing into the fixing device causes separation. The present invention relates to the invention for the purpose of excluding the influence on the means.

First, a first embodiment of the present invention will be described with reference to FIGS.

First, the outline of the image forming apparatus will be described with reference to FIG. 2. In the drawing, Pa, Pb, Pc and Pd are image forming portions capable of forming images of black color, yellow color, magenta color and cyan color, respectively. Under the image forming portions Pa, Pb, Pc, and Pd arranged in one horizontal row, there is an endless first recording material carrier belt 8 that holds and moves the recording material 9. It is arranged.

Chargers 2a, 2b, 2c, 2d, scanner units 3a, 3b 3c, are provided around the photosensitive drums 1a, 1b, 1c, 1d which are the image bearing members of the image forming sections Pa, Pb, Pc, Pd. 3d, developing devices 4a, 4b, 4c, 4
d, transfer chargers 5a, 5b, 5c and 5d, and cleaning devices 6a, 6b, 6c and 6d. The transfer chargers 5a, 5b, 5c, 5d are positioned inside the recording material conveying belt 8, and the transfer chargers 5a, 5b, 5c, 5
d via the recording material conveying belt 8
The toner images on a, 1b, 1c and 1d are transferred onto the recording material 9 on the recording material conveying belt 8.

The recording material conveying belt 8 is made of polyurethane resin,
Both ends of a film sheet made of a dielectric resin such as PVdF (polyvinylidene fluoride) resin, PET (polyethylene terephthalate) resin, polycarbonate resin, polyether sulfone resin, polyurethane resin are endlessly formed by means of ultrasonic welding or the like. The endless belt is formed by splicing or by extrusion molding or centrifugal molding, and is driven at a constant speed (10
It is driven to rotate at 0 mm / S).

The recording material conveying belt 8 electrically holds the recording material 9 and holds the recording material 9 at each image forming portion Pa,
The multi-color image is formed on the recording material 9 by moving the recording material 9 to Pb, Pc, Pd. A separation charger 61 is provided on the paper discharge side of the recording material conveyance belt 8 for separation.

As will be better understood by referring to FIG. 1, the separation charger 61 is provided with, for example, a charging device (not shown) between the first position (shown by the solid line position) and the second position (shown by the broken line position 61 '). It is configured such that it can be moved by a moving means including a pressure spring and an electromagnet. When the separation charging device 61 is in the first position, the distance L ₁ between the charging line of the separation charging device 61 and the nip portion between the heating roller 7a and the pressure roller 7b of the fixing device 7 is increased.
2 210 mm, when the separation charger 61 is in the second position 61 ', the distance L ₂ between the nip of the heating roller 7a and a pressure roller 7b pair of the fixing device 7 and the charging line of the separation charger 61
It is configured to be 30 mm.

Further, paper feed cassettes 59, 60, paper feed rollers 15, 16 and registration rollers 13 are provided on the paper feed side of the recording material transport belt 8, and a second paper is provided on the paper discharge side of the recording material transport belt 8. The conveyance belt 21 and the fixing device 7 which are the recording material carrying means are disposed.

The image forming operation of the image forming apparatus will be described below.

First, the image formation of a black color in the image forming portion Pa will be described. When the scanner unit 3a exposes the image light L of the black image onto the photosensitive drum 1a uniformly charged by the charger 2a, An electrostatic latent image is formed on the photosensitive drum 1a. The electrostatic latent image is directed to the developing device 4a having black toner as the photosensitive drum 1a rotates, and is visualized as a black toner image by the developing device 4a. The toner image is positioned on the recording material conveying belt 8 which moves in the direction of the arrow in the drawing, and transferred onto the recording material 9 which is electrostatically adsorbed and held by an adsorption charging device (not shown) using the transfer charging device 5a. It Then, the residual toner is cleaned by the cleaning device 6a on the photosensitive drum 1a after the transfer, and the photosensitive drum 1a is prepared for the next image formation.

Further, in the image forming Pb on which a yellow image is formed, the yellow color is similarly formed on the photosensitive drum 1b uniformly charged by the charger 2b while the timing and the image forming action in the image forming Pa are planned. The image light L of the image is exposed to form an electrostatic latent image on the photosensitive drum 1b, and the electrostatic latent image is visualized as a yellow toner image by the developing device 4b having yellow toner. It Then, this toner image is transferred onto the recording material 9 onto which the black toner image transferred by the recording material transfer belt 8 is transferred via the transfer charger 5b.

Similarly, magenta and cyan images are formed by the image forming units Pc and Pd on which magenta and cyan images are formed.
A cyan toner image is formed, and the toner image is recorded on the recording material 9
By carrying out multiple transfer onto the recording material 9, a full-color image of four colors is formed on the recording material 9. On the other hand, the recording material 9 is fed from the inside of the paper feeding cassette 59, 60 to the paper feeding roller 15 or 16
Then, the sheets are taken out one by one and conveyed to the registration roller 13, and the registration roller 13 supplies the recording material on the recording material conveyance belt 8 at the same timing.

At this time, the main body 10 of the image forming apparatus takes in recording material size information from a recording material size detecting member (not shown) provided in the paper feeding cassettes 59 and 60 in which the paper is fed. When the material size is the size of Japanese Industrial Standard Paper A4 (length 297 mm, width 210 mm) and the paper is fed transversely with its longitudinal direction orthogonal to the traveling direction, the separation charger 61 is previously set to the second position 61. '(Dotted line position in FIG. 2).

In this state, the recording material 9 is sucked and held on the recording material conveying belt 8 and the four image forming portions P are formed.
Toner images of four colors are multiply transferred onto the recording material 9 while passing through a, Pb, Pc, and Pd. After the transfer, the recording material 9 is separated from the recording material conveying belt 8 while being discharged by the separating charger 61 (position 61 ') at the end of the recording material conveying belt 8 on the paper discharge side, and then the second conveying operation is performed. The belt 21 conveys the toner image to the fixing device 7, and the fixing device 7 fixes the toner image as a permanent image.

When an image is formed using such an image forming apparatus, for example, in this embodiment, A4
Even when the size paper is fed laterally, the separation charger 61 can be displaced more than the position where the trailing edge of the recording material 9 was affected by the rise of the recording medium 9 in the conventional case. Good image formation can be carried out without causing the problems shown.

[Embodiment 2] In this embodiment, in the image forming apparatus shown in the above-mentioned embodiment, as shown in FIG. 3, there are two separate chargers, that is, separate chargers 62 and 63, respectively. The distance between the nip portion between the charging line of _{No. 1} and the heating roller 7a and the pressure roller 7b of the fixing device 7 is L ₁ = 210 mm, L
_It was provided at a position where ₂ = 230 mm. Further, the separation chargers 62 and 63 each have a distance between the charging line and the recording material conveyance belt 8 of about 10 mm when in use.
It is equipped with a descending and ascending means using an electromagnet or the like that descends to a position where

In the present embodiment, when the paper is fed, for example, the A4 size paper is used as the recording material based on the recording material size information from the recording material size detecting members provided in the paper feeding cassettes 59 and 60. In the case of lateral feeding with respect to the direction, the separation charger 63 is lowered in advance to make it operable, and the separation charger 62 is raised and retracted.

When an image is formed using such an image forming apparatus, unlike the conventional example, when the A4 size paper is laterally fed in this embodiment as well, the trailing edge of the recording material 9 rises. Charger 62 affected by
Since the other separating charging device 63 is provided with the separating function, it is possible to perform good image formation without causing the problems shown in the above-mentioned conventional example.

[Embodiment 3] In this embodiment, the image forming apparatus to which the present invention is applied is substantially the same as that of the above-described Embodiments 1 and 2, except that as shown in FIG. The difference is that a manual paper feed tray 58 is provided. Further, in this embodiment, a recording material size detecting member 22 which is, for example, an optical sensor capable of detecting the recording material size is provided on the way from the paper feeding portion to the conveyor belt 8. Then, the recording material size detecting member 22 reads the difference in the passing time between the leading end portion and the trailing end portion of the recording material,
The length of the recording material 9 is calculated from the moving speed of the recording material 9 by a calculation means (not shown). Based on the calculated length of the recording material 9, the separation charger 61 is moved in parallel with the conveyor belt 8 as shown in FIG. With this configuration,
Even in an image forming apparatus having a manual paper feeding section as in the present embodiment, the size of the recording material is automatically detected, and the position of the separation charger 61 is changed according to the detected value. Good image formation can always be carried out without causing a problem.

The fourth to fifth embodiments solve the problem in the case where the recording material is supplied by the roller pair to the conveying belt which is close to the plurality of image forming portions.

"Embodiment 4" and "FIG. 7" are Embodiment 4 of the present invention.
FIG. 4 is a schematic side view of the color image forming apparatus showing four image forming units Pa, which are provided above the conveyor belt 8 suspended by a pair of driving rollers 11 and driven rollers 12 in the illustrated apparatus.
Pb, Pc and Pd are arranged. The image forming units Pa only differ in the colors of the toners used to form the toner images, so only the image forming unit Pa will be described.

A rotating cylindrical photosensitive drum 1a extending in the direction perpendicular to the plane of the drawing is disposed close to the conveyor belt 8,
The photosensitive drum 1a is uniformly charged by the primary charger 2a, and an image signal of a cyan component color due to the cyan component of the original such as an image-modulated laser beam is applied to the photosensitive drum 1a to form an electrostatic latent image. When the latent image reaches the developing portion where the developing device 4a faces the photosensitive drum 1a, the developing device 4a
Cyan toner is supplied to form a toner image.

Further, when this cyan toner image arrives at the transfer site where the transfer charger 5a is present, the recording material 9 in the cassette 60 is taken out by the paper feed roller 16 so far, passes through the conveyance roller 13a, and then the registration roller 13. Via the transfer belt 8 or through the adsorbing and charging device 29 to be adsorbed and fixed to the belt and reach the transfer portion. Transferred to 9. At this time, the residual toner that has not transferred to the recording material 9 reaches the position of the cleaning device 6a and is removed by this, and the photosensitive drum Pa is ready for the next image forming step.

Then, when the recording material 9 carrying the cyan toner image reaches the image forming portions Pb, Pc, Pd, by this time, the magenta toner image, the yellow toner image, and the black toner image are formed in the image forming portion. The recording materials 9 are formed and transferred one after another onto the recording material 9, and then the recording material 9 is separated from the conveyor belt 8 to be fixed.
Then, the toner image is fixed and fixed to form a color image and is disposed outside the apparatus.

In such an image forming apparatus, in the above apparatus, the distance La between the first image forming portion Pa and the registration roller 13 located closest to the conveyor belt 8, the registration roller 13 and the immediate upstream side thereof. Certain transport roller 13
When the distance from a is Lb and the length of the recording material 9 in the conveyance direction is Ls, La + Lb> Ls.
Further, immediately after the recording material 9 is adsorbed and placed on the conveyor belt 8 and enters the transfer portion of the first image forming portion Pa, the registration roller 13 is released by an appropriate means such as a cam (not shown). Configured.

The relationship between the progress of the recording material 9 and the image forming portion Pa on the conveying path, the registration roller 13, and the conveying roller 13a upstream of the recording material 9 in the above-described structure will be described.

FIG. 8 shows that the leading edge 9f of the recording material 9 hits the registration roller 13 and stands by at a timing before entering the image forming portion Pa before the registration roller 13, and the rear edge of the recording material 9 is shown. 9r is a recording material cassette 6
It is near 0. At this time, the recording material 9 forms a loop to prevent skew.

FIG. 9 shows that the registration roller 13 is rotated at a predetermined timing and the recording material 9 is guided to the image forming portion Pa. At this time, the peripheral speed of the registration roller 13 is the transfer speed of the transfer belt 8. The recording material 9 is slightly faster than the adsorption charging device 29, and the front end 9f of the recording material 9 is adsorbed to the conveyance belt 8 by the adsorption charging device 29 to form a loop on the front side of the adsorption charging device 29.

FIG. 10 shows the state immediately after the recording material 9 reaches the image forming portion Pa, and at this time, the registration roller 13
Is released and the loop is also released. The registration roller 13 is released by the recording material 9 in the image forming portion P.
It may be before reaching a, but after reaching the image forming portion Pa, in other words, the rear end 9r of the recording material 9 is conveyed by the transport roller 13a.
It is more suitable after passing through. This is because, immediately before the recording material 9 reaches the image forming portion Pa, the length of the portion has the relationship as described above, and therefore the recording material rear end 9
Since r is not disengaged from the transport roller 13a, the registration roller 13 is released while the roller holds the trailing edge of the recording material 9 and the loop of the recording material 9 expands, so that the shock does not affect the recording material 9. ..

Further, as the recording material 9 advances, the trailing edge 9r of the recording material 9 becomes the registration roller 13 as shown in FIG.
After passing through the roller, the roller restores and recovers the clamping force.

[Embodiment 5] and [FIG. 12] show other embodiments in comparison with Embodiment 4. In this apparatus, the adsorption charger is not provided on the conveyor belt 8. There is. In this case, the recording material 9 is conveyed to the image forming portion Pa by the conveying force of the registration rollers 13 and transferred, and is adsorbed to the conveying belt 8. That is, the photosensitive drum 1a also serves as the recording material suction means.

Even in such a configuration, by setting the distance relationship between the transfer portion, the registration roller, and the transport roller located upstream thereof as described above, a shock is generated when the recording material leaves the transport roller 13a. It is possible to avoid adverse effects.

Although the full-color image forming apparatus having four image forming portions has been described in the fourth and fifth embodiments of the present invention, the present invention is not limited to such an apparatus and one image forming portion is provided. It can be easily understood that it can be applied to a monochrome type or two color image forming apparatuses.

[Embodiment 6] Embodiment 6 relates to an apparatus for preventing inseparability when separating the recording material from the recording material carrying means that has passed through the image forming portion.

First, an example of an image forming apparatus to which the present invention can be applied will be described with reference to FIG. The image forming apparatus shown in FIG. 16 is an electrophotographic color copying machine.
The present invention is equally applicable to various image forming apparatuses such as electrophotographic systems and electrostatic recording systems. This color copying machine has a configuration in which four image forming portions Pa, Pb, Pc and Pd are linearly arranged, and each image forming means includes a dedicated photosensitive drum 1a, 1b, 1c as an image carrier and 1d
Around the photosensitive drums 1a to 1d, dedicated image forming process means, for example, chargers 2a, 2b, 2c and 2d, developing units 4a, 4b, 4c and 4 are provided.
d, transfer chargers 5a, 5b, 5c, 5d, cleaning devices 6a, 6b, 6c, 6d and laser scanner units 3a, 3b, 3c, 3d for forming image information as a latent image on the photosensitive drum. It is set up.

On the other hand, the endless conveyor belt 8 is provided below the photosensitive drums 1a to 1d so as to penetrate the image forming portions Pa to Pd.
The recording material transporting unit including the recording material is disposed, and the sheet feeding device 30 including the recording material cassette 60 that stores the recording material 9 is disposed on the right side thereof. Further, a registration roller 13 for feeding the recording material 9 at a timing is arranged between the paper feeding device 30 and the recording material conveying section, and the recording material 9 is fed from the paper feeding cassette 60 to the paper feeding roller. It is sent by 16 and is supplied to the image forming units Pa to Pd via the registration roller 13.

In the above-mentioned structure, first, the recording material 9 sent out by the paper feeding cassette 60 is temporarily stopped when the leading end of the recording material 9 is slightly sandwiched by the registration rollers 13, and the image of the first image forming portion Pa is temporarily stopped. The recording material is sent out to the recording material conveying portion at the same timing as the forming process, and is electrostatically adsorbed on the conveying belt 8 by the adsorbing means (not shown). In the first image forming unit Pa, the scanner unit 3a scans image information on the photosensitive drum 1a uniformly charged by the charger 2a to form an electrostatic latent image. Then, a visible image of yellow toner is formed by the developing device 4a.

On the other hand, the recording material 9 is conveyed while being electrostatically attracted and held on the conveying belt 8, and the yellow visible image formed on the photosensitive drum 1a by the action of the transfer charger 5a below the photosensitive drum 1a, That is, the toner image is transferred onto the recording material 9. Hereinafter, the second, third and fourth image forming means Pb,
Similar to the first image forming unit Pa, toner images of magenta, cyan, and black are sequentially formed on Pc and Pd, and these toner images are sequentially formed on the recording material 9 conveyed by the conveyor belt 8. It is transcribed multiple times. When the transfer process is completed, the recording material 9 is separated from the recording material conveying section and sent to the fixing device 7, where it is collectively fixed to obtain a desired full-color image. Further, the photosensitive drums 1a to 1d of the respective image forming portions Pa to Pd which have been transferred are prepared for the next latent image formation after the residual toner is removed by the cleaning devices 6a to 6d.

Now, the first separating means from the recording material conveying section will be described in detail. The recording material 9 that has undergone the transfer process as described above moves toward the separating portion S. The separation section S is provided with a separation charger 64 and a separation claw guide 21A as separation means. First, a DC superposed AC high voltage is applied to the separation charger 64. At this time, the drive roller 11 is grounded, and the recording material 9 and the conveyor belt 8 that have reached between the separation charger 64 and the drive roller 11 are simultaneously discharged, and the electrostatic attraction force obtained by the transfer process is removed. .. The recording material 9 deprived of the suction force begins to be separated from the conveyor belt 8, and the separation claw guide 21
It is conveyed to the fixing device 7 along A. At this time, the tip of the separation claw guide 21A is not in contact with the surface of the conveyor belt 8 and the conveyor belt 8 is not scratched.

Next, the second separating means according to the present invention will be described in detail. The conveyor belt 8 is wound around a driving roller 11, a separation roller 11a, a back roller 11b, and a driven roller 12. The curvature of the separation roller 11a is larger than that of the drive roller 11 (about twice in this example). A separation / conveyance path 23 for guiding the recording material 9 separated by the separation roller 11a is provided with the separation roller 11a side as the upstream side. A light emitting portion 24a and a light receiving portion 24b of an optical sensor are provided on the separation / conveyance path 23 as detection means for detecting the recording material 9 entering the conveyance path, with the separation / conveyance path 23 interposed therebetween.

Conventionally, the conveyor belt 8 that has passed through the separating section S
Since the fog toner and the scattered toner adhere to the surface of the paper, it immediately goes to the conveyor belt cleaning device 25 as shown in FIG. According to the present invention, as shown in FIG. 16, after passing through the separation roller 11a having a curvature sufficiently larger than that of the drive roller 11, it reaches the conveyor belt cleaning device 25 through the back roller 11b. With the above configuration, when the separation of the recording material 9 from the conveyor belt 8 occurs in the separating section S, conventionally, the conveyor belt cleaning device 25 is used as it is.
When the cleaning device 25 is reached, the cleaning device 25 is destroyed, or the cleaning device 25 becomes an accordion shape, and the conveyor belt 8 is damaged. In the present invention, when the separation failure occurs in the separation section S, the curvature of the separation roller 11a is sufficiently large, so that the suction force of the transport belt 8 becomes smaller than the bending force of the recording material 9, and the recording material 9 is reliably separated. To do. When the curvature of the driving roller 11 is increased, peeling discharge is generated between the recording material 9 and the conveyor belt 8 to cause image disturbance, which is a problem, but it is not a problem because the recording material is poorly separated. Further, unlike the separating claw which comes into contact with the conveyor belt 8, it does not have to come into contact with the conveyor belt 8 and therefore has an advantage that the conveyor belt 8 can be reliably separated without being damaged. Next, the separation roller 1
The defective recording material 9 having the curvature separated by 1a is guided to the separation conveyance path 23 formed by the guide plate. The light emitting portion 24a and the light receiving portion 24b are provided with detection means for detecting the presence / absence of a pair of recording materials 9 here, and the recording material 9 having a poor separation.
When is reached, the detected signal is displayed on the display means via the control device to notify the user. When a separation failure occurs, the user recognizes the separation failure by the detection means and removes the recording material having the separation failure from the separation conveyance path 23. The image forming apparatus can also start the next image forming operation.

Since the above-mentioned second separating means is provided, the recording material 9 does not reach the conveyor belt cleaning device 25. Therefore, the conventional problem is solved. Further, since the special separating / conveying path is provided, the removing process can be performed without contaminating the other parts of the apparatus.

In the above embodiment, the curvature separating method of the roller having a large curvature is shown as the second separating means. However, as in the case of the first separating means, the electrostatic charge is strongly removed by using the charger, and the second separating means is used. It may be used as a separation means. However, when the curvature separation method is adopted as in this embodiment, there is an advantage that the separation means is inexpensive and has a simple structure. In the above embodiment, the present invention is applied to an electrophotographic color copying machine having four image forming units, but the present invention is applicable to the electrophotographic system having an arbitrary number of image forming units and the electrostatic recording system. Needless to say, it can be applied to various image forming apparatuses including a copying machine and a printer.

[Embodiment 7] This embodiment relates to the reuse of the toner collected in the cleaning device in the multicolor image forming apparatus. FIG. 18 is a sectional view showing an embodiment of the image forming apparatus having a plurality of photoconductors, which is Embodiment 7 to which the present invention is applied. The whole structure is similar to that of the image forming apparatus described above. It is an example of a laser beam printer having an optical scanning means using a plurality of laser beams.
1 shows a laser beam printer with two photosensitive drums.

This printer is provided with four image formations corresponding to colors, each of which has an image forming means around the electrophotographic photosensitive member, and toner on the photosensitive member formed by each image forming section. An image is transferred onto a recording material conveyed by a belt-shaped moving body that moves in opposition to the photoconductor.

Photosensitive drums 1a, 1b, 1c and 1d are arranged in magenta, cyan, yellow and black image forming portions Pa, Pb, Pc and Pd, respectively, and rotated in the arrow direction (clockwise direction). In addition, each photosensitive drum 1a, 1b,
The primary (corona) chargers 2a, 2 are provided around 1c, 1d.
b, 2c, 2d, scanner units 3a, 3b, 3c, 3d as light scanning means, and further developing devices 4a, 4
b, 4c, 4d, and cleaning devices 6a, 6b, 6
An image forming unit having c and 6d is provided.

Further, the transfer section 50 which constitutes one of the image forming means includes a transfer belt 5 and a transfer charger 5a for the photosensitive drums 1a, 1b, 1c and 1d which are commonly used in the respective image forming sections. 5b, 5c, 5d, for forming a full-color image, on the recording material 9 carried on the conveyor belt 8,
This is achieved by sequentially transferring the toner images of the respective colors formed on the photosensitive drums 1a, 1b, 1c, 1d. The recording material 9 is supplied from the paper feed cassette 60, and the recording material 9 that has completed the transfer process is separated, and the fixing device 7
It is discharged to the tray 14 via the.

The scanner units 3a, 3b, 3c,
Reference numeral 3d denotes a laser light source which is a light source (not shown), a rotating polygon mirror for scanning the laser light from the laser light source, an fθ lens for condensing the scanning beam on the generatrix of the photosensitive drum, and a reflecting mirror for deflecting the light beam. And a beam detection device for detecting a specific position of the scanning beam.

Corona chargers 17a, 17b, which control the magnitude of electric charge of the toner while the toner images developed by the developing devices 4a, 4b, 4c, 4d reach the transfer section 50.
17c and 17d are provided.

Next, the present invention will be described in detail with reference to the partial block diagram of the image forming portion Pb (using a cyan developer) of FIG. 19 and the control flow of FIG.

The apparatus for recycling the toner is the same for each image forming section, and FIG. 19 shows the second image forming section P.
In b, the case where cyan toner is used is shown. The cleaning device 6b and the toner hopper 19b communicate with each other through a recycling pipe 26b. A screw 27 for feeding the toner from the cleaning device 6b to the toner hopper 19b is provided in the recycle pipe 26b. The screw 27 has flexibility and rotates by receiving a rotational force from a drive source (not shown). Cleaning device 6 when screw 27 rotates
The residual toner collected in b passes through the recycle pipe 26b and is fed to the toner hopper 19b. The toner in the toner hopper 19b is sent from the toner supply pipe 18b to the developing device 4b by the screw blade 28.

When the image forming apparatus is operated to start the supply operation of the recording material 9, the image forming operation of each image forming section is started in S101. That is, even in the image forming portion Pb using cyan toner, a voltage of -4 to -9 KV is applied to the corona charger 2b and the charging current is -300 to 900 μA, so that the photosensitive drum 1b is uniformly charged. Thereafter, the scanner unit 3b forms a latent image on the photosensitive drum 1b based on an image signal from an image input system (not shown). Next, the toner replenished from the toner hopper 19b through the toner replenishing pipe 18b based on a predetermined signal is mixed and stirred with the developer and developed by the developing device 4b in order to visualize the latent image with a predetermined bias. At this time, the developing method uses reversal development and toner of negative polarity is used. FIG. 21 shows the relationship between the relative humidity and the charge of the toner on the photosensitive drums 1a, 1b, 1c and 1d. From FIG. 21, the photosensitive drums 1a, 1
The charge of the toner developed on b, 1c and 1d has a humidity of 60
% Is about −20 μC / g in each environment. If this toner image is transferred to the recording material 9 as it is, for example, S
When the recording material 9 is conveyed to the image forming portion Pb of the cyan station by the conveying belt 8 in a state where the magenta toner image in the image forming portion Pa is transferred to the recording material 9 at 102, the cyan toner image is transferred next. When a part of the magenta toner on the recording material 9 is retransferred to the photosensitive drum 1b of the image forming portion Pb of the cyan station and is cleaned by the cleaning device 6b of the cyan station, not only the cyan toner but also the magenta toner is transferred to the cleaning device 6b. There is a possibility that it will come in and mix in the recycle pipe 26b.

As a result of a number of experiments, it has been found that color mixture can be prevented by sequentially reducing the charge of the toner in the image forming portion for the second and subsequent colors. It is considered that this is because the latitude of transfer is expanded by lowering the tribo after the second color, and it is difficult to retransfer the toner with high tribo. Therefore, in the present embodiment, a means for sequentially reducing the toner charges on the photosensitive drums 1a, 1b, 1c, 1d of the image forming portions below the first image forming portion Pa is provided, so that the other color toners are provided on each photosensitive drum. To prevent toner re-transfer and enable toner recycling, that is, assuming that the toner charge in the first image forming portion Pa, that is, the magenta color image forming portion Pa is about −20 μC / g, the second image forming portion In Pb, that is, in the cyan image forming portion Pb, in order to reduce the charge of the toner developed on the photosensitive drum 1b, S
At 103, V _PP : 2 is applied to the corona charger 17b as a charge eliminating means.
AC voltage of KV, f _PP : 500 Hz is applied. At this time, the toner charge on the photosensitive drum 1b is about -16 μC / g.
When the transfer efficiency is 80%, the remaining 20% of the toner is cleaned by the cleaning device 6b and returned to the toner hopper 19b through the recycling pipe 26b. At this time, the cyan toner image is transferred to the recording material 9 in S104, and is further conveyed by the conveyor belt 8 to the image forming portion Pc of the third station. Hereinafter, V _PP : 1.5 KV, f _PP : 500 Hz and V _PP : are applied to the corona chargers 17c and 17d in the yellow and black image forming portions Pc and Pd, respectively.
AC voltage of 1 KV, f _PP : 500 Hz is applied (S10
5 to 108) The toner charge on the photosensitive drums 1c and 1d is reduced to about −10 μC / g and about −5 μC / g,
Retransfer is prevented. After the toner charge control and the toner image transfer operation up to S108 are completed in this way, the cleaned toners are returned to the respective color hoppers 19a, 19b, 19c, 19d in S109, and the recording material 9 is discharged after fixing in S110. To be paper.

As described above, means is provided for sequentially reducing the charge of the toner in the downstream image forming section so that the toner on the recording material 9 is not retransferred onto the photosensitive drums 1b, 1c, 1d of the other colors. Thus, the toner can be recycled through the respective cleaning means without color mixing.

[Embodiment 8] In Embodiment 7, the toner charge of each color is controlled in order to recycle the toner of all four colors, but in this embodiment, only the toner of the first image forming portion Pa that does not need to be controlled is controlled. It is characterized in that the black toner is recycled, or the black toner mode is expected to consume the most amount of toner, and the black toner in which mixed colors are less noticeable is controlled to recycle, or only the toner of a specific color is recycled.
Here, when black is in the image forming portion other than the first image forming portion Pa, the toner charge is controlled only for the toner image on the photosensitive drum using the black toner to reduce the toner charge. Is.

[Embodiment 9] In this embodiment, the charge of the toner image on each photosensitive drum used in "Embodiment 7" is controlled to make the retransfer preventing method for the other color photosensitive drums more effective. For this purpose, each transfer charger 5a, 5b, 5 is added as an additional means.
The toners on the recording material 9 are prevented from being retransferred to the photosensitive drums of other colors by increasing the currents applied to c and 5d sequentially and making the transfer electric field stronger toward the downstream image forming portion.

[Embodiment 10] Since the electric charge of the toner fluctuates greatly depending on the ambient temperature and humidity as shown in FIG. 21, a means for detecting the temperature and the humidity is provided in the present embodiment to control the toner charge according to the environmental condition. Corona charger 17a, 17
By controlling the electrification currents applied to b, 17c, and 17d, the toner charge on the photosensitive drum can be stably controlled regardless of the environmental conditions. At this time, the transfer current may be controlled as necessary to make it more effective.

[0105]

As described above, according to the size of the recording material, the position of the separating means is changed or one of the separating means at a plurality of different positions is selectively turned to the recording material carrying means. By advancing forward, it is possible to prevent image disturbance due to the rising of the trailing edge of the recording material due to a shock when the recording material plunges into the fixing means, and separation failure due to dirt on the separating means.

Further, the recording material taken out from the recording material reservoir is transferred to the transfer belt via at least a pair of transfer rollers and then the registration rollers, and further transferred to the transfer portion in the image forming apparatus. By making the distance between the part and the conveying roller located immediately upstream of the registration roller longer than the length of the recording material in the traveling direction,
It is possible to effectively prevent a shock caused by a conveyance roller having a large load on the recording material, and transfer unevenness and image misalignment due to the shock, which is a remarkable effect in obtaining a high quality image.

In addition to the usual first separating means for separating the recording material from the recording material carrying means in the form of an endless belt, the first
Since the second separating means is provided between the separating means and the cleaning device for cleaning the surface of the recording material carrying means to ensure the separation, the second separating means causes the image disturbance and the recording material carrying means. It is possible to prevent the recording material from reaching the cleaning device without causing damage such as scratches. As a result, the recording material does not plunge into the cleaning device to destroy the cleaning device or damage the recording material carrying means.

Further, as the second separating means, by separating the recording material carrying means around the separating roller having a large curvature, the separation due to the large curvature can be carried out. Therefore, an inexpensive, simple and reliable separating device can be provided. I was able to provide it.

Further, since the recording material having the poor separation is guided to the separation conveyance path and detected, it becomes possible for the user to easily detect the separation failure without polluting other parts of the apparatus.

Further, in an image forming apparatus having a plurality of image forming units for forming an image of only one color with one image carrier, by providing means for preventing retransfer of toner of another color to each image carrier, After cleaning, the toner collected in the cleaning device is prevented from being mixed in color, and the toner can be reused after cleaning, which is not only effective in terms of resource reuse for the growing demand for color copying machines, but also In addition, it is also effective as a waste countermeasure against environmental problems in that waste toner is not generated.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part of an image forming apparatus embodying the present invention.

FIG. 2 is a vertical sectional view of an image forming apparatus embodying the present invention.

FIG. 3 is a longitudinal sectional view of a main part of an image forming apparatus according to another embodiment.

FIG. 4 is a vertical sectional view of an image forming apparatus according to another embodiment.

FIG. 5 is a vertical sectional view of an image forming apparatus in a conventional example.

FIG. 6 is a side view showing a problem in the conventional example.

FIG. 7 is a vertical cross-sectional view of an example of an image forming apparatus in which the present invention is implemented on the recording material supply side.

FIG. 8 is a vertical cross-sectional view showing the operation of FIG.

9 is a vertical sectional view showing the operation of FIG.

FIG. 10 is a vertical sectional view showing the operation of FIG.

FIG. 11 is a vertical sectional view showing the operation of FIG.

FIG. 12 is a vertical cross-sectional view of another embodiment of the image forming apparatus in which the present invention is implemented on the recording material supply side.

FIG. 13 is a schematic side view of a main part showing a mode in which the transfer material is conveyed from the registration roller side to the conveyance belt.

FIG. 14 is a schematic side view of a main part showing a mode in which a transfer material is conveyed from a registration roller side to a conveyance belt.

FIG. 15 is a schematic side view of a main part showing a mode in which the transfer material is conveyed from the registration roller side to the conveyance belt.

FIG. 16 is a vertical cross-sectional view showing an embodiment of the present invention in which a means for preventing separation failure in a separation section is applied to an electrophotographic color copying machine.

FIG. 17 is a vertical cross-sectional view of the image forming apparatus in the conventional example with respect to FIG.

FIG. 18 is a vertical sectional view of an image forming apparatus embodying the present invention.

FIG. 19 is a partially enlarged detailed view of FIG. 18.

20 is a flowchart illustrating the operation of FIG.

FIG. 21 is a diagram showing the relationship between environmental humidity and toner charge.

[Explanation of symbols]

 S Separation part Pa, Pb, Pc, Pd Image forming part 7 Fixing device 7a Heating roller 8 Conveying belt 9 Recording material 11 Driving roller 13 Registration roller 18b Toner supply tube 19b Toner hopper 21 Conveying belt 22 Recording material size detecting member 23 Separation and conveying Channel 26b Recycle pipe 27 Screw 29 Adsorption charger 61, 62, 63, 64 Separation charger

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location G03G 15/14 Z 21/00 113 (72) Inventor Yoshinori Mochida 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 Canon Inc. (72) Inventor Ichiro Sekita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (12)

[Claims] 1. A first recording material carrying means for carrying and carrying a recording material, a means for electrostatically adsorbing the recording material on the first recording material carrying means, and a first recording material carrying means. Image forming means for forming an image to be transferred onto the recording material carried on the recording material, separating means for electrostatically separating the recording material from the first recording material carrying means, and a pair of rollers on the recording material. An image forming apparatus comprising: a fixing unit that fixes the formed image on a recording material; and a second recording material holding unit that holds and conveys the recording material that is provided between the separating unit and the fixing unit. An image forming apparatus comprising means for adjusting the position of the fixing means relative to the fixing means. 2. The image forming apparatus according to claim 1, wherein the position of the separating means is adjusted according to the length of the recording material carried on the first recording material carrying means in the moving direction. .. 3. A first recording material carrying means for carrying and transporting the recording material, a means for electrostatically adsorbing the recording material on the first recording material carrying means, and a first recording material carrying means. Image forming means for forming an image to be transferred onto the recording material carried on the recording material, separating means for electrostatically separating the recording material from the first recording material carrying means, and a pair of rollers on the recording material. In an image forming apparatus having a fixing means for fixing the formed image on a recording material and a second recording material carrying means provided between the separating means and the fixing means for carrying and carrying the recording material, the separating means is Each of the plurality of separating means electrostatically separates the recording material from the first recording material holding means, and one of the plurality of separating means selectively advances toward the first recording material holding means. The plurality of separating means have different distances from the fixing means. And an image forming apparatus. 4. At least one image carrier, recording material carrying means for carrying the recording material arranged in the vicinity thereof, and recording arranged near the upstream end of the recording material carrying means in the carrying direction of the recording material. The recording medium is provided in the image forming unit, which has a material suction means, a transfer device for transferring the image on the image carrier to the recording material, and a roller for conveying the recording material which is arranged immediately upstream of the recording material carrying means. In the image forming apparatus in which the conveying force is released immediately before reaching, the distance between the transfer portion and the conveying roller arranged on the upstream side of the recording material conveying roller is set to be larger than the maximum recording material conveying direction length Larger image forming device. 5. The image forming apparatus according to claim 4, wherein the image carrier on the most upstream side in the recording material conveyance direction is also used as the recording material adsorbing means. 6. At least one image forming unit having an image forming unit around an image carrier, and an endless belt-shaped recording material carrying unit that is wound around a plurality of rollers and sequentially conveys the recording material. An image forming apparatus having a first separating means for separating the recording material from the recording material carrying means, and a cleaning device downstream of the first separating means for cleaning the surface of the recording material carrying means. An image forming apparatus having a second separating means between the first separating means and the cleaning device. 7. The separating means having a static eliminating means for applying a high voltage and a claw-shaped separating claw guide, and separating by utilizing the curvature of one of the rollers,
7. The image forming apparatus according to claim 6, wherein the second separating unit is a curvature separating unit formed by a roller having a curvature larger than that of the roller of the first separating unit. 8. A separating / conveying path is provided downstream of the second separating means, and a detecting means for detecting a defective separation recording material separated by the second separating means is provided in the conveying path. The image forming apparatus according to claim 6. 9. An image forming member for forming an image on an image carrier,
An image forming apparatus having a plurality of image forming units each including a latent image forming unit, a developing device, and a cleaning device, and a transfer unit that superimposes toner images of different colors formed by the respective image forming units onto a recording material. In the image forming apparatus, the control device for preventing color mixture of toner captured by the cleaning device is reused, and the toner of the cleaning device by the cleaning device is reused. 10. The image forming apparatus according to claim 9, wherein the control unit for preventing color mixture of the toner conveyed by the cleaning device is a control unit for preventing retransfer of the toner onto the image carrier. apparatus. 11. The control device for preventing color mixture of toner captured by the cleaning device is a device for controlling the charge of the toner on the image carrier and before the toner image on the image carrier enters the transfer device. The image forming apparatus according to claim 9, wherein the image forming apparatus is located. 12. The control means for preventing retransfer of toner onto the image bearing member includes means for strengthening a transfer electric field for each image forming portion toward a downstream image forming portion. The image forming apparatus according to item 10.