JPH0387874A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a high quality picture without a jam and transfer omission by providing a transfer material carrying guide between the transfer material supplying position on a transfer material carrying member and the transfer position, and securely carrying a transfer material to the transfer position by means of the transfer material carrying guide. CONSTITUTION:After the transfer material P is supplied to the transfer material supplying position, where a conductive roller 20 is located, it is electrostatically attracted and held onto the transfer material carrying sheet 6a by a corona electrifier 19, and is sent to the transfer position where a transfer electrifier 7 facing a photosensitive drum 1 is located. The transfer material carrying guide 223 is provided so as to be positioned between the transfer material supplying position and the transfer position. Even when the transfer material P is not attracted and not held onto the transfer material carrying sheet 6a, and consequently the front edge of the transfer material P hangs down in the gravitational direction, the material P is guided by the guide 223 to be delivered to the transfer position without causing a jam. In the transfer position, the transfer corona electrifier 7 operates to generate a transfer electric field, and a toner image on the drum 1 is subjected to transfer P by means of charges imparted to the transfer material carrying sheet 6a.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and particularly relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus. The present invention relates to an image forming apparatus that transfers images onto a transfer material held above.

For example, in a color electrophotographic copying machine, an image is obtained by forming a toner image on an image bearing member such as a photosensitive drum and transferring the toner image to a transfer material. Usually, the transfer material is carried and conveyed by a transfer drum, which is constructed by wrapping a transfer material carrying member, usually a transfer material carrying sheet such as a high resistance film, around a drum-shaped frame. That is, at the transfer material supply position, the transfer material supplied to the transfer drum is mechanically fixed and held at its tip by a gripper provided on a part of the circumferential surface of the transfer drum, or is held by electrostatic adsorption. It is wrapped around a transfer material carrying sheet by holding it firmly with force (Japanese Patent Laid-Open No. 55
-32079). Then, by rotating the transfer drum, the transfer material is transferred to the transfer position multiple times,
By multiple transfer, toner images of multiple colors are transferred from the image carrier to the surface of the transfer material.

However, in the conventional method described above, when the transfer material is held on the transfer material carrying sheet, a gap may locally occur between the transfer material and the transfer material carrying sheet. The reason why such a gap occurs is that, for example, the transfer material carrying sheet is mechanically deformed by a cleaning member provided to clean and remove residual toner on the transfer material carrying sheet, or
Alternatively, it may be caused by deformation due to the influence of electrostatic force due to charging of the transfer material carrying sheet, or due to the influence of heat from a fixing device disposed close to the transfer drum. . In particular, when a corona charger is used as a transfer charger, charges are applied to the transfer material and the transfer material supporting sheet over a relatively wide range.
The deformation area of the transfer material carrying sheet expands.

As described above, at locations where a gap is created between the transfer material and the transfer material carrying sheet, the transfer efficiency decreases and transfer omissions occur.

Furthermore, if the transfer material holding surface of the transfer material carrying sheet is deformed into a convex shape, so-called "jamming" is likely to occur, and conversely, if the transfer material holding surface is deformed into a concave shape, poor suction of the transfer material will occur. However, problems such as misalignment occur during transfer.

In particular, the above problem is noticeable when the transfer material is held on the transfer material carrying sheet by electrostatic attraction without using a gripper.

For this purpose, in conventional image forming apparatuses that electrostatically transfer the toner image on an image carrier to a transfer material held on a transfer material carrying sheet to form an image on the transfer material, the transfer material carrying sheet A charge applying means that contacts the transfer material carrying sheet and a charge injection means that contacts the transfer material on the holding surface of the transfer material carrying sheet are arranged to face each other with the charge applying means and the charge injection means A pressure mechanism is provided on at least one side to forcibly remove a gap between the transfer material carrying sheet and the transfer material when the transfer material is attracted to the transfer material carrying sheet.

However, in the conventional method described above, changes in temperature and humidity,
Due to changes in the paper thickness of the transfer material P, changes in the feeding speed of the transfer material, and changes in the charges of the charge applying means and the charge injection means, the installation position of the charge applying means and the charge injection means (i.e., the transfer material supply position) and the transfer position may change. In many cases, the transfer material becomes incompletely adsorbed to the transfer material carrying sheet between the two, or the transfer material completely peels off from the transfer material carrying sheet, resulting in a jam. Incomplete suction state means that there is a local gap between the transfer material and the transfer material carrying sheet. If the transfer material passes the transfer position in this state, it may cause transfer failure or misalignment of the image. , or wrinkles or the like may occur on the transfer material. In particular, the above-mentioned problems are noticeable with transfer materials having a curvature in the opposite direction to the curvature of the transfer material carrying sheet, such as so-called curled paper.

Therefore, an object of the present invention is to prevent transfer failure even when incomplete adsorption of the transfer material occurs between the adsorption position and the transfer position in a transfer material carrying member such as a transfer material carrying sheet that supports and conveys the transfer material. You can obtain high-quality images without
Another object of the present invention is to provide an image forming apparatus that can significantly improve color reproducibility in color image formation.

in order to The above object is achieved by an image forming apparatus according to the present invention.

To summarize, the present invention provides an image forming apparatus that forms an image on an image carrier and transfers the image to a transfer material held on a transfer material carrying member, in which a transfer material supply means of the transfer material carrying member is provided. An image forming apparatus characterized in that a transfer material conveyance guide is provided between a transfer material supply position where the transfer material is supplied from the image carrier and a transfer position where the image on the image carrier is transferred to the transfer material. It is.

According to a preferred embodiment, the charge injection means is provided at the transfer material supply position, facing the transfer material and movable toward and away from the transfer material carrying member, and the transfer material conveyance guide is provided with the charge injection means. The transfer material carrying member is configured to move toward and away from the transfer material carrying member in conjunction with or independently from the movement toward and away from the transfer material carrying member. Note that the transfer material conveyance guide may be configured to come into contact with the transfer material carrying member when it approaches the transfer material carrying member, or may be positioned close to the transfer material carrying member with a slight gap therebetween.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The image forming apparatus according to the present invention will be specifically described below with reference to the drawings.

In FIG. 1, a photosensitive drum 1, which is an image carrier, is rotationally driven in the direction of the arrow. A primary charger 2, an optical system 3, a developing device 4, and a pre-transfer charger 5 are arranged facing the outer peripheral surface of the photosensitive drum 1 in the rotation direction thereof. - The charger 2 applies a uniform charge amount to the photosensitive drum 1, and the optical system 3 applies a color-separated optical image or a light beam corresponding to this to the surface of the photosensitive drum 1 at a predetermined timing, and Form a latent image. This optical system 3 uses a laser beam scanning device or the like. Further, in this embodiment, the developing device 4 is a horizontally moving type developing device that moves in a tangential direction facing the surface of the photosensitive drum 1, and is capable of processing magenta color developer, cyan color developer, yellow color developer, and black color developer. It is equipped with four developing devices 4M, 4C14Y, and 4BK that separately store developer toner of four colors. The developing device 4 makes a selected developing device face the photosensitive drum 1 in response to irradiation of a light image of a selected color by the optical system 3 or a light beam corresponding thereto, and forms a toner image on the surface of the photosensitive drum 1. form.

Furthermore, a transfer device 6 is arranged opposite to the photosensitive drum 1. As schematically illustrated in FIG. 2, the transfer device 6 is a transfer drum in which a transfer material carrying member, that is, a transfer material carrying sheet 6a is wound in a cylindrical shape between both cylindrical end frames 6b. Further, as shown in FIG. 1, at the transfer position facing the photosensitive drum 1, a transfer corona charger 7 is provided on the opposite side of the holding surface of the transfer material carrying sheet 6a, that is, inside the transfer drum 6.
will be placed.

The transfer drum 6 is driven to rotate in the direction of the arrow, and the transfer drum 6 is placed on the upstream side of the transfer position where the corona charger 7 is disposed, on the opposite side of the transfer material holding surface of the transfer material carrying sheet 6a.
An adsorption corona charger 19 is disposed inside the transfer material holding surface, and a conductive roller 20 as a charge injection means is disposed facing the transfer material holding surface.

Further, on the downstream side of the transfer position, a corona discharger 10.11 for static elimination is arranged across the transfer material carrying sheet 6a, and also disposes the transfer material P held on the transfer material carrying sheet 6a. Pressing rollers 12 and 13 for separating from the transfer material carrying sheet 6a are disposed with the transfer material carrying sheet 6a in between, and a separating blade 14 is disposed in the vicinity thereof. Furthermore, on the downstream side, there is a brush roller 15 for cleaning the holding surface of the transfer material carrying sheet 6a, and a corona discharger or brush type remover for removing adhesion forces (residual Coulomb force and van der Waals force) as necessary. Electric appliances 1
6 is provided.

Further, a fixing device 18 consisting of a pair of fixing rollers is arranged adjacent to the transfer drum 6, and the toner on the transfer material P separated from the transfer material carrying sheet 6a by the separating blade 14 and transported by the conveyor 17 is separated from the transfer material carrying sheet 6a by the separating blade 14. Fix the image.

Further, around the photosensitive drum 1, as shown in FIG. 1, a static eliminator 27 for removing static charge on the surface of the photosensitive drum 1 and a cleaning blade 28 for removing residual toner are provided. In addition, if necessary, near the separation blade 14,
In order to prevent image disturbance due to peeling discharge that occurs when the transfer material P is separated from the transfer material carrying sheet 6a, it is preferable to install a corona discharger 29 and perform AC corona discharge.

With this configuration, the surface of the photosensitive drum 1 is uniformly charged by the primary charger 2, and then, when a color image is irradiated by the optical system 3 through, for example, a green filter, the magenta component of the color image is A latent image is formed that mainly consists of . In synchronization with the feeding of this latent image, the developing device 4
A developing device 4M containing magenta developer is moved tangentially to the photosensitive drum 1 to face the photosensitive drum 1, and a magenta toner image is formed on the photosensitive drum 1.

On the other hand, the transfer material P is introduced into the upper guide 22 and the lower guide 22' by the action of the registration rollers 21 and 21', and guided by the upper and lower guides, the transfer material P is rolled along the surface of the transfer material carrying sheet 6a. The transfer material is supplied to the transfer material supply position where the transfer material 20 is located.

According to the present invention, the lower guide 22' is swingably supported about a fulcrum A, and is normally biased clockwise in FIG. 1 by a coil spring 222. Further, the conductive roller 20 is rotatably attached to the tip of the lower guide 22', and therefore the conductive roller 20 is an eccentric cam that is rotationally driven in the direction of the arrow by a driving means (not shown). When the lower guide 22' swings around the fulcrum A by 221, it moves towards and away from the transfer material carrying sheet 6a. The eccentric cam 221 is driven in synchronization with the supply timing of the transfer material P, and when the transfer material P is supplied to the supply position, the conductive roller 20 moves the transfer material carrying sheet as shown in FIG. 6a.

In this embodiment, the transfer material P is transferred to the transfer material carrying sheet 6a.
At the position where the transfer material carrying sheet 6a is supplied, a strain correcting means 23 made of an elastic support member such as a 150 μm elastic sheet is provided on the opposite surface of the holding surface of the transfer material carrying sheet 6a to press and hold the transfer material carrying sheet 6a from the inside. The mechanical deformation and formation of the transfer material carrying sheet 6a by the brush roller 15 or the like corrects or prevents the deformation caused by the electrostatic force by the corona charger 19.

In this case, the elastic force of the distortion correction means 23 is
It is preferable to act in the direction in which the transfer material carrying sheet 6a is stretched, that is, in the opposite direction to the moving direction of the transfer material carrying sheet, thereby reducing the distortion of the transfer material carrying sheet 6a in the thrust direction (the axial direction of the transfer drum). be able to. Further, it is also possible to regulate the circumferential discharge distribution of the corona charger 19.

In the above configuration, after the transfer material P is supplied to the transfer material supply position where the conductive roller 20 is located, the corona charger 19
The transfer material is electrostatically attracted and held by the transfer material carrying sheet 6a and sent to the transfer position where the transfer charger 7 is located, facing the photosensitive drum 1. Of course, the timing at which the registration rollers 21, 21' feed the transfer material and the timing at which the optical system 3 forms a latent image are synchronized and coincide at the transfer position.

According to the present invention, the transfer material conveyance guide 223 is provided so as to be located between the transfer material supply position and the transfer position. In this embodiment, the transfer material conveyance guide 223 is integrally formed with the lower guide 22'. Therefore, due to changes in the environment, changes in the paper thickness of the transfer material P, etc., the transfer material P is not adsorbed and held by the transfer material carrying sheet 6a, and the transfer material P
Even if a state occurs in which the leading edge of the transfer material P hangs down in the direction of gravity, the transfer material P is guided by the transfer material conveyance guide 223 and is transported to the transfer position without becoming jammed.

The transfer material conveyance guide 223 has a fulcrum A like the lower guide.
When the conductive roller 20 is in contact with the surface of the transfer material carrying sheet 6a, the transfer material carrying sheet 6a
Therefore, they are positioned so as to be separated by a gap d that is somewhat larger than the thickness of the transfer material P.

At the transfer position, a corona charger 7 for transfer operates to generate a transfer electric field, and the toner image on the photosensitive drum 1 is transferred onto the transfer material P by the charge applied to the transfer material carrying sheet 6a.

Further, according to this embodiment, as shown in FIG. 3, the eccentric cam 221 is rotated to the bottom dead center by the driving means at the timing when the rear end of the transfer material P passes the conductive roller 20. Driven. As a result, the lower guide 22' is urged and rotated counterclockwise about the fulcrum A, and as a result, the conductive roller 20 and the transfer material conveying guide 223 are largely retracted from the transfer material carrying sheet 6a. As a result, dirt such as toner adhering to the transfer material carrying sheet is removed from the conductive roller 2.
As a result, staining of the transfer material P can be prevented.

Toner remaining on the photosensitive drum 1 after transfer is removed by a static eliminator 2.
After the static electricity is removed in step 7, it is removed by a blade 28, and the surface of the photosensitive drum 1 is cleaned. On the other hand, the transfer material P attracted to the transfer material carrying sheet 6a moves as the transfer drum 6 rotates while carrying the toner image, and passes between the corona dischargers 10 and 11. At this time, corona discharger 10.11 is not energized. Also, pressing roller 1
2.13 is also separated from the transfer material carrying sheet) 6a, and includes a brush roller 15, a brush type static eliminator 16, and a conductive roller 20.
It is also separated from the transfer material carrying sheet 6a. In this way, the transfer material P, in which the toner image carried by the Coulomb force is transported without being disturbed, further passes between the corona charger 19 and the conductive roller 20 and is sent to the transfer position again. .

Note that the biasing of the corona charger 19 and the contact of the conductive roller 20 with the transfer material carrying sheet 6a are completed before the leading edge of the toner image on the transfer material P reaches the positions of the corona charger 19 and the conductive roller 20. When the transfer material P passes through this gap, no charge for adsorption is applied to the transfer material P.

The above image formation and transfer operation can be performed using other cyan, yellow,
The process is also carried out for black color, and a full color image is formed on the transfer material P. After that, the charger 10, 11, 29 and the separating means 12, 13, 14 are operated, and the transfer material P is separated from the transfer drum 6 and transferred to the fixing device. transported to.

FIG. 4 shows another embodiment of the image forming apparatus according to the present invention.

The embodiment of FIG. 4 differs from the embodiment of FIG. 1 in the following points.

In other words, in this embodiment, the transfer material conveying guide 223, which is formed integrally with the lower guide 22', has its tip 223a touching the transfer material when the conductive roller 2o is in contact with the surface of the transfer material carrying sheet 6a. It is configured to be in contact with the carrier sheet 6a.

Therefore, in this embodiment, in order for the substantially leading end 223a of the transfer material conveying guide 223 to slide with the transfer material carrying sheet 6a, it is desirable that the leading end 223a be formed of, for example, an elastic sheet with a thickness of 150 μm. .

As described above, according to this embodiment, since the transfer material carrying sheet 6a and the transfer material conveying guide 223 are in contact with each other,
Even if the transfer material P is incompletely adsorbed to the transfer material carrying sheet 6a at the position of the conductive roller 20, that is, at the transfer material supply position, due to environmental changes, changes in the state of the transfer material, etc., the transfer material P cannot be removed. Approximately the tip 22 of the transfer material conveyance guide 223
The transfer material can be reliably adsorbed to the surface of the transfer material carrying sheet 6a at position 3a.

FIG. 5 shows yet another embodiment. The embodiment shown in FIG.
In the illustrated embodiment, the transfer material conveyance guide 223 is lower than the lower guide 2.
It is different from 2' in that it is provided independently.

In the embodiment shown in FIG. 5, the transfer material P is the conductive roller 2.
At the 0 position, the transfer material is attracted to the transfer material carrying sheet 6a, and then sent to the position of the transfer material conveyance guide 223. The transfer material conveyance guide 223 is fixed to an arm 25 that is pivotally supported on the frame 26 by a pin 26a. The arm 25 is normally supported by a tension spring 30 so as to be separated from the transfer material carrying sheet 6a, and the transfer material conveyance guide 223 is supported by an electromagnetic solenoid 31 connected to the arm 25.
By urging the arm 25 and swinging the arm 25 against the elastic force of the tension spring 30, the arm 25 is brought into contact with the transfer material carrying sheet 6a.

According to this embodiment, with the above-described configuration, the transfer material P
When the transfer material conveyance guide 223 passes through the position of the transfer material conveyance guide 8223, the transfer material conveyance guide 223 is brought into contact with the transfer material carrying sheet 6a, and is otherwise retracted to a position where it does not come into contact with the transfer material carrying sheet 6a.

Therefore, between the position of the conductor roller 20 and the transfer position, the transfer material P can be reliably attracted to the transfer material carrying sheet 6a by the transfer material conveyance guide 223, and the toner etc. on the transfer material carrying sheet can be This prevents the reading from being transferred to the transfer material conveyance guide 223 and contaminating the transfer material as a result.

As explained above, in the image forming apparatus according to the present invention, since the transfer material conveyance guide is provided between the transfer material supply position and the transfer position in the transfer material carrying member, the transfer material cannot be easily transferred. Even if incomplete adsorption to the material carrying member occurs, or even if the transfer material is completely peeled off from the transfer material carrying member and is likely to jam, the transfer material is reliably transported to the transfer position by the transfer material conveyance guide. It has the advantage of being able to obtain high-quality images without jams or transfer omissions, and furthermore, in the case of color image formation, color reproducibility can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a perspective view of one embodiment of the transfer device. FIG. 3 is a schematic cross-sectional view of the structure of the image forming apparatus shown in FIG. 1, showing a mode in which the transfer material conveyance guide is spaced apart from the transfer material carrying sheet. 4 and 5 are schematic cross-sectional views of other embodiments of the image forming apparatus according to the present invention. 1: Image carrier 6: Transfer device 7: Transfer charger 20: Charge injection means (conductive roller) 22.22' guide 221: Eccentric cam 223: Transfer material conveyance guide

Claims (1)

[Scope of Claims] 1) In an image forming apparatus that forms an image on an image carrier and transfers the image to a transfer material held on a transfer material carrying member, the transfer material supply of the transfer material carrying member Image formation characterized in that a transfer material conveyance guide is provided between a transfer material supply position where the transfer material is supplied from the means and a transfer position where the image on the image carrier is transferred to the transfer material. Device. 2) A charge injection means is provided opposite to the transfer material at the transfer material supply position and is movable toward and away from the transfer material carrying member, and the transfer material conveyance guide is configured to move the charge injection means toward and away from the transfer material carrying member. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus moves toward and away from the transfer material carrying member in conjunction with the movement. 3) A charge injection means is provided at the transfer material supply position, facing the transfer material and movable toward and away from the transfer material carrying member, and the transfer material conveyance guide means is configured to move the charge injection means away from the transfer material carrying member. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus moves toward and away from the transfer material carrying member independently of the tangential movement.