JPS62127770A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain high-quality images which are free from insufficient density parts, by pressing and closely contacting a transfer material against and with an image carrier having a visual image just before the transfer material reaches a transferring position. CONSTITUTION:A pressing means 20 which presses a carrying belt 8 and transfer material 6 against photosensitive drums 1a, 1b, 1c, and 1d at transferring positions of each image formation Pa, Pb, Pc, and Pd is provided. The pressing means 20 is provided below the carrying belt 8 and, when the means 20 does not press the belt 8, a pressing section 21 comes down to the position shown by the dotted line and the belt 8 and transfer material 6 are not allowed to contact with the photosensitive drum 1a. When an image formation starting switch is depressed, the transfer material 6 is attracted to the surface of the belt 8, and thus, the transportation of the material 6 is started. At this time, a shaft 22 is rotated or a discharge 4a for transfer is raised and the pressing section 21 pushes the carrying belt 8 toward the photosensitive drum 1a before the transfer material 6 reaches the transferring position.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises one image forming unit having an image bearing member and a developing device and forming an image of at least one color, and in the image forming unit Visible image formed (toner image)
An image forming bag that transfers images onto a transfer material, or has a plurality of such image forming units, each image forming unit forming a visible image (toner image) of a different color. The present invention relates to an image forming apparatus that sequentially transfers toner images onto the same transfer material, and is particularly characterized by a transfer means that transfers toner images onto the transfer material.

Conventionally, a plurality of image forming units are provided, and each image forming unit forms a visible image (toner image) of a different color, and the toner images are sequentially transferred onto the same transfer material in an overlapping manner. A variety of image forming apparatuses, so-called color image forming apparatuses, have been proposed, but the most commonly used color copying apparatus is a multicolor electrophotographic color copying apparatus.An example of such a color copying apparatus is shown in FIG. A simple explanation will be given based on this.

In Fig. 4, there is a first
, second, third, and fourth image forming units Pa, Pb,
Pc and Pd are arranged in parallel. The first, second, third and fourth image forming units Pa, Pb, Pc and Pd each have a dedicated image carrier, in this example an electrophotographic photosensitive drum la,
It is equipped with lb, lc and 1d.

The photosensitive drums 1a, 1b, 1c, and ld have latent image forming sections 2a, 2b, 2C12d, and developing sections 3a, 3 on their outer peripheral sides.
b, 3C13d, transfer discharge parts 4a, 4b, 4c, 4d
And cleaning sections 5a, 5b, and 5C15d are arranged. With such a configuration, in the color copying apparatus, the first
A latent image of the yellow component color in the original image is formed on the photosensitive drum la of the PIj image forming unit Pa at a latent image forming pH of 2a. The latent image is made into a visible image by a developer containing yellow toner in the developing section 3a, and the yellow toner image is transferred onto the transfer material 6 at the transfer section 4a.

On the other hand, while the yellow image is being transferred to the transfer material as described above, a latent image of magenta component color is formed in the second image forming unit (Pb), and then a toner image with magenta toner is obtained in the developing section 3b. It will be done. The magenta toner image is
When the transfer material 6 that has been transferred in the first image forming unit Pa is carried into the transfer 4b, the image is transferred to a predetermined position on the transfer material 6.

Hereinafter, the third step will be carried out in the same manner as above. Cyan and black images are formed by the fourth image type (t unit) Pc and Pd, and the cyan and black colors are transferred to predetermined positions on the same transfer material. When such image formation is completed, the image on the transfer material is fixed to the transfer material by the fixing section 7 to form a multicolor image 111. On the other hand, each of the photosensitive drums la, lb, lc, and ld on which the transfer has been completed is cleaned by a cleaning section 5a.
, 5b, and 5C15d, the residual toner is removed and prepared for the next latent image formation to be performed subsequently.

In the image forming apparatus having the above configuration, the transfer material 6 is conveyed by the conveyor belt 8 from the right side to the left side in FIG.
, Pdc7) is configured to pass through the transfer sections 4a, 4b, and 4C14d.

However, in the image forming apparatus with the above configuration, the conveyor belt and the photosensitive drum are in line contact, so the adhesion between the transfer material and the photosensitive drum is poor, and therefore the toner image is not formed on the transfer material. In order to improve the transferability, the transfer number sections 4a, 4b, 4c,
It is necessary to strengthen the transfer corona in 4d. For this reason, conventionally, there have been problems in that the conveyor belt is highly charged, resulting in an increase in transfer dust, and the photosensitive drum is unnecessarily charged, accelerating deterioration of the photosensitive drum l. On the other hand, if the transfer corona is weak, there is a problem that uneven transfer is likely to occur due to vibrations of the conveyor belt, unevenness of the surface of the conveyor belt, etc.

Further, in image formation other than full-color image formation, for example, in the case of a two-color original of black toner and red toner, development and transfer in the cyan image forming unit are unnecessary. However, in conventional image forming apparatuses, even in this case, the transfer material passing through the cyan image forming unit is brought into contact with the photosensitive drum of the image forming unit, and minute amounts of cyan toner adhering to the photosensitive drum are transferred. As a result, there was a problem in that image deterioration occurred.

Such toner adhesion of unnecessary colors occurs to some extent even when there is no image signal, and becomes particularly noticeable due to fluctuations in the position of the photosensitive drum. In addition, it tends to occur before and after the rotation of the developing sleeve of each developing section starts, and after the surface to which the phenomenon bias voltage is applied.

Conventionally, as a countermeasure to this problem, a method of not applying voltage to the transfer discharge wire when transfer is not required has been considered, but as long as the transfer material is in contact with the photosensitive drum, unnecessary toner adhesion is prevented. The current situation is that this is not possible.

9. The first goal of this project is to solve the above problems by improving some of the conventional components to achieve stable transferability without installing complicated and expensive mechanisms. An object of the present invention is to provide an image forming apparatus capable of obtaining images of good quality.

Another object of the present invention is to provide an image forming apparatus in which deterioration of an image bearing member such as a photosensitive drum is reduced.

Ha! 11. Objective I) above is achieved by the image forming apparatus according to the present invention. To summarize, the present invention forms a latent image in an image forming unit having an image carrier, and transfers the visible image obtained by developing the PPi image onto a transfer material conveyed by a conveyance stage. In the image forming apparatus, +ii
Immediately before the transfer material reaches the transfer position, the transfer material acting on the transport stage i is pressed into close contact with the image bearing member having the visible image, and the transfer material is pressed against the image carrier having the visible image. The image forming apparatus is characterized in that it has a pressing means for acting on the transfer material conveying means to separate the transfer material from the image carrier when it passes a transfer position.

The present invention will be explained below with reference to FIGS. 1 to 3 showing one embodiment thereof.

In this embodiment, the image forming apparatus according to the present invention is embodied in the color electrophotographic apparatus shown in FIG. 4, and the overall structure thereof is the same. That is, in the image forming apparatus according to the present invention, referring to FIG.
2, and a conveyor belt 8 is stretched around the drive roller 12 and rotated in the direction of the arrow.

The conveyor belt 8 is formed of a thin dielectric sheet using a mesh of Tetoron fibers with little elongation, and is formed to electrostatically attract the transfer material 6 to the surface and to prevent lateral displacement or meandering when rotating. . Alternatively, the conveyor belt 8 may be formed of a thin dielectric film made of conductive synthetic resin. In either case, the conveyor belt 8
The surface of the transfer material 6 is made free from irregularities that would cause uneven transfer.

In FIG. 1, a paper feed mechanism 13 is arranged on the right side of the conveyor belt 8, and the transfer material 6 is fed onto the conveyor belt 8 via the paper feed mechanism 13. Each image forming unit Pa, Pb,
The transfer material 6 that has been transferred at Pc and Pd is transferred to the conveyor belt 8.
is sent to the fixing device 7 from the left side. The fixed transfer material 6 is discharged from the discharge port 14 to the outside of the apparatus main body 10.

Above the conveyor belt 8, there are first and second
．． Third and fourth image forming units Pa, Pb, Pc, and Pd are arranged in parallel. 1st. The second, :53 and fourth image forming units Pa, Pb, Pc and Pd are photosensitive drums la.
, 1b, lc, and 1d, and the photosensitive drums 1a, 1
b, charger 15 on the upper left side of each IC1 and ld
a, 15b, 15c and 15d are provided.

Further, laser beams 16a, 16b, 16c, and 16d are provided in two parts of the photosensitive drums la, lb, lc, and ld, respectively. These laser beam scanners 16a
, 16b, 16c, 16d are composed of semiconductor lasers, polygon mirrors, fO lenses, etc., and receive the electric digital image signal and emit a laser beam modulated in accordance with the signal to the band 1 [devices 15a, 15b, 15c, 15d and the developing devices 3a, 3b, 3c, and 3d.
It is formed to scan in the direction of the I line of b, lc, and ld to expose these.

Specifically, the laser scanner 16a of the first image forming unit Pa receives a pixel signal corresponding to the yellow component image of the color image, and the laser scanner 16b of the second image forming unit Pb receives a pixel signal corresponding to the magenta component image. are input completely, and the third image forming unit Pa
laser scanner 16c and fourth image forming unit Pd
An image signal corresponding to a cyan component image and a pixel signal corresponding to a black component image are respectively input to the laser scanner 16d.

The paper feeding mechanism 13 includes a paper feeding kite 51 and a sensor 52. When the transfer material 6 is inserted into the paper feeding guide 51, the sensor 52 detects the tip of the transfer material 6, and the photosensitive tram la, lb
, lc, and 1d, and the drive roller 12 is also driven to rotate the conveyance heald 8. Further, the transfer material 6 fed to the conveyor belt 8 receives corona discharge from the attraction charger 59 and is reliably attracted to the surface of the conveyor belt 8.

The leading edge of the transfer paper 6 is connected to each sensor 60a, 60b, 60c,
When 60d is shut off, image formation on the rotating photosensitive trams la, lb, lc, and 1d is sequentially started based on the signal. When the transfer material 6 passes through the fourth image forming unit Pd, the static eliminator 61 to which an AC voltage is applied removes the transfer material 6.
is neutralized and separated from the conveyor belt 8.

Next, the transfer material 6 enters the fixing 7 and after fixing the image,
It is discharged from "Discharge 1" 14.

Furthermore, according to the present invention, the conveyor belt 8 and the transfer material 6 are
Press stage 2 that presses against the photosensitive drums la, 1b, 1c, and ■d at the transfer positions of each image forming Pa, Pb, Pc, and Pd.
0 is set.

Hereinafter, with reference to FIG. 2, the pressing means 20 installed in the image forming unit Pa will be described as an example. Pressing means 2
0 includes a pressing part 21 having elasticity and a shaft 22 to which one end of the pressing part 21 is bonded. The pressing portion 21 can be made of an insulating sheet, such as polyethylene tereftate reprinted as Mylar (registered trademark), and preferably has a thickness of about 100 mm.

The shaft 22 is mounted on the main body 10 so as to be rotatable in the direction of the arrow, and its rotational movement is performed by driving means such as a solenoid and a spring. Further, in this embodiment, the pressing means 20 is provided below the conveyor belt 8, and when the conveyor belt 8 is not pressed, the pressing portion 21 of the presser is lowered to the position shown by the dotted line, and the conveyor belt 8 is lowered. and the transfer material 6 is a photosensitive drum l
It is configured so as not to come into contact with a.

Further, the contact position between the pressing stage 20 and the conveyor belt 8 is located behind the tangential position 23 between the photosensitive drum la and the conveyor belt 8, and the distance thereof is approximately 3 mm.

Further, the pressing force of the pressing means 2o is approximately 12 g/cm. On the other hand, the transfer discharge device 4a consists of a discharge wire 24 and a pack plate 25, and discharge is turned ON10F at a predetermined transfer timing from a constant voltage power source.
F is given.

The pressing means 20 may be configured as shown in FIG. This pressing means (unit) 26 is
By moving the transfer discharger 4a up and down, the conveyor belt 8 is pressed and released. The pressing position of the conveyor belt 8 is set by driving means (not shown) such as a vertically movable solenoid and a spring in the same manner as the pressing means 2o described above.

Moreover, this pressing means 26 is easy to remove, and by removing it, the transfer discharge wire 24 and the pack plate 2 are removed.
The feature is that not only the pressing part 5 but also the pressing part 21 can be easily cleaned.

The operation of the pressing means 20 and 26 having the following structure will be explained below. When the switch for starting image formation is pressed, the transfer material 6 is attracted to the surface of the conveyor belt 8 and conveyance is started. At this time, the shaft 21 rotates in accordance with a predetermined timing or the transfer discharger 4a rises, and before the transfer material 6 reaches the transfer position, the pressing section 21 moves the conveyor belt 8 toward the photosensitive drum la. and press.

As mentioned above, depending on the type of document, it may not be necessary to perform development and transfer in all image forming units, but in this case, the transfer material 6 is transported to the transfer position of the image forming unit. However, the pressing portion 21 does not press the conveyor belt 8 toward the photosensitive drum. Furthermore, since no voltage is applied to the transfer discharge wire 24, the transfer process is omitted.

Therefore, the transfer material 6 attracted to the conveyor belt 8 does not come into close contact with the photosensitive drum, the unfixed toner image already transferred onto the transfer material 6 is not disturbed, and unnecessary color toner is also transferred. There isn't.

Incidentally, in the embodiment L, a digital color image forming apparatus equipped with four photosensitive drums has been described, but the present invention is not limited thereto. It is also suitable for forming devices. Further, although the color copying apparatus has been described as an example, the present invention is not limited to this and can be applied to various image forming apparatuses.

The image forming apparatus according to the present invention configured as shown in Section A and II can completely prevent unnecessary toner from adhering to the transfer material, and can completely avoid image quality deterioration. Therefore, such a prevention means is not a complicated and expensive mechanism, but can be simply attached to the conventional 4R components.

Price increases can be prevented and the reliability of one image forming apparatus can also be improved.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of the pressing means. FIG. 2 is a schematic explanatory diagram of the overall structure of an embodiment of the image forming apparatus according to Misaki II. FIG. 3 is a side sectional view of a modification of the pressing means. FIG. 4 is a schematic illustration of a conventional image forming bag. Pa, Pb, Pc, Pd: Image forming units la, lb
, lc, ld: Image carrier 6: Transfer material 8: Conveyor belt 20.26: Pressing stage 21: Pressing department agent Patent attorney Akira Kurahashi)7. Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] 1) A latent image is formed in an image forming unit having an image carrier, and a visible image obtained by developing the latent image is transferred to a transfer material conveyed by a conveying means. In an image forming apparatus configured to perform transfer, the image forming apparatus acts on the conveyance means to press the transfer material conveyed by the conveyance means into close contact with the image carrier having the visible image immediately before the transfer material reaches the transfer position. ,
The image forming apparatus further comprises a pressing means for acting on the transfer material conveying means to separate the transfer material from the image carrier when the transfer material passes through the transfer position. 2) A plurality of image forming units are arranged in parallel, and the transfer material conveyance means is a conveyance belt arranged so as to sequentially apply the transfer material to the plurality of image forming units. Device. 3) The conveyor belt is formed of a mesh-like thin dielectric material that electrostatically attracts and conveys the transfer material.
Apparatus described in section. 4) A claim in which the pressing means comprises an elastic insulating sheet that urges the transfer material conveying means toward the image carrier, and an actuating means that drives the sheet toward and away from the transfer material conveying means. The device according to any one of paragraphs 1 to 3.