JPH0697364B2 - Multiple image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention has a plurality of developing devices, develops a latent image formed on an image carrier that moves endlessly, and transfers the toner image onto a transfer material. The present invention relates to a multi-color image forming apparatus that obtains an image by double-transferring onto a sheet.

(Prior Art) Recently, not only in special fields but also in the field of general office work, the demand for color copying rapidly increases, and there is a strong demand for color copying machines that can be used by not only professionals but also anyone. At present, as a color copying machine, a full-color electrophotographic copying machine using electrophotographic technology is generally widely used. The full-color electrophotographic copying machine still has various problems to be solved or improved. One of them has a structure in which a transfer drum for gripping and surrounding the transfer material is formed in order to transfer the transfer material to the transfer material plural times. There is something to do.

Conventionally, a color electrophotographic copying machine having a structure as shown in FIG. 2 has been proposed.

A conventional example will be described with reference to the configuration of FIG. 2. In the figure, reference numeral 1a denotes a photosensitive drum that constitutes an image carrier, and rotates in the direction of arrow 2a. Around the photosensitive drum 1, a charger 12a, a developing unit group 13a, a transfer drum 20a,
A cleaning device 27a is arranged. Reference numerals 10a and 11a are laser optical systems, which form a drum based on the color-separated image information signal.
Form an image on 1a. 10a is a polygon mirror, and 11a is a laser reflection mirror. The developing unit group 13a is a revolving-type developing unit 13 which uses Y, M, C, and Bk developers, respectively.
It consists of 1a, 132a, 133a and 134a.

When forming an image of a specific color on the drum 1a, the developing unit 131a, 132a, 133a or 134a of that color is set on the drum 1a.
When an image is formed adjacent to, and an image of a color different from that is formed, it is rotated in the direction of arrow 135a so that the developing unit of the desired color is adjacent to drum 1a.

Reference numeral 15a is a cassette for accommodating the transfer material 14a (usually plain paper is used). Transfer material 14a in cassette 15a (hereinafter,
The transfer paper (referred to as transfer paper) is supplied to the cassette 1 by the paper feed roller 16a.
It is sent out from the sheet 5, passes through the first registration roller pair 17a and the second registration roller pair 18a, and is sent to the paper feed guide 19a. The transfer paper sent is passed through the first and second registration rollers 17a,
Timing is taken by 18a, and the tip is gripped by the gripper 201a on the transfer drum 20a. The gripped transfer paper passes between the suction charger 23a and the squeezing roller 22a, and is sucked and held by the suction sheet 202a on the transfer drum 20a over the entire area. An image on the drum 1 is transferred to the attracted transfer paper by the transfer charger 24a. The transfer process is repeated for each color, and when the transfer is completed, the gripper opens and is guided to the transport unit 29a by the separation claw 28a. The transfer paper guided to the transport unit 29 is a fixing roller pair 30a, 31.
It is passed through a to be fixed, and is placed on the tray 32a. The image remaining on the drum 1a after the transfer process is cleaned by the cleaning device 27a, and the drum is prepared for the next image formation. 25a,
Reference numeral 21a is a cam that opens and closes the gripper on the transfer drum.

(Problems to be Solved by the Invention) In order to hold the transfer paper on the transfer drum under such a configuration, according to the opening timing of the gripper present in a part of the transfer drum rotating at a constant speed, The transfer paper must be transported. Therefore, it is necessary to accurately detect the gripper position of the transfer drum and to accurately convey the transfer roller by the registration roller. When the printing speed is increased, the rotation speed of the transfer drum is also increased, and it is very difficult to set the timing for gripping.

Furthermore, at the moment when the transfer paper is gripped by the gripper, the transfer paper has to be carried out by the registration roller at a speed higher than the peripheral speed of the transfer drum. If the opening timing of the gripper of the transfer drum is earlier or later than the opening timing, a grip mistake occurs and image formation becomes impossible.

Further, a cam for opening the gripper at the time of gripping in the transfer drum, and a pushing-up mechanism for opening the gripper at the separating position and pushing up the front end of the transfer paper wound around the transfer paper are required.

In addition, there are drawbacks such as exposure unevenness and transfer unevenness due to shocks during operation of the cam.

Therefore, the main object of the present invention is to remove grippers from the transfer drum to be wound around the transfer paper to eliminate grip mistakes, and at the same time to eliminate cams in the transfer drum, simplify the transfer drum, and smooth the rotation of the transfer drum, thereby eliminating image defects. It is an object of the present invention to provide a multi-color image forming apparatus that does not have any color.

(Means) According to the present invention for achieving the above object, an image carrier that carries an image, a transfer material carrier that carries and rotates a transfer material, and an image carrier and the transfer material carrier are provided. A transfer means for conveying the transfer material to the general contact, and a transfer charging means provided in the transfer material carrying body of the general contact, for transferring the transfer material carried on the transfer material carrying body by the transfer charging means. In a multiple image forming apparatus that sequentially transfers images of the image carrier, the transfer charging unit electrostatically adsorbs a transfer material to the transfer material carrier at the approximate contact, and then transfers the transfer material carrier. The image on the image carrier is transferred while the transfer material carried on the sheet passes through the approximate contact point.

(Embodiment) Next, an embodiment of the multicolor image forming apparatus according to the present invention will be described in detail with reference to the drawings.

The image forming apparatus according to the present invention is applied to a mono-color image forming apparatus such as a two-color copying machine, a full-color copying machine, a printer, etc. In this embodiment, an electrophotographic full-color printer to which the Carlson process is applied will be described. To do.

FIG. 1 is a schematic sectional view of a full color printer according to the present invention. In the figure, a photosensitive belt 1 as an image carrier is an endless belt that is hung between a belt pulley 2 and a belt pulley 3, is rotating in the direction of the arrow in the figure, and is a transfer material at a position approximately directly above the belt pulley 3. A transfer drum 4 as a carrier, and a cleaning device 5 and a primary charging device 6 are arranged in this order in the rotation direction thereof, and further in the traveling direction of the belt, between the belt pulley 3 and the belt pulley 2 and a straight line below the photosensitive belt. Part, yellow developer 7 from the right
(Y), magenta developing device 7 (M), cyan developing device 7
(C), a black developing device 7 (Bk) is arranged.

A scanner device 8 includes a semiconductor laser that converts an electric signal into an optical signal, a rotating polygon mirror that scans in a horizontal direction, and the like. A laser beam changes its optical path by a reflecting mirror 9 according to an image signal. Then, a latent image is formed on the photosensitive belt 1 at a position substantially below the belt pulley 3.

On the other hand, the transfer paper is stored in the cassette 10, and after being fed from the cassette in response to a paper feed signal, it is conveyed by the conveyance roller 111 and the conveyance guide 112 while aiming at the contact point between the transfer drum 4 and the belt pulley. .

As shown in FIG. 3, the transfer drum is formed by cutting out a hollow cylindrical body portion to form ring-shaped portions 41, 42 at both ends and a connecting portion 43 for connecting these ring-shaped portions. A sheet that electrostatically supports the transfer paper, such as Mylar film 44
Is wrapped around. A transfer charger 12 is provided inside the transfer drum so as to face a contact point between the transfer drum 4 and the belt pulley 3.

The transfer paper that has entered this contact portion is electrostatically adsorbed on the Mylar film on the peripheral surface of the transfer drum by the output of the transfer charger 12 as the transfer charging means, and is wound around the transfer drum to the rear end. The timing of winding the transfer paper around the transfer drum is such that the entire length of the transfer paper in the transport direction covers the Mylar film surface.

That is, it suffices to feed the transfer paper after the connecting body portion 43 of the transfer drum shown in FIG. 3 has passed the transfer charger position. This timing does not have to be strictly controlled, and the synchronization with the image is taken by the transfer paper leading edge detection sensor 113 as a position detecting means for detecting the transfer material leading edge on the transfer drum after the transfer sheet is wound. .

The transfer drum 4 rotates at the same peripheral speed as the photosensitive belt, and at the moment when the transfer paper passes the transfer paper leading edge detection sensor 113, an image is written from the scanner 8 by an output signal from the sensor.

In the case of forming a full-color image, first, a latent image is formed on the photosensitive belt 1 from the yellow image signal from the scanner.
Then, the image is visualized by the yellow developing device 7 (Y) and heads to the transfer position B.

The length along the photosensitive belt 1 from the image writing position A to the transfer position is equal to the distance from the transfer paper leading edge detection sensor 113 to the transfer position on the peripheral surface of the transfer drum.
Therefore, the Y developed image formed on the photosensitive belt is transferred in synchronization with the transfer material. Similarly, next, M developing device 7
(M) to form a magenta image, C developing unit 7 (C) to form a cyan image, and Bk to form a black image using the developing unit 7 (Bk). vessel
Overprinted by 12 outputs.

After the Bk image is transferred, the transfer paper is separated from the transfer drum at the separation point C by outputting the static eliminator 13 to neutralize the attraction between the transfer paper and the transfer drum and by the separation claw 14.
Then, the multi-toner image on the transfer paper is fixed by the fixing device 16 by being conveyed by the conveying belt 15, and is discharged onto the tray 17.

FIG. 4 shows a timing chart in the case where an A4 size transfer sheet is used in the image forming apparatus according to the present embodiment, after the transfer sheet reaches the transfer position.

The transfer drum is φ160 and can output transfer paper up to A3. First, at the first rotation of the transfer drum, the transfer charging device outputs one round of the transfer drum to adsorb the transfer paper onto the transfer drum. When the transfer material tip sensor 113 is turned on for the transfer paper,
At the same time, Scanner writes a Y (yellow) image. When the transfer paper passes through the transfer material front end sensor to the rear end, the transfer material sensor is turned off, and at this moment, the laser output of the scanner is stopped. The length of the transfer paper can be detected from the ON time range of the transfer material sensor.

From which writing position A to Y
From the timing when the belt advances to the developing position, the Y developing device is driven to obtain a Y (yellow) developed image. Then, the transfer drum enters the second rotation and outputs the transfer high voltage.

The output of the development drive and the transfer may be performed at least for the length of the paper, but it is better to allow for the rise time and the fall time.

When the transfer material sensor is turned on at the second rotation, the latent image is formed by the magenta signal from the scanner, and similarly, the magenta image is visualized and transferred to the transfer material. After that, the same process as the cyan image and the black image is repeated. Then, at the separation position of the fifth rotation of the transfer drum, the separation claw and the separation static eliminator are output. The separation claw should be about the length of the transfer paper,
The static eliminator neutralizes the surface of the transfer drum, so at least 1
The lap is done.

As described above, after the transfer paper is wound around the transfer drum, the sequence may be updated every time with the signal of the transfer material sensor as a reference. After that, the sequence may be executed in correspondence with the preset number of clocks.

Further, in order to send the transfer material to the contact position on the transfer drum 4 and the belt pulley 3, it is better to send the transfer material by the conveying roller 111 from the tangential direction from the contact as shown in FIG.

In the above-mentioned embodiment, the belt is exemplified as the carrier, but it may be in the form of a drum.

(Effects of the Invention) As described above, in the present invention, since the transfer material is adsorbed to the transfer material carrier by the transfer charging means, a gripper is not required, and strict control for transporting the transfer material to the transfer material carrier is unnecessary. is there.

Further, in the present invention, the transfer material is once passed through the approximate contact point between the transfer material carrier and the image carrier, and electrostatically adsorbed to the transfer material carrier up to the rear end thereof by the transfer charging means, so that the transfer material is leveled. It is possible to prevent air from entering between the transfer material and the transfer material carrying body without providing a special roller member. Therefore, the transfer material can be surely adsorbed, and a high-quality image can be obtained without causing a transfer failure.

[Brief description of drawings]

1 is a sectional view of a full-color recording apparatus to which the present invention is applied, FIG. 2 is a sectional view of a conventional full-color copying machine, FIG. 3 is a perspective view of a transfer drum, and FIG. 4 is an example of control of the apparatus of the present invention. The timing chart shown in FIG. 5, and FIG. 5 are explanatory views showing an example of feeding according to the present invention. In the figure, 1 ... Photosensitive belt 4 ... Transfer drum 12 ... Transfer charger 41, 42 ... Ring part 43 ... Connection part

Claims (1)

[Claims] 1. An image carrier that carries an image, a transfer material carrier that carries and rotates a transfer material, and a carrier that carries the transfer material to a general contact point between the image carrier and the transfer material carrier. Means and a transfer charging means provided in the transfer material carrier at the approximate contact, and sequentially superimpose the images of the image carrier on the transfer material carried by the transfer material carrier by the transfer charging means. In the multiplex image forming apparatus for transferring by transfer, the transfer charging means electrostatically adsorbs the transfer material to the transfer material carrier at the general contact, and then the transfer material carried on the transfer material carrier is transferred to the transfer material carrier. A multiple image forming apparatus, wherein the image of the image carrier is transferred while passing through the contact points.