JPH0219814Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) This invention is based on a transfer device for an electrostatic copying machine, in particular, a transfer paper is applied to the peripheral surface of a rotary frame body in which a cylinder is cut out leaving both ends of the cylinder and a band-like connecting part connecting these parts. The toner image is transferred to the toner image on the rotary frame by a transfer charger disposed inside the rotary frame at a position where the rotary frame contacts the image carrier holding the toner image to be transferred. The present invention relates to a type of transfer device that transfers onto the surface of transfer paper.

(Prior art) Regarding this type of transfer device, Japanese Patent Publication No. 50-93434, No. 51-78340, No. 53-104248,
No. 54-19750, No. 55-38502, No. 55-18653, No. 55-
It is described in various publications such as No. 110278.

Before starting a detailed explanation of this invention, an outline of a color electrostatic copying machine equipped with such a transfer device will be explained with reference to FIGS. 1 and 2. Around the photosensitive drum 1 having a photoconductive layer on its surface, along the counterclockwise direction of rotation, there are a charging charger 2, an erase lamp 3, a yellow developing device 4, a magenta developing device 5, a cyan developing device 6,
A transfer drum 7, a first static elimination charger 8, a cleaning device 9, a second static elimination charger 10, and the like are arranged. Further, an exposure optical system 11 is arranged above the photoconductor drum 1, and an exposure lamp 14 for illuminating a color original 13 on an original table glass 12 is integrated with the exposure optical system 11 on the left side in the figure. The first mirror 15 moves at a speed V in the direction, the speed V/
2, the second mirror 16 and the third mirror move in the same direction.
It includes a mirror 17, a stationary imaging lens 18, a fourth mirror 19, a color separation filter 20, and the like.

As shown in FIG. 2, the transfer drum 7, which comes into contact with the photoreceptor drum 1 and moves in the same direction as the surface of the photoreceptor drum 1 at its contact point, has a cylinder with both ends 21a, 21b and a belt-like link connecting these ends. Part 2
It consists of a rotating frame body 21 which has been cut out leaving only part 1c, and a dielectric film 22 such as mylar attached to cover the cut out part of this frame body, and a gear 23 provided at one end of the frame body By meshing with a gear 24 provided at one end of the drum 1, the photosensitive drum 1 and the transfer drum 7 are synchronized. An opening 25 is provided along the longitudinal direction of the band-like connecting portion 21, and a paper clamper 26 looks through this opening as schematically illustrated in FIG. It is held at 7.

The surface of the photosensitive drum 1 is first uniformly charged to a predetermined polarity by the charging charger 2, and then the charged charges in the non-image area are erased by the raise lamp 3. Then, a first image exposure is performed through the exposure optical system 11, and the charged charges are selectively erased in correspondence with the original image, and an electrostatic latent image is formed thereon. During this first image exposure, the blue filter BF of the color separation filter 20 is used, and the electrostatic latent image formed on the photoreceptor drum 1 is mainly composed of a yellow component, which is a complementary color to blue. This is developed by being supplied with yellow toner from the yellow developing device 4. This developed yellow toner image is selected and sent from the paper feed cassettes 27 and 28, and is wrapped around the transfer drum 7 by the clamper 26. The photosensitive drum 1 and the transfer drum 7 The images are overlapped at a position where they touch each other and transferred onto a transfer paper by a transfer charger 29 arranged inside the transfer drum 7 at that position. The photosensitive drum 1 after transfer is
The residual potential on the surface is eliminated by the first static eliminating charger 8, the residual toner is removed by the cleaning device 9, and the static electricity is further eliminated by the second static eliminating charger 10, thereby completing the first copying process. Next, the second copying process begins, and after charging, a latent image is formed using a green filter GF, which is developed by the magenta developing device 5, and the developed image is transferred onto the transfer paper held by the transfer drum. The image is superimposed on the yellow image. Next, static electricity removal and cleaning are performed in the same way, and then a third copying process is performed, and the red filter RF
A cyan toner image is formed using the cyan developing device 6 and the cyan toner image is further transferred onto the transfer paper on the transfer drum 7 in an overlapping manner. After the three image transfers in which the transfer voltage was sequentially increased in this way, the transfer drum 7 and the transfer paper thereon are transferred to the double static elimination charger 30,
When the clamper 26 removes the leading edge of the transfer paper and lifts it up, the transfer paper is separated by the separation claw 32.
The sheet is separated from the transfer drum 7 by the rollers 34, enters the fixing device 33, receives the transferred color toner image, and is then discharged onto the tray 35 by the sheet discharge rollers 34. One of the photoreceptor drums 1 is similarly subjected to charge removal and cleaning to complete the copying process. In addition, the code|symbol 36 is a brake.

Now, in transfer methods that generally use a corona charger, including such transfer devices,
The relationship between the area where the transfer paper contacts the toner image carrier and the area where the transfer paper is irradiated with corona ions is as follows:
It is known that this has a large effect on the quality of transferred images. Generally, it is said that when corona is irradiated to the area of the transfer paper before it contacts the toner image carrier and after the transfer paper is separated from the toner image carrier, transfer blur occurs in that area. Therefore, JP-A No. 53-48529, 53
-114442, 56-36673, 57-68880, etc., various proposals have been made regarding the limitation of the contact area of the transfer paper and the corona irradiation area. Disturbance of the image due to peeling discharge that occurs when it is separated from the carrier is particularly noticeable.

Regarding such a problem of peeling discharge, there is a new and different situation in the case of the transfer method as in this invention. This is because the transfer paper contacts the toner image carrier while being held on the circumferential surface of the rotating frame, so the contact area is extremely narrow. For example, as shown in FIG. 3, the conventional transfer charger 29 is located inside the position where the rotating frame 21 contacts the photoreceptor drum 1, and more precisely, between the center CT of the rotating frame 21 and the photoreceptor drum 1. The corona wire electrode 29a of the transfer charger 29 is located on the line connecting the center CP. Therefore, the transfer paper 37 held on the circumferential surface of the rotating frame 21 via the dielectric film 22 comes into almost linear contact with the photosensitive drum 1, and transfer and separation occur within this narrow contact area. Since this is performed continuously, peeling discharge is likely to occur when the transfer paper is separated. This separation discharge is caused partly by the fact that the rotating frame 21 rotates clockwise, so that the corona ion flow flows toward the transfer paper separation side. Mainly as a result of this peeling discharge, the tone of a plane image is not uniform, and bleeding occurs in a line image.

(Purpose of the invention) The purpose of the invention is to provide an improved transfer device as described above that can obtain transferred images of good quality.

The transfer device according to this invention is characterized in that the transfer charger is disposed slightly in front of the position where the rotating frame contacts the toner image carrier in the direction of rotation thereof. In addition to the photoreceptor, a dielectric material is used as the toner image carrier, and in addition to the drum shape, a plate shape is also used. In addition to those with a dielectric film affixed thereto, those with mesh or wire stretched over them, or those without any tension are used for the rotating frame.

An embodiment of this invention will be described below with reference to FIG.

(Structure of the invention) In FIG. 4, the effective charging range of the transfer charger 29 for the transfer paper is a line connecting the rotation center CT of the rotating frame 21 and the rotation center CP of the photosensitive drum 1 as an image carrier. In addition, the corona wire electrode 29a is arranged at a position offset from the above line by a distance b to the upstream side in the rotational direction of the rotating frame 21.

The photosensitive drum 1 and the rotating frame 21 each have an outer diameter of 120 mm, and are driven to move in the same direction at their contact points at a circumferential speed of 125 mm/S. A dielectric film 22 with a thickness of 100 to 120 μm is provided in the cutout portion of the rotating frame 21.
A polyester film is adhered thereon, and a transfer paper 37, which is plain paper, is held on top of the polyester film by gripping the tip with a paper gripper and electrostatic adsorption. The material of the dielectric film 22 is explained in detail in Japanese Patent Application Laid-Open No. 18633/1983.

The transfer charger 29 has a semicircular shield case with an inner radius of about 10 mm, and its corona wire electrode 29a is connected to the photosensitive drum 1 by the rotating frame 21.
From the tangent at the point touching the center of the rotating frame 21
It is located approximately 10mm down in the CT direction.
A DC voltage of 4 to 6 KV (4.2 to 4.5 KV in the case of monochromatic black and white) having a polarity opposite to that of the toner image is applied to the wire electrode 29a, and then to the static elimination chargers 30 and 31, a DC voltage of 4 to 5.5 KV is applied. An alternating current voltage of KV is applied.

Under the same conditions as the conventional transfer charger 29 of this invention, the wire electrode 29a is positioned downstream from the conventional position by a distance d, preferably 2 to 4 mm. It is located in

(Effect of the invention) It is known that in a corona charger, the electric field is the strongest in the portion directly below the corona wire electrode. Therefore, if the position of the corona wire electrode is slightly shifted to the downstream side as in this invention, the electric field on the side where the transfer paper is separated during transfer becomes weaker and the peeling discharge becomes smaller, thereby reducing image disturbance. In addition, in the conventional case, the corona ion flow dragged by the rotation of the rotating frame 21 was located at the part where the transfer paper 37 separates from the photoreceptor drum 1, but in this invention, the flow of corona ions dragged by the rotation of the rotating frame 21 is located exactly at the part where the transfer paper 37 separates from the photoreceptor drum 1. Since it is applied to the point of contact with the drum 1, it contributes favorably to the transfer, but does not promote peeling discharge. Therefore, according to the transfer device of this invention, this can be easily achieved by simply changing the position of the transfer charger, without the need for any special additional equipment, without causing blurring or blurring in the transferred image. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an electrostatic copying machine to which this invention is applied, FIG. 2 is a schematic perspective view showing a photosensitive drum and a transfer drum in the apparatus shown in FIG. 1, and FIG. FIG. 4 is a diagram showing the position of a conventional transfer charger, and FIG. 4 is a diagram showing the position of a transfer charger in this invention. 1...Photosensitive drum, 7...Transfer drum, 21
... Rotating frame body, 22 ... Dielectric film, 29 ...
...Transfer charger, 37...Transfer paper.

Claims (1)

[Claims for Utility Model Registration] Transfer paper is held on the circumferential surface of a rotating frame body which is obtained by removing a cylinder leaving both ends thereof and a band-like connecting part connecting these parts, and the rotating frame body transfers a toner image to be transferred. A transfer charger disposed inside the rotating frame at a position in contact with the held image carrier,
In a copying device of an electrostatic copying machine that transfers the toner image onto the surface of the transfer paper on the rotating frame, an effective charging range of the transfer paper by the transfer charger is between the center of rotation of the rotating frame and the image carrier. The transfer charger is placed at a position that includes a line connecting the center of rotation of the body and the center of the effective charging range in the rotational direction of the rotational frame is offset from the line to an upstream side in the rotational direction of the rotational frame. A transfer device for an electrostatic copying machine, characterized in that: