JPH0511314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a transfer device in an image forming apparatus having a transfer drum equipped with a gripper.

Prior Art In an image forming apparatus having a transfer drum equipped with a gripper, a presser roller is disposed on the circumferential surface of the image forming apparatus in order to hold the transfer paper on the transfer drum.
However, when such a device is used in a color image forming apparatus using an overlapping transfer method, the presser roller hits the image surface during the second rotation and disturbs the colors transferred during the first rotation. Also, this roller must be spaced apart to avoid disturbance. however,
At the time of separation, the transfer paper on the surface of the transfer drum is vibrated, making it impossible to obtain sharp copies and also making the structure complicated.

Purpose The present invention aims to eliminate stains on the copy surface caused by a transfer paper press roller, etc., and also to eliminate transfer blur caused by vibration during pressure contact, thereby obtaining sharp copies.

Configuration FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus (Japanese Utility Model Publication No. 120546/1983) having a transfer drum equipped with a gripper, in which a copy 2 on a document placement glass 1 is placed on a proof optical system. The electrostatic latent image is exposed onto the photoreceptor drum 4 by the device 3, and the electrostatic latent image is made into a visible image by the developing device 5. On the other hand, the transfer paper S from the cassette 6 is sent to the transfer drum (transfer paper holding drum 9) through a paper feed roller 7 and a timing roller 8, and is fed to a transfer drum (transfer paper holding drum 9) provided on the circumference of the transfer drum 9, which can be opened and closed. The leading edge of the transfer paper is held between the sheet gripper 11 and the transfer drum 9. And presser roller (straining roller)
12, the transfer paper is tightly wrapped around the drum circumferential surface, and the leading edge of the transfer paper and the leading edge of the visible image forming area on the photoreceptor drum 4 are aligned at the transfer position 13. The visible image is then transferred onto the transfer paper by the transfer charger 14. After this transfer, residual toner on the photosensitive drum 4 is removed by a cleaning device 10.

In this image forming apparatus, electrostatic latent images are formed on the photoreceptor drum 4 according to the number of color separations, and the transfer drum 9 rotates by the number of color separations, until the final image is formed. When the gripper 11 comes to the vicinity of the transfer paper peeling claw 16 after completing the transfer, the gripper 11 opens while the discharging separation charger 15 assists in separating the leading edge of the transfer paper.
The leading edge of the transfer paper is lifted off the circumferential surface of the transfer drum 9 and separated. Next, the leading edge of the transfer paper rides on the peeling claw 16 and is completely separated from the drum circumferential surface, after which the transfer paper passes through a fixing device 17 and a pair of discharge rollers 18, and is discharged and stored in a tray 19.

However, in such an image forming apparatus,
As described above, the squeezing action of the presser roller 12 on the transfer paper during several transfer steps caused disturbances in the transferred colors, making it impossible to obtain sharp copies.

Therefore, in the present invention, the transfer paper is reliably gripped and conveyed to the transfer position 13 without using the presser roller 12.

FIG. 2 is a schematic explanatory diagram of an image forming apparatus equipped with a transfer device according to the present invention, with the presser roller 12 shown in FIG. 1 removed. In the present invention, as in the conventional apparatus shown in FIG. The transfer paper is sent out by the timing roller 8, which rotates in a certain relationship, and meets the gripper 11 at point A, where the leading edge of the transfer paper is gripped. It is necessary to insert the transfer paper by moving the transfer paper speed faster than the gripper speed for a short time after the leading edge of the transfer paper meets the gripper speed. However, at this time, the leading edge of the transfer paper fed by the timing roller 8 is not necessarily perpendicular to the direction of travel, so if the transfer paper is fed by a length equal to the gripper depth, one end of the transfer paper will not reach the grip of the gripper. Sometimes it doesn't reach the department.

For this reason, in the present invention, as shown in FIG. 3, the transfer paper is fed to the gripper 11 by a length longer than the length required for the grip, and the transfer paper is continued to be fed while slackening the transfer paper until the gripper 11 reaches the transfer position. That's what I do.

If it passes through the transfer position 13, the transfer charger 1
4, the transfer paper tightly adheres to the circumferential surface of the transfer drum 9. By doing this, the leading edge of the transfer paper is accurately gripped by the gripper 11, and the occurrence of transfer paper dropping, jamming, etc. can be prevented.

That is, the transfer paper S sent from the cassette 6 and waiting with its leading end stopped by the timing roller 8 is transferred to the gripper 11 on the photosensitive drum 4 (provided on the ring body 21 of the transfer drum 9, and gripped by a grip piece). The transfer paper feed timing roller 8 rotates at a predetermined timing with respect to the grip mechanism 22) consisting of the transfer paper guide G, and the transfer paper guide G meets the gripper 11 at point A. The paper is gripped and moves in the direction of the arrow until it reaches the transfer position 13, where it is transferred by the transfer corona. It rotates at a peripheral speed faster than the speed on the surface, so that a slack is created between the transfer paper S and the transfer drum 9. If you do this,
The leading edge of the transfer paper is kept pressed against the gripper 11 until it reaches the transfer position 13. In order to do this, the length of the transfer paper path between the transfer position 13 and the timing roller 8 may be made shorter than the length of the transfer paper. Further, in order to prevent the leading edge of the transfer paper from hanging down from the transfer drum while being separated from the transfer paper guide G, it is preferable to provide an appropriate guide.

The transfer charger 14 not only transfers the toner on the photoreceptor drum 4 onto the transfer paper when the transfer paper passes the transfer position 13, but also uses Coulomb force during corona discharge to move the transfer paper around the transfer drum. It also has the effect of adsorbing it to the dielectric film on the surface.
Since the transfer paper and the holding drum 9 rotate as one, the force that pulls the transfer paper as it passes the transfer position is the grip force + electrostatic adsorption force, which is far greater than the grip force alone. growing.

Effects In the present invention, the transfer paper maintains a constant bulge relative to the transfer drum circumferential surface until the leading edge of the transfer paper passes the transfer position 13 without using the conventionally used press roller (straining roller). By rotating the timing roller 8 in such a manner that the leading edge of the transfer paper is always pushed in the direction of being pushed into the gripper 11, the leading edge of the transfer paper is kept in good alignment and does not fall off.

Therefore, it is possible to prevent the transfer paper from falling or jamming when receiving the transfer paper, and since no presser roller is used, there is no staining or deformation of the transferred image, and registration (copy position) also becomes better.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a conventional example of an image forming apparatus, FIG. 2 is a schematic configuration diagram similar to FIG. 1 of an image forming apparatus according to the present invention, and FIG. 3 shows the configuration of the transfer device in FIG. FIG. 4... Photosensitive drum, 8... Timing roller, 9... Transfer drum, 11 Transfer paper gripper,
12...Press roller, 13...Transfer position, 14...
...Transfer charger, 22...Grip mechanism, G...
...Transfer guide, S...Transfer paper.

Claims (1)

[Claims] 1. In a transfer device of an image forming apparatus having a transfer drum composed of a gripper and a dielectric film, the length of the transfer paper path between the transfer position and the timing roller is made shorter than the length of the transfer paper, and the length of the transfer paper path between the transfer position and the timing roller is made shorter than the length of the transfer paper. Without providing a transfer paper pressing roller, the transfer paper is kept bulging at least until the leading edge of the transfer paper gripped by the gripper reaches the transfer position.
A transfer device characterized in that the timing roller continues to rotate while feeding the transfer paper.