JPS61239273A - Toner image transfer device - Google Patents

Abstract

PURPOSE:To attain a good registration for toner image transfer and to attain a good transfer image without toner image scattering by providing an air blow- off nozzle above a transfer corotron in the form carrying direction. CONSTITUTION:A gripper 56 is attached rotatably to a gripper bar 32 and is always energized in such a direction that it is closed to a sheet 58 of the gripper bar 32. The gripper 56 of the gripper bar 32 is opened in the position of a reference sensor and the position of a driving sprocket by an actuator to grip or release a form 22. An air blow-off nozzle 60 is provided above a transfer corotron 48 in the form carrying direction, and air is blown to the lower face of the form 22 from a nozzle front end 62, and the form 22 is so guided that it is brought into close contact with a photosensitive drum 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a toner image transfer device for transferring a toner image on a photosensitive drum onto a sheet of paper using a transfer corotron.

In an electrophotographic copying machine or a printer using electrophotography, the surface of the photosensitive drum is generally uniformly charged by a charging corotron, and then an electrostatic latent image corresponding to the document is transferred to the photosensitive drum by an image exposure device. An electrostatic latent image formed thereon or corresponding to an input image signal is formed on the photosensitive drum.

After this electrostatic latent image is developed and visualized by a developing device such as a magnetic brush developing device, the toner image on the photosensitive drum is transferred onto a sheet of paper by a transfer corotron at the next transfer station.

When a transfer corotron is used to transfer a toner image on a photosensitive drum onto a sheet of paper, it is important to ensure that the sheet of paper contacts the photosensitive drum in the transfer area. In a paper transport system using transport rollers, in order to ensure that the photosensitive drum and paper come into contact in the transfer area, a paper guide plate is installed so that the paper enters the photosensitive drum upstream of the transfer area. There is. Also, hold the paper using chain gripper 1.
In the case of a paper feeding device, a paper support plate is provided so that the paper comes into contact with the photosensitive drum, and when the chain gripper passes under the photosensitive drum, a paper support plate is provided to allow the paper support plate to escape downward. A mechanism is provided to prevent interference between the paper support, holding plate, and chain gripper.

The structure of a copying machine having such a gripper conveyance mechanism will be further explained with reference to FIG. A photosensitive drum 10 made of amorphous selenium or the like is uniformly charged by a charging corotron 12, and an electrostatic latent image corresponding to a document 16 is formed on the photosensitive drum 10 by an image exposure device 14. The electrostatic latent image formed on the photosensitive drum is developed and visualized by a developing device 18 such as a magnetic brush developing device.

On the other hand, the paper 22 stacked on the paper feed tray 20 is sent out by the rotation of the feed roller 24, and is sent via the conveyance roll 26 to the gut roll 28, where the skew (diagonal feeding) of the paper is corrected and the transfer timing is adjusted. be done. Reference numeral 30 denotes a paper conveyance chain, which is wound around a driving sprocket 29 and a driven sprocket 31, and its tension is adjusted by a tension sprocket 33. 32 is a gripper bar attached to the chain 30, and the chain and the gripper bar constitute a chain gripper.

The gripper bar 32 is opened and closed by the operation of an actuator 34, and grips and releases the leading end of the paper 22. That is, when the chain 30 rotates counterclockwise and the actuator 34 reaches the position of the reference sensor 36, the actuator 34 is pressed by a pressing member (not shown) to open the gripper bar 32, and at the same time, the gate roll 28 The paper 22 is sent out from the gripper bar 32, and after the leading edge of the paper is gripped by the gripper bar 32, the gripper bar is closed.

The reference sensor 36 mentioned above is also used as a signal to write an image on the photosensitive drum 10 or a signal to start exposure,
This reference sensor 36 determines the timing of conveyance of the toner image on the photosensitive drum 10 and the conveyance of the paper 22 being conveyed. When the leading edge of the paper 22 is gripped and conveyed by the gripper bar 32, the rear end of the paper 22 is free and released.

Reference numeral 38 denotes a paper support plate, which functions to press the paper gripped by the gripper bar and conveyed toward the photosensitive drum. That is, the paper support plate 38 is connected to a link 40, which is rotatably supported around a rotation fulcrum 42 and biases the paper support plate 38 counterclockwise by a spring 44. When the gripper bar 32 grips the leading edge of the paper and approaches the photosensitive drum 10, the solenoid 46 is energized and rotates the paper support plate 38 clockwise to prevent interference between the paper support plate and the gripper bar 3. .

When the gripper bar 32 passes the transfer corotron 48,
The paper 22 is electrostatically attracted to the photosensitive drum 10, and the toner image on the photosensitive drum is electrostatically moved to the paper for transfer. In this case, a voltage is applied to the transfer corotron 48 so that the polarity of the electric discharge of the transfer corotron 48 is opposite to the charging polarity of the toner to accomplish the transfer.

At or slightly before the gripper bar 32 passes the transfer corotron, the excitation of the solenoid 46 is cut off, and the condensing paper support plate 38 rotates counterclockwise about the fulcrum 42 to transfer the paper onto the photosensitive drum 10. The photosensitive drum 10 and the paper are guided so that they are in close contact with each other.

The paper 22 on which the toner image on the photosensitive drum has been transferred by the transfer corotron 48 is gripped by the gripper bar 32 and conveyed as the chain rotates. When the gripper bar 32 reaches the position of the drive sprocket 29, the actuator 34 is moved by a suppressing member (not shown). is pressed to open the gripper bar 32 and release the paper from the gripper bar.

After the toner image on the paper 22 released from the gripper bar 32 is fixed by the fixing roller 50 and made into a permanent image,
The paper is discharged into the paper discharge tray 52. - The untransferred toner image, that is, the residual toner image on the photosensitive drum is cleaned by a cleaning device 54 such as a cleaning blade, and one copy cycle is completed.

Problems to be Solved by the Invention However, as described above, in an apparatus in which paper is conveyed by a chain gripper and a toner image on a photoreceptor is transferred onto the paper by a transfer corotron, paper support is required to avoid interference with the gripper bar. The board had to be retracted and raised and controlled. For this reason, the operation control between the chain gripper and the paper support plate becomes complicated, the registration of the transferred toner image varies depending on the operation of the paper support plate, and the gripper bar moves up the paper support plate after passing the paper support plate. Therefore, there were problems such as the inability to set detailed timing.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a toner image transfer device with a simple structure and high transfer accuracy in a copying machine or printer employing a chain gripper paper conveyance device, which overcomes the deficiencies of the prior art described above.

Means for Solving the Problems In order to solve the above-mentioned problems of the prior art, the present invention grasps and conveys the leading edge of paper with a chain gripper, and transfers the toner image on the photosensitive drum by a transfer corotron. The present invention provides a toner image transfer device for a copying machine or a printer configured to transfer images onto a sheet, characterized in that an air blowing nozzle is provided upstream of the transfer corotron in the sheet conveyance direction.

According to a preferred embodiment of the present invention, the gripper bar of the chain gripper is provided with an inclination angle such that when the paper is gripped, the leading edge of the paper is held slightly upward from the horizontal direction. By providing the gripper bar with an inclination angle in this manner, the paper can be conveyed in close contact with the photosensitive drum.

According to the present invention, an air blowing nozzle is provided on the upstream side of the transfer corotron in the sheet conveying direction in place of the conventional paper support plate, so that air is constantly blown out from the air blowing nozzle. In this way, the paper is lifted and lifted by the air flow and is conveyed in close contact with the photosensitive drum, and in the transfer area, the paper is brought into close contact with the photosensitive drum, and the transfer corotron causes the toner image on the photosensitive drum to be conveyed. will be transferred onto the paper with high precision. Furthermore, instead of blowing out the air from the air blowing nozzle all the time, a control method may be adopted in which the air is blown out only when the paper is conveyed by the gripper bar.

Further, if the gripper bar is provided with an inclination angle as in the above-described preferred embodiment, the leading edge of the paper can be curled upward in advance, and the closeness between the paper and the photosensitive drum can be increased.

EXAMPLES The present invention will be explained in detail below based on examples shown in the drawings. FIG. 1 shows a schematic side view of the structure of the present invention, and FIG. 2 shows a perspective view thereof.

In FIGS. 1 and 2, the charging device, exposure device, developing device, cleaning device, etc. necessary for the electrophotographic copying machine explained in conjunction with FIG. 3 are omitted, but this is only for convenience of explanation. Of course, the apparatus shown in FIGS. 1 and 2 also includes these components. In FIG. 1, a gripper 56 is rotatably attached to the gripper bar 32 with a pin 57, and is always biased in the closing direction against the seat 58 of the gripper bar 32 by biasing means (not shown). As shown in the figure, the sheet 58 is provided with an inclination angle that guides the leading edge of the paper 22 upward. According to experiments, this angle of inclination is preferably around 5 degrees.

The gripper 56 of the gripper bar 32 is moved by an actuator (not shown) at the reference sensor 36 position and the two drive sprocket positions shown in FIG. 3 to grip or release the sheet 22.

An air blowing nozzle 60 is provided on the upstream side of the transfer corotron 48 in the paper conveyance direction, and air is blown from the nozzle tip 62 onto the lower surface of the paper 22 in the direction of the arrow to guide the paper so that it comes into close contact with the photosensitive drum 10. are doing. As shown in FIG. 2, the air blowing nozzle 60 is connected to a fan 64, and the air sucked by this fan is sent to the photosensitive drum 1.
The nozzle 60 is arranged so as to spray the air at zero. The tip 62 of the nozzle 6o may be a continuous opening, as shown in FIG. 2, or may be comprised of a plurality of spaced apart holes.

Air may be blown out continuously from the nozzle 60, or may be controlled so that it is blown out only when the paper passes through the nozzle 60.

Generally, in a device that conveys paper using a chain gripper, in order to improve transfer efficiency, the gripper passes very close to the photosensitive drum, and the gap between the leading edge of the paper and the photosensitive drum 10 is set to 0. It is necessary to narrow it to about 5 to 0.8 m. If this gap is wide, the image will be distorted during transfer unless the paper is forced along the photosensitive drum using a member such as the paper support plate as described above. However, providing a paper support plate on the upstream side of the transfer corotron in order to prevent this image disturbance has many drawbacks as described above, and therefore cannot be said to be a good method. Particularly in the case of color copying, in which a toner image is transferred multiple times onto a sheet of paper, the disadvantage that registration mismatch increases is fatal.

According to the transfer device of the present invention which employs the air blowing nozzle 60 as described above, such drawbacks can be greatly improved. However, in order to obtain good registration,
Even when the transfer device of the present invention is employed, it is desirable that the distance between the position where the paper passes and the photosensitive drum 10 be narrow.

In addition, in order to obtain good registration, the strength of the air flow blown from the air blowing nozzle 60 must be 2 (
It is desirable that it be in the range of about lf to 25 gf. Furthermore, by providing the chute 66 on the upstream side of the air blowing nozzle 60 in the paper conveyance direction, the effect of air pressure can be used more effectively.

In the embodiment described above, the air blowing nozzle 60 is constructed from a separate member from the transfer corotron 48, but the shield plate of the transfer corotron 48 and the air blowing nozzle 60 may be integrated. Furthermore, if the nozzle 60 is configured to be movable up and down, or the blowing pressure can be adjusted, the distance between the paper 22 and the photosensitive drum 10 can be appropriately controlled.

Effects of the Invention Since the present invention is configured as detailed above, it is possible to obtain good registration when transferring a toner image, and also to obtain a good transferred image without toner scattering. be effective. Furthermore, since the paper is guided along the surface of the photosensitive drum by the air blowing nozzle, there is also the effect that operation control can be simplified compared to conventional devices.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of the toner image transfer device of the present invention, FIG. 2 is a perspective view thereof, and FIG. 3 is a schematic configuration diagram of a copying machine having a conventional transfer device that uses a chain gripper as a paper conveying means. be.

Claims (2)

[Claims] (1) In a copying machine or printer transfer device configured to grip and convey the leading end of a sheet of paper with a chain gripper, and to transfer a toner image on a photosensitive drum onto the sheet of paper using a transfer corotron, the sheet is conveyed by the transfer corotron. A toner image transfer device characterized in that an air blowing nozzle is provided on the upstream side in the direction. (2) The transfer device according to claim 1, wherein the gripper bar of the chain gripper is provided with an inclination angle such that when the paper is gripped, the leading end of the paper is held slightly upward from the horizontal direction.