JPH0368965A - Both-surface image producing device - Google Patents

Abstract

PURPOSE:To remove the positional deviation between images on both surfaces and to form the image at a higher speed than that of a conventional device by arranging a pair of photosensitive bodies for a surface and a back surface so that they may be opposed and forming a vertical transfer paper conveyance path. CONSTITUTION:A pair of photosensitive bodies 10 and 11 for the surface and the back surface which have the same diameter are closely arranged to be opposed and a pair of transfer chargers 15 and 21 are provided. A resist roller pair 24 and a pair of fixing rollers 25 and 26 are arranged to be opposed above and below the photosensitive bodies 10 and 11 respectively. A surface transfer part (b), a back surface transfer part (d) and the paper nipping part (f) of a pair of fixing rollers form the vertical transfer paper conveyance path along the same perpendicular. The image is formed on both surfaces while a transfer paper 50 is vertically conveyed by gravity and the rotating force of the photosensitive bodies 10 and 11 which rotate in a reverse direction to each other, so that the image is formed at a high speed without causing the positional deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a double-sided image creating apparatus such as a digital copying machine, a page printer, and a page facsimile capable of creating images on both the front and back sides.

As conventional double-sided image forming apparatuses, the following (2) to (3) are known, but each of them has the following drawbacks.

■ Using one photoreceptor, after transferring and developing the front side, the transfer paper is reversed and conveyed to the same photoreceptor again, and the back side is transferred and developed (for example, see Japanese Patent Application Laid-Open No. 14250/1983); In this case, since the transfer paper is turned in a loop and reversed, it takes a long time to form an image.

(2) Two photoreceptors are arranged at a distance in the horizontal direction, and a transfer paper reversing mechanism is provided between them (see, for example, Japanese Patent Laid-Open No. 60-98449). In this case, not only does the entire apparatus become larger, but also the image forming operation must be performed with a time difference between the front and back surfaces, which results in a long image forming time and a complicated transfer paper conveyance mechanism.

■ Two photoconductors are arranged vertically sandwiching the transfer paper's horizontal conveyance path at a distance, and a fixing device is installed correspondingly to each of these photoconductors. (for example, Japanese Patent Application Laid-Open No. 1983-1912)
(See Publication No. 81). In this case, since a fixing device is installed correspondingly to each of the two photoreceptors, the apparatus becomes large.

■ Two photoconductors are arranged vertically facing each other, and transfer paper is sandwiched between them to transfer both the front and back sides at the same time (for example, see Japanese Patent Application Laid-Open No. 63-63057). In this case, there is no transfer deviation on both sides, and high-speed transfer is possible. However, variations in transfer performance due to differences in the thickness of the transfer paper cannot be avoided.

Problem W to be solved by Ming The problem of the present invention is to solve the above-mentioned drawbacks of the conventional technology, to achieve a simple structure and miniaturization, to have good transfer performance, no positional deviation between the front and back sides, and to be able to print double-sided images at high speed. The goal is to be able to create

The double-sided image forming apparatus according to the present invention includes a pair of photoconductors of the same diameter for the front side and a back side that rotate in opposite directions, and a pair of transfer plates for the front side and the back side that correspond to these photoconductors, respectively. It is equipped with a charger.

Both photoreceptors are arranged close to each other and facing each other, and the surface transfer charger is arranged vertically apart between both photoreceptors. A pair of registration rollers are arranged above the photoconductors, and a pair of fixing rollers for the front side and the back side are disposed below between the photoconductors, facing each other so as to sandwich the transfer paper between the two photoconductors. The front side transfer section between the front side transfer charger, the back side transfer section between the back side photoconductor and the back side transfer charger, and the paper nipping section of the pair of fixing rollers are arranged along the same vertical line. Forms a vertical transfer paper conveyance path.

The raw transfer paper is conveyed vertically downward by its own weight and the rotational force of a pair of photoreceptors of the same diameter that rotate in opposite directions, and is transferred onto both sides by a pair of transfer chargers corresponding to each of these photoreceptors. After the images are simultaneously transferred and separated by one, the images are conveyed vertically between a pair of fixing rollers and fixed on both sides at the same time.

Futoshi Futari Next, one embodiment of the present invention will be described in detail with reference to one drawing.

In the figure, a pair of photoreceptors 10 and 11 for the front surface and the back surface are shown.
have the same diameter, and are rotated in opposite directions by a common motor (not shown), that is, the front photoreceptor 10 is rotated counterclockwise, and the back photoreceptor 11 is rotated clockwise. Both of these photoreceptors 10 and 11 are disposed close to each other and facing each other with the front surface facing upward and the back surface facing downward, with a slight vertical shift.

A charging charger 12, a driver 13 for writing an image, a developing unit 14, a transfer charger 15, a separation charger 16, and a cleaning unit 17 are sequentially arranged around the front photoreceptor 10 in the rotation direction thereof. An image is written on the photoreceptor 10 by the driver 13 at point a,
The image is transferred to the transfer paper 50 by the transfer charger 15 at point b.
transferred to the surface of The transfer charger 15 and the separation charger 16 are arranged vertically in parallel, and the transfer paper 50, on which the image has been transferred to the surface by electrostatically adhering to the surface photoreceptor 10 at point b, is immediately removed from the photoreceptor 1o. separated.

Similarly, a charger 1 is placed around the back side photoreceptor 11.
8. Driver 19. Developing unit 20° transfer charger 21, separation charger 22, cleaning unit 23
are arranged sequentially. An image is written on the photoreceptor 11 by the driver 13 at point 0, and the image is transferred to the back surface of the transfer paper 50 by the transfer charger 21 at point d. A transfer charger 21 and a separation charger 22 are also arranged vertically in parallel, and the transfer paper 5o, on which the image has been transferred to the back side by electrostatically adhering to the backside photoreceptor 11 at point d, is immediately separated from the photoreceptor 11. be done.

A common pair of registration rollers 24 is arranged above between both photoreceptors 10 and 11, and below a pair of fixing rollers 25 and 26 for the front and back surfaces are arranged so as to be in contact with each other at the same height. ing.

Transfer/separation charger 15/16 for front side and transfer/separate charger for back side
The separate chargers 21 and 22 are located between the photoconductors 10 and 11, and are equidistant from the midpoint e between the centers of the defining photoconductors 10 and 11, and are located between the front photoconductors 10 and 10 at point b. The tangent line to the back photoreceptor 11 at point d, and the contact point f of the re-fixing rollers 25 and 26 are on the same vertical line.

Therefore, the transfer paper 50 moves from point b (front side transfer portion) to point d (back side transfer portion) due to its own weight and the rotational force of the pair of photoreceptors 10 and 11 having the same diameter that rotate in opposite directions. Further, it is conveyed straight and vertically to point f (paper nipping section).

In addition, the pair of registration rollers 2 for the defining light bodies 10 and 11
At the position 4, even when the long side of at least A4 size transfer paper is set as the traveling direction, the transfer paper
The position of the double-chamber landing rollers 25 and 26, where the rear end (upper end) of the transfer paper is away from the pair of registration rollers 24 while in contact with both of the transfer paper and the transfer paper of the above size, While in contact with both bodies 10 and 11, the leading edge (lower end) of the transfer paper is at a distance between the re-fixing rollers 25 and 26. As a result, the transfer paper 50 can be vertically conveyed at a constant speed without the need to provide a separate conveyance roller between the registration roller pair 24 and the fixing rollers 25 and 26.

A paper feed guide plate 27 is arranged above the registration roller pair 24 to guide the transfer paper 50 fed from the paper feed section to the registration roller pair 24, and above the fixing rollers 25 and 26, the transfer paper 50 is guided to the registration roller pair 24. Guide plates 28 and 29 on both sides are arranged to prevent the fixing roller 50 from jamming without entering between the fixing rollers 25 and 26. In addition, these guide plates 2
The distance between 8 and 29 is smaller than the distance between the centers of refixing rollers 25 and 26. Further, below the fixing rollers 25 and 26, a paper discharge guide plate 30 is disposed that guides the transfer paper 50 after fixing to the paper discharge section, and further below that, a paper discharge guide plate 30 is arranged which generates a downward airflow to move the fixing roller 25. - A fan 31 is arranged to flow the heat from 26 downward. fan like this 3
1 prevents the heat of the fixing rollers 25 and 26 from affecting the photoreceptor 10-11, and also prevents the transfer paper 5 from being affected by the heat of the fixing rollers 25 and 26.
The downward conveyance of 0 can be encouraged.

In the above configuration, among the continuously sent image signals, the image signal of the first front side (previous page) is stored in the memory, and this is synchronized with the image signal of the next back side (next page). If the image signals of both the front and back sides are simultaneously inputted in parallel to the respective drivers 13 and 19, the photoreceptors 10 and 11 on both the front and back sides can be exposed simultaneously. Then, the images can be transferred to the front and back sides of the transfer paper 50, respectively.

In this case, if the exposure position a''c and the transfer positions b and d on the front and back sides are set in the following relationship, images exposed simultaneously on the front and back sides can be transferred to the same position on the front and back sides without any image formation deviation.

(Rotation distance M of arc ab in front photoreceptor 10)+
(Distance between the transfer position point and point d on the transfer paper transport path)
= (rotation distance of circular arc cd on back side photoconductor 11) The transfer paper 50 is transferred continuously on both sides in this way, but the transfer paper 50 is in close contact with the front and back photoconductors 10 and 11 with a slight shift in position. Since the front and back sides are transferred separately, the negative toner adhering to the transfer paper 50, which is charged to a positive transfer rate, is transferred from the front with a positive transfer charger 15 across a space.
- Even if the toner is pulled by 21, the adhesion between the transfer paper 50 and the toner, which are in close contact with each other and are strongly electrostatically adsorbed, cannot be broken, so continuous transfer (high-speed transfer) between front and back sides can be performed without disturbance of one image.

The transfer paper 50, on which images have been transferred on both the front and back sides, has a vertical conveyance path and is immediately separated from the photoreceptors 10 and 11 by the separation chargers 16 and 22 after each transfer on the front and back sides. Due to the rotation of -11 and the weight of the transfer paper 50, after being separated from the back photoreceptor 11, it enters smoothly and straight between the re-fixing rollers 25 and 26 without touching anything. The image is then fixed simultaneously on both sides while being sandwiched between these fixing rollers 25 and 26 and conveyed downward.

If there is a fixing section for the front and back sides between the front and back photoconductors as in the past, the transport distance from transfer to fixing becomes longer, which means that image signals for both the front and back sides need to be input continuously, and both sides can be exposed at the same time.
Although duplex transfer is difficult, the arrangement shown in the figure makes it possible as described above, which speeds up the process from exposure to fixing.

Note that the image signal on the back side is also stored in the memory, and is read out simultaneously with the image signal on the front side to each driver 13.
19 and expose both the front and back sides at the same time. Furthermore, if the front and back image signals are input in parallel to the respective drivers 13 and 19 at the same time, the memory can be omitted. In this case, an analog copying machine will suffice.

As explained above, according to the present invention, it is possible to create double-sided images faster than conventional methods without positional deviation between the images on the front and back sides.
Moreover, not only is the mechanism simple and compact, but also good image quality can be obtained on both the front and back sides.

[Brief explanation of drawings]

The drawings are configuration diagrams of one embodiment of the present invention. 10...... Photoconductor for front side 11... Photoconductor for back side 15... Transfer charger for front side 21...
・・・・・・Reverse side transfer charger 24・・・・・・
...Registration roller pair 25...Fixing roller 26 for front surface...Fixing roller b for back surface
......Surface transfer part d...
・・・・・・Back side transfer part f ・・・・・・・・・Paper holding part

Claims (1)

[Claims] It is equipped with a pair of photoconductors of the same diameter for the front and back surfaces that rotate in opposite directions, and a pair of transfer chargers for the front and back surfaces that correspond to these photoconductors, respectively, with both photoconductors facing each other in close proximity. The transfer chargers are placed vertically apart between the photoconductors, a pair of registration rollers is placed above between the photoconductors, and a pair of fixing rollers for the front side and the back side are placed below between the photoconductors. They are placed facing each other with the transfer paper in between,
The front side transfer section between the front side photoconductor and the front side transfer charger, the back side transfer section between the back side photoconductor and the back side transfer charger, and the paper nipping section of the pair of fixing rollers are aligned on the same vertical line. A double-sided image creation device characterized in that the paper is lined up along the lines to form a vertical transfer paper conveyance path.