JPH0342475B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image control device that performs so-called continuous magnification black erasure control, and particularly to an image control device that performs so-called continuous magnification black erasure control, and in particular, to control the amount of blackout on a photosensitive drum when the magnification of a recorded image is continuously changed. The present invention relates to an image control device that prevents toner from adhering to an image area.

Conventional Technology and Problems to be Solved by the Invention Conventionally, in this type of copying machine, processing to prevent toner from adhering to non-image areas during stepwise magnification (black erasure processing) was performed in the direction of drum rotation. This could be done by various means that have already been proposed, but it was done by arranging small miniature lamps in a direction parallel to the drum axis and blinking the lamps according to the selected magnification. however,
In the case of continuous magnification, the lamp must be blinked continuously, which could not be achieved with a small lamp or the like. Also, LED (light emitting diode)
A method using a light-emitting element such as I couldn't use it without it. In addition, a method has been proposed in which a shielding object is placed in front of a light source that emits light uniformly, and this shielding object is moved continuously according to the magnification ratio to block the light from the light source. It is difficult to implement due to problems such as complexity.

[Means for Solving the Problems] In order to solve the above problems, the present invention projects an original image at a desired magnification onto a primarily charged photoreceptor, simultaneously charges the photoreceptor secondarily, and then In an image forming device that forms a latent image corresponding to an original image by exposing the body to light, a member that can press the original and form a latent image corresponding to a white image when the pressed surface is projected onto a photoreceptor. a manuscript cover having;
an exposure means provided along the width direction of the photoreceptor and having a variable exposure area for projecting an original image and exposing the photoreceptor after secondary charging; and an exposure means on which the original and the pressing surface of the original cover are projected onto the photoreceptor. and a control means for controlling the exposure of only the area by the exposure means.

[Function] With the above configuration, the present invention can prevent toner from adhering to non-image areas during variable magnification copying with a simple configuration,
This makes it possible to obtain very good-looking copies with little toner staining.

Furthermore, by effectively using means for exposing the photoreceptor,
The present invention is intended to save power and reduce heat generation, and to have a simple and inexpensive configuration.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1A shows a schematic configuration example of the main parts of an NP process type copying machine to which the present invention is applied. A drum-shaped photoreceptor 1 is uniformly charged by a charger 2.
Thereafter, a latent image is formed on the photoreceptor 1 by irradiating reflected light from an original (not shown) while being charged to the opposite polarity by the charger 13, and then the entire surface of the LED array 4 is exposed to a potential that can be developed. I can do it.
The above process is as shown in Figure 1B,
Since this is a well-known theory, detailed explanation thereof will be omitted. The latent image is eventually developed by the developing device 5. On the other hand, the copy paper (recording paper) 8 is conveyed along the conveyance path 9 under conveyance control so that the developed image coincides with the transfer position, and after being transferred by the transfer charger 6, it is transferred to the charger 7. The static electricity is removed and the film is peeled off.
The LED array 4 is a light emitting element for blacking out a non-image area, which will be described later.

FIG. 2 shows an example of the structure of the document table portion of the copying machine shown in FIG. First, a document 11 to be copied is placed on the document placement glass 12 with one side as a reference, and the pressure plate 10 is lowered. The back surface of this document pressure plate 10 is entirely white. When copying is performed at a magnification ratio M in this state, the image of the original 11 whose length L is magnified to a length M×L and exposed to light, as shown in FIGS. 3A and B. A latent image is formed on the drum 1.

The latent image area of the original on the photosensitive drum 1 is indicated by L'. At this time, the document pressure plate 10 is longer than the document by l, and is provided so that a white back surface portion of length l remains, so that it is placed adjacent to the edge of area L' and has a length of M×l. white latent image area with dimensions corresponding to
l' is formed on the photosensitive drum 1. 1a shows a latent image formed on the photosensitive drum 1, and a shaded area 1b in the figure shows a dark latent image formed on the photosensitive drum 1. Further, in the figures, arrows indicate the axial direction of the drum. Here, if the magnification is changed continuously when there is no white latent image L' formed by the document pressure plate 10, the boundary line between the dark latent image 1b and the latent image L' of the document will change continuously, so that it will not be erased. This means that it is necessary to continuously irradiate the dark areas with light.
However, in this example, a white latent image area l' is made to exist when changing the magnification, so L' is the area that must be illuminated with light, and l' may or may not be illuminated. Since the shaded area 1b in the figure is an area where light should not be irradiated, the light emitted by the LED array 4 arranged at a pitch D that is smaller or equal to l' (see Figure 5) is If you irradiate appropriately depending on the situation, at least the shaded area 1
It is possible to ensure that the area b is not irradiated and the area L' is certainly irradiated.

As a result, as shown in Figure 1B, even though a latent image is formed in both bright and dark areas where the entire surface is not exposed, the potential is either the potential that should be developed or the potential that is not developed. As such, it does not appear on the surface of the drum 1. That is, in areas where the entire surface is not exposed, the potential of the dark area 1b is the same as the potential of the bright area 1a in that it is not developed.

4A and 4B show a schematic configuration example of the light control circuit of the copying machine shown in FIG. 1. FIG. Each element 4a, 4b... of the LED array 4 is a digit line D ₁ to D _o
and scan lines S ₁ , S ₂ . . . are connected as matrix intersections, and the LED elements selected based on the magnification ratio are dynamically lit by the dynamic lighting circuit 20.

FIG. 5 shows the relationship between the magnification ratio and the operation of the elements of the LED array 4 in FIG.
The lighting of each element of the LED array 4 is controlled so that at least the entire area on the right side of the figure is not irradiated from this area S, and at least the entire area on the left side of the figure is irradiated from this area S. Lighting is controlled so as not to damage the image.

As explained above, according to the embodiment, a white latent image is created in the non-image area due to continuous magnification change, so there is no need to consume excess toner even with continuous magnification change. This has the effect of producing clean copies because toner does not stick to it. Furthermore, according to the present invention, the LED array can be used effectively, resulting in lower power consumption and lower heat generation, resulting in lower cost and higher reliability of the device. Also, as in this example,
If a so-called dynamic lighting method is applied to drive the LED array, the drive circuit becomes simpler, further reducing power consumption and generating less heat.

In this embodiment, the case where the reference is on one side is shown, but it goes without saying that a case where the reference is in the center is also suitable. Further, although this embodiment shows a control means using an LED array, similar effects can be obtained even when an LCD shutter array is used. Further, in this embodiment, the area that may or may not be irradiated with light is formed by the document pressure plate, but it may also be formed by sliding a plate with a white back side in accordance with the edge of the document.

[Effects] As described above, according to the present invention, by exposing only the area on the photoreceptor onto which the original and the pressing surface of the original cover are projected, toner is not applied to the non-image area during variable magnification copying. Adhesion can be prevented with a simple configuration, and copies with very good appearance and less toner stain can be obtained.

Furthermore, by effectively using means for exposing the photoreceptor,
It is possible to save power and reduce heat generation, and to have a simple and inexpensive configuration.

[Brief explanation of drawings]

1A and 1B are schematic explanatory diagrams showing an example of the internal configuration of a copying machine to which the present invention is applied, and diagrams showing the process, and FIG. The front view shown in Figure 3 A and B is the second
4A and 4B are a front view and a plan view of essential parts showing the relationship between the original document and the latent image on the photosensitive drum shown in FIG. The enlarged view, FIG. 5, is an explanatory diagram showing the relationship between the LED array of FIG. 4 and the magnification ratio. 1... Photosensitive drum (photosensitive body), 2... Charger,
3...Reflected light, 4...LED array, 4a, 4b,
4c~...Each element of the LED array, 5...
Developing device, 6... Transfer charger, 7... Charger, 8...
... Copy paper (recording paper), 9 ... Conveyance path, 10 ...
Original pressure plate, 11...Original, 12...Original placement glass, 13...Charger, 20...Dynamic lighting circuit, _D1 ~ _D2 ...Digital line, _S1 , _S2 ~
...Scan line, M...Magnification ratio, L...Length of the document, L'...Latent image area of the document, l...Remaining length of the back side of the document, l'...White latent image caused by the document pressure plate region.

Claims (1)

[Claims] 1. Projecting an original image at a desired magnification onto a primarily charged photoreceptor, and simultaneously charging the photoreceptor secondarily;
Then, in an image forming device that forms a latent image corresponding to the original image by exposing the photoconductor, when the document is pressed and this pressed surface is projected onto the photoconductor, a latent image corresponding to the white image can be formed. an exposure means that is provided along the width direction of the photoconductor and whose exposure area is variable and that projects the document image and exposes the photoconductor after secondary charging; and a press of the document and the document cover. 1. An image control device comprising: control means for controlling exposure of only the region on the photoreceptor onto which the surface is projected by the exposure means.