JPH0339767A - Electrostatic copying device - Google Patents

Abstract

PURPOSE:To prevent degradation in picture quality and paper jamming caused by the defect of separation by automatically switching a transfer current and a separation current at the time of setting copying conditions wherein a blank is forcedly formed in transfer paper. CONSTITUTION:When such a copying mode is set that a blank part is forcedly formed on a part of the transfer paper, the discharging currents of a transfer pole 7 and a separation pole 8 are switched to other values from normal values. Namely, when the copying mode wherein the blank part is forcedly left is selected, the transfer current and the separation current are switched. In order to improve separation capability, a voltage impressed on the transfer pole 7 is switched to be lower, namely, the transfer current is switched to be a lower value. In order to improve the separation efficiency more, the value of this AC voltage discharge current is switched to be a higher value, and/or a bias potential for converting the current into DC is switched to be a higher value. Thus, even on the copying conditions that the blank part is left in a part of the transfer paper, appropriate separation can be carried out.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention improves transfer separation performance in an electrostatic copying device that can set special copying modes such as masking, trimming, frame erasing, or reduction shift copying. The present invention relates to an electrostatographic copying apparatus.

[Conventional technology]

2. Description of the Related Art Conventionally, there have been copying apparatuses that have a function of copying only a portion of a document, for example. As shown in FIG. 4, this method specifies the area 2a of the original 2 placed on the platen glass 1 by, for example, specifying coordinates, and copies only the area 2a within the specified area (erasing outside the specified area). (see, for example, Japanese Patent Laid-Open No. 60-213168).

[Problem to be solved by the invention]

However, this outside designated area erasing function uses a charged erasing lamp to expose and erase charges on the surface of the photoreceptor, excluding the area corresponding to the designated area 2a of the original 2 described above, to prevent toner from adhering. Therefore, when transferring the toner image to the transfer paper after development,
The adhesion between the transfer paper and the toner-free portion of the photoreceptor becomes stronger. As a result, separation is not performed completely in the subsequent separation step, resulting in changes in the toner image and deterioration of image quality, or in the worst case scenario, the transfer paper wraps around the photoreceptor, causing a paper jam.

Such an abnormal situation may also occur during designated area erasure (masking), which reversely erases the designated area 2a of the original document 2, and may also occur when erasing the frame portion, shift copying, binding margin copying, and reduction shift copying. It can also occur in some cases. In other words, when copying conditions are such that a relatively large area remains as a blank on the transfer paper, the above problem is likely to occur especially when the leading edge remains.

The present invention has been made in view of these points, and its purpose is to enable proper separation even in the case of copying conditions where a blank area remains on a part of the transfer paper as described above. It is an object of the present invention to provide a copying apparatus that has the following features.

[Means to solve the problem]

For this purpose, the electrostatic copying apparatus of the present invention includes a first means for detecting that a copying condition that forcibly leaves a blank area on the transfer paper is set, and a transfer pole and/or
Also, a second means for switching the discharge current of the separation electrode is provided.

Example C] Examples of the present invention will be described below. FIG. 3 is a diagram schematically showing the copying apparatus. In the electrostatic recording section A, a charged electrode 4,
Charge erasing lamp 5, developing device 6 with transfer pole 7, separation pole 8,
and a cleaning device 9 are arranged in sequence. Further, upstream of the transfer pole 7, a registration roller 11 is provided that temporarily stops the transfer paper fed from the paper feed section 10 to adjust the timing, and further downstream of the separation pole 8, a conveyor belt 12 and a heat fixing Devices 13 are provided one after the other.

On the other hand, in the document reading section B, a bar-shaped exposure light source 14 that travels in the direction indicated by the arrow on the lower surface of the platen glass 1 on which the document 2 is set and exposes the document 2, and a photoreceptor that emits the reflected image light obtained by exposure. Mirrors 15 to 18, a lens 19, and the like are provided for transmitting information to the 3.

In this copying apparatus, an original 2 on a platen glass 1 is exposed by scanning an exposure light source 14 in the direction of the arrow. When the image light obtained by this exposure is incident on the photoreceptor 3, the electric charge on the light irradiated portion of the photoreceptor, which had been previously charged at high voltage by the charging electrode 4, decreases in accordance with the degree of brightness. An electrostatic latent image is formed according to the image of the original. and,
As the photoreceptor 3 rotates, this electrostatic latent image portion is transferred to the developing device 6.
When the image reaches the sleeve 6a, it is developed there with toner, forming a toner image corresponding to the image of the document. Then, this toner image is transferred from the registration roller 12 to a transfer sheet fed at a timing when the leading edge of the image coincides with each other at a transfer pole 7, and further reaches a separation pole 8 where it is separated from the surface of the photoreceptor 1. and,
The transfer paper carrying the toner image is then transferred to the conveyor belt 12.
The sheet is then sent to the thermal fixing device 13, where it is thermally fixed, and the sheet is discharged. The photoconductor 3 on which toner remains is cleaned by the blade 9a when it reaches the cleaning device 9, and is prepared for the next cycle.

When copying only the specified area 2a of the document 2 described above, information corresponding to the specified area is transmitted to the charge erasing lamp 5, and the plurality of L's constituting the charge erasing lamp 5 are
By lighting a predetermined one of the EDs at a predetermined timing, the designated area 2 of the document 2 on the photoreceptor 3 is
Charges outside the region corresponding to a are erased. As a result, the adhesion of the transfer paper to the erased portion increases, and the separation performance deteriorates as described above.

Therefore, in this embodiment, when a copy mode is set in which a blank area is forcibly created in a part of the transfer paper as described above, the discharge current of the transfer pole 7 and the separation pole 8 is changed from the normal value. Changed to switch to another value.

At the transfer pole 7, a voltage with a polarity opposite to that of the toner adhering to the surface of the photoreceptor 3 is applied to the transfer paper.
The toner is transferred to the transfer paper side by electrostatic force (
For example, see Japanese Patent Publication No. 53-17495). Therefore, a voltage with the same polarity as the charging polarity of the surface of the photoreceptor 3 is applied to the transfer paper, but in order to transfer the toner from the photoreceptor 3, a voltage higher than the charging voltage of the photoreceptor 3 is applied. applied.

Therefore, the electric charge caused by this remains on the transfer paper and the separation pole 8
Therefore, in order to improve the separation performance, the voltage applied to the transfer pole 7 should be lowered, that is, the transfer current should be switched to a smaller value.

On the other hand, regarding the separation pole 8, there is a method of applying a charge of the opposite polarity to the charge applied by the transfer pole described above.
Since the permissible range of this voltage is narrow, it is now common to apply an AC voltage biased to DC so that the sum of 1 ft of positive and negative radiation has the opposite polarity to the charge applied by the transfer pole. (For example, Special Publick
495, JP-A No. 53-93838).

Therefore, in order to further increase the separation efficiency, the value of this AC voltage discharge current may be changed to a high value, and/or the bias potential for biasing the DC current may be changed to a high value.

In this embodiment, in consideration of this point, the transfer current and the separation current are switched when a copy mode in which a blank area is forcibly left is selected.

FIG. 1 is a diagram showing this control system. 20 is an operation unit for setting various copy modes, number of copies, density, etc., 21
Reference numeral 21 denotes a control section composed of a microcomputer or the like, and the transfer current setting of the transfer pole 7 and the separation current setting of the separation pole 8 are controlled by this control section 21 .

FIG. 2 is a diagram showing a flowchart of a control program for setting and switching the transfer current and separation current described above. Here, when one of the modes of erase outside the specified area, erase within the specified area, frame erase, and reduction shift is selected in the operation unit 20 described above and the command is taken into the control unit 21, the transfer paper is Assuming that a copying condition that tends to cause separation failure from the photoreceptor 3 is established, the transfer current of the transfer pole 7 and the separation current of the separation pole 8 are switched from normal values to other values. The other values are, for example, a value that is 20% lower than the normal value for the transfer current, and a value that is amplified by 20% for the separation current.

In the above, only the erase outside specified area, erase within specified area, frame erase, and reduction shift are shown as copy modes that forcibly create a blank area in a part of the transfer paper, but there are other copy modes such as shift copy and binding. There are other types such as substitute copies.

Further, although an example in which both the transfer current and the separation current are switched at the same time has been described above, the present invention is not limited to this, and only one of them may be used.

C. Effects of the Invention As explained above, according to the present invention, the transfer current and separation current are automatically switched when setting the copying conditions to forcibly create a blank space on the transfer paper, so image quality deterioration due to separation defects is prevented. This has the advantage of being able to prevent paper jams.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a control unit according to an embodiment of the present invention, FIG. 2 is a flowchart of its control program, FIG. 3 is a schematic configuration diagram of a copying machine, and FIG. 4 is an explanatory diagram of erasing outside a specified area. be. 5... Charge erasing lamp, 7... Transfer pole, 8... Separation pole. Figure 2 Figure 3

Claims (2)

[Claims] (1) a first means for detecting that a copying condition forcibly leaving a blank area on the transfer paper is set; and a discharge current of the transfer pole and/or the separation pole is switched based on the detection result of the first means. An electrostatic copying apparatus comprising a second means. (2) The first means includes a designated area erase mode, a designated area erase mode, a frame erase mode, a shift copy mode,
2. The electrostatic copying apparatus according to claim 1, wherein the electrostatic copying apparatus detects the setting of a binding margin production mode or a reduction shift mode.