JPH0339770A - 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 according to copying conditions, wherein a blank is forcedly formed on transfer paper, the conditions of the transfer paper and the conditions of temperature. CONSTITUTION:When such a copying mode is set that a blank part is forcedly formed on the part of the transfer paper, moreover, the repulsive quantity, size and temperature/moisture of the transfer paper are considered, and the discharging currents of a transfer pole 7 and a separate hole 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 according to the conditions of the transfer paper and the temperature. 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 discharging current is switched to be a higher value, and a bias potential for converting the current into DC is switched to be a higher value. Thus, it is eliminated that a toner picture is changed and the picture quality is degraded and, at worst, that the transfer paper is wound around a photosensitive body and the paper jamming occurs.

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 blank on the transfer paper, the above problem is likely to occur, especially when the leading edge remains.

The above-mentioned tendency is more pronounced than when the transfer paper is fed with stiff vertical grain (A3, B4, A4R, B5R).
This is particularly noticeable when the transfer paper is fed with a weak cross-grain (A4, B5), and is also noticeable when the basis weight (thickness) of the transfer paper is small. Furthermore, if the temperature deviates from the predetermined range, the problem becomes more noticeable.

The present invention has been made in view of these points, and its purpose is to improve the basis weight, size, and temperature of the transfer paper 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 in which proper separation is performed in consideration of the above.

[Means to solve the problem]

To this end, 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 first means for detecting the amount of displacement and/or size of the transfer paper. The device comprises a second means, a third means for detecting the temperature, and a fourth means for switching the discharge current of the transfer electrode and/or the separation electrode based on the detection results of the first means to the third means. .

〔Example〕

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, 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 rod-shaped exposure light source 14 that travels in the direction indicated by the arrow on the lower surface of the platen glass l on which the document 2 is set and exposes the document 2, emits the reflected image light obtained by exposure to the photoreceptor. 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 charge on the light irradiated portion of the photoreceptor, which has been previously charged at a high voltage by the charging electrode 4, decreases in accordance with the degree of brightness, and the original is placed there. An electrostatic latent image corresponding to the image is formed. 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 on which the toner image is cut 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 the copy mode that forcibly creates a blank area on a part of the transfer paper is set as described above, the basis weight, size, and temperature/humidity of the transfer paper are further taken into consideration. The discharge currents of the transfer electrode 7 and the separation electrode 8 are switched from normal values to other values.

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 a DC-biased AC voltage so that the sum of positive and negative discharge amounts has the opposite polarity to the charge applied by the transfer pole. (For example, Special Publication 53-174
(See Japanese Patent Laid-Open No. 93838/1983).

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.

Taking these points into consideration, this embodiment switches the transfer current and separation current according to the conditions of the transfer paper and the humidity/temperature when a copy mode that forcefully leaves a blank area is selected. I did it like that.

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
22 is a paper size detection unit that detects the paper size of transfer paper;
2 is a transfer paper basis weight detection section, 23 is a temperature detection section, 24 is a humidity detection section, and 25 is a control section consisting of a microcomputer, etc., 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. 25.

As the paper size detection section 21 described above, a transfer paper size detection section provided in a transfer paper cassette can be used. The basis weight detection unit 22 also detects that the transfer paper is in the paper feed unit 10.
It is possible to use a system in which a light transmission sensor is disposed on the way from the registration roller 11 to the registration roller 11, and the amount of light transmitted by the light transmission sensor is detected. Further, the temperature detection section 23 and the humidity detection section 24 are installed in the path or near the cassette so that the temperature and humidity of the transfer paper can be detected.

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 erasing outside the specified area, erasing within the specified area, frame erasing, and reduction shift is selected in the operation unit 20 described above and the command is taken into the control unit 25, the transfer paper is Assuming that a copying condition that easily causes 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 set to a second value different from the first value (normal value). Can be switched. The second value is, for example, a value that is 15% lower than the normal value for the transfer current, and a value that is 15% higher than the normal value for the separation current.

However, at this time, it is detected that the basis weight of the transfer paper is small (thin, for example, 55 g/m" or less), or the paper size is A4.
Alternatively, if B5 is detected, the transfer current of the transfer pole 7 and the separation current of the separation electrode 8 are switched to the third value. The third value is, for example, a value that is 18% lower than the normal value for the transfer current, and a value that is 18% higher than the normal value for the separation current.

Furthermore, at this time, in addition to the above-mentioned copying conditions being satisfied and the above-mentioned transfer paper conditions being satisfied, the temperature exceeds 33°C and the humidity exceeds 80%.
If the temperature exceeds 10°C or less and the humidity is less than 20%, the transfer paper becomes stiff and is easily charged with static electricity, so the transfer current of the transfer pole 7 and the separation pole The separation current of 8 is switched to a fourth value. For example, the fourth value may be 22% higher than the normal value for the transfer current.
0% down value, and 20% for separation current
The increased value.

In this way, the copying conditions are met, the transfer paper conditions are met, and the humidity/
Depending on the establishment of atmospheric conditions such as temperature, the transfer current is controlled to be lower and the separation current is controlled to be higher, so deterioration of separation performance can be effectively prevented, and at the same time, image quality deterioration can also be prevented. I can do it.

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.

In addition, 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 it is also possible to switch only one of them. By setting , it is possible to perform control such that one of the transfer current and separation current is switched, and in addition to the above switching, the other is switched when the transfer paper conditions are such that poor separation is likely to occur.

Furthermore, regarding the conditions of the transfer paper itself, there are three combinations of basis weight and size that result in poor separation, and the transfer current and separation current can be controlled to be finely switched depending on the combination.

Furthermore, although the atmospheric conditions are detected using both humidity and temperature conditions in the above description, the atmospheric conditions can also be determined based only on the temperature conditions.

〔Effect of the invention〕

As explained above, according to the present invention, the transfer current and separation current are automatically switched according to the copying conditions for forcibly creating a blank on the transfer paper, the transfer paper conditions, and the temperature conditions. This has the advantage of being able to prevent image quality deterioration and paper jams due to poor separation.

[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.

Claims (2)

[Claims] (1) A first means for detecting that copying conditions have been set to forcefully leave a blank area on the transfer paper, a second means for detecting the amount and/or size of the transfer paper, and a second means for detecting the temperature. and a fourth means for switching the discharge current of the transfer pole and/or the separation pole based on the detection results of the first to third 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.