JPH06266247A - Electrophotographic copying device - Google Patents

Abstract

PURPOSE:To invariably copy a high-quality image by accurately correcting the transfer current without causing impediments such as a transfer miss and a transfer cissing and without being limited by the thickness and quality of sheets so much in an electrophotographic copying device in the high-humidity high-temperature state. CONSTITUTION:An electrophotographic copying device is provided with a history memory means of the output value change from a humidity detecting means, a measurement memory means of the stack period of transfer sheets in a transfer sheet cassette, and a memory storing the memory value information and at least one of the parameter information such as the number, sequence, weight, and quality of the transfer sheets stacked in the cassette for each transfer sheet. The resistance value of each transfer sheet is calculated from the memory as the estimated value, and the corona discharge output of a charge unit is programmed to follow the optimum value. Each information is reset by either one of the signal from a means detecting that no transfer sheet exists in the cassette and the signal from a means judging whether the cassette stacked with the transfer sheets is left removed from the copying device for a prescribed period or longer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of output control of a charger, especially a transfer electrode of an electrophotographic copying machine.

[0002]

2. Description of the Related Art Generally, a copying machine of this type irradiates an original placed on a platen glass with light from a light-emitting lamp of a reading section, and the reflected light causes a photoreceptor (O) to be charged at a high voltage.
An electrostatic latent image is formed on a PC (organic photoconductor) drum or belt, and the electrostatic latent image is further developed in the developing section so that the toner image becomes visible. The transfer image is transferred onto the transfer sheet that enters in synchronism with the transfer sheet, the transfer sheet is separated from the surface of the photoconductor, and is conveyed to a fixing unit. The toner image is fixed and fixed on the transfer sheet by heat fusion and is collected.

However, when the copying machine is installed in a high humidity condition, the resistance value of the transfer paper changes due to moisture absorption, so that even if a constant high voltage current is applied to the transfer electrode, it is generated. Charges with a polarity different from that of the toner are not left on the transfer paper, and are transferred to the transfer paper and are leaked by being grounded. If the cleaner is emptied and erased, or if the high-voltage current is increased to compensate for it, the electric charge generated by the high-voltage current from the transfer electrode has a high water content and a low electrical resistance. The phenomenon of transfer repellency occurs in which the toner image on the paper starts to fluctuate, and the toner image on the photoconductor collapses and becomes blurred, and is transferred to the transfer paper.

In order to prevent and remove such a phenomenon, Japanese Patent Publication No. 53-57042 proposes a method of measuring the water content of transfer paper in a copying machine and feeding it back to a transfer pole power source. No. 28081 measures the resistance value of transfer paper,
A proposal has been made to change the transfer conditions by feeding back, and Japanese Patent Publication No. S58-152267 proposes a means for judging the high humidity condition to control the high voltage current of the strip electrode.

Further, in JP-A-53-115233, the amount of light, the amount of charge, the temperature and humidity, and the number of sheets are detected to correct the sensitivity of the photosensitive member.
No. 10274 uses a phage function to feed back various sensor information to the separation control, and in Japanese Patent Laid-Open No. 3-10275, the number of revolutions of the fixing roller that rotates during warm-up is controlled by phage inference. ing.

As described above, in the electrophotographic copying apparatus, various controls for maintaining the image quality are performed, but various physical quantities are corrected and the correction calculation becomes complicated, and when they are applied to transfer paper, they are measured one by one. As a result, the conditions are complicated and the control is difficult and unstable. However, in spite of such difficulty and instability, there is no idea in the prior art that the feedback of such information is given to the transfer current value.

[0007]

However, it is not preferable that the resistance value of the transfer paper is measured one by one as in the prior art, because the mechanism becomes large-scaled and the transfer paper is jammed.
Similarly, it is not preferable to measure the water content one by one.

There is also one that measures the humidity and feeds it back to the separation current, but after the humidity is measured, if the humidity is this humidity, the separation current will be determined as a uniform condition. If 20 or more sheets are continuously fed in high humidity, the excessive current causes the phenomenon of transfer repelling due to image quality as described above.

Further, it is desirable that the transfer paper information be provided with stable image quality control not only for those having a steady thickness and material but also for those having a thick thickness and different materials.

Further, unless the means for resetting and initializing these pieces of information are clarified, control by accurate information transmission becomes impossible.

The present invention solves such a problem and causes a transfer paper jam for measurement without causing transfer defects or transfer repellency even in a high humidity condition, and without increasing the size of the apparatus. It is an object of the present invention to provide an electrophotographic copying apparatus having a charge control means for transfer and the like that does not occur.

[0012]

This object is solved by the following technical means.

The recording medium has a history storing means for a change in output value from the humidity detecting means and a measuring storing means for measuring a leaving time of the transfer paper in the transfer paper cassette, and the storage value and the transfer paper stacked and stacked in the cassette. Has a memory for storing, for each transfer sheet, the number of sheets and the order of passing the sheets and at least one of parameter information such as the weight and material of the transfer sheet, and estimates the resistance value of each transfer sheet from the memory. The corona discharge output of the charger is programmed so as to follow the optimum value by calculating as a value, and the signal from the means for judging that the transfer paper is not in the cassette for resetting and initializing each of the above information. An electrophotographic duplication, characterized in that it is made by one of the signals from the means for judging whether or not the cassette on which the transfer sheets are stacked has been removed from the copying apparatus for a predetermined time or longer. Apparatus.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the overall configuration diagram of FIG. 1, the control circuit diagram of FIG. 2 and the relationship diagram of the command value and the transfer current to the photoconductor of FIG.

Exposure beam on charged photoconductor drum 60
The latent image exposed at 120 is first developed by the developing roller 41 of the developing device 40 to form a toner image, and a corona discharge is generated by the transfer pole 51 and the separation electrode 52 at the transfer position and the separation position, and every leaf is formed. It is transferred onto the transfer paper 14 that is fed from the paper feeding device 10 that feeds paper to the transfer position, and is conveyed to the fixing device 80.

The conveying speed of the transfer paper 14 and the peripheral speed of the photoconductor drum 60 are the same, so that the transfer paper 14 and the photoconductor drum 60 can accurately transfer the toner image without causing a relative displacement.

Transfer papers 14 are stacked and loaded in the cassettes 13A, 13B and 13C containing transfer papers of various sizes of the paper feeding device 10, and the stacked transfer papers 14 are pushed up by the push-up plate 11. Sending rollers 12A, 12B, 12C by action
, And one of the upper surface is sent out by the roller,
A conveyance guide member that is conveyed by the pair of conveyance rollers 21 and 22 and the pair of final-stage conveyance rollers 23 and 24, and that is further provided in the vicinity of the photosensitive drum 60 via a conveyance guide of a linear portion.
It reaches the end of 128 and synchronizes with the photosensitive drum 60, and receives the image transfer as described above.

The transfer paper 14 having received the image transfer is conveyed toward a fixing device 80 for further heat fixing, and is fixed there.
Recovered over 90.

Now, when such an electrophotographic copying apparatus is placed in a place where air conditioning is not well reached in a high temperature and high humidity area (for example, 33 ° C., 85% RH), this state and transfer paper When the water content changes and the resistance value changes accordingly, a transfer failure occurs, and when it is roughly corrected, a phenomenon such as a transfer drop or a transfer repelling that deteriorates the image quality appears. Further, in order to accurately maintain the information of the resistance value and to perform the calculation accurately, the reset and the initialization of the information must be clearly processed. In addition to the steady thickness and steady quality of the transfer paper, special ones with different thicknesses and different materials may be used, and in this case, the changes in the water content and the resistance value are naturally different. Make a move. The present invention controls the transfer current so that a stable high-quality image that does not cause such image quality deterioration can always be maintained for transfer paper of any thickness and of any paper quality. did.

Next, the control means used in the present invention will be described first in the case where a transfer paper having a constant thickness and paper quality is used.

A humidity sensor is provided near the paper feeding device 10 of the copying machine, and the history of changes in output value from the sensor is CP.
The transfer paper cassettes 13A, 13
A measurement value of a stacking time (leaving time) of each transfer sheet stacked on B and 13C and a transfer sheet number of the transfer sheets stacked and stacked on each cassette 13A, 13B and 13C. The sheet passing order is also stored in the calculating means of the CPU, the transfer current value table and the matching optimum command value are transmitted to the D / A converter 154 through the command value comparing means, and the converted value is input to the high voltage power supply 155. The transfer electrode 51 and the separation electrode 52 are applied so that the current value becomes an optimum value.

Here, how the command values are tabulated will be described.

When the humidity is set to a high humidity and the moisture absorption progresses under the condition, the transfer sheets stacked on the cassette are sequentially transferred from the first sheet to the 20th sheet from the top. The progress of the moisture absorption state is tabulated based on the experimental data by the table, which is shown in Table 1.

[0024]

[Table 1]

In this table, the order of the transfer sheets stacked on the cassette in the lateral direction is shown uniformly from the top to the 20th sheet and from the 20th sheet or more. Then, in the vertical direction, the command value and its correction value at the time of 5 minutes, 10 minutes from the initial (initialized) state are applied, and further 1 copy state, the mechanism of command value shift, 180 minutes or more Command value when it has passed and correction value at that time, further 9co
How the command value shifts in the situation after py,
Further, the command value of the state after a lapse of 5 minutes and its correction value are specifically described and tabulated.

The command values are 0, 5 and 10,
When 0, the transfer current value is not particularly corrected, but when it becomes 5, it is almost 10
It came to be corrected to a large μA, and when it reached 10, it was almost 2
This is a very remarkable current value correction of 0 μA.

In the correction stage in the middle, in the case of moisture absorption in a high humidity state as shown in the table above, the shift is made to the side of two data (between two lines) that is larger, but in the case of moisture release, that is, from the high humidity state. A similar separate table is created when shifting to a low humidity state, and the correction value is shifted to the smaller side of the two data.

As a result, a state that closely approximates the actual state is obtained. Here, it means that the moisture absorption state does not progress so quickly and becomes extremely unchanged when the number of sheets is 20 or more. However, as the use of transfer paper progresses, even the lower stacks will be affected by moisture absorption only after they rise to the 20th sheet or more. It can be said that it is sufficient for the table to be able to manage the moisture absorption behavior of up to 20 sheets of transfer paper.

On the other hand, there are three types of transfer paper, which are in a steady state with a water content of 8% or less, have a relatively high water content of 8% to 9%, and have a considerably high moisture content of 9% or more. Appropriate transfer current value and command value (L
The relationship between the SB value and the least significant bit value) is shown in Table 2.

[0030]

[Table 2]

As shown in the diagram of the relationship between the transfer current value for the photoconductor and the command value (LSB value) in FIG. 3, even if the water content of the transfer paper increases, the transfer current value 180 μA causes the command value to change to 5,
It becomes possible to change the transfer current value to 10 so that the transfer current value becomes the optimum current value for the water content of the transfer paper at that time.

The above is a model representation of a situation in which the transfer paper used has a constant thickness and a constant paper quality (material), and the water content and the resistance value accompanying it change.
On the other hand, it is necessary to correct the command value for transfer paper having a particular thickness and material.

That is, the water content and the resistance value R are the paper thickness t and the material c.
Is considered to be a function of, the relation of R = f (t, c) is established, and the resistance values of the stationary paper and the special paper are R ₁ ,
If R ₂ is set, the relationship of R ₂ / R ₁ = f ₂ (t ₂ , c ₂ ) / f ₁ (t ₁ , c ₁ ) occurs, so the command value is multiplied by this R ₂ / R ₁ to correct the command value. I was able to do.

If such physical property information of the transfer paper is stored in the CPU as shown in the circuit diagram of FIG. 2, the resistance value based on the input physical property data and the transfer current are stored without distinction between steady state and special state. The value is compared and corrected with respect to that of the steady transfer paper, and the command value that stably provides high image quality is corrected.

Therefore, the optimum transfer current value can always be obtained by the automatic correction by the command value correction regardless of the steady or special transfer paper.

The transfer sheet elapsed time information compared with the above-mentioned command value and its correction value table created by the order of transfer sheets stacked on the cassette and the passage of time shows that the transfer sheets in the transfer sheet cassette are lost. Reset or if the transfer paper is left in the cassette by mistake or if the cassette is accidentally removed from the copying machine for more than 30 seconds. Then, when these cassettes are set again with the transfer paper inserted, they are set to the initial state.

As a result, the transfer paper information is always accurately compared with the command value table (including the correction value), the correct water content, that is, the correct resistance value is estimated, the correct transfer current is output, and the transfer omission or transfer repellency is obtained. High-quality copying that does not occur can be stably continued.

[0038]

According to the present invention, the trouble of handling an electrophotographic copying machine in a high temperature and high humidity region is eliminated, and high quality copying can always be obtained. That is, the change status of the water content and the resistance value of the transfer paper loaded in the high humidity condition is determined as a temporal change based on the experimental result information about the steady state, each thickness of the special transfer paper, and the material. , A table is prepared so that it can correspond to the optimum transfer current value related by the position and order of the number of passed sheets, and at the time of copying, the humidity measurement data and each transfer sheet position information input each time are recorded in the table. In addition, it is calculated by the calculation means of the CPU that is also mounted, and it follows changes in the paper thickness and paper quality of the transfer paper, and when the transfer paper in the cassette runs out, or when the transfer paper is in the middle If it is removed from the copying machine, the position, order information, timer information, etc. of the transfer paper will not be set to the initial state unless it is reset and reloaded. Transfer current is supplied without error spots and transfer the transfer became soon no high-quality copying can be stably obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is a control circuit diagram of the present invention.

FIG. 3 is a relationship diagram of a command value and a transfer current value for a photoconductor.

[Explanation of symbols]

 10 Paper feeder 13A, 13B, 13C Cassette 14 Transfer paper 60 Photosensitive drum 51 Transfer pole 155 High voltage power supply

Claims (1)

[Claims] 1. A history storage unit for changing the output value from the humidity detection unit and a measurement storage unit for measuring the leaving time of the transfer paper in a transfer paper cassette, and the storage value information and the stacked storage in the cassette. Has a memory for storing, for each transfer sheet, the transfer sheet number and the sheet passing order information of the transfer sheet and at least one of parameter information such as the weight and material of the transfer sheet, and stores the resistance value of each transfer sheet. Means for determining that the corona discharge output of the charger is programmed so as to follow the optimum value by calculating as an estimated value from the memory, and resetting and initializing each information described above does not exist in the cassette. From the copying machine or a signal from a means for judging whether the cassette on which the transfer sheets are stacked has been removed from the copying machine for a predetermined time or more. Electrophotographic copying machine.