JPH06266246A - 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 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 mechanism changing the control based on the memory value and the number and sequence of the transfer sheets stacked in the cassette. The change of the moisture content of the transfer sheets with the lapse of time while they are stacked in the cassette is stored as the exponential function, and the corona discharge output of a charge unit is programmed to follow the optimum value according to the exponential function. The time constant is changed at the time of moisture absorption and at the time of moisture desorption to cope with the control. The last humidity measured data are stored when a power source is turned off, the data are compared with the humidity measured data when the power source is again turn on, and moisture absorption and moisture desorption are automatically selected.

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.

[0005]

However, it is not preferable that the resistance value of the transfer paper is measured one by one because the mechanism becomes large 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. However, after measuring the humidity, the humidity is uniformly determined as the separation current, and attention should be paid to the stacking position of the paper. Not paid,
If 20 or more sheets are continuously passed in high humidity, the current will be excessive and the problem of transfer repelling will occur in terms of image quality as described above.

The present invention solves such a problem and causes the transfer paper to be jammed for measurement without causing transfer defects or transfer repelling 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.

[0008]

This object is solved by any one of the following technical means a, b and c.

(A) It has a history storage means for the output value change from the humidity detection means and a measurement storage means for measuring the leaving time of the transfer paper in the transfer paper cassette, and the storage value and the stack are stacked and stacked in the cassette. The charging device has a configuration in which the control is changed depending on the number of passing transfer sheets and the order of passing sheets, and the time change of the water content of the transfer sheet while being left in the cassette is stored in the calculating means as an exponential function, and the charger is used. An electrophotographic copying apparatus characterized in that the corona discharge output of is programmed so as to follow the optimum value by the exponential function.

(B) It has a history storage means of the output value change from the humidity detection means and a measurement storage means of the leaving time of the transfer paper in the transfer paper cassette, and is stacked and stacked in the storage value and the cassette. It has a configuration that changes the control depending on the number of sheets of transfer paper and the order of paper passage, and the change over time in the water content of the transfer paper while being left in the cassette is stored as an exponential function in the calculation means and when moisture is absorbed. And an electrophotographic copying apparatus characterized in that the time constant is made different at the time of moisture release so that the corona discharge output of the charger follows the optimum value by the selected exponential function.

(C) In item (b), the last humidity measurement data is stored when the power is off, and it is again compared with the humidity measurement data when the power is on to determine whether moisture absorption or desorption, and an exponential function to be applied is selected. An electrophotographic copying machine characterized by:

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are shown in FIG. 1 as a whole configuration diagram, FIG. 2 as a control circuit diagram, as shown in FIG. A description will be given using the relational diagram showing the temporal change of No. 1 and that when moisture is released in 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.

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

Transfer papers 14 are stacked and loaded in the cassettes 13A, 13B and 13C of the paper feeding device 10 which accommodate transfer papers of various sizes, 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 which has 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 the 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. In the present invention, the transfer current is controlled so that a stable high-quality image in which such a phenomenon does not occur can always be maintained.

Next, the control means used in the present invention will be described.

A humidity sensor is provided near the sheet feeding device 10 of the copying machine, and the history of changes in the 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 that condition, the transfer sheets stacked on the cassette are sequentially transferred from the first to the 20th sheet from the top, and the time elapses after the initialization. The progress of the moisture absorption state is tabulated based on the experimental data by the table, which is shown in Table 1.

[0022]

[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, when moisture is absorbed in a high humidity condition as shown in the table above, the data shifts to the larger side of the two data (between two lines), but in the case of moisture discharge, that is, from the high humidity condition. 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 slightly 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.

[0028]

[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 command value becomes 5 from the transfer current value of 180 μA.
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.

As described above, the water content of the transfer paper is measured in the copying machine when the humidity is measured in the copying machine and when the transfer paper is loaded in the cassette and mounted in the paper feeding section of the copying machine. It was confirmed experimentally and accurately by the position and the order and by the standing time, and it was confirmed that the relationship between the water content and the transfer current is expressed as shown in Table 2.

A curve obtained by plotting such a relationship between the standing time and the water content with the number of treated sheets as a parameter is very close to an exponential function.

That is, FIG. 4 is a curve in the case of moisture absorption left in a high temperature and high humidity (HH) state, and FIG. 5 is a normal temperature and normal humidity (NN).
It is a curve in the case of moisture release left in the state of.

In the former case, assuming that the moisture content before moisture absorption is x ₀ and the saturated moisture content is x ₁ , there is a relation that x ₁ > x ₀ , x ₀ is, for example, 7%, and the moisture content in the middle is the stack of paper. The water content y changes depending on the position and the order, and changes depending on an arbitrary elapsed time. The water content y is y = (x ₀ −x ₁ ) exp (−t / τ) +
It is calculated by x ₁ .

Τ is a time constant, and by selecting it, this equation can be well approximated to the graph of FIG. 4, which is the experimental result described above.

That is, in this state, the relationship between the saturated water content x ₁ (%), the y intercept (%) in the time constant, and the time constant τ (min) is as shown in Table 3 for the order of the number of sheets of each transfer sheet. .

[0036]

[Table 3]

In the latter case, there is a relation that moisture content before moisture release x ₁ moisture saturation saturated moisture content x ₀ (%) and x ₁ > x _0. x ₀ is, for example, 7%. Is the stack position of the paper,
The water content y ′, which changes depending on the order and changes with an arbitrary elapsed time, is y ′ = (x ₁ −x ₀ ) exp (−
t / τ) + x ₀ .

Τ is a time constant, and by selecting it, this equation can be well approximated to the graph of FIG. 5, which is the experimental result described above.

That is, in this state, the saturated water content x ₀ (%) and y ′ at the time constant are obtained with respect to the order of the number of transfer sheets.
Table 4 shows the relationship between the intercept (%) and the time constant τ (min).

[0040]

[Table 4]

As described above, by incorporating such a numerical calculation mechanism of an exponential function into the calculation means without using the table of the transfer current value regardless of moisture absorption or moisture release, the estimated water content of the transfer paper at that time can be obtained. By obtaining the corresponding accurate transfer current value, it becomes possible to stably obtain a high-quality copy without missing transfer or transfer repellency.

Of course, this table and this exponential function formula may be used in combination. By incorporating such an exponential function formula in the calculation means, when the power of the copying apparatus is turned off, the last humidity measurement data at that time is stored,
Again, by comparing the humidity measurement data when the power is turned on and judging whether it is moisture absorption or moisture release, the exponential function formula applied is
It becomes possible to automatically decide which one of the moisture release is selected.

Further, in this case, when the transfer current value table is also used, it is possible to automatically determine which of the moisture absorption and the moisture release is selected.

[0044]

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 or the normal humidity condition is changed with time based on the experimental result information and the position and the order of the number of passed sheets. In order to correspond to the optimum transfer current value associated with it, the moisture content and the elapsed time are made into an exponential function and built into the calculation unit, and at the time of copying, the humidity measurement data and the transfer paper position information input each time are calculated by the exponential function. The calculation means of the CPU that stores the formulas is operated, and the optimum transfer current is always supplied without error, so that a high-quality copy without transfer omission or transfer repelling can be stably obtained. Moreover, it can be applied to both cases of moisture absorption and desorption, and the selection has been made automatically and accurately.

[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.

FIG. 4 is a relationship diagram showing a temporal change in water content of transfer paper when absorbing moisture.

FIG. 5 is a relationship diagram showing a change over time in water content of transfer paper when moisture is released.

[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 (3)

[Claims] 1. A history storage means for storing a change in output value from a humidity detecting means and a measurement storage means for measuring a leaving time of the transfer paper in a transfer paper cassette, and the memory value and the cassette are stacked and stacked. It has a configuration in which the control is changed depending on the number of sheets of transfer paper and the order of paper passage, and the temporal change of the water content of the transfer paper while being left in the cassette is stored as an exponential function in the calculation means, and the charging unit An electrophotographic copying machine characterized in that the corona discharge output is programmed so as to follow an optimum value by the exponential function. 2. A history storage unit for storing a change in output value from the humidity detection unit and a measurement storage unit for measuring a leaving time of the transfer sheet in the transfer sheet cassette, and the storage value and the stack are stacked in the cassette. It has a configuration in which control is changed depending on the number of sheets of transfer paper and the order of paper passage, and the change over time in the moisture content of the transfer paper while being left in the cassette is stored as an exponential function in the calculating means to indicate that when moisture is absorbed An electrophotographic copying apparatus, characterized in that a time constant is varied at the time of dehumidification so that the corona discharge output of a charger follows an optimum value by the selected exponential function. 3. The method according to claim 2, wherein when the power is turned off, the last humidity measurement data is stored and again compared with the humidity measurement data when the power is turned on to determine whether moisture absorption or desorption is performed and an exponential function to be applied is selected. An electrophotographic copying machine characterized by: