JPH02699B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling image formation in electrophotography.

Conventionally, in image forming apparatuses using electrophotography such as copying machines, in order to stabilize the surface potential on the photoreceptor, this surface potential is read with an electrometer, etc.
A method is used in which a charger or the like is controlled by performing comparisons, calculations, and other processing on analog values.

In this type of method, comparison and
The circuitry for performing calculations and other processing is complex and uses many parts, and malfunctions are likely to occur due to noise and the like.

In recent years, due to advances in semiconductor technology, calculation units, register units, accumulators, program counters,
One-chip microprocessors with built-in stack pointers and the like have been provided, and it is conceivable that such microprocessors can be applied to control and diagnosis of image forming apparatuses such as copying machines.

The present invention has been made in view of the above points, and its purpose is to stabilize and control the surface potential regardless of the deterioration of the photoreceptor, fluctuations in environmental conditions, etc., and to perform this stabilization control digitally using a processor. An object of the present invention is to provide an image forming apparatus that can be executed under control.

That is, the present invention provides a charging means for charging a photoreceptor, an image exposure means for forming an electrostatic latent image by imagewise exposing the photoreceptor charged by the charging means, and a static eliminator for removing static from the photoreceptor. a developing means for developing an electrostatic latent image formed on the photoreceptor; a reference light source for exposing the photoreceptor; a detection means for detecting a surface potential on the photoreceptor; A/D conversion means for converting an output analog value into a digital value; and controlling operating conditions of the static eliminator based on a digital value corresponding to a first bright area potential output from the A/D conversion means. a first program; a second program for controlling the operating conditions of the charging means based on a digital value corresponding to the dark potential output from the A/D conversion means; and a third program for controlling the operating conditions of the image exposure means based on a digital value corresponding to a second bright area potential, and sequentially executing the first, second and third programs. control means for optimizing the dark potential and the first and second light potential, the control means controlling the first light source formed by exposing the photoreceptor to the reference light source after charging the photoconductor;
The potential of the bright area potential portion is detected by the detection means, and a first program for adjusting the first bright area potential is executed based on a digital value corresponding to the detected value to determine the operating conditions of the static eliminator. first to control
The process is carried out, and then the photoconductor is charged under the static elimination conditions controlled in the first process, and the potential of the dark area potential portion formed without being exposed is detected by the detection means, and the detected value is A second step is executed to determine the operating conditions of the charging means by executing a second program for optimizing the dark potential based on the corresponding digital value, and then the charging means is controlled by the first step and the second step. charging the photoreceptor based on the static elimination conditions and charging conditions, and then detecting the potential of a second bright portion potential portion formed by exposing the photoreceptor with the image exposure means, using the detection means;
A third program for optimizing the second bright area potential is executed based on the digital value corresponding to this detected value and the optimized first bright area potential obtained in the first step. The present invention provides an image forming apparatus characterized in that a third step of controlling the operating conditions of the image exposure means is executed.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of an electrophotographic apparatus. First, a light image is exposed through a lens system 3 onto the surface of a photoreceptor 1 (Mylar 101, CdS 102, conductive substrate 103) which has been primarily charged by a charger 1. As the static eliminator 4 discharges, an electrostatic latent image is formed, and if necessary, the entire surface is exposed with a lamp to increase the contrast of the latent image, a developing device 6 forms a visible image, and a paper feeding roller 7 transfers the image to a cassette. The visible image is transferred by a transfer charger 10 onto a transfer paper 9 fed from a paper 8, and the transfer paper 9 is separated from the photoreceptor 1 by a separation roller 11, and further sent to a fixing device 12 consisting of a fixing roller to be fixed. The paper is then discharged onto the tray 13.

In such copying machines that use electrophotographic technology, the potential on the surface of the photoreceptor, which has the greatest effect on visible images, is affected by variations in the installation of the charger, variations in the voltage of the charging transformer, changes in ambient temperature and humidity, and exposure to light. It is difficult to maintain a predetermined potential because it is affected by variations in body characteristics and deterioration.

The surface potentials of the photoreceptor obtained in the bright and dark areas of each copying processing position as described above are shown in FIG. When the humidity around the photoreceptor increases, the surface potentials ○a and ○ro at points change as shown in ○a and ○ro in Figure 3, and also as the photosensitive drum ages, the surface potentials ○a and ○ro in Figure 4 change.
The color changes as shown in ○ and B, and the contrast between bright and dark areas cannot be obtained. Moreover, it goes without saying that even if the distance of the charger from the drum surface is different from the beginning, the potentials of ○A and ○B will not be able to obtain the desired values.

Therefore, the copying conditions are controlled so that the potential at the point remains constant under any conditions, as shown at ○A' and ○B' in FIGS. 3 and 4.

Further explanation will be given with reference to the embodiment shown in FIG. In the figure, 21 is a probe for detecting the surface potential of the photoconductor, and 22 is a reference light source, which is provided to emit light through an AC static eliminator.
23 is an exposure aperture reversible motor that automatically adjusts the amount of light from the exposure lamp 24; 25 is an aperture adjustment dial;
26 is a sample manuscript.

That is, the potential at a point when the reference light source is turned on or off is detected by the surface potential detection probe 21, the charging transformer is controlled by the signal, and the potential of the charging transformer is fixed so that the optimum surface potential is obtained. If so, next, the document exposure lamp is turned on without using the reference light source, and the sample paper provided at one corner of the document table is irradiated. The exposure diaphragm is varied by rotating the lens drive unit in the forward or reverse direction by an operably coupled reversible motor until the confirmed potential becomes equal to the potential of ◯◯ obtained in the first step.

A control circuit using a microcomputer that embodies the above method will be explained.

The AD converter in the figure converts the input signal a into digital data and outputs it to the next stage.
It is a central control unit that has processing functions such as reading and decoding input and instruction data from converters, memory ROM, and RAM, addition and subtraction, logical operations, and comparisons.
The ROM is a read-only memory that stores the procedure (program) for operating this control circuit for the above purpose, the RAM is a writable memory that temporarily stores data related to the program processing, and the output device 1 is a read-only memory that stores the procedure (program) for operating this control circuit for the above purpose. Similarly, output devices ₂ and 3 output signals to set the voltage of the AC transformer and DC transformer of each component. The output devices 4 and 5 are for outputting signals for on/off control of the AC high voltage transformer, DC high voltage transformer, main drive motor, full-surface exposure lamp, reference light source, document exposure lamp, and reversible motor for controlling the exposure aperture. It is also connected to the actual load via an interface circuit. AC high voltage transformer 1, 2
The outputs of are connected through diodes in opposite directions, but this means that only the component is output from AC high voltage transformer 1, and only the component is output from AC high voltage transformer 2, and furthermore, component>component. This is to make it so. In other words, the static electricity is removed by the difference between these two components, and therefore the third and fourth
In the figure, the input voltage of the AC high voltage transformer 2 is increased to increase the voltage of the component in order to change from ○RO to ○RO', and the input voltage of the DC transformer is increased to change from ○I to ○I'. It raises it.

The input device inputs a clock signal for executing a copying sequence, a drum position (home) signal, a registration signal for transfer timing, and a signal (not shown) detecting developer concentration, jam, etc. DA1～
3 converts digital signals from each output device 1 to 3 into analog quantities, and connects AC high voltage transformers HVT _{1 to 3} and
This is a DA converter that outputs voltage to a DC high voltage transformer, and the output timing is determined by the signal from the output device 4. The ROM stores a program for controlling the potential according to a flowchart as shown in FIG. The RAM stores in advance the AC optimum potential, the potential, and the DC optimum potential.

Incidentally, the AD converter is controlled by a control signal line and an address bus, and outputs a 4-bit digital conversion signal to the data bus.

The operation will be explained based on the flowchart shown in FIG. Prior to the copy cycle, the CPU uses output device 1
is specified via the address bus, and a binary signal for setting the AC high voltage transformer 1 to a predetermined potential is output to the output device 1 via the data bus. This is converted into an analog quantity by a DA converter and provides a potential to the AC high voltage transformer 1.
However, at this point, the control signal line ○a of the D-A converter is not set, so data is simply transferred to the output device 1. Subsequently, predetermined binary signals are similarly transferred to the output devices 2 and 3. Furthermore, the CPU specifies the address of the output device 5,
Binary code 1000 to turn on the main drive motor
output. This is a code when the output device 5 can output 4 bits in parallel, and is output via the data bus (hereinafter referred to as data bus), and means that the main motor terminal is 1 and the other terminals are 0 (SP-
1).

Next, the timer is operated until the rotation of the drum becomes constant (SP-2), and the next execution is waited. When the time is up, the CPU outputs the binary code 1111 to the output device 4, and the primary high voltage transformer and the AC high voltage transformer 1. ，
2 Turn on the entire surface exposure lamp and reference light source (SP-
3).

SP-4 to SP-14 are routines that turn on the reference light source and change the AC high-voltage transformer 2 to find the appropriate value for the bright area potential of the photosensitive drum, SP-15 to SP-24
is a routine that turns off the reference light source and changes the DC high-voltage transformer to find an appropriate value for the dark potential of the photosensitive drum.

The flag here is used to determine whether or not to branch during program execution, and is set to
Proceed execution to the yes side, and proceed to the no side by resetting.

If you change the DC high voltage transformer with SP-15 to SP-24, it will also change the bright area potential, so again
A loop α is provided to return to the routine of SP-15 to SP-24 and check again. Flag1 is light part,
SP-27 that both potentials in the dark area have reached appropriate values.
Since Flag2 and Flag3 do not generate spark discharge, SP-4 to SP-
14. It is provided to remember that the voltage limit has been reached at SP-15 to SP-24. Therefore, when Flag2 is set, the routines SP-4 to SP-14 are not executed, and when Flag3 is set, SP-14 is not executed.
-15~SP-24 is not executed and the program is forced to proceed to the next program.

SP-28 to SP-35 turn on the document exposure lamp and rotate the exposure aperture control motor in the forward or reverse direction so that the potential E _L set in SP-4 to SP-14 is equal to the appropriate light amount. This is a routine to set.
When this is complete, turn off all loads using SP-36 and enter the copy cycle. The above is an example of obtaining the optimum potential for a standard color tone, and a reference light source and sample paper corresponding to that color tone are provided. However, since the tones of the originals vary, after setting the appropriate aperture, the operative connection between the lens drive unit and the motor is released, and instead it is operatively connected to the adjustment dial, so that it can be adjusted to match the tones of the originals. You can get the image.

From the flowchart in Figure 6 above, it can be seen that a general-purpose microcomputer (μ-COM4,
Since it is easy for those skilled in the art to create program steps using dedicated instruction codes using the INTEL 8080, etc., the instruction word steps will be omitted.

Note that the timer can be implemented by storing the timer time in advance as a code in RAM, and by providing a routine that sequentially subtracts this code one by one and determines whether it has reached 0. However, it is also possible to use an external timer means. to start the timer at the out of the control circuit and in
This can also be done by detecting time-up.

Further, if a check zone is provided around the photosensitive drum to which reference light and sample light are irradiated, control can be performed even during the copy cycle.

In this way, the detection signal is converted into digital, read as a count value, and the judgment function of the microcomputer is used to obtain the appropriate electrostatic voltage, which is then converted into analog and applied to the high voltage transformer, or to obtain the appropriate amount of exposure and adjust the exposure. It has the characteristics of

Furthermore, a reference light source is provided, and as a first step, before the copying cycle, the potential of the photoreceptor surface when the reference light source is turned on and the potential when it is turned off are detected by a surface potential detection probe, and the detection signal is used to detect the transformer. It is characterized by controlling the output.

Next, in the second step, the potential on the surface of the photoreceptor is detected in the same way as above when the sample paper (corresponding to the bright area) provided at one corner of the document table is irradiated by the document exposure lamp. It is characterized in that exposure is adjusted by a signal so that the surface potential becomes equal to the potential of the bright area (when lit) obtained in the first step.

By the way, the reason for dividing into the first and second stages is that if the photosensitive drum deteriorates over time, the fourth stage
The potential of the primary charging transformer and the neutralization transformer must be increased to achieve ○A → ○A' and →○Ro →○Ro' in the diagram, but the upper limit of this potential must be below the spark discharge starting voltage. Therefore, in order to guarantee against deterioration of the photosensitive drum, the potentials ○A and ○B obtained with this voltage must be set to optimal values, so the first step is to set and maintain the potential of the transformer. If you use the light from the document exposure lamp without using a reference light source, the amount of light irradiated will vary depending on the instability of the light intensity of the document exposure lamp and the setting value of the exposure aperture adjustment dial, making it impossible to confirm the surface potential of the standard color tone. After setting the appropriate surface potential by setting a reference light source that does not pass through the lens system in the first step, I decided to vary the aperture in the second step to find the appropriate value again using the light intensity of the exposure lamp that will actually be used. be.

As described above, according to the present invention, the static elimination conditions are controlled according to the first bright area potential, the charging conditions are controlled according to the dark area potential, and then the static electricity is formed based on the controlled static elimination conditions and charging conditions. Since the image exposure conditions are controlled according to the second bright area potential, the image exposure conditions can be controlled under optimized static elimination conditions and charging conditions.
It becomes possible to optimize the static elimination conditions, charging conditions, and image exposure conditions with extremely high precision, and it is possible to simply obtain an appropriate image regardless of photoreceptor deterioration, environmental changes, and the like.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the electrophotographic device, and Figure 2 is a schematic diagram of the electrophotographic device.
FIG. 3 is a graph showing surface potential changes with respect to humidity; FIG. 4 is a graph showing changes in surface potential over time; FIG. 5 is a circuit diagram of the stabilizing device of the present invention; FIG. The figure is a flowchart showing the procedure for stabilizing the surface potential according to FIG. 5, in which 21 is a surface potential detection probe;
22 is a reference light source, 23 is an aperture motor, 24 is an exposure lamp, and 26 is a sample document.

Claims (1)

[Scope of Claims] 1. Charging means for charging a photoreceptor; Image exposure means for forming an electrostatic latent image by imagewise exposing the photoreceptor charged by the charging means; and removing static from the photoreceptor. a developing means for developing an electrostatic latent image formed on the photoreceptor; a reference light source for exposing the photoreceptor; a detection means for detecting a surface potential on the photoreceptor; A/D conversion means for converting an analog value outputted from the means into a digital value; and an operating condition of the static elimination means based on the digital value corresponding to the first bright area potential outputted from the A/D conversion means. a first program for controlling, a second program for controlling operating conditions of the charging means based on a digital value corresponding to the dark potential output from the A/D converting means; a third program for controlling operating conditions of the image exposure means based on a digital value corresponding to the second bright area potential to be output;
control means for optimizing the dark potential and the first and second light potential by sequentially executing second and third programs, the control means controlling the reference light source after charging the photoreceptor; Detecting the potential of a first bright potential portion formed by exposure to light by the detection means,
Based on the digital value corresponding to this detected value, the first
A first step of controlling the operating conditions of the static eliminator by executing a first program for optimizing the bright area potential, and then controlling the photoreceptor under the static eliminator conditions controlled in the first step. The detecting means detects the potential of the dark potential portion formed without charging and exposing, and executes the second program for adjusting the dark potential based on the digital value corresponding to this detected value. A second step of determining the operating conditions of the charging means is executed, and then the photoreceptor is charged based on the static elimination conditions and charging conditions controlled in the first step and the second step, and then exposed by the image exposure means. The potential of the second bright area potential portion formed by this is detected by the detection means, and the digital value corresponding to this detected value and the optimized first bright area potential obtained in the first step are combined. An image forming apparatus characterized in that a third step of controlling operating conditions of the image exposure means is executed by executing a third program for optimizing the second bright area potential based on the above.