JPH06148997A - Image processing device - Google Patents

Abstract

(57) [Summary] [Purpose] To determine the operation amount according to the detected state quantity and increase the response speed such as potential control. [Structure] Based on the membership function of the state quantity stored in the SRAM 3, the fitness of the detected state quantity is calculated. SR is calculated by a predetermined calculation based on this conformity
The inference result of each rule stored in AM2 is obtained. In addition, the operation amount is calculated based on the obtained inference result of each rule. The fuzzy rule change determination unit 1c determines whether the applied fuzzy rule has changed. Then, every time when the operation amount for performing the potential control should be calculated, that calculation is not performed, but the operation amount is calculated for the combination of the values of the state quantity predicted in advance and stored in the table memory. When the operation amount should be changed, the value in the table memory is picked up from the combination of the detected state quantities to determine the operation amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus such as a copying machine or a printer, and more particularly to an image processing apparatus which applies fuzzy inference to perform control.

[0002]

2. Description of the Related Art In a copying machine, a printer or the like, a change in electrostatic latent image is a major cause of change in image quality. This change in electrostatic latent image is caused by a change in drum sensitivity, a change in discharge amount of the primary charger, and a change in exposure amount. These changes are caused by the installation environment of the machine (for example, temperature and humidity) and related parts. Caused by deterioration and dirt. Therefore, there is a drum surface potential control mechanism in order to obtain a stable electrostatic latent image as much as possible even if these factors occur.

Conventionally, this drum surface potential control mechanism changes only the light portion target potential (VL), the dark portion target potential (VD), and the control coefficient according to the drum sensitivity so that an appropriate image can be obtained. Method, and has the following configuration. That is, when measuring the light portion potential, a reference current is passed through the primary charger and the potential sensor measures the drum surface potential. Then, based on the measured value, DC
Compare the measured value of the drum surface potential with the target value on the controller board, and if the drum surface potential is out of the target value,
The primary charging level control signal output from the DC controller board is corrected. As a result, the corrected current is applied from the high voltage transformer to the primary charger.

The above measurement and correction are repeated three times to bring the dark part potential close to the target value. Further, when measuring the dark part target potential, the reference lighting voltage is applied to the document illumination lamp. The original illumination lamp illuminates a standard white plate and projects the reflected light on the drum. Then, the potential of the surface of the drum projected on the drum is measured by a potential sensor and input to the DC controller board. This DC controller board compares the measured value with the target value, and if the measured value deviates from the target value,
The light amount adjustment signal output from the DC controller board is corrected. As a result, the corrected voltage is applied from the lamp regulator to the document illumination lamp.

The above measurement and correction are repeated three times to bring the bright portion potential close to the target value. It should be noted that the above-described operation is not performed for each copy, but is performed for every certain fixed time. The bright target potential, the dark target potential, and the control coefficient are set according to the sheet contained in the drum, and these settings are made only when the drum is replaced. Further, in PWM (pulse width modulation) control using an operational amplifier, which has been conventionally used to control the potential, the gain of the entire control circuit is mainly determined by the gain of the operational amplifier peripheral circuit, and the potential rises at this gain. , Falling characteristics and steady-state characteristics (for example,
In the case of constant voltage control, voltage regulation) is determined.

In this voltage control, for example, even if the potential rising / falling characteristics are changed due to the load variation of the potential due to the temporal change of the motor or the torque variation for raising the temperature of the motor, it is not possible to deal with the fuzzy. Inference control is used to control the rising / falling characteristics of the potential and the characteristics in the steady state. The reason why changes in the characteristics cannot be handled is that when the number of parameters that determine the rising / falling characteristics of the potential increases, or when there is an ambiguous relationship with the control amount among the parameters, This is because it is difficult to formulate the relationship between the control amount and the control amount.

By the way, conventionally, in an image forming apparatus such as a copying machine or a printer, the maximum copy density and gradation are deteriorated as the cumulative number of copies increases. This is due to the deterioration of the development contrast due to the deterioration of the latent image carrier or the deterioration of the developer (toner). On the other hand, in order to increase the developing electric field strength, the gap between the latent image carrier and the developing sleeve is narrowed, the AC component and DC component of the developing bias are increased, or the exposure light amount is increased to increase the development contrast. Measures have been taken to increase.

[0008]

However, the above-mentioned conventional potential control has the following problems. In the conventional voltage control method, the control parameters are only the bright portion target potential (VL), the dark portion target potential (VD), and the control coefficient as described above, but it is difficult to make a correction to obtain an appropriate image with only this. . That is, in addition to these parameters,
Change rate of light potential of drum, change rate of dark potential of drum, change rate of control coefficient of drum, environmental temperature, environmental humidity,
Optimal correction cannot be performed without considering the light amount of the document illumination lamp and the discharge amount of the primary charger.

In particular, the rate of change in the light potential of the drum, the rate of change in the dark potential of the drum, and the rate of change in the control coefficient of the drum are important parameters for determining image correction. This is because the light target potential, the dark target potential, and the control coefficient are different for each drum. Conventionally, these settings are made when the drum is replaced. However, this setting is only the setting of the initial sensitivity of each drum, and the correction is insufficient for the subsequent sensitivity change. In other words, the conventional method has a problem that the optimum correction cannot be performed between one correction control time and the next correction control time.

Therefore, in order to solve the above problems, a method of performing these controls using fuzzy control has been proposed. That is, in addition to the light target potential (VL), the dark target potential (VD), and the control coefficient as the control parameters, the change rate of the light section potential of the drum, the change rate of the dark section potential of the drum, and the control coefficient of the drum are set. The rate of change, ambient temperature, ambient humidity, the amount of light from the document illumination lamp, and the amount of discharge from the primary charger are also set.

By setting these parameters, the drum sensitivity can be optimally corrected and an appropriate image can be obtained. In particular, by adding the rate of change of the light potential of the drum, the rate of change of the dark potential of the drum, and the rate of change of the control coefficient of the drum to the parameters, the time between one correction control time and the next correction control time Although the optimum correction can be performed, if the number of state quantities is too large, it takes a long time to calculate the manipulated variable, and there is a problem that the speed required for the entire potential control system cannot be kept up.

Further, in the potential control by the fuzzy control, it takes a long time to calculate the manipulated variable, and there is a problem that the response speed required for the entire system cannot be obtained. For example, the switching frequency at the switching potential is usually several hundred KHz, but the calculation speed by fuzzy control cannot keep up with this frequency. On the other hand, depending on the control value, the membership function or fuzzy rule itself can be rewritten, or the state quantity can be divided into several levels and calculated in advance, and the results stored in a table memory. Method, but it is insufficient in terms of response speed.

On the other hand, in the above conventional image forming apparatus, in controlling the gap between the latent image carrier and the developing sleeve in order to maintain the maximum copy density, the atmospheric pressure is low in addition to the change of the state quantity such as the cumulative number of copies. At times, there is a problem that if the gap is narrowed, leakage occurs, or if the gap is narrowed, the developing electric field becomes strong and fogging occurs in the non-image area. Further, even if the AC component and the DC component of the developing bias are increased, the developing electric field becomes stronger, causing fog in the non-image area,
There is a problem of causing a leak.

If the gap between the latent image carrier and the developing sleeve is narrowed or the AC component of the developing bias is increased, the development contrast required to obtain the maximum copy density may be small, but the latent image is formed. If the exposure amount for forming is too large, there arises a problem that power consumption is increased and laser deterioration is accelerated. Therefore, although it is known that the latent image carrier-developing sleeve gap, the developing bias amount, and the exposure light amount, which are appropriate for maintaining the maximum copy density and the gradation, vary in a complicated manner. It is difficult to formulate the relationship between the state quantity and the control quantity. Further, if a lookup table or the like is provided for this purpose, the number of tables becomes enormous and the required memory capacity also increases.

A first object of the present invention is to provide an image processing apparatus capable of distinguishing a change in state quantity and changing a fuzzy rule to be applied to increase a response speed. A second object of the present invention is to provide an image processing apparatus which performs fuzzy inference to perform potential control in a copying machine that charges a photosensitive member on a drum to perform copying, thereby performing optimum drum sensitivity correction. Is.

A third object of the present invention is to provide an image processing apparatus which applies PWM control or fuzzy control according to the state quantity to the power supply control in a copying machine which charges a photoconductor to perform copying. That is. A fourth object of the present invention is to provide an image processing apparatus capable of obtaining a stable image with good gradation by controlling the developing sleeve and the like according to the state quantity by fuzzy reasoning.

[0017]

In order to achieve the above object, the invention according to claim 1 is to detect the state quantity related to the potential control, and to implement the state quantity and the potential control. A means for relating the relationship with the operation amount as a qualitative rule, and an inference means for inferring the operation amount based on the degree to which the state quantity belongs to a predetermined set according to the rule.

Further, in the invention described in claim 7, the first power supply control means, the second power supply control means, a means for detecting a state quantity related to the power supply control, the state quantity and the first Means for associating the relationship with the operation amount when the power supply is controlled by the power control means as a qualitative rule, and infers the operation amount based on the degree to which the state quantity belongs to a predetermined set according to the rule. The inference means and the switching means for switching so that either the control value by the inference means or the control value by the second power supply control means are output, and the switching means performs switching in accordance with the state quantity. , The power supply is controlled with this switched control value.

Further, in the invention described in Item 13, a developing portion is formed in a region near the latent image carrier and the developer carrier, and a gap between the latent image carrier and the developer carrier is constant. In the image processing apparatus for forming an image by forming a latent image on the latent image carrier by exposure by applying either one of an AC electric field or a DC electric field as a developing bias while keeping the distance, , A means for detecting a state quantity related to the control of the exposure and the developing bias, a means for controlling a controlled quantity of the gap, the exposure and the developing bias, and a relationship between the state quantity and the controlled quantity With a qualitative rule, means for storing a function expressing the state quantity and the control quantity in at least one fuzzy set, and the degree to which the state quantity belongs to a predetermined set according to the rule. Based on There are, and a reasoning means in which the control amount is calculated the degree of belonging to a predetermined set, infers the control amount.

[0020]

In the above structure, the operation amount is determined in accordance with the detected state amount, and functions to increase the response speed such as potential control.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. [First Embodiment] The first embodiment of the present invention will be described in detail below. FIG. 1 is a block diagram showing the arrangement of an image processing apparatus according to the first embodiment of the present invention. In the figure, reference numeral 1 denotes a CPU, which functions as a fitness calculation means, a calculation means, and a calculation means in this apparatus. As the fitness calculating means, the fitness of the detected state quantity is calculated based on the membership function of the state quantity stored in the SRAM 3. As the calculation means, the inference result of each rule stored in the SRAM 2 is obtained by a predetermined calculation based on the calculated conformance. In addition, as the calculation means, the operation amount is calculated based on the inference result of each rule obtained.

The counter 1a and the timer 1b are respectively used for obtaining the rate of change of the drum light portion potential from the detected state quantity, for example, the drum light portion potential. Also,
The fuzzy rule change determination unit 1c determines whether or not the applied fuzzy rule has changed, and if it does not change, it instructs that the membership function is not called again.

SRAM2 stores fuzzy rules (fuzzy propositions), and SRAM3 stores membership functions. The ROM 4 stores the control program of the CPU 1, and the RAM 5 stores the calculation of the conformity degree, calculation,
It is used as a calculation work area when performing calculations and the like.
A / D converters 6, 8, 11, 13, 16, 19, 22,
Of the 24, the A / D converters 22, 24, 6 and 11 convert the analog signals from the state quantity detecting units, which will be described later, from the respective state quantity detecting units into digital signals and transmit them to the CPU 1. Also, the A / D converters 8, 13, 16 and 19 are, on the contrary, CP
The digital signal from U1 is converted into an analog signal to control each load.

Environmental temperature detector 23, environmental humidity detector 2
5, the light quantity detection unit 7, and the potential measurement unit 12 function as a state quantity detection unit in the device according to the present embodiment. Further, the document illumination lamp 10, the primary charger 15, the transfer charger 18, and the developing cylinder 21 are the objects to be controlled by this apparatus here. Further, the lamp regulator 9, the primary corona current control circuit 14, the transfer corona current control circuit 17, and the developing bias control circuit 20 function as means for driving the above-mentioned controlled object.

The table memory 26 stores in advance the manipulated variable values for the combinations of the state variable values. Next, the control operation of the image processing apparatus having the above configuration will be described in detail. For the fuzzy control in the present embodiment, for example, (a) the light portion potential of the drum is used as the state quantity, and (b) the dark portion potential of the drum is used as the operation amount, and (c) the primary corona current level control signal is used as the operation amount. .

FIG. 2 shows the membership functions of these sets. Specifically, FIG. 2A is a membership function of the light part potential of the drum, FIG. 2B is a membership function of the dark part potential of the drum, and FIG. 2C is a primary corona current. 7 shows a membership function of a level control signal. As shown in FIG. 2, each set of the light potential of the drum, the dark potential of the drum, and the primary corona current level control signal has three fuzzy sets. For example, the fuzzy labels "ML", "MM", and "MH" are attached to three fuzzy sets of the light potential of the drum (see FIG. 2).
(A)), ML (Meibu Deni Low); “Light area potential of the drum is small”
Fuzzy set MM (Meibu Deni Middle); "Fluid potential of medium is medium" Fuzzy set MH (Meibu Deni High); "Light potential of drum is large"
Is a fuzzy set. The degree of belonging to each set is “0”
Takes any value from 1 to "1".

Therefore, the determination of the primary corona current level control signal in this embodiment using the fuzzy rule will be described. FIG. 5 shows the entire fuzzy rule in this embodiment. Among them, for example, the following <Rule 5> and <Rule 6> are used to determine the primary corona current level control signal.
> Use the fuzzy rule. That is, <Rule 5> IF (M = MM AND A = AM) T
HEN C = CM <Rule 6> IF (M = MM AND A = AH) T
HEN C = CL where M = light potential of the drum A = dark potential of the drum C = primary corona current level control signal

Now, assuming that the light portion potential of the drum, the dark portion potential of the drum, and the membership function of the primary corona current level control signal are given as shown in FIGS. 2 (a), 2 (b) and 2 (c), respectively. To do. Then, as shown in FIG. 3, when the light portion potential X0 of the drum and the dark portion potential Y0 of the drum are input,
MM and MM for X0, AM and AH for Y0
Corresponds. Therefore, of the fuzzy rules shown in FIG.
Inference is performed based on Rule 5> and <Rule 6>.

First, when inferring according to <Rule 6>,
For the light portion potential X0 of the drum, it is included in the set of MM at a degree of μX0 from the membership function of the light portion potential of the drum. Further, with respect to the dark portion potential Y0 of the drum, it is included in the set of AH at a degree of μY0 from the membership function of the dark portion potential of the drum. Then, the calculated μX0
And the minimum value of μY0 are determined, and the minimum value is used as the degree to which the condition part of <Rule 6> is satisfied, and the MIN calculation is performed with the value and the membership function of the primary corona current level control signal. The result of this calculation is the set S0 (trapezoid shown by the hatched portion) shown in FIG.

Similarly, when inferred according to <Rule 5>, the calculation result is the set T0 (trapezoid shown by the shaded portion) shown in FIG. Then, when the inference result of each rule thus obtained, that is, the set S0 and the set T0 are combined, the combined result is the set V0 (hatched portion) shown in FIG. Finally, the center of gravity (point P0) of this set V0 is calculated to obtain the primary corona current level control signal.

Here, these operations are not calculated and calculated each time the operation amount is to be calculated, but the operation amount value for the expected combination of the state amount values is calculated in advance. Then, this is stored in the table memory. Then, when it is time to change the operation amount, the operation amount can be determined from the combination of the detected state quantities only by collecting the value in the table memory shown in FIG. Can be fast.

The table memory is not limited to the two-dimensional one, but may be three-dimensional depending on the number of state quantities.
Next, an example will be described in which, among several state quantities, the state quantity that has changed and the state quantity that does not change are discriminated from each other and whether or not the fuzzy rule to be applied changes.

For example, when the values of the light portion potential X of the drum and the dark portion potential Y of the drum change from the values shown in FIG. 3 to the values shown in FIG. 4, that is, the value of X changes from X0 to X1.
In addition, assume that the value of Y changes from Y0 to Y1. In this case, the fuzzy rule to be applied is changed from <Rule 5> and <Rule 6> to <Rule 3> and <Rule 5>, but <Rule 5> is used as it is before and after the change. As a result, it is not necessary to call the membership function (MM, AM, CM used in <Rule 5>) in the SRAM 3 to the CPU 1 again, and the calling procedure can be omitted so that the response speed is further improved. Can be made.

As described above, according to this embodiment,
The calculation is not performed every time when the operation amount for performing the potential control should be calculated, but the operation amount is calculated in advance for the combination of the expected state value values and stored in the table memory. At the time when the operation amount should be changed, the operation amount can be determined only by collecting the value in the table memory from the combination of the detected state amounts, so that the response speed can be made very fast.

Further, the response speed can be further increased by distinguishing the changed state quantity and the unchanged state quantity from among some state quantities and determining whether or not the fuzzy rule to be applied is changed. . The state quantity is not limited to the light potential of the drum and the dark potential of the drum, and any state quantity relating to potential control can be used as the state quantity. Also, the operation amount is not limited to the primary corona current level control signal, but the transfer corona current level control signal,
The developing bias level control signal, or the rate of change thereof may be used.

That is, in order to obtain the optimum correction of the drum sensitivity and the proper image, as the control parameters, the light portion target potential (VL), the dark portion target potential (VD), the change rate of the light portion potential of the drum, and the dark portion potential of the drum. , The change rate of the control coefficient of the drum, the light amount of the document illumination lamp, the discharge amount of the temporary charger, and the like may be set. In particular, by adding the rate of change of the light potential of the drum, the rate of change of the potential of the dark area of the drum, and the rate of change of the control coefficient of the drum to the parameters, the optimum correction between one correction control time and the next correction control time Can be done.

Further, the number of state quantities is not limited to two, and any number of states can be combined, and the above fuzzy reasoning algorithm is an example, and the algorithm may be modified. For example, instead of taking the center of gravity of the area when synthesizing a plurality of rules, the value on the horizontal axis with respect to the maximum value on the vertical axis may be used as the inference result. Next, a modified example of the first embodiment will be described. <Modification 1> FIG. 7 shows an entire fuzzy rule according to Modification 1 of the first embodiment.

Here, as shown in FIG. 7, the temperature O is used instead of the dark area potential A of the drum. In the same figure, OL, OM, and OH are OL; a fuzzy set representing “low temperature”, OM; a fuzzy set representing “medium temperature”, OH; fuzzy set representing “high temperature”, respectively. is there.

Since the method of obtaining the optimum primary corona current level control signal in this modification is the same as the method in the first embodiment, its explanation is omitted here. <Modification 2> FIG. 8 is a diagram showing an entire fuzzy rule according to the modification 2, in which S represents humidity. Further, in the figure, SL, SM, and SH are, respectively, SL; a fuzzy set that represents "low humidity"SM; a fuzzy set that represents "medium humidity"SH; fuzzy set that represents "high humidity" .

Also in this modification, the method for obtaining the optimum primary corona current level control signal is the same as the method in the first embodiment, and therefore its explanation is omitted. [Second Embodiment] The second embodiment of the present invention will be described in detail below.

FIG. 9 is a block diagram showing the structure of the power supply device according to the second embodiment of the present invention. In the figure, 31
Is a CPU, and functions as a fitness calculation means, a calculation means, a calculation means, and a driver switching determination means in this apparatus. As the fitness calculating means, the fitness of the detected state quantity is calculated based on the membership function of the state quantity stored in the SRAM 33. As the calculation means, the SRAM is calculated by a predetermined calculation based on the calculated compatibility.
The inference result of each rule stored in 32 is obtained. In addition, as the calculation means, the operation amount is calculated based on the inference result of each rule obtained.

A / D is used as the driver switching determination means.
From the state quantity fetched via the converters 43 and 46, the driver is set to a control value for normal PWM control, or
Determine whether to use the fuzzy control value. The counter 31a and the timer 31b are respectively used when obtaining the rate of change from the detected state quantity, for example, the output voltage of the power supply. The SRAM 32 stores fuzzy rules (fuzzy propositions), and the SRAM 33 stores membership functions. And the ROM 34 is a CPU
RAM 35 for storing the control program 31.
Is used as a calculation work area when the CPU 31 performs fitness calculation, calculation, calculation and the like.

Output signal transfer interface (I / O)
The reference numeral 36 designates a signal from the CPU 31 for the driver switching section 38.
The driver switching unit 38 switches the control value of the PWM control or the control value of the fuzzy control and outputs it to the driver 39. The control signal for switching is
Driver switching unit 3 from CPU 31 via I / O 37
Sent to 8. The driver 39 drives the power supply 41 according to the actual operation amount calculated by the PWM control or the fuzzy control. This operation amount is, for example, a duty ratio.

The power source 41 operates the load 4 based on the above control.
4. Output a predetermined voltage to the motor, for example. The output voltage detector 42 functions as a state quantity detector, and detects the output voltage from the power supply 41. The output voltage detector 42 may be a room temperature sensor or a humidity sensor in some cases. The load current detection unit 45 also functions as state quantity detection means, and detects the value of the current flowing through the load 44 and the load state such as the number of rotations of the motor. The A / D converters 43 and 46 convert the analog signals from the output voltage detection unit 42 and the load current detection unit 45 into digital signals and send them to the CPU 31.

Next, the control operation of the power supply device having the above configuration will be described in detail. In the fuzzy control in the present embodiment, for example, (a ') the output voltage of the power supply, (b) the change rate of the output voltage of the power supply is used as the state quantity, and (c) the pulse width of the PWM control is used as the operation quantity. Use the duty ratio.

FIG. 10 shows the membership functions of these sets. When the membership function is actually set, the difference between the control target voltage and the output voltage of the power source (a ′) is calculated, and this difference is defined as (a) voltage deviation. Figure 10
(A) is a membership function of voltage deviation, FIG.
(B) is the membership function of the voltage change rate, and
FIG. 10C shows the voltage control amount, that is, the membership function of the pulse width duty ratio of the PWM control.

As shown in FIG. 10, each set of voltage deviation, voltage change rate, and pulse width duty ratio of PWM control has three fuzzy sets. For example, the voltage deviation of 3
For each fuzzy set, the fuzzy label is “V
“L”, “VM”, and “VH” are attached (see FIG. 10).
(A)), respectively VL (Voltage Low); Fuzzy set representing "small voltage deviation" VM (Voltage Middle); Fuzzy set representing "medium voltage deviation" VH (Voltage High); Let it be a fuzzy set representing "big". The degree of belonging to each set is “0”
Takes any value from 1 to "1". For example, in the case of a fuzzy set with the fuzzy label VM, the voltage deviation 2
The degree of belonging to the set of V, that is, the goodness of fit is “1.
0 ", and the degree of conformity of the voltage deviation of 1.5V or 2.5V is" 0.5 ".

Therefore, the determination of the voltage control amount (pulse width duty ratio of PWM control) in this embodiment using the fuzzy rule will be described. FIG. 13 shows the entire fuzzy rule in this embodiment. Among them, for example, the following <
The fuzzy rules of Rule 5> and <Rule 6> are used.
That is, <Rule 5> IF (V = VM AND R = RM) T
HEND = DM <Rule 6> IF (V = VM AND R = RH) T
HEN D = DL where V = voltage deviation R = voltage change rate D = pulse width duty ratio of PWM control.

For example, it is assumed that the membership functions of the voltage deviation, the voltage change rate, and the pulse width duty ratio of PWM control are given as shown in FIGS. 10 (a), 10 (b), and 10 (c), respectively. Then, as shown in FIG. 11, the voltage deviation X
When 0 and voltage change rate Y0 are input, V0 is applied to X0.
RM and RH correspond to M and VM, and Y0. Therefore, among the fuzzy rules shown in FIG. 13, <Rule 5> and <Rule 5>
Inference is performed based on rule 6>.

First, when inferring according to <Rule 6>,
The voltage deviation X0 is included in the VM set at a degree of μX0 from the membership function of the voltage deviation. Also,
The voltage change rate Y0 is included in the set of RH at a degree of μY0 according to the membership function of the voltage change rate. Then, the minimum value of the obtained μX0 and μY0 is obtained, and the minimum value is taken as the degree to which the condition part of <Rule 6> is satisfied, and the MIN calculation between the value and the membership function of the pulse width duty ratio of the PWM control is performed. To do. The result of this calculation is the set S0 (trapezoid shown by the hatched portion) shown in FIG.

Similarly, when inferred according to <Rule 5>, the calculation result is the set T0 (trapezoid shown by the hatched portion) shown in FIG. Then, when the inference result of each rule obtained in this way, that is, the set S0 and the set T0 are combined, the combined result is the set V0 (hatched portion) shown in FIG.
Becomes Finally, the center of gravity (point P0) of this set V0 is calculated to obtain the pulse width duty ratio of PWM control.

Next, an example in which normal PWM control and fuzzy control are switched in order to solve the problem that the calculation speed by fuzzy control cannot keep up with the speed required for the entire control system will be described. Here, when a fast response speed is required and the number of parameters (state quantities) that determine control is small, such as when the voltage rises / falls or when the load current changes drastically, the normal PW is used.
Power control is performed by M control. Then, a change in load current, such as a change with time, is slow and a fast response is not required, but since there are many parameters, the normal P
The power supply control is performed by fuzzy control only when the WM control is insufficient.

The above switching is performed by the CPU 31 and the CP
The U31 takes in the state quantity of the power source 41 via the A / D converter 43 and the state quantity of the load 44 via the A / D converter 46, and switches the state quantity value or a combination thereof. To judge. For example, assuming that the output voltage of the power supply is detected via the A / D converter 43 and the load current is detected via the A / D converter 46, the time change rate is calculated from the output voltage value. Then, if it is larger than a certain value, the commercial power supply (AC) is turned ON / OF.
Assuming that the voltage is rising / falling under the F control, the driver 39 is switched to the normal PWM control.

However, if the temporal change rate is calculated from the current value of the load and it is smaller than a certain value and the temporal change rate of the output voltage is smaller than the constant value, a fast response speed is unnecessary. And switch the driver to fuzzy control. Note that these determination results are transmitted to the driver switching unit 38 via the I / O 37. After all, normal P
Power supply control is performed by switching between WM control and fuzzy control as the case may be, and fuzzy control is performed only when there is no sudden change in load and there is an influence due to temperature, humidity, changes in wiring impedance, and the like.

Next, an example of changing the fuzzy rule to be applied when there is a changed state quantity among some state quantities will be described. For example, when the values of the voltage deviation X and the voltage change rate Y change from the values shown in FIG. 11 to the values shown in FIG. 12, that is, the value of X changes from X0 to X1, Y
Assume that the value of changes from Y0 to Y1.

In this case, the fuzzy rule to be applied is
<Rule 5> and <Rule 6> to <Rule 3> and <Rule 3>
Although it is changed to Rule 5>, <Rule 5> is used as it is before and after the change. As a result, the SRAM3
Membership functions in 3 (here <rule 5
VM, RM, DM) used in
Since it is not necessary to call 1 and this calling procedure can be omitted, the response speed can be further improved.

As described above, according to this embodiment,
When a fast response speed is required and the number of parameters (state quantities) that determine the control is small, the power supply is controlled by normal PWM control, and the load current changes slowly and a fast response is not required. Parameter exists, the power supply is controlled by fuzzy control only when the normal PWM control is insufficient. In the normal case, it is possible to control at a sufficiently fast response speed, and when the number of parameters is large. Since fuzzy control is performed, it is possible to perform fine power supply control according to the state of the load and the state of the power supply itself.

The state quantity is not limited to the voltage deviation and the voltage change rate, and any state quantity related to power supply control such as room temperature, humidity, the load current of the power supply, and the change rate of the load current of the power supply may be used. You can Also, the operation amount is PW
The change rate is not limited to the pulse width duty ratio of M control, and may be the change rate thereof. Furthermore, the number of state quantities is not limited to two,
You can combine any number.

The above fuzzy inference algorithm is an example, and the algorithm may be modified. For example, instead of taking the center of gravity of the area when synthesizing a plurality of rules, the value on the horizontal axis with respect to the maximum value on the vertical axis may be used as the inference result. Next, a modified example of the second embodiment will be described. <Modification 1> FIG. 14 shows an entire fuzzy rule according to Modification 1 of the second embodiment.

In this case, as shown in FIG. 14, the load current of the power source is used instead of the voltage change rate R. In the figure, EL, EM, and EH are respectively EL; a fuzzy set representing "the load current of the power source is small"EM; a fuzzy set EH representing "the load current of the power source is medium"; It is a fuzzy set that represents “a large current”.

Since the method of obtaining the optimum pulse width duty ratio of the PWM control in this modification is the same as the method in the second embodiment, its explanation is omitted here. <Modification 2> FIG. 15 is a diagram showing an entire fuzzy rule according to this modification 2, in which F represents the rate of change of the load current of the power supply. In the figure, FL, FM, FH are
FL: Fuzzy set representing "the rate of change of the load current of the power source is small"FM; Fuzzy set representing "the rate of change of the load current of the power source is medium"FH;"Large rate of change of the load current of the power source" Is a fuzzy set that represents.

Also in this modification, the method for obtaining the optimum primary corona current level control signal is the same as the method in the second embodiment, and therefore its explanation is omitted. [Third Embodiment] FIG. 16 is a block diagram showing the arrangement of an image forming apparatus according to the third embodiment of the present invention. In the figure, the CPU 101 performs fuzzy control described later,
The RAM 102 is used as a work area when performing fuzzy inference. In addition, this device also uses I / O port 1
04-107, A / D converters 108-110 for converting analog signals into digital signals, a motor drive circuit 111,
DC developing bias adjuster 112, AC developing bias adjuster 113, laser driver 114, density sensor for detecting toner image on drum, atmospheric pressure sensor 116, cumulative copy number counter 117, developing device-latent image carrier unit 200. Composed of.

FIG. 17 is an internal structure diagram of the developing unit-latent image carrier unit. As shown in the figure, this unit
Latent image carrier 201, developing sleeve 202, motor 20
4, the developing device mounting base 203 and the like. The motor 204 rotates the screw 205 to rotate the developing device mounting base 2
03 is moved in the direction of the arrow in the drawing to control the latent image carrier-developing sleeve gap. The CPU 101 generates a known PWM drive pulse via the I / O port 104, and controls the rotation of the motor 204 in the developing device-latent image carrier unit 200 via the drive circuit 111, thereby performing the above-mentioned latent drive. The gap between the image carrier and the developing sleeve is accurately controlled.

Similarly, the CPU 101 uses the I / O port 1
I / O by controlling the DC component of the development bias via
The AC component of the developing bias is controlled via the port 106. Further, the exposure amount (Full Power) of the laser is controlled via the I / O port 107. The developing conditions in the apparatus according to the present embodiment are: contrast potential 400V, AC bias V
_PP = 1200V, frequency 1800 Hz, the reference value of the latent image carrier-developing sleeve gap is 250 μm, and these values are stored in the ROM 102 in advance. The state quantities in this embodiment are (1) maximum copy density, (2) atmospheric pressure, (3) fog amount in non-image area, and (4) cumulative number of copies, and the control quantity is the latent image carrier. It is the developing sleeve gap. Then, here, the latent image carrier-developing sleeve gap is adjusted so that the maximum copy density becomes a reference value of 1.4 and the "fog" becomes 2% or less which is the reference.

Therefore, the adjustment control of the latent image carrier-developing sleeve gap in this embodiment will be described in detail. FIG. 18 is a diagram showing a fuzzy set of membership functions of the state quantities and the control quantities of the above (1) to (4) in the present embodiment. As shown in the figure, the maximum copy density, the atmospheric pressure, the fog amount in the non-image area, the cumulative number of copies, and the fuzzy set of the latent image carrier-developing sleeve gap are divided into several parts, and the degree of belonging to each set Is expressed as a value from 0 to 1.

For example, in the case of the latent image carrier-developing sleeve gap, as shown in FIG. 18D, (1) NB (Negative Big): a negative value and a large absolute value. (2) NS (Negative Small) ): Negative value and small absolute value (3) Z0 (Zero): around 0 (4) PS (Positive Small): Positive value and small absolute value (5) PB (Positive Big): Positive value It is assumed that the absolute value is large. Then, the degree of belonging to each set is changed from 0 to 1
Expressed as a value up to.

In the present embodiment, the above-mentioned four state quantities are used, but for simplicity of explanation, three state quantities of maximum copy density, atmospheric pressure and non-image fog are used among them. For example, in the case of Z0 (Zero) in FIG. 18A, when the maximum copy density is 1.4, the degree of belonging to the set Z0 is 1.0, and the maximum copy density is 1.35, 1. When it is 45, the degree of belonging to the set is 0.5.

Next, a method for determining the latent image carrier-developing sleeve gap deviation from the maximum copy density, atmospheric pressure, and fog state amount will be described. The following fuzzy rules are used for the above determination. That is, <Rule 1> IF (maximum copy density = Z0 and
Atmospheric pressure = Z0 and fog = Z0) THEN Latent image carrier-developing sleeve gap deviation = Z0 <Rule 2> IF (maximum copy density = NB and
Atmospheric pressure = Z0 and fog = Z0) THEN Latent image carrier-developing sleeve gap deviation = Z0 FIG. 19 includes <Rule 1> and <Rule 2> above.
The whole fuzzy rule in this embodiment is shown, and the reference numerals in the figure mean A: maximum copy density, B: atmospheric pressure, C: fog, and D: latent image carrier-developing sleeve gap deviation.

FIG. 20 shows a method for inferring the latent image carrier-developing sleeve gap deviation when the maximum copy density is x, the atmospheric pressure is y, and the fog is z. As shown in the figure, for <Rule 1>, the membership function of the maximum copy density is included in the set NB at a degree of μx with respect to the input x, and the membership function of the atmospheric pressure is used for the input y. It is included in the set of Z0 at the degree of μy, and included in the set of Z0 at the degree of μz with respect to the input z from the membership function of the fogging.

Then, the minimum values of the obtained μx, μy, and μz are taken, and the MIN calculation is performed between the obtained values and the membership function of the latent image carrier-developing sleeve gap deviation to obtain the set NS. In S, the calculation result indicated by S (hatched portion in the figure) is obtained. By performing the same calculation for <Rule 2>, the calculation result shown by the shaded portion T in the figure is obtained. Next, the center of gravity of the combined area of these S and T is obtained, and the center of gravity is determined by the fuzzy theory. It is set as the latent image carrier-developing sleeve gap deviation obtained in. The operation according to this fuzzy rule is performed once for each copy.

FIG. 21 is a flow chart showing the fuzzy inference processing procedure in this embodiment. In each of steps S1000, S1001, and S1002 in the figure, the density sensor 115 and the atmospheric pressure sensor 116 detect the maximum copy density, the atmospheric pressure, and the fog.
03, S1004, and step S1005.
According to the fuzzy rule shown in FIG. 9, the degree of belonging to the fuzzy set of control quantities is calculated from the degree of belonging to the fuzzy set of state quantities by the above method.

In step S1006, the center of gravity of the control amount with the highest possibility is calculated, and in the following step S1007,
This center of gravity is set as the latent image carrier-developing sleeve gap deviation. The CPU 101 uses P using this fuzzy theory.
In the WM control, by moving the motor 204 by the deviation amount so as to obtain the above-mentioned gap, the latent image is adjusted so that the maximum copy density is 1.4 and the fog is 2% or less with respect to the above state quantity. The carrier-developing sleeve gap is controlled.

As described above, according to this embodiment,
In the developing unit of an image forming apparatus such as a copying machine or a laser beam printer, in which a large amount of change is caused by the environment and the state quantity and the control quantity are governed by an ambiguous relationship,
By fuzzy reasoning, the latent image carrier-developing sleeve gap, the developing bias amount, which is the control amount, from the state quantities such as the maximum copy density, the atmospheric pressure, the cumulative number of copies, and the fog that are complicatedly related,
By calculating the appropriate value of the latent image exposure amount, it becomes possible to control the latent image carrier-developing sleeve gap, the developing bias amount, and the latent image exposure amount according to the state amount, and the maximum copy density without fog is large. It is possible to obtain a stable image with good gradation.

Further, since a large-capacity memory such as a look-up table is not required in the processing, a development contrast suitable for the latent image carrier-developing sleeve can be set, and an unnecessary light quantity is not used. A longer life and lower power consumption are possible. [Fourth Embodiment] In the third embodiment, the maximum copy density,
By controlling the latent image carrier-developing sleeve gap with respect to the state quantities such as atmospheric pressure, fog, and cumulative number of copies, the maximum copy density is maintained by fuzzy control and an image with less fog is obtained.

However, if the developing condition is kept constant and the gap between the latent image carrier and the developing sleeve is simply changed (for example, the gap between the latent image carrier and the developing sleeve is made small), the fog increases rapidly and V-D The slope of the curve suddenly increases. Then, due to this, the gradation is deteriorated, and the range with respect to the leak becomes extremely small. Therefore, in this embodiment, the AC bias is changed according to the change in the latent image carrier-developing sleeve gap. For example, the maximum electric field strength is constant (4v / μm)
The value of the AC development bias V _PP is changed so that the latent image carrier-developing sleeve gap (μm ) AC development bias V _PP (V ) 150 600 600 180 840 210 1080 1080 250 1400 275 1600 300 1800 V-D. When the curve is taken, the characteristic shown in FIG. 22 is obtained. FIG. 23 shows the membership function of the AC developing bias V _PP as the controlled variable.

As described above, the latent image carrier-the latent image carrier-is controlled by controlling the AC developing bias in addition to the developing sleeve gap.
By changing the AC developing bias according to the value of the developing sleeve gap, better images can be stably obtained, and the gradation is also improved compared to the case where the latent image carrier-developing sleeve gap is simply changed. To be done. Further, in terms of gradation, it is possible to change the gap between the latent image carrier and the developing sleeve when copying a character or a photograph. <Modification> In the third embodiment, the AC developing bias is used as the control amount in addition to the latent image carrier-developing sleeve gap, but from FIG. 22, it is maximum when the latent image carrier-developing sleeve gap is changed. It can be seen that when the development contrast required to reach the copy density changes and the gap between the latent image carrier and the development sleeve is narrow, a small development contrast is sufficient.

Therefore, the exposure amount of the laser or the like can be reduced in accordance with the gap between the latent image carrier-developing sleeve and the AC developing bias, whereby the life of the laser can be extended and the power consumption can be reduced. Further, since the development is not performed with the extra development contrast, the consumption of the extra toner can be prevented. Therefore, in this modified example, in addition to the latent image carrier-developing sleeve gap and the AC developing bias, the exposure amount is also a control amount.
Further, in order to control the development contrast, in addition to the exposure amount, the DC development bias is changed, and in addition to the above-mentioned effects, fogging control is also performed. Note that FIG. 24 is a membership function of the exposure amount and the DC developing bias according to this modification.

As described above, by increasing the control amount, the range of performing the fuzzy control can be widened, and the exposure amount can be easily controlled by the laser, and the image scanning is superior in image quality. The method according to the present modification is particularly suitable for reversal development. The present invention may be applied to a system including a plurality of devices or an apparatus including a single device. Further, the present invention is
It goes without saying that the present invention can also be applied to the case where it is achieved by supplying a program to a system or apparatus.

[0079]

As described above, according to the present invention, the response speed of control is increased by discriminating the change in the state quantity and changing the fuzzy rule to be applied accordingly to determine the operation quantity. be able to. Further, fuzzy inference is performed for potential control in a copying machine that charges a photosensitive member on a drum to perform copying, so that optimum drum sensitivity can be corrected and an appropriate image can be obtained.

Further, for power control in a copying machine which charges a photoconductor to perform copying, PW is performed according to the state quantity.
By selectively applying the M control or the fuzzy control, not only the response speed can be increased, but also the fine control according to the power supply load or the like can be performed. Further, by controlling the developing sleeve and the like according to the state quantity by fuzzy reasoning, a stable image with good gradation can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a potential control device according to a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a membership function of a set of state quantities according to the first example.

FIG. 3 is a diagram for explaining a method of determining a primary corona current level control signal in the first embodiment.

FIG. 4 is a diagram for explaining a method of determining a primary corona current level control signal in the first embodiment.

FIG. 5 is a diagram showing an entire fuzzy rule in the first embodiment.

FIG. 6 is a diagram showing a table memory that stores a state quantity value and an operation quantity value in the first embodiment.

FIG. 7 is a diagram showing an entire fuzzy rule according to a first modification of the first embodiment.

FIG. 8 is a diagram showing an entire fuzzy rule according to a second modification of the first embodiment.

FIG. 9 is a block diagram showing a configuration of a power supply device according to a second embodiment of the present invention.

FIG. 10 is a diagram showing a membership function of a set in the second embodiment.

FIG. 11 is a diagram for explaining a method of determining a pulse width duty ratio of PWM control in the second embodiment.

FIG. 12 is a diagram for explaining a method of determining a pulse width duty ratio of PWM control in the second embodiment.

FIG. 13 is a diagram showing an entire fuzzy rule in the second embodiment.

FIG. 14 is a diagram showing an entire fuzzy rule according to a first modification of the second embodiment.

FIG. 15 is a diagram showing an entire fuzzy rule according to a second modification of the second embodiment.

FIG. 16 is a block diagram showing a configuration of an image forming apparatus according to a third embodiment of the present invention.

FIG. 17 is an internal structural diagram of a developing device-latent image carrier unit according to the third embodiment.

FIG. 18 is a diagram showing a fuzzy set of membership functions of state quantities and control quantities in the third embodiment.

FIG. 19 is a diagram showing an entire fuzzy rule in the third embodiment.

FIG. 20 is a diagram showing a method of inferring a latent image carrier-developing sleeve gap deviation in the third embodiment.

FIG. 21 is a flowchart showing a fuzzy inference processing procedure in the third embodiment.

FIG. 22 is a diagram showing a VD curve according to the fourth example.

FIG. 23 is a diagram showing a membership function of an AC developing bias V _PP as a controlled variable according to the fourth embodiment.

FIG. 24 is a membership function of an exposure amount and a DC developing bias according to a modification of the fourth embodiment.

[Explanation of symbols]

1 CPU 1a counter 1b timer 1c fuzzy rule change determination unit 2,3 SRAM 4 ROM4 5 RAM 7 light intensity detection unit 6,8,11,13,16,19,22,24 A / D
Converter 9 Lamp regulator 10 Original illumination lamp 12 Potential measuring unit 15 Primary charger 18 Transfer charger 17 Transfer corona current control circuit 20 Development bias control circuit 21 Development cylinder 23 Environmental temperature detector 25 Environmental humidity detector 26 Table memory

Claims (24)

[Claims] 1. A means for detecting a state quantity related to potential control; a means for relating a relationship between the state quantity and an operation amount for performing the potential control as a qualitative rule; An image processing apparatus comprising: an inference unit that infers the operation amount based on the degree to which the state quantity belongs to a predetermined set. 2. The image processing apparatus according to claim 1, wherein the rule is expressed in the form of a membership function in which the state quantity and the operation quantity are expressed in fuzzy sets. 3. The inference means further comprises means for calculating the goodness of fit of the state quantity based on the membership function, and means for obtaining an inference result of the rule by a predetermined calculation based on the goodness of fit. The image processing apparatus according to claim 2, further comprising: a unit that calculates an operation amount based on the inference result. 4. A table memory for preliminarily storing a value of the operation amount for a combination of values of the state amount, wherein the inference means extracts an operation amount related to the changed state amount from the table memory. The image processing apparatus according to claim 1, wherein the image processing apparatus performs inference. 5. The potential control is potential control in a copying machine for copying by charging a photosensitive member on a drum.
The state quantity includes a light potential of the drum, a dark potential of the drum, a control coefficient of the drum, a change rate of the light potential of the drum, a change rate of the dark potential of the drum, a change rate of the control coefficient of the drum,
At least one of the ambient temperature, the ambient humidity, the light amount of the original illumination lamp, the change rate of the original illumination lamp light amount, the discharge amount of the primary charger, and the change rate of the discharge amount of the primary charger is included. The image processing apparatus according to claim 1. 6. The potential control is potential control in a copying machine for copying by charging a photosensitive member on a drum,
The image processing apparatus according to claim 1, wherein the operation amount is a primary corona current level control signal, a transfer corona current level control signal, or a developing bias level control signal. 7. A first power supply control means, a second power supply control means, a means for detecting a state quantity related to power supply control, and a power supply control by the state quantity and the first power supply control means. Means for associating the relationship with the operation amount as a qualitative rule, inference means for inferring the operation amount based on the degree to which the state quantity belongs to a predetermined set according to the rule, and control by the inference means A switching means for switching so that either the value or the control value by the second power supply control means is output, and the switching means performs switching according to the state quantity, and at this switched control value An image processing apparatus characterized by performing power supply control. 8. The image processing apparatus according to claim 7, wherein the rule is expressed in the form of a membership function in which the state quantity and the operation quantity are expressed by fuzzy sets. 9. The inference means further comprises means for calculating the goodness of fit of the state quantity based on the membership function, and means for obtaining an inference result of the rule by a predetermined calculation based on the goodness of fit. The image processing apparatus according to claim 8, further comprising: a unit that calculates an operation amount based on the inference result. 10. The power supply control is power supply control in a copying machine that charges a photoconductor to perform copying, and the state quantity includes an input voltage of the power supply, a change rate of the input voltage of the power supply, and an output voltage of the power supply. , Output voltage change rate of power supply, room temperature, humidity,
The image processing apparatus according to claim 7, wherein at least one of a load current of the power supply and a change rate of the load current amount of the power supply is included. 11. The power supply control is power supply control in a copying machine that charges a photoconductor to perform copying, and the operation amount is a pulse width duty ratio in pulse width modulation control or a change in the pulse width duty ratio. The image processing apparatus according to claim 7, wherein the image processing apparatus is a rate. 12. The image processing apparatus according to claim 7, wherein the second power supply control means performs pulse width modulation control. 13. A developing portion is formed in a region in the vicinity of the latent image carrier and the developer carrier, the gap between the latent image carrier and the developer carrier is maintained at a constant distance, and an alternating current is applied as a developing bias. In an image processing apparatus for forming a latent image on the latent image carrier by exposure by applying either one of an electric field and a DC electric field, the gap, the exposure, and the developing bias A means for detecting a state quantity related to control, a means for controlling a controlled quantity of the gap, the exposure, and the developing bias, and a rule relating the relationship between the state quantity and the controlled quantity as a qualitative rule. Means, a means for storing a function expressing the state quantity and the control quantity in at least one fuzzy set, and the control quantity is predetermined based on the degree to which the state quantity belongs to a predetermined set according to the rule. Collection of Degree calculating a belonging to an image processing apparatus characterized by comprising inference means for inferring the control amount. 14. The rule comprises an antecedent part and a consequent part, and the inference means is further configured such that at least one of the state quantities at that time is a fuzzy set of state quantities of the antecedent part of the rule. The first calculating means for calculating the degree of belonging to the function expressed by the above, and the degree to which the function expressing the control amount of the consequent part of the rule by a fuzzy set matches the state quantity at that time,
The second calculation means for calculating using the degree calculated by the calculation means, and the means for synthesizing the results calculated by the second calculation means for all the rules, The image processing apparatus according to claim 13, wherein the actual control amount is calculated. 15. The state quantity includes atmospheric pressure, copy density,
14. The image processing apparatus according to claim 13, wherein at least one of the fogging of the non-image portion and the cumulative number of copies is included. 16. The regulation means controls the size of the gap in correspondence with the level of the atmospheric pressure, increases the gap when the atmospheric pressure is high, and decreases the gap when the atmospheric pressure is low. The image processing apparatus according to claim 15, wherein the image processing apparatus comprises: 17. The ruler controls the magnitude of the exposure in accordance with the level of the atmospheric pressure, reduces the exposure when the atmospheric pressure is high, and increases the exposure when the atmospheric pressure is low. The image processing apparatus according to claim 15, wherein the image processing apparatus comprises: 18. The regulation means controls the magnitude of the application of the developing bias in accordance with the level of the atmospheric pressure, reduces the application of the developing bias when the atmospheric pressure is high, and
The image processing apparatus according to claim 15, wherein the application of the developing bias is increased when the atmospheric pressure is low. 19. The regulation means controls the size of the gap corresponding to the size of the cumulative number of copies, reduces the gap when the number of cumulative copies is large, and reduces the number of cumulative copies. The image processing apparatus according to claim 15, wherein the gap is increased in the case. 20. The ruler controls the size of the gap in accordance with the level of the toner image density of a potential portion where the copy density is maximized, which is formed on the latent image carrier in a test mode, and controls the size of the gap. 16. The image processing apparatus according to claim 15, wherein the gap is increased when the toner image density is high, and the gap is decreased when the toner image density is low. 21. The ruler controls the size of the gap in accordance with the level of toner image density in a fog portion of the non-image portion formed on the latent image carrier in a test mode to control the size of the gap, The image processing apparatus according to claim 15, wherein the gap is increased when the image density is high, and the gap is decreased when the toner image density is low. 22. The control amount for the exposure is increased when the control amount for the gap is large, and the control amount for the exposure is decreased when the control amount for the gap is small. The image processing device according to item 1. 23. When the control amount for the gap is large, the AC electric field as the developing bias is increased, and when the control amount for the gap is small, the AC electric field as the developing bias is decreased. The image processing device according to claim 13. 24. The image processing apparatus according to claim 13, wherein the image formation is performed by reversal development.