JPH07152211A - Process controlling device - Google Patents

Abstract

PURPOSE:To obtain a sufficient image density at a block part and to obtain a good- quality image having sufficient brightness at a white part by controlling the density of black by correcting an electrostatic charging potential and controlling the density of white by correcting a radiated light quantity so that the surface potential of a photoreceptor may be equal to or under developing bias potential. CONSTITUTION:The correction amount of the light quantity of a copying lamp 21 is obtained based on the correction amount of the electrostatic charging potential of the photoreceptor 1 by a CPU 4. When the photoreceptor 1 is exposed in a state where the obtained correction amount is added, the surface potential of the photoreceptor 1 is optically attenuated. The light quantity of the lamp 21 at this time is enough to lower the surface potential of the photoreceptor 1 to be equal to or under the developing bias potential in the case of assuming that the surface potential of the photoreceptor 1=electrostatic charging potential. By exposing the photoreceptor 1 with the obtained light quantity of the lamp 21, the photoreceptor 1 is sufficiently optically attenuated and the complete white part is obtained in the case of performing toner adhesion. Namely, when the surface potential of the photoreceptor 1 is equal to or under the developing bias potential, the toner is attracted to a developing device side and does not adhere on the surface of the photoreceptor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as an electrostatic copying machine or a laser printer, which has a stable quality regardless of deterioration of a photoconductor or a developer or a change in environmental conditions. It relates to a process control device for obtaining an image.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, the surface potential of a photoconductor (actual potential on the surface of the photoconductor) changes greatly due to changes in environmental conditions (temperature, humidity, etc.). For example, in the case of an OPC photoconductor, since the photocarrier has temperature dependence, the surface potential under a low temperature environment is lower by about 100 to 150 V than the surface potential at room temperature.
Further, in the case of the Se photoconductor, since the amount of thermally excited carriers generated in the photosensitive layer has temperature dependence, the surface potential under low temperature environment is increased by about 50 V as compared with that at room temperature, and conversely under high temperature environment. The surface potential decreases by about 10 to 100V. As a result of such a variation in surface potential, the density of the image changes.

The environmental conditions also affect the developer (toner). The toner used in the electrophotographic image forming apparatus is in powder form and is very sensitive to changes in humidity. Generally, when the humidity is low, the electric resistance of the toner itself becomes high, and the electric charge holding power of the frictionally charged toner becomes high. If the charge holding power of the toner increases, the density of the copy image will decrease. On the contrary, when the humidity is high, the charge holding power of the toner becomes low and the density of the copy image becomes high. That is, the developer is affected by the change in environmental conditions, and the image density changes.

The above-mentioned fluctuation of the image density is short-term, but the image density also changes in the long-term.

Normally, the photosensitive member undergoes mechanical stress due to a cleaner or the like during use to cause film thickness reduction, and the film thickness of the photosensitive member gradually decreases. Then, the charge on the surface of the photoconductor increases, and as a result, the sensitivity of the photoconductor apparently decreases and the density of the formed image becomes dark. This phenomenon is particularly remarkable in the case of an OPC photoconductor. In addition, the image density changes due to various factors such as deterioration of the developer and deterioration of the charger.

In order to collectively correct the change in the image density due to various causes as described above, it is generally performed to adjust the charging potential (potential applied to the charger for charging the photoconductor). ing. This is a method in which the surface of the photoconductor is charged with a predetermined charging potential, toner is attached to the charged region, the toner concentration is detected, and the charging potential of the photoconductor is controlled based on the detected concentration. , JP Sho 60
This method is disclosed in Japanese Patent Publication No. 80871. By controlling the charging potential in this manner, the amount of toner attached to the surface of the photoconductor is adjusted, and the image density is controlled.

[0007]

Some electrophotographic image forming apparatuses have a function of preventing the temperature and humidity of the photoreceptor from changing by disposing a heater in the photoreceptor. . In such an image forming apparatus having a heater inside the photoconductor, the surface potential of the photoconductor is less affected by environmental conditions, and the surface potential of the photoconductor does not change in the short term. Therefore, the cause of the short-term change in the image density in this case is a decrease in the charge amount of the toner or a change in the density. Therefore, if the change in image density is corrected by the charge potential of the photoconductor, the surface potential of the photoconductor will change depending on the environmental conditions.

The change in the surface potential of the photosensitive member affects the brightness of the image. Here, the brightness refers to the degree of blackness of the image density, ie, how dark the density of the image portion is (in the case of black toner), while the brightness refers to the degree of whiteness of the white density of the white background portion. There is. An image of good quality is required to have sufficient blackness and be free from fog and stains on the white background.

However, as described above, when the fluctuation of the image density due to the decrease of the charge amount of the toner or the change of the density is corrected by the charging potential, the surface potential rises, and even if the image density of the black portion is sufficient. However, there is a problem that the whiteness of the white background portion is very poor.

The present invention has been made in view of the above problems, and it is possible to obtain a sufficient image density in a black portion and a sufficient quality image in a white background portion with sufficient brightness. It is to provide a process control device capable of performing.

[0011]

According to a first aspect of the present invention, means for detecting the density of a toner image by charging the surface of a photoconductor and adhering toner thereto, and a density detection value of the toner image are determined in advance. Means for obtaining the correction amount of the charging potential of the photoconductor required to obtain the above value and the charging surface potential of the photoconductor taking the above correction amount into consideration, the surface potential is approximately the developing bias potential or less. And a calculation unit that stores a relationship between the correction amount of the copy lamp light amount necessary for optical attenuation and the correction amount of the charging potential, and calculates the correction amount of the copy lamp light amount from the correction amount of the charging potential. It is characterized by having.

According to a second aspect of the present invention, means for detecting the density of the toner image by charging the surface of the photoconductor and adhering the toner thereto, and the density detection value of the toner image are predetermined values. Means for obtaining the charging potential of the photoconductor required for the photoconductor, and the amount of copy lamp light necessary for attenuating the surface potential of the photoconductor below the developing bias potential when the charging potential is the surface potential of the photoconductor, And a calculation unit that stores a relationship with the charging potential and calculates the copy lamp light amount from the charging potential.

According to a third aspect of the present invention, in the process control apparatus according to the first aspect or the second aspect, a means for detecting a corresponding value of the photosensitive member temperature is provided, and the arithmetic means is the charging potential. Or the amount of correction,
A relationship between the copy lamp light amount or the correction amount thereof and the corresponding value of the photoconductor temperature is stored, and based on this relationship, the charging potential or the correction amount thereof and the corresponding value of the photoconductor temperature are used to determine the copy lamp light amount. Alternatively, it is a means for calculating the correction amount.

According to a fourth aspect of the present invention, in the process control apparatus according to the first aspect or the second aspect, there is provided means for detecting a corresponding value of the photoconductor film thickness, and the arithmetic means is the charging means. Potential or its correction amount,
A relationship between the light amount of the copy lamp or its correction amount and the corresponding value of the photoconductor film thickness is stored, and based on this relationship, the charging potential or the correction amount thereof and the corresponding value of the photoconductor film thickness are copied. It is characterized in that it is means for calculating the lamp light amount or its correction amount.

According to a fifth aspect of the present invention, in the process control apparatus according to the first aspect, means for setting one of a plurality of copy modes such as a normal mode and a photo mode, and a means for setting each copy mode are provided. And a means for setting different charging potentials, and the computing means is provided for each copy mode.

According to a sixth aspect of the present invention, in the process control apparatus according to the first aspect, the arithmetic means includes a correction amount of the charging potential, a correction amount of the copy lamp light amount, and a charging potential of the photoconductor. The relationship between the charging potential and the correction level is stored based on this relationship.
And means for calculating a correction amount of the copy lamp light amount from the charged potential level of the photoconductor.

[0017]

In the process control apparatus according to the first aspect of the present invention, the correction amount of the copy lamp light amount is obtained by the calculation means based on the correction amount of the charging potential of the photoconductor. When the photoconductor is exposed by adding the correction amount to the light amount of the copy lamp, the surface potential of the photoconductor is attenuated. The light intensity of the copy lamp at this time is a light intensity sufficient to reduce the surface potential to the developing bias potential or less when the surface potential of the photoconductor is equal to the charging potential, and when the photoconductor is exposed with the obtained copy lamp light intensity. The photoconductor is sufficiently attenuated to obtain a sufficient white background when toner is attached. When the surface potential of the photoconductor becomes equal to or lower than the development bias potential, the toner is attracted to the developing device side, so that the toner does not adhere to the surface of the photoconductor and a sufficient white background can be obtained. The surface of the photoconductor is stable when the temperature of the photoconductor is stable, or in the case of an image forming apparatus in which the photoconductor is provided with a heater or the like and the surface potential of the photoconductor hardly decreases due to the influence of the photoconductor itself. Potential = charging potential.

In the invention described in claim 2, the light quantity of the copy lamp is directly obtained from the charging potential.

In the process control device according to the third aspect, the light intensity of the copy lamp or the correction amount thereof is calculated based on the charging potential of the photoconductor or the correction amount thereof and the corresponding value of the photoconductor temperature. That is, the relationship between the charged potential of the photoconductor or its correction amount and the copy lamp light amount or its correction amount is corrected by the photoconductor temperature. Therefore, even if the surface potential of the photoconductor does not become equal to the charging potential due to the fluctuation of the photoconductor temperature, when the photoconductor is exposed to the required amount of light of the copy lamp, the photoconductor is sufficiently attenuated and the surface potential of the photoconductor is equal to the developing bias potential. It becomes the following.

Generally, in the case of an OPC photosensitive member, the surface potential decreases as the photosensitive member temperature lowers, and in the case of the Se photosensitive member, the surface potential increases due to the lower photosensitive member temperature. In this case, when the copy lamp light amount or the light amount correction amount is calculated on the assumption that the charging potential is equal to the surface potential, for example, in the case of an OPC photosensitive member, the surface potential decreases when the photosensitive member temperature decreases, resulting in overcorrection. In the case of the Se photoconductor, when the photoconductor temperature decreases, the surface potential rises, resulting in insufficient correction. In the third aspect, since the corresponding value of the photoconductor temperature is taken into consideration when the light intensity of the copy lamp is obtained, such overcorrection or undercorrection can be prevented.

In the process control device according to the fourth aspect, the copy lamp light amount or the copy lamp light amount correction amount is calculated based on the charging potential or the charging potential correction amount of the photoconductor and the corresponding value of the photoconductor film thickness. . That is,
The relationship between the charging potential of the photoconductor or its correction amount and the copy lamp light amount or its correction amount is corrected by the photoconductor film thickness, and the film thickness of the photoconductor changes over time. Even when the surface potential is not equal to the charging potential, when the photoconductor is exposed with the obtained light amount of the copy lamp, the photoconductor is sufficiently attenuated and the photoconductor surface potential becomes equal to or lower than the developing bias potential.

In the process control apparatus according to the fifth aspect, when different charging potential levels are set for each copy mode, a calculation means is provided for each copy mode. The charging potential level varies depending on the copying machine, but is set to about -800 V in the normal mode and about -500 V in the photographic mode, for example. In this way, when the charging potential level changes greatly, the slope of the light attenuation upon irradiation with light changes. For example, as shown in FIG. 1, the slopes of the light attenuation curve when the charging potential level is high and the light attenuation curve when the charging potential level is low are different. It is considered that such a change in inclination is due to a difference in electric field strength due to a difference in surface potential of the photoconductor.

When the slope of the light attenuation curve changes in this way,
Even if the correction amount (change amount) of the charging potential is the same, the correction amount (change amount) of the light amount required for light attenuation is different. For example, as shown in FIG. 1, if the charging potential is corrected by aV when the charging potential level is high, the correction amount of the light amount necessary for attenuating the surface potential of the photoconductor to the developing bias potential is b. On the other hand, when the charging potential level is low, the charging potential is a
When the V correction is performed, the correction amount of the light amount required to optically attenuate the surface potential of the photoconductor to the developing bias potential is c.
That is, the correction amount of the light amount required for light attenuation changes depending on the difference in the charging potential level.

According to the present invention, the light amount calculation means is provided for each copy mode, and by this means, an appropriate correction amount of the copy lamp light amount can be obtained even if the copy mode (charging potential level) changes.

In the process control apparatus according to the sixth aspect, the light quantity correction amount of the copy lamp is calculated based on the correction amount of the charging potential of the photoconductor and the charging potential level of the photoconductor. Therefore, regardless of the charging potential level of the photoconductor, the light quantity correction amount required to reduce the surface potential of the photoconductor to approximately the developing bias voltage or less is required.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a main part of an electrophotographic copying machine equipped with a process control apparatus according to an embodiment of the present invention. An image forming process section including the photoconductor 1 and an exposure apparatus 2 including a copy lamp 21. , And their control units, and the configuration of the document table 3 for placing a document.

The photosensitive member 1 is an OPC photosensitive member and has a thickness of 2 m.
The charge generation layer is uniformly applied to a thickness of 1 μm on an aluminum tube having a diameter of 100 m, a diameter of 100 mm and a length of 340 mm, and then a charge transport layer is applied uniformly to a thickness of 34 μm. The photoconductor 1 is provided with a drum heater so that the surface potential and the sensitivity of the photoconductor 1 can be kept constant even if the environmental conditions change to some extent. Around the photoconductor 1
A charging device 11, a developing device 12, a transfer device 13, a peeling device 14, a toner concentration sensor 15, a cleaner 16, a discharging lamp 17 and the like are arranged facing the photoconductor 1. The document table 3 is made of a transparent glass body on which a document is placed. The exposure device 2 includes a copy lamp 21, a mirror 22, ..., A lens 23, and reflects light reflected from an original placed on the original table 3 to the photoconductor 1 via the mirror 22 ,. And lead.

The CPU 4 is an image forming process unit or exposure device 2.
Is a control unit for controlling. A copy mode, a copy start command, etc. are input to the CPU 4 from the operation unit 44, and the CPU 4
Executes copy processing and the like in response to this. CPU4
A detection value of the toner concentration sensor 15 is input to the toner concentration sensor 15 via the toner concentration detector 41. Based on this, the CPU 4 determines the charging potential of the charger 11 and the exposure light amount of the copy lamp 21, and outputs the value to the charging potential control unit 42 and the exposure light amount control unit 43. The charger 11 of this embodiment is of the strontron type, and the grid voltage is controlled as the charging potential. Further, the exposure light amount of the copy lamp 21 is controlled by the voltage applied to the copy lamp. The charging potential may be controlled by the voltage applied to the charger line, or the exposure light amount may be controlled by the duty ratio or the like.

Now, the procedure for controlling the charging potential will be described.

The control of the charging potential is executed, for example, during warm-up when the power of the copying machine is turned on, or when a certain period of time has elapsed after the power was turned on, thereby performing image quality correction in response to environmental changes. be able to.

When controlling the charging potential (during process control), first, three types of grid voltages including the initial grid voltage are set, and a toner patch is formed based on each grid voltage. For example, when the initial grid voltage is -800V, -750V, -800V, -8
10 cm x 3 grid voltages of 50 V each
A charged area of about 10 cm is formed, and toner is attached to this charged area to form a toner patch. At this time, the developing bias voltage is set to -200V. Then, the toner density sensor 15 detects the densities of the three formed toner patches. A reflection type infrared sensor is usually used as the toner concentration sensor 15, and the toner concentration detection unit 41 outputs the ratio of the reflected light of the surface of the photoconductor to the reflected light of the toner patch as the toner concentration to the CPU 4. .

On the other hand, the CPU 4 stores the toner density as an initial value when the initial grid voltage is set at the initial use of the photoconductor. For example, in the case of the above example, the reflected light of the toner patch when the grid voltage is set to −800 V and the developing bias voltage is set to −200 V is detected, and the reflected light of the surface of the photoconductor and the reflected light of the toner patch are detected. The ratio is stored in the CPU 4 as the toner concentration.

The process control is performed as described above.
From the relationship between the toner density when the grid voltage for each type is set and the toner density at the initial time, the correction amount of the grid voltage required for the current toner density to approximate the initial toner density is calculated, Further, the grid voltage is obtained, and the value is set as the grid voltage during image formation.

Next, a procedure for setting the light quantity of the copy lamp according to the grid voltage set as described above will be described.

An embodiment of claim 1 will be described.

When the drum heater is provided on the photoconductor 1, the temperature of the photoconductor is kept substantially constant, and the surface potential and sensitivity of the photoconductor 1 are kept constant. Therefore, the surface potential of the photoconductor is almost equal to the grid voltage. Can be obtained. However, even in that case, the image density changes due to a change in the charging potential of the developer depending on environmental conditions. This change in image density is corrected by adjusting the grid voltage, which has nothing to do with the original cause. Therefore, the density of the white part changes.

This will be specifically described. Now, consider a case where the grid voltage is set to -700V and a case where the grid voltage is set to -800V by the correction of the charging potential. When the surface temperature of the photoconductor is stable, these charging potentials become the surface potential of the photoconductor as it is. FIG. 3 shows optical attenuation when the grid voltage is set to −700V, and −8.
These are the results of examining the light attenuation when set to 00V, and the photoreceptor surface potential when the photoreceptor was exposed while changing the copy lamp voltage after the charging treatment was examined. In addition,
The photoconductor 1 is irradiated with the light of the copy lamp 21 reflected by the standard white plate, and the amount of the light is changed by changing the copy lamp voltage. Here, when the developing bias voltage is -200V, it is necessary to reduce the surface potential of the photoconductor to -200V or less by the exposure process in order to obtain a good white portion. As can be seen from the figure, the copy ramp voltage for this purpose is about "3" when the grid voltage is -700V, and about "4" when it is -800V. From this, it can be seen that when the grid voltage is changed, the exposure light amount needs to be changed if the density of the white portion is to be the same level.

Therefore, in this embodiment, the relationship between the correction amount of the grid voltage and the correction amount of the copy lamp light amount in order to obtain a white portion having a constant density was experimentally investigated. The result is shown in FIG. In the figure, the horizontal axis shows the correction amount of the grid voltage, and the vertical axis shows the correction amount of the copy lamp voltage. The grid voltage correction amount is indicated by a voltage value, and the copy lamp voltage correction amount is indicated by a ratio with respect to an initial value. This experimental result shows the correction amount of the copy lamp voltage for obtaining the amount of light necessary for the gray scale to start fogging, that is, for the surface potential to be substantially equal to the developing bias voltage.

A table or a function representing the result of this experiment is stored in the exposure light amount control unit 43, and when the charging potential is actually corrected, the correction amount of the copy lamp voltage is calculated based on the correction amount of the grid voltage. Then, the copy lamp voltage is calculated based on the obtained value. This makes it possible to form an image having sufficient brightness (whiteness). In this case, the calculation means based on the experimental result, that is, the experimental result table or function is previously stored in the exposure light amount control unit 43
In the process control, it is only necessary to form the toner patch for obtaining the grid voltage at the time of the process control, and the time required for the process control can be shortened and the device configuration can be simplified. That is, if the amount of exposure light for the white portion is set each time the process control is performed, a white standard plate and a control program therefor are required, and time for the processing is also required. However, if the experimental result table or the function is obtained in advance and stored, those are unnecessary.

An embodiment of claim 3 will be described.

As described above, the photoconductor of this embodiment is provided with the drum heater and is controlled so that the photoconductor temperature becomes constant. However, even with this control, a slight temperature change is observed. In this embodiment, the correction is performed.

FIG. 5 is a diagram showing the relationship between the environmental temperature and the surface temperature of the photoconductor 1, and FIG. 6 is a diagram showing the relationship between the photoconductor temperature and the surface potential of the photoconductor. As can be seen from these figures, the temperature of the photoconductor changes due to the change of the environmental temperature, which changes the surface potential of the photoconductor. FIG. 7 is a diagram showing a light decay curve when the surface potential of the photoconductor is −670 V (23 ° C.) and a light decay curve when the surface potential of the photoconductor is −700 V (30 ° C.). When the surface potential changes due to changes in temperature, the light decay curve also changes. In this case, when the grid voltage of the charger and the copy lamp voltage are corrected by the process control as shown in the above embodiment, the correction of the grid voltage is used to correct the fluctuation of the surface potential due to the change of the photoconductor temperature. As a result, the copy lamp voltage is overcorrected or undercorrected. In order to prevent this, in this embodiment, the ambient temperature is detected as a value corresponding to the surface temperature of the photoconductor, and the copy lamp voltage is corrected based on the result.

The sensor for detecting the ambient temperature is installed on the main substrate of the copying machine or the like at a place where the temperature rise is very small and detects a value close to the actual ambient temperature. FIG. 8 is a diagram showing the relationship between the environmental temperature and the copy lamp voltage correction amount. The copy lamp voltage correction ratio represents the correction ratio of the copy lamp voltage when the grid voltage is increased by 100V,
The actually required correction amount of the copy lamp voltage can be obtained by the following formula: actual correction amount = correction amount when 100 V is increased / 100 × grid voltage correction amount.

Therefore, the corrected copy lamp voltage is: corrected copy lamp voltage = actual correction amount × uncorrected copy lamp voltage.

When the grid voltage is reduced, it can be obtained by multiplying the reciprocal of the copy lamp voltage. At the time of actual control, the relationship shown in FIG. 8 is made into a table shape and stored in the exposure light amount control unit 43, and after the copy lamp light amount correction amount is obtained, the copy lamp light amount can be obtained using the above formula.

By thus correcting the copy lamp voltage according to the ambient temperature, the target copy image quality could be obtained even under the environment of 5 ° C.

In this embodiment, the ambient temperature is detected because the ambient temperature corresponds to the temperature of the photoconductor, but the temperature of the photoconductor itself may be detected.

An embodiment of claim 4 will be described.

In the above embodiment, the image quality change due to the short-term factor can be corrected, but the image quality change due to the long-term factor due to the photoconductor film reduction cannot be corrected. Therefore, the control for correcting the image quality change due to the film reduction will be described.

As the film thickness of the photoconductor 1 decreases, the electric field strength of the photoconductor changes. For this reason, the slope of the light attenuation curve changes, and the above-described correction of the lamp voltage cannot be performed sufficiently. Therefore, as shown in FIG. 9, the correction amount of the copy lamp voltage is obtained according to the film thickness of the photoconductor.
This relationship is obtained experimentally, and the copy lamp voltage correction amount on the vertical axis is the same as in FIG. 8 described above, and the copy lamp voltage can be obtained by the equation.

At the time of actual correction, the photoconductor film thickness is predicted by monitoring the photoconductor rotation time and the like. Then, the relationship shown in FIG. 9 is stored in a table shape,
By using the equation, the copy lamp voltage is corrected according to the rotation time of the photoconductor.

In the above embodiment, the correction amount of the copy lamp light amount is obtained based on the correction amount of the charging potential of the photoconductor, but the copy lamp light amount may be obtained directly from the charging potential. Direct copy lamp light intensity is obtained by finding the light intensity of the copy lamp corresponding to the charging potential and correcting it with the corresponding value of the photoconductor temperature (environmental temperature) and the corresponding value of the photoconductor film thickness (photoconductor rotation time). Can be asked.

An embodiment of claim 5 will be described.

Normally, the grid voltage level is determined by the type of copying machine and the copy mode (normal mode, photo mode, etc.) set in the copying machine. When these copy modes are input from the operation unit 44 shown in FIG. 2, the charging potential level is determined according to the input copy mode. For example, as shown in FIG. 10, the grid voltage in the normal mode is -800V and the grid voltage in the photo mode is -500V. This difference in grid voltage level results in a difference in surface potential level of the photoconductor. As mentioned above, when the surface potential level of the photoconductor changes, when the correction amount of the copy lamp light amount is calculated from the correction amount of the charging potential, the correction amount of the copy lamp light amount does not become the same even if the correction amount of the charging potential is the same. Is. Therefore, in this embodiment, the relationship between the correction amount of the charging potential and the correction amount of the copy lamp light amount is stored for each copy mode, and the correction amount of the copy lamp light amount is obtained based on the relationship.

FIG. 11 is a diagram showing the relationship between the grid voltage correction amount and the copy lamp voltage correction amount in each of the normal mode and the photographic mode. This experiment is a result of changing the copy lamp voltage so that the brightness (whiteness) of the copy at that time is increased or decreased with reference to the grid voltage at the initial time of each mode. As can be seen from the figure, the inclination greatly changes between the normal mode and the photo mode. The relationship between the grid voltage correction amount and the copy lamp voltage correction amount for each mode is stored in the exposure light amount control unit 43 in advance, and good control can be performed by obtaining the copy lamp light amount for each mode during process control. it can.

An embodiment of claim 6 will be described.

In this embodiment, the correction amount of the copy ramp voltage with respect to the grid voltage correction amount is changed according to the grid voltage level instead of the change in each mode.

FIG. 12 shows experimentally obtained results, where the horizontal axis represents the voltage level of the grid voltage and the vertical axis represents the copy lamp voltage correction amount. The copy lamp voltage correction amount on the vertical axis is the same as the copy lamp voltage correction amount shown in FIG. 8 described above, and the copy lamp voltage can be obtained by the equation. Then, the relationship shown in FIG. 12 is stored in a table shape, and the copy lamp voltage is calculated by the table and the formula.

By performing the correction according to the voltage level as described above, it is possible to perform the correction regardless of the mode in which any voltage level is set. Further, even when the grid voltage is changed for density correction, the copy lamp voltage can be corrected by using this relationship.

[0061]

According to the first and second aspects of the present invention, the density of black (toner adhering portion) of the image is controlled so that a clear density is obtained by correcting the charging potential, and the density of white (toner non-adhering) is controlled. Density) is controlled so that a sufficient white color can be obtained by correcting the irradiation light amount so that the surface potential of the photoconductor becomes equal to or lower than the developing bias potential. As a result, a high-quality image with high contrast can be obtained. Further, since the calculation means for obtaining the copy lamp light amount or its correction amount is stored in advance, it is possible to obtain the copy lamp light amount or its correction amount by simply obtaining the charging potential of the photoconductor or its correction amount. This has the advantage of simplifying the process for obtaining the lamp light quantity.

According to the third aspect of the invention, since the light quantity computing means is corrected according to the corresponding value of the photoconductor temperature, even when the surface potential of the photoconductor changes with the photoconductor temperature. Appropriate light amount correction will be performed.
In particular, good correction can be performed even when the temperature is extremely low or high.

According to the invention described in claim 4, since the light quantity correcting means is corrected by the film thickness of the photoconductor, the light quantity of the copy lamp can be corrected according to the change of the light attenuation state with time. it can.

According to the fifth aspect of the present invention, when the charge potential level is set for each image forming mode, even if the photo-attenuation state of the photoconductor surface potential is changed by the charge potential level, each mode is changed. Since the light amount calculation means is provided for each, an appropriate light amount corresponding to the mode can be obtained.

According to the sixth aspect of the present invention, since the light amount correction means is corrected by the charging potential level of the photoconductor, even when the electric field strength changes depending on the charging potential level of the photoconductor, a stable copy lamp light amount can be obtained. Corrections can be made.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the action of claims 5 and 6, showing a light attenuation state when the surface potential of a photoconductor changes.

FIG. 2 is a block diagram of a main part of a copying machine to which the present invention is applied.

FIG. 3 is a diagram according to the embodiment of claim 1, showing a state of optical attenuation.

FIG. 4 is a diagram according to the embodiment of claim 1, showing a relationship between a grid voltage correction amount and a copy lamp voltage correction amount.

FIG. 5 is a diagram according to an embodiment of claim 3, showing the relationship between the environmental temperature and the photosensitive member temperature.

FIG. 6 is a diagram according to an example of claim 3 and shows a relationship between a photosensitive member temperature and a surface potential.

FIG. 7 is a diagram according to an embodiment of claim 3, showing a state of light attenuation when the temperature changes.

FIG. 8 is a diagram according to an embodiment of claim 3, showing the relationship between the environmental temperature and the copy lamp voltage correction amount.

FIG. 9 is a diagram according to an embodiment of claim 4 and shows a relationship between a photoconductor film thickness and a copy lamp voltage correction amount.

FIG. 10 is a diagram according to an embodiment of claim 5 and shows an example of setting a grid voltage level and a copy lamp voltage level for each mode.

FIG. 11 is a diagram according to an embodiment of claim 5 and shows a relationship between a grid voltage correction amount and a copy lamp voltage correction amount for each mode.

FIG. 12 is a diagram according to an embodiment of claim 6 and shows a relationship between a grid voltage level and a copy lamp voltage correction amount.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kunio Ohashi, 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Prefecture Within the corporation

Claims (6)

[Claims] 1. A means for detecting the density of a toner image by charging the surface of a photoconductor to which toner is attached, and charging the photoconductor required to set a density detection value of the toner image to a predetermined value. A means for obtaining a correction amount of the potential, and a correction of the light intensity of the copy lamp necessary for attenuating the surface potential of the photoconductor to a level below the developing bias potential, when the charging potential considering the correction amount is used as the surface potential of the photoconductor. Quantity and
A process control device comprising: a calculation unit that stores a relationship with a correction amount of the charging potential and calculates a correction amount of a copy lamp light amount from the correction amount of the charging potential. 2. Means for detecting the density of the toner image by charging the surface of the photoconductor to which toner is attached, and charging the photoconductor necessary to set the density detection value of the toner image to a predetermined value. Means for obtaining potential, and storing the relationship between the charging potential and the copy lamp light amount necessary for attenuating the surface potential to below the developing bias potential when the charging potential is the surface potential of the photoconductor. And a calculation unit that calculates the light intensity of the copy lamp from the charging potential. 3. The process control device according to claim 1, further comprising means for detecting a corresponding value of the photoconductor temperature, wherein the arithmetic means is the charging potential or its correction amount, and the copy. The relationship between the lamp light amount or its correction amount and the corresponding value of the photoconductor temperature is stored, and based on this relationship,
A process control device, which is means for calculating a light intensity of a copy lamp or a correction amount thereof from a corresponding value of the charging potential or a correction amount thereof and the photoconductor temperature. 4. The process control device according to claim 1, further comprising: a means for detecting a corresponding value of the photoconductor film thickness, wherein the computing means includes the charging potential or its correction amount, The relationship between the copy lamp light amount or its correction amount and the corresponding value of the photoconductor film thickness is stored, and based on this relationship,
A process control device, which is means for calculating a light intensity of a copy lamp or a correction amount thereof from a corresponding value of the charging potential or a correction amount thereof and the photoconductor film thickness. 5. The process control device according to claim 1, wherein a means for setting one of a plurality of copy modes such as a normal mode and a photo mode, and a charging potential of a different level according to each copy mode are set. A process control device comprising: setting means; and the calculating means for each of the copy modes. 6. The process control device according to claim 1, wherein the arithmetic unit stores a relationship between the correction amount of the charging potential, the correction amount of the copy lamp light amount, and the level of the charging potential of the photoconductor. Then, the process control device is a means for calculating the correction amount of the charging potential and the correction amount of the copy lamp light amount from the charging potential level of the photoconductor based on this relationship.