JPH06118757A - Image stabilizing method - Google Patents

Abstract

PURPOSE:To always obtain a sharp stable copied image by obtaining information with respect to the sensitivity of a photosensitive body based on a toner image formed on the photosensitive body and setting the quantity of light with which the photosensitive body is irradiated with the sensitivity information. CONSTITUTION:An optical sensor 12 detects the reflectance of the toner image on the photosensitive body as the density of the toner image. For turning this toner concn. into the sensitivity information of the photosensitive body, first, it is electrified with a prescribed voltage to impart a constant surface potential to the photosensitive body, the illuminating unit of an optical system 6 is moved under a standard white sheet 15 and a copy lamp 6a is successively turned on with various kinds of voltages, so that the electrostatic latent image patterns of different surface potentials are formed on the photosensitive body and actuarized to measure the reflectance by the optical sensor 12. Then, the quantity of light with which the photosensitive body is irradiated such as the light quantities of a destaticization lamp and a blank lamp. Thus, the drop of the surface potential can be prevented under low temperature environment and consecutive processing as well, especially in the initial stage of the use of the photosensitive body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention improves image quality in an electrophotographic image forming apparatus, such as an electrostatic copying machine.
The present invention relates to an image stabilizing method for stabilizing.

[0002]

2. Description of the Related Art A copying process of an electrostatic copying machine includes a charging process for imparting photosensitivity to a photoconductor and an exposure process for forming a latent image by forming an image of a document on the photoconductor. A latent image erasing step of erasing the electrostatic latent image in the non-image area (unnecessary portion),
A developing process for developing the latent image with toner particles, a transfer process for transferring the visualized toner image onto a transfer paper, and a cleaning process for cleaning the residual toner on the photoconductor after the transfer. And a static elimination step for erasing the electrostatic latent image on the photoconductor. If the amount of blank lamp light or static elimination light in the latent image erasing process or static elimination process is less than the required amount, the non-image area (unnecessary part) or the electrostatic latent image of the previous image cannot be erased and toner adheres. As a result, not only an afterimage or an image in an extra area appears and becomes a very unsightly copy image, but also extra toner is consumed or the inside of the machine is contaminated with toner. Therefore, it is desired that the blank lamp light amount and the charge eliminating lamp light amount in the copying machine be set to at least a light amount capable of erasing the electrostatic latent image so that development is not performed. Specifically, it is set to about 4 to 8 times the half-exposure amount (the amount of light required to reduce to 1/2 of the surface potential of the photoconductor).

The charging characteristics of the photoconductor largely depend on the ambient temperature. In particular, in the case of an OPC photosensitive member, the drift mobility of photocarriers generated in the photosensitive layer by exposure is small, the temperature dependence is large, and the lifetime is long, so that the surface potential decreases in a low temperature environment. large. This is because the photocarriers generated in the latent image erasing step and the charge removing step survive to the next charging step, become easy to move due to the electric field applied in the charging step, and cancel the supply potential due to corona discharge or the like. In this way, the potential drop phenomenon largely depends on the degree of photocarrier mobility and temperature dependence, the lifetime of photocarriers, the total number of photocarriers (the amount of light of the blank lamp and the discharge lamp), the film thickness of the photoconductor, The lower the mobility, the longer the lifetime, the higher the blank lamp light amount or the static elimination lamp light amount, and the thicker the film thickness, the greater the decrease in the surface potential.

On the other hand, with the OPC photoconductor, the film thickness of the photoconductor gradually changes due to mechanical stress due to the magnetic brush in the developing process and the cleaning blade in the cleaning process as the number of copies increases. phenomenon). Along with this, the photosensitivity of the photoconductor decreases at a constant rate as the film thickness decreases. Normally the film thickness is 100K
It is reduced by an amount of about 3 to 6 μm per copy. This amount of film reduction is the kind and amount of components contained in the transfer paper used,
Furthermore, it has been known that it depends on the thickness of the magnetic brush of the developer and the type and amount of the external additive material of the toner. The photosensitivity of the photoconductor decreases in proportion to the film thickness 0.6 to 0.9 power in response to such film reduction. For this reason, the life of the photoconductor is extended,
In order to increase the sensitivity, the film thickness of the photoconductor is designed to be thicker.

[0005]

For the above reasons,
In a long-life, high-sensitivity OPC photosensitive member, the film thickness of the photosensitive layer must be thick (35-40 μm).
Further, when the photoconductor is replaced, that is, when the life of the photoconductor is approaching, the photosensitivity of the photoconductor is reduced to 50 to 70% of the initial level due to film loss. In the copying machine, the blank lamp light amount and the charge eliminating lamp light amount at the initial stage are set so that sufficient afterimage generation can be prevented even during such a photoconductor life period. That is, when the photosensitivity is lowered at the end of the life of the photoconductor, the light amount is set to be 4 to 8 times the sufficient half exposure amount. The amount of blank lamp light and the amount of static elimination lamp light required during the life of the photoconductor correspond to 1.5 to 2.0 times the amount of light required in the initial stage of the photoconductor (irradiated with more light than necessary).

Here, the film thickness of the photosensitive layer is still large in the early stage of the photoconductor, and the surface potential drop becomes very large. Further, in the initial stage of the photoconductor, since an unnecessarily large amount of static elimination light is irradiated as described above, the influence of the environmental temperature change is amplified, the charging characteristics of the photoconductor are greatly deteriorated, and the environment is low (5 ° C). 150-200V compared to under normal temperature environment
Had caused a decrease in surface potential. Such a decrease in surface potential causes a decrease in copy image density, and only an unclear image with a small contrast can be obtained. Further, when the copying process is continuously carried out, the optical carriers are accumulated, but the accumulation of the optical carriers is also promoted by the excessive irradiation of light as described above in the initial stage of the photoconductor. , The surface potential was greatly reduced.

An object of the present invention is to always provide a clear and stable copy image.

[0008]

The present invention can be summarized as follows.
A toner image or an electrostatic latent image is formed on the photoconductor, information corresponding to the sensitivity of the photoconductor is obtained based on the toner image or latent image, and the light amount of the static elimination lamp or the blank lamp light is also obtained based on this sensitivity information. The amount of light to be applied to the photoconductor such as is set.

[0009]

According to the present invention, the discharge lamp light amount and the blank lamp light amount are set based on the detected sensitivity information of the photosensitive member, and the discharge lamp light amount and the blank lamp light amount are appropriately set during the use of the photosensitive member. Go on. That is, a corresponding amount of light is set at the beginning of use of the photoconductor (usually, a lower amount of light is set), and a corresponding amount of light is set even after the life of the photoconductor (usually, a higher amount of light is set than at the initial stage). ). Therefore, especially at the initial stage of use of the photoconductor, the problem that the surface potential is significantly lowered even in a low temperature environment or during continuous copying does not occur.

[0010]

1 is a schematic sectional view of a copying machine for explaining the present invention.

Reference numeral 1 is a photoconductor having a thickness of 2 mm and a diameter of 100.
mm, 340 mm in length, the charge generation layer is uniformly applied on the aluminum tube to a thickness of about 0.5 μm, and then the charge transport layer is uniformly applied to a thickness of about 34 μm. It is the body. 2 is a charger, linear type 70μ
m discharge electrode made of tungsten oxide wire, and a stainless steel shield electrode surrounding the discharge electrode,
Also, it is a scorotron charger having a screen grid electrode made by etching a stainless material having a plate thickness of 0.1 mm. CPU for this grid electrode
A high-voltage power supply 4 whose output is variable based on a signal from 3 is connected. Reference numeral 5 denotes a blank lamp in which 60 LEDs each having a central emission wavelength of 660 nm are arranged at intervals of 5 mm along the photosensitive member axial direction. The blank lamp 5 is used for erasing an unnecessary area of the electrostatic latent image and for forming an image when the photoconductor sensitivity is measured. Reference numeral 6 denotes an optical system for irradiating a document on a document table or a standard white plate, which will be described later, with light and forming an image of reflected light on a photoconductor. The optical system 6 is provided with a moving unit including a copy lamp 6a so as to be movable along the document table, and the document on the document table is scanned by this movement. The AE sensor 16 is located at the position of the copy lamp 6a.
Is provided. The AE sensor detects reflected light from a document or a standard white plate described later. Reference numeral 7 is a sensor for detecting the surface potential of the photoconductor. Reference numeral 8 is a developing device for developing the electrostatic latent image formed on the photoconductor with toner. 9
Is a transfer charger for transferring the toner image on the photoconductor to the transfer paper 10. The toner image transferred to the transfer paper is heated and fixed by the fixing device 11 and discharged to the outside of the device. An optical sensor 12 detects the reflectance of the toner image on the photoconductor as the density of the toner image. A cleaner 13 removes the toner on the photoconductor. Reference numeral 14 is a discharge lamp, which erases the residual potential on the photoconductor. 1
Reference numeral 5 is a standard white plate. As one method for forming a toner image or an electrostatic latent image, the image of the standard white plate 15 is printed on the photoconductor. When detecting the potential of the electrostatic latent image, this is left as it is. When detecting the density of the toner image, the developing device 8 visualizes the toner image to form a toner image, and the optical sensor 12 detects the density. ing. The optical sensor 12 uses an infrared light emitting diode having a wavelength of 890 nm as a light emitting portion, irradiates the photoconductor with the infrared light emitting diode, and receives the reflected light by a phototransistor (see FIG. 2).

Surface sensor 7, optical sensor 11 and AE
The outputs of the sensor 16 are amplifiers 21, 23, 25, respectively.
It is amplified by and is inputted to the CPU 3 through the A / D converters 22, 24 and 26. CPU
3 controls the blank lamp drive circuit 31, the discharge lamp drive circuit 32, and the copy lamp drive circuit 34 according to these input information for process control so that optimum process control can be performed. The blank lamp drive circuit 31 and the static elimination lamp drive circuit 32 are PW from the CPU.
The M signal is input and converted into an analog level by integrating the M signal, the drive duty is changed according to this level, and the emitted light amount can be variably controlled. The copy lamp drive circuit 34 receives the PWM signal from the CPU, converts the PWM signal into an analog level by integrating the PWM signal, and applies a voltage to the copy lamp 6a according to this level so that the emitted light amount can be variably controlled. Has become. The developing bias applied to the magnet roller of the developing device 8 is supplied from the driving power supply 33.

In the copying machine configured as described above,
A procedure for detecting the sensitivity information of the photoconductor and controlling the light amount of the blank lamp, the static elimination lamp, etc. based on the detected value will be described.

<Detection of Sensitivity Information> As a method of detecting the sensitivity information of the photoconductor, for example, a method of detecting the toner density (reflectance of toner) shown in to and a method of detecting the surface potential shown in is there.

In this example, when toner is formed on the photoconductor and the density (reflectance of toner) is detected, and a predetermined reflectance (80% = reflectance of an image corresponding to a standard white plate) is obtained. Copy lamp voltage is used as the sensitivity information of the photoconductor.

When the toner density is used as the sensitivity information, a toner image is formed on the surface of the photoconductor and the density is detected. First,
In order to apply a constant surface potential to the photoconductor, charging is performed with a predetermined screen grid bias voltage (850V). The photoconductor used was a new one, and the film thickness was 35 μm. Next, the illumination unit of the optical system is moved below the standard white plate so that the standard white plate can be imaged on the photoconductor. The copy lamps are sequentially turned on with various voltages (AC60V to 7V).
2V), electrostatic latent image patterns having different surface potentials are formed on the photoconductor. The latent image of the part other than this pattern should be erased by turning on the blanching lamp appropriately to prevent the toner from adhering to the unnecessary part in the next development process, so as not to cause the toner consumption or toner scattering. Is desirable. After passing through the developing process at a predetermined developing bias voltage (200 V), the reflectance of the visualized toner pattern is measured by a reflective optical sensor. FIG. 3 shows the state in which the photoconductor is developed. The toner pattern has a width of 45 mm and a length of 50 mm, and is formed as four different images.

FIG. 4 shows the copy lamp voltage for toner pattern formation on the horizontal axis and the reflectance measurement result on the vertical axis. From this result, in the early stage of the photoconductor,
It can be seen that a reflectance of 80% is obtained when the copy lamp voltage is 63.0V. This data is stored in the CPU 3 and used as the initial sensitivity of the photoconductor. Next, a photoreceptor subjected to a life test of 250 k sheets is mounted, a toner pattern is formed in the same manner as above, and the reflectance thereof is measured. The obtained results are shown together in FIG. At this time, the copy lamp voltage at which a reflectance of 80% is obtained is 68.1V. It can be seen that this difference in copy lamp voltage corresponds to the difference in sensitivity between the initial stage and after 250 klife, and is lower than the initial photoconductor sensitivity after 250 klife. In this way, the relative sensitivity of the photoconductor can be measured. The film thickness of the photoconductor subjected to this life test was 25.0 μm.

The above is an example in which the photosensitivity of the photoconductor is detected by measuring the copy lamp voltage for obtaining a predetermined toner reflectance. With this method, the change over time of the copy lamp itself (depending on life) Even if the voltage is the same, the light intensity will decrease).

In order to detect the photosensitivity of the photoconductor by eliminating the change with time of the copy lamp, the reflected light of the standard white plate is detected by the original light receiving sensor at the same time when the copy lamp is turned on at various voltages. Capture the output to the CPU,
Use that value instead of the copy ramp voltage. FIG. 5 shows the output of the document light-receiving sensor (value digitally converted to 8 bits) on the horizontal axis and the reflectance measurement result on the vertical axis. The method for forming the toner pattern in this case is the same as that in.

From this result, it is understood that the reflectance of 80% of the toner pattern is obtained when the output of the original light receiving sensor is 75. This data is stored in the CPU and used as the initial sensitivity of the photoconductor. Life test 25
A 0K-sheet photoconductor is mounted, a toner pattern is formed in the same manner as above, and the reflectance is measured. The obtained results are shown together in FIG. At this time, the output of the document light-receiving sensor, which can obtain a reflectance of 80% for recognizing that the toner pattern is white, is 88, which is lower than the initial photoconductor sensitivity.

Another method for measuring the photosensitivity of the photoconductor is as follows. , Used a standard white plate and a copy lamp to form a toner pattern on the surface of the photoreceptor, but this method uses a blank lamp without using the standard white plate. In the blank lamp, 60 LEDs each having a central emission wavelength of 660 nm are arranged at intervals of 5 mm. For the above purpose, a drive circuit is formed so that the light amount can be variably controlled at the central portion of 45 mm. The light amount varying means is provided by supplying drive power by duty control as in the charge elimination lamp. Then, the duty of the blank lamp at the time of forming the toner pattern with which a predetermined amount of reflected light (80%) is obtained is detected as the sensitivity of the photoconductor at that time. This method is as follows.

First, in order to apply a constant surface potential to the photoconductor, a predetermined screen grid bias voltage (850
V) is charged. The photoconductor used is a new one having a film thickness of 35 μm. Next, the LED of 45 mm in the central portion of the blank lamp forms an electrostatic latent image pattern of different surface potential on the photoconductor while changing the duty, and the latent image other than this pattern is erased by turning on the blank lamp. To do. Then, a predetermined developing bias voltage (20
After passing through the development process at 0 V), the same as above,
The toner pattern of FIG. 3 is formed. FIG. 6 shows the result of measuring the reflectance of the toner pattern (only in the initial stage) with a reflective photosensor. In FIG. 6, the horizontal axis represents the duty of the blank lamp and the vertical axis represents the reflectance measurement result of the toner pattern. From this figure, it can be seen that in the initial stage of the photoconductor, a reflectance of 80% is obtained when the blank lamp duty is 35%. Similarly, the blank lamp duty after the life (for example, after 250 k life) can be detected as the sensitivity information.

Further, in the above methods (1) to (4), a toner pattern is formed on the surface of the photoconductor, and the reflectance is measured to obtain the change in the photosensitivity of the photoconductor.
The surface potential of the electrostatic latent image formed on the surface of the photoconductor may be measured, and the rate of change in photosensitivity may be calculated based on the measured potential. That is, in the above methods (1) to (4), the toner is adhered onto the electrostatic latent image formed by exposure and the reflectance thereof is measured, but the toner is not adhered (at a stage before passing through the developing process), The surface potential of the latent image is measured by the surface potential sensor. FIG. 7 shows the result of measuring the surface potential of the photoconductor before passing through the developing step, and at the initial stage of the photoconductor, the surface potential corresponding to white (approximately 2
The copy lamp voltage at which 50 V) is obtained is 63.0 V.

Further, the copy lamp voltage at which the surface potential corresponding to white is obtained after the life of 250 k sheets is 68.
It is 1V.

Similarly, also in the method of setting the light amount of the static elimination lamp of, the information corresponding to the photoconductor sensitivity can be obtained by measuring the surface potential of the latent image by the surface potential sensor before the toner is attached. Note that FIG. 8 shows the result when an electrostatic latent image is formed in the same process as, and shows the relationship between the reflected light amount of the original and the surface potential of the photoconductor. Further, FIG. 9 shows the result when an electrostatic latent image is formed by a blank lamp as in the step of FIG. 9, and shows the relationship between the blank lamp drive duty and the photoreceptor surface potential.

<Correction of Light Amount Irradiated on Photoreceptor> (1) Correction of Light Amount of Static Elimination Lamp The light amount of the static elimination lamp is performed by duty-controlling the electric power supplied to the static elimination lamp. It is measured in advance and is as shown in FIG. The method of measuring the sensitivity change of the photoconductor and determining the light quantity of the charge elimination lamp from the result is performed as follows according to the method of measuring the sensitivity information.

Detecting Copy Lamp Voltage as Sensitivity Information In a halogen lamp used as a copy lamp of a copying machine, the change in the amount of emitted light is proportional to the applied voltage ratio approximately 3.19.

Charge elimination lamp light amount increase rate = sensitivity change rate of photoconductor = (changed copy lamp voltage / initial copy lamp voltage) ^3.19 . For example, when the initial copy lamp voltage is 63.0
V, the copy lamp voltage after 250k life is 68.1V
If it is, increase rate of static elimination lamp light quantity = (68.1 / 63.0)
It becomes ^3.19 .

The CPU knows the initial sensitivity of the photoconductor and the sensitivity change in life, calculates the charge removal lamp increase rate to correct the photoconductor sensitivity change from these changes, determines the charge removal lamp light quantity, and controls it.

When the amount of reflected light from the standard white plate is detected as sensitivity information The document light receiving sensor used in the present invention has a characteristic that the rate of change of the output voltage is equal to the rate of change of the amount of received light. That is, if the light quantity doubles, the output voltage also doubles.

Charge elimination lamp light amount increase rate = sensitivity change rate of photoconductor = output value of original light receiving sensor after change / initial output value of original light receiving sensor. For example, when the amount of reflected light at the initial stage (output value of the document light receiving sensor) is 75 and the amount of reflected light after 250 klife is 88, then: = (88/75)

When the duty of the blank lamp is detected as the sensitivity information, the charge removal lamp drive duty = blank lamp drive duty change rate × initial charge removal lamp drive duty, and the blank lamp drive duty change rate = blank lamp drive duty / initial blank It becomes the lamp drive duty.

(2) Correction of Blank Lamp Light Quantity FIG. 11 shows the relationship between the blank lamp drive duty and the blank lamp light quantity. Based on this relationship, the light amount of the blank lamp is corrected in the same manner as the above-mentioned light correction lamp light amount correction.

<State after Irradiation Light Amount Correction> Next, an example of an experiment will be shown in the case where the amount of light applied to the photosensitive member is corrected as described above, and the device is used in a low temperature environment or continuously used.

(1) Experimental example in a low temperature environment The above copying system (a new photoconductor is used) was brought into an environmental test room, and the result of measuring the temperature dependence of the surface potential of the photoconductor is shown in FIG. Twelve. Even though the photoconductor has a thick film thickness (35 μm), the amount of light that the static elimination lamp, blank lamp, etc. expose to the photoconductor is kept to the minimum necessary, so the surface potential drops in a low temperature environment. It can be seen that the amount can be suppressed to about 50V. In the conventional method, a large amount of light (about 1.5 to 2.0 times the amount of light required at the initial stage) was given in anticipation of a decrease in the sensitivity of the photosensitive member even in the initial stage of the photosensitive member.
The surface potential decrease amount in a low temperature environment is 150 V to 200
V was extremely large.

(2) Example of continuous use experiment Further, FIG. 13 shows the result of measuring the transition of the photosensitive member surface potential during continuous use using this copying system. Even though the photoconductor is in the initial stage and has a large film thickness (35 μm), the amount of light for exposing the photoconductor to the static elimination lamp, blank lamp, etc. is minimized. It can be seen that the decrease amount of the surface potential can be suppressed to about 50V. In the conventional method, a large amount of light is generated even in the initial stage of the photoconductor (about 1.5 to about the required amount of light in the initial stage
2.0 times), the surface potential decrease is 100.
It was a very large value of V to 150V.

<Example of Control> In the copying machine, the above-described correction step (step of performing sensitivity measurement and correcting the light amount of the static elimination lamp and the light amount of the blank lamp) is performed, for example, every predetermined number of copies. For example, it is performed every 10 k. How often the correction process is performed depends on the amount of film loss of the photoconductor and the usage pattern of the copying machine, but it is preferably performed every 1 to 50 k sheets. Since it is not desirable to interrupt the copying operation and perform these correction steps in the interest of the user, the correction steps should be performed if the predetermined number of sheets have elapsed after the power switch was turned on. Alternatively, it is desirable that the process be performed when a series of copy jobs is completed after a predetermined number of sheets have passed. In this way, it is possible to execute the correction process without making the user feel uncomfortable.

FIG. 14 shows the result of the life test of the photoconductor in which the above-described charge eliminating lamp light quantity correction system is incorporated. In FIG. 14, the horizontal axis represents the number of copies, and the vertical axis represents the change in the sensitivity of the photoconductor and the change in the light amount of the discharge lamp. In the figure, the test was performed in a mode of repeating 999 sheets continuously between 0 to 100 k sheets, and in a mode of repeating three multi-copy sheets between 100 to 200 k sheets. 2 more
Recycled paper was used as the transfer paper in the repeating mode of continuous 999 sheets between 00 and 300 k sheets. In this recycled paper, calcium bicarbonate is used as an additive, and it is expected that the polishing effect on the photoconductor will be increased. For this test up to 300k sheets, the density of the copy image is sufficient for practical use, and the optimum amount of light from the static elimination lamp is always applied, so there is no afterimage (memory) and so on. I was able to get an image. In this way, instead of simply controlling the light amount of the static elimination lamp by the number of copies, by measuring the actual sensitivity change of the photoconductor and performing control based on the result, the type of transfer paper used and the copy used. Regardless of the pattern, it is possible to always provide an optimum light amount of the static elimination lamp, and it is possible to obtain an excellent copy image in which the afterimage does not always occur in the life of the photoconductor and the density does not decrease in a low temperature environment. If the light amount of the static elimination lamp is simply controlled by the number of copies, it is difficult to correctly control the change in the copying environment as described above, and in some cases it is overcorrected and the density is lowered in a low temperature environment. On the contrary, the correction may be too small, which may cause the afterimage.

Incidentally, even when an experiment was carried out by a copying machine incorporating a blank lamp light amount correction system, similarly good results could be obtained.

<Correction of Copy Lamp Light Amount> By the way, in the copying machine, process conditions such as developing bias are corrected while detecting the reflected light of the document so that the optimum copy image density can be obtained (charge potential of the photoconductor, etc.). It may be corrected)
This step is performed in real time during the copying process.
This is called an AE mode (automatic exposure mode).

When the AE mode is selected, the developing bias voltage is changed with respect to the output of the original light receiving sensor in the relationship shown in FIG. Point A in the figure is the original light receiving sensor output obtained by irradiating the standard white plate with the initial copy lamp voltage (63.0V), and point B in the figure is 50% of the output at this time.
The value of is set. This set value is appropriately determined so that an optimum reproduced image can be obtained by actually copying various originals in each copying system. By this method, a copy image having an optimum density can be obtained. As is apparent from FIG. 15, when the original has a high density, the developing bias voltage is set high, and when the original has a light density, the developing bias voltage is set low and the developing bias voltage is automatically set. It is controlled so that the optimum copy image can be obtained.

By the way, the copy lamp voltage is necessary in order to compensate for the decrease in the exposure light amount due to the contamination of the optical system (copy lamp, mirror, etc.) and the deterioration of the light source lamp, and the decrease in the sensitivity due to the film loss of the photoconductor. Will be increased accordingly. If this is not done, fog will occur on the white background of the copy due to insufficient exposure to the photoconductor, resulting in an unsightly and poorly copied image. For example, although the copy lamp voltage required at the initial stage of the photoconductor is 63.0V, the copy ramp voltage needs to be increased to 71.0V in order to give the photoconductor the same exposure amount as the initial stage after a certain life. As a result, it is possible to compensate for the decrease in the sensitivity of the photosensitive member, the contamination of the optical system, and the deterioration of the copy lamp.
By periodically performing such correction of the exposure light amount (for example, every 10 k sheets), it is possible to obtain a copy image having a constant brightness throughout the life of the photoconductor. However, when the copy lamp voltage is changed in this way, it is necessary to change the relationship shown in the figure. This is because the change in the copy lamp voltage is a change in consideration of both the exposure amount of the optical system and the change in the sensitivity of the photoconductor, whereas the relationship in FIG. 15 shows the relationship between the original density and the developing bias voltage. Because it is only.

As shown in FIG.
In order to change the relationship of 5, the following may be done. The sensitivity of the photoconductor is periodically measured, and the standard white plate is irradiated with the optimum copy lamp voltage obtained at that time to obtain the output of the document light receiving sensor. For example, for the original light receiving sensor output 75 obtained by irradiating a standard white plate with a copy lamp voltage of 63.0 V at the beginning, the optimum copy lamp voltage obtained by the sensitivity measurement is 71.0 V, and this voltage is the standard. Assuming that the output of the original light receiving sensor on the white plate is 151, the new relational expression of FIG. 9 is that point C in the figure is 151 and point D is 151 ×
0.5 = 75.5. However, since the horizontal axis original light receiving sensor output in FIG. 15 must be an 8-bit digitel value, it is rounded to a value of 76.
By doing so, even if the copy lamp voltage is changed during the life of the photoconductor, the automatic exposure system can obtain the same performance as that at the initial stage of the photoconductor.

[0044]

According to the present invention, since the light amount of the discharging lamp and the light amount of the blank lamp are appropriately set during the use of the photosensitive member, it is not necessary to set a high light amount in advance at the initial stage of the photosensitive member and it is always appropriate. The amount of light can be set. As a result, it is possible to prevent the photocarriers from being generated more than necessary, the surface potential of the photoconductor can be stabilized, and the image quality can be improved and stabilized.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a copying machine to which the present invention is applied.

FIG. 2 is a diagram showing a configuration of an optical sensor for detecting the reflectance of a toner image.

FIG. 3 is a diagram showing a state of a toner patch (electrostatic latent image patch) formed for photosensitive member sensitivity measurement.

FIG. 4 is a diagram showing the relationship between the reflectance of a toner patch and the voltage of an image forming copy lamp.

FIG. 5 is a diagram showing the relationship between the reflectance of a toner patch and the amount of reflected light from a standard white plate for image formation.

FIG. 6 is a diagram showing the relationship between the reflectance of a toner patch and the duty of a blank lamp for image formation.

FIG. 7 is a diagram showing the relationship between the surface potential of an electrostatic latent image and the voltage of an image forming copy lamp.

FIG. 8 is a diagram showing the relationship between the surface potential of an electrostatic latent image and the amount of reflected light from a standard white plate for image formation.

FIG. 9 is a diagram showing the relationship between the surface potential of an electrostatic latent image and the duty of an image forming blank lamp.

FIG. 10 is a diagram showing a relationship between a discharge lamp duty and a discharge lamp light amount.

FIG. 11 is a diagram showing a relationship between a blank lamp duty and a blank lamp light amount.

FIG. 12 is a graph showing the relationship between environmental temperature and photoreceptor surface potential.

FIG. 13 is a diagram showing the relationship between continuous copy time and photoreceptor surface potential.

FIG. 14 is a diagram showing a relationship between a change in the sensitivity of the photoconductor during the life of the photoconductor and a charge removal lamp duty corresponding to the change.

FIG. 15 is a diagram showing a developing bias setting curve in the AE mode.

Front page continued (72) Inventor Motoyuki Itoyama 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka

Claims (7)

[Claims] 1. A charging step for a photosensitive member, an image exposing step for forming a latent image, and a developing step. By sequentially performing these steps, a toner image is formed on the surface of the photosensitive member, An image stabilizing method characterized in that the reflection density of the toner image is detected, and the amount of light applied to the photosensitive member is set based on the detected reflection density. 2. A photosensitive member charging step and an image exposing step for forming a latent image. By sequentially performing these steps, an electrostatic latent image is formed on the surface of the photosensitive member and the electrostatic latent image is formed. The image stabilization method, comprising detecting the surface potential of the photoconductor, and setting the amount of light applied to the photoconductor based on the detected surface potential. 3. A photosensitive member charging step, an image exposing step for forming an electrostatic latent image, and a developing step. By sequentially performing these steps, a toner image is formed on the surface of the photosensitive member. ,
In addition to detecting the reflection density of the toner image, the amount of light from the optical system is detected during the image exposure step, and the amount of light to be applied to the photoconductor is set based on the detected reflection density and the amount of light in the optical system. Image stabilization method. 4. A photosensitive member charging step and an image exposing step for forming an electrostatic latent image. The electrostatic latent image is formed on the surface of the photosensitive member by sequentially performing these steps. In addition to detecting the surface potential of the latent image, the amount of light from the optical system is detected during the image exposure step, and the amount of light to be applied to the photoconductor is set based on the detected surface potential and the amount of optical system light. Image stabilization method. 5. A photosensitive member charging step, an image exposing step for forming an electrostatic latent image, and a developing step. These steps are sequentially performed to form a toner image on the surface of the photosensitive member. ,
In addition to detecting the reflection density of the toner image, the amount of light from the optical system is detected during the image exposure step, and the amount of light to be applied to the photoconductor is set based on the detected reflection density and the amount of light in the optical system. An image stabilizing method, which comprises detecting an image exposure light amount in an image exposure step for forming a latent image and controlling a developing bias voltage based on the image exposure light amount. 6. A photosensitive member charging step and an image exposing step for forming an electrostatic latent image. By sequentially performing these steps, an electrostatic latent image is formed on the surface of the photosensitive member. The surface potential of the latent image and the amount of light from the optical system during the image exposure step are detected, and the amount of light to be applied to the photoconductor is set based on the detected surface potential and the amount of light in the optical system. An image stabilizing method, which comprises detecting an image exposure light amount during an image exposure step for controlling the developing bias voltage based on the image exposure light amount. 7. The image stabilizing method according to claim 1, wherein the set amount of light applied to the photoconductor is given by a charge eliminating lamp or a blank lamp.