JPH0744063A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of forming image of uniform density irrespective of the causes of fluctuations even when dark decay on a photosensitive body film is fluctuated due to various causes. CONSTITUTION:A photosensitive drum 13 is provided with a base body 30 having electric conductivity and a photosensitive body film 12 formed on the surface of the base body 30. The photosensitive body film 12 is electrified by a main changer 14. The electrified photosensitive body film 12 is exposed by an optical device 15 and an electrostatic latent image is formed. The electrostatic latent image on the photosensitive body film 12 is developed by a developer 16. The level of dark decay on the photosensitive body film 12 is detected by a surface electrometer 26. The temperature of the photosensitive body film 12 is adjusted by a heater 24 in accordance with the level of the dark decay on the photosensitive body film 12 detected by the surface electrometer 26 and thus, the fluctuations of surface potentials due to the dark decay are compensated for. Further, in the case that the fluctuations of the surface potentials are not sufficiently compensated for by adjusting the temperature of this photosensitive body film 12, the fluctuations of the surface potentials are compensated for by adjusting the charged potential control means of the main charger 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using electrophotography, and more particularly to an image forming apparatus for forming an image by charging and exposing a single-layer organic photosensitive drum.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic technique has been actively developed as an electrostatic copying apparatus or a printing apparatus.

FIG. 10 is a system diagram of an image forming apparatus 1 using a conventional electrophotographic technique. The image forming apparatus 1 includes a rotatable photosensitive drum 3 having a photosensitive film 2 formed on the surface thereof,
A main charger 4 for uniformly applying a predetermined amount of electric charge to the photoconductor film 2, an optical device 5 for exposing the photoconductor film 2 to form an electrostatic latent image on the photoconductor film 2, and a photoconductor. A developing device 6 for developing the electrostatic latent image on the film 2, a transfer device 8 for transferring the toner image formed on the photoconductor film 2 onto the recording paper 7, and a toner remaining on the photoconductor drum 3 are removed. A cleaning device 9 having a cleaning blade for removing the charges remaining on the photoconductor drum 3 to set the surface potential of the photoconductor drum 3 to a predetermined uniform potential.
Equipped with 0 etc.

According to the image forming apparatus 1, the main charger 4 uniformly applies a predetermined amount of electric charge to the photoconductor film 2, and then the optical device 5 irradiates the photoconductor film 2 with light. An electrostatic latent image is formed on the film 2. Thereafter, the developing device 6 supplies the toner onto the photoconductor film 2 to visualize the electrostatic latent image. The toner image on the photoconductor drum 3 is transferred to the transfer device 8
Is transferred onto the recording paper 7. After the transfer, the toner remaining on the photosensitive drum 3 is removed by the cleaning device 9. Next, the static elimination lamp 10 irradiates the photoconductor film 2 with light to remove the electric charge remaining on the photoconductor film 2 and equalize the surface potential of the photoconductor film 2 to a predetermined potential. After that, the main charger 4 charges the photosensitive drum 3 again. These series of processes are continuously and repeatedly performed according to the rotation of the photosensitive drum 3.

In the prior art, an inorganic material or an organic material is used as a photosensitive material forming the photosensitive film 2. Se-based materials, amorphous Si-based materials, etc. are used as the inorganic materials. In recent years, organic materials are often used in terms of safety and workability. Organic photoreceptors using organic materials are classified into laminated organic photoreceptors and single-layer organic photoreceptors.

The laminated organic photoreceptor has a structure in which a charge generation layer and a charge transport layer are laminated. Among the materials forming the charge transport layer, many materials having a good hole transporting ability have been developed, but a material having an excellent electron transporting ability has not yet been developed. For this reason, most of the laminated organic photoconductors are of the negative charging type. However, in the case of charging a negative charging type photoconductor using a charger that uses corona discharge, there is a problem that ozone is often generated and a new ozone countermeasure is required in terms of safety and environmental friendliness. there were. In order to overcome the above problems, a single-layer organic photoreceptor in which a charge generation medium is dispersed in a charge transport medium has been proposed. In the single-layer organic photoconductor, a positive charge type photoconductor can be easily realized by using a material having a good hole transport ability as the charge transport medium.

[0007]

A single-layer organic photoreceptor is preferable in terms of ease of production as compared with a laminated organic photoreceptor. However, the single-layer photoconductor film generally has a high residual potential even after charge elimination. Further, there is a problem in that the charge potential at the time of charging becomes low due to the photocarrier remaining in the photosensitive layer exhibiting the high residual potential.
In addition, the photoconductor film having a good charging ability during the short use time has a problem that the longer the use time is, the more fatigued the film is, the more trap sites are increased, and the lower the chargeability is.

The above-mentioned conventional technique has the following problems. That is, there is a problem that after a predetermined amount of electric charge is applied to the unit area of the photoconductor film 2 by the main charger 4, dark decay occurs in which a part of the electric charge is lost with the passage of time. Therefore, as the photosensitive drum 3 rotates, an arbitrary region of interest on the photosensitive film 2 moves from the charging position (position close to the main charger 4) to the developing position (position close to the developing device 6). In the meantime, the amount of charge in that area will decrease.

It is generally called dark decay that the surface potential of the photosensitive film 2 decreases without exposure. The degree of this dark decay changes depending on various factors such as the charge holding ability of the photoconductor film and the environment in which the image forming apparatus 1 is installed. When the charge holding ability of the photoreceptor film 2 and the environment in which the image forming apparatus 1 is installed are different for each image forming apparatus 1, the degree of dark decay also varies for each image forming apparatus 1. Further, when the charge holding ability of the photosensitive film 2 or the environment in which the image forming apparatus 1 is installed changes with time, the degree of dark decay also changes with time. A change in the degree of dark decay causes a change in the charge amount of the photoconductor film 2 at the developing position, which hinders the formation of an image with a uniform density.

In the conventional image forming apparatus 1, irrespective of the installation environment and without considering the temporal change of dark attenuation,
The same data for compensating for the decrease in surface potential due to dark decay was set for all the image forming apparatuses 1. This data is initial data corresponding to the degree of dark attenuation measured at the time of manufacturing the photosensitive drum 3, for example.

Therefore, when the degree of dark decay changes due to various factors such as the charge holding ability of the photoconductor film and the environment in which the image forming apparatus 1 is installed, the conventional image forming apparatus 1 uses the initial data. However, it is not possible to compensate for the changed dark attenuation, and it becomes impossible to form an image of uniform density. The same applies to the case where the dark decay causes a change over time due to long-term use of the image forming apparatus 1. In this case, the image forming apparatus 1 cannot compensate the fluctuated dark attenuation with the initial data,
It becomes impossible to form an image having a uniform density.

In particular, the positive charging type single-layer organic photoreceptor film has good charging ability and charge retaining ability at the initial stage of use, but the chargeability and charge retaining ability decrease with the lapse of use time. There is a problem of doing. Therefore, there is a problem that the image forming apparatus cannot form a uniform image due to the degree of dark decay in the positive charging type organic photosensitive film changing with time. This is one of the problems to be solved particularly for practical application of the single-layer organic photoreceptor film of the type.

The present invention has been made in order to solve the above problems, and an object of the present invention is to solve the above problems regardless of the cause of the dark attenuation in the photoconductor film even if the dark attenuation is caused by various causes.
An object is to provide an image forming apparatus capable of forming an image having a uniform density.

[0014]

SUMMARY OF THE INVENTION An image forming apparatus according to the present invention comprises a rotatable substrate having a conductive base and a photosensitive film formed on the surface of the base, and the photosensitive member. A charging means for charging the photosensitive film, an exposing means for irradiating the charged photosensitive film with light corresponding to an image, and the exposing means along the rotation direction of the photosensitive member. Based on the degree of dark decay detected by the dark decay detecting means, the dark decay detecting means for detecting the degree of dark decay in the photoconductor film, and the developing means arranged downstream of the means. Then, by adjusting the temperature of the photoconductor film, the first compensating means for compensating the dark decay, and the charging means of the charging means based on the degree of the dark decay detected by the dark decay detecting means. By adjusting the amount of charge supplied to the photoreceptor film,
And a second compensating means for compensating for the dark decay, whereby the above object is achieved.

In the present invention, the first compensating means is
In some cases, the second compensating unit operates in priority to the second compensating unit, and the second compensating unit compensates the dark attenuation that cannot be compensated by the first compensating unit.

In the present invention, the first compensating means is
Heating means for giving a heat quantity to the photoconductor film, and control means for controlling the heat quantity given to the photoconductor film by the heating means on the basis of the degree of the dark decay detected by the dark decay detecting means. May have.

In the present invention, the first compensating means is
There may be a case where a temperature sensor for detecting the temperature of the photoconductor film is further provided, and the amount of heat given to the photoconductor film by the heating means may be controlled based on the temperature detected by the temperature sensor.

In the present invention, the second compensating means is
It may be a means for adjusting the power supply current of the charging means.

In the present invention, the charging means may be a scorotron type, and the second compensating means may be means for adjusting the potential control means of the charging means.

[0020]

In the image forming apparatus of the present invention, the photoconductor member is provided with a conductive base and a photoconductor film formed on the surface of the base. The photoconductor film is charged by the charging means. The charged photoconductor film is exposed by the exposure means to form an electrostatic latent image. The electrostatic latent image on the photoconductor film is developed by developing means. In the photoconductor film of the photoconductor member, dark decay occurs in which the surface potential due to charging by the charging means decreases with time even when no exposure is performed.

The dark decay detecting means detects the degree of dark decay in the photoconductor film. The first compensating means adjusts the temperature of the photoconductor film in accordance with the degree of the dark decay of the photoconductor film detected by the dark decay detecting means to thereby reduce the surface potential of the photoconductor film due to the dark decay. Compensate for fluctuations. The second compensating means also adjusts the amount of charge supplied to the photoconductor film by the charging means in accordance with the degree of the dark decay of the photoconductor film detected by the dark decay detecting means. The fluctuation of the surface potential due to the dark decay is compensated.

As a result, when the degree of dark decay changes with time, or when the dark decay varies among image forming apparatuses due to the installation environment of the image forming apparatus, etc.
If the dark decay fluctuates from the level just after the photoconductor film was manufactured,
An image having a uniform image density can be formed by compensating for a change in the surface potential due to a change over time in the degree of dark decay or the variation.

Further, since the compensation by the first compensating means is harmless because there is no increase in discharge products, the first compensating means is
If it is operated with priority over the second compensation means,
It is possible to minimize the generation of harmful substances accompanying the compensation operation.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The image forming apparatus of the present invention, after detecting the surface potential, influences the image formation within a certain range based on the detected surface potential, for example, when the decrease amount of the surface potential is up to about 40V. The temperature of the photosensitive drum, which is one of the parameters, is adjusted. If the amount of change in surface potential exceeds the range, the power supply current of the main charger is adjusted according to the amount of change. As a result, the change with time of the charge amount of the photosensitive film at the developing position is compensated, and an image having a uniform density is formed. Therefore, the present invention is effective in compensating for the dark attenuation for the photosensitive drum in which the change amount of the dark attenuation, that is, the decrease amount of the surface potential is about 40V or more.

An example of the present invention will be described below in the case of using a positive charging type single-layer organic photoreceptor film as an example.

FIG. 1 shows an image forming apparatus 1 according to an embodiment of the present invention.
It is a systematic diagram which shows the structure of 1. This image forming apparatus 11
1. As shown in FIG. 1, a rotatable photoconductor drum 13 in which a photoconductor film 12 made of a single-layer type organic photoconductor is formed on the surface of a drum substrate 30 made of a metal material such as aluminum, and a photoconductor film. A main charger 14 that uniformly applies a desired amount of electric charge to 12 and an optical device 15 that exposes the photoconductor film 12 to generate light for forming an electrostatic latent image on the photoconductor film 12 and a photoconductor film. A developing device 16 for developing the electrostatic latent image on the recording medium 12 with toner, and a toner image on the photosensitive drum 13 on the recording paper 17
A transfer device 18 for transferring the toner image, a cleaning device 19 for removing the toner remaining on the photosensitive drum 13 after the transfer of the toner image, and an electric charge remaining on the photosensitive drum 13 for removing the photosensitive material. A static elimination lamp 20 for equalizing the potential on the body membrane 12 to a predetermined potential is provided.

As the main charger 14, a scorotron charger is adopted, and a discharge wire 21 for corona discharge, a shield case 22 surrounding the discharge wire 21 and opening to the photosensitive drum 13 side, and a shield case 22 are provided. And a metal grid 23 provided in the opening. A power supply 25 for supplying a current required for corona discharge is connected to the discharge wire 21 of the main charger 14.
The shield case 22 is grounded.

In this embodiment, as the main charger 14,
By using the scorotron charger, the surface potential at the charging position of the photosensitive drum 13 at the time of charging is
It reaches a predetermined upper limit value and is held at the upper limit value. This is for the following reason. The power supply current Icc from the power supply 25 to the discharge wire 21 is the discharge current Isc to the shield case 22, the discharge current Igc to the grid 23, and the discharge current Ipc to the photosensitive drum 13 due to the discharge.
Will be diverted to. In order for the discharge current from the discharge wire 21 to reach the surface of the photoconductor film 12 via the grid 23,
It is necessary that the surface potential of the photosensitive film 12 is lower than the potential of the grid 23.

When the discharge current Ipc is supplied to the photoconductor film 12 at the charging position by the discharge from the discharge wire 21, the surface potential of the photoconductor film 12 gradually rises. When the rising surface potential matches the potential of the grid 23,
After that, no discharge occurs between the grid 23 and the photoconductor film 12. Power supply current Ic supplied to the discharge wire 21
c is the discharge currents Isc and Ipc. Therefore, the surface potential of the photoconductor film 12 is determined by the grid potential of the grid 23, and is held at the grid potential after reaching the grid potential.

A surface potential meter 26 for measuring the surface potential is arranged near the developing position of the photosensitive drum 13 without hindering the rotation of the photosensitive drum 13. The surface electrometer 26 is connected to the comparator 27 and detects a difference between a preset optimum surface potential reference value and the surface potential measured by the surface electrometer 26. Comparator 27
Is connected to a control device 28 including, for example, a microcomputer. The control device 28 is
The heater 24 and the power supply 25 are controlled. A memory 29 is connected to the control device 28. The detection of the degree of dark decay is performed by the surface electrometer 26 and the comparator 27.

The photoconductor film 12 is formed on the inner surface of the drum substrate 30.
A heater 24 made of a planar heating element for increasing the temperature and a temperature sensor 31 for measuring the temperature of the photoconductor film 12 are provided.

As the main charger 14, a scorotron charger is used in this embodiment. Generally, the photoreceptor film 1
2 has a saturated charging potential Vs of 500 to 1000 V, especially 7
It is desirable to carry out main charging so as to be in the range of 00 to 850V. Therefore, when performing corona discharge, 4
It is desirable to apply a high voltage of ˜7 kV to the discharge wire 21 of the main charger 14.

FIG. 2 is a system diagram showing the arrangement of the photoconductor drum 13, the main charger 14, the developing device 16 and the charge eliminating lamp 20 of this embodiment, and FIG. 3 is a grid 23 of the main charger 14. It is a top view. Charger width W1 of the main charger 14
Is, for example, 22 mm, and the opening width W of the grid 23 is
2 is 16 mm as an example. The distance L1 between the grid 23 and the photoconductor drum 13 is 1.5 mm as an example. An angle θ1 between the downstream end of the main charger 14 with respect to the rotation direction of the photoconductor drum 13 and the developing device 16 along the rotation direction is 120 ° as an example.
An angle θ2 along the rotation direction between the main charger 14 and the upstream end of the main charger 14 in the rotation direction is 30 °, for example. The diameter of the photoconductor drum 13 is, for example, φ78 mm. The grid length L2 of the grid 23 is 320 as an example.
mm. The openings of the grid 23 are formed in a mesh shape, and the opening ratio is 80% as an example.

The optical device 15 used for image exposure is
An optical system including a lens or a reflecting mirror, or a laser light oscillator is used. The developing device 16 includes a developing roller 16 a that supplies the charged toner of the one-component developer or the two-component developer to the surface of the photoconductor film 12. As the transfer device 18, a corona charger similar to the main charger 14 or a contact type charger is used.

In the present embodiment, the charge removal light quantity of the charge removal lamp 20 is such that the charge potential of the photoconductor film 12 falls to near zero potential of 100 V or less. In addition, it is preferable that it is 5 LUX · SEC or more, and particularly 10 LUX · SEC or more. On the other hand, when it is 50 LUX · SEC or more, deterioration of quality occurs due to light fatigue of the photoconductor film 12.
As the static elimination lamp 20, any visible light source such as a halogen lamp, a fluorescent lamp, a cold cathode ray tube, or a neon lamp such as red or green can be used. Alternatively, a monochromatic light source such as an LED (light emitting diode) of red, yellow, green or the like can be used.

The photoconductor film 12 of this embodiment is a positive charging type single layer organic photoconductor film, and is formed by mutually dispersing a binder resin, a charge transport medium and a charge generating substance. As the charge generating substance, any organic photoconductive pigment known per se is used. In particular, phthalocyanine pigments, perylene pigments,
Photoconductive organic pigments such as quinacridone pigments, pyranthrone pigments, disazo pigments and trisazo pigments are used alone or in combination of two or more.

As the charge transport medium, a medium in which a charge transport substance is dispersed in a resin medium is used. As the charge transport material, any hole transport material or electron transport material known per se is used for the purpose of the present invention. Examples of suitable hole transport materials are poly-N-vinylcarbazole, phenanthrene, N-ethylcarbazole, 2,5-diphenyl-1,3,4-oxadiazole, 2,5-bis (4
-Diethylaminophenyl) -1,3,4-oxadiazole, bis-diethylaminophenyl-1,3,6-
Oxadiazole, 4,4'-bis (diethylamino)
-2,2'-dimethyltriphenylmethane, 2,4,5
-Triaminophenylimidazole, 2,5-bis (4
-Diethylaminophenyl) -1,3,4-triazole, 1-phenyl-3- (4-diethylaminostyryl) -5- (4-diethylaminophenyl) -2-pyrazoline, p-diethylaminobenzaldehyde- (diphenylhydrazone), etc. , Or a combination of a plurality of these. 2 examples of suitable electron transport materials
-Nitro-9-fluorenone, 2,7-dinitro-9-
Fluorenone, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2-nitrobenzothiophene, 2,4,8-trinitrothioxanthone, dinitroanthracene, dinitroacridine, It is used in any one of dinitroanthoquinone and the like, or a combination of a plurality thereof.

As the binder resin, various ones, for example, styrene-based polymers, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-
Maleic acid copolymer, acrylic polymer, styrene-acrylic copolymer, styrene-vinyl acetate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy Examples of various polymers include resins, polycarbonates, polyarylates, polysulfones, diallylphthalate resins, silicone resins, ketone resins, polyvinyl butyral resins, polyether resins, phenol resins, and photocurable resins such as epoxy acrylates and urethane acrylates. To be done. A photoconductive polymer such as poly-N-vinylcarbazole can also be used as the binder resin.

The charge generating substance present in the photoreceptor film 12 is suitably in the range of 0.1 to 50 parts by weight, particularly 0.5 to 30 parts by weight, per 100 parts by weight of the binder resin. It is suitable that the charge transport substance is in the range of 20 to 500 parts by weight, particularly 30 to 200 parts by weight, per 100 parts by weight of the binder resin. The thickness of the photoreceptor film 12 is preferably in the range of 10 to 40 μm, particularly 22 to 32 μm in view of high surface potential, printing durability and sensitivity.

As the conductive drum base 30 of the photosensitive drum 12, an aluminum base pipe, an aluminum base pipe subjected to alumite treatment, or a base made of a conductive resin is generally used. The organic photosensitive layer as the photosensitive film 12 is formed by using a resin, an amide solvent such as N, N-dimethylformamide, N, N-dimethylacetamide; a cyclic ether such as tetrahydrofuran or dioxane; dimethyl sulfoxide; benzene; Aromatic solvents such as toluene and xylene; ketones such as methyl ethyl ketone; N-methyl-2-pyrrolidone; phenols such as phenol and cresol, and the like; And This composition is applied to the conductive drum substrate 30 to form the photoconductor film 12.

The present invention has a remarkable advantage in the case of a positive charging type organic single layer photoreceptor, and the positive charging type also has an advantage that ozone is less generated at the time of main charging. In the case of the positive charging type, it is preferable to use a perylene pigment, an azo pigment or a combination thereof as the charge generating substance, and to use 2,6-dimethyl-2 ′, 6′-di te as the charge transporting substance.
Diphenoquinone derivative such as rt-butyldiphenoquinone, 3,3′-dimethyl-N, N, N ′, N′-tetrakis-4-methylphenyl (1,1′-biphenyl)-
It is preferable to use diamine compounds such as 4,4′-diamine, fluorene compounds and hydrazone compounds.

Below, referring to the flow chart,
The operation of this embodiment will be described.

FIG. 4 is a flow chart showing the operation of the image forming apparatus 11 of this embodiment, and FIG. 6 is the operation of detecting the surface potential of the photoconductor film 12 and the photoconductor film 12 in this embodiment.
6 is a flowchart for explaining in detail the temperature correction operation of FIG. The operation described below is performed by the image forming apparatus 1 of this embodiment.
In the case of the electrostatic copying machine 1 as an example, this is performed during the warm-up period after the main switch is turned on, or during the period when the copying operation is not performed. When it is performed during the warm-up period, it is not necessary to independently set an operation period for the correction operation of the present embodiment described below, and it is possible to prevent waste of time for the copying operation.

At step a1 in FIG. 4, the main switch is turned on. In step a2, the surface potential is measured, as will be described later in detail. Step a
At 3, it is determined whether the measured surface potential is equal to a predetermined reference value of the surface potential. If the determination in step a3 is negative, in step a4, a correction operation described later in detail is executed.

After the completion of the correction operation, in step a5, the electrostatic copying machine is set to a standby state in which copying operation is possible, and in step a6, the copying operation is executed. At step a7, the copying operation is completed and the main switch is turned off. If the determination is affirmative in step a3, in step a5, the electrostatic copying machine is set to a standby state in which copying operation is possible. Thereafter, the processing of steps a6 and a7 is performed.

At step b1 in FIG. 5, the main switch is turned on. At step b2, the photosensitive drum 13 starts rotating, and the main charger 14 is powered by the power supply 25.
Discharge current Icc is supplied from. The optical device 15, the developing device 16, the transfer device 18, the cleaning device 19, the discharge lamp 20 and the like are all stopped. In step b3, the process stands by until the photosensitive drum 13 makes one rotation (for example, about 1 to 6 seconds). The waiting time may be a time in which the photosensitive drum 13 rotates at least once. When the main motor of the image forming apparatus 11 of this embodiment is pulse-driven, the measurement of the waiting period may be realized by counting the pulses used for driving the main motor. Further, the image forming apparatus 11 may separately use a timer or a counter for measuring the waiting period.

The waiting period is set in order to wait until the charging on the entire surface of the photosensitive film 12 is completed.
As described above, the main charger 1 composed of the scorotron
This is because when the photosensitive drum 13 is charged by means of No. 4, the entire surface of the photosensitive film 12 may not be charged to the saturated charging potential Vs.

When the determination in step b3 becomes affirmative, the surface potential is measured by the surface electrometer 26 in step b4. In step b5, it is judged whether or not the measured surface potential is equal to a predetermined reference value of the surface potential.

If the determination in step b5 is negative, it is determined in step b6 whether or not the temperature of the photosensitive film 12 is the lower limit value of the settable temperature range.

If the determination in step b6 is negative, in step b7, the correcting operation relating to the temperature of the photosensitive film 12 described below is executed.

FIG. 6 shows the relationship between the temperature of the photosensitive film 12 and the variation range of the surface potential at the developing position. As can be seen from the figure, if the temperature of the photosensitive film 12 rises by 1 ° C.,
The surface potential drops by about 2V. The present invention utilizes this characteristic to compensate for changes in the degree of dark decay. When the surface potential measured by the surface potential meter 26 decreases due to dark decay, the comparator 27 determines the amount of decrease in the surface potential. The controller 28 lowers the temperature of the photoconductor film 12 according to the amount of decrease in the surface potential, and maintains the surface potential at the reference value. On the contrary, when the environment in which the image forming apparatus 11 is installed changes and the surface potential increases, the temperature of the photoconductor film 12 is increased in accordance with the amount of increase in the surface potential to increase the surface potential. Maintain the standard value. Therefore, when the dark decay changes with time, or when the dark decay varies depending on the installation environment of the image forming apparatus and the like, the dark decay may occur immediately after the photoconductor film is manufactured. Even when the temperature changes from the degree, the temperature of the photoconductor film 12 is controlled according to the amount of the change, so that it is possible to compensate for the temporal change or the variation of the degree of dark decay. This allows
A uniform image density can be realized.

The correction operation will be described more specifically with reference to FIG. In this case, the reference value of the surface potential is set to 800V, for example. In this case, when the surface potential measured by the surface electrometer 26 is 780 V, for example,
The temperature of the heater 24 is adjusted by the controller 28 so that it is lower than the temperature set at that time by 10.degree. The measured surface potential is, for example, 820V.
At the time of, the temperature of the heater 24 is adjusted by 10 ° C. higher than the temperature set at that time.

The temperature of the heater 24 is adjusted by the controller 28 adjusting the control voltage of the heater 24. FIG. 8 shows the relationship between the heater control voltage and the heater temperature. As can be seen from the figure, when raising the temperature of the heater 24, the heater control voltage is raised, and conversely, when lowering the temperature of the heater 24, the heater control voltage is lowered. However, the controllable temperature range of the heater 24 is 30.
℃ ~ 60 ℃, therefore the adjustment range of the surface potential is almost 6
It is 0V.

The initial temperature of the heater 26 is usually set near the upper limit of the temperature range, for example, 50 ° C. this is,
This is because in most cases the surface potential drops and rarely rises.

It should be noted that when a selenium-terrell-based material is used as the photoconductor material forming the photoconductor film 12, thermal destruction occurs when the temperature of the photoconductor film 12 exceeds 45 degrees. Therefore, it is necessary to adjust the temperature of the photoconductor film 12.

Data related to the correction operation shown in FIG. 6 and various data necessary for adjusting the temperature of the photoconductor film 12, such as the data shown in FIGS. 7 and 8, are stored in the memory 29.

Furthermore, the image forming apparatus 11 of this embodiment is
Photoreceptor film 12 of the relationship itself shown in FIGS. 6, 7 and 8.
It is also possible to configure so as to compensate for the deterioration caused by the above, the variation due to the installation environment of the image forming apparatus, and the like. Memory 2 above
The data stored in 9 fluctuates due to long-term use of the photoconductor film 12 or changes in ambient atmosphere such as temperature, humidity, and vibration. Therefore, in the present invention, the data in the memory 29 is rewritten to the latest data each time the correction operation is performed. That is, various parameters that fluctuate by performing the correction operation, for example, data such as the temperature of the photoconductor film 12 measured by the temperature sensor 31 are fed back and used for the subsequent correction operation. As a result, the correction operation can be performed more precisely according to the characteristic peculiar to each image forming apparatus 11, and sufficient compensation of the surface potential can be realized. When the correction process in step b7 is completed, in step b9, the image forming apparatus 11 enters a standby state in which a copying operation is possible. When the copying operation is executed and completed in step b10, the main switch is cut off and the operation of the image forming apparatus 11 is stopped in step b11. Then, the process returns to step b1.

If the determination in step b6 is negative, that is, if the temperature of the photosensitive film 12 is the lower limit value of the settable temperature range, the temperature of the photosensitive film 12 is maintained at the lower limit value. As it is, in step b8, the correction operation regarding the current Icc of the power supply 25 of the main charger 14 described below is executed.

This correction operation is performed by adjusting the surface potential by the controller 28 adjusting the current Icc of the power supply 25 based on the amount of decrease in the surface potential.
Such correction has been performed conventionally, and the specific means and method are not particularly limited. Alternatively, the discharge current Ipc may be adjusted by adjusting the grid voltage while keeping the current Icc of the power supply 25 unchanged, thereby adjusting the surface potential. Discharge current Icc
The correction such as to adjust the value involves the generation of harmful substances such as ozone and NOx on the photoconductor film 12. In the present invention, after performing a harmless correction operation of adjusting the temperature of the photoconductor film 12,
When the temperature cannot be corrected only by adjusting the temperature, the correction is performed by adjusting the amount of electric charge supplied to the photoconductor film 12 of the main charger 14. Therefore, the correction according to the present invention is more harmless than the case where the correction is performed only by adjusting the amount of charge supplied to the photoconductor film 12 of the main charger 14.

When the correction process of step b8 is completed, the process proceeds to step b9, and the processes of step b9 and after are executed.

Even if the determination is affirmative in step b5, the process proceeds to step b9, and the above-mentioned step b
The processing after 9 is executed.

According to the measurement by the inventor of the present invention, the potential at the developing position of the image forming apparatus of the prior art which does not adjust the surface potential of the photosensitive film 12 as in the present embodiment and the potential of the present embodiment. When the electric potential at the developing position of the image forming apparatus 11 is compared with that of the electrostatic copying machine, the results shown in FIG. 9 are obtained. Line 32 in FIG. 9 is for the prior art and line 33 is for this embodiment. As can be seen from FIG. 9, in the prior art, the potential at the developing position gradually decreases with use, whereas the image forming apparatus 11 according to the present embodiment.
Has a substantially constant potential at the developing position.

As a result, it is possible to realize the image forming apparatus 11 in which the image density is maintained constant in the regular developing method and the fog phenomenon, which is uneven image density, is prevented in the reversing developing method.

Although a heater is conventionally installed in the photoconductor drum 13, this prevents the dew condensation on the photoconductor drum 13 by maintaining the temperature of the photoconductor drum 13 at around 35 degrees. This is because In the photoconductor drum 13 of the image forming apparatus 11 as an electrostatic copying machine, due to dew condensation on the surface of the photoconductor drum 13, the charge distributed on the photoconductor drum 13 disappears or the formed electrostatic charge is lost. This is because the latent image may be destroyed. However, such a temperature adjustment is a rough one, and the temperature sensor 31 is not provided for precise temperature adjustment as in the present embodiment.

In the above embodiment, the degree of dark decay is detected by measuring the surface potential of the photosensitive film 12 at the developing position. However, the device and method for detecting the degree of dark decay are not particularly limited, and other devices and methods capable of detecting the degree of dark decay may be used. For example, a detector for taking out a leak current Ilc generated by dark decay in the photoconductor film 12 is connected to the photoconductor drum 13, and the degree of dark decay is determined from the amount of fluctuation of the leak current Ilc detected by the detector. May be detected. Also in this case, in order to sufficiently compensate for the change over time in the degree of dark decay, the variation of the leak current Ilc is stored in the memory each time the correction operation is performed,
Various data used for the correction operation may be set as data based on the latest characteristics of each image forming apparatus.

In the above embodiments, the drum-shaped substrate on which the photosensitive film is formed is used as the photosensitive member.
A belt-shaped substrate on which a photosensitive film is formed may be used. Further, in the above embodiment, the image forming apparatus of the present invention is described as an electrostatic copying machine, but the image forming apparatus of the present invention is
Regardless of the electrostatic copying machine, any image forming apparatus that forms an image by an electrophotographic method may be used.

[0067]

According to the present invention, fluctuations in the surface potential are compensated by detecting the surface potential on the photosensitive drum and then adjusting the temperature of the photosensitive film based on the detection result. Further, when the surface potential fluctuation cannot be sufficiently compensated by adjusting the temperature of the photoconductor film, the fluctuation of the surface potential is compensated by adjusting the amount of charges supplied to the photoconductor film of the main charger. As a result, when the dark decay changes with time, or when the dark decay varies depending on the installation environment of the image forming apparatus and the like, the dark decay is the degree immediately after the photoconductor film is manufactured. , It is possible to form an image having a uniform image density more harmlessly by compensating for the fluctuation of the surface potential due to the temporal change or the variation of the degree of dark attenuation.

[Brief description of drawings]

FIG. 1 is a system diagram of an image forming apparatus 11 according to a first embodiment of the present invention.

FIG. 2 is a system diagram showing an arrangement state of the present embodiment.

FIG. 3 is a plan view of a grid 23 of the main charger 14.

FIG. 4 is a flowchart illustrating the operation of this embodiment.

FIG. 5 is a flowchart illustrating the operation of this embodiment.

FIG. 6 is a graph showing the relationship between the temperature of the photosensitive film 12 and the change width of the surface potential.

FIG. 7 is a graph showing the relationship between the measured surface potential and the temperature adjustment range.

FIG. 8 is a graph showing a relationship between a heater control voltage and a heater temperature.

FIG. 9 is a graph illustrating the effect of this embodiment.

FIG. 10 is a system diagram of a conventional image forming apparatus 1.

[Explanation of symbols]

 Reference Signs List 11 image forming apparatus 12 photoconductor film 13 photoconductor drum 14 main charger 16 developing device 19 cleaning device 20 discharge lamp 21 discharge wire 22 shield case 23 grid 24 heater 25 power supply 26 surface potential meter 27 comparator 28 controller 29 memory 30 Drum base 31 Temperature sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G03G 15/02 102 (72) Inventor Ichiro Yamazato 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mitako (72) Inventor, Takuji Terada, 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (6)

[Claims] 1. A rotatable photoconductor member comprising a conductive substrate and a photoconductor film formed on the surface of the substrate, and a photoconductor film which is disposed in the vicinity of the photoconductor member. Charging means for charging, exposing means for irradiating the charged photoconductor film with light corresponding to an image, and developing means arranged downstream of the exposing means along the rotation direction of the photoconductor member. A dark decay detecting means for detecting the degree of dark decay in the photoconductor film, and adjusting the temperature of the photoconductor film based on the degree of dark decay detected by the dark decay detecting means. The first compensating means for compensating for the dark decay, and adjusting the amount of charge supplied to the photoconductor film of the charging means based on the degree of the dark decay detected by the dark decay detecting means. An image forming apparatus comprising: a second compensating unit that compensates for the dark decay. 2. The first compensating means operates in preference to the second compensating means, and the second compensating means compensates for dark attenuation that could not be compensated by the first compensating means. The image forming apparatus according to Item 1. 3. The heating means for applying heat to the photoconductor film and the degree of dark decay detected by the dark decay detection means, the first compensating means The image forming apparatus according to claim 1, further comprising a control unit that controls the amount of heat applied to the photoconductor film. 4. The first compensation means further comprises a temperature sensor for detecting the temperature of the photoconductor film, and the photoconductor film is provided by the heating means on the basis of the temperature detected by the temperature sensor. The image forming apparatus according to claim 3, which controls the amount of heat applied to the image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the second compensating unit is a unit that adjusts a power supply current of the charging unit. 6. The image forming apparatus according to claim 1, wherein the charging unit is a scorotron type, and the second compensating unit is a unit for adjusting a potential control unit of the charging unit.