JPH0743962A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device forming an image with uniform density even when the degree of dark attenuation on a photoreceptor film is fluctuated by the various kinds of causes. CONSTITUTION:A surface potential sensor 26 detecting the surface potential of the photoreceptor film 12 at a developing position is provided near a photoreceptor drum 13. A comparator 27 is connected to the sensor 26 and the fluctuating amount of the value of the surface potential with respect to an initial value is detected by the comparator 27. Besides, the comparator 27 is connected to a controller 28. In a memory 29 connected to the controller 28, the fluctuating amount of the value of the surface potential and data showing relation between a destaticizing time and an electrostatic charge time, the electrostatic charge time and a developing time are stored. By the controller 28, any of a destaticization means, an electrostatic charge means and a developing means is moved based on the data read out of the memory 29 so as to adjust the destaticizing time and the electrostatic charge time or the electrostatic charge time and the developing time.

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. 9 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 its surface, a main charger 4 for uniformly applying a predetermined amount of electric charge to the photosensitive film 2, and a photosensitive film 2. An optical device 5 for exposing and forming an electrostatic latent image on the photosensitive film 2, a developing device 6 for developing the electrostatic latent image on the photosensitive film 2, and a developing device 6 formed on the photosensitive film 2. A transfer / separation charger 8 that transfers the toner image to the paper 7 and separates the paper 7 from the photoconductor drum 3, and a cleaning blade that removes the toner remaining on the photoconductor drum 3 after the toner image is transferred to the paper 7. The cleaning device 9 includes a cleaning device 9 and a charge eliminating lamp 10 for removing charges remaining on the photosensitive drum 3 and setting the surface potential of the photosensitive drum 3 to a predetermined uniform potential.

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 photosensitive film 2 to develop the electrostatic latent image. The toner image on the photosensitive drum 3 is transferred onto the sheet 7 by the transfer / separation charger 8. The toner remaining on the photosensitive drum 3 after the transfer is cleaned by the cleaning device 9
Removed by. Next, the static elimination lamp 10 irradiates the photoconductor film 2 with light to remove the electric charges remaining on the photoconductor film 2. 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. As such inorganic materials, organic materials are often used in recent years 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, when a negative charging type photoconductor is charged by using a charger that uses corona discharge, ozone is often generated, and there is a problem that ozone countermeasures are newly required in terms of safety and environment. 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 that the photocarrier remaining in the photoconductor film showing the high residual potential lowers the potential on the photoconductor film during charging. Further, the photosensitive member film having good charging ability during a short period of use also suffers from fatigue as the operating time becomes longer, trap sites increase, and the charging capability decreases.

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 near the main charger 4) to the developing position (position near 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 photoconductor film 2 decreases regardless of 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. Also,
When the charge holding ability of the photosensitive film 2 and the environment in which the image forming apparatus 1 is installed vary with time, the degree of dark decay also varies 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, making it difficult to form an image with a uniform density.

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

Therefore, when the degree of dark decay varies 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 does not have the dark decay. Compensation cannot be performed, and a predetermined surface potential cannot be obtained at the developing position. The same applies to the case where the degree of dark attenuation changes as the image forming apparatus 1 is used for a long period of time. In this case, the image forming apparatus 1 cannot compensate for the fluctuating dark attenuation, and thus cannot form an image with uniform density.

[0012] In particular, the positive-charge type single-layer organic photoconductor film has a good chargeability and charge-retaining ability at the beginning of use, but the chargeability and charge-retaining ability decrease as it is used. I have a problem. Therefore, the problem that the image forming apparatus cannot form an image with a uniform density due to the degree of dark decay in the positively chargeable organic photosensitive film changing with use is a problem. This is one of the problems to be urgently solved particularly when the charge-type single-layer organic photoreceptor film is put into practical use.

The present invention has been made in view of the above circumstances, and even if the degree of dark attenuation in the photoconductor film changes due to various causes, an image can be formed with a uniform density regardless of the cause of the change. It is an object of the present invention to provide an image forming apparatus that can be formed.

[0014]

An image forming apparatus of the present invention includes a rotatable photoconductor drum having a photoconductor film formed on the surface thereof, and a photoconductor drum disposed in the vicinity of the surface of the photoconductor drum. A charging means for supplying electric charges onto the photoconductor film, a developing means arranged downstream of the charging means along the rotation direction of the photoconductor drum, and a rotation direction of the photoconductor drum. Along the upstream side of the charging means, the charge removing means for removing the charges on the photoconductor film, and the dark decay in the photoconductor film based on the dark decay of the photoconductor film. A dark decay detecting means for detecting the degree of dark decay, and an interval between the charge eliminating means and the charging means, or the charging means and the darkening decay means according to the variation of the degree of dark decay detected by the dark decay detecting means. And a control means for adjusting the distance to the developing means. The above-mentioned object can be achieved by.

In the image forming apparatus, the dark decay detecting means has a sensor for detecting the potential of the surface of the photosensitive drum near the developing means, and the sensor is provided near the developing means. It may be.

In the image forming apparatus, the discharging unit and the developing unit may be fixed, and the charging unit may be movable.

In the image forming apparatus, the charge eliminating means may be a charge eliminating lamp.

The image forming apparatus supports a pair of rails provided near the charging means along the outer periphery of the photosensitive drum and the charging means, and moves the charging means on the rails. And a motor for driving the mechanism, and the control means may control the motor.

[0019]

In the image forming apparatus of the present invention, first, the photoconductor film formed on the surface of the photoconductor drum is uniformly charged by the charging means. Then, the photoconductor film is irradiated with light according to the image, and the potential of the part irradiated with the light is lowered. The developing means attaches a developer to the photoconductor film according to such a potential distribution on the photoconductor film to form an image on the photoconductor film.

The surface potential of the portion of the photoconductor film which is not irradiated with light is lowered by dark decay. The dark decay detecting means is composed of, for example, a sensor that detects the surface potential at the developing position and a comparator that compares the detected potential with a reference potential, and detects the dark decay of the photoconductor film. Detect the degree. Based on the detected degree of dark decay, the control unit moves any one of the charge eliminating unit, the charging unit, and the developing unit according to the change in the degree of dark decay. As a result, the distance between the charge eliminating means and the charging means or the distance between the charging means and the developing means is adjusted to compensate for the fluctuation of the degree of dark decay.

In the present invention, as described above, when the variation in the degree of dark decay of the photoconductor film is detected, the variation in the degree of dark decay of the photoconductor film in the vicinity of the developing means is detected based on the detection result. I am trying to compensate. This allows
For example, when the characteristics of the photoconductor film are changed from the characteristics immediately after manufacturing and the degree of dark attenuation is changed with repeated use, or when the degree of dark attenuation is changed due to changes in the installation environment of the image forming apparatus. However, fluctuations in the degree of dark decay are compensated, and the surface potential of the photosensitive drum near the developing means is always maintained at a predetermined potential. In addition, even if the degree of dark attenuation varies from image forming device to image forming device due to differences in the environment in which individual image forming devices are installed, or manufacturing factors, etc.
The surface potential of the photosensitive drum in the vicinity of the developing unit can be set to a predetermined potential by compensating for the variation in the degree of dark decay.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an image forming apparatus 11 according to an embodiment of the present invention.
It is a system diagram which shows the structure of. The image forming apparatus 11 is
A rotatable photoconductor drum 13 having a photoconductor film 12 made of a single-layer organic photoconductor formed on a surface of a drum base 30 made of a metal material such as aluminum, and a main charger for uniformly charging the photoconductor film 12. 14, a developing device 16 for developing the electrostatic latent image formed on the photosensitive film 12 by exposure with toner. On the downstream side of the developing device 16, similarly to the conventional image forming apparatus 1 shown in FIG. 9, transfer / separation charging for transferring the toner image on the photoconductor film 12 to a sheet and separating the sheet from the photoconductor drum 13. And a cleaning device for removing the toner remaining on the photoconductor drum 13, and the photoconductor drum 1 is provided on the downstream side of the cleaning device.
A charge eliminating lamp 20 for removing the electric charge remaining on the upper portion 3 is provided. The main charger 14, the developing device 16, and the discharging lamp 20 respectively constitute a charging unit, a developing unit, and a discharging unit.

A surface potential sensor 26 for detecting the surface potential at the developing position is provided near the developing device 16. The surface potential sensor 26 is connected to the comparator 27 and has a reference value of the surface potential read from the memory 29,
The difference from the detected surface potential value is detected. The surface decay sensor 26 and the comparator 27 are included in the dark decay detecting means.

As the main charger 14, a corona charger such as a scoroton charger, or a charging brush,
A contact type charger such as a charging roller is used. Generally, the saturation charging potential Vs of the photoconductor film 12 is 500 to 1000V,
In particular, it is desirable to perform the main charging so that the voltage is in the range of 700 to 850V. To do so, if the main charging is performed using a corona charger, the charger should be 4 to 7k.
It is desirable to apply a high voltage of V. In the case of contact charging, it is desirable to apply a voltage of about 1.5 to 3 times the surface potential of the photoconductor film 12 at the start of charging to the main charger.

As the optical device used for image exposure, an optical system including a lens, a reflecting mirror, or the like, or a laser light oscillator or the like is used. The developing device 16 includes a developing roller or the like that attaches the charged toner to the surface of the photoconductor film 12. As the transfer / separation charger 18, a corona charger similar to the main charger 14 or a contact type charger is used.

The static elimination lamp 20 irradiates light so that the surface potential of the photosensitive film 12 drops to 100 V or less, preferably about 40 V. In the present embodiment, it is desirable that the charge removal light amount of the charge removal lamp 20 is 5 LUX · SEC or more, particularly 10 LUX · SEC or more on the photoconductor film 12. When the amount of static elimination light 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 resin medium in which a charge transport substance is dispersed 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 resins such as 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 0.1 to 50 parts by weight per 100 parts by weight of the binder resin,
Particularly, it is suitable that the amount is in the range of 0.5 to 30 parts by weight,
On the other hand, the charge transport material is 20 to 100 parts by weight of the binder resin.
It is suitable to be in the range of 500 parts by weight, especially 30 to 200 parts by weight. The thickness of the photoconductor film 12 is 10-4.
It is preferably 0 μm, particularly 22 to 32 μm in view of high surface potential, printing durability and sensitivity.

As the drum substrate 30 of the photosensitive drum 13, a conductive one is used. Generally, an aluminum base pipe or an aluminum base pipe obtained by subjecting the aluminum base pipe to an alumite treatment is used, but a base material made of a conductive resin or a conductive film can also be used. Photoconductor film 1
In order to form the organophotoreceptor layer as 2, the amide-based solvent such as N, N-dimethylformamide and N, N-dimethylacetamide; cyclic ether such as tetrahydrofuran and dioxane; dimethylsulfoxide; benzene;
Aromatic solvents such as toluene and xylene; ketones such as methyl ethyl ketone; N-methyl-2-pyrrolidone; phenols such as phenol and cresol;
A charge generating substance is dispersed in this to obtain a coating composition.
This composition is applied to the conductive drum substrate 30 to form the photoconductor film 12.

The present invention has remarkable advantages in the case of a positively chargeable organic single layer photoreceptor, and the positively chargeable one also has an advantage that less ozone is generated during 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-dibutyldiphenoquinone, 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.

In the vicinity of the main charger 14, the photosensitive drum 1
A rail 31 is arranged along the outer periphery of the photoconductor 3, and the main charger 14 can move along the rail 31 with the rotation axis of the photosensitive drum 13 as an axis. Image forming apparatus 1
1 is shipped, etc., the main charger 14 is arranged at a reference position apart from the static elimination lamp 20 and the developing device 16 by a predetermined distance. Main charger 1 that slides on the rail 31
Both ends of 4 are connected to a pair of rods 35. Also,
The pair of rods 35 are also connected to the gear 32. The gear 32 is driven by a motor 34 via a gear 33 as shown in FIG.
Controlled by 8. Pair of rods 35, gear 3
2, 33 constitutes a mechanism for moving the charging means.

A memory 29 is connected to the control device 28. The memory 29 stores data used for compensating for the difference between the reference value of the surface potential obtained as described later and the surface potential value detected by the surface potential sensor. The controller 28 controls the motor 34 so as to move the main charger 14 by a required distance based on the data read from the memory 29. further,
The movement amount (for example, the rotation amount of the gear 32) when the main charger 14 is moved is also stored in the memory 29. A control means is configured by including the control device 28 and the memory 29.

Photoreceptor drum 13 and main charger 1 of this embodiment
FIG. 5 shows the arrangement of the developing device 16, the developing device 16, and the charge eliminating lamp 20. In this embodiment, the charger width W1 of the main charger 14 is
Is 22 mm, the opening width W2 of the grid 23 is 16 mm, and the grid length L2 is 320 mm. The openings of the grid 23 are formed in a mesh shape, and the opening ratio is 80%. Further, the photoconductor drum 1 in the present embodiment
The diameter of 3 is 78 mm, and the linear velocity of the photosensitive drum 13 is 30.
0 mm / sec, the grid 23 and the photosensitive drum 1
The distance L1 from 3 is set to 1.5 mm.

Further, in this embodiment, the main charger 14
Is at the reference position, that is, the position set at the time of shipment of the image forming apparatus 11, the time (charge-development time) for moving an arbitrary region of interest on the photoconductor film 12 from the charging position to the developing position is 100 msec. And the time required to move from the charge removal position to the charge position (charge removal-charge time) is 100.
msec.

When the image forming apparatus 11 is shipped, the main charger 14 is placed at the reference position, and the charging-developing time and the discharging-charging time at this time are set to predetermined values. The values representing the charging-developing time and the discharging-charging time are stored in the memory 29 when the photoconductor film 12 is manufactured or when the image forming apparatus 11 is shipped.

FIG. 3 shows the surface potential Vd ₁ when the main charger 14 is arranged at the reference position when the charging-developing time is changed, that is, the reference potential and the main charger 14 in this embodiment. Surface potential Vd when is moved to an arbitrary position
Is data showing a change in the difference Vd ₂ -Vd ₁ and _2. Here, as an example, data in the initial stage of use of the photoconductor drum 13 and data in a state where the photoconductor drum 13 has been used 100,000 times are shown. These data are stored in the memory 29 in advance when the photoconductor film 12 is manufactured or when the image forming apparatus 11 is shipped. In addition to the above-mentioned data, the memory 29 also stores data according to the usage state of the photosensitive drum 13. From FIG. 3, when the charging-development time is longer than when the main charger 14 is at the reference position, the surface potential Vd ₂ is lower than the reference potential Vd ₁ , and conversely, when the charging-development time is shorter, the surface potential Vd ₂ is lower. It can be seen that Vd ₂ is higher than the reference potential Vd ₁ . Further, it can be seen that the degree of dark attenuation increases as the use is repeated, and thus the change width of the difference Vd ₂ −Vd ₁ increases. Therefore, even if the degree of dark decay fluctuates due to some cause such as change with time, the fluctuation can be compensated by adjusting the charging-developing time based on the data shown in FIG. For example, when the surface potential at the developing position is lower than the desired potential, the charging-developing time is shortened to increase the surface potential value at the developing position to obtain the desired potential. .

In the image forming apparatus of the present invention, in order to adjust the charging-developing time, either the main charger 14 or the developing device 16 is moved without changing the rotation speed of the photosensitive drum 13. . It is possible to move both the main charger 14 and the developing device 16, but when both are moved, it is desirable to move only one of them because the device becomes large and complicated. Although only the main charger 14 is moved in the present embodiment, the developing device 1
The developing device 16 may be moved by providing the above-mentioned rail, rod or the like in the vicinity of 6.

When the main charger 14 is moved, the main charger 1
4 not only the distance between the developing device 16 and the developing device 16,
The distance between 0 and the main charger 14 also changes.

FIG. 4 is data showing changes in the surface potential difference Vd ₂ -Vd ₁ when the charge removal-charging time is changed. Similar to the data shown in FIG. 3, these data are also stored in the memory 29 in advance when the photoconductor film 12 is manufactured or when the image forming apparatus 11 is shipped. Further, the memory 29 stores data corresponding to the usage state of the photosensitive drum 13, other than the data at the initial use of the photosensitive drum 13 as shown in FIG. 4 and the data after being used about 100,000 times. Remembered From this figure, the main charger 1
It can be seen that the surface potential Vd ₂ at the developing position rises above the reference potential Vd ₁ as 4 moves from the reference position in the direction away from the static elimination lamp 20. It is considered that this is due to the influence of the carriers generated by irradiating the photoconductor film 12 with the static elimination light. When the photoconductor film 12 is irradiated with light by the static elimination lamp 20, carriers are generated in the photoconductor film 12 and the charges remaining on the photoconductor film 12 can be removed. However, when the charge removal-charging time is short, the main charger 14 causes the photoconductor film 12 to
Even if charged, the surface potential of the photoconductor film 12 immediately drops due to the influence of the carriers remaining on the photoconductor film 12. When the charge removal-charging time is long, the residual carriers are small, so the influence of the carriers on the surface potential is small, the decrease of the surface potential is suppressed, and the surface potential at the developing position is lower than the reference potential. To rise. Therefore, even if the degree of dark decay fluctuates for some reason, the fluctuation can be compensated by adjusting the static elimination-charging time. For example, when the surface potential at the developing position becomes lower than the desired potential, the value of the surface potential at the developing position can be increased and a predetermined potential can be obtained by lengthening the static elimination-charging time. .

The charge removal-charging time is adjusted in the same manner as the charge charging / developing time described above, without changing the rotation speed of the photosensitive drum 13, and either one of the charge removing lamp 20 and the main charger 14 is changed. Move to remove static electricity lamp 20 and main charger 14
This is done by adjusting the interval between and. Either the static elimination lamp 20 or the main charger 14 may be moved, but it is preferable to move the main charger 14. This is because the above-mentioned adjustment of the charging-developing time can be performed at the same time as the adjustment of the discharging-charging time.

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

FIG. 6 is a flowchart showing the operation of the image forming apparatus 11 of this embodiment, and FIG. 7 shows the operation of detecting the surface potential at the developing position and the position of the main charger 14 in this embodiment. It is a flow chart explaining adjustment operation. The operation described below is performed by the image forming apparatus 11 of the present embodiment.
As an example, in the case of an electrostatic copying machine, it is performed during the warm-up period after the main power is turned on, or during the period when the copying operation is not performed. When it is performed during the warming-up period, it is not necessary to spend time for the operation of adjusting the position of the main charger 14 which will be described below, and it is possible to prevent waste of time for the copying operation.

Here, the case where the position control operation of the main charger 14 is performed during the warm-up period after the main power is turned on will be described as an example. At step a1 in FIG. 6, the main power supply is turned on. At step a2, the surface potential Vd ₂ at the developing position is measured. In step a3, it is judged whether or not the value of the measured surface potential Vd ₂ is equal to the value of the reference potential Vd ₁ stored in advance. Here, the reference potential Vd ₁ is the surface potential at the developing position when the main charger 14 is arranged at the reference position, as described above. If the determination in step a3 is negative,
The degree of dark decay has changed for some reason, and the position adjusting operation of the main charger 14, which will be described later, is executed in step a4.

After the position adjusting operation of the main charger 14 is completed, the electrostatic copying machine is set to a standby state in which copying operation is possible in step a5, and the copying operation is executed in step a6. In step a7, the copying operation is completed and the main power supply is cut 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. Continuing, step a
The process of 6 is performed.

At step b1 in FIG. 7, the main power source is turned on. In step b2, the photoconductor drum 13 starts rotating, and the main charger 14 and the discharge lamp 20
Turns on. The optical device 15, the developing device 16, the transfer device 18, the cleaning device 19 and the like are all stopped.
Then, in step b3, the surface potential sensor 26 measures the surface potential Vd ₂ of the photosensitive film 12 at the developing position. The measured surface potential Vd ₂ is calculated in step b.
In 4, the comparator 27 determines whether or not it is equal to the reference potential Vd ₁ previously stored in the memory 29.

If the determination in step b4 is negative, it means that the degree of dark decay is fluctuating for some reason. Therefore, in step b5, the position control operation of the main charger 14 described below is executed. . That is, the difference Vd ₂ −Vd ₁ between the measured surface potential Vd ₂ and the reference potential Vd ₁ from the measured surface potential Vd ₂ and the reference potential Vd ₁ is
It is detected by the comparator 27. The controller 28 determines, based on the difference Vd ₂ −Vd ₁ detected by the comparator 27,
Optimal static elimination to compensate for this difference-charging time and charging-
Data showing the developing time, and the main charger 14 at that time
The data indicating the position of is read from the memory 29. Based on the read data, the control device 28 calculates the rotation amounts of the gears 32 and 33, for example, and drives the motor 34 to rotate the gears 32 and 33. The rotation of the gear 32 causes the main charger 14 to move on the rail 31 and stop at a position where a predetermined surface potential can be obtained. Main charger 14
The position after the stop is stored in the memory 29.

The movement of the main charger 14 compensates for variations in the degree of dark decay. In this embodiment, the surface potential Vd ₂ at the developing position can be maintained at a predetermined potential by changing both the charge removal-charging time and the charge-development time. For example, at the beginning of use of the photoconductor drum 13, the main charger 14 is moved from the reference position to the developing device 1.
6 direction to remove static charge-charging time 150 msec
In this case, the charging-developing time becomes 50 msec, and the surface potential at the developing position can be increased by about 20V.
Further, in order to lengthen the static elimination-charging time by 50 msec, the main charger 14 may be moved toward the developing device 16 by about 15 mm. Further, when the main charger 14 is moved so as to set the discharging-charging time to 150 msec while the photosensitive drum 13 is used about 100,000 times, the surface potential at the developing position is increased by about 17V. be able to. As a result, even if the degree of dark decay varies on the photoconductor film 12 due to some reason such as a change over time, an image can be formed with a uniform density.

When the position adjusting operation of the main charger 14 in step b5 is completed, in step b6, the electrostatic copying machine enters a standby state in which the copying operation is possible. In step b7, when the copying operation is executed and completed, step b
At 8, the main power supply is cut off and the operation of the electrostatic copying machine is stopped. Then, the process returns to step b1.

If the determination is affirmative in step b4, the process proceeds to step b6, and the above-mentioned step b6 is executed.
Perform the following processing.

According to the measurement by the present inventor, in the image forming apparatus 1 of the prior art which does not detect the surface potential at the developing position and does not adjust the charge removal-charging time and the charge-developing time as in the present embodiment. When the surface potential at the developing position and the surface potential at the developing position in the image forming apparatus 11 of this embodiment were compared as an electrostatic copying machine, the results shown in FIG. 8 were obtained. Line 132 in FIG. 8 is the case of the prior art, and line 133 is the case of this embodiment. As can be seen from FIG. 8, in the prior art, the potential at the developing position gradually decreases with use, whereas in the image forming apparatus 11 of this embodiment, the potential at the developing position is constant.

As a result, the image density is maintained constant in the regular developing method, and in the reversal developing method, the fog phenomenon, which is uneven image density, is prevented.
We were able to realize 1.

In this embodiment, the surface potential sensor is used as a means for detecting the fluctuation of the degree of dark decay, and the fluctuation of the surface potential at the developing position is detected. However, the invention is not limited to the surface potential sensor.
Any detector can be used as long as it can detect fluctuations in the degree of dark decay.

In this embodiment, the image forming apparatus of the present invention has been described as an electrostatic copying machine. However, the image forming apparatus of the present invention can be used as a photoconductor film for a facsimile, a printer or the like regardless of the electrostatic copying machine. Any image forming apparatus that performs image formation by performing charging, image exposure, and charge removal may be used.

[0056]

According to the present invention, after detecting the fluctuation of the degree of dark decay in the photoconductor film, the distance between the main charger and the discharging lamp, and the main charger and the developing unit are detected based on the detection result. The device spacing is adjusted to compensate for variations in the degree of dark decay in the photoreceptor film. As a result, when the degree of dark decay changes with long-term use, or when the degree of dark decay varies among image forming apparatuses due to the installation environment of the image forming apparatus, etc. Even if the degree of dark decay fluctuates due to changes from the characteristics immediately after manufacturing, the fluctuation or variation of the degree of dark decay is compensated and the surface potential at the developing position is maintained at a predetermined value. Therefore, an image can be formed with a uniform density.

[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 perspective view of the image forming apparatus 11 according to the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a change in surface potential at a developing position and charging-developing time.

FIG. 4 is a graph showing a relationship between a change in surface potential at a developing position and charge-electrification time.

FIG. 5 is a diagram showing an arrangement state in the present embodiment.

FIG. 6 is a flowchart illustrating the operation of this embodiment.

FIG. 7 is a flowchart illustrating the operation of this embodiment.

FIG. 8 is a graph illustrating the effect of this embodiment.

FIG. 9 is a system diagram of a conventional image forming apparatus 1.

[Explanation of reference numerals] 11 image forming apparatus 12 photoconductor film 13 photoconductor drum 14 main charger 16 developing device 20 discharge lamp 23 grid 26 surface potential sensor 27 comparator 28 controller 29 memory 30 drum base 31 rails 32, 33 gear 34 Motor 35 Rod

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location G03G 15/08 506 Z 8530-2H (72) Inventor Ichiro Yamazato 1-2 Takumazo, Chuo-ku, Osaka-shi No. 28 Mita Engineering Co., Ltd. (72) Inventor Takuji Terada 1-2-2 Tamatsukuri, Chuo-ku, Osaka City Mita Engineering Co., Ltd.

Claims (4)

[Claims] 1. A rotatable photoconductor drum having a photoconductor film formed on the surface thereof, and a charging device disposed near the surface of the photoconductor drum and supplying an electric charge onto the photoconductor film. And a developing unit arranged downstream of the charging unit along the rotation direction of the photosensitive drum, and arranged upstream of the charging unit along the rotation direction of the photosensitive drum. And a static eliminating means for generating light for removing the electric charge on the photoconductor film, and the degree of the dark decay on the photoconductor drum is detected based on the dark decay on the photoconductor film. The dark decay detecting means, and the distance between the charge eliminating means and the charging means or the distance between the charging means and the developing means in accordance with the variation in the degree of the dark decay detected by the dark decay detecting means. An image forming apparatus comprising: a control unit for adjusting. 2. The dark decay detecting means has a sensor for detecting the potential of the surface of the photosensitive drum in the vicinity of the developing means, and the sensor is provided in the vicinity of the developing means. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein the charge removing unit and the developing unit are fixed, and the charging unit is movable. 4. A pair of rails provided along the outer periphery of the photosensitive drum in the vicinity of the charging means, and a mechanism for supporting the charging means and moving the charging means on the rails. A motor for driving the mechanism, wherein the control means controls the motor.
The image forming apparatus according to item 1.