JPH0580680A - Image forming device - Google Patents

Abstract

PURPOSE:To satisfactorily form an image without causing a photosensitive drum an electric breakdown in the case where the characteristics of the photosensitive drum does not allow either positive or negative voltage destaticization/ exposure. CONSTITUTION:A destaticizing lamp 22 is disposed at the back of an auxiliary electrifier 21 and exposes an opposite area on the periphery of the photosensitive drum 1 opposite which the auxiliary electifier 21 is positioned. The opposite area is immediately destaticized by means of exposure even when the opposite area is electrified because of the sticking of charges from the auxiliary electrifier 21 thereto. Therefore, the surface potential of the opposite area does not become high. The polarity of the auxiliary electrifier 21 is the one capable of causing destaticization and exposure.

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 such as an electrophotographic system or an electrostatic recording system having an image carrier, and more particularly to a charge removing mechanism for the image carrier.

[0002]

2. Description of the Related Art Conventionally, various image forming apparatuses have been proposed. 13 to 17 show an example of a multicolor electrophotographic copying machine equipped with a typical developing device, a so-called rotary developing device.

A multicolor electrophotographic copying machine of this type is shown in FIG.
As shown in FIG. 3, the photosensitive drum 1 is rotatably supported and rotates in the arrow direction, and the image forming means is arranged on the outer peripheral portion thereof. This image forming means may be any means, but in this example, the primary charging device 2 that uniformly charges the photosensitive drum 1 and the color-separated optical image or an optical image corresponding to the primary charging device 2 are irradiated to the photosensitive drum 1. 1 for exposing an electrostatic latent image on the photosensitive drum 1 and a rotary developing device 4 for converting the electrostatic latent image on the photosensitive drum 1 into a visible image.
And a transfer means 5 and a cleaner 7.

The rotary developing device 4 includes, for example, four developing devices 4Y and 4M which individually store four color developers of yellow color developer, magenta color developer, cyan color developer and black color developer, respectively. , 4C, 4B and these four developing devices 4
It is composed of a substantially cylindrical tubular rotating body 4a that holds Y, 4M, 4C, and 4B and is rotatably supported.
The rotary developing device 4 conveys a desired developing device to a position facing the outer peripheral surface of the photosensitive drum 1 by the rotation of the rotating body 4a, develops the electrostatic latent image on the photosensitive drum 1, and rotates the rotating body 4a.
When a is rotated once, so-called full-color development for four colors can be performed.

A visible image, that is, a toner image on the photosensitive drum 1 is transferred onto a transfer material P which is carried and carried by the transfer means 5. In this example, the transfer means 5 comprises a transfer drum 5a which is rotatably supported and has a gripper 5c.
A transfer charger 5b, an inner charge eliminator 5d, an outer charge eliminator 5e, and a separation claw 8 are arranged around the drum 5a. As shown in FIG. 14, a transfer material carrying sheet 501 is stretched on the outer peripheral surface of the transfer drum 5a. As the transfer material carrying sheet 501, a polyethylene terephthalate or a polyvinylidene fluoride resin film is usually used.

Next, a process of forming a full-color image by the multicolor electrophotographic copying apparatus having the above-mentioned structure will be briefly described.

First, the primary charging device 2 and the exposing means 3 are driven to form a blue color-separated electrostatic latent image on the outer peripheral surface of the photosensitive drum 1, and the electrostatic latent image is developed by the developing device. A developed visible image is formed by the cyan developer stored in 4C. On the other hand, the transfer material P fed to the transfer drum 5a is gripped by the gripper 5c and comes into contact with the visible image formed on the outer peripheral surface of the photosensitive drum 1 as the transfer drum 5a rotates. Then, the visible image is transferred onto the transfer material P by the operation of the transfer charger 5b.

The toner image formation and transfer operation is repeated for each color of magenta, cyan and black, and the transfer charger 5 is operated until the transfer operation for the fourth color is completed.
The operation of b is also repeated. When the transfer of the visible images of four colors onto the transfer material P is completed, the transfer material P is neutralized by the inner static eliminator 5d and the outer static eliminator 5e, and then separated from the transfer drum 5a by the separation claw 8 to generate heat. It is fixed by the roller fixing device 6 and discharged to the outside of the machine.

Next, the movement of charges when an organic photoconductor (hereinafter referred to as OPC) is used for the photosensitive drum 1 and the photosensitive drum 1 is negatively charged by the primary charger 2 will be described.

The exposure means 3 aligns the photosensitive drum 1 with the original.
When forming an electrostatic latent image on top, the negative charges in the exposed areas are neutralized by the positive charges generated by the exposure.

On the other hand, the developing devices 4Y, 4M, 4C, 4
In B, the toner is negatively charged, whereas the bias voltage of each of the developing devices 4Y, 4M, 4C, and 4B is applied to the negative side.
Separate from 4M, 4C and 4B.

As described above, the surface of the photosensitive drum 1 has a negatively charged portion and an electrically neutralized portion, and the toner separated from the developing units 4Y, 4M, 4C and 4B is electrically charged. Adhere to the electrically neutralized area and form a visible image.

[0013]

By the way, in the above-mentioned multicolor electrophotographic copying apparatus, the positive charge in the transfer charger 5b moves to the transfer material sheet 501 on the surface of the transfer drum 5a, and further the transfer material P surface area. In some cases, the electric field was accumulated and concentrated to form a high electric field.

In this case, when the photosensitive drum 1 and the transfer drum 5a are further rotated and the transfer material P is separated from the photosensitive drum 1 to form a minute gap as shown in FIG. 16, a peeling discharge is generated. The negative charges in the air are attracted to the positive charges of the transfer material P and move onto the transfer material P, while the positive charges in the air move onto the photosensitive drum 1 having a negative charge.

According to a research experiment by the present inventors, when a polyvinylidene fluoride resin film is used as the transfer material carrying sheet 501 of the transfer drum 5a and a transfer paper (particularly high humidity) is used as the transfer material P. It has been confirmed that the above-mentioned phenomenon occurs. The volume resistivity of the polyvinylidene fluoride resin film is 10 ¹³ Ω · c.
m, transfer paper is 10 ⁹ (at high humidity) to 10 ¹² (at low humidity)
It was Ω · cm.

As a result, the surface of the photosensitive drum 1 where the transfer material P contacts during transfer (hereinafter referred to as the memory effect area) is locally charged to a high positive voltage. As is generally known, the positive voltage thus charged does not eliminate static electricity only by static elimination exposure, which causes image unevenness as described later.

The change in the surface potential of the photosensitive drum 1 is shown in FIG. That is, the memory effect area is irregularly charged to a positive potential (+100 V to +700 V) as shown in (a), but this waveform cannot be neutralized even by static elimination exposure (b) as described above. Therefore, even if the negative polarity (-700V) is used for the primary charging (C),
It is not uniformly charged (-300V to -650V). on the other hand,
When the image is exposed and a quantity of light corresponding to the density of the original is irradiated (d), the waveform is erased as shown by a dotted line according to the quantity of light. At the time of development, an amount of toner corresponding to the potential of the dotted line waveform adheres to form a visible image. Here, since the memory effect area is not uniformly charged as described above and a visible image faithful to the original is not formed, image unevenness (image defect) occurs in this area.

On the other hand, as a method of preventing this image unevenness, the surface of the photosensitive drum 1 after the transfer is charged by an auxiliary charger having the same polarity as that of the primary charger 2, and the charge is removed by the charge removing exposure after the charging. There is a method of performing primary charging or the like.

According to this method, since the entire surface of the photosensitive drum 1 is negatively charged by the auxiliary charging device, the charge can be removed by the charge removing exposure, so that a uniform potential can be obtained. However, in order to negatively charge the entire surface, the memory effect area, which is charged to the highest positive voltage, must be negatively charged. Therefore, a negative voltage having a potential higher than the positive voltage is charged. Need to let. However, since the area other than the memory effect area is still negatively charged,
Further, if a negative voltage is charged, the parts other than the memory effect region are charged to a high potential (about -1 kV), which causes a problem of dielectric breakdown.

In addition, it is necessary to secure a space on the surface of the photosensitive drum 1 for performing auxiliary charging and charge-exposure exposure. In particular, if auxiliary charging is performed before cleaning by the cleaner 7, it remains on the photosensitive drum 1. However, there is a problem in that the toner that is present is charged and cleaning failure occurs.

Therefore, according to the present invention, the auxiliary charging and the discharging exposure are performed in parallel, that is, the same portion on the photosensitive drum is subjected to the auxiliary charging and the discharging exposure at substantially the same time.
An object of the present invention is to provide an image forming apparatus which has no image unevenness, can effectively use space, and can reduce the amount of ozone generated.

[0022]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in the order of a rotatably supported image carrier, a primary charger, an exposing unit, and a developing unit. In an image forming apparatus including an apparatus and a transfer unit,
A static elimination light source that is provided between the transfer unit and the primary charger to eliminate static electricity in a facing opposing area of the outer peripheral surface of the image carrier, and a facing area exposed by the static elimination light source. And a charger that is charged with the same polarity as the primary charger.

In this case, the charging device may be provided with an operating device for turning on / off the charging device in synchronization with the driving of the image carrier.

[0024]

According to the above-mentioned structure, the charger removes the charge on the facing area exposed by the charge eliminating light source. Therefore, even if the charge from the charger is attached to the facing area, the charge is immediately generated. The exposure eliminates the charge, and therefore the surface potential of the facing region does not increase.

When the characteristic of the image bearing member is such that either one of the positive voltage and the negative voltage cannot be used for the static elimination exposure, the opposite area is obtained by charging the image bearing member with a polarity permitting the static elimination exposure. Is discharged.

At this time, since the photosensitive drum is rotating, the entire outer peripheral surface of the photosensitive drum is discharged.

Further, the actuating device turns on / off the operation of the charger in synchronization with the driving of the image carrier.
The charger may be operated only when the areas where static electricity cannot be removed only by the static elimination light source face each other.

[0028]

EXAMPLES Examples of the present invention will be described below with reference to FIGS. The same parts as those shown in FIG. 13 are designated by the same reference numerals, and the description thereof will be omitted.

1 and 2 show the structure in the vicinity of the image forming portion of the image forming apparatus according to the present invention.

The photosensitive drum 1 is supported by a driving means (not shown) so as to rotate counterclockwise, and the auxiliary charger 21 is provided between the primary charger 2 and the cleaner 7 so as to face the photosensitive drum 1. Has been.

The auxiliary charger 21 has a high negative voltage (1
Corona wire 21a applied with the same polarity as the next charger 2)
This corona wire 21a has a photosensitive drum 1
Are arranged so as to keep a constant distance from the surface of the photosensitive drum 1 along the axial direction of. A shield case 21b is arranged around the corona wire 21a, and the shield case 21b is opened on the side (inside) facing the photosensitive drum 1 and the opposite side (outside), respectively.

On the other hand, a charge eliminating lamp 22a as a charge eliminating light source is arranged outside the auxiliary charger 21, and extends along the axial direction of the photosensitive drum 1 like the corona wire 21a. The light emitted from the static elimination lamp 22a effectively irradiates the surface of the photosensitive drum 1 through the outer opening and the inner opening of the shield case 21b. Therefore, the auxiliary charger 21 and the discharge lamp 22a are
The same location on the photoconductor 1 is charged and exposed almost at the same time.

In this embodiment, the diameter of the photosensitive drum 1 is set to 80 mm and the diameter of the transfer drum 5 is set to 160 mm (twice the diameter of the photosensitive drum). In addition, the photosensitive drum 1
Is rotated in the direction of the arrow at 160 mm / sec, and its surface is charged to -300 to -900 V by the primary charger 2. Further, a laser beam exposure device was used as the exposure means 3. Each developing device of the rotary developing device 4 has a toner of each color having a negative charge, and a developing sleeve that carries the toner and conveys the toner to a developing area in the vicinity of the photosensitive drum 1, and is applied to the sleeve. A developing electric field formed by a voltage (hereinafter, referred to as developing bias) and a potential of the photosensitive drum 1 causes the toner to adhere to the electrostatic latent image formed on the photosensitive drum 1 by reversal development and is visualized.

As will be understood with reference to FIG. 1, the transfer means 5 is a transfer drum 5 having a structure similar to that shown in FIG.
In the present embodiment, the transfer material carrying sheet 501 is
Thickness is 100 μm to 175 μm, volume resistivity is 10 ¹³ Ω
A cm polyvinylidene fluoride resin film was used. Further, a corona charger is used as the transfer charger 5b, and a voltage of +6 kV to +9 kV is applied in this embodiment,
The transfer current was set to +100 μA to +500 μA. The visible image on the photosensitive drum 1, that is, the toner image, is transferred to the transfer material P carried and carried by the transfer drum 5a.

Further, in this embodiment, as the primary charger 2 and the auxiliary charger 21, scorotron type chargers as shown in FIG. 4 (b) are used, and a high voltage power source 2 with a built-in controller is used. -2, the discharge amount of the corona wire 2-1 that is discharged by the high voltage applied is controlled by applying a predetermined control voltage from the grid bias power supply 2-4 to the grid line 2-3, and the photosensitive drum 1 Is charged to a desired electric potential.

The static elimination lamp 22 uses an LED lamp array 65 as shown in FIG. 3 (a), a fuse lamp array 66 as shown in FIG. 3 (b), and the like. For example,
The LED lamp array 65 is an array of 64 lamps having a peak wavelength of 695 nm that are linearly arranged.

The operation of the above embodiment will be described with reference to FIG. FIG. 5 shows changes in the surface potential of the photosensitive drum 1 in which a memory effect area is generated when the present invention is applied.

Immediately after the transfer, the memory effect area (a) is irregularly charged (+100 V to +700 V) to a positive potential as shown in the figure. When this portion is subjected to auxiliary charging with negative polarity, this waveform is not deformed and only rises as shown by the dotted line (portion B) in FIG. However, when the exposure is carried out at the same time as the auxiliary charging to remove the electric charge, the electric potential of the memory effect region becomes zero due to the auxiliary charging, but the charging to the negative voltage is hindered by the discharging exposure.

That is, when the auxiliary charging is performed, the positively charged portion is charged to the negative “side”, but since the static elimination lamp 22 has no effect as long as it is the positive potential, the potential waveform (a) in FIG. ) Rises without changing the waveform. However, since the static elimination lamp 22 is effective against a negative voltage, when the potential waveform (a) rises to locally charge the negative voltage, the negative charges are immediately neutralized by the static elimination lamp. As a result, the potential of the entire surface of the photosensitive drum 1 is maintained at almost zero.

Therefore, when a negative voltage is charged by the primary charger 2 after that (c), the potential on the entire surface of the photosensitive drum 1 becomes uniform (for example, -700 V). When the image is exposed and a quantity of light is emitted according to the density of the original, (d) static electricity is removed according to the quantity of light as shown by the dotted line, and toner adheres to form a visible image faithful to the original. It

Actually, the length of the A3 size transfer material in the traveling direction is 420 mm, which is approximately equivalent to the length of the electrostatic latent image formed on the photosensitive drum 1. However, the diameter of the photosensitive drum is 80 mm and the circumference is 251.
Since it is 3 mm, 1.67 rounds of the photosensitive drum 1 are required to form an electrostatic latent image corresponding to the A3 size. That is, when the auxiliary charging as described above is not performed, the memory effect generated on the photosensitive drum 1 when the visible image formed on the first rotation of the photosensitive drum 1 is transferred to the transfer material P is the photosensitive drum 1. 6 affects the formation of the electrostatic latent image formed in the second round, that is, the electrostatic latent image corresponding to the latter half of A3 size as shown in FIG. 6, and causes image unevenness in that portion. .. In this embodiment, as shown in FIG.
By effectively operating the auxiliary charging device 21 in the memory effect area corresponding to the latter half of the A3 size as shown in (4), the adverse effect in the conventional example as described above is suppressed, and the image unevenness due to the memory effect is suppressed. Can be prevented.

According to this, a sound visible image with no image unevenness can be formed, and a normal region not subjected to the memory effect is not charged to a remarkably high potential (minus), so that dielectric breakdown may occur. Absent. Furthermore, since the charge eliminating lamp 22 is arranged outside the auxiliary charger 21, that is, the space on the photosensitive drum 1 for arranging the auxiliary charger 21 and the charge eliminating lamp 22 is only the amount of the auxiliary charger 21. Therefore, the degree of freedom in designing the device is increased. In addition, the auxiliary charger 21 is attached to the cleaner 7
1 does not need to be arranged on the front side (lower side in FIG. 1), and therefore defective cleaning due to electrification of residual toner can be avoided.

In the above embodiment, the auxiliary charger 2
The static elimination lamp 22 is provided by providing an opening outside the shield case 21b of No. 1, but if the portion charged by the auxiliary charger 21 is exposed by the static elimination lamp 22, the positions of both may be slightly shifted. Good.

Since the memory effect area is generated only in a part of the photosensitive drum 1 as described above, the auxiliary charger 21 may be operated only in that area. That is, the role of the auxiliary charger 21 is to charge the area charged with the positive voltage to the negative “side”, and is therefore unnecessary for areas other than the area.

That is, in the multicolor electrophotographic copying apparatus having the above-described structure, in this embodiment, a section where an electrostatic latent image is not formed on the photosensitive drum 1 (hereinafter referred to as an electrostatic latent image non-forming section), for example, a transfer is performed. A section in which a preparatory step for image formation such as gripping the material P on the transfer drum 5 is performed, and after the image exposure of the first color is performed to form an electrostatic latent image, the image exposure of the second color is performed. During the period until the electrostatic latent image is formed, the auxiliary charger 21 is not operated, and the discharge lamp 2
It is controlled so that only the static elimination exposure by 2 is performed.

FIG. 7 shows an operation sequence corresponding to the position of the photosensitive drum of the multicolor electrophotographic copying apparatus of this embodiment. In the present embodiment, the auxiliary charger 2 is provided with a high-voltage power supply 2-2 as an operating device that turns the charger 2 ON / OFF in synchronization with the rotation of the photosensitive drum 1, and a region other than the memory effect region. The auxiliary charger 21 is not operated for
Only the static elimination exposure by the static elimination lamp 22 is performed.

As a result, in addition to the above-described effects, the operation time of the auxiliary charger 21 is shortened, so that the amount of discharge products generated by corona discharge can be reduced. For example, FIG. 8 shows a temporal change in the O ₃ concentration when the electrophotographic copying apparatus of this embodiment is continuously operated, and shows the case where ON / OFF control of the auxiliary charger 21 is performed. It is possible to reduce the O ₃ concentration.

Further, since the amount of current flowing through the photosensitive drum 1 is reduced, it is possible to suppress the deterioration of the photosensitive drum 1 and the deterioration of the image quality. Specifically, about 8000 times of image formation is the limit. On the other hand, the life of the photosensitive drum 1 can be extended until the image can be formed about 12,000 times.

Next, another embodiment of the present invention will be described with reference to FIG. The image forming apparatus of this embodiment is applied to a multicolor electrophotographic copying machine having four image forming units a, b, c and d.

In the present image forming apparatus, each of the image forming units a to d includes a photosensitive drum 11a, 11b, 11c, 1.
1d, around which the primary chargers 12a, 12b, 1
2c, 12d, exposure means 13a, 13b, 13c, 13
d, developing devices 14a, 14b, 14c, 14d, transfer chargers 15a, 15b, 15c, 15d, cleaner 16a,
16b, 16c, 16d are arranged, and the photosensitive drums 11a-1a are arranged in such a manner as to penetrate the image forming units ad.
An endless transfer material carrying belt 17 is arranged below 1d as a conveying means, and the transfer material P fed by the paper feed roller 18 is arranged at the transfer chargers 15a to 15d. The photosensitive drums 11a to 11d are configured so as to be in contact with the photosensitive drums 11a to 11d.

Further, as shown in FIG. 9 also in this embodiment, in applying the present invention, the photosensitive drum 11a
The auxiliary charging devices 23a, 23b, 23c, 23d and the discharge lamps 24a, 24b, 24c, 24d for simultaneously exposing the entire surface of the photosensitive drums 11a to 11d for charging the image forming units a to d. It is provided corresponding to the same location.

The image forming process by the multi-color electrophotographic copying apparatus having the above-mentioned structure is basically the same as that of the above-mentioned embodiment, so that it will not be described in detail. However, in this embodiment, the photosensitive drums 11a to 11d are respectively provided on the surface. After the residual toner above is removed by the cleaners 16a to 16d, the auxiliary charger 23a
23d to be charged with the same polarity as that of the electrostatic latent image, that is, negative polarity, and at the same time, uniformly exposed by the discharge lamps 24a to 24d, and discharged to have a surface potential of about 0V. Then, by the operation of the primary chargers 12a to 12d and the laser beam exposure devices 13a to 13d, which are exposure means,
A color-separated electrostatic latent image corresponding to an image pattern is formed on the photosensitive drums 11a to 11d, and the developing devices 14a to 14d.
By the operation of 14d, the electrostatic latent image is colored in yellow,
After being developed with magenta, cyan, and black toners to form a visible image, the visible image is transferred to the transfer charger 1.
By the operation of 5a to 15d, the images are sequentially transferred onto the transfer material P carried on the transfer material carrying belt 17, and a full color image is formed on the transfer material P.

Also in this embodiment, as in the case of the above-described embodiment, the static charge is formed in advance by the operation of the auxiliary chargers 23a to 23d shown in FIG. 9 before the memory effect area is subjected to the primary charging. It is charged so as to have the same polarity as the latent image, that is, the negative polarity. The surface of the photosensitive drum 1 is neutralized by the operation of the static elimination lamps 24a to 24d to a substantially uniform potential before the primary charging is performed, and at the same time, a normal area not affected by the memory effect is generated by the auxiliary charger. It is not charged to a remarkably high potential. Therefore, after that, primary charging,
The developing process is normally performed, and the toner image is formed in the memory effect area and transferred to the transfer material P as in the above embodiment, so that the image is not disturbed.

FIG. 10 shows an operation sequence corresponding to the position of the photosensitive drum of the multicolor electrophotographic copying apparatus of this embodiment. As will be understood with reference to FIG. 10, also in the present embodiment, the auxiliary chargers 23a to 23d in the section other than the area where the memory effect area on the photosensitive drums 11a to 11d is in charge of forming the electrostatic latent image. Is not performed, and only the static elimination exposure for the static elimination lamps 24a to 24d is performed. Therefore, also in this example, it is possible to reduce the amount of electric current flowing through the photosensitive drums 11a to 11d in each generation of the discharge products while preventing the image from being disturbed in the memory effect region. .. As a result, the photosensitive drums 11a to 1a by repeating the image forming process are performed.
It was possible to suppress the deterioration of 1d and the resulting deterioration of the image forming quality.

FIG. 11 is a schematic configuration diagram showing still another embodiment of the image forming apparatus of the present invention. The image forming apparatus of this embodiment is an image forming apparatus having no transfer device, for example, a black and white electrophotographic digital laser beam printer.

The image forming apparatus has a photosensitive drum 31, around which a primary charger 32, a laser beam scanner 33 as an exposing means, a developing device 34, a transfer charger 35, and a cleaner 37 are arranged.

Further, as shown in FIG. 11 also in this embodiment, in applying the present invention, the photosensitive drum 31
Auxiliary charger 3 for charging the entire surface at the same time as charging
8 and a discharge lamp 39 are provided at the same position on the surface of the photosensitive drum 31.

The image forming process by the multi-color electrophotographic copying apparatus having the above-mentioned structure is basically the same as that of the above-mentioned embodiment, so that it will not be described in detail. The residual toner is removed by the cleaner 37 and then charged to the same polarity as the electrostatic latent image formed by the auxiliary charging 38, that is, to the negative polarity, and at the same time, the charge eliminating lamp 3
It is uniformly exposed by 9 and is discharged to have a surface potential of about 0V. Thereafter, the toner image formed by the reversal development on the photosensitive drum 31 by the operation of the primary charger 32, the laser beam scanner 33, and the developing device 34 is transferred to the paper feeding roller 3.
6 is transferred onto the transfer material P by operating the transfer charger 35 at the transfer portion where the transfer material P fed and conveyed by 6 and the like and the photosensitive drum 31 come into contact with each other. Further, FIG. 12 shows an operation sequence corresponding to the position of the photosensitive drum of the laser beam printer of this embodiment. As will be understood with reference to FIG. 12, also in the present embodiment, the operation of the auxiliary charger 38 is performed in a section other than the area where the memory effect area on the photosensitive drum 31 forms an electrostatic latent image. Instead, it is controlled so that only the static elimination exposure by the static elimination lamp 9 is performed. 12
Shows a continuous print sequence as an example.

By carrying out the image forming process as described above, also in the present embodiment, the deterioration of the photosensitive drum 31 and the deterioration of the image quality due to the deterioration of the photosensitive drum 31 due to the repeated image forming process are suppressed as in the conventional case. It was possible to obtain a high-quality image with no image distortion corresponding to the memory effect area.

The auxiliary charger 21 may be of the corotron type shown in FIG. 4 (a) or of the scorotron type shown in FIG. 4 (b).

Further, the surface potential of the photosensitive drum after the primary charging and the surface potential after the laser beam exposure in each of the above embodiments,
The developing bias voltage and the like are not limited and can take various values according to changes in the surrounding environment. Of course, the exposure is not limited to the laser beam exposure.
Further, the present invention is equally applicable to various copying machines such as electrophotographic systems and electrostatic recording systems other than multicolor electrophotographic copying machines, and image forming apparatuses such as printers.

[0062]

As described above, since the charger removes the charge on the facing area exposed by the charge eliminating light source, the image bearing member has a polarity which cannot be eliminated only by the exposure due to a memory effect or the like. Even if charged, the charge can be removed, and the image carrier does not suffer dielectric breakdown. Therefore, there is no image unevenness and the life of the image carrier is extended.

Further, the operating device may operate the charger only when facing the area where static elimination cannot be performed only by the static elimination light source. In this case, static elimination is of course possible. The amount of ozone generated can also be reduced by stopping the required corona discharge.

[Brief description of drawings]

FIG. 1 is an explanatory view of the vicinity of an image forming section showing an embodiment of a multicolor electrophotographic copying apparatus to which the present invention is applied.

FIG. 2 is a detailed view showing the structure around the photosensitive drum of FIG.

FIG. 3 is an external view of the static elimination lamp of FIG.

FIG. 4 is an explanatory view of the auxiliary charger of FIG.

FIG. 5 is an explanatory diagram showing a change in potential distribution in a memory effect region.

FIG. 6 is a diagram showing a portion corresponding to a memory effect region in an A3 size transfer material.

FIG. 7 is a sequence diagram when ON / OFF control of an auxiliary charger is performed.

FIG. 8 is a diagram showing the influence of ON / OFF control of the auxiliary charger on the O ₃ concentration.

FIG. 9 is an overall structural view showing another embodiment of the present invention.

FIG. 10 is a sequence diagram for controlling ON / OFF of the auxiliary charger.

FIG. 11 is an overall structural view showing another embodiment of the present invention.

FIG. 12 is a sequence diagram when the auxiliary charger is ON / OFF controlled.

FIG. 13 is a structural explanatory view showing a conventional example.

FIG. 14 is a structural explanatory view of a transfer unit 5.

FIG. 15 is an explanatory diagram showing transfer of charges from a transfer charger to a transfer material.

FIG. 16 is an explanatory diagram showing the movement of charges due to peeling discharge between a transfer material and a photosensitive drum.

FIG. 17 is an explanatory diagram showing changes in the potential distribution in the memory effect region in the case of the conventional example.

[Explanation of symbols]

1 Image Carrier (Photosensitive Drum) 2 Primary Charger 3 Exposure Means 4 Developing Device 5 Transfer Means 7 Cleaner 8 Separation Claws 11a, 11b, 11c, 11d Photosensitive Drums 12a, 12b, 12c, 12d Primary Chargers 13a, 13b , 13c, 13d exposure means 14a, 14b, 14c, 14d developing device 15a, 15b, 15c, 15d transfer means (transfer charger) 16a, 16b, 16c, 16d cleaner 17 transfer means (transfer material carrying belt) 21 auxiliary charger 22 Charge Eliminating Light Source (Electrifying Elimination Lamp) 23a, 23b, 23c, 23d Auxiliary Charger 24a, 24b, 24c, 24d Electrifying Emission Light Source (Eliminating Lamp) 31 Photosensitive Drum 32 Primary Charger 33 Exposure Means 34 Developing Device 35 Transfer Means ( Transfer charger) 37 Cleaner 38 Auxiliary charger 39 Light source for static elimination (static elimination lamp)

Claims (2)

[Claims] 1. An image forming apparatus comprising a primary charger, an exposure unit, a developing unit, and a transfer unit in order around a rotatably supported image carrier, wherein the transfer unit and the transfer unit are provided. A static elimination light source that is provided between the primary charging device and exposes a facing opposing area on the outer peripheral surface of the image carrier, and a facing area exposed by the static elimination light source, An image forming apparatus comprising: a charging device that is charged to the same polarity as the charging device. 2. The image forming apparatus according to claim 1, wherein the charger includes an operating device that turns the charger on and off in synchronization with the driving of the image carrier.